ISSN 0104-6632 Printed in Brazil

www.abeq.org.br/bjche

Vol. 33, No. 04, pp. 945 - 956, October - December, 2016 dx.doi.org/10.1590/0104-6632.20160334s20150172

*To whom correspondence should be addressed

Brazilian Journal of Chemical Engineering

EFFECT OF POLY (N- VINYPYRROLIDONE) ON THE NON-ISOTHERMAL CRYSTALLIZATION

KINETICS AND VISCOELASTIC PROPERTIES OF PVDF FILMS

A. Mashak1*, A. Ghaee2 and F. Ravari3

1Department of Novel Drug Delivery Systems, Iran Polymer and Petrochemical Institute,

P.O. Box: 14965/115, Tehran, Iran. *E-mail: a.mashak@ippi.ac.ir

2Department of Life Science Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box: 143951374, Tehran, Iran.

3Department of Chemistry, Payame Noor University, Tehran 19395-4697, Iran.

(Submitted: March 15, 2015 ; Revised: August 24, 2015 ; Accepted: August 28, 2015)

Abstract - Poly(vinylidene fluoride) (PVDF) and PVDF blends with various molecular weights of poly (N- vinylpyrrolidone) (PVP) films were prepared in dimethyl formamide through the solution casting method. Non-isothermal melt crystallization studies of PVDF films were carried out by cooling the molten samples at different temperatures using differential scanning calorimetry (DSC). The obtained films have been characterized by dynamic mechanical thermal analysis (DMTA). Crystallization kinetics of PVDF films were successfully described by the Jeziorney, Mo and Ziabicki models. The Ozawa equation was found to be invalid for describing the crystallization kinetics. Kinetic parameters such as t1/2, Zc and F(T) indicated that the crystallization rate decreased for PVDF/PVP films as compared to neat PVDF films and was affected by the molecular weight of PVP. The results based on Ziabicki's model revealed that the addition of PVP decreased the ability of PVDF to crystallize under non-isothermal melt crystallization conditions. The activation energy was calculated through Friedman and advanced isoconversional methods. Results showed that the addition of PVP to PVDF films caused an increase in activation energy. By comparing DMTA results of PVDF/PVP blends with neat PVDF films, it could be concluded that blending PVDF with PVP caused an increase in the glass transition temperature (Tg) while the storage modulus was decreased. Keywords: Poly(vinylidene fluoride); Poly (N- vinylpyrrolidone); Crystallization kinetics; Non-isothermal crystallization; Differential scanning calorimetry.

INTRODUCTION

Polyvinylidene fluoride is popular in industrial applications as a semi-crystalline polymer due to favorable properties like good thermal stability, chemical resistance, high mechanical strength and ferro-electricity (Nasir et al., 2007; Sencadas et al., 2010). The crystalline structures of PVDF polymer, according to the chain conformation with trans or gauche linkages, are α, β and γ phases (Nasir et al.,

2007). The crystalline morphology and crystallinity of PVDF are of major importance in various applica-tions. However, the hydrophobic characteristic of PVDF is a limitation in some applications. For ex-ample, membrane fouling caused by hydrophobic interactions results in rapid water flux decline and high energy-consumption, especially when the wastewater contains natural organic matter (NOM), proteins and micro-organisms (Rajabzadeh et al., 2012).

946 A. Mashak, A. Ghaee and F. Ravari

Brazilian Journal of Chemical Engineering

Hydrophobic characteristics of polymers can be altered by polymer blending, that is more effective and widely used in comparison to chemical synthesis procedures (Ma et al., 2008; Li and Xu, 2012; Li et al. 2013). Studies showed that the crystalline phase of PVDF can be changed by blending with amor-phous polymers exhibiting physical interaction with PVDF. Therefore, it is necessary to investigate the crystallization kinetics for optimizing the process conditions and improving the structure-property cor-relation. The main focus has been on the crystalliza-tion behavior of PVDF and its blend in melt crystal-lization processes in the open literature (Lee and Ha, 1998; He et al., 2008; Zhong et al., 2011). Sencadas et al. (2010) studied the isothermal melt crystalliza-tion of PVDF at different crystallization tempera-tures. The Avrami parameters and the Hoffman-Weeks model were discussed to obtain the equilibrium melt-ing temperature. The crystallization and morphologi-cal behavior of PVDF/polyhydroxybutyrate blends were also studied by Liu et al. (2005). They de-scribed a phase diagram by calorimetric measure-ments and reported the Avrami exponent for pure PVDF, which has a value of approximately three. The miscibility behavior of poly(methyl methacry-late) and PVDF was investigated by Fan et al. (2007). They found that the Avrami exponent de-creases with rising crystallization temperature. Mancarella and Martuscelli (1977) also reported that the PVDF Avrami exponent variation was between 2.99 and 4.60 and that the half crystallization time was increased by an increase in crystallization tem-perature. Gradys et al. (2007) studied non-isothermal crystallization of PVDF at ultra high cooling rates. Their results indicated that pure β- phase of PVDF was obtained during the melt- crystallization process at cooling rates above 2000 K/s.

Although, there are some reports in the literature on the crystallization behavior of PVDF, less attention was paid to the non-isothermal crystallization kinet-ics of PVDF/PVP blends. In this study, the effect on PVDF crystallization of PVP with various molecular weights as an amorphous and water soluble polymer was investigated. The PVDF/PVP blend is a miscible system due to the compatibility of the two polymers (Chen and Hong, 2002; Ji et al., 2008; Freire et al., 2012). Dynamic mechanical thermal analysis (DMTA) was used to characterize the dynamic mechanical properties of PVDF films. The Jeziorney, Ozawa, Mo and Ziabicki kinetic models were applied to de-scribe the crystallization behavior of PVDF films. Furthermore, the activation energy of melt crystalliza-tion for sample films was determined from the Freid-man equation and advanced isoconversional method.

MATERIALS AND METHODS

Poly(vinylidene fluoride) (Mw = 530000 gmol-1) was purchased from Sigma-Aldrich (USA). Poly (N- vinylpyrrolidone) (PVP) (K 17, Mw 10,000 gmol-1 and 360000 gmol-1) was provided by Rahavard Tamin Chemical Co. (Iran). N, N-Dimethylformamide (DMF) was obtained from Sigma-Aldrich (USA) and used as solvent. All chemicals were used without further purification. Sample Preparation

PVDF films were prepared using the solvent cast-ing method. Poly(vinylidene fluoride) pellets were dissolved in DMF at 50 °C for 10 h and then poly(N-vinylpyrrolidone) was added at a PVDF: PVP weight ratio of 1:1. The PVDF solution was poured into a flat dish for solvent evaporation at room temperature within an interval of two weeks. The samples were dried further at 50 °C for 8 h to remove the solvent residues. The thicknesses of polymer films were about 150-200 µm. The samples were named neat PVDF, PVDF/PVP1 for PVP with low molecular weight and PVDF/PVP2 for PVP with high molecu-lar weight. Characterizations

The crystallization kinetics of PVDF polymer and the effects of PVP on its crystallization behavior were evaluated using a differential scanning calo-rimeter (DSC) (Polylabe 625, instrument, UK). The weights of all samples were ~5 mg. The samples were heated from room temperature to 200 °C with a 30 °C min-1 heating rate and held for 3 min to eliminate the previous thermal history. Subse-quently, the samples were cooled to 50 °C at prede-termined rates. The non-isothermal process included melt crystallization at different cooling rates: 2.5, 5, 10 and 20 °C min-1, while exothermal curves of heat flow were recorded as a function of tempera-ture and the experiments carried out under nitrogen atmosphere. FTIR spectra were obtained by a FTIR instrument (Bruker, model Equinox) in the 600–3500 cm-1 wave number range. Dynamic mechani-cal thermal analyses of the samples were carried out using a DMA, (Tritec 2000 machin) under the bending mode at a frequency of 0.1 Hz. The tem-perature range was from -100 to 100 °C at a rate of 5 °C min-1. The dried polymer films were cut into approximately 2.5×1×0.15 cm3 rectangles. The am-plitude was set to be within the linear viscoelastic regime.

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PVDF/PVP

PVDF/PVP

FTIR Spectr

For a bettePVDF and Proscopy was

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Hong (2002).

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December, 2016

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ith the coolmolecules to nditions. Thug rate is the

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Non-Isotherm

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Several mehe non-isoth

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with crystalliz

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Fig. 5 showswith crystalliVP films. Aeristic sigmoe to the sphef crystallizatin completiong rates.

elative crystad PVDF/PVP

mal Crystall

rami Model

ethods have hermal crystavrami equatioes of isotherhe relative czation time (

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been develoallization kion was used rmal kineticscrystallinity t) as follows

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be expressed

2008).The hosformed intoions of relatfor neat PV

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( ) 1 exp(X t = −

here k and nd the Avram08). In actual co

antly during e parametersgs. Therefore

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=

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ue to more iner chains.

( )nkt−

n are the crymi exponent

onditions, thenon-isothermn and k hav

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e modified crte constant ocess (Yu et

nd Zhang, 20e 2. Zc is in

The modifiedoaded PVDFtrast to that

llization halfat which the

t1/2 for non-ed from Equarmal crystalle 2. Generalprocesses. T

oling rates hmes for bo

ver, the valur in comparis

the data shoeters Zc and twas reducedarlier, this ef

olecular mobh PVP in the

crystallizatiy PVP withteractions of

rystallizationt, respective

e temperaturemal crystallive different p

considered constants b

ified equatio

rystallizationof the non-isoal., 2009; B

013). The vancreased by d crystallizaF films decrof neat PVD

f-time (t1/2), e extent of -isothermal ation 6 and lization ratesally, short t1/2The t1/2 valuehave shorter oth neat anues of t1/2 foson to those

ow that PVP t1/2. Thus, thd upon blendffect was caubility due toe molten station rate of Ph higher molf the PVDF a

(4

n rate constaely (Ji et a

e changes coization; hencphysical meathe correctio

by introducinn is expresse

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n rate constaothermal cry

Bahader et aalues of Zc aincreasing th

ation rate coeased to somDF, at variou

is defined crystallizatiocrystallizatioused to eval

s. The data a2 means fastes indicate thcrystallizatiod PVDF/PVor neat PVDof PVDF/PV

(6

influenced thhe PVDF cryding with PVused by reduo stronger ite. The resulPVDF was alecular weigand PVP pol

4)

ant al.,

on-ce, an-on ng ed

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ant ys-al., are he n-

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The Ozawpproaches foroposed by e978). This mhe non-isotheided into smion is express

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igure 6.

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K Tφ

⎡ ⎤−⎢ ⎥⎣ ⎦

( )) ln (X t K⎤=⎦

and m are thnent, respecs on the dim

( )ln 1 ( )X t−

ypyrrolidone) on t

zilian Journal of

rystallizatio

Zc (°Cmin-1)

0.88 0.97 1.12 1.12 0.23 0.59 0.98 1.05 0.24 0.58 0.88 0.95

one of the mormal crystall

e Avrami Eqused on the aallization pro

mal steps. Th

( ) lnT m φ−

he cooling fuctively. Themension of c)⎤⎦ versus ln

the Non-Isotherm

Chemical Engine

n kinetic pa

t1/2(min)

0.98 0.91 0.58 0.35 2.99 1.93 0.93 0.66 4.01 2.69 1.56 1.25

ost used kinelization proceuation (Jeziorassumption tocess can be e Ozawa Eq

unction and Ozawa exp

crystal growφ are shown

mal Crystallization

eering Vol. 33, N

arameters of

Tmax (°C)

135.1 134.7 132.0 127.0 120.9 115.8 109.7 104.8 103.4

99.4 93.9 88.1

etic ess, rny, that di-

qua-

(7)

(8)

the po-

wth. n in

FigPV

corwisatkinthaingsec20 CoM

JezmaIn maleaQitheX(

n Kinetics and Vi

No. 04, pp. 945 -

f neat PVDF

(dX(t)/dt)max(s-1)

0.014 0.019 0.030 0.042 0.008 0.010 0.017 0.027 0.003 0.005 0.008 0.010

gure 6: TheVDF/PVP1 (b

It can be serrelations. Cith temperatutisfactory fornetics of PVDat the Ozawag the crystallcondary crys09).

ombined Avodel)

It is obvioziorny modiary stages oorder to find

al crystallizaagues suggesiu et al., 200e Avrami andt):

iscoelastic Proper

956, October - D

F and PVDF

Dφ (°C)

2.69 3.9

5.01 6.88 6.3

6.89 8.61 10.47 11.8 11.2 14.9 25.1

e Ozawa plob) films.

een that theshanges in slo

ure. Thus, thr the descripDF films. Soa model canlization kinestallization (

vrami and

ous that the ification couf non-isothe

d a method toation processsted a new m

00). This metd Ozawa Equ

erties of PVDF Fi

December, 2016

F/PVP films.

Gz,φ (°C min-1)

2.53 4.95 9.69

18.83 2.33 4.74 9.50

18.04 2.41 4.15 7.64

17.30

ots of neat P

se figures haopes indicate

he Ozawa mption of the ome authors

nnot be applietics of polym(Ozawa, 197

Ozawa Eq

Avrami anuld only desermal melt co describe ths exactly, Mmethod (Liuthod is the cuations at a

lms 9

Gz

1.01 0.99 0.96 0.94 0.93 0.94 0.95 0.90 0.96 0.83 0.76 0.86

PVDF (a) an

ave poor linee that m variethod was ncrystallizatiohave declare

ied for modemers that hav71; Yu. et a

quations (M

alysis and iscribe the prcrystallizatiohe non-isotheo and his co

u et al., 199combination given value

951

nd

ear ies not on ed el-ve

al.,

Mo

its ri-

on. er-ol-97; of of

95

ln

wcoddyothisPbli Tm

Fan

52

( )n ln F Tφ =

where ( )F T =ooling rate aefinite physiegree of cryield a linear f crystallinityhe Mo modesothermal pr

PVDF/PVP2 e calculated ines. The kin

Table 3: Thmodel.

Sample Neat PVDF

PVDF/PVP1

PVDF/PVP2

Figure 7: Plond PVDF/PV

) ln tα−

( ) / tK T Z= ⎡ ⎤⎣ ⎦and α is theical and pra

ystallinity, threlationship y, as shown iel was succesrocess of neafilms. The vfrom the slo

netic paramet

he kinetic p

X(t) % 20 40 50 80 20 40 50 80 20 40 50 80

ots of ln φ veVP1 (b) films

1m refers to

e ratio of n toactical meanihe plots of l

for a certainin Fig. 7. It cssful in descat PVDF, PVvalues of αope and the ters are listed

parameters

α 0.58 1.03 1.20 1.79 1.31 1.37 1.38 1.42 1.63 1.75 1.65 1.67

ersus ln t fors.

A. Mash

Brazilian Jou

the value of o m. F(T) haing. At a givnφ versus l

n relative degcan be seen tcribing the nVDF/PVP1 aα and F(T) c

intercept of d in Table 3.

from the M

F(T) 5.31 5.73 6.09 7.41 6.75 9.58 11.0

17.98 12

22.9 27.32

47.7

r neat PVDF

hak, A. Ghaee an

urnal of Chemica

(9)

the as a ven ln t

gree that

non-and can the

Mo

(a)

PVshocryingtheX(cryhigaccfoufilmpar An

thelizfunpofol dX

whexp

ZK

whlizTmcryisomeindtio

ZG

cryisocanfuneac

ZG

nd F. Ravari

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The values VDF and 1.3ow that F(T)ystallinity. Og PVP reveae values achit) values. Siystallization gher F(T) vacordance wiund that F(Tms. This is rameters.

nalysis Base

Ziabicki deermal crystalzation progrenction (Ziablymers in Zillowing equa

( ) (ZX t K Tdt

=

here Kz(T), tpressed by:

,m( )Z ZT K=

here Tmax, Kzzation rate temax and the wystallization okinetic apprer crystallizadex), Gz ,wason (11) over t

(m

g

TZ Z

TK T

°

= ∫The Gz para

ystalline polyothermal cryn be replacenction of thch cooling ra

, (m

g

TZ

TdXϕ

°

= ∫

of α vary 1 to 1.7 for P) increased up

On the other hled higher Fieved for neaince F(T) ref

process, at alues for PVPith slower cT) values arealso in agre

d on Ziabick

veloped anollization kine

ess and crystaicki, 1996). abicki's mod

ation (first or

)[1 ( )]T X t−

he crystalliz

max exp 4ln⎡−⎢⎣

z,max and D aemperature,

width at half-rate functio

roximation, ation abilitys obtained bythe crystalliz

) 1.064T dT ≈

ameter expreymer to crys

ystallization sd in Equatio

he relative cate study as f

/ ) 1X dT dTϕ ≈

from 1.62 toPVDF/PVP fupon increasihand, PVDF

F(T) values aat PVDF filmflects the dit similar X(P loaded PVcrystallizatiore higher foreement with

ki Model

other approacetics related tallization ratCrystallizati

del can be derder kinetics)

zation rate fu

max2

( )n2 T TD−

are the maxthe crystalli

-height meason, respectivthe semi-cry

y (kinetic cy the integra

zation range:

,max4 .ZK D

esses the abistallize. In thstudies usin

on (12) with crystallinity, follows:

1.064( /dX dT

o 2.07 for nefilms. The dang the relativfilms contai

as compared ms at the samfficulty of tht) values, th

VDF films is on rates. It r PVDF/PVPh other kinet

ch for non-isto the crystate-temperatuion kinetics escribed by th):

(10

unction, can b

2 ⎤⎥⎦

(1

ximum crystaization rate sured from thvely. With thystalline polrystallizabiliation of Equ

(12

lity of a semhe case of nog DSC, KZ(the derivativ(dX/dT)φ, f

,max)T Dϕ ϕ (13

eat ata ve in-to

me he he in is

P2 tic

so-al-ure of he

0)

be

1)

al-at he he ly-ity ua-

2)

mi-n-T) ve for

3)

wcr(dinnGpliPTcrvPspPPta E

anvgetclothcoinu F

(M

ln

wrareEgbeqca

erPthin

Effect

where (dX/dTrystallizationdX/dT)φ funndex for an etic crystalli

Gz,α normalizaphol et al., ization kineti

PVP films baTmax decreasereased with alues of Gz

PVDF/PVP2 pectively. Th

PVP films shPVDF to crysallization con

Effective Act

Several mnd Friedmanation energyer, 1956; Vyat al., 2013)losely relaterder to calche effective onversional ntegral isocosed.

Friedman Eq

The FriedMa et al., 20

(

( )nX t

dX tdt

⎛ ⎞⎜ ⎟⎝ ⎠

where dX(t)/date as a funelative crysta

EX(t) the effeciven value oy plotting dXqual to -EX(tan be calcula

Fig. 8 illurgy as a fun

PVDF and PVhe results, tncreasing the

of Poly (N- Viny

Braz

T)φ,max, Dφ an rate, the w

nction and tarbitrary cooizability inde

zation with 2004). Tabl

ics parameterased on Ziabed, while (dX

increasing for neat PVfilms were

he reduction hows that PVstallize undenditions.

tivation Ene

methods suchn methods ary for the crysazovkin, 200). In fact, td to the relaulate approxactivation emethod of F

onversional m

quation

dman Equatio11; Friedman

)tan

tcons t=

dt is the innction of timallinity (X(t))ctive energy of X(t). A strX(t)/dt versust)/R. Thus, thated from the

ustrates plotsnction of relVP loaded PVthe activatioe relative cr

ypyrrolidone) on t

zilian Journal of

and Gz,φ are width at halthe kinetic oling rate. Tex, Gz, can φ (i.e., Gz e 2 summarirs of neat PVicki's model

dX/dT)φ,max, Dcooling rate

VDF and PV1.006, 0.933of the Gz va

VP decreasedr non-isothe

ergy

h as Kissingre used to evstallization p02; Friedmanthe activatioative crystallximately relienergy, the dFriedman anmethod of V

on is expresn, 1964):

( )

( )

X t

X t

ERT

−

nstantaneous me (t) for a

), R is the gabarrier of thraight line cs 1/TX(t). Thehe activatione slope of thes of effectivelative crystaVDF sampleon energy irystallinity,

the Non-Isotherm

Chemical Engine

the maximlf-height of crystallizabi

The Ziabicki be obtained = Gz,φ/φ) (Sizes the crys

VDF and PVD. The values

Dφ and Gz,φe. The averaVDF/PVP1 a3 and 0.835, alue for PVDd the abilityrmal melt cr

ger, Vyazovvaluate the aprocess (Kissn, 1964; Omron energy winity degree.iable valuesdifferential id the advanc

Vyazovkin w

ssed as follo

(1

crystallizatgiven value

as constant, ahe process focan be obtain slope of plon energy (EXe straight linee activation allinity for nes. Accordingincreased upsuggesting t

mal Crystallization

eering Vol. 33, N

mum the lity ki-by

Su-stal-DF/ s of in-

age and re-

DF/ y of rys-

vkin acti-sin-rani was . In

s of iso-ced

were

ows

14)

tion e of and or a ned

ot is EX(t))

e. en-

neat g to pon that

theincexpfrosloobvarPVcaupo

FigfunPV Ad

actto acctheThbe appfinmathenoenoplinprewasys

Φ

wh

aE

n Kinetics and Vi

No. 04, pp. 945 -

e crystallizatcrease in relpect that tra

om the equiliowed down served that tried in the

VDF/PVP1< used a delay lymer.

gure 8: Plonction of rel

VDF/PVP film

dvanced Isoc

It is notewotivation enerreliably pre

curacy of sue accuracy hus, errors in

minimized.proximation

nal plots yieations undene activation n-linear proergy by theed. An adv

near) was deesent study, as applied tostem using th

1

( )n n

ai j

E= ≠

=∑∑

here φ is th

a is the ac

iscoelastic Proper

956, October - D

tion becomeative crystalansmission oibrium melt tas crystallizthe calculatee followingPVDF/PVP2in the crysta

ts of effectivlative crystalms using the

conversiona

orthy that thrgy on relativdict the beh

uch predictioof calculatin

n computing tOne of the ss intentionalllding the aciably induceenergies. To

ocedure for e isoconversvanced isocoescribed by

a non-lineathe dynamic

he following

,

,

( , )( , )

na a i

a a ji

I E TI E T

φ

≠∑

he cooling rativation ene

erties of PVDF Fi

December, 2016

es more diffllinity. Indeeof the polymto the growt

zation proceeed activation g manner: 2 films, indicallization pro

ive activationllinity for ne

e Friedman e

al Method

he sole depeve crystallinihavior of a sons obviouslng the activthe activatiosources of thlly used to dectivation eneed an error ino resolve thcomputing

sional methoonversional Vyazovkin (

ar isoconversc DSC data

g equation:

)j

i

φφ

ate, T is theergy, i, j ar

lms 9

fficult with aed, one shoumer segmenh front will beds. It is alenergy valuneat PVDF

cating that PVocess of PVD

n energy as eat PVDF anquation.

endence of thity is sufficiesubstance. Thly depends ovation energ

on energy muhese errors aerive the lineergy. Approxn the values his problem,the activatio

od was devemethod (no(1997). In thsional methoof neat PVD

(15

e temperaturre the ordin

953

an uld nts be so

ues F< VP DF

a

nd

he ent he on gy. ust are ear xi-of a

on el-

on-he od

DF

5)

re,nal

95

nrapEInma

I

I

an

P

Eapthvob

FfuPm

ovnta

54

umbers of Dates. The acarticular con

aE at which tn Equation (

mined by the l., 1977) giv

0

( , )T

aI E Tα

= ∫

( ),aEI E T ⎛= ⎜

⎝

nd

( ) (expP x

x−

=

Each valuaE dependenc

pplied the shermal and nersional plotbtained from

Figure 9: Plounction of re

PVDF/PVP fimethod.

The non-if PVDF andarious coolineat PVDF, Pallization ab

DSC runs perctivation enenversion levthe ( )tΦ fun(12) the temp

Senum-Yanen as:

exp( )aE dTRT

α

( )aE P xR⎞⎟⎠

) 3

4 20x x

x x⎛− +⎜⎜ +⎝

ue of X(t) wace. The advansame compunon-isothermt trends in F

m the Friedm

ots of effectelative crystailms using th

CONCL

isothermal md its blends ng rates usin

PVDF/PVP bility due to

rformed at dergy can be

vel by findinnction has a mperature inte

ng approxima

T

2

3 218 88

120 24x x

x+ + ++ +

as minimizenced isoconvutational algomal DSC datFig. 9 are san method.

tive activatioallinity for n

he advanced i

LUSIONS

melt crystalliwith PVP w

ng DSC. As blends exhibi

the tendenc

A. Mash

Brazilian Jou

ifferent coole found at ang the valueminimum valegral was detation (Senum

(1

(1

9640 120x

⎞+⎟⎟+ ⎠

(

d to obtain ersional methorithm for ita. The isoc

similar to th

on energy aneat PVDF aisoconversio

ization kinetwere studiedcompared w

it reduced crcy of PVDF

hak, A. Ghaee an

urnal of Chemica

ling any

e of lue. ter-

m et

16)

17)

18)

the hod iso-on-

hose

as a and

onal

tics d at with rys-F to

inttwatoPVwafouTgJezdebe invKicalPVafftioPVFreThPVcon

Ba

Ba

Bi

Ch

Fa

Fre

nd F. Ravari

al Engineering

teract with ween the hydoms of the cVP on the gas also evaluund that PVD

values in cziorny, Mo scribe the crsuccessful.

valid for deinetic paraml models sh

VDF decreasfected by theon energies oVDF/PVP bleidman and

he higher vVDF/PVP blensistent with

adia, J. D., A., Ribes-Gmal Analystion of Polyand InterfaJyotishkumCo. KGaA,

ahader, A., Glization kincarbon nanliquid. Mac

anchi, O., Mrigaray, S. Melt crystameric silsestions. J. No

hen, N. P. andand compoPVP blend.

an, W., Zhenbehavior inand poly(vitopology ofPolym. Sci.

eire, E., BiaE. C., FortePVDF/PMMshear mixe(2012).

PVP througdrogen atomcarbonyl grouglass transitiuated by DMDF films cocomparison tand ZiabickrystallizationThe Ozawa

escribing theeters obtaine

howed that tsed in the pe molecular wof melt cryslends were

advanced value of thends comparh the lower ra

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Effect of Poly (N- Vinypyrrolidone) on the Non-Isothermal Crystallization Kinetics and Viscoelastic Properties of PVDF Films 955

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