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Blends of hydroxypropyl methylcellulose and poly(1-vinylpyrrolidone-co-

vinyl acetate): Miscibility and thermal stability

Article  in  Polymer Degradation and Stability · October 2005

DOI: 10.1016/j.polymdegradstab.2005.02.010

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 Polymer Degradation and Stability 90 (2005) 21e27
www.elsevier.com/locate/polydegstab

Blends of hydroxypropyl methylcellulose

and poly(1-vinylpyrrolidone-co-vinyl acetate): Miscibility
and thermal stability
Cláudia M. Zaccaron, Ricardo V.B. Oliveira, Marcela Guiotoku,
Alfredo T.N. Pires, Valdir Soldi*
Grupo de Estudos em Materiais Poliméricos (POLIMAT), Departamento de Quı´mica, Universidade Federal de Santa Catarina,
88040-900 Florianópolis, SC, Brazil

Received 13 January 2005; received in revised form 3 February 2005; accepted 6 February 2005
Available online 25 March 2005

Abstract

The miscibility, kinetic parameters, and mechanism associated with the thermal degradation of hydroxypropyl methylcellulose/
poly(1-vinylpyrrolidone-co-vinyl acetate) (HPMC/P(VP-co-VAc)) blends, were analysed. The presence of only one glass transition
temperature (Tg) in the blend, intermediate between those for the pure polymers, the shift of the bands in the region of 3430 cmÿ1
and the disappearance of the band at 1647 cmÿ1 from the infrared spectra, suggest miscibility between the components. The
thermogravimetric curves associated with the temperature of maximum degradation rate (Tmax) indicate a higher thermal stability
for the blend with 30% HPMC and for the pure copolymer. This conclusion was supported by the activation energy (E ) values
which increased to ca. 190 and 170 kJ molÿ1 for the blend with 30% HPMC and the pure copolymer, respectively. The E-values for
the studied systems suggested a degradation mechanism associated with a random scission of the chain. The FTIR spectra of the
solid residues from the thermal degradation reaction of both systems suggest the formation of alcohol and unsaturated
hydrocarbons as reaction products. For the HPMC system, CO2, CO, aldehydes, alcohols and ethers were detected as volatile
products. Volatile products such as, acetic acid, CO2, CO and NH3 were detected for P(VP-co-VAc).
Ó 2005 Elsevier Ltd. All rights reserved.

Keywords: Hydroxypropyl methylcellulose; Poly(1-vinylpyrrolidone-co-vinyl acetate); Thermal degradation; Activation energy

1. Introduction as a matrix for drug delivery [5,6], in building materials,

for dye and paint removal, in adhesives, cosmetics, coating
Cellulose and their derivatives have been extensively processes and in the agricultural and textile areas [7].
used in recent decades, mainly due to their potential The thermal stability and degradation kinetics of
applications in different areas and properties such as cellulose derivatives have been described in the literature
biodegradability, solubility in water (derivatives), capa- by various authors [8e10]. Different processes, such as
city to form films, etc. [1e4]. Hydroxypropyl methylcel- molecular characterization, stability, recovery during
lulose (HPMC) is a hydrophilic polymer extensively used recycling, kinetic and chemical processes and macromo-
lecular reactions, have been considered in the degrada-
tion of polymers, in particular polysaccharides [11].
* Corresponding author. Tel.: C55 48 331 9219; fax: C55 48 331
Zohuriaan and Shokrolahi [9] studied the thermal
9711. degradation of various cellulose derivatives observing
E-mail address: vsoldi@qmc.ufsc.br (V. Soldi). that the decomposition started between 200 and 280  C.

0141-3910/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymdegradstab.2005.02.010
22 C.M. Zaccaron et al. / Polymer Degradation and Stability 90 (2005) 21e27

The exception was methylcellulose in which the thermal overnight at room temperature. The resulting solutions
degradation started at 325  C suggesting a significant were spread over Teflon plates and the solvent (water)
dependence on the structure and functional groups was slowly evaporated. After the solvent evaporation
present in the chain. The structural dependence was also the films were dried under vacuum and stored in
analysed by Nada and Hassan [10] observing that the a desiccator until analysis. Films were prepared with
temperatures of maximum degradation rate for cellulose the following compositions HPMC/P(VP-co-VAc):
and grafted cellulose were 315  C and 260  C, re- 100/0, 70/30, 50/50, 30/70 and 0/100.
spectively. In general, for polysaccharides, processes
such as dehydration, depolymerisation and pyrolytic 2.3. Infrared spectroscopy
decomposition occur at high temperatures (ca. 350  C),
forming H2O, CO2, CO, CH4 and unsaturated struc- Infrared spectroscopy (FTIR) was carried out on
tures as products of degradation [9,12,13]. Bomem equipment, model FTLA 2000 (Japan), with
Blends of poly(1-vinylpyrrolidone-co-vinyl acetate) a resolution of 4 cmÿ1, in the range of 4000e400 cmÿ1.
[P(VP-co-VAc)] with cellulose acetate are used as mem- For miscibility studies, the FTIR analysis was per-
branes in the pervaporation processes [14]. Kwok et al. [15] formed using 0.25% (w/w) films of the polymers and
evaluated the plasticizer effect of P(VP-co-VAc) on blends at room temperature.
HPMC. Properties such as, water permeation, mechanical Solid residues and gas products evolved from thermal
behaviour and glass transition temperature, were studied. degradation reactions were also analysed by FTIR. For
In terms of thermal degradation only the homopolymers this analysis, samples of ca. 200 mg were submitted to
PVP and PVAc have been studied. The degradation thermal degradation in a tubular oven (Lindberg/Blue)
reaction of PVP occurs via only one main stage of mass at the required temperature, under nitrogen atmosphere
loss, starting at ca. 400  C, leading to the formation of (50 cm3 minÿ1) at a heating rate of 10  C minÿ1. The
esters as a consequence of the scission of the NeCeO solid residues were cooled to room temperature and the
bonds at 480  C, confirmed by the evolved NH3 [16,17]. FTIR measurements were carried out in KBr or on SiO2
For PVAc, on the other hand, the thermal degradation supports. The spectra of the gas products were obtained
occurs via two main stages, one associated with the during degradation at different temperatures in the
deacetylation reaction at ca. 325  C leading to the tubular oven connected to the FTIR equipment.
formation of polyenes, which at 460  C (second stage)
2.4. Thermal analysis
degrade forming benzene, toluene and naphthalene [18,19].
In order to improve the thermal stability of HPMC it
DSC measurements were performed in a DSC 50
was blended with P(VP-co-VAc), a more thermally
(Shimadzu, Japan) under nitrogen (50 cm3 minÿ1). The
stable copolymer. In this study, pure components and
samples were first heated to 150  C (heating rate of
blends with 30, 50 and 70% HPMC were analysed and
20  C minÿ1) to remove adsorbed water. They were then
compared in terms of their thermal stability, kinetic
rapidly cooled to room temperature with liquid nitrogen
parameters and products of degradation under nitrogen.
and a second scanning to 300  C (heating rate of
10  C minÿ1) was obtained.
Thermogravimetric analysis was carried out on a
2. Experimental
TGA-50 (Shimadzu, Japan) under nitrogen atmosphere
(50 cm3 minÿ1) using an average sample of 7 mg. Non-
2.1. Materials
isothermal experiments were performed in the tempera-
ture range of 25e600  C at different heating rates (5, 10
Hydroxypropyl methylcellulose [HPMC] and poly
and 20  C minÿ1) for each sample. The thermogravimet-
(1-vinylpyrrolidone-co-vinyl acetate) [P(VP-co-VAc)]
ric data were analysed using the Ozawa method [20] and
were obtained from Sigma-Aldrich (St. Louis, USA).
the parameters determined using the associated TGA-50
The molecular weight of HPMC, determined in this
software. The activation energy was derived from the
study by intrinsic viscosity, was 4.0 ! 106 g molÿ1. The
slope of the dependence of the reaction rate upon the
copolymer P(VP-co-VAc) with a molecular weight
reciprocal absolute temperature, at defined weight loss.
w5.0 ! 104 g molÿ1 (determined by size exclusion chro-
matography) had an average molar ratio of vinyl-
pyrrolidone/vinyl acetate of 1.3/1. Deionised water was 3. Results and discussion
used in all experiments.
3.1. Miscibility of the blend
2.2. Film preparation
In order to investigate the miscibility of the HPMC/
Pure polymers and a mixture of 2% (w/w) HPMC copolymer mixtures, FTIR and DSC analyses were
and P(VP-co-VAc) in aqueous solution were stirred performed. The FTIR spectra for pure components and
 C.M. Zaccaron et al. / Polymer Degradation and Stability 90 (2005) 21e27 23

blends with 70, 50 and 30% HPMC are shown in Fig. 1.

Pure HPMC had bands related to OeH stretching at HPMC/P(VP-co-VAc)
3430 cmÿ1, a CeH stretching region at 3000e2800 cmÿ1, 100/0

Endotherm
C]O carbonyl stretching from the glucose of the
70/30
cellulose at 1645 cmÿ1 and a CeOeC stretching region
at 1300e900 cmÿ1. For P(VP-co-VAc) the main absorp- 50/50
tion bands were associated with OeH stretching at
3600e3000 cmÿ1, CeH stretching at 3000e2800 cmÿ1 30/70
and at 1370 cmÿ1, C]O carbonyl groups from PVAc at
1732 cmÿ1 and PVP at 1662 cmÿ1 and CeOeC stretching 0/100
at 1300e1000 cmÿ1. With the decrease in the percentage
of HPMC in the blends, the band at 1645 cmÿ1 (glucose
carbonyl stretching) disappears and an apparent broad-
ening of the OeH region occurs. The broadening of 80 100 120 140 160 180 200
o
the band associated with the hydroxyl group indicates Temperature ( C)
the formation of intermolecular hydrogen bonds. At the
Fig. 2. DSC curves for the pure components and HPMC/P(VP-co-
same time, a small shift of the carbonyl stretch of P(VP-
VAc) blends. Heating rate 10  C minÿ1 and nitrogen flux of
co-VAc) occurred in the blends in relation to the pure 50 cm3 minÿ1.
copolymer. These shift also suggest the formation of
intermolecular hydrogen bonding, similarly to the results
reported for blends of HPMC/PVP [21]. value (154, 145 and 126  C, respectively) which was
DSC measurements were performed in order to intermediate between those for the pure components.
analyse the glass transition temperature of the blend. In These data are in agreement with the infrared measure-
Fig. 2 the DSC curves for the studied systems are shown. ments, suggesting component miscibility.
The Tg values for P(VP-co-VAc) and HPMC were 109  C
and 190  C, respectively. Chatlapalli and Rohera [22]
determined for HPMC from two different sources Tg 3.2. Thermogravimetric analysis
values of 184  C and 187  C. The small differences are
probably associated with the structure and orientation of The thermal stability at a heating rate of 10  C minÿ1
the polymers, residual monomers and polarity (relative under nitrogen was investigated and the apparent
hydrophilicity) of polymer molecules. Other factors such activation energy of the corresponding thermal degra-
as preparation method and heating rate can affect the Tg dation reaction calculated through the Ozawa method
values. For example, McPhillips et al. [23] determined [20]. For all systems, a small mass loss was observed in
for HPMC Tg values in the range 160e168  C using the range 40e150  C (not shown in Fig. 3) which was
modulated temperature differential scanning calorimetry attributed to moisture adsorption. Parameters such as
(MTDSC). Each HPMC/P(VP-co-VAc) blend composi- the temperature of maximum degradation rate (Tmax,
tion (70/30, 50/50 and 30/70) had showed only one Tg defined by the TG derivative curves in Fig. 3B),
percentage of mass loss in each stage of degradation
and percentage of solid residue at 600  C, are shown in
HPMC (Wt. ) 1645 Table 1. Although the parameters related to the water
(100) adsorption are included in Table 1, the corresponding
3430
kinetic parameters were not determined.
1730 1660
Transmittance (a.u.)

(70) In Fig. 3 the thermogravimetric curves of HPMC,

(50)
P(VP-co-VAc) and blends with 70, 50 and 30% HPMC
are shown. Pure HPMC had only one stage of
degradation at Tmax Z 393.5  C which corresponds to
(30) 77.3% mass loss. For other cellulose derivatives such as
sodium carboxy methylcellulose, hydroxy ethylcellulose
(0) and methylcellulose Tmax were 303  C, 299  C and
370  C, respectively, indicating that they are less
thermally stable than HPMC [9].
The pure copolymer had two main stages of
4000 3500 3000 2500 2000 1500 1000 500
degradation, stages 2 and 3 in Table 1, with Tmax at
Wavenumber (cm-1) 368  C and 483  C. Stages 2 and 3 correspond to the
Fig. 1. FTIR spectra for the pure components and HPMC/P(VP-co- degradation of vinyl acetate (26.3% of weight loss) and
VAc) blends. vinylpyrrolidone (55.7% of weight loss), respectively.
24 C.M. Zaccaron et al. / Polymer Degradation and Stability 90 (2005) 21e27

100 significant weight loss (24.9%) being observed in stage 3,

P(VP-co-VAc)/HPMC although 17% weight loss was observed in stage 4
100/0 (Table 1).
80 70/30 Considering the second stage of degradation, the
50/50
30/70 thermogravimetric analysis suggests that the blend with
60 0/100 70% HPMC is more thermally stable than the pure
TG ( )

components and the blends with 50% and 30% HPMC.

40 This is confirmed by the Tmax of 407  C. On the other
hand, the analysis of stages 3 (for P(VP-co-VAc)) and 4
(for the blend with 30% HPMC), suggests a higher
20 stability for these systems in comparison with the pure
HPMC and other blends.
A
0
200 250 300 350 400 450 500 550 600 3.3. Kinetic parameters
Temperature (οC)
The apparent activation energies of the pure compo-
P(VP-co-VAc)/HPMC nents and the blends versus the weight-loss fractions
100/0 (a) are shown in Fig. 4. In general, high E-values
70/30 (O100 kJ molÿ1) suggest a degradation mechanism asso-
50/50
30/70 ciated with the random scission of strong bonds in the
0/100 polymeric chain, reflecting the existence of multiple
DTG (a.u.)

competing steps in the degradation process [17,25]. This

behaviour was clearly observed for pure P(VP-co-VAc)
and blends with 30, 50 and 70% HPMC. However, in pure
HPMC, E remains practically constant (z104 kJ molÿ1)
suggesting that the degradation occurred by scission of
weak bonds of the chain. The E-value of pure HPMC is
B in agreement with the value (112 kJ molÿ1) determined by
Li et al. [8] using the Friedman method. It is interesting to
200 250 300 350 400 450 500 550 600
observe that the E-value for HPMC (which is a cellulose
Temperature (οC) derivative) is considerably lower than the E-values 182,
Fig. 3. Thermogravimetric (A) and derivatives (B) curves for the 230 and 232 kJ molÿ1 reported in the literature for
systems HPMC/P(VP-co-VAc) at a heating rate of 10  C minÿ1. cellulose, carboxy methylcellulose and methylcellulose,
respectively [9,10]. This behaviour suggests a dependence
of E with the structure of the polymer. For the blend with
These results agree with the literature which describes 70% HPMC, E increased from 100 to 150 kJ molÿ1 with
that PVAc suffers deacetylation in the temperature the variation of a from 0.22 to 0.65. In the blend with 50%
range 160e400  C [24] and that degradation of PVP HPMC, E was practically constant (117 kJ molÿ1) up to
occurs in the temperature range 400e530  C [17]. a Z 0.5, increasing to ca. 185 kJ molÿ1 at a Z 0.6.
For the blends with 70% and 50% of HPMC, the In blends with 30% HPMC and pure P(VP-co-VAc) E
degradation is higher in stage 2, with 71.1% and 61.6% was determined considering stages 2 and 3 (Table 1). In
of weight loss, respectively. However, blends with 30% stage 2, the E-values increased from 125 to 155 kJ molÿ1
HPMC showed four stages of degradation with the most and 115 to 130 kJ molÿ1 for the blend with 30% HPMC

Table 1
Thermogravimetric parameters for the HPMC/P(VP-co-VAc) system
HPMC/P(VP-co-VAc) (% wt) Stage 2 Stage 3 Stage 4 Residual weightc (%)
a b a b a
T2 M2 T3 M3 T4 M4b
100/0 393 77.3 e e e e 11.3
70/30 408 71.1 475 6.0 e e 16.5
50/50 405 61.6 468 12.4 e e 17.5
30/70 365 19.8 411 24.9 481 17.0 14.3
0/100 367 26.3 483 55.7 e e 5.5
a
Temperatures of maximum degradation rate (  C).
b
Percentage weight loss in each stage of degradation.
c
Residual weight at 600  C.
 C.M. Zaccaron et al. / Polymer Degradation and Stability 90 (2005) 21e27 25

1643 cmÿ1 (C]O) [26] and 1066 cmÿ1 (CeOeC)

200 (Fig. 5A). After heating (393 and 500  C), the band at
2904 cmÿ1 (scission of the glucose ring) disappeared
180 indicating the formation of unsaturated products associ-
ated with the bands at 1633 and 1560 cmÿ1 [27,28]. The
E (kJ mol-1)

160 band at 1066 cmÿ1 also disappears suggesting the

formation of alcohol structures as confirmed by the band
140
at 3444 cmÿ1.
The solid residues of P(VP-co-VAc) (Fig. 5C) were
analysed at four different temperatures. At 250  C,
120
absorption bands at ca. 3500 cmÿ1 (OeH stretching),
1745 and 1664 cmÿ1 (C]O of PVAc and PVP, re-
100 spectively), 3000e2800 cmÿ1 and 1390 cmÿ1 (CeH
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 stretching) and 1446 cmÿ1 (CeN stretching), were
Weight-Loss Fraction (α) identified. On increasing the temperature (368  C) the
Fig. 4. Plots of activation energy versus weight-loss fraction for pure
band at 1745 cmÿ1 associated with the PVAc carbonyl
components and HPMC/P(VP-co-VAc) blends: (-) 100/0; (B) 70/30; group initially disappeared. The band related to the
(<) 50/50; (+) 30/70 and (>) 0/100. carbonyl group of PVP at 1664 cmÿ1 shifted to
1657 cmÿ1, probably due to the PVAc degradation
which may affect the copolymer structure. At 483  C,
and P(VP-co-VAc), respectively, with the increase in the
which is the degradation temperature of PVP, a band
weight-loss fraction. In stage 3, the E-value for the blend
associated with the carbonyl group at 1666 cmÿ1 was
with 30% HPMC increased to ca. 205 kJ molÿ1 (a Z 0.6)
observed, indicating that the scission of the NeC]O
decreasing to ca. 190 kJ molÿ1 at a Z 0.75. For the same
bonds still did not occur. The scission of the main chain,
stage, the E-values for P(VP-co-VAc) decreased from
including the PVP monomeric unit, produced unsatu-
170 kJ molÿ1 (a Z 0.55) to 150 kJ molÿ1 at a Z 0.85. For
rated structures characterized by the band at 1635 cmÿ1
the PVAc (polyvinyl acetate) deacetylation reaction
which appeared at 600  C [17].
E-values in the range 215e228 kJ molÿ1 have been
For the HPMC/P(VP-co-VAc) (50/50) blend practi-
described in the literature [19]. For the degradation
cally the same absorption bands (with a small wave-
of PVP (polyvinyl pyrrolidone) E-values in the range
number shift) of the pure components were observed at
170e200 kJ molÿ1 have been determined [17]. The lower
250  C (Fig. 5B). However, while the bands at 1738 and
E-values for P(VP-co-VAc) in comparison with the
1666 cmÿ1 associated with the carbonyl group of PVAc
copolymer components (PVAc and PVP) suggest a de-
and PVP disappeared, the band at 1442 cmÿ1 related to
pendence of E on the polymer structure. However, the
CeN stretching, and new bands at 1647, 1562 and
E-values were higher for blends with 30% HPMC and
1414 cmÿ1, were observed. The band at 1647 cmÿ1 may
P(VP-co-VAc), when compared with pure HPMC and
be associated with the ester formation as a consequence
blends with 50% and 70% HPMC. This behaviour is in
of the scission of the NeC]O bonds, as described in the
agreement with the Tmax of 483  C for the copolymer in
literature for pure PVP [17]. The bands at 1633, 1562
stage 3 and the Tmax of 481  C for the blend with 30%
and 1414 cmÿ1 which are all present at 600  C, must be
HPMC in stage 4 of the degradation (Table 1). At the
related to carbonecarbon double bonds associated with
same time, the E-values for the blend with 30% HPMC
unsaturated structures and char formation [29].
and P(VP-co-VAc) also suggest that the degradation
The volatile gas products for HPMC at a Tmax of
mechanism is associated with the random scission of
393  C, shown in Fig. 6, are associated with alcohol
strong bonds in the polymeric chain.
formation (OeH stretching at 3700 cmÿ1), CeH stretch-
ing (3000e2800 cmÿ1), CO2 (2370e2340 cmÿ1, 670 cmÿ1),
3.4. Infrared spectroscopy CO (2175 cmÿ1), aldehyde formation (C]O deformation
at 1750 cmÿ1) and CeOeC (1000e1100 cmÿ1). The above
In order to analyse the products of the degradation products are in full agreement with the decrease in intensity
reactions, two kinds of FTIR measurements were of the bands observed in Fig. 5A at 393  C.
performed for pure components and blends with 50% For pure P(VP-co-VAc), analysed at 483  C, it was
HPMC, considering: (i) solid residues before and after observed that some different products evolved from the
the weight loss at Tmax, and (ii) volatile gas products degradation reaction. For example, the formation of
collected at Tmax. NH3 is confirmed by the absorption bands at 970, 990
Before degradation (ca. 200  C) pure HPMC had and ca. 3600 cmÿ1, which is to be expected as a gas
residues associated with absorption bands at 3440 cmÿ1 product evolved from the degradation of PVP. Acetic
(OeH stretching), 2904 cmÿ1 (CeH stretching), acid evolved from the VAc unit as confirmed by the
26 C.M. Zaccaron et al. / Polymer Degradation and Stability 90 (2005) 21e27

200oC 393oC

1643
2904 1066 2175
393oC 3440
Transmittance (a.u)

Transmittance (a.u.)
3700 2370 1750
405oC
1125

1616
500oC 3419
483oC

1760
3444 1633 1560 3000 1427
A 1745
4000 3500 3000 2500 2000 1500 1000 500 4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cm-1) Wavenumber (cm-1)
Fig. 6. FTIR spectra for the volatile products evolved during thermal
250oC degradation at Tmax of: (A) HPMC at 393  C, (B) 50% HPMC at
405  C and (C) P(VP-co-VAc) at 483  C.
2929 1738
405oC 1666 1442
Transmittance (a.u..)

products related to amides is confirmed by the C]O

468oC 1647 1415 deformation at 1760 cmÿ1.
The HPMC/P(VP-co-VAc) (50/50) blend, analysed at
405  C, shows the same evolved products present in the
1414 degradation of the pure components, similarly to the
1633
600oC 1562 behaviour observed above for the solid residues.

1633 1414
1562
B
4000 3500 3000 2500 2000 1500 1000 500 4. Conclusions
Wavenumber (cm-1)
The HPMC and P(VP-co-VAc) miscibility was con-
250oC
firmed by thermal analysis and infrared spectroscopy.
1664 The behaviour concerning the absorption bands in the
1745 FTIR spectra and the variation of Tg suggests inter-
368oC 2961 actions via hydrogen bonding between the components.
Transmittance (a.u.)

1446
The profile of the thermogravimetric curves and
1657 number of degradation stages were dependent on the
483oC percentage of copolymer present in the blend. According
to the Tmax, the blend with 30% HPMC and pure P(VP-
co-VAc) was the most thermally stable systems. For the
same systems the activation energy values (E ) increased
600oC 1666
to ca. 190 and 170 kJ molÿ1, respectively, confirming
1635 the higher thermal stability. Considering the activation
C energy values of the pure components and blends,
4000 3500 3000 2500 2000 1500 1000 500 a degradation mechanism associated with a random
Wavenumber (cm-1) scission of the chain occurred.
The FTIR spectra of the solid residues from thermal
Fig. 5. FTIR spectra for the residues during thermal degradation at
degradation of HPMC indicated the formation of
different temperatures: (A) HPMC, (B) HPMC/P(VP-co-VAc) (50/50)
and (C) P(VP-co-VAc). alcohol structures and unsaturated hydrocarbons as
reaction products. For the same system CO2, CO,
characteristic band at ca. 3000 cmÿ1 and C]O de- aldehydes, alcohols and ethers were detected as volatile
formation at 1745 cmÿ1. The low intensity of the band products. Unsaturated structures were also observed as
associated with CO2 suggests that the gas evolution may solid products associated with the degradation reaction
be suppressed in this system, in agreement with other of P(VP-co-VAc). For this system volatile products such
systems described in the literature [30]. Finally, evolved as, acetic acid, CO2, CO and NH3 were detected. For the
 C.M. Zaccaron et al. / Polymer Degradation and Stability 90 (2005) 21e27 27

blend HPMC/P(VP-co-VAC) (50/50) the formation of membranes in the pervaporation of ethanol-ethyl tert-butyl ether
the same solid and volatile products detected for the mixtures. Simplified model for flux prediction. Sep Purif Technol
1998;13:237e45.
pure components, was observed. [15] Kwok TSH, Sunderland BV, Heng PWS. An investigation on the
influence of a vinyl pyrrolidone/vinyl acetate copolymer on the
moisture permeation, mechanical and adhesive properties of
Acknowledgements aqueous-based hydroxypropyl methylcellulose film coatings.
Chem Pharm Bull 2004;52:790e6.
[16] Rosiak J, Olejniczak J, Pekala W. Fast reaction of irradiated
This research was supported by Conselho Nacional
polymers. 1. Cross-linking and degradation of polyvinylpyrroli-
de Desenvolvimento Cientı́fico e Tecnológico (CNPq), done. Radiat Phys Chem 1990;36(6):747e55.
Coordenação de Aperfeiçoamento de Pessoal de Nı́vel [17] Bianco G, Soldi MS, Pinheiro EA, Pires ATN, Gehlen MH,
Superior (CAPES) and Federal University of Santa Soldi V. Thermal stability of poly(N-vinyl-2-pyrrolidone-co-
Catarina (Universidade Federal de Santa Catarina e methacrylic acid) copolymers in inert atmosphere. Polym Degrad
Stab 2003;80:567e74.
UFSC), Brazil.
[18] Zulfiqar S, Ahmad S. Thermal degradation of blends of PVAC
with polysiloxane-II. Polym Degrad Stab 2001;71:299e304.
[19] Sivalingam G, Karthik R, Madras G. Blends of poly(epsilon-
References caprolactone) and poly(vinyl acetate): mechanical properties and
thermal degradation. Polym Degrad Stab 2004;84:345e51.
[1] Qiu Z, Komura M, Ikehara T, Nishi T. Miscibility and [20] Ozawa T. A new method of analyzing thermogravimetric data.
crystallization of biodegradable blends of two aliphatic polyesters. Bull Chem Soc Jpn 1965;38:1881e6.
Poly(3-hydroxybutyrate-co-hydroxyvalerate) and poly(butylenes [21] Hiremath AC, Sherigara BS, Prashantha K, Rai KS, Kumar SP.
succinate) blends. Polymer 2003;44:8111e7. Studies on the miscibility of hydroxypropyl methylcellulose and
[2] Van de Velde K, Kiekens P. Biopolymers: overview of several polyvinylpyrrolidone blends. Indian J Chem Technol 2002;9:
properties and consequences on their applications. Polym Test 312e5.
2002;21:433e42. [22] Chatlapalli R, Rohera BD. Study of effect of excipient source
[3] Sakellariou P, Hassan A, Rowe RC. Plasticization of aqueous variation on rheological behaviour of diltiazem HCl-HPMC wet
poly(vinyl alcohol) and hydroxypropyl methylcellulose with masses using a mixer torque rheometer. Int J Pharm
polyethylene glycols and glycerol. Eur Polym J 1993;29:937e43. 2002;238139e51.
[4] Coma V, Sebti I, Pardon P, Pichavant FH, Deschamps A. Film [23] McPhillips H, Craig DQM, Royall PG, Hill VL. Characteriza-
properties from crosslinking of cellulosic derivatives with a poly- tion of the glass transition of HPMC using modulated
functional carboxylic acid. Carbohydr Polym 2003;51:265e71. temperature differential scanning calorimetry. Int J Pharm 1999;
[5] Fuller CS, MacRae RJ, Walther M, Cameron RE. Interactions in 180:83e90.
poly(ethylene oxide)ehydroxypropyl methylcellulose blends. [24] McNeill IC, Ahmed S, Memetea L. Thermal-degradation of vinyl
Polymer 2001;42:9583e92. acetate-methacrylic acid copolymer and the homopolymers. 2.
[6] Ford JL. Thermal analysis of hydroxypropylmethylcellulose and Thermal-analysis studies. Polym Degrad Stab 1995;48:89e97.
methylcellulose: powders, gels and matrix tablets. Int J Pharm [25] Barreto PLM, Pires ATN, Soldi V. Thermal degradation of edible
1999;179:209e28. films based on milk proteins and gelatin in inert atmosphere.
[7] Pekel N, Yoshii F, Kume T, Güven O. Radiation crosslinking of Polym Degrad Stab 2003;79:147e52.
biodegradable hydroxypropylmethylcellulose. Carbohydr Polym [26] Yang G, Zhang L, Peng T, Zhong W. Effects of Ca2C bridge
2004;55:139e47. cross-linking on structure and pervaporation of cellulose/alginate
[8] Li X, Huang M, Bai H. Thermal decomposition of cellulose blend membranes. J Membr Sci 2000;175:53e60.
ethers. J Appl Polym Sci 1999;73:2927e36. [27] Boon JP, Pastorova I, Botto RE, Arisz PW. Structural studies on
[9] Zohuriaan MJ, Shokrolahi F. Thermal studies on natural and cellulose pyrolysis and cellulose chars by PYMS, PYGCMS,
modified gums. Polym Test 2004;23(5):575e9. FTIR, NMR and by wet chemical techniques. Biomass Bioenergy
[10] Nada AMA, Hassan ML. Thermal behavior of cellulose and 1994;7:25e32.
some cellulose derivatives. Polym Degrad Stab 2000;67:111e5. [28] Souza AC, Pires ATN, Soldi V. Thermal stability of ferrocene
[11] Sivalingam G, Madras G. Oxidative degradation of poly(vinyl derivatives and ferrocene-containing polyamides. J Therm Anal
acetate) and poly(epsilon-caprolactone) and their mixtures in 2002;70:405e14.
solution. Chem Eng Sci 2004;59:1577e87. [29] Soares S, Camino G, Levchik S. Effect of metal carboxylates on
[12] Villetti MA, Crespo JS, Soldi MS, Pires ATN, Borsali R, Soldi V. the thermal decomposition of cellulose. Polym Degrad Stab
Thermal degradation of natural polymers. J Therm Anal 1998;62:25e31.
2002;67:295e303. [30] Vieira I, Severgnini VLS, Mazera DJ, Soldi MS, Pinheiro EA,
[13] Soldi V. Stability and degradation of polysaccharides. In: Pires ATN, et al. Effect of maleated propylene diene rubber
Dumitriu S, editor. Polysaccharides: structural diversity and (EPDM) on the thermal stability of pure polyamides and
functional versatility. 2nd ed. p. 395e409. polyamide/EPDM and polyamide/poly(ethylene terephthalate)
[14] Nguyen Q, Clément R, Noezar I, Lochon P. Performances of blends: kinetic parameters and reaction mechanism. Polym
poly(vinylpyrrolidone-co-vinyl acetate)-cellulose acetate blend Degrad Stab 2001;74:151e7.

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