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B GIO DC V O TO VIN KHOA HC V CNG NGH
VIT NAM
VIN K THUT NHIT I
**************************
L TH M HNH
CH TO V NGHIN CU TNH CHT VT LIU
NANOCOMPOZIT TRN C S POLYETYLEN V
NANO CLAY BIN TNH SILAN
LUN N TIN S HO HC
H NI-2012
2
i
B GIO DC V O TO VIN KHOA HC V CNG NGH
VIT NAM
VIN K THUT NHIT I
**************************
L TH M HNH
CH TO V NGHIN CU TNH CHT VT LIU
NANOCOMPOZIT TRN C S POLYETYLEN V
NANO CLAY BIN TNH SILAN
LUN N TIN S HO HC
Chuyn ngnh: Ho L thuyt v ho l
M s: 62.44.31.01
Ngi hng dn khoa hc
1.TS o Th Minh
2.GS. TS Ng Duy Cng
H NI-2012
3
LI CM N!
Vi lng bit n su sc, em xin gi li cm n n GS.TS. Ng Duy
Cng v TS. o Th Minh giao ti v tn tnh hng dn em
trong sut thi gian thc hin lun n.
Ti xin trn trng cm n Ban Lnh o v T t vn o to sau
i hc Vin K thut nhit i t vn, khch l v to iu kin thun
li trong thi gian ti thc hin lun n.
Ti xin gi li cm n n tp th cn b phng Vi phn tch, phng
Ha l v Vt liu phi kim loi Vin K thut nhit i gip v to
iu kin thun li ti hon thnh ni dung lun n.
Ti xin cm n cc ng nghip trong v ngoi Vin Khoa hc v
Cng ngh Vit Nam nhit tnh gip thc hin cc php o v phn
tch mu th nghim trong ni dung lun n.
Ti cng xin gi li cm n chn thnh n gia nh v bn b
ng vin, khuyn khch ti trong qu trnh lm lun n.
Tc gi lun n
L Th M Hnh
4
LI CAM OAN
Ti xin cam oan nhng ni dung trong lun n ny do ti thc hin
di s hng dn ca ngi hng dn khoa hc. Mt s nhim v
nghin cu l thnh qu tp th v c cc ng s cho php s dng.
Cc s liu, kt qu trnh by trong lun n l trung thc v cha c
cng b trong lun n khc.
Tc gi lun n
L Th M Hnh
5
BNG CH VIT TT
APS - Aminopropyltrimetoxysilan
BP - benzoyl peoxit
CEC - dung lng trao i cation
DCP - dicumyl peoxit
d001 - khong cch c bn ca khong st
E- modun n hi
Et in p nh thng
HDPE - PE t trng cao
IR ph hng ngoi
MDPE - PE t trng trung bnh
MMT- montmorillonit
LDPE - PE t trng thp
LLDPE - PE t trng thp mch thng
PE-g-AM - PE ghp anhydrit maleic
PE- polyetylen
PEX - polyetylen khu mch
PEX-b- PE khu mch bng tia bc x beta
SEM - knh hin vi in t qut
TGA - Phn tch nhit trng lng
tg tang gc tn hao in mi
TEM - Hin vi in t truyn qua
UHMWPE - PE c khi lng phn t rt cao
6
XRD - ph nhiu x tia X
VLDPE - PE t trng rt thp
VTMS- vinyltrimetoxysilan
dn di khi t
e hng s in mi
s in tr sut mt
v in tr sut khi
bn ko t
7
MC LC
Trang
LI CM N
LI CAM OAN
BNG CC CH VIT TT
DANH MC BNG, BIU TRONG LUN Nvi
DANH MC TH, HNH V TRONG LUN Nviii
M U ..1
CHNG 1. TNG QUAN...........4
1.1. Khong st t nhin v khong st hu c.....4
1.1.1. Khong st t nhin, cu trc v thnh phn.......................................................4
1.1.2. Bin tnh khong st............................................................................................5
1.1.3. ng dng ca khong st hu c........8
1.2. Polyetylen (PE)......................................................................................................9
1.2.1. Nhu cu v ng dng polyetylen trn th gii v Vit Nam...............................9
1.2.2. ng dng ca PE...............................................................................................12
1.2.3. Tnh cht ca PE ...12
1.2.3.1 Cu trc phn t v hnh thi hc....12
1.2.3.2. Tnh cht ca PE.14
1.2.3.3. ho tan .14
1.2.4. Cc phng php khu mch PE ..15
1.2.4.1. Khu mch bng peoxit..15
1.2.4.2. Khu mch bng tia bc x beta (PEX-b)..........18
1.2.4.3. Khu mch bng cc hp cht silan....18
1.2.4.4. Khu mch PE bng bc x t ngoi..21
i
8
ii
1.3. Hp cht lin kt c silic....24
1.3.1. Lch s pht trin...24
1.3.2. Cu to ca cc cht lin kt c silic.25
1.3.3. C ch hot ng ca cht lin kt c silic trong vt liu compozit.....25
1.3.4. Lnh vc ng dng ca cc cht lin kt c silic .............27
1.4. Vt liu nanocompozit polyme/clay......28
1.4.1. Phn loi .......28
1.4.2. Cc phng php ch to nanocompozit polyme/clay .........29
1.4.2.1. Phng php chn lp....29
1.4.2.2. Phng php trng hp ti ch (in- situ polymerisation)32
1.4.2.3. Phng php trn hp trng thi nng chy........33
1.4.3. Cc phng php kho st cu trc vt liu nanocompozit polyme/clay......34
1.4.3.1. Phng php ph nhiu x tia X (XRD)....34
1.4.3.2. Phng php hin vi in t truyn qua (TEM).35
1.4.3.3. Phng php ph hng ngoi (IR).........36
1.4.4. Mt s tnh cht ca vt liu polyme/ clay nanocompozit36
1.4.4.1. Tnh cht c hc.36
1.4.4.2. bn nhit v tnh cht chng chy.38
1.4.4.3. Tnh cht che chn..41
1.5. Tnh hnh nghin cu vt liu nanocompozit PE/clay.....42
1.5.1. Nghin cu ch to v kho st tnh cht chng vi khun ca
vt liu nanocompozit t PE/nano bc42
1.5.2. Ch to v kho st tnh cht vt liu PE/clay nanocompozit.......43
CHNG 2. THC NGHIM.......51
2.1 Nguyn liu v ha cht............51
2.2. Bin tnh hu c clay bng APS v VTMS......51
9
iii
2.3. Ch to vt liu compozit PE/clay.......................................................................51
2.4. Ch to vt liu nanocompozit PE/clay hu c bng
phng php trn nng chy.......................................................................................51
2.4.1. Ch to vt liu nanocompozit PE/clay-APS khi khng v
c mt cht tng hp PE-g-AM.................................................................................51
2.4.2. Ch to vt liu nanocompozit PE/clay-VTMS khi khng
v c mt cht khi mo DCP. ...................................................................................52
2.5. Cc phng php nghin cu ..............................................................................52
2.5.1. Ph hng ngoi IR.............................................................................................52
2.5.2. Phn tch nhiu x tia X-XRD...........................................................................52
2.5.3. Phn tch nhit trng lng- TGA.....................................................................53
2.5.4. Kho st cu trc hnh thi hc ca vt liu bng nh knh hin
vi in t qut (SEM)..................................................................................................53
2.5.5. nh knh hin t truyn qua (TEM)..................................................................53
2.5.6.Kho st tnh cht c hc....................................................................................53
2.5.7. Kho st bn oxy ha nhit v bn oxy ha quang..................................54
2.5.7.1. Kho st bn oxy ha nhit........................................................................54
2.5.7.2. Kho st bn oxy ha quang......................................................................54
2.5.8. Kho st kh nng chng chy ca vt liu.......................................................54
2.5.9. Kho st kh nng chng thm kh (hi nc, axeton).....................................55
2.5.10. Kho st tnh cht in ca vt liu.................................................................55
Chng 3: KT QU V THO LUN................................................................56
3.1. Ch to v kho st tnh cht clay hu c ...........56
3.1.1. Ph hng ngoi IR.............................................................................................56
3.1.2. Ph nhiu x tia X-XRD....................................................................................58
3.1.3. Ph phn tch nhit trng lng- TGA..............................................................60
10
iv
3.1.4. Kho st cu trc ca clay trc v sau bin tnh..62
Mt s kt qu mc 3.1........63
3.2. Kho st tnh cht vt liu compozit trn c s PE/clay.64
3.2.1. Tnh cht c hc................................................................................................64
3.2.2. Tnh cht nhit TGA..........................................................................................65
3.2.3. Ph nhiu x tia X..............................................................................................66
Mt s kt qu mc 3.2........67
3.3. Kho st nh hng ca iu kin ch to v thnh phn
vt liu n tnh cht c hc vt liu nanocompozit...............................................67
3.3.1. nh hng ca nhit ....................................................................................67
3.3.2. nh hng ca thi gian trn....68
3.3.3. nh hng ca tc trc quay....70
3.3.4. Kho st nh hng ca hm lng clay-APS
v cht tng hp PE-g-AM n tnh cht vt liu ....71
3.3.4.1. Tnh cht c l vt liu vi cc hm lng clay-APS khc nhau.......72
3.3.4.2. nh hng ca hm lng PE-g-AM n tnh cht c hc vt liu .........73
3.3.5. Kho st nh hng ca hm lng clay-VTMS
v cht khi mo DCP n tnh cht vt liu.....75
3.3.5.1.Tnh cht c hc vt liu vi cc hm lng clay-VTMS khc nhau.75
3.3.5.2. nh hng ca hm lng cht khi mo DCP n tnh cht vt liu..77
Mt s kt qu mc 3.3....78
3.4. Kho st ph hng ngoi IR v phn tch nhit TGA.....79
3.4.1. Kho st ph hng ngoi- IR.....79
3.4.2. Phn tch nhit TGA..80
Mt s kt qu mc 3.4....86
3.5. Kho st cu trc vt liu nanocompozit trn c s
PE/clay-APS v PE/clay-VTMS.....,....86
11
3.5.1. Ph nhiu x tia X-XRD....86
3.5.2. nh knh hin vi in t qut pht x trng- FESEM.88
3.5.2.1. Vt liu nanocompozit t PE/clay APS v
PE/clayAPS/PE-g-AM.......88
3.5.2.2. Vt liu nanocompozit t PE/ clay VTMS v
PE/clay-VTMS/DCP........89
3.5.3. nh knh hin vi in t truyn qua- TEM...90
Mt s kt qu mc 3.5....92
3.6. Kho st mt s tnh cht tiu biu cho vt liu nanocompozit
trn c s PE/clay-APS v PE/clay-VTMS mc ch ng dng
lm v bc cp in....92
3.6.1. Tnh cht in92
3.6.2. bn oxy ha nhit v oxy ha quang....93
3.6.2.1. bn oxy ha nhit......93
3.6.2.2. bn oxy ha quang....95
3.6.3. Tnh cht chng chy.....96
3.6.4. Tnh cht chng thm kh..98
3.6.4.1. Tnh chng thm hi nc..99
3.6.4.2. Tnh chng thm hi axeton.......99
Mt s kt qu mc 3.6..100
KT LUN...101
TI LIU THAM KHO...102
v
12
vi
DANH MC CC BNG, BIU TRONG LUN N
Bng 1.1. S ph thuc ho tan ca PE vo nhit trong xilen....15
Bng 1.2. S ph thuc ho tan ca PE vo trng lng phn t
trong xilen 70 0C.........15
Bng 1.3. Mt s loi peoxit thng dng v thi gian
bn phn hu ca chng..17
Bng 1.4. Tnh cht ca HDPE khu mch bng vinyltrimetoxysilan (VTMS)...21
Bng 1.5. Tnh cht c l ca PE v vt liu nanocompozit PE/clay....45
Bng 1.6. Cc thng s phn tch nhit c trng ca nanocompozit
HDPE/clay vi cc hm lng clay khc nhau..48
Bng 3.1.c trng ph IR ca clay v clay hu c.....59
Bng 3.2.Tnh cht c hc ca vt liu compozit PE/clay....64
Bng 3.3. c trng TGA ca PE v PE/3%clay......66
Bng 3.4. Tnh cht c hc vt liu nanocompozit PE/1%clay-APS vi
nhit trn khc nhau...68
Bng 3.5. Tnh cht c hc vt liu nanocompozit PE/1%clay-APS
vi thi gian trn khc nhau.....69
Bng 3.6. Tnh cht c hc vt liu nanocompozit PE/1%clay-APS
vi tc trn khc nhau...71
Bng 3.7. Tnh cht c hc vt liu nanocompozit vi hm lng
clay-APS khc nhau................72
Bng 3.8. nh hng ca hm lng PE-g-AM n tnh cht c hc vt liu....74
Bng 3.9. Tnh cht c hc vt liu nanocompozit vi hm lng
clay-VTMS khc nhau.........75
Bng 3.10. nh hng ca hm lng cht khi mo DCP n
13
vii
tnh cht c hc ca vt liu...77
Bng 3.11. c trng phn tch nhit TGA ca PE v cc mu
vt liu PE/3%clay-APS vi cc hm lng PE-g-AM khc nhau...83
Bng 3.12. c trng phn tch nhit TGA ca PE v cc mu
vt liu PE/2%clay-VTMS vi cc hm lng DCP khc nhau85
Bng 3.13. Tnh cht in ca vt liu nanocompozit PE/clay-APS93
Bng 3.14. Tnh cht in ca vt liu nanocompozit
PE/clay-VTMS....93
Bng 3.15. H s bn oxy ha nhit ca vt liu sau th nghim
1000C trong 72 gi.94
Bng 3.16. H s bn oxy ha nhit ca vt liu sau th nghim
1360C trong 72 gi........95
Bng 3.17. H s bn oxy ha quang ca vt liu sau th nghim..96
Bng 3.18. Tc chy ca PE v vt liu nanocompozit
PE/clay-APS...........97
Bng 3.19. Tc chy ca PE v vt liu nanocompozit
PE/clay-VTMS..........98
Bng 3.20. Tnh chng thm hi nc ca vt liu.......99
Bng 3.21. Tnh chng thm hi axeton ca vt liu...100
14
viii viii
DANH MC CC HNH V, TH TRONG LUN N
Hnh 1.1. Cu trc ca bentonit ....5
Hnh 1.2. Cu trc ca cc dng clay hu c khc nhau ....7
Hnh 1.3. Sn lng nha trn th gii..9
Hnh 1.4. Phn loi ht nha.....10
Hnh 1.5. Sn lng ngnh nha Vit Nam trong cc nm 2000-2010....11
Hnh 1.6. Cu trc ca 3 loi PE ....13
Hnh 1.7. Cng thc ca cc cht lin kt c silic...25
Hnh 1.8. S to thnh mng phim polysiloxan trn b mt thy tinh.........26
Hnh 1.9. S ca pha chuyn tip gia thu tinh v vt liu nn
nh hp cht lin kt c silic.....................................................................27
Hnh 1.10. Cc dng polyme/clay nanocompozit...28
Hnh 1.11. Qu trnh to thnh vt liu nanocompozit polyme/clay bng
phng php chn lp trong dung dch30
Hnh 1.12. Qu trnh chn lp trng thi nng chy.31
Hnh 1.13 . S hnh thnh nanocompozit polyme/clay t clay
hu c v nn nha PE bin tnh..32
Hnh 1.14. S tng hp nanocompozit Nylon 6/ clay t caprolactam.........32
Hnh 1.15. Ph XRD ca cc dng vt liu polyme/clay..34
Hnh 1.16. nh TEM ca vt liu nanocompozit PS/clay........35
Hnh 1.17. S ph thuc ca E-modun nhit 120oC
vo s thay i hm lng clay.....36
Hnh 1.18. dn khi t ca vt liu nanocompozit t epoxy
vi cc cht hu c ho khc nhau......37
15
ix
Hnh 1.19. Pic HRR ca nylon-6 v nylon-6 nanocompozit tch lp....39
Hnh 1.20. Kh nng thm kh CO2 ca PI nanocompozit...40
Hnh 1.21. nh TEM vt liu nanocompozit PE/nanoAg vi cc
hm lng nano bc khc nhau....42
Hnh 1.22. nh TEM vt liu nanocompozit trn c s LLDPE/CL15..43
Hnh 1.23. Ph hng ngoi ca vt liu nanocompozit v cc mu so snh
trong qu trnh th nghim oxy ha quang.....43
Hnh 1.24. nh TEM ca vt liu nanocompozit PE-g-VTMS/clay hu c .....45
Hnh 1.25. TGA ca PE (A), PE-g-VTMS (B) v PE-g-VTMS/clay (C).46
Hnh 1.26. nh SEM ca khong st bin tnh C-OMMT........48
Hnh 1.27. nh TEM vt liu nanocompozit HDPE/P-MMT...48
Hnh 1.28. nh TEM ca vt liu nanocompozit HDPE/clay, trc (A) v
sau khi x l vi sng siu m (B) ...49
Hnh 1.29. ng i ca qu trnh khuch tn kh trong vt liu......50
Hnh 3.1. Ph hng ngoi ca clay.............................................................................56
Hnh 3.2. Ph hng ngoi ca clay bin tnh bng APS ............................................57
Hnh 3.3. Ph hng ngoi ca clay bin tnh bng VTMS..........................................57
Hnh 3.4. Ph XRD ca clay (1) v clay- APS(2)........................................................59
Hnh 3.5. Ph XRD ca clay (1) v clay- VTMS(2).....................................................59
Hnh 3.6. Phn tch nhit TGA ca clay ban u...60
Hnh 3.7. Phn tch nhit TGA ca clay v clay bin tnh APS .........61
Hnh 3.8. Phn tch nhit TGA ca clay v clay bin tnh VTMS......62
Hnh 3.9.nh FESEM ca clay ban u..62
Hnh 3.10. nh FESEM ca clay-APS.....63
Hnh 3.11. nh FESEM ca clay-VTMS..63
16
x
Hnh 3.12. Phn tch nhit TGA ca PE .......65
Hnh 3.13. Phn tch nhit TGA vt liu compozit PE/3%clay...65
Hnh 3.14. Ph nhiu x tia X ca clay66
Hnh 3.15. Ph nhiu x tia X ca vt liu compozit PE/3%clay...66
Hnh 3.16. Gin haake trn mu vt liu nanocompozit vi
thi gian trn khc nhau....69
Hnh 3.17. Gin haake vi cc tc trn mu khc nhau.......70
Hnh 3.18. nh hng ca hm lng clay-APS n
tnh cht c hc ca vt liu......73
Hnh 3.19. nh hng ca hm lng cht tng hp PE-g-AM n
tnh cht c hc vt liu.....74
Hnh 3.20. nh hng ca hm lng clay-VTMS
n tnh cht c hc vt liu...76
Hnh 3.21. nh hng ca hm lng cht khi mo DCP n tnh cht
c hc ca vt liu.......78
Hnh 3.22. Ph IR ca PE.........79
Hnh 3.23. Ph IR ca 90%PE/10%PE-g-AM /3% clay -APS .......79
Hnh 3.24. Ph IR ca PE/2% clay -VTMS/0,2%DCP........80
Hnh 3.25. Gin TGA ca PE ban u......81
Hnh 3.26. Gin TGA ca vt liu PE/3%clay-APS....82
Hnh 3.27. Gin TGA ca vt liu 90%PE/10%PE-g-AM /3% clay APS.....82
Hnh 3.28. Gin TGA ca vt liu PE/2% clay-VTMS...........84
Hnh 3.29. Gin TGA ca vt liu PE/2% clay -VTMS/0,2%DCP...84
Hnh 3.30. Ph nhiu x tia X ca clay -APS (1), vt liu nanocompozit
PE/3% clay-APS (2) v 90%PE/10%PE-g-AM /3% clay -APS (3)....86
Hnh 3.31. Ph nhiu x tia X ca clay -VTMS (1)
17
vt liu nanocompozit PE/2% clay -VTMS (2).......87
Hnh 3.32. Ph nhiu x tia X ca clay-VTMS (1), vt liu nanocompozit
PE/2% clay -VTMS/0,1%DCP(2) v PE/2% clay-VTMS/0,2%DCP(3) ......88
Hnh 3.33. nh FESEM nha PE ........89
Hnh 3.34. nh FESEM vt liu nanocompozit PE/3% clay -APS....89
Hnh 3.35. nhFE SEM vt liu nanocompozit
90%PE/10%PE-g-AM /3% clay -APS ............89
Hnh 3.36. nh FESEM vt liu nanocompozit PE/2% clay-VTMS....90
Hnh 3.37. nh FESEM vt liu nanocompozit
PE/2% clay-VTMS/0,2%DCP ...90
Hnh 3.38. nh TEM vt liu nanocompozit PE/3% clay -APS/10%PE-g-AM90
Hnh 3.39. nh TEM vt liu nanocompozit PE/2% clay -VTMS/0,1%DCP.......91
Hnh 3.40. nh TEM vt liu nanocompozit PE/2% clay -VTMS/0,2%DCP.......91
xi
18
M U
Vt liu nanocompozit l loi vt liu compozit mi v ang c cc nh
khoa hc trn th gii v trong nc ch trng nghin cu v ng dng, do c nhiu
tnh nng u vit nh: tnh cht c hc cao, n nh kch thc, thm thu kh, hi m
v cc hp cht hydrocacbon thp, bn nhit, chu bc x t ngoi, chng chy tt v
phn hy sinh hc nhanh [37,94]. V vy, vt liu nanocompozit c ng dng rng
ri trong cc lnh vc: giao thng, thng tin lin lc, in, in t, xy dng v vt
liu chng chy.
Mt trong cc loi vt liu nanocompozit v ang c quan tm nghin
cu hin nay l vt liu nanocompozit nn polyme c gia cng bng khong st
kch thc nano (nanocompozit polyme/nano-clay). y l hng nghin cu c
ch trng nhiu do kt hp c nhng tnh cht u vit ca c hp cht v c, ln
hu c cng nh nguyn liu clay r tin, sn c trong t nhin. Theo cc ti liu
nghin cu cng b th cc tnh cht nh: bn, m un n hi, kh nng chu
nhit, khng thm kh, nh, chng chy ca vt liu nanocompozit polyme/nano-
clay c tnh nng vt tri hn so vi nanocompozit gia cng bng cc ht c kch
thc khc nhau [67].
Trong t nhin c nhiu loi khong st, song loi khong st hay c s
dng nhiu nht l montmorillonit (MMT). y l loi khong st thuc nhm
smectit. S d MMT hay c dng do cu trc c bit ca n khc hn so vi cc
loi khong st khc nh: khong cch gia cc lp ln v cc ion trong khong st
d thay th bng mt ion khc. V vy, ngi ta d dng bin tnh MMT bng nhiu
hp cht hu c khc nhau to ra s tng hp gia khong st v polyme nn
[67,111].
Polyetylen (PE) l mt trong nhng nha nhit do thng dng nht, c
ng dng nhiu trong i sng cng nh trong cng nghip, do PE khng t, d gia
1
19
cng trn cc thit b cng nghip, c tnh cht c hc tt, khng cChnh v vy,
hng nm trn th gii sn xut mt lng ln PE: khong 60 triu tn [102]. Tuy
nhin, PE c nhc im l: cng thp, d b lo ho di tc ng ca cc yu t
mi trng nh: nhit , bc x, m v tnh cht chng chy ca loi vt liu ny
km...Kt qu l tnh cht v thm m ca sn phm b thay i nhanh chng, thi
gian s dng b rt ngn. Do vy, vic nghin cu v tm ra cc bin php chng
lo ha PE v nng cao thi gian s dng ca chng l cn thit v c ngha kinh t
[17,31,114].
Vi nhng l do phn tch trn, chng ti tin hnh nghin cu ti: Ch
to v nghin cu tnh cht ca vt liu nanocompozit trn c s PE v nano clay
bin tnh silan vi mc ch to ra vt liu nanocompozit bn nhit, bn thi tit v
c kh nng chng chy cao t c th ng dng sn xut vt liu bc dy cp
in.
Mc tiu ca lun n
1) Ghp silan: aminopropyltrimetoxysilan (APS) v vinyltrimetoxysilan (VTMS) ln
clay (clay-APS v clay-VTMS).
2) Ch to vt liu nanocompozit PE/ clay-APS v PE/ clay-VTMS.
3) nh gi c vai tr ca silicon trong vic ci thin tnh cht c hc, kh nng
chu lo ha ca vt liu.
4) nh gi c vai tr ca clay trong vic nng cao kh nng chu nhit, tnh cht
chng chy v tnh chng thm kh ca vt liu.
ngha khoa hc, thc tin v ng gp mi ca lun n:
Lun n tp trung nghin cu ch to, kho st tnh cht vt liu nhm a ra
c quy trnh ch to, hm lng thnh phn ti u cho h vt liu PE/clay
nanocompozit vi s c mt cht tng hp/cht khi mo phn ng. y l mt
trong nhng yu t quan trng trong vic a vt liu thu c ng dng trong ngnh
vt liu bc cp in. Cc ng gp mi ca lun n gm:
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20
- ch to c 2 loi clay hu c mi: clay-APS v clay-VTMS bng vic
ghp 2 loi hp cht silan: APS v VTMS vo clay.
- nghin cu ch to c hai c 2 loi vt liu nanocompozit mi trn
c s PE v 2 loi clay hu c, vi s c mt ca cht tng hp: PE ghp
anhyric maleic (PE-g-AM) v cht khi mo phn ng dicumyl peoxit
(DCP).
- nghin cu mt s tnh cht ca vt liu nanocompozit mi thu c:
kh nng chu lo ha, kh nng chu nhit, tnh cht chng chy v tnh
chng thm kh ca vt liu nhm nh hng ch to vt liu bc cp in.
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21
CHNG 1. TNG QUAN
1.1. Khong st t nhin v khong st hu c
1.1.1. Khong st t nhin, cu trc v thnh phn
Khong st l hp cht ca hn hp gia oxit silic v oxit nhm c hnh
thnh trong t nhin do qu trnh phong ha nhng ngun gc. N l hn hp bao
gm: SiO2, Al2O3, H2O v mt s oxit ca kim loi kim, kim th, st, mangan,
km c kch thc ht vi micromet.
Khc vi zeolit t nhin nh: modelit, faujarit c cu trc tinh th, cc n v
cu trc ca khong st l cc phin oxit silic (khi 4 mt) v phin gipxit (khi 8
mt). Mi vi phin oxit silic bao gm 1 ion Si+4 nm gia v 4 ion O-2 bao quanh, mi
phin gipxit gm 1 ion Al+3 hoc ion Mg+2 ( cu bruxit-Mg(OH)2) v 6 ion m bao
quanh O-2
v/hoc nhm OH-. Cc khi n v ny lin kt vi nhau to thnh dng
phin mng (vi phin) theo cu trc mng 2 chiu. Mng vi phin ca cc khi t
din SiO4 lin kt vi nhau thng qua nguyn t oxy v c gi l vi phin t din
(tetrahedral sheet) v mng vi phin ca cc khi bt din MO6 gi l vi phin bt
din (octahedral sheet).
Ty vo t l s tm t din trn s tm bt din m ta c cc loi khong st
khc nhau, nh: montmorillonit, vermicumit, pyrophylit, kaolinit, tal, smectit, illit,
muscovit.
Cc lp trong khong st c chiu dy c 1nm, chng lin kt vi nhau bng
lc ht tnh in v gia cc lp ny l khong trng. Tng b dy ca mt lp v
khong trng c gi l khong cch c bn (d). Khong cch c bn ny khc nhau
vi mi loi khong st, thm ch s khc bit ny cn xy ra ti nhng v tr khc
nhau trong cng mt loi khong st. Loi khong st thng dng ch to
polyme/khong st nanocompozit l bentonit/montmorillonit, do n d b tch lp v
4
22
c ng lng trao i cation ln: 80-120 meq/100g [8]. Hnh 1.1 m t cu trc
ca bentonit.
Hnh 1.1. Cu trc ca bentonit [27]
Bentonit c c im l cc ion trong cc tm t din v bt din c th b thay
th ng hnh bi cc ion khc, v d: ion Si4+ tm t din c th b thay th bi cc
ion Al3+
hoc Fe3+, cn ion Al3+ tm bt din c th b thay th bi cc Zn2+ hoc
Mg2+. Chnh s thay th bng cc cation c in tch nh hn lm cho mng tinh th
khong st tr nn tch in m v s thiu ht c b tr bi cc cation c in tch
dng nh: Na+, K+trn b mt cc lp.
Bentonit c cc tnh cht c trng nh: kh nng hp th nc, trng, c
din tch b mt ring ln v c bit l c dung lng trao i cation (CEC) cao: 80-
120 meq/100g [8].
1.1.2. Bin tnh khong st
Khong st c rt nhiu ng dng trong thc tin v lnh vc ng dng ca n
vn khng ngng tng ln. S phong ph ny l do vic bin tnh b mt ca khong
st rt d dng. Tnh cht trng n, tnh cht hp ph b mt, tnh cht keo t v tnh
cht lu bin c th c iu chnh ng dng vo nhng mc tiu khc nhau.
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23
Gn y nht cc nh khoa hc s dng khong st vi thnh phn chnh l
Montmorillonit (MMT) ch to vt liu nanocompozit lai to hu c/v c.
C nhiu cch bin tnh khong st khc nhau, nhng ph bin nht l bin tnh
khong st bng hp cht hu c (hu c ha MMT). Mc ch ca vic hu c ha
MMT l chuyn t vt liu a nc sang a du vi nhng gc th khc nhau v c
kh nng trng n trong dung mi hu c, khuych tn v tng hp tt trong cc
polyme, hay ni cch khc qu trnh hu c ha khong st l qu trnh chuyn MMT
v c thnh MMT hu c a du. Sn phm ca qu trnh bin tnh hu c khong
st ni trn c gi l khong st hu c [67]. Di y l mt s phng php bin
tnh chnh:
a. Phng php trao i cation
y l phng php xut hin cch y khong 5 thp k [23]. Trong
phng php ny, cc cation v c nh: Na+, Ca2+...gia cc lp ca khong st c
thay th bng cc cation hu c nh: mui ankylamoni, cc aminoaxit hoc cc hp
cht nhm imidazol...Qu trnh bin tnh c th m t nh sau:
M-khong st + Na+
N- khong st + Mb+
Sau khi bin tnh, b mt ca khong st tr nn k nc mt phn v n d
dng tng hp vi cc polyme hu c hn.
i vi cht bin tnh l cc ankyl amoni, khi kch thc ca nhm ankyl cng
ln th th tnh k nc ca khong st hu c thu c cng cao v khong cch c
bn ca khong st c nng ln mt cch ng k.
S sp xp mch ankyl trong khong khng gian gia cc lp khong st ph
thuc vo 2 yu t: mt in tch ca khong st v loi cht hot ng b mt.
Nhn chung, cht hot tnh b mt di v mt in tch ca clay cao th cc lp
clay s b p li v lm tng th tch chim bi nhng cht hot tnh b mt.
Vi nhng mch ankyl ngn, chng c th sp xp song song vi b mt
khong st to nn cu trc n lp (monolayer). Vi nhng mch ankyl trung bnh
6
6
24
v mch di, chng to nn cu trc a lp (hai lp, gi ba lp). Khi mch ankyl nm
cho so vi b mt ca khong st, khong st hu c c cu trc tng t nh ca
parafin [15,26, 81].
Hnh 1.2. Cu trc ca cc dng khong st hu c khc nhau [81]
b. Phng php ion lng cc
y l phng php bin tnh khong st trng thi rn da trn tng tc
ion lng cc v khng cn dung mi. Vic khng s dng dung mi trong qu trnh
bin tnh khong st nn khng gy nhim mi trng v phng php ny d c
ng dng trong cng nghip [67]. Phng php ny ln u tin c cng b bi
Ogawa M v cc cng s [77]. Nm 1995, nhm nghin cu ca Breakwell s
dng phng php ny bin tnh khong st vi mui amoni bc bn 60oC. Kt qu
thu c t ph XRD cho thy, khong cch c bn ca khong st hu c trong
khong: 1,24 - 1,27 nm.
Tip , cc tc gi [23, 45] cng bin tnh MMT bng phng php ny. Kt
qu thu c cho thy, s trao i ion l do tng tc ca cc phn t lng cc nh.
Tuy nhin, di ca mch ankyl cng c nh hng nht nh n khong st hu
c thu c. Trong phng php ny, phn t hu c c cha nhm lng cc lin
kt vi cc cation gia cc lp khong st v phn dng lin kt vi lp silica
[71,117]
c. Phng php s dng cht hot ng b mt
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25
Ngoi cc phng php nu trn, ngi ta cn dng cht hot ng b mt
bin tnh khong st, tiu biu trong s cc cht l cc hp cht silan. y l cc
monome silicon hu c, c cng thc ha hc tng qut l R- SiX3. Trong , R l
nhm chc hu c v X l nhm c th b thy phn to thnh nhm silanol. Cc
hp cht silan c th phn ng vi b mt cc cht v c to nn cc lin kt siloxan
hoc hydro. Trong khong st, cc nhm OH tn ti trn b mt ca cc lp khong
st. Khi , hp cht silan b thy phn chuyn thnh dng silanol, sau silanol kt
hp vi cc nhm OH trn b mt khong st to thnh cc lin kt siloxan v lin
kt hydro [49].
1.1.3. ng dng ca khong st hu c
Thi gian gn y, ng dng ca khong st ngy cng c m rng, nh:
lm cht xc tc, cht hp ph, vt liu khng khun, cht mang thuc su, cht cha
ph thi ht nhn... [23, 110]. Vic bin tnh khong st thnh khong st hu c
to ra nhiu kh nng ng dng mi, trong ni bt nht l: dng lm cht gia
cng trong ch to vt liu polyme/khong st nanocompozit [16,33,42,54]. Theo
Makarian [70], khong st hu c chim n 70% v trong s cc cht gia cng c
kch thc nano c dng trong ch to vt liu polyme nanocompozit. Nh qu
trnh bin tnh, khong st c kh nng tng tc tt hn v phn tn mt cch ng
u hn trong polyme nn. Nh , vt liu polyme/khong st nanocompozit c cc
tnh cht u vit hn hn so vi loi vt liu compozit thng thng khc nh: tnh
cht c l, tnh cht nhit, kh nng chng thm kh, ha cht, bn mi trng,
tnh cht chng chy...
1.2. POLYETYLEN (PE)
1.2.1. Nhu cu v ng dng polyetylen trn th gii v Vit Nam
Nn kinh t th gii chng kin nhng thay i k diu do nhng thnh
tu ca cuc cch mng khoa hc k thut mang li. Cng vi s tin b ca cng
ngh thng tin, cng ngh sinh hc th cng ngh vt liu mi (m cng ngh polyme
8
26
Triu tn
l mt trong nhng ngnh c nhiu ng dng) v ang pht trin khng ngng.
Cng ngh polyme l mt ngnh vt liu mi c kh nng sn sut ra nhiu loi sn
phm c ng dng rng ri trong nn kinh t quc dn v thay th cho nhng vt
liu truyn thng nh: st, thp, thy tinh, g, snh, sDo c cc c tnh u vit
nh: trng lng nh, hnh thc mu m p, tnh cht c l tng ng vi nhiu
vt liu khc, gi r nn cc sn phm polyme tng bc thm nhp vo tt c cc
lnh vc ca nn kinh t v cuc sng [10]. Vic s dng vt liu polyme trn th gii
v Vit Nam thc y s pht trin ca nhiu ngnh sn xut, nghin cu khoa
hc, c bit trong cc lnh vc: ch to my, xy dng, in t, ng, mng ph, bao
b.
Hnh 1.3. Sn lng nha trn th gii nm 2000-2010 (triu tn/nm)
Trn th gii, hng nm mt lng ln polyme c tiu th, c bit l PE.
Theo thng k ca mt s nh nghin cu th lng PE tiu th trong nhng nm gn
y chim 36% - 40% lng vt liu polyme tiu th trn ton th gii [36].
9
2000 2002 2004 2006 2008 2010
0
50
100
150
200
250
300
350
Nm
27
Hnh 1.4. Phn loi ht nha
Vit Nam nha l mt trong nhng mt hng xut khu c tc tng
trng nhanh nht trong 5 nm tr li y. Theo mt s bo co, nm 2009 kim
ngch xut khu nha tng 15,9%. Trong tng sn lng nha hng nm, sn phm
nha bao b chim khong 36%, trong khi nha vt liu xy dng chim khong
16%, gia dng chim khong 36% v cc ngnh cng nghip khc nh: in t,
in, giao thng vn ti chim khong 12%. Cc sn phm t nha khng nhng
thay th hu ht hng nha ngoi nhp m cn trc tip tham gia xut khu. Mt
phn ln cc sn phm c lm t nha PE, c bit l gia dng v bao b cc
loi nh: bao b mm n lp v a lp, bao b dng dt si, bao b dng ti cc
siu th pht trin rt nhanh v bt u tham gia xut khu vo cc th trng
kh tnh nh: Nht Bn, Chu c, Chu u, Chu M. Chnh v nhu cu nh vy nn
mc tng trng ca ngnh nha Vit Nam trong nhng nm gn y t t l rt
cao. V d: nm 2002 ton ngnh nha s dng 1.260.000 tn nguyn liu, trong
PE chim 26,9% t gn 400.000 tn [11]. Mc tiu trong nhng nm sp ti ca
ton ngnh nha ni chung v nha PE ni ring ca Vit Nam nh sau:
- Sn phm nha s dng tnh theo u ngi: 40kg/nm
- Nha sn xut trong nc p ng c 50% nhu cu th trng
- Sn lng ht PE t 450.000 (tn/nm)
PE-29%
PP-19%
PVC-11%
PS-8%
PET-8%
PUR-7%
khc-18%
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Hnh 1.5. Sn lng ngnh nha Vit Nam trong cc nm 2000-2010
(nghn tn)
Nhng s liu trn cho thy tm quan trng ca cc sn phm lm t nha ni
chung v nha PE ni ring, chng s ng gp mt phn khng nh vo tng thu
nhp quc dn ca c nc. Bi vy, vic nghin cu v ng dng cc sn phm
nha vo mc ch phc v i sng con ngi cn c cc nh khoa hc quan tm
v y mnh hn na.
Cc cng ngh nha m Vit Nam s dng sn xut cc sn phm nha
gm:
- Cng ngh phun p (Injection Technology): Cng ngh ny c s dng
lm cc chi tit v ph tng cho cc thit b in t, in lc, xe my v
ngnh cng nghip t. Theo cc chuyn gia cng nghip, c khong 3.000
loi thit b phun p ti Vit Nam.
- Cng ngh n-thi (Blow-Extrusion Technology): y l cng ngh thi
mng sn xut cc loi vt liu bao b nha t mng nh: PE, PP v mng
PVC.
- Cng ngh sn xut nha thanh Profile (Profile Technology): Vit Nam,
cng ngh ny c s dng lm cc sn phm nh: ng nc PVC, ng
nc PE, ng nhm-nha, cp quang, ca PVC, khung hnh, tm lp, ph
tng
Nm
Nghn tn
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1.2.2. ng dng ca PE
PE c tnh cht c, l, ho tt, v vy chng c s dng trong nhiu lnh
vc k thut cng nh trong i sng, nh: chai, l, mng mng bao b, ng dn
nc, bn tm, cc chi tit xe hi
PE cng c dng nhiu cho cc sn phm bn vi dung mi v du nht
nh: thng cha dung mi, chai l, mng mng, bao b.
Do c tnh cht cch in tt nn PE c dng nhiu trong ngnh k thut
in sn xut dy cch in, vt liu in lm vic tn s cao nh: dy v bc
dy cp in, bng cch in. Dy cp bc bng PE c u im hn so vi dy cp
bc bng cao su v nh hn, d un hn v c hiu in th nh thng cao hn.
1.2.3. Tnh cht ca PE
1.2.3.1 Cu trc phn t v hnh thi hc
Cc cng trnh nghin cu cho thy, PE c cu trc kt tinh nh parafin nhng
kt tinh khng bao gi t 100% v trong qu trnh sn xut PE lun c s xen ln
gia cc pha kt tinh v pha v nh hnh. Tinh th hon ho nht cng cha 5 10%
v nh hnh .
Cc mt xch ca PE ngn, c khong 2,33 Ao nn PE c kh nng kt tinh
nhanh. iu kin nhit thng, kt tinh ca PE nh hng trc tip n cc
tnh cht ca PE nh: t trng, cng, modun n hi un, bn t, trng v
kh nng ho tan trong cc dung mi hu c. Da vo trng lng phn t, t trng,
kt tinh v cu trc, PE c phn loi nh sau:
- LDPE (PE t trng thp): PE c cu trc mch nhnh, t trng: 0,910- 0,925
g/cm3, nhit nng chy: 108-115 oC, nhit ho thu tinh Tg -110
oC, kt
tinh: 55-65%.
- LLDPE (PE t trng thp mch thng): l sn phm ng trng hp ca
ethylen vi alpha-olefin c mch cacbon di hn nh: buten, hexen hoc octen.
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30
LLDPE c trng lng phn t cao v khng ng nht v mt ho hc, c th bao
gm c HDPE, t trng: 0,915-0,925 g/cm3.
- HDPE (PE t trng cao): PE c mch thng di, hm lng kt tinh cao: 74-
95%, nhit nng chy: 130-135oC, t trng: 0,941-0,965 g/cm3.
Hnh 1.6. Cu trc ca 3 loi PE [19]
Ngoi ra cn c mt s loi khc PE khc vi cng ngh sn xut phc tp hn
v t thng dng hn, nh:
-VLDPE (PE t trng rt thp): l loi PE ch yu l mch thng, cn cc
mch nhnh rt t, t trng: 0,880- 0,915 g/cm3.
-MDPE (PE t trng trung bnh): t trng ca PE ny khong: 0,926- 0,940
g/cm3.
-UHMWPE (PE c khi lng phn t rt cao): l loi PE c khi lng
phn t trung bnh s t 3,1 n 5,67 triu. Loi PE ny rt cng nn c dng lm
si v lp lt thng n. T trng: 0,930- 0,935 g/cm3, nhit nng chy Tnc
130oC.
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1.2.3.2. Tnh cht ca PE
LDPE v LLDPE l nhng cht rn kh trong v mm do, cn HDPE li l
cht rn c mu trng c v cng. PE l loi polyme khng b ho tan trong bt c
loi dung mi no nhit thng. Tuy nhin khi ngm trong cc hydrocacbon
thm, hydrocacbon clo ho, du khong v parafin trong mt thi gian di th PE b
trng ln v gim bn c hc. Tnh cht c hc ca PE ph thuc vo trng
lng phn t v kt tinh ca n. Ngoi ra n cn ph thuc vo nhit , nhit
cng lm thay i mt s tnh cht c l ca sn phm nh: kch thc v cng.
PE cng rt nhy cm vi bc x t ngoi. Hin tng ny chnh l s phn hu
quang PE. Tng t nh parafin, PE bt chy chm, chy khng khi. Trong mi
trng khng c oxi PE bn ti 290oC. nhit khong: 290 350 oC PE b phn
hu thnh sn phm phn t khi nh, b ngoi tng t nh sp. nhit trn
350oC sn phm phn hu l polyme dng lng v cc sn phm khc nh: buten,
etylen, etan, hydro, oxit cacbon, kh cacbonnic v cc cht khc [12].
1.2.3.3. ho tan
PE c nng lng b mt thp nn khng thm nc v cc dung mi phn
cc. bm dnh v kh nng hp ph ca PE thp, chnh v vy, PE kh nhum
mu, kh kt dnh bng cc cht kt dnh phn cc. nhit thng, PE khng ho
tan trong bt c dung mi no, nhng khi tip xc lu vi dung mi mch thng,
vng thm hoc hirocacbon clorua n b trng. nhit khong 70oC PE tan
mt phn trong mt s dung mi ( v d: trong xylen).
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32
Bng 1.1. S ph thuc ho tan ca PE vo nhit trong xylen
Ngoi ra, ho tan ca PE cn ph thuc rt mnh vo trng lng phn t.
Bng 1.2. S ph thuc ho tan ca PE vo
trng lng phn t trong xylen 70 oC
Trng lng phn t ho tan (%)
9.400 12,0
11.000 10,0
13.000 2,0
16.000 0,3
31.000 0,05
40.000 0,01
1.2.4. Cc phng php khu mch PE
Trn th gii, PE khu mch c ng dng nhiu ch to cc sn phm
phc v trong cng nghip, cng nh trong i sng. Chu u, ng polyetylen
khu mch (PEX) c a ra th trng vo nhng nm 70 ca th k XX. Vt liu
PEX rt mm do v d lp t, kh b rn b nt di tc ng ca ngoi lc v bn
nhit cao. V nhng u im trn nn cc ng PEX rt c a chung v thm
Nhit (oC) ho tan (%)
20 0,008
58,5 0,25
69 0,98
78 10,2
15
33
To
nhp th trng nhanh chng. Tuy nhin, c mt vn c t ra v gy tranh ci
l: xy c th khuch tn qua cc ng PEX hay khng? Chnh vn lm chm li
qu trnh pht trin ca PEX. Vn ny cng c gii quyt bng cch s dng lp
ngn cch trong ng PEX v s lng sn phm ny tng 20%/nm chu u. Ti
M, vic s dng cc ng PEX cho cc h thng t nng bt u vo nhng nm 80.
Tuy nhin, ch n gia v cui nhng nm 80 khi tiu chun ASTM c cng b
(1984) th mi c s bng n v s lng sn phm. C nhiu phng php khu
mch PE c s dng: khu mch bng peoxit, khu mch bng tia bc x beta
v khu mch bng cc hp cht silan.
1.2.4.1. Khu mch bng peoxit
Trong phng php ny, PE c trn ln vi peoxit hu c nh: dicumyl
peoxit (DCP), benzoyl peoxit (BP), cht chng oxi ho v mt s ph gia khc, sau
hn hp trn c a vo thit b trn nng chy (kn hoc h) hoc trn thit b
n. Nhit v thi gian phn ng ph thuc vo nhit nng chy ca PE, cng
nh nhit v thi gian phn hu ca peoxit [14]. Phn ng xy ra theo c ch:
a. Phn ng phn hu ca peoxit: di tc ng ca nhit peoxit phn
hu thnh cc gc t do.
R-O-O-R 2 RO.
Hai loi peoxit hay c s dng l DCP v BP, trong nhit phn hu
ca DCP khong 160oC v ca BP khong 130oC [47]. V vy, 2 loi peoxit ny
thng c s dng khu mch PE.
b. Phn ng khi mo: phn ng xy ra khi gc t do ca peoxit bt 1
nguyn t H trong PE to ra gc polyme P..
RO. + P-H R-O-H + P
.
c. Phn ng khu mch: phn ng xy ra khi hai gc P. kt hp vi nhau to
ra PE khu mch.
P. + P
. P- P
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34
Bng 1.3. Mt s loi peoxit thng dng v thi gian bn phn hu ca chng
Loi peoxit Khi lng phn t
Nhit bn phn hu (oC)
6 pht 1 gi
10 gi
t-butyl peoxyisopropyl cacbonat 176,2 137 114 94
2,2-di-t,butyl peoxybutan 234,3 138 114 92
t-butyl peoxy stearyl cacbonat 386,6 138 114 93
t-butyl peoxy axetat 132,2 141 117 95
t-butyl peoxy benzoat 194,2 146 122 101
Dicumyl peoxit 270,4 155 128 104
2,5-dimetyl-2-5-t-butyl-peoxy hexan 290,4 159 132 108
t-butyl cumyl peoxit 208,3 160 131 106
Bis(t,butyl peoxy isopropyl) benzen 338,51 160 133 110
di-decanoyl peoxit 342,5 99 79 60
di-octanoyl peoxit 286,4 100 79 61
di-lauryl peoxit 398,6 62 80 62
t-butylpeoxy2-etylhexanoat 216,3 111 90 70
t-butylpeoxy dietylaxetat 188,3 112 86 68
dibenzoyl peoxit 242,2 116 92 71
1.2.4.2. Khu mch bng tia bc x beta (PEX-b)
Qu trnh khu mch PE bng tia bc x beta c m t nh sau: hn hp bao
gm PE, cht n nh, bt mu v mt s ph gia khc c a vo my v n
thnh dng ng. Nhng ng ny c chy di chm tia electron nhiu ln, sau
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35
cun li thnh vng. Cc chm tia electron hay tia bc x beta c di chuyn rt
nhanh t mt my gia tc electron. i vi qu trnh khu mch PE dng ng cn c
mt in th hng triu vn chm tia bc x xuyn qua vt liu v to ra qu trnh
khu mch ng nht. Di tc dng ca tia bc x, nguyn t hidro b bn v tch ra
to thnh phn t H2 thot ra. Cc mch PE to thnh gc polyme, chng lin kt vi
nhau to thnh mng li 3 chiu. Cng v s lng electron bn vo PE s
quyt nh mc khu mch [14].
S sau trnh by qu trnh khu mch PE bng tia bc x beta:
a. Qu trnh to gc polyme di tc dng ca chm tia bc x beta:
2PH + nng lng 2P. + 2H.
b. Qu trnh khu mch:
2P. + 2H
. P-P + H2
1.2.4.3. Khu mch bng cc hp cht silan
a. C s ca phn ng ghp silicon ln mch PE
V mt ho hc, silicon c lin kt Si-O di: 0,164 nm, gc lin kt Si-O-Si
ln: 143o, nguyn t O linh ng do khng b n ng khng gian, nn nhm th R
gn vi nguyn t Si d quay xung quanh trc lin kt. Nng lng lin kt Si-O kh
cao: 106 kcal/mol [96]. Do c im cu trc nh vy nn silicon rt mm do, bn
nhit, chu kh hu, bn vi bc x t ngoi, k nc, c tnh cht c hc kh cao,
tnh cht in mi tt v c khong nhit s dng rng -100 300oC [1,96].
b. Nguyn l v cng ngh ghp silicon ln PE
Qu trnh ghp silicon ln PE bao gm nhiu giai on. u tin PE c ghp
vi silan trong my n trc khi n thnh dng ng. Cc ng sau khi c n ra,
thng c mc khu mch thp, v phn ln cc lin kt Si-O-Si gia cc phn t
polyme c to thnh sau khi tip xc vi m. Khi bo qun cc ng ny nhit
phng vi m trung bnh, qu trnh khu mch c th ko di hng thng. Thi
gian khu mch ca vt liu c th gim xung mt cch ng k (trong mt vi gi)
18
36
khi c s l mi trng nhit v m cao hoc lu thng dng nc nng
trong ng. i vi nhng ng dy ln, vic s l bng nc nng c th ko di
trong nhiu gi [114]. Qu trnh ghp silicon ln PE xy ra nh sau (v d: vi
vinyltrimetoxysilan- VTMS) [1]:
- Phn ng phn hu ca peoxit: di tc ng ca nhit to thnh cc
gc t do:
R-O-O-R 2RO.
- Phn ng khi mo: sau gc t do ca peoxit bt nguyn t H ca PE
to ra gc polyme P.
- Phn ng ghp silan ln PE: Phn ng ghp vinyltrimetoxysilan ln PE
xy ra nh sau:
- Phn ng khu mch PE: qu trnh ny xy ra do lin kt gia cc gc
polyme c ghp silan vi nhau v di tc ng ca hi m trong mi
trng hoc nc trong qu trnh lm lnh, cc nhm metoxysilan b thu
phn to thnh nhm silanol -SiOH. Cc nhm ny trng ngng vi nhau a
n PE khu mch, trong mch phn t ca PE c cc lin kt Si-O-Si,
lin kt c trng ca polyme silicon :
CH2
CH2
CH2
RO HC
CH2
CH2
ROH
HC
CH2
CH2
H2C CH Si(OR) 3 HC
CH2
CH2
CH2 CH Si(OR)3
19
37
Cng c kin cho rng phn ng gia PE v hp cht silicon nn gi l phn
ng lu ho hn l phn ng khu mch v trong c mt cu ni gia cc chui
polyme ch khng ch l lin kt cacbon-cacbon [50].
Jenn Fong Kuan v cc cng s gn y nghin cu khu mch ca: HDPE,
LDPE v LLDPE ghp vinyltrimetoxysilan bng hi nc. Cc kt qu cho thy:
bn ko t ca HDPE ghp silan tng 31%, trong khi dn di tng i gim
xung do phn tinh th trong HDPE b ph hu. bn nhit ca vt liu cng tng
ln theo thi gian khu mch. i vi LLDPE, bn va p ca LLDPE ghp silan
tng ln theo thi gian khu mch. Tuy nhin, bn ko t v dn di tng i
ca LDPE ghp silan khng thay i nhiu. iu ny c th do LDPE c cu trc
mch nhnh, lm cho qu trnh khu mch bng silan khng thun li [52].
c. Tnh cht ca PE khu mch bng silicon [41]
- Nhit s dng cao
- Bin dng t di tc ng ca ti trng, chu ro tt
- bn ho cht c ci thin
- Bn mi trng
- Tnh chu mi mn tng, chu va p
CH2
CH
CH2
CH2 CH2 Si
OH
OH
OH HO
OH
OH
Si CH2 CH2 CH
CH2
CH2
CH2
CH
CH2
CH2 CH2 Si
O
O
O Si
O
O
CH2 CH2
CH2
CH
CH2
20
38
Bng 1.4. Tnh cht ca HDPE khu mch bng vinyltrimetoxysilan (VTMS)
Thi gian khu mch
Tnh cht
HDPE
HDPE-g-VTMS
0 h 0,5 h 1 h 3 h 6 h
bn ko t (Kgf/cm
2)
247,9 326,3 346,3 346,1 348 344,4
dn di tng i (%)
239,7 48,4 35,9 31,5 39,2 46,9
bn un (Kgf/cm2) 310,2 357,1 382 382,7 391 391,7
Moun un (Kgf/cm2) 9512,5 9240,6 10170,9 10613,6 10893,8 10975,9
bn va p theo Izod (J/M)
783,2 404,8 371,5 310,8 364,3 388,5
bn nhit (oC) 78,1 84,1 96,1 97,3 100,7 101,2
1.2.4.4. Khu mch PE bng bc x t ngoi
Khu mch PE bng tia bc x t ngoi c Ositer v cc cng s nghin cu
t nm 1950. Bng vic s dng bc x t ngoi trong vng 200-300 nm cc tc gi
nhn thy rng thi gian chiu x c th gim i 1000 ln nu s dng cht khi mo
quang l hp cht benzophenon. Phng php khu mch n gin ny rt c ch
v c nhiu cng trnh nghin cu c cng b. Tuy nhin, cho n trc nm
1990 cha c kt qu no c ng dng trong thc t do gp kh khn trong khi
khu mch cc sn phm PE c dy ln, v tia UV kh xm nhp vo khi PE
bn trong v tc khu mch PE xy ra chm. Khu mch PE bng tia UV c nhiu
u im nh: thit b n gin, khng tn km, polyme t b phn hu v khng b
oxy ho trong qu trnh khu mch, v vy y l vn vn lun c cc nh khoa
hc quan tm. Mt iu ng ch l gio s Ranby v cc cng s tng hp
c cc cht khi mo quang hot ng theo c ch gc dng khu mch PE
trng thi nng chy ch to dy v cp. Cng chnh h l nhng ngi xy
21
39
dng c mt h thng cng ngh hon chnh cho php trin khai khu mch cp v
dy trong cng nghip [22].
a. Cht khi mo quang ho
Trong cng nghip ngun sng t ngoi thng c s dng l cc n thu
ngn vi p sut cao thp khc nhau, bc sng trong khong: 200-400 nm. PE l
mt polyme khng c nhm hp th nh sng, v vy kch thch qu trnh khu
mch ngi ta s dng cc cht khi mo quang. Mt iu cn lu l khi s
dng cc n thu ngn phi la chn sao cho vng bc x nh sng ca n ph hp
vi ph hp th ca cht khi mo quang. Cht khi mo quang s dng cho qu
trnh khu mch PE c chia thnh hai nhm:
- Nhm 1: cht khi mo b ct t di tc ng ca tia t ngoi (nh:
aryl keton R1-Ph-CO-R2).
- Nhm 2: cht khi mo khng b ct t di tc ng ca tia t ngoi
(nh benzophenol hoc xanthol) m hot ng theo c ch bt nguyn t
hidro (H) hoc chuyn dch in t.
Chen v cc cng s s dng 18 loi cht khi mo khc nhau khu mch
HDPE v nhn thy: nhm khi mo hot ng theo c ch bt nguyn t H hiu
qu hn so vi nhm cht khi mo hot ng theo kiu ct t. Khi s dng ng
thi hai loi cht khi mo th tc khu mch tng ln giai on u [18].
b. Cht khu mch
Trong h thng khi mo quang, phi c t nht mt trong hai monome hot
ng nh mt cht khu mch. H thng khi mo quang bao gm: cht khi mo
quang v cht khu mch s xc tin cc phn ng khu mch.
V d: h 4-clobenzophenon/trialylcyanurat (4-CBT/TAC) trong TAC l
mt cht khu mch c 3 nhm alyl lin kt vi vng cyanurat bn nhit, rt c hiu
qu lm tng tc khu mch ca polyme.
22
40
Cc kt qu nghin cu [22] cng cho thy, tc khu mch ca PE ph
thuc rt mnh vo cu trc ca chng v sp xp nh sau:
HDPE > LLDPE > LDPE.
c. C ch qu trnh khu mch
Qu trnh khu mch bao gm cc phn ng chnh sau:
- Phn ng khi mo: Di tc ng ca tia UV, cht khi mo quang bt
mt nguyn t H ca PE theo s sau:
PH P. + .H
- Phn ng pht trin mch: Gc P. sinh ra phn ng vi ni i ca cht
khu mch TAC theo s sau:
P. + TAC PTAC
.
P. + nTAC PTACn
.
- Phn ng khu mch:
Phn ng khu mch xy ra nh sau
P. + P
. Crosslinking (khu mch)
P. + PTAC
. Crosslinking
P. + PTACn
. Crosslinking
d. u im ca phng php khu mch quang ho
So vi cc phng php khu mch PE khc, khu mch PE bng phng php
quang ho (i vi cc sn phm PE c dy mng) c mt s u im sau:
- Gi thnh thp hn so vi cc phng php khc
- Thi gian khu mch nhanh
- Khu mch xy ra nhit phng
- Khng s dng dung mi nn khng gy nhim mi trng.
23
41
- Quy m nh xng v thit b nh, gn.
- Tn t nng lng.
- iu kin kim tra n gin, d thao tc
- Tnh cht in v tnh cht c hc cao.
1.3. HP CHT LIN KT C SILIC
1.3.1. Lch s pht trin
Vn nghin cu lin kt thu tinh/nha b mt ranh gii xut hin vo
nhng nm 1940 cho cc sn phm lm bng compozit trn nn nha polyeste v gia
cng bng si thy tinh, do bn ca nhng sn phm ny b gim mnh, c bit
l bn un, khi s dng chng trong mi trng m. Tt c nhng nghin cu
nhm to ra lin kt trc tip thu tinh-polyme u khng thnh cng. Kh khn mt
phn l do h s dn n nhit ca 2 loi vt liu rt khc nhau: epoxy: 4-8, polyeste:
5-10, PP: 10-20, PA: 8-10, trong khi thy tinh ch c: 0,4-0,5.10-2/oC). Mt nguyn
nhn khc l do si thy tinh ht m. Hn na, phn ln cc polyme nhit rn b co
ngt mnh trong qu trnh ng rn: epoxy: 3-4%, polyeste: 6-10%. Mt tr ngi
khc cho vic hnh thnh lin kt thu tinh-nha l do khng th loi ton b nc ra
khi b mt si thu tinh. T y, ngi ta nhn ra rng, s l b mt si thy tinh
bng trimetylclosilan s to ra trn b mt si thu tinh lin kt Si-O-Si k nc.
Nhng nhm -CH3 khng c kh nng to ra lin kt tt vi nn polyme. Do vy, cn
phi tm ra hp cht c 2 nhm chc c kh nng to ra cu lin kt gia nha v si
thu tinh. Hp cht ny gi l cht lin kt hay gi l cht to cu. N cn phi c
mt nhm chc phn ng vi thu tinh v mt nhm chc khc c kh nng phn
ng vi nha.
Cht lin kt u tin s dng trong cng nghip l mt hp cht phc ca
crom v metacrylat. Clorua crom to lin kt tt vi thy tinh, cn metacrylat c th
phn ng vi ni i ca polyeste.
1.3.2. Cu to ca cc cht lin kt c silic
24
42
RO
Si
RO
RO R' F
Cht lin kt c silic (silan hu c) c cng thc tng qut nh sau:
Hnh 1.7. Cng thc ca cc cht lin kt c silic
y RO: l nhm alcoxy c kh nng thy phn v phn ng vi cht gia cng
nh: -OCH3, -OC2H5...
F: l nhm chc hu c c kh nng lin kt hoc tng hp vi nn polyme: amin,
epoxy, mecaptan...
R': mch hydrocacbon lin kt vi Si.
1.3.3. C ch hot ng ca cht lin kt c silic trong vt liu compozit
Vt liu compozit bao gm hai thnh phn chnh, vt liu nn v cht gia
cng (ct) dng ht hay dng si. Tnh cht c hc ca vt liu compozit khng
nhng ph thuc vo bn cht ca vt liu nn v cht gia cng m n cn ph
thuc vo cht lin kt gia chng ranh gii chuyn tip. V vy c lin kt tt
cht gia cng thng phi c x l trc khi i vo s dng, trong cc cht
lin kt c silic thng c s dng nhiu nht x l cht gia cng.
Cht lin kt silic s l b mt cht gia cng thng dng thu phn,
c nhm silanol. C 2 phn ng xy ra ng thi, khi s l b mt cht gia cng
bng cc cht lin kt silic (hnh 1.8):
- Phn ng gia nhm SiOH ca cht lin kt silic v nhm SiOH trn b mt
thy tinh to thnh lin kt hydro hoc cu siloxan Si-O-Si.
- Phn ng trng ngng gia cc nhm SiOH cn li vi nhau to thnh
polysiloxan.
25
43
Si OR'
OR'
OR'
R
OH2
Si OH
R
OH
OH Si
OH
O
Si OH
R
OH
H
Si
OH
O
Si OH
R
H
O
H
Si
OH
O
Si
R
OH
H
O
H* Si O Si O
R R
O
HO
H
O
SiSi
*n
-H2O
Thy phn
Trng ng-ng
Hnh 1.8. S to thnh mng phim polysiloxan trn b mt thy tinh
S hnh thnh lp chuyn tip gia si thy tinh/cht lin kt c silic/vt liu
nn xy ra nh sau: u tin nhng nhm RO ca cht lin kt silic b thu phn to
ra cc nhm silanol, v cc nhm silanol ny to lin kt hydro hoc lin kt siloxan
vi vt liu v c, cn nhng nhm chc F phn ng vi vt liu nn hu c to ra
lin kt cht ch theo s trn (hnh 1.9).
Hnh 1.9. S ca pha chuyn tip gia thu tinh v vt liu nn
nh hp cht lin kt c silic.
Si OH
Si O Si
O
O
Si
Si O
H
H
SiO
O
N
NSi O
H
H
N
B mt
thy tinh Lp chuyn tip
Nn nha
26
44
1.3.4. Lnh vc ng dng ca cc cht lin kt c silic
Cht lin kt c silic c s dng rng ri nh: lm cht lin kt trung gian
gia vt liu v c v hu c, gia cht gia cng v nn nha trong polyme
compozit, cht khu mch cho cp in v dy thng tin, s l b mt kim loi...
Ngoi ra chng cn c ng dng trong mt s cc lnh vc khc nh: nha, b
tng, sn, keo dn, mc in... Sau y l mt s lnh vc ng dng c th:
- Keo dn: thch hp vi keo c cha nc hoc du. Hi m ng li nha
lm tng dnh, bn ho hc, kh nng chu thi tit v lin kt cht
n/nh.
- Lp ph v sn: lm tng bm dnh trn b mt ca sn v kim loi,
thm t, kh nng chu thi tit, kh nng phn tn bt mu.
- Si thu tinh v mat thy tinh: tng kh nng bm dnh vi nha nhit do
khi c x l bng cht lin kt c silic.
- X l cht n: tng s lin kt ca nha v cht n v s phn b cht n
trong nha nhit do.
- hoa nhn to: tng s lin kt gia nha nhit rn v cht n.
- Mc in: tng bm dnh, thm t.
- Cao su v elastome: tng s lin kt, chng s vn cc ca nha/cht n,
tng tnh cht in.
- Nha nhit do : khu mch nha PE lm cp, dy...
- Bin tnh polyme: khu mch polyme nng cao bn mi trng
- Vt liu dt: lm cho vt liu dt do hn, chu nc v tng kh nng nhum
mu.
1.4. VT LIU NANOCOMPOZIT POLYME/CLAY
1.4.1. Phn loi
Tu theo cch thc phn b hay dng tn ti ca clay trong nn polyme m
ngi ta phn loi nanocompozit polyme/clay ra thnh cc loi sau (hnh 1.10):
27
45
Hnh 1.10. Cc dng nanocompozit polyme/clay
a. Dng chn lp (intercalated nanocomposite)
L dng nanocompozit m trong cc phn t polyme c chn vo gia
cc lp clay v khong cch gia cc lp clay c tng ln song vn cn cu trc
lp.
b. Dng kt t (floculated nanocomposite)
Trng hp ny cng ging nh trng hp chn lp, nhng c hin tng
mt s lp clay dnh vo nhau do tng tc hydro gia cc lp. Dng ny c tnh cht
c hc khng tt bng dng chn lp v hin tng kt t lm cho khong st phn b
khng u trong nn polyme.
c. Dng bc lp (exfoliated nanocomposite)
y l trng hp m cc lp clay tch hon ton khi nhau v phn tn
u trong nn polyme. V vy, tng tc gia pha nn v pha gia cng trong trng
hp ny l tt nht. Hin tng bc lp xy ra khi hm lng clay nh v tng tc
gia pha nn polyme v clay tt nht.
1.4.2. Cc phng php ch to vt liu polyme/clay nanocompozit
Hin nay, trn th gii c cc phng php thng dng ch to polyme clay
nanocompozit l: phng php chn lp, phng php trng hp ti ch (in- situ
polymerization) v phng php trn hp nng chy.
28
46
1.4.2.1. Phng php chn lp
a. Phng php chn lp trong dung dch
Trong phng php ny, clay c a vo trong dung dch polyme v c
khuy trn mnh. Sau dung mi s chui vo gia cc lp clay v lm cho clay
trng n, khong cch c bn gia cc lp khong st tng ln, nh polyme d
dng chn vo gia cc lp clay. Sau khi lm bay hi dung mi ta s thu c
polyme/clay nanocompozit (hnh 1.11). Dung mi thng c s dng l: nc,
clorofoc, toluen. Phng php ny thng c dng ch to polyme/clay
nanocompozit ng dng lm lp ph bo v.
Hnh 1.11. Qu trnh to thnh vt liu polyme/clay nanocompozit bng
phng php chn lp trong dung dch
u im ca phng php ny l khng cn bin tnh clay do dung mi ng
vai tr kch lp clay, lm tng khong cch c bn gia cc lp. Tuy nhin, phng
php ny c nhc im l dung mi sau khi c tch ra gy nhim mi trng v
t c s dng v mc ch kinh t [86].
b. Phng php chn lp trng thi nng chy
Nguyn l ca phng php ny nh sau :
29
47
Trong phng php ny, clay hu c v polyme c trn nhit gia cng
trong cc thit b gia cng polyme nh: my cn, my n, my phun. Trong qu
trnh trn, di tc dng ca ng sut trt, cc phn t polyme s chn vo gia cc
lp ca clay hu c to thnh vt liu polyme/clay nanocompozit. Qu trnh chn
lp trng thi nng chy c m t nh hnh 1.12. Phng php ny thng c
p dng cho cc polyme nhit do v hin ang l phng php thng dng v kinh
t nht ch to vt liu polyme nanocompozit.
Hnh 1.12. Qu trnh chn lp trng thi nng chy
Nha nhit do u tin s dng phng php chn lp trng thi nng chy
ch to polyme nanocompozit l polystyren (PS). Ngi ta trn PS dng ht vi
clay hu c nhit trn 165oC. Bng phng php nhiu x tia X v knh hin vi
in t truyn qua, ngi ta chng minh c sn phm thu c l polyme/clay
nanocompozit [95].
Cho ti nay, ngi ta ch to thnh cng vt liu nanocompozit polyme/clay
t hu ht cc nn nha nhit do nh: polyetylen (PE), polypropylen (PP), nilon 6,
poly(etylen terephtalat) (PET) [29]. Trong , PE v PP l 2 loi nha nhit do c
quan tm nhiu nht[16,20,31,42,48]. Trong qu trnh ch to, do c tnh khng phn
cc ca cc polyolefin nn chng rt kh tng hp vi clay hu c, do vy qu trnh
chn cc phn t polyme vo gia cc lp clay thng kh thc hin. khc phc
30
48
PE-g- AM
hin tng ny, ngi ta tin hnh bin tnh polyme bng cch a cc nhm phn
cc vo phn t polyme thng qua phn ng ghp v s dng cht tng hp c cha
cc nhm chc nh: nhm -OH, -CO nhng nhm ny c th lin kt tt vi clay,
cn mch hydrocacbon ca cht tng hp th tng hp vi nn polyme. in hnh
nht l bin tnh PP, PE bng anhydric maleic (AM) to ra PP v PE ghp AM (PP-g-
AM, PE-g-AM) v s dng chng lm vt liu nn trong polyme/clay nanocompozit
[41,55,80].
Phng php chn lp trng thi nng chy c u im hn so vi phng
php chn lp trong dung dch v phng php chn lp trng thi chy khng s
dng dung mi do vy s gim tc hi n mi trng v sc khe con ngi.
Hnh 1.13 . S hnh thnh polyme/clay nanocompozit t clay
hu c v nn nha PE bin tnh
1.4.2.2. Phng php trng hp ti ch (in- situ polymerisation)
Phng php trng hp ti ch c tin hnh da theo nguyn l nh sau:
trc tin, khong st c phn tn vo dung dch monome cc monome chn
vo gia cc lp clay, sau tin hnh trng hp monome thu c polyme
nanocompozit.
31
49
Hnh 1.14. S tng hp Nylon 6/clay nanocompozit t caprolactam
Phng php ny c p dng ch yu vi cc monome dng lng v c th
tng hp tt vi clay, tc l c kh nng lm trng n clay. c nhiu cng trnh
cng b lin quan n phng php ny, song ch yu dng vi cc monome nh:
anilin, caprolactam, styren, acrylnitril.
u im ca phng php l khng cn bin tnh clay, cng nh phn tn
ca clay trong nn polyme l tt, tuy nhin vic kim sot qu trnh trng hp li kh
phc tp v ch p dng hn ch i vi cc monome dng lng v c th lm
trng n clay.
1.4.2.3. Phng php trn hp trng thi nng chy
y l mt trong nhng phng php c ng dng rng ri bi qu trnh
trn hp rt tin li v n gin: polyme nn v cht gia cng (nano kim loi, nano-
SiO2) c trn t l thch hp, tu theo yu cu ca sn phm, sau tin hnh
ch to vt liu nanocompozit bng cc thit b gia cng polyme nh: my n, my
c phun. Chnh v c th s dng cc thit b trn, nn y l phng php d trin
khai sn xut quy m cng nghip [6]. Tuy nhin, cn phi la chn cng ngh v
iu kin gia cng thch hp sao cho cc ht gia cng vi kch c nano c phn
tn tt trong nn polyme khi mi thu c vt liu c tnh cht nh mong mun.
Trong qu trnh trn hp nng chy polyme khuch tn vo cc lp MMT hu
c lm tng khong cch gia cc lp v lm gim lc tng tc gia chng a n
vic tch lp MMT, lm cho n phn tn tt trong nn polyme. Trong phng php
32
50
ny, s c mt ca lng ln cht hot ng b mt phn t lng thp ( bin tnh
MMT) nh hng mnh n hiu qu gia cng. Do lc tnh in mnh gia cc lp
MMT, chng khng d dng tch ra v tng hp gia polyme v MMT rt kh, do
ngi ta thng s dng mui amoni c mch ankyl di x l MMT trc nh
phn ng trao i ion, nhm mc ch gim tng tc gia cc lp, nng cao kh
nng tng hp v lm gim tnh thm t ca MMT vi nn polyme. Vi cc mui
amoni c mch khc nhau th hm lng s dng khc nhau. Tuy nhin, cc mui
ankyl amoni c bn nhit thp nn khi gia cng khng trnh khi s phn hy
[15].
1.4.3. Cc phng php kho st cu trc vt liu polyme/clay nanocompozit
Hai phng php hay c s dng kho st cu trc ca vt liu
polyme/clay nanocompozit l: phng php nhiu x tia X (XRD) v phng php
knh hin vi in t truyn qua (TEM) [15, 27, 87].
1.4.3.1. Phng php ph nhiu x tia X (XRD)
Vic phn tch cu trc vt liu qua ph XRD c thc hin kh d dng, v
vy y l phng php kh c a chung [79].
Phng php ny da vo phng trnh Bragg:
sin = n/2d
Trong : l chiu di bc sng ca tia X
d: khong cch c bn ca clay
: gc nhiu x
i vi mi loi vt liu thu c, ph XRD c c im khc nhau:
- Vi vt liu polyme/clay khng trn ln hay vt liu nanocompozit dng kt
t: trn ph XRD khong cch c bn d001 ca vt liu hu nh khng thay i
so vi d001 ca khong st ban u.
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51
- Vi vt liu nanocompozit polyme/clay dng chn lp: ph XRD c pic d001
thay i so vi d001 ca clay ban u v thng dch chuyn v gc c cng
nh hn.
- Vi vt liu nanocompozit polyme/clay dng tch lp: khng xut hin pic d001
ca h vt liu trn ph XRD.
Hnh 1.15. Ph XRD ca cc dng vt liu polyme/clay
(a) Polyme/clay khng to thnh dng nanocompozit
(b) Polyme/clay to thnh dng nanocompozit chn lp
(c) Polyme/clay to thnh dng nanocompozit tch lp
1.4.3.2. Phng php hin vi in t truyn qua (TEM)
Phng php ny vi phng i cao cho php kho st cu trc bn trong ti
mt v tr xc nh ca vt liu polyme/clay nanocompozit, t c th quan st
nhng khuyt tt trong cu trc ca vt liu [15,74]. Thng thng, nh TEM thu
c cc vt en ca khong st (do c cha cc nguyn t Al, Si, O) trn nn
polyme sng mu hn.
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52
1.4.3.3. Phng php ph hng ngoi (IR)
Mt s tc gi cng s dng ph IR trong phn tch cu trc ca vt liu
nanocompozit [66, 107]. Ph IR c th cho php phn bit lin kt trong hn hp v
lin kt ha hc trong vt liu nanocompozit. Tuy nhin, nhng s khc nhau nhiu
khi rt nh, v vy vic s dng ph IR trong phn tch vt liu nanocompozit lun
cn c s phi hp vi cc phng php khc.
1.4.4. Mt s tnh cht ca vt liu polyme/clay nanocompozit
Vt liu polyme/clay nanocompozit c nhng tnh cht u vit hn hn vt liu
compozit thng thng, trong ng ch l: tnh cht c hc cao, kh nng chu
nhit v chng chy tt..
1.4.4.1. Tnh cht c hc:
Do c tng tc v kt dnh tt gia pha nn v pha gia cng nn vt liu
polyme/clay nanocompozit c tnh cht c hc cao hn nhiu so vi vt liu polyme
ban u, th hin mt s thng s sau
a. E- modun:
Hnh 1.16. nh TEM ca vt liu PS/clay nanocompozit [15]
(a): vt liu PS/clay nanocompozit dng chn lp
(b) vt liu PS/clay nanocompozit dng tch lp
35
53
y l thng s th hin cng ca vt liu ti thi im bt u ca qu
trnh o bn c l, l c trng tiu biu cho s to thnh vt liu polyme/clay
nanocompozit. Vt liu Nylon 6/clay nanocompozit l loi nanocompozit tch lp,
E-modun ca vt liu ny tng mnh ngay c hm lng cht gia cng thp. Hnh
1.17 m t s ph thuc ca E-modun khi thay i hm lng clay nhit 120oC
i vi vt liu nanocompozit nylon-6 tch lp thu c bng phng php trng hp
in situ e-cprolactam vi s c mt ca MMT ( di trung bnh 1000Ao) v Saponit
( di trung bnh 500Ao) bin tnh bng aminododecanoic axit.
Hnh 1.17: S ph thuc ca E-modun nhit 120oC
vo s thay i hm lng clay
T hnh v trn cho thy, kh nng phn tn ca lp silicat ti tng ca E-
modun trong vt liu c nh hng trc tip ca di thanh clay[61]. Ngoi ra, cn
k n loi axit a vo xc tc cho qu trnh polyme ho. Trong trng hp vt liu
PP/clay nanocompozit, khi thay i hm lng cht bin tnh PP l anhydrit maleic
(AM), cng nh hng ti ln ca E-modun.
b. bn ko t:
i vi cc polyme nht do, qu trnh ch to vt liu nanocompozit dng
chn lp hay dng tch lp th bn ko t ca vt liu u ph thuc mnh vo
Hm lng clay (% )
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54
tng tc gia polyme nn v cht gia cng. Chng hn nh vt liu nylon 6
nanocompozit tch lp, bng nhiu phng php ch to khc nhau [61,102,103] hay
vt liu PMMA nanocompozit [64] u c bn ko t tng, iu c gii
thch do s c mt ca lin kt phn cc (trong PMMA) hay tng tc ion (khi
nylon-6 ghp ln clay) gia polyme v cc lp clay. Nht l i vi vt liu nylon 6
nanocompozit do va c hin tng tch lp clay va c tng tc ion vi clay.
Cn trong trng hp PP/clay nanocompozit[64], bn ko t hu nh
khng hoc tng rt t, l do trong vt liu ny thiu s tng tc gia polyme nn
khng phn cc v cht gia cng c phn cc. Khi c mt ca cht AM bin tnh PP
trong vt liu c s ci thin v bn ko t..
c. dn khi t:
i vi cc vt liu nanocompozit c polyme nn l nha nhit do nh PP,
PMMA, PS dn khi t gim. Ring i vi cc cht nn nh epoxy [105] hay
polyol polyuretan [106] dn khi t li khng gim, i khi cn c hin tng
tng ln nh hnh 1.18 di y.
Hnh 1.18: dn khi t ca vt liu nanocompozit t epoxy
vi cc cht hu c ho khc nhau[64]
Tuy nhin, ring i vi polyme nn l PI khi to vt liu nanocompozit c s tng
ln i vi c bn v dn ko t [113]. Trong trng hp ny, bn v
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55
dn ko t ca vt liu t ti u ti hm lng clay l 5%, khi tip tc tng hm
lng clay ln n 10% th c bn v dn u gim mnh. l do khi hm
lng clay vt qu 5% th dng vt liu to thnh khng dng tch lp na, iu
dn n hin tng tnh cht c hc b gim.
1.4.4.2. bn nhit v tnh cht chng chy
a. bn nhit:
Thng thng bn nhit ca vt liu c nh gi bng phn tch nhit
trng lng (TGA). Khi php phn tch c thc hin trong mi trng kh tr nh:
nit hoc heli, th hin cho qu trnh phn hu khng c s tham gia ca oxi, cn
trong trng hp s dng khng kh, th l qu trnh phn hu vt liu c s tham
gia ca oxi. Nhng nghin cu u tin c cng b l ca A. Blumstein vo nm
1965, trong kho st bn nhit ca PMMA chn lp bng montiorillonit
(MMT). Kt qu cho thy, vi s c mt ca 10% MMT, nhit phn hu ca vt
liu tng ln khong 40-50oC so vi polyme nn. Tip , vo nhng nm 90 ca th
k XX, cng c nhiu tc gi quan tm n bn nhit ca vt liu
nanocompozit. Cc tc gi [30] kho st bn nhit TGA ca vt liu
poly(dimetylsiloxan) khi c 10% clay hu c. So snh vi mu khng c mt clay
hu c cho thy, bn nhit ca vt liu nanocompozit nhit mt 50% trng
lng tng ln 140oC . Cc tc gi cho rng, s d bn nhit vt liu tng ln r rt
nh vy, l do hiu ng cn s bc hi c hnh thnh trong vt liu (ch yu l
silicat vng) gy ra hin tng ny. bn nhit vt liu cng tng ln i vi
mt s vt liu nanocompozit chn lp c to thnh bng polyme ho nh tng t
metyl metacrylat[30], styren[64], v epoxy[76] vi s c mt ca Na-MMT.
Mt yu t khc cng c nh hng khng km n bn nhit ca vt liu
nanocompozit chnh l polyme nn ban u, nh trng hp vt liu poly(imit)
nanocompozit tch lp[65], bn nhit ca n 50% khi lng ch tng 25oC,
trong khi vt liu PDMS nanocompozit tch lp li l 140oC. T cho thy, cu
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56
trc ho hc v c ch phn hu ca polyme nn ban u ng mt vai tr quan trng
i vi bn nhit ca vt liu.
b. Tnh cht chng chy:
Tnh cht chng chy ca vt liu nanocompozit c nghin cu gn y
trong nhm ca Gilman[97] v P. Kiliaris[57]. Phng php thng dng trong nh
gi cc h s lm gim s chy ca vt liu (tc nh nhit, pic gim nhit, nhit
lng chy..) l nng lng Cole. Thng thng, mu c t gn ngun la
(thng 35 kW/m2) v tc nh nhit (HRR) cng nh tc mt khi lng
c ghi nhn nh mt hm s theo thi gian.
Kt qu kho st cho thy hiu ng chng chy r rt nht l s thu nh ca pic
HRR, ngoi ra kh v mui than cng c o li. vt liu nylon-6 nanocompozit
tch lp pic HRR gim 63% so vi pic HRR ca nylon-6 (hnh 1.19). Cc th nghim
o nhit lng Cone cng c tin hnh vi mt vi vt liu nanocompozit khc
nh: Nylon-12 tch lp (2% clay hu c), poly(metylmetacrylat-co-
dodecylmetacrylat) tch lp[37], PS (3%) v PP(2%) dng chn lp, i vi mi loi
vt liu ny, u thu c tn hiu pic HRR gim, trong khi nhit lng chy, khi
v kh CO u khng tng.
Hnh 1.19: Pic HRR ca nylon-6 v nylon-6 nanocompozit tch lp
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57
Nhng s liu trn cho thy, s lm chm ngn la khng xy ra theo mt qu
trnh trong pha kh m thng l s thay i ca qu trnh chy trong pha ngng t.
Cc th nghim thc hin trn cc thit b kh ho bc x [34] cho thy hiu ng
gim chy ca vt liu nanocompozit ch yu c c nh s to thnh ca cc lp
than t s gy vn ca cu trc nanocompozit tch lp hoc chn lp. Cu trc nhiu
lp silicat ny c tc dng nh mt cht cch ly v s chuyn khi lng, t
lm gim s bc hi cc sn phm b phn hu nh thy i vi Nylon-6 cng nh
cc vt liu nanocompozit nhit rn khc [58].
1.4.4.3. Tnh cht che chn
S c mt ca cc lp clay trong vt liu polyme/clay nanocompozit tch lp
c tc dng lm gim s thm kh qua cc mng c to thnh t cc vt liu
ny. o tnh thm kh CO2 i vi vt liu nanocompozit tch lp tng phn polyimit
c thc hin bi Ian v cc cng s [39]. Theo , thm kh tng i Pc/Pp vi:
Pc v Pp l thm kh ca vt liu compozit v polyme ban u. Kt qu cho thy
n c biu din di dng hm theo phn cht n a vo. Thc nghim b
xung cho l thuyt v ch ra rng, chng thm kh ca vt liu ph thuc vo chiu
di, chiu rng cng nh phn % th tch ca cht n a vo trong polyme nn.
Hnh 1.20: Kh nng thm kh CO2 ca PI nanocompozit
T l th tch
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58
Hiu ng chng thm nc i vi vt liu nanocompozit tch lp mt phn
hoc hon ton PI cng c a ra bi nhm tc gi Yano et al., bng vic s dng
clay hu c c chiu di lp khc nhau. Gia thc nghim v l thuyt cng ch ra
rng, khi chiu di thanh clay tng ln, thm tng i ca vt liu gim xung.
1.5. TNH HNH NGHIN CU VT LIU NANOCOMPOZIT T PE V
CHT GIA CNG NANO
Nh bit, PE l mt nha nhit do c s dng rng ri trong i sng
cng nh trong cng nghip, chnh v vy c rt nhiu cc cng trnh nghin cu,
kho st tnh cht vt liu trn c s PE [14,16,17,19,40,48,53,56,83,93]. Gn y,
nn cng nghip vi s xut hin ca cht gia cng c kch thc nano em li
nhiu tnh nng u vit cho sn phm thu c v PE cng khng l ngoi l. Chnh
v vy, trn th gii cng nh ti Vit Nam, c nhiu cng trnh cng b lin quan
n qu trnh ch to v kho st cc tnh cht vt liu PE/clay nanocompozit
[2,3,16,44,54,116].
1.5.1. Nghin cu ch to v kho st tnh cht chng vi khun ca vt liu
nanocompozit t PE/nano bc.
Gn y, nhm cc tc gi Paula A. Zapata(2011) [78] tin hnh ch to
vt liu nanocompozit trn c s PE v nano bc bng phng php trng hp in situ
vi s c mt ca cht n nh axit oleich, vi mc tiu ng dng vt liu ny trong
bao gi thc phm v s dng trong ngnh dc. Kho st cu trc vt liu qua nh
TEM cho thy, vi s c mt ca axit oleic, cc cu t nano bc phn tn kh tt
trong PE nn. Cc kho st c tin hnh vi chng vi khun e- coli cho thy, tc
dng chng vi khun ca vt liu tng ln vi s tng hm lng ca nano bc. Vi
5%nano bc sau 24 gi tip xc loi b ti 99,9% vi khun e-coli trong mu th.
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59
Hnh 1.21 : nh TEM vt liu nanocompozit PE/nanoAg vi
cc hm lng nano bc khc nhau(1,2 v 5%)
Kt qu trn cho thy, to ra c vt liu nanocompozit c tnh chng vi
khun cao. T y, m ra hng ng dng mi cho vt liu nanocompozit trn c s
PE v cht gia cng nano.
1.5.2.Ch to v kho st tnh cht vt liu PE/clay nanocompozit
Nm 2009, N.Tz. Dintcheva v cc cng s [35] kho st tnh cht nhit,
bn oxy ha quang ca vt liu nanocompozit PE/clay hu c. Cc tc gi tin
hnh ch to vt liu trn thit b trn hai trc v mt s mu chn lc trn thit b
trn kn. Hai loi clay hu c thng mi c s dng y l: Closite 15A (CL15)
v Nanofill SE 3000 (NF) v clay cha bin tnh (Na-MMT) c dng lm mu i
chng. Ngoi ra, cc tc gi cn s dng cht tng hp PE ghp anhydric maleic
(PE-g-AM). Cc kho st v s phn tn ca clay hu c trong vt liu c thc
hin bng cc phng php phn tch nh: XRD, TEM, SEM v FTIR. Kt qu kho
st cho thy, vi s c mt ca cht tng hp PE-g-AM, clay hu c thu c c
dng chn lp v tch lp. Kt qu o tnh cht c l ca vt liu nanocompozit
PE/CL15/PE-g-AM, PE/NF/PE-g-AM v cc mu so snh PE/Na-MMT v blend
PE/PE-g-AM cng cho thy: mdun n hi E, bn ko t ca vt liu ch yu
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60
nh hng bi hm lng clay ch khng phi do s c mt ca PE-g-AM, trong khi
dn di tng i ca vt liu li tng nh khi c mt cht tng hp ny.
Hnh 1.22. nh TEM vt liu nanocompozit trn c s LLDPE/CL15 khi
khng (a) v c (b) mt cht tng hp PE-g-AM
Kt qu th nghim oxy ha quang i vi hai loi vt liu nu trn v cc
mu so snh c th hin qua s to thnh v bin i ca nhm cacbonyl (CO)
trong qu trnh oxy ha trn ph hng ngoi (hnh 1.23).
Hnh 1.23. Ph hng ngoi ca vt liu nanocompozit v cc mu so snh
trong qu trnh th nghim oxy ha quang
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Nm 2005, Chungui Zhao v cng s [31] cng tin hnh kho st tnh cht c l,
tnh cht nhit v tnh cht chy ca vt liu nanocompozit HDPE/clay bng phng
php trn hp nng chy.Trong clay c bin tnh bi dioctadexyl
dimetylamonium clorid (DOAc) v (N--trimetoxysilanpropyl) octadexyldimetyl
amonium clorit (JSAc). Clay sau khi c bin tnh bng 2 hp cht hu c c k hiu
ln lt l DM v JS. Tnh cht c l ca vt liu ph thuc vo nhiu yu t [31]
nh: hm lng cht gia cng, s tng tc gia cht gia cng v polyme nn, s
kt dnh gia cht n v cht nn trn b mt phn gii.
Bng 1.5. Tnh cht c l ca PE v vt liu nanocompozit PE/clay
Mu bn ko
t (MPa)
bn un
(MPa)
bn va
p theo
Izod (J/m)
PE 22 1.2 26 1.1 20 4.1
PE/JS5 25 1.4 28 0.8 16 4.6
PE/JS10 27 1.1 33 2.0 16 3.4
PE/JS15 28 1.4 38 1.3 12 2.9
PE/DM5 21 2.0 26 2.1 22 4.5
PE/DM10 23 0.9 31 0.9 16 3.6
PE/DM15 24 1.8 30 1.2 14 3.1
Cc kt qu thu c t bn c l ca vt liu thu c cho thy, khi tng
hm lng khong st, E-modun v bn ko vt liu tng ln nhng bn va p
Izod li gim. Vi khong st JS cho tnh cht c l vt liu tt hn so vi khong st
DM c cng hm lng.
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Kho st tnh cht chy ca vt liu c thc hin theo tiu chun ASTM E
1354 trong nhit lng hnh nn. Kt qu cho thy, c s gim cng pic ta nhit
(HRR) ca vt liu nanocompozit HDPE/JS v HDPE/DM so vi mu PE ban u.
Hay nh pic biu th tc mt trng lng ca vt liu nanocompozit v PE nn
cng cho thy: tc mt trng lng ca PE nhanh hn so vi vt liu
nanocompozit. Qua y, cc tc gi nhn nh rng, s ci thin tnh cht chy ca
vt liu nanocompozit c th l do c hiu ng che chn vt l. Khi c mt 2% clay
bin tnh JS, pic HRR ca vt liu gim ti 54%. Quan st qu trnh chy ca vt
liu nanocompozit v PE ban u, cc tc gi thy rng, chnh s to thnh than c
c t s c mt ca clay c tc dng ci thin tnh cht chy ca vt liu
nanocompozit.
Mt s tc gi khc (o Th Minh v cng s, Hongdian Lu v cng s) [3,
41] thc hin ghp LLDPE vi hp cht silan (vinyltrimetoxysilan), sau ch to
vt liu nanocompozit polyme/clay vi s c mt ca cht khi mo dicumyl peoxit
(DCP) trong thit b th nghim v kho st cu trc v tnh cht nhit ca vt liu thu
c.
Hnh 1.24 nh TEM ca vt liu nanocompozit PE-g-VTMS/clay hu c
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63
Kt qu thu c t nh TEM cho thy, khong st hu c phn tn kh tt
trong nn polyme. Cc cng b trc [101] cng cho thy,vi s c mt trn 3% ca
clay c bin tnh bi C16-(hexadecyl trimetylammonium) hoc C18-(octadecylamin)
khi khng c mt cht tng hp th khong st phn tn khng ng u trong PE.
Trong trng hp ny, s phn tn ng u ca clay trong PE-g-VTMS c
c l do s kt dnh tt gia nn PE v clay v do s c mt ca VTMS vi hai
nhm chc hot ng gp phn lm cho PE d dng chn vo gia cc lp ca
khong st.
Kt qu kho st phn tch nhit TGA hnh 1.25 cho thy, vt liu
nanocompozit PE-g-VTMS/clay c bn nhit cao hn so vi PE ban u v PE-g-
VTMS. Vt liu ny c tc mt trng lng thp nht trong khong nhit t
250-400oC. Nh vy, vic a PE-g-VTMS vo gia cc lp ca clay ci thin
bn oxy ha nhit ca vt liu.
Hnh 1.25. TGA ca PE (A), PE-g-VTMS (B) v PE-g-VTMS/clay (C)
Tc gi Joong-Hee Lee v cc cng s [55] cng tin hnh ch to vt liu
HDPE/clay hu c bng phng php trn hp nng chy vi s c mt ca hai loi
cht tng hp l PE-g-AM v PP-g-AM. Trc tin, clay c bin tnh bi C18-
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(octadecylamin) sau c trn hp vi 2 loi cht tng hp trc khi a vo
ch to vt liu nanocompozit.
Kt qu thu c t ph XRD ca vt liu nanocompozit thu c cho thy, s
c mt ca cht tng hp PP-g-AM lm cho khong st phn tn tt hn so vi PE-
g-AM. Cc kho st tip theo c thc hin vi vt liu nanocompozit trn c s
HDPE/PP-g-AM vi cc hm lng khong st khc nhau (1,3,5,7%). Kt qu kho
st phn tch DSC v TGA cho thy, s c mt ca clay lm tng nh im chuyn
ha thy tinh ca vt liu. Tuy nhin, khi tng hm lng clay, li lm gim nhit
bt u phn hy (Tonset) ca vt liu (bng 1.7). Cc tc gi cng kho st tnh
cht chng thm kh (N2, CO2) ca vt liu thu c. Kt qu cho thy, s c mt ca
clay lm tng kh nng chng thm kh ca vt liu. Vi 7% clay lm gim 23% s
thot kh N2 v 28% s thot kh CO2.
Bng 1.6. Cc thng s phn tch nhit c trng ca nanocompozit HDPE/clay vi
cc hm lng clay khc nhau[55]
Hm lng clay (%)
Nhit chuyn ha thy tinh ( oC)
Nhit bt u phn hy( oC) (Tonset)
1 124,4 426,7
3 124,7 419,3
5 124,9 399,7
7 126,1 395,5
Cng vi vt liu nanocompozit ch to t HDPE, cc tc gi thuc nhm
nghin cu E.M. Araujo et al [20] bin tnh mt loi khong st Braxin vi 4
loi mui amoni khc nhau v 4 loi clay hu c thu c k hiu l: D-OMMT,G-
OMMT, P-OMMT v C-OMMT. Mu vt liu nanocompozit ban u c trn u
trong thit b trn ni 2 trc sau mu c ch to trn my p phun Fluidmec
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200oC. Tnh cht vt liu c kho st bao gm: tnh cht c l, bn va p Izod
v tnh cht chng chy theo phng php UL 94-HB [98].
Kt qu kho st ph XRD vi 4 mu vt liu nanocompozit trn c s HDPE
vi 4 loi clay bin tnh cho thy: vi mu PE/D-OMMT, pic c trng cho khong
cch c bn d001 hu nh khng thay i. iu cho thy, clay phn tn khng tt
trong nn PE v vt liu nanocompozit khng c to ra. Ba loi clay cn li u
phn tn kh tt trong nn PE v to nn vt liu nanocompozit dng chn lp.
Hnh 1.27. nh TEM vt liu nanocompozit HDPE/P-MMT
Hnh 1.26. nh SEM ca clay bin tnh C-OMMT
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Kt qu kho st hnh thi cu trc bng nh TEM ca vt liu nanocompozit
HDPE/P-MMT cho thy, ngoi cu trc dng chn lp ca vt liu
vn cn mt s dng kt t ca khong st P-MMT trong nn PE. Nh vy, vt liu
nanocompozit HDPE/P-MMT thu c dng bn chn lp.
Nm 2007, Sarat K. Swain v cng s [74] kho st nh hng ca sng
siu m n cu trc v tnh cht ca vt liu nanocompozit HDPE/clay. Kt qu
kho st qua ph XRD cho thy, sng siu m c tc dng tch cc r rt i vi qu
trnh chn lp ca PE trong clay: pic d001 ca vt liu tng 50% so vi khong st ban
u. Tnh cht c l, cng nh tnh cht lu bin ca vt liu u tng khi tng hm
lng clay v thay i cng sng siu m.
Hnh 1.28. nh TEM ca vt liu nanocompozit HDPE/clay,
trc (A) v sau khi x l vi sng siu m (B)
.
Cc tc gi cng kho st kh nng thm kh O2 ca vt liu nanocompozit
trc v sau khi chu tc ng ca sng siu m, ch vi 2,5%clay sau qu trnh siu
m c tc dng lm gim kh nng thm kh O2 ti 20%.
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Hnh 1.29. ng i ca qu trnh khuch tn kh trong vt liu
A: vt liu compozit thng thng, B: vt liu nanocompozit polyme/clay
Vit Nam, vic nghin cu ch to vt liu polyme/clay nanocompozit cng
c cc nh khoa hc quan tm nghin cu [2,3,9]. Nm 2003, nhm ti do GS.
Quch ng Triu nghin cu ch to v ng dng hai loi vt liu nanocompozit
epoxy/clay bng phng php khuch tn dng dch v nanocompozit polyamit/clay
bng phng php khuch tn nng chy. Hai loi vt liu ny u c cc tnh cht
u vit hn hn so vi cc vt liu compozit cng loi [8]. TS. o Th Minh v cc
cng s (2005) cng c cng trnh nghin cu ch to vt liu nanocompozit trn
c s polyme nhit do (PE, PVC) v nano-clay ng dng lm cp in bn thi tit
v kh chy. Nhm ti kho st tnh cht c l, tnh cht nhit v kh nng
chng chy ca vt liu nanocompozit thu c. Kt qu kho st cho thy, hai loi
vt liu PE/nano-clay v PVC/nano-clay nanocompozit u t tiu chun lm vt
liu bc dy cp in. Nh vy, cc tc gi trong v ngoi nc c nhng kt qu
nghin cu cho vt liu nanocompozit polyme/clay vi cc polyme nhit do nh:
PP, PE v PVC. Tuy nhin, vic nghin cu tip tc vn l cn thit xt trn 2 gc :
khoa hc v trin khai ng dng.
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CHNG 2. THC NGHIM
2.1 Nguyn liu v ha cht
- PE: Polyetylen mch thng t trng thp (LLDPE), sn phm thng mi ca
Thi Lan, t trng d = 0,9175 g/cm3, ch s chy MFI210/2.16 (g/10 pht) = 7,6.
- PE-g-AM: Polyetylen ghp anhydrit maleic (PE-g-AM) c hm lng AM t
0,5-1%, sn phm ca D n KC 02.DA.04, Vin K thut nhit i.
- Clay: Bentonit ca hng Huaxuechun CP-Trung Quc, khong cch c bn d001
= 1,49 nm, kch thc ht 3-7m.
- Aminopropyltrimetoxysilan (APS): Sn phm thng mi ca hng Merck
(c), tinh khit 99,9%, c cng thc ha hc l: H2N-(CH2)3-Si (OCH3)3
- Vinyltrimetoxysilan (VTMS): Sn phm thng mi ca hng Merck (c),
tinh khit 99,9%, c cng thc ha hc l: CH2 = CH- Si (OCH3)3
- Cht khi mo dicumyl peoxit (DCP): Sn phm thng mi ca hng Merck
(c), tinh khit 99,7%, nhit nng chy Tnc = 39-42oC. Thi gian bn
hy 177oC l 1 pht, hm lng oxy hot ha l 5,9%.
2.2. Bin tnh hu c clay bng APS v VTMS
Clay v hp cht silan (APS hoc VTMS) vi t l 3/1 c a vo bnh cu
3 c c cha 600 ml dung dch etanol/nc cng vi t l 3/1. Hn hp trn c
khuy bng my khuy t nhit 80oC vi tc khuy 30 vng/pht trong 5 gi.
Kt thc phn ng, sn phm c lc v ra nhiu ln bng dung dch etanol/nc
nh trn. Sau , sn phm c sy kh nhit 80oC trong 5 gi v nghin mn.
Sn phm thu c l hai loi clay hu c k hiu l clay-APS v clay-VTMS.
2.3. Ch to v kho st tnh cht vt liu compozit PE/clay
2.4. Ch to vt liu nanocompozit PE/clay hu c bng phng php trn nng
chy
2.4.1. Ch to vt liu nanocompozit PE/clay-APS khi khng v c mt cht tng hp PE-g-AM
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Cc mu: PE, PE/clay-APS (clay-APS: 1-5%) v cc mu PE/PE-g-AM/clay-
APS vi cc t l PE/PE-g-AM/clay-APS l 95/5/3, 90/10/3, 85/15/3 v 80/20/3 c
ch to trong my trn kn Haake (c) 1700C vi tc trc quay 70 vng/pht,
trong 8 pht. Thit b trn c kt ni vi my tnh t quan st c s thay
i nht ca vt liu trong qu trnh trn. Kt thc qu trnh trn, mu c ly ra
v p thnh tm trn thit b TOYOSEIKY 1700C trong thi gian t 2-3 pht vi
lc p 150-220 kg/cm2.
2.4.2. Ch to vt liu nanocompozit PE/clay-VTMS khi khng v c mt cht khi
mo DCP
Quy trnh ch to cc mu: PE, PE/clay-VTMS (clay-VTMS: 1-5%) v cc
mu PE/2%clay-VTMS/DCP vi hm lng DCP thay i t 0,1-0,5% khi lng so
vi PE c ch to tng t nh vi quy trnh to mu phn 2.4.1. Cc mu sau
khi ch to c gi n nh iu kin phng t nht 24 gi trc khi tin hnh xc
nh tnh cht.
2.5. Cc phng php nghin cu
2.5.1. Ph hng ngoi (IR)
Ph hng ngoi IR c o trn my IMPACT 410-Nicolet (M), ti Vin Ha
hc, Vin Khoa hc v Cng ngh Vit Nam. Cc mu clay c p dng vin vi
KBr, cn cc mu vt liu nanocompozit c p thnh mng mng c chiu dy 0,3-
0,5 mm v c o di dng ph hp ph trong vng bc sng t 400- 4000cm-1.
2.5.2. Ph nhiu x tia X (XRD) Khong cch c bn d001 ca clay trc v sau khi bin tnh, cng nh trong
vt liu nanocompozit c kho st qua ph XRD. Cc mu o nhiu x tia X c
tin hnh trn my Siemens D5000 (c), ng pht tia Cu vi bc sng K =
1,54040 Ao, gc qut 2 thay i t 1- 30o. My c t ti phng X-Ray, Vin
Khoa hc vt liu, Vin Khoa hc v Cng ngh Vit Nam.
2.5.3. Phn tch nhit trng lng (TGA)
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Cc mu c o trn thit b phn tch nhit SHIMADZU TGA-50H (Nht
Bn) ti Phng Phn tch nhit, Vin Ha hc, Vin Khoa hc v Cng ngh Vit
Nam. y l phng php phn tch da trn s thay i khi lng ca mu theo s
thay i ca nhit . Phng php ny cho bit: nhit bt u qu trnh phn hy,
nhit m qu trnh phn hy ca mu l ln nht (Tmax) hoc nhit mu b
phn hy 10, 50% ...
iu kin phn tch nhit ca cc mu nh sau:
- Tc nng nhit : 10oC/pht
- Mi trng kho st: khng kh
- Nhit kho st:
+ Vt liu nanocompozit: T nhit mi trng n 700oC
+ Clay v clay bin tnh: T nhit mi trng n 900oC
2.5.4. Knh hin vi in t qut pht x trng (FESEM)
nh FESEM ca cc mu c chp trn my HITACHI S-4800 (Nht Bn) ti
Vin Khoa hc vt liu, Vin Khoa hc v Cng ngh Vit Nam vi phng i t
10.000 n 50.000.
2.5.5. Knh hin vi in t truyn qua (TEM)
Chp nh TEM cc mu vt liu c coi l mt trong nhng bin php hiu qu
nh gi mc phn tn ca cht gia cng kch thc nano trong nn polyme.
Cc mu vt liu c ct lp mng c m v c gn trn epoxy v a vo
bung chp. Cc mu chp TEM c thc hin trn my JEOL JEM 1010 (Nht
Bn) ti Vin V sinh dch t Trung ng.
2.5.6. Kho st tnh cht c hc
Mdun n hi, bn ko t, dn di tng i c o trn my o tnh
cht c hc Zwick Z2.5 (c) ti Vin K thut nhit i, Vin Khoa hc v Cng
ngh Vit Nam, theo tiu chun ASTM D 638 vi tc ko mu 50 mm/pht. Mi
mu o 5 mu ly gi tr trung bnh.
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2.5.7. Kho st bn oxy ha nhit v bn oxy ha quang
Cc mu vt liu sau qu trnh th nghim oxy ha nhit v oxy ha quang c xc
nh h s bn lo ha theo cng thc di y:
Trong : Ki (i= , ) l h s lo ha ca vt liu v bn ko t v dn khi
t.
Cs: tnh cht vt liu sau khi th nghim
CT: tnh cht vt liu trc khi th nghim
2.5.7.1. Kho st bn oxy ha nhit
Cc mu nanocompozit c th nghim oxy ha nhit nhit 100oC v
136oC trong 72 gi trong t sy Memmert (c) c i lu khng kh. Cc mu sau
khi th nghim c ly ra v gi n nh nhit phng trong 24 gi trc khi
xc nh tnh cht c hc. bn oxy ha nhit c xc nh theo phn trm cn li
ca bn ko t v dn di tng i ca mu trc v sau khi th nghim.
2.5.7.2. Kho st bn oxy ha quang
Th nghim oxy ha quang c thc hin trong thit b th nghim kh hu gia
tc UV CON NC-327-2 (M) ti Vin K thut nhit i, Vin Khoa hc v Cng
ngh Vit Nam. Ch th nghim theo tiu chun ASTM D 4587-95: trong 72 gi
vi 6 chu k, mi chu k bao gm 8 gi bc x t ngoi 70oC v 4 gi ngng m
50oC. Cc mu sau khi th nghim c ly ra v gi n nh nhit phng trong
24 gi trc khi xc nh tnh cht c hc. bn oxy ha quang c xc nh
theo phn trm cn li ca bn ko t v dn di tng i ca mu trc v
sau khi th nghim.
2.5.8. Kho st kh nng chng chy ca vt liu
Ki
Cs
CT
=
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Kh nng chng chy ca mu vt liu c th nghim theo tiu chun UL 94
HB (M) ti Vin K thut nhit i, Vin Khoa hc v Cng ngh Vit Nam. y l
phng php thng dng cho cc loi vt liu v c m t nh sau: cc mu c
kch thc 1,25cm x 12,5cm c kp vo gi theo phng nm ngang (hoc
nghing 45o). Trn mu c nh du 2 vch ti cc v tr 2,5 v 10cm. Qu trnh
t mu c thc hin trong 30 giy hoc n khi mu chy n vch 2,5cm th bt
u tnh thi gian chy. Nu mu th nghim chy qu vch 10cm th thi gian chy
c ghi li t vch 2,5 n vch 10cm. Nu mu dng chy trc vch 10cm th
thi gian chy v chiu di ca on mu b ph hy c ghi li. Mu th nghim c
chiu dy di 3 mm s t ch tiu theo UL 94 HB nu c tc chy nh hn 76
mm/pht hoc dng chy trc vch 10cm.
2.5.9. Kho st kh nng chng thm hi nc/axeton
Cc mu vt liu c p di dng mng mng c chiu dy: 50-60 m. Cc
cc ong 50 ml ng nc/axeton c bt kn bng cc mng ny v c cn chnh
xc bng cn phn tch xc nh khi lng mo. Sau nhng thi gian nht nh, cc
