Kinetics of decomposition of poly(vinyl chloride)/low-migration

POLIMERY 2005,
50, nr
7-E
601
BARBARA ślVIERZ_MOTYSIA1), KRZYsZTor PIEL1cHowsKl2)")
Kinetics of decomposition of poly(vinyl chloride)/low-migration
polyesterurethane plasticizer blend
a thermogravimetric study
-
RAPID COMMI'T.IICATION
summary - Kinetics of d€cornposiiion of Poly(viny] Ćhloride) (PvC), Plasii_
cized either by di(2-ethylhexyl)phthalaie (DEHP) or medium molecular
$'eight polyesterurethane (PESTUR) or by both plasticizers, was studied by
isoconversional methods on the basis of thermogra\.imetic data unde! dynamiĆ heatint conditions' It has been found ihai ihe initia] decomPosition
temP€Iaiule is hi8hel fof PVC Plasticjzed r\'iih PESTUR in ĆomPalison vriih
PVc plasiicized rvith DEHP oI 1vith PESTUR/DEHĘ and thelmal degrada_
tion shows featules of mu1tiŚteP Ćompl€x process' Application of Po1ymelic
plasticizer leads to ih€ inclease in values and a "smoothin8'' effect in ńe
course of energy of activatior'r and pre-exponential factor at initial stage of
decońposition indicating thus the hindeled miglation of mediuń moleculal
weitht compound from PvC mat x (in comParison 1\.iń PVc coniaining
monomelic DEHP) due to stelic hindlances as we]l as due to sP€cific interac_
tions betrveen C=O and Cl groups along the macrochains.
Key words: Pol)'(vinyl chloride), po1ymedc plasticizeł kinetics of degladation, ener8y of activation, ihermottavińeiiic analysis'
Piasticize.l poly(viny1 chloride) (PVO is one of the
mosiwidely used polymeric materials formedical appli
cations. Flexible PVC is used for the manufaciure of
blood bags, hansfusioll tubings and as packaging for
pharmaccuticals [1,2]. PVC used inmedical applications
coniains up to ,10 % (by rveight) of the plasticizer which
i5 usua]ly di(2-eńylhexyl)phlha1ate (DEHP)' Horvever,
DEHP is a hypolipidemic hepatocarcinogen and ihere
are some reports questiollint the safety of DEHP in
Pvc-based medical devices [3-6].
Generally, ihe snbjeci ofmigration and volatilizaiion
of plasticizers has been rvidely studied [7-10]. Hence,
various attempts have been made io reduce plasticizer
ńitratjon fi'oln P1asiicized l'VC; meńods employed inc1rrde coaiin8 ol PVC sul{ace wiih polym€rs such as
acfy1ai€s oI Polyestels, closslinkin8 of Pvc dulin8 plo'
cessing wiih peroxides or grafring hydrophilic monomers onto ihe surface of PVC by l-radiation/plasma
treatment 111, 121. PVC lvas also chemically surface
modified by nucleophilic substitution o{ chlorine atoms
bV Fhotołcii' e N Jrdiethyl diiIlio. albamaie jn aqueour)]ndust.ia]
chenistrv Research
]n-.titut€,
ut R)'dl8ień 8' 0]
media in the presence of a suitable phase Eansier .atalysi
- further crosslinking by inadiation with UV re'
sulted in for ation of a barier for the diffusion of DEHP
from Łhe matlix [13]. one of the Iecent r€search dilec_
tions tolvards lowering the migration and \,olatilization
ofPlasticiŻeń ftom PVc j5 application of high moleculal
Weight elasiomeric polymers e.8' Polyestef_bas€d dlel'
moplastic polyurethanc (TPUR) elastomers as blending
resins that display plasticize$' performance. Unlofiunately, PVC/TPUR blends are difficull to process due to
iheir hish me]t viscosity and 1imited h€ai siabiliiy
114-161. These drawbacks could be at least partially
eliminated if medium molecular vreight semi'soIld
oHłelminated Po]yesterurethanes (PESTUR), showing
hi8h degrec of comPaiibi1ity wiih PvC ńatrix, $'ere for
plastification PuĘoses [17 '19].
Hcnce, in this communicatlon some kinetics aspects
of the detiadaiion Process of PVc PlasticiŻed with nove1
macromolecular po1yesterulethane'based p]asticiŻef af e
reported.
EXPERIMENTAL
793
Ż)
Materials
kpielich@usk'Pi'edu.Pl,te]':(+.ł8]2)ó282727,Iłx] (+4612)62E2038
Wlocłarł'ek (Poland).
CraĆÓ\! Uńn'Ćrsjty Óf T€chno]o8)', DĆFartmĆnt oi Cncńistry and
Techlologv of Polymcrs, ul' łasza*Tka 2.1, 3] ] 55 Kjaló$''
! To u'noń aIl cor.€sPond.nce should bc aadresscd' e_mai]]
SuspensionPVC (K-70) ivas
a
produci of ANI{IL SA,
POLIMERY 2005,
602
50, ru
7-8
As monomeńc Plasticizel di(2-ethy1h€xy1)phthalate
(DEHP) produced by Boryszerv SA Sochaczevr (Poland)
..
Polyesterurethane GESTUR) of Mto = 13 000 was synth€sized ai Industrial chemistry Research Insiitute by
prepolymer method using isopholone diisocyanate and
a copolymer of 1,6-hexanediol and adipic/phihalic acid.
60
!ło
20
Plepalation of samp1eŚ
0
PVC compositions rvere prepared in a twostageprocessr durin8 ihe first siage, dry blends of PVC and additives weI€ obtained in a high_speed mixer at 100 oC and
then ihe blends homogenized ai 160 Óc in a Brabendel
Plasiicorder were processed in a laboratory Brabender
single-screrv extruder at 155-165 oC. Finally, square
plates were press molded at 165 oC under 7 MPa pressure. The detailed desoiption of this procedure was pres€nted e1selvhele [17]'
Fił' 1' TCA rÓfi\es
10
of
1-3
{
ńe samPles is glven in Table
l4
/F
U
rio
EBB
rro
t2
l0
6!
i
{ł
d
0,2
1'
ó00
abtahed at heąlifig rate
t?0
(33.5)
DEHP 08.5)/PrSrJR Os)
PISTUR (50)
Desc ption
of samples
190
j
DIHP
3
400
Tcmperature, "C
Klmin
llałLÓztr Gńouńl i. lt' !')
l
200
- ljo
T a b i e 1' Des.riPtion ol the s.npleś oi Pvc PlaśtiĆizede'ith
2
0
0,4
4,6
0,8
Fig ' 2 ' Energy af ncii:oąt\on (E) and logarithn of pra-txponen!i"1 lactar (A) wrsus liaction7l mass lass (ct) fot the deyada-
lbn yacess
af sample 1 cd\c1l\ąled
b! azawa Fl!11fl wal|
M€thod
Thermogravimeiric analysis OGA) was performed
using a Netzsch TG 209 themal analyzer in arton atmosphere using open cr-Al2o3 pan, operating in a dy"
namic mode at a heating ńte 2'5,5, 10 or 20 K/min. The
sample weight rvas aboui 7m8.
RESULTS AND DISCUSSION
At ihe ljrsi stage, analysis was performed at heating
rate of 10 K/min io ascertain the thermal siabiliiy of the
samples
-
results ate shown in Fig.
1.
initial decomposition temperaoC, lvhereby
ture ofsample 3 is ihehithest, reaching 252
oC,
respecti\.ely.
for samples 1 and 2 ii is 215 and 225
Detradation sho'Ws featules of a multist€P compIex
process. To obiain additional infomaiion of the nature
of this process a kinetiĆ analysis was Pelformed by two
isoconversional methods Gy Ozawa-Flynn-Wa11 and
Friedman) thal yield values of activation energy (E) and
pre'exponential factor (,4) 120-221. Both methods lead
io similar resulis.
The Iesults of ozawa-Flynn*Wall analysis of ńe
ihermal degradation oI sample 1 are presenied in Fig.2.
E and,4 are ploited versus ftactional mass loss (cr),lvhat
It can be seen that ihe
is a measure of conversion degree. There are three regions of energy of aĆtivaiion and Ple_exPonentlal factol
changeability which arise from migration of the
monońelic plasticizer and decomposition of PVc matńx'
The first region is most likely associated wiih mi8ration ofPlasticizel rvhich is lost fiJst fuom the sulfac€ and
then from ihe bulk. Murase et. al. [23] also investigaied
the migration of DEHP i11 PVC under heatin8 by depth
analysis but using FT-IR specboscopy and noticed that
depth profiles depended on ihe stabilizers used. For
PVC/DEHP stabi]ized with di"ź-butyl-tin-dilaumte,
DEHP seems to be lost first from the surface, and then
difflrses from the polymel matdx to the surface. lvhiĆh is
a typical pattern of diffusion control. On the oihff hand,
in Pvc/DEHP Ćoniaining dj-71_buty]-tin'di1aulate oI
di-r-butyl-tin-maleate polymer DEHP evolution is less
i iensive and characierized by a smaller rate coefficient
is a typical surface conbol paitem [23].
- ihis
Isoihelńal \,rei8ht loss kineiics of Plasiiclzed PVc ai
oC, siudied by Alldouin
the iemperature range 85-120
Ćt' nl. [2'|], showed ihat in this iemPefaluIe ran8e ihe
plasiicizer loss lvas the only significant source of iveight
change, but stiIl at least two diffel€nt kinetics re8imes
POLIMERY 2005,
50, nr
7-E
603
lfele involved, as e\.idenced by ńe chalacieristic shape
of A(henius ploi.Ii could be supposed thai almosi coniinuous plasiicizeI monola},el exisied ai ihe sańp1€ sulface, making ihe evaporaiion rate practically insensitive
io the p]asiicizer bulk concenbation' Inde€d, vrhen this
]attel decreases, the free \.olume fuaction anct thus, th€
p]asticizel diffusivity decleases and can r€ach a criiical
value beyond vrhich the !\.hole Ploc€ss b€comes diffusion-corlholled. A simple kinetjc model cannot, therefcrc dp.crbl ll_c \vLolc plasl;c.zer-los> procF-5 5 n.e
there is plobably a kinetic transition stage behĄ'een the
tiĄ'o legimes'
At higher temperature a gradual decomposition of
the PVC matrix iakes place by splitting off hydro8cn
chloride. As earlier investitations shorved, during this
process polyene sequences lvere formed that wcre acti\.e
il'r sccondary rcactions leading to crosslinking ancl formation of aromatic pyrolysatcs 125,261.
Kinctic analysis by Friedman method of degradatiorl
of sample 2 showrl in Fig. 3 leads to conclusion thai the
addiiion of PESTUR as po]ymeriĆ PlasiicizeI causes an
increase in values and "smoothjns" of a curvc of activaiion €nel8y and ple-exponeniial {actoI versus deglee of
conversion profile (up to a < 0.7).
As ii was shown in Fig. '1, thc use of only PESTUR as
a Plasticiz€r in amount 50 wt. % (sample 3) makes the
ih€rma1 d€composition charactcrized by Ie1aii\.€1y siab1e
E and Aprofile, apart from ihe final stage lor c. > 0.8.
I011
ó0
ź loo
=.
40.
21]l]
0-
0
,20
-200
-400
0
0,2 0,.1 0,6 0,8
40
l
Fis 3.E elłv ofacti1)atbfi (E) ą d lo4drilhm aJple-e|pofientiil fnctat (A) l,ctsus'fracliD aI t ass loss @) lot the deyatlaliDn focess af sanryIe 2 calculatetl b! Flbllnn methad
The dlffelent kineiic behaviour of PVC plastiĆiŻed
lvith PESTUR in comparisol'r rviih PVC containillg
monomedcDEHPcanbeexplained interms of hindered
migaiionof medilmmolecularweightcompoundfrom
PVC matrix due to stelic hindlanĆes as 1vell as due io
specific intelactions behv€en c=o and Cl $ouPs along
the macrochains. Ii is well knolr.n that chlorinated poly_
ńels ale miscib1e 'lviih many Polyesiets and it has been
shown ihai ihe miscibility of these blends can be due to
hl'dro8en bonding betr"reen ihe c=o grouPs of the
E
=
i
r200
r20
I000
r00
.00
6A
',.
ooo
200
ryłę
0
0,2
Fił. 4 ' El]"r&|
0,ó
0,8
Ól actixntia11 (E) nnl1
Ioła\ithn af łe-erya e11(A)
ul5u5
alfipss
loss k!) fol the deyalląfactor
fractilJ
lion racess a| safl|ple 3 cnlculąted b.! ozau,ą-F]!11n-wa1l
liil
PESTURand łr-hydrogen ol chlorinated po1ymer I27,28J
or C=O C1-C inieractions of dipole-dipole type t29,30J.
Bv the appropriaie anangement of Cl aioms in ihe polymel sfucture, the ]altel ini€Iachon wi1l becomc a factor
controlling thc propcrtics of thc blend. This rvill occur as
ihe greater ihe number of non-repulsive intemctions
\ńich exist on a molecu1al Ievel bei .€en ihe b]end's
componenis, ihe more dense lhe arrangemeni of thc miclosLructule ]€ading io an ińplovement in thc system's
physical properties. On ihe other hand, the rate of diffu'
slon of volatile prodrrcts ihrough microphase domain
siruciure ay differ due to changcs h moryhology arlangcmcnt thus considelably affeciing ihe ov€Ia1l decomposition route.
Morcovcr, the complctc moryhological and siructural descdpiion of PVC/PESTUR blend is exbemely
Ćomplex sinĆe boih PVc, lĄ'ith its hielarchical miclosiruciural aIlanBemeni, and PESTUR, coniaining alternaie sofi and hard segment units, contdbute to the n1ultiĆomponent blend system thus affecting considerably
its thermal propertics.
Further kinctic studies to(.ards deiennination of ihe
folm of f(c{) mod€I functions ale undelway and l,{i]l be
repoft€d it1 ihe future [31]'
CONCLUSIONS
It has been found that the application ofpoll'estemrethane plasticizer led io the increase and a "smoothing"
€ffect in the cource of acti1.ahon ener8y and PIe-exPonential factor at the initial stage of PVC blends degradation indicating thus ihe hindercd migration of medium
molecu1al ' 'ei8hi cońPorjnd from PVC mailix (in comparison rviih PVC containing monomedc DEHP) due to
steric hindrances as vrell as due to specific interaciions
Cl groups along the maclochains.
Hindered mitration of a plasticizer is an exbcmeli' imPortant palań€tel in medica]applications, so the resu]ts
obtained may be applied to desigr of P\rC blends with
improved properties.
betlveen C=O and
644
POLIMERY 2005,50, nr
REFERENCES
1'
oblóiMuzajM', świerz_Motysia B., szabJowska B':
"Po1y(vinyl chloride)" (in Polish), wNT, Warsaw
2'
3'
świerz-Motysia B'|Polbnery 20Ca,4a, Ę4'
schn€id$ B', schena J', TIuo8 R', Jacobson M', Ke\,],
4'
1.997.
S.: N . EnBl. I . Med. 1989, 320,
Ptonait
L563.
s' L', Nau H', Maier R'
F', \Ąrittfohi
W,
5.
ó.
7.
obladen M' | 7i'l6/fusŁ'1 1993, 33, 598,
JaeSei R. i., Rubin R. I.: Nutritbn 1.997 ,11/ 12, t010.
Wang Q'' stolm B' K j palym. Testillł 2005,24, Ż9a '
Kovaćic T'' Mlklić Z j Thelnochifiba Actn 2002, 381,
8'
49.
N,rarcilla A', Galcia s', Galcia-Quesada J. c': /'
9'
Appl. Plto|. 2004,71,
Jimenez A., ToII€
stub 2040,73,447.
10' stanhoPe
11. Duvis T.,
157
,4łrl'
.
L'' Kenny J' M' Pouln Dełtad'
Neizel N.: Palimery Żaa3,48, 42'] '
Karles c., Papaspyddes C. D.:/ Appl ?oB '.
ł1111' sci' 1991', 42,191.
12. Krishnan V K., Jayakishnan A., FrancisJ. D.:
Bb"a-
terdls 1991,72,489.
13' Lakshmi S', Jayaklishnan A': Pol!1ńer 1'99a,39,151'
14. "Polymer Blends Handbook" (Ed. Uh.acki L.), Klu,
wel Acad€mjc, Doldlecht 2003'
15. Piia J. R. R., Sampaio E. E. M.,
Polln. Testihs 2A02, 21 545.
Moniefo E. E.
C.:
7-8
1ó' Pielicho\Ą'ski K', Nju8una J': "Therma1 de8iadation
of Po1yrn€ric matelials", RaPra Technolosy Ltd',
snawburv 2uu5.
17 Palish pa1;t appt . 229 354 (2AAU.
'I8. sWierŻ_Molys]a B.'
Ko,,aliewlC7
PeIka J': Palinery 1999,4ą'780'
J'' PrZ)by]slj
J',
lo' 5W:erz-Motys a B'| .clU Ąnr' Reporl 200l' ]CRl'
Warszawa 2002, 72.
20' ozawaTł B11l1' chem' so.' /pn' 1965, 38. 1881'
21' nynn J' H', WallL' A: Polym. Lłt' 196ó,4'23Ż'
2Ż' lrjedndn H' l':] fo]yą' cri' loo5 cb, l7Ę
23' Mulase A', sugiura M', AragaI': Polln De|L stąb'
1991, 43, 4L5
2'1'
.
Audouin L', Dal1e B ', Melz]el G',yeńu
Palytn. Sci. 1992, 45, 2091
25' Pi€lichowskj
K', Pie1ichowski
1995, 10, 257
.
7995, 40,377
.
j'|
]
Appl'
.
J',
German K': PolfiĆly
26' Pieiichowski K', Pielichowskii', G€Ińan K.:Pol'nery
27. ZiskaJ.
J.,
Paul D.
R.:
Pollmer 't981,22,91,8.
28' Koscie]ecka A'|E /' Polyfi' I ' 1993,29, Ż3'
29. Allard D., Prud'homme R. E.t l. Appl. Palym. Sci.
30' Aubin M', Bedald Y, MorrjssetieM. n, Prud,hońme
R' Ej ] ' PÓryn. sci., Pal!fi. Phys ' Ed}1''1983, 21', 233'
31. Pie1ichowski K', świeĘ-MotysiaB'| /. Theft Ahnl.
'
Ctloll'm. submitted.
Receiłed
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