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Wood Core Shell Structures for use in
Wood Plastic Composites
Armando McDonaldSmith Sundar
WPC UtilizationOver 70 firms in the US & Canada produced WPC in 2002 worth $1.03 billionMarket had grown rapidly & dominated by the decking marketSpeculated growth -$1.95 billion by 2006 (Plastic news)New opportunities for WPC for semi-structural applications
Objectives of study
Create a high-performance WPC materials:
1. Modify the wood surface to create core-shell like structures to reinforce WPC
Modify surface with an alkyl substituted isocyanate
Improve coupling & therefore performance
Project overview
Wood size reduction
and screening
Synthesis of modified Isocynates
Coupling ofmodified
isocynates towood
Compounding rheology
&Material
evaluation
Technologytransfer &
Commercialapplication
Current research
Avg 110 umAvg 109 um
Avg 33 um
Avg 29 umAvg 25 um
0
10
20
30
40
50
Avg 110 um Avg 109 um Avg 33 um Avg 29 um Avg 25 um
% o
f Tot
al W
eigh
t
100 mesh -100+200 -200+300 -300+400 >400
Fiber generation
Commercial maple flour (100#)Ball milledScreened
200-300#Particle analysis
<
Original Screened fraction
Wood modification strategy
Wood micro fiber
Wood micro fiber
Plastic chains
Wood micro fiber
Chemical approaches
1. Synthesize aliphatic isocyanates which can couple to wood
2. Activate wood with a diisocyanate which can then couple to an aliphatic alcohol
3. Activate wood with a diisocyanate which can then couple to an aliphatic amine
Approach 1
OCN-R-NCO
Woodfiber
-OH
R’ = C2, C8, C12, C18
Woodfiber
-O-CO-NH-R-NH-CO-O-R’
= C18H37OH
= polyethylene
R’OHOCN-R-NH-CO-O-R’
OH
n
(MDI)
1: Aliphatic isocyanate synthesis
Do we have the correct chemistry?Need to derivatize the isocyanategroup with dibutyl-amine (DBA)Separate compounds (3) by HPLC
OCN-R-NCO R’OH OCN-R-NH-CO-O-R’
AU
0.00
1.00
2.00
3.00
Minutes2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00
C2-MDI-C2C2-MDI-DBADBA-MDI-DBA
HPLC chromatogram
(MDI)
1: Aliphatic isocyanate synthesisIsolate/collect HPLC peaksCharacterize each peak by electrospray-MS
+ve psuedomolecular ions (M-H+ / M-Na+)
M-Na+DBA-MDI-C2 M-H+
1. Wood modification
300# maple (extr. free) dispersed in tolueneAdd OCN-R-NH-CO-O-R’ & react for 24-72 hMonitored reaction by TLC as DBA derivativesWashed & dried
63295137Weight gain (%)
C18H37OHC12H25OHC8H17OHC2H5OHFatty alcohol
717.
8975
0.2681
6.91
1055
.11
1074
.51
1103
.75
1163
.73
1235
.90
1310
.72
1412
.79
1469
.35
1510
.33
1533
.66
1593
.55
1702
.41
2850
.91
2918
.99
3324
.65
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
%Tr
ansm
ittan
ce
500 1000 1500 2000 2500 3000 3500 4000 Wavenumbers (cm-1)
897.
07
1033
.47
1233
.76
1371
.15
1421
.39
1504
.57
1593
.46
1735
.91
3382
.60
7 0
7 2
7 4
7 6
7 8
8 0
8 2
8 4
8 6
8 8
9 0
9 2
9 4
9 6
%Tr
ansm
ittan
ce
5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0 4 0 0 0 W a v e n u m b e r s ( c m - 1 )
1. FTIR spectroscopy
C=O
traceNCO
-CH2-MDI-C2-modified wood
Extractives free wood
N-H
1. Compounding
Haake torque rheometer163°C, 35rpm, 5 min0-50% wood (60g)HDPE (EquistarLB01000)
0
1 0
2 0
3 0
4 0
0 1 2 3 4 5 6
T im e ( m in )
Torq
ue (N
m)
C 2C 8C 1 2C 1 8c o n t r o l
1. Molding & tensile propertiesTensile specimens were injection molded from compounded blends (Dynisco LMM)Tensile testing
Instron 5500RASTM 1708-02a 1 mm/min
Improvement in tensile strength for some modified fibers
C8 & C18 at 30% woodC2 at 50% wood 0
5
10
15
20
25
30
c2 c8 c12 c18 Control
Tens
ile S
tren
gth
(Mpa
)
10% Wood loading 30% Wood loading 50% Wood loading
1. Thermal analysis
Mettler Toledo DSC 10oC/min +/- ramps Wood modification increased % crystallizationHowever, No trends were observed between crystallinity & tensile properties
30% WF
0
10
20
30
40
50
Control C2 C8 C12 C18
% C
ryst
allin
ity
WPC, 30% wood content
Approaches 2 & 3
OCN-R-NCOWoodfiber
-OH Woodfiber
-O-CO-NH-R-NCO
C18H37NH2
Woodfiber
-O-CO-NH-R-NH-CO-NH-C18H37 3
2Woodfiber
-O-CO-NH-R-NH-CO-O-R’
R’OH R’ = C2H5, C8H17, C12H25, C18H37
2 & 3. Wood modification300# maple (extr. free) dispersed in tolueneAdd MDI (or TDI) & react for 24-72 hDecant solvent Add alcohol (or amine) & react for 24-72 hWashed & dried
60
C18H37NH-MDI
43
C18H37O-MDI
62335340Weight gain (%)
C18H37NH-TDI
C12H25O-MDI
C8H17O-MDI
C2H5O-MDI
Alkyl grp
2 & 3. FTIR spectroscopy
-CH2-
TDI-ODA modified wood
720.
76
769.
6181
6.4
385
0.76
1018
.83
1057
.2411
08.1
7
1231
.33
1310
.26
1412
.95
1467
.23
1511
.40
1534
.12
1594
.46
1648
.51
1697
.38
2852
.21
2920
.91
2952
.57
3313
.36
7 8
7 9
8 0
8 1
8 2
8 3
8 4
8 5
8 6
8 7
8 8
8 9
9 0
9 1
9 2
9 3
9 4
9 5
9 6
%Tr
ansm
ittan
ce
5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0 4 0 0 0 W a v e n u m b e r s ( c m - 1 )
C=O
traceNCO
-CH2-
MDI-C2H5OHmodified wood
N-H
N-H3
2
2 & 3. Compounding
0
1 0
2 0
3 0
4 0
0 1 2 3 4 5 6
T im e (m in )
Torq
ue (N
m)
C 2C 8C 1 2C 1 8c o n tr o l
3
2
0
1 0
2 0
3 0
4 0
0 1 2 3 4 5 6T i m e M in
Torq
ue(N
m)
T D IM D IC o n t r o l
2 & 3. Tensile results WPC from C2 & C18fiber gave strength improvements at 50% wood content
WPC from TDI-C18fiber gave strength improvements
0
5
10
15
20
25
30
Control MDI-ODA TDI-ODA
Tens
ile s
tren
gth
(MPa
)
10%WF 30%WF 50%WF
0
5
10
15
20
25
30
Control C2 C8 C12 C18
Tens
ile s
tren
gth
(MPa
)
10%WF 30%WF 50%WF
2 & 3. Thermal analysis
Observed and increase in HDPE crystallinity due to wood modification
However, No trends were observed between crystallinity & tensile properties
0
10
20
30
40
Control C2 C8 C12 C18 MDI-ODA
TDI-ODA
HD
PE
Cry
stal
linity
(%)
WPC, 30% wood content
2 & 3. Melt Flow
MFI measured10kg, 190oC, 300s
MFR decreased on wood modification
Especially the C8modified fiber
Similar trend observed in torque rheometry
WPC, 30% wood content
0
1
2
3
4
5
6
Control C2 C8 C12 C18 TDI-ODA MDI-ODA
MFR
(g/1
0 m
in)
Comparison between approaches
Approach 1 takes longer to prepare modified fiber
Tensile properties were generally higher from fiber prepared from approach 1
0
5
10
15
20
25
30
Control C2 C8 C12 C18
Tens
ile s
tren
gth
(MPa
)
Approach-1 Approach-2
0.0
0.5
1.0
1.5
2.0
Control C2 C8 C12 C18
Tens
ile m
odul
us (G
Pa)
Approach-1 Approach-2
Conclusions
Wood surface modification has a positive effect on:
Improved compoundabilityReduced melt viscositySlight improvement in tensile strengthApproach 1 gave better props.Approach 2 & 3 more adaptable for an industrial process
Outcomes:Lower melt viscosities suitable for injection molding applicationsHigher wood loadings achievable at the same melt viscosity
Ongoing work:Extrusion trialsDMTA analysisRheological studies WPC morphology (microscopy)Wood fiber surface energetics & chemistryWater adsorption trials
Questions?
Acknowledgements:Lance Gallagher
Drs. Michael Wolcott, Karl Englund and Tieqi Li, WMEL, WSU
Funding provided by USDA CREES-NRI grant #2002-3732