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
Brazilian Journal
of Chemical
Engineering
EFFECT OF POLY (N- VINYPYRROLIDONE) ON
THE NON-ISOTHERMAL CRYSTALLIZATION
KINETICS AND VISCOELASTIC PROPERTIES OF
PVDF FILMS
A. Mashak
1*, A. Ghaee
2and F. Ravari
31
Department of Novel Drug Delivery Systems, Iran Polymer and Petrochemical Institute, P.O. Box: 14965/115, Tehran, Iran.
*
E-mail: a.mashak@ippi.ac.ir
2
Department of Life Science Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box: 143951374, Tehran, Iran.
3
Department 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, and phases (Nasir et al.,
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 crystallizacrystalliza-tion 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 - 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
N
p g m li ra d
o ou h sh P cu fi m
sh an P si in (t fr ta v tw M
In (Δ
F b
RE
Non-isotherm
Crystalliza olymers was lass transiti melting point ine polymer ates in such ue to the dilu
Non-isothe f neat PVDF us cooling ra eating rate a hown in Figu PVP2 are pre urves of nea ilms (Fig. 1 mained consta The meltin howed the fu nd 145 °C fo PVP2 films, r ingle endoth ng run. How that is, 2.5 ° ront of the m allization of
arious coolin wo melting p Ma et al. (201 The data p n this table
ΔHc), the on
Figure 1: The ehaviors at a
ESULTS AND
mal Crystall
ation in misc s limited to ion tempera t. In this stud was blended blends were ution of crys ermal melt c F films and ates and melt
after non-iso ure 1. All ex esented in T at PVDF, PV
1), the temp ant during th ng behavior usion endoth or neat PVD respectively. hermal meltin wever, the pea °C min-1) sh melting. It cou
PVDF durin ng rate setti peaks. Simil 11).
presented in e, the total nset (Tcon), pe
e DSC curves a heating rate
D DISCUSS
lization Beh
cible blends temperature ature and th dy, PVDF as
d with PVP. e different fro tallizable ch crystallizatio PVDF/PVP ting behavior othermal cry xperimental d Table 1. Fro
DF/PVP1 an perature pea he heating pr
of crystalliz herms to be a DF, PVDF/PV
. As can be ng during th ak at the low howed a sm
uld be relate ng the heatin ings does no
ar results we
Fig. 1 are li crystallizat eak (TcP) and
s of non-isoth s of 10 °C m
SION
avior
similar to p es between he equilibri a semi-cryst Crystallizat om pure PV ain.
on thermogra blends at va rs at 10 °C m ystallization data for PVD om the melt nd PVDF/PV ak position
ocess. ed PVDF fil around 160, 1 VP1 and PVD
seen, there i he second he wer heating r mall shoulder ed to the recr ng process sin
ot influence ere obtained
sted in Table tion enthalp d end (Tcf) cr
hermal crysta min-1 after crys
pure the ium tal-tion VDF
ams ari-min-1 are DF/ ting VP2
re-lms 155 DF/ is a eat-rate r in
rys-nce the d by
e 1. pies
rys-tal Th tur
gan rat tio the to
et
tem
Tcf ne ing de pre ing
wi liz inf
ΔH
in rel an
en exp PV tio car PV an (C res
allization at d stallization (b
llization tem he results sho
res for the sa It can be in nize and for te. On the ot on of the chai e cooling rat initiate cryst
al., 2007). A mperatures (
f) of PVDF/P at PVDF film g higher m
crease more esence of PV g of the cryst
It can be s ith an increas zation enthalp
fluenced by
Hc decreased comparison lated to redu
d a lower de Based on t ce on the cry plained by VDF and PV ons. The hy
rbonyl group VDF due to
d the elect hen and Ho stricted move
different cool b and d) of n
peratures are owed that TcP amples as the nferred that t rm stable nu ther hand, at
in segments te; so, more tallization (B According to
(including th PVP sample ms. The TcP
olecular we than for PV VP in the PV tallization pe een that the se in the cool pies of neat
cooling rate d significantl
with neat P ction in the a gree of perfe he results, P ystallinity of
interaction VP through h
drogen bond p of PVP an
the acidity o tronegativity ong, 2002). ement of the
ling rates (a a eat PVDF an
re shown for P
shifted to l e cooling rate
the PVDF m uclei at a s t high coolin of PVDF co supercoolin Bianchi et al
o Fig. 1, the he values of es are lower
values for P eight PVP ( VDF/PVP1. In VDF film lea
eaks.
e values of Δ ling rate. Th
PVDF films e. However, ly for PVDF PVDF films. amount of cr ection of the PVP has a n f PVDF film of function hydrogen bo nding occurs nd the methy of PVDF hy y of PVP o This interac e PVDF chain
and c) and th nd PVDF/PV
r PVDF film ower temper e increased. molecules reo
lower coolin g rate the m ould not follo ng was neede
., 2014; Xion crystallizatio f Tcon, TcP an than those PVDF contai (PVDF/PVP n addition, th ds to a wide
ΔHc decrease he total crysta s were slight , the value F/ PVP blen . This may b rystals forme
crystals. negative infl ms. This can b
nal groups onding intera s between th ylene group ydrogen atom oxygen atom ction sugges ns.
hose of meltin VP1 films.
ms.
ra- or-ng
mo-ow ed ng on nd of
in-2) he
en-ed al-tly
of ds be ed
lu-be
of
ac-he of ms ms sts
T fi F P tr P an at F b 2 an ch st cm in T b th o H F P P
Table 1: Cha ilms. Sample PVDF PVDF/PVP PVDF/PVP FTIR Spectr
For a bette PVDF and P
roscopy was PVDF and its nd 890 cm-1 t 1160 cm-1 From the FTI e identified 012). The nd the absor haracteristic From Fig tretching abs m-1 in pure P n PVDF/PVP This shift tow y the effect he carbonyl g
f PVDF. The Hong (2002).
Figure 2: F
PVDF/PVP f PVDF/PVP1
aracteristic d
φ (°
P1
P2
roscopy
er understand PVP in PVD
s used. Fig. s blends. Th are attribute
assigned to IR spectra, cr by the absor phase is assi rption bands of α and p . 2 it can b sorption ban PVP shifted P1 and PVD ward higher f
of the hydro group of PV e same result
FT-IR spec films: pure (c) and PVD
data of the n
C min-1)
2.5 5 10 20 2.5 5 10 20 2.5 5 10 20
ding of inter DF/PVP blend
2 shows s he absorption ed to the C–F o the C–C b
rystalline PV rption bands igned at 828 s at 602 and phases, respec
be seen tha nd of PVP as to 1662 cm-1 F/PVP2 film frequency ca ogen bond f VP and the m
t was reporte
ctra of nea PVP (a), n DF/ PVP2 (d)
non-isotherm
Tcon/°C
137.4 138 135.3 131 124.8 121.5 116 112.4 89 83 73 60 raction betwe ds, FTIR sp spectra of n n bands at 13 F vibration a bond (Fig. 2 VDF phases c s (Martin et
and 1063 cm d 1225 cm-1
ctively. at the carbo
ssigned at 16
1 and 1691 c
ms, respective an be explain formed betwe methylene gro ed by Chen a
at PVDF a eat PVDF ( ).
mal crystall
TcP/°C
134.8 134.7 132 126 120.4 115.7 109.6 105 102.2 96.9 93.9 85 een pec-neat 395 and 2a). can al., m-1, are onyl 638 cm-1 ely. ned een oup and and (b), Dy me niq (D eff tie fre po mo by tem In ma δ) eff det usi me gro ing 20 vs PV -15 tha the lus lec du tha int an ization beha
Tcf/
132 131 126 119 114 109 100 94 11 11 10 10 ynamic Mec Viscoelastic easured by t que. In dyn DMTA), stiff
fect, which a es, are evalua equency. The onent in sem
obility of the y the change
mperature (T
practice, Tg aximum in th
or loss mo fect of PVP o
termined by ing DMTA. ental molecu oups in the c g process (L
13).
Fig. 3 show . temperatur VDF/PVP2 s
50 to 100 °C at an increas e E' values o s of PVDF cular weight ue to the low
at the presen termolecular
Lobo and B d relaxation
avior for nea
°C .1 .2 .8 .6 .2 .6 .8 .1 13 11 08 04 hanical The c properties he dynamic namic mech fness (E-mo are two impo
ated as a fun e presence of
mi-crystallin e polymer ch e of the mod
Tg) of the pol determines t he mechanic odulus (E'') o
on the amorp evaluating d Two relaxati ular motions a
chain occurre obo and Bon
ws the storag re of neat
amples in th C at 0.1 Hz. F se in tempera of polymeric films contai
decreased c wer crystallini
nce of PVP dipole bond Bonilla (2003 process asso
at PVDF an
ΔTc
18.8 22.5 23.5 27.8 29.7 34.8 36.8 40 56.5 60.2 71.8 81.5 ermal Analy
of the mate mechanical hanical ther odulus) and ortant viscoe nction of tem f a second po ne polymers
hains that ca dulus and g lymer (Badia the temperat
al damping p occurs. In t phous region dynamic pro ion processe and local mo red during th
nilla, 2003; O
ge modulus PVDF, PVD he temperatur From Fig. 3a, ature caused films. The ining PVP w compared wi nity. It could in the film ding of PVDF 3) have repor
ociated with
nd PVDF/PV
ΔHc(Jg
-1 ) 36.49 36.41 36.11 35.95 34.1 30.3 33.84 32.5 30.92 27.28 26.64 14.67 ysis
erials could b thermal tec rmal analys the dampin elastic prope mperature an olymeric com changes th an be observe glass transitio a et al., 2014 ture at which
parameter (ta this study, th n of PVDF w
operty chang es such as se otions of sma he PVDF hea Osinska et a
(E') and tan DF/PVP1 an re range of T , it is observe d a decrease
storage mod with high m ith neat PVD
be considere ms reduced th
F chains. rted that the
the crystallin VP be ch-sis ng er-nd m-he ed on 4). h a an he was ges eg-all at-al.,
fr an ta n v fo sh cr en
F v sa
C
o ti co (Δ
Δ
w th pr th P
raction mole nd 86 °C, re an δ curve (F
eat PVDF fi alue is shifte or PVDF/PV hift of Tg to rease in the m nce of PVP, a
Figure 3: Th ersus tempe amples.
Crystallizabi
A simple m f polymers a ions was dev
ordingly, the
ΔTc) with co
Δ =Tc Pϕ+ Δ
where ΔT0c is he limit of z
rocess sensit hermodynam P factor acco
ecular motion espectively. T
Fig. 3b), wh lm is -40 ºC ed to higher VP1 and PVD
higher temp mobility of th as described
he tan δ (a) erature of ne
ility of PVD
method to e and their sens
veloped by N e variation in
oling rate (
φ
0
ΔT c
s the degree zero cooling tivity factor. mic driving fo
unts for the
ns of PVDF The maximu hich is defin . For PVDF/ temperature DF/PVP2, res
peratures con he PVDF cha previously.
) and storag eat PVDF a
F
evaluate the sitivity to pro Nadkarni et
n the degree o
φ
) can be expof undercool g rate and th
ΔT0c is asso force for nuc
kinetic effe
occurred at um value of ned as the Tg /PVP films, t s (-8 and 35 spectively). T nfirmed the ains in the pr
ge modulus and PVDF/P
crystallizabi ocessing con
al. (1993). A of undercool pressed as:
ling required he slope P i
ociated with cleation and
cts (Lorenzo -42
the g of this 5 ºC The de-
res-(b) PVP
lity
ndi- Ac-ling
(1)
d in is a
the the o et
al. be qu de the ch the tiv
co the ble cre PV sug nu of PV Th tio
Fig PV
Re
tio det me oth
X
wh tem
rel
, 1999; Song the differen uent heating gree of supe e ability of th anges in the e line of ΔTc vity factor.
Fig. 4 show oling rate. Th e intercepts ends. The re eased from 1 VP1 and 53.
ggests that ucleation of P
PVP. The va VDF/PVP2> hese results s on of PVDF i
gure 4: Vari VDF and PVD
elative Cryst
The relative on of the cry
termined from ers by parti herms. X(t) is
( )
00 ∞
⎛ ⎜ ⎝
=
⎛ ⎜ ⎝
∫
∫
TT T
T dH
d X t
dH d
here T0 and T
mperatures, r For the non lationship be
g et al., 201 nce between scan (Table ercooling wi he polymer m
thermal con c vs. cooling
ws the plots he values of to evaluate t esults show 18.8 for neat 9 for PVDF the thermod PVDF is sig alues of the P PVDF/PVP show that PV in the blend f
ation of ΔTc DF/PVP film
tallinity of P
e degree of cr ystallization m the crystal ial integratio s defined as
⎞ ⎟ ⎠ ⎞ ⎟ ⎠
c
c H
dT dT dH
dT dT
T∞ are the on respectively. n-isothermal c
etween cryst
11). ΔTc was
Tcon and Tm 1). The var ith the cool molecules to nditions. Thu g rate is the
s of variation fΔT0c can be
the crystalliz that the ΔT
t PVDF to 30 F/PVP2. Suc dynamic driv gnificant afte P factor follo P1> neat VP reduced t
films.
c with coolin ms.
PVDF
rystallinity (X
temperature llization exot
on of cryst a function of
nset and end
crystallizatio tallization tim
considered m in the subs
riations of th ing rate sho
respond to th us, the slope
process sens
n of ΔTc wi obtained fro zability of th
T0c values i 0.5 for PVD ch an increa ving force f er the additio
wed the orde PVDF film the crystalliz
ng rate for ne
X(t)) as a fun e or time w therms of pol tallization e f temperature
(2
crystallizatio
on process, th me (t) and th to
se-he ow he of
si-ith om he in-DF/
ase for on er: ms.
za-eat
nc-was
ly- ex-e:
2)
on
co fo
t
w zo ti cr an sa in la cr h
F P in
N
M
th m p th w
orresponding ollows:
T T
φ °
− =
where φ is th ontal temper ime scale. F rystallinity w nd PVDF/P ame characte ng rates due ater stage of rystallization igher cooling
Figure 5: Re PVDF (a) and
ng rates.
Non-Isotherm
Modified Avr
Several me he non-isoth mers. The Av rimary stage he model, th with crystalliz
g temperatur
he cooling ra rature axis Fig. 5 shows
with crystalli VP films. A eristic sigmo e to the sphe f crystallizati n completion
g rates.
elative crysta d PVDF/PVP
mal Crystall
rami Model
ethods have hermal crysta vrami equatio es of isother he relative c zation time (
re (T) can b
ate (Ji et al., 2 can be tran s the variati ization time All these cu oidal shape a erulite impin ion. It can b n, a shorter
allinity versu P1 (b) films a
lization Kin
(Jeziorney
been develo allization ki on was used rmal kinetics crystallinity
t) as follows
be expressed
2008).The ho sformed into ions of relat
for neat PV urves have at various co ngement in e seen that, r time requi
us time for n at various co
netics Analys
Equation)
oped to descr netics of po to describe s. According (X(t)) chan s:
d as
(3)
ori-o a tive VDF the
ool-the for ires
neat
ool-sis
ribe
oly-the g to nges
X
wh an 20
sta the ing of the by
log
wh an tal 20 sho co sta ext co
the rea can ate sho cry the co film film film
1/2
t
kin tal As ing ter sho fec du me
( ) 1 exp(
X t = −
here k and n
d the Avram 08).
In actual co antly during e parameters gs. Therefore
the crystall e cooling rat y (Jeziorny, 1
log
gZC Zt
φ
=
here Zc is the d Zt is the ra llization proc
15; Lang an own in Tabl oling rate. T ant of PVP l
tent, in cont oling rates.
The crystal e time (t) a aches 50%. n be obtaine e non-isother
own in Tabl ystallization e higher coo mpletion tim ms. Moreov ms are lower ms.
1/
2
ln 2 n
k
⎛ ⎞
=⎜ ⎟
⎝ ⎠
Obviously, netic parame llization rate s discussed e g PVDF mo ractions with ow that the cted more b ue to more in
er chains.
(−ktn)
n are the cry mi exponent
onditions, the non-isotherm
n and k hav e, Jeziorney lization rate te. The modi
978):
e modified cr te constant o cess (Yu et
nd Zhang, 20 e 2. Zc is in The modified
oaded PVDF trast to that
llization half at which the
t1/2 for non-ed from Equa rmal crystall
e 2. General processes. T oling rates h
mes for bo ver, the valu r in comparis
the data sho eters Zc and t
was reduced arlier, this ef olecular mob h PVP in the
crystallizati y PVP with teractions of
rystallization t, respective
e temperature mal crystalli ve different p considered constants b ified equatio
rystallization of the non-iso
al., 2009; B 013). The va ncreased by d crystalliza F films decr of neat PVD
f-time (t1/2), e extent of -isothermal ation 6 and lization rates ally, short t1/2
The t1/2 value have shorter oth neat an ues of t1/2 fo
son to those
ow that PVP
t1/2. Thus, th d upon blend ffect was cau bility due to e molten stat ion rate of P h higher mol f the PVDF a
(4
n rate consta ely (Ji et a
e changes co ization; henc physical mea the correctio by introducin n is expresse
(5
n rate consta othermal cry Bahader et a
alues of Zc a increasing th ation rate co
eased to som DF, at variou
is defined crystallizatio crystallizatio used to eval s. The data a
2 means fast
es indicate th crystallizatio d PVDF/PV or neat PVD of PVDF/PV
(6
influenced th he PVDF cry
ding with PV used by redu o stronger i te. The resul PVDF was a lecular weig and PVP pol
4)
ant
al.,
on-ce,
an-on ng ed
5)
ant
ys-al., are he n-me
us
as on on lu-are
ter hat on VP DF VP
6)
he ys-VP.
uc- in-lts af-ght
ly-O
ap pr 1 th v ti
X
ln
w O n P
F
Sample
Neat PVDF
PVDF/PVP1
PVDF/PVP2
Ozawa Meth
The Ozaw pproaches fo roposed by e 978). This m he non-isothe ided into sm ion is express
( ) 1 exp
X t = −
(
n⎡⎣−ln 1−Xwhere K(T) a Ozawa expon
ent depends Plots of ln⎡⎣−
igure 6.
Table 2: Cr
Φ
(°Cmin-1)
2.5 5 10 20 2.5 5 10 20 2.5 5 10 20
hod
wa model is o or non-isothe extending the model is bas ermal crysta mall isotherm
sed as:
( )
m K T
φ
⎡− ⎤
⎢ ⎥
⎣ ⎦
( )
)
ln (X t ⎤⎦= K
and m are th nent, respec s on the dim
(
)
ln 1−X t( )
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 mo rmal crystall e Avrami Equ sed on the a allization pro mal steps. Th
( )T −m lnφ
he cooling fu ctively. The mension of c
)
⎤⎦ versus lnn 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 kine lization proce uation (Jezior assumption t ocess can be e Ozawa Eq
unction and Ozawa exp crystal grow
φ are shown
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
Fig PV
cor wi sat kin tha ing sec 20
Co M
Jez ma In ma lea Qi the
X(
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: The VDF/PVP1 (b
It can be se rrelations. C ith temperatu
tisfactory for netics of PVD at the Ozawa g the crystall condary crys
09).
ombined Av odel)
It is obvio ziorny modi ary stages o order to find al crystalliza agues sugges iu et al., 200 e Avrami and
t):
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 plo b) films.
een that thes hanges in slo ure. Thus, th
r the descrip DF films. So a model can lization kine stallization (
vrami and
ous that the ification cou
f non-isothe d a method to ation process
sted a new m 00). This met
d Ozawa Equ
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 ha opes indicate he Ozawa m ption of the ome authors nnot be appli etics of polym
(Ozawa, 197
Ozawa Eq
Avrami an uld only des ermal melt c
o describe th s exactly, M
method (Liu thod is the c uations at a
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 line e that m vari ethod was n crystallizatio
have declare ied for mode mers that hav 71; Yu. et a
quations (M
alysis and i scribe the pr crystallizatio he non-isothe o and his co u et al., 199 combination
given value nd
ear ies not on ed
el-ve
al.,
Mo
its ri-on.
er- ol-97;
ln
w
co d d y o th is P b li
T m
F an
( )
nφ=lnF T
where F T
( )
=ooling rate a efinite physi egree of cry ield a linear f crystallinity he Mo mode sothermal pr PVDF/PVP2 e calculated ines. The kin
Table 3: Th model.
Sample
Neat PVDF
PVDF/PVP1
PVDF/PVP2
Figure 7: Plo nd PVDF/PV
)
−αlnt( )
/ tK T Z =⎡⎣ ⎤⎦ and α is the ical and pra ystallinity, th relationship y, as shown i el was succes rocess of nea films. The v from 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 ve VP1 (b) films 1
m refers to
e ratio of n to actical meani he plots of l for a certain in Fig. 7. It c ssful in desc at PVDF, PV values of
α
ope and the ters are listedparameters
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 for s.
the value of
o m. F(T) ha ing. At a giv
nφ versus l n relative deg can be seen t cribing the n VDF/PVP1 a
α
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 (9)
the
as a ven lnt gree
that
non-and can the
Mo
(a)
PV sho cry ing the
X( cry hig acc fou film par
An
the liz fun po fol
dX
wh exp
Z K
wh liz
Tm
cry iso me ind tio
Z G
cry iso can fun eac
Z G
The values VDF and 1.3
ow that F(T) ystallinity. O g PVP revea e values achi
t) values. Si ystallization gher F(T) va cordance wi und that F(T
ms. This is rameters.
nalysis Base
Ziabicki de ermal crystal zation progre nction (Ziab lymers in Zi llowing equa
( ) (
Z X t
K T dt =
here Kz(T), t
pressed by:
,m
( )
Z T =KZ
here Tmax, Kz zation rate te
max and the w
ystallization okinetic appr
er crystalliza dex), Gz ,was
on (11) over t
( m
g T
Z Z
T K T ° =
∫
The Gz para ystalline poly othermal cry
n be replace nction of th ch cooling ra
, (
m
g T Z
T dX
ϕ
° =
∫
of
α
vary 1 to 1.7 for P ) increased up On the other hled higher F
ieved for nea ince F(T) ref process, at alues for PVP
ith slower c
T) values are also in agre
d on Ziabick
veloped ano llization kine ess and crysta icki, 1996). abicki's mod ation (first or
)[1 ( )]
T −X t
he crystalliz
maxexp 4ln
⎡
−
⎢ ⎣
z,max and D a
emperature, width at
half-rate functio roximation, ation ability s obtained by the crystalliz
) 1.064
T dT ≈
ameter expre ymer to crys ystallization s
d in Equatio he relative c ate study as f
/ ) 1
X dT ϕdT≈
from 1.62 to PVDF/PVP f upon increasi hand, PVDF
F(T) values a at PVDF film
flects the di t similar X( P loaded PV crystallizatio re higher for eement with
ki Model
other approac etics related tallization rat Crystallizati del can be de rder kinetics)
zation rate fu
max 2
( )
n 2 T T
D −
are the max the crystalli -height meas on, respectiv the semi-cry y (kinetic c
y the integra zation range:
,max 4KZ D.
esses the abi stallize. In th studies usin on (12) with crystallinity,
follows:
1.064(dX dT/
o 2.07 for ne films. The da ng the relativ
films contai as compared ms at the sam
fficulty of th
t) values, th VDF films is
on rates. It r PVDF/PVP h other kinet
ch for non-is to the crysta te-temperatu ion kinetics escribed by th
):
(10
unction, can b
2⎤
⎥
⎦ (1
ximum crysta ization rate sured from th vely. With th ystalline pol
rystallizabili ation of Equ
(12
lity of a sem he case of no
g DSC, KZ( the derivativ
(dX/dT)φ, f
,max )
T ϕ Dϕ (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
w cr (d in n G p li P T cr v P sp P P ta E an v g et cl o th co in u F (M ln w ra re E g b eq ca er P th in
where (dX/dT
rystallization
dX/dT)φ fun ndex for an etic crystalli
Gz,α normaliz
aphol et al., ization kineti PVP films ba
Tmax decrease reased with alues of Gz PVDF/PVP2 pectively. Th PVP films sh PVDF to crys allization con
Effective Act
Several m nd Friedman ation energy er, 1956; Vya
t al., 2013) losely relate rder to calc he effective onversional ntegral isoco sed. Friedman Eq The Fried Ma et al., 20
( ( ) n X t dX t dt ⎛ ⎞ ⎜ ⎟ ⎝ ⎠
where dX(t)/d
ate as a fun elative crysta
EX(t) the effec
iven value o y plotting dX
qual to -EX(t an be calcula Fig. 8 illu rgy as a fun PVDF and PV he results, t ncreasing the
T)φ,max, Dφ a
n rate, the w nction and t
arbitrary coo izability inde zation with
2004). Tabl ics parameter ased on Ziab ed, while (dX
increasing for neat PV films were he reduction hows that PV stallize unde nditions.
tivation Ene
methods such n methods ar y for the crys
azovkin, 200 ). In fact, t d to the rela ulate approx
activation e method of F onversional m
quation dman Equatio 11; Friedman ) tan t cons t =
dt is the in nction of tim allinity (X(t)) ctive energy
of X(t). A str
X(t)/dt versus t)/R. Thus, th
ated from the ustrates plots
nction of rel VP loaded PV
the activatio e relative cr
and Gz,φ are
width at hal the kinetic oling rate. T ex, Gz, can
φ (i.e., Gz e 2 summari rs of neat PV icki's model
dX/dT)φ,max, D
cooling rate VDF and PV 1.006, 0.933
of the Gz va VP decreased r non-isothe
ergy
h as Kissing re used to ev
stallization p 02; Friedman the activatio ative crystall
ximately reli energy, the d Friedman an
method of V
on is expres n, 1964): ( ) ( ) X t X t E RT − nstantaneous me (t) for a ), R is the ga
barrier of th raight line c s 1/TX(t). The
he activation e slope of the s of effective lative crysta VDF sample on energy i rystallinity, the maxim lf-height of crystallizabi The Ziabicki be obtained = Gz,φ/φ) (S izes the crys VDF and PVD
. The values
Dφ and Gz,φ
e. The avera VDF/PVP1 a 3 and 0.835,
alue for PVD d the ability rmal melt cr
ger, Vyazov valuate the a process (Kiss n, 1964; Omr on energy w
inity degree. iable values differential i d the advanc Vyazovkin w
ssed as follo
(1
crystallizat given value as constant, a he process fo can be obtain
slope of plo n energy (EX e straight line e activation allinity for n es. According increased up suggesting t
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 the inc exp fro slo ob var PV cau po Fig fun PV Ad act to acc the Th be app fin ma the no en op lin pre wa sys Φ wh a E e crystallizat crease in rel
pect that tra om the equili owed down served that t ried in the VDF/PVP1<
used a delay lymer.
gure 8: Plo nction of rel VDF/PVP film
dvanced Isoc
It is notewo tivation ener
reliably pre curacy of su e accuracy hus, errors in minimized. proximation nal plots yie ations unden e activation
n-linear pro ergy by the ed. An adv near) was de esent study, as applied to
stem using th
1 ( ) n n a i j E = ≠ =
∑∑
here φ is th
a is the ac
tion become ative crystal ansmission o ibrium melt t
as crystalliz the calculate e following PVDF/PVP2 in the crysta
ts of effectiv lative crystal
ms using the
conversiona
orthy that th rgy on relativ dict the beh uch predictio
of calculatin n computing t
One of the s s intentionall lding the ac iably induce energies. To ocedure for e isoconvers vanced isoco escribed by a non-linea the dynamic he following , , ( , ) ( , ) n
a a i a a j i
I E T I E T
φ
≠
∑
he cooling ra tivation ene
es more diff llinity. Indee
of the polym to the growt zation procee ed activation g manner: 2 films, indic allization pro
ive activation llinity for ne e Friedman e
al Method
he sole depe ve crystallini havior of a s ons obviousl ng the activ the activatio sources of th lly used to de ctivation ene ed an error in o resolve th computing sional metho onversional
Vyazovkin ( ar isoconvers c DSC data g equation: ) j i φ φ
ate, T is the ergy, i, j ar
fficult with a ed, one shou
mer segmen h front will b eds. It is al
energy valu neat PVDF cating that PV ocess of PVD
n energy as eat PVDF an
quation.
endence of th ity is sufficie substance. Th
ly depends o vation energ on energy mu hese errors a erive the line ergy. Approx n the values his problem, the activatio od was deve method (no (1997). In th sional metho of neat PVD
(15
e temperatur re the ordin
n ra p
E
In m a I I an P E ap th v ob F fu P m o v n taumbers of D ates. The ac articular con
a
E
at which t n Equation ( mined by thel., 1977) giv
0
( , )
T
a I E T
α
=
∫
(
a,)
E I E T =⎛⎜⎝
nd
( )
exp(
P x x − = Each valu aE dependenc pplied the s hermal and n
ersional plot btained from
Figure 9: Plo unction of re PVDF/PVP fi method.
The non-i f PVDF and arious coolin eat PVDF, P allization ab
DSC runs per ctivation ene nversion lev
the Φ( )t fun (12) the temp Senum-Yan en as:
exp(Ea)dT RT α
( )
a E P x R ⎞ ⎟ ⎠)
3 4 20 x x x x ⎛ − + ⎜⎜ + ⎝ue of X(t) wa ce. The advan same compu
non-isotherm t trends in F m the Friedm
ots of effect elative crysta ilms using th
CONCL
isothermal m d its blends ng rates usin PVDF/PVP b ility due to
rformed at d ergy can be vel by findin nction has a m
perature inte ng approxima T 2 3 2 18 88 120 24 x x x + + + + + as minimize nced isoconv utational algo mal DSC dat Fig. 9 are s an method.
tive activatio allinity for n he advanced i
LUSIONS
melt crystalli with PVP w ng DSC. As blends exhibi the tendenc
ifferent cool e found at a ng the value
minimum val egral was det ation (Senum
(1
(1
96 40x 120
⎞
+
⎟⎟
+ ⎠ (
d to obtain ersional meth orithm for i ta. The isoc similar to th
on energy a neat PVDF a
isoconversio
ization kinet were studied compared w it reduced cr cy of PVDF
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 int tw ato PV wa fou Tg Jez de be inv Ki cal PV aff tio PV Fre Th PV con Ba Ba Bi Ch Fa Fre teract with ween the hyd
oms of the c VP on the g as also evalu
und that PVD values in c ziorny, Mo scribe the cr
successful. valid for de inetic param
l models sh VDF decreas fected by the on energies o VDF/PVP bl
eidman and he higher v VDF/PVP ble nsistent with
adia, J. D., A., Ribes-G mal Analys tion of Poly and Interfa Jyotishkum Co. KGaA, ahader, A., G lization kin carbon nan liquid. Mac anchi, O., M
rigaray, S. Melt crysta meric silses tions. J. No hen, N. P. and
and compo PVP blend. an, W., Zhen
behavior in and poly(vi topology of Polym. Sci. eire, E., Bia E. C., Forte PVDF/PMM shear mixe (2012). PVP throug drogen atom carbonyl grou glass transiti
uated by DM DF films co comparison t
and Ziabick rystallization
The Ozawa escribing the
eters obtaine howed that t
sed in the p e molecular w
of melt crys lends were advanced value of th ends compar h the lower ra
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