A Kinetic Investigation of the Copolymerization of Acrylonitrile and Vinyl Acetate in Bulk

Dev. Chem. Eng. Mineral Process., 6(3/4), pp.153-170, 1998.

A Kinetic Investigation of the

Copolymerization of Acrylonitrile and

Vinyl Acetate in Bulk

N.T. McManus, A. Penlidis* and G.L. Rempel Department of ChemiCQl Engineering, University of Waterloo

Waterloo, Ontario N2L 3G1, CANADA

The free radical copolymenm'on, initiated by 2, 2' azo-bis- isobutyronitn'le (AIBN,

of acrylonitrile (AN) and vinyl acetate WAC) in bulk has been 4xamined. Reactivity

ratios were evaluated using the error in variables model (EVM). In addition, full

conversion range experimenrnents were u n d e m , which examined polymenm'on rate,

molecular weight deve lopm and copolymer composition with respect to the &em

of feed composition, initiator concentration and temperature.

Keywords: Acryhnitrile: vinyl acetate; reactivity ratios; copolymerization; kinetics.

Introduction and Literature Review A wider ah to produce novel elastomerk materials equivalent to hydrogenated nitrile

butadiene rubber (HNBR) provided the stimulus for this study. HNBR is produced

by the selective hydrogenation of the C-C double bonds in acylonitrile butadiene

rubber (NBR) [l]. It is essentially a copolymer of ethylene and AN with small

proportions of butylene and residual double bond. Unfavourable reactivity ratios mean

that significant copolymerization cannot be achieved for these monomers unless very

high pressures of ethylene are used. Moreover, at such conditions other difficulties

regarding inhomogeneity are also encountered [2].

* Author for correspondence.

153

N.T. McManw, A. Penlidis and G.L Rempel

Potentially, a polymer with physical properties similar to those of HNBR could

be obtained by the terpolymerization of ethylene, AN and VAc. Indeed, previous

research has examined this system and achieved only limited success with the

polymerization Carried out in bulk at ultra-high ethylene pressures [3]. The result

indicated that to produce successfully such a polymer, the difficulties encountered

with traditional bulk methods would have to be bypassed by using alternate

polymerization methodology. One possible option is to utilise semi-batch emulsion

methodology.

A meaningful study of such a complex multicomponent polymerization has to be

approached systematically in order to obtain a full understanding of the system. This requires that all levels of the system be examined in a logical fashion, i.e. one

examines iirst the homopolymerizations, then copolymerization and finally the

multicomponent polymerization. Also the different possible polymerization media

should be examined stepwise, i.e. bulk, then solution and finally emulsion. This method breaks down the complete problem into its component parts which may be

then pieced together in order to rationalise the h d multicomponent system. This methodology has successfully been used for the examination of terpolymerization of

VAc with butyl acrylate and methyl methacrylate in a variety of media [4-61.

Breaking down the ANNAclethylene system into its components, the

homopolymerizations of all three monomers have been studied Ediry widely. The

copolymerization of ethylene (E) and AN has been attempted and is difficult using

standard free radical procedures because ultra-high pressures of ethylene are required to achieve significant levels of E in the copolymer [2,7]. The addition of aluminum

alkyls has been utilized to produce alternating copolymers of E and AN [ti]; however

this method cannot be adapted to produce random copolymers with higher levels of

E.

The ENAc copolymerktion has been the subject of several investigations and it

has been shown that the copolymerization may be tailored to produce any desired

copolymer composition at high pressures of E. Of direct relevance to our overall aim

is the work by Scott et al[9] which showed that ENAc copolymers, with moderately

154

Kinetic investigation of copolymerization of acrylonitrile and vinyl acetate

high E levels, could be produced under relatively low pressures of E by using semi-

batch emulsion methods.

Table I. Reported Reactivity Ratios for AN / VAc Copolymerizaton

r, Reference

Bulk

Bulk

Bulk

Bulk

Solution

Solution

Water

Emulsion

4.05

6.0

3.88

2.34

5.0 4.0

4.2

2.7

0.78

0.06

0.07

0.009

0.044

O.O7(a) 0.008(b)

0.05

0.05

0.025 r, is for AN; r, is for VAc. a: Finemann Ross method. b: Extrapolation method.

ANNAc copolymerization has been the subject of a number of studies over the

years largely because of the commercial value of the products in the manufacture of

acrylic and carbon fibres. However, a detailed systematic study of the kinetics of the

process has not been undertaken. Early evaluation of the reactivity ratios in bullc

was made by Mayo et al. [lo] and Alfrey et al. [ll]. In a study describing dye

sensitized photopolymerization of ANNAc in bulk, Taniyama and Oster [12] also

evaluated the reactivity ratios. These authors used curve fitting techniques as opposed

to standard linear methods to determine the final values and it is noteworthy that the

result obtained for r, wk) differed substantially from those of Mayo and Alfiey (see

Table 1). In a series of studies Dorokhina et al. [13-161 examined the

copolymerization with a view to optimi7f! the process for the production of polymers

for use in fibre manufacture. They examined the polymerization in emulsions and

DMF solutions initiated by peroxides. Evaluations of the reactivity ratios were made

and the implications of changing monomer feed levels and the distribution of

155

N.T. McManw, A. Penlidis and G.L. Rempel

monomers in two-phase systems were examined with regards to kinetics and product

composition. Guyot et al. [17,18] looked at the polymerization, as part of a study

examining copolymerizations of various monomers, using gas liquid chromatography

as a means to determine radical concentration. The authors obtained reactivity ratios

using these data and presented two sets of estimates. One was obtained using the

Finemann-Ross method and the second used an extrapolation method (presumably

non-linear). Significant differences in the value of r, were obtained (see Table 1)

from the different methd , hinting at the inadequacies of the traditional method for

determining reactivity ratios.

Studies have also been conducted of the copolymerization in the presence of Lewis

acids as a means of altering the effective reactivity ratios of the system. Chien [19]

has described the use of AN-ZnC1, complex which copolymerized spontaneously with

VAc leading to alternating copolymer. Mokhtar et al. [20] have studied the use of

SnC1, in conjunction with AIBN initiation. Addition of SnCl, led to increased rates

particularily in feeds with high proportions of AN. Increasing amounts of SnC1, also

altered the effective reactivity ratios leading to an increase in r, . The use of Ziegler-

Natta type catalysts has also been examined. Sharma et al. [21] have studied

ANNAc copolymerization in the presence of Co(AcAc),/AlF!h. They examined the

kinetics of the system and the composition of products. Similarities to the AIBN

initiated polymerization were observed suggesting that anionic and radical propagation

were concurrent in the system [21]. This was confinned by a decrease of the rate in

the presence of radical inhibitors.

Monomer sequence distributions have been examined, Using I3C NMR, for

copolymers obtained by different initiation methods [22]. It was observed that

polymerizations using AIBN initiator or the Co(AcAc),/AEt, produced copolymer

with similar diad and triad distributions and it was confinned that ZnC1,-promoted

products gave rise to largely alternating polymer. Recently, further studies have

examined ANNAc copolymer microstructure using '% NMR [23-251. The data obtained from compositional analysis have been used to determine effective reactivity

ratios for copolymerization in emulsions [23] and for the polymerization in a water

156


slurry 124,251. The use of spectroscopic techniques to examine this system is

ongoing. Other recent work has investigated primary radical interactions between

initiator and monomers using ESR [26,27]. The previous studies give insights into certain details of the copolymerization of

A ” A c . However, there are no kinetic studies and the different estimates of

reactivity ratios are contradictory, particularly for r, (see Table 1). The current

study describes evaluation of reactivity ratios for the system using statistically valid

methods, as described by Dub6 et al. [28]. It also describes the kinetics, at selected

monomer feed levels, initiator concentrations and temperature levels, over the full

conversion range.

Experimental Details

Reagent Purification Monomers, obtained from Aldrich Chemical Company, were distilled under reduced

pressure, not more than twenty-four hours prior to use. The initiator, 2,2’-azo-

bisisobutyronitrile (AIBN) (from Polysciences Inc.) was recrystallized three times

from absolute methanol. Solvents (acetone, ethanol, methanol, d6-DMSO and chloroformd) were used as received without further purification.

Reactive Ratio Experiments Experiments were carried out in glass ampoules (capacity approx 10 ml). Stock

solutions of the monomer and initiator were prepared by weighing appropriate

amounts of reagents. Aliquots were then pipetted into ampoules. Degassing of the

monomer solution was done by several vacuum-fieeze-thaw cycles. The ampoules

were then flame-sealed and stored in liquid nitrogen until ready for use.

Polymerizations were carried out by placing the ampoules in a thermostatically

controlled water bath (fitted with a shaker). The ampoules were removed from the

water bath after a recorded time interval. They were weighed immediately and then

frozen by submersion in liquid nitrogen. Thereafter the ampoules were broken and

the contents poured into previously weighed beakers containing a ten-fold excess of

157

N.T. McManus, A. Penlidis and G.L. Rempel

ethanol. The empty ampoules were weighed when dry. The copolymer obtained was

dried to constant weight in a vacuum oven at approx 50°C. Conversion levels were

then determined by comparing the weights of products to the weights of the monomer

feeds in the ampoules. Polymer compositions were determined primarily from 'H NMR spectra of the copolymers (see below for more details).

The design of experiments canied out for reactivity ratio determination employed

the Tidwell and Mortimer (1965) D-optimal criterion [29]. Initial guesses of r, = 3.1

and r, = 0.1 were chosen after assessment of literature values. The monomer feeds

were thus fl, = 0.4 and y;o = 0.05 (subscript 1 denotes AN). An additional feed

level was chosen to give further information; this was = 0.1. In the

experiments, four replicate polymerizations were run to low conversion at each

monomer feed level with an AIBN concentration of 0.05 M and a reaction

temperature of 40°C.

Reactivity ratios obtained from this first set of experiments did not give

satisfactoty results. The reason was probably that the chosen monomer feeds were

not optimal. Thus, a further reactivity ratio evaluation was undertaken using

monomer feeds determined on the basis of the values obtained from the initial

experiment. The values of

As a supplement, a third feed level was run to low conversions with

for the second examination were ca 0.004 and 0.2.

of 0.007.

Full Conversion Range Studies The full conversion range experiments were carried out using ampoules in a manuer

similar to that described for the reactivity ratio studies. The set of full conversion

range experiments was primarily a Z3 factorial design which examined the effects of: monomer feed composition (cm = 0.02 and 0.007), temperature (40 and m), and initiator concentration ( 0.05 and 0.1 molL ). Additional runs were conducted

which examined in more detail the polymerization at the low conversion region using

the same two monomer feeds at 60% and 0.025 and 0.05 moln initiator.

158


Characterization Copolymer Composition The primary method for compositional analysis was 'H NMR spectroscopy. 13C{'H}

and elemental analysis were used also as supplementary analyses for selected samples.

'H NMR Spectroscopy

'H NMR spectra were recorded using a Bruker AM 300 spectrometer. The

composition of the copolymers was determined from the 'H-NMR spectra of samples

dissolved in CDCl, or D6-DMSO (depending on the level of AN in the copolymer).

Spectra were run Using a relaxation delay of 7 sec. Copolymer composition was

calculated from integrals of the signal at approx 2.4 ppm, assigned to the -CU(CN)-

of AN, and of the signal at approx 5 ppm from the -CH(OAc)- of VAc.

NMR Spectroscopy Compositions were measured by comparing peak areas for CN signals at approx 120

ppm and for CH&02 at approx 170 ppm. An INVGATE pulse sequence was used

with a pulse delay of 7%.

Gel Pernation Chromatography (GPC) GPC was used to measure approximate molecular weight averages. The system was

equipped with a bank of three columns, ranging in size from 103 to lo6 Angstroms.

Chromatographic grade tetrahydrofuran (THF) was the mobile phase and all samples

were dissolved in THF for the measurements. Samples were filtered through 45pm filters to remove any insoluble gel. Polymer elution was detected using a Waters

R401 differential refractive index @RI) detector. Average molecular weights were

calculated from elution profiles at room temperature, Using in-house developed

s o h a r e with polystyrene standards calibration data 1301.

159


Discussion Reactivity Ratio Estimation Table 1 presents reactivity ratio values for the A " A c system from previous reports.

The wide range of values for r, and r, is clearly illustrated. The most marked difference lies in the value of r, which has been estimated at between 0.008 and

0.07. The reasons for this variation may be due to analytical problems but are largely

the resuit of deficiencies in the traditional linear methods for determining reactivity

ratios [31].

Analysis of data in this study was performed using a program called RREVh4

which estimates reactivity ratios using the Mayo Lewis equation in conjunction with

measured feed- and product polymer- composition data. The program considers the

measurement error in both the dependent (copolymer composition) and independent

(monomer feed composition) variables [28]. Since the measurement error incurred for

both variables must be known (or estimated), a more accurate estimate of the true

values and associated uncertainties of the reactivity ratios can be obtained. T&k 2. Rcac~ivily Ratio f i t i m ' o n Preliminary Study.

fa Conversion FAN

0.0519 0.31 0.573

0.0519 0.31 0.561

0.0519 0.34 0.598

0.0516 1.5 0.575, 0.54'

0.0516 1.5 0.576

0.0516 1.6 0.595, 0.572b

0.1Ooo 1.3 0.669, O.63gb

0.1Ooo 1.2 0.661

0 . 1 m 1.2 0.676, 0.64'

0.3959 0.39 0.833

0.3959 0.37 0.836

0.3959 0.41 0.861 Eompositions were obtained from 'H NMR unless otherrvlse noted. a: Values obtained from elemental analyses. b: Values obtained using ''C{'H) NMR.

160


Table 2 shows results from the prelimimq study. The copolymer compositions

along with the conversion levels attained for the different ampoule experiments are

presented. It should be noted that polymer precipitation during the course of

polymerization was observed in all experiments, even at very low conversion levels,

and this was true for all cases reported below, regardless of monomer ratios in the

feed.

RREVM was used to analyse the data presented in Table 2. The error values used

in the calculation were those used for earlier similar studies [5,32] (0.0055% for feed

composition and 5 % for copolymer composition). The results from the analysis gave

point estimates of rl = 8.2 and r, = 0.002. The 95% joint confidence interval

from the calculations included values of r, that were less than zero. The observed high

degree of uncertainty in the results probably stemmed from the fact that the measured

reactivity ratios were significantly different from those used as initial estimates in the

Tidwell Mortimer equations. Hence, the selected momomer feeds could not be

considered "optimal" for determining reliable reactivity ratio estimates. New

monomer feeds were determined using the Tidwell Mortimer criterion with the r, and r, values obtained from the pre]iminarv study. This resulted in new levels for

Gm = 0.004 and 0.2. The results from these experiments are presented in Table 3.

It was determined that although the actual total conversion of monomers for fom =

0.004 was low, there would be considerable drift in the relative level of AN in the

feed. Therefore, a third level of feed was examined (.tbAN = 0.007). The conversion

level for this feed level was only 0.18 96 and so drift in fm was minimised.

Reactivity mtios were once again evaluated Using RREVh4: first by using data

only from the samples where cm = 0.2 and 0.004. A second analysis was made,

using data from = 0.2 and 0.007. Finally, data from all three levels were used

in the calculation.

161


Table 3. Reactivity Ratio Estimation: Second Data Set.

CAN Conversion FAN (%>

O.Oo40

O.Oo40

O.Oo40

0.0040

0.2028

0.2028

0.2028

0.2028

0.0070

0.0070

0.0070

0.0070

1.7

1.5

1.5

1.8

4.8

4.6

4.8

4.4

0.18

0.18

0.18

0.18

0.231

0.250

0.243

0.221, 0.211*

0.711

0.703

0.719

0.742

0.336

0.328

0.324

0.335

For NMR analysis: samples with FAN < 0.4 were dissolved in CDC13 and samples with FAN > 0.7 dissolved in d6-DMSO. a: NMR was run in d6-DMSO.

The error values used for this series of evaluations were 0.1% for the feed

composition and 5 % for the copolymer composition. The value for the feed

composition error was higher than that used in earlier studies; this was to account for

the relatively higher error in weighing AN in feeds where f& = 0.004 and 0.007,

and also to account for the drift in feed composition which must occur in these

experiments even though conversion of monomer was minimid.

The results from these analyses are presented in Table 4 and little difference was

observed in the values obtained for r, and r, in the three different calculations. The

95 % joint confidence intervals from all three are also similar as shown in Figure 1.

162


Table 4. RREVMAnalyses of Data in Table 3.

0.2, 0.004 6.49 0.0094

0.2, 0.007 6.42 0.0079

0.2. 0.004. 0.007 6.61 0.0089

Figure 2 shows the expected copolymer composition as predicted by the Mayo-

Lewis model using rl = 6.61 and r, = 0.0089 (solid line) with secondary lines

calculated using the high and low values for r, from the 95% confidence interval.

The experimental data from this study are also shown in Figure 2.

i 0.015

0.005 4 r, 6.48. re 0.0084 r, 6.42. T. 0.0079 rt 6.61. r, 0.0088

0.000

rl

Figure I . Reactivity Ratios. Final Analysis. 95 % Posterior Probability Contours.

mom Erpsrirnmw data. mayo Lari. burr r, - 6.61. r, = 0.009. - - uayo Lcri. m e r, = 5.28. r. = 0.000. yay0 Lcrk C w e r, = 'I.95. r, = 0.008.

o.2

0.0 0.0 0.2 0.4 0.6 0.8 1.0

f AN

Figure 2. Mayo Lewis Model Curves Along with Experimental Data Points.

Full Conversion Erperinents Full conversion range experiments in bulk were carried out to examine different

factors influencing the copolymerization. The primary experimental design was a 23

factorial design using two levels for three variables: monomer feed composition,

163


initiator concentration and temperature. The copolymerization experiments examined

the effect of the three variables on the rate of monomer conversion, copolymer

composition and molecular weight averages of products (here the results show only approximate trends). The level of AN in the monomer feed was dictated by a

constraint that the AN level in the initial stages of polymerization should be controlled

between an upper level of 0.45 and a lower level of 0.3. Using the Mayo Lewis

model with the reactivity ratios obtained, the initial levels of AN expected to give

these copolymer compositions are Gm = 0.02 and 0.007. The temperatures

examined were 40°C and 60°C and initiator concentrations were 0.05 and 0.1

m o l L A secondary design addressed in more detail the polymerization at the low

conversion (< 10%) region. It examined the effects of monomer feed and initiator

concentration at the following levels: Gm = 0.007 and 0.02, and initiator

concentration = 0.025 and 0.05 m o l L Observations from these runs are

summarized below and, as supplementary inforination, full tabulated details of the

experimental results obtained are available upon request from the authors (A.P.).

The polymerkition rate profiles (see Figures 3 and 4) are characterized by an

initial "slow" phase followed by a relatively rapid reaction phase (approx 11 times

faster than the initial "slow" phase). It is apparent from the conversion curves that the

point at which the polymerization takes off is dictated by all the experimental

variables in the design; including the initial level of AN in the feed.

* I 0 0

0

0

I

+

0 - 0 +=

O +I +

O

ooooo C,-O.OZO. -0.05U. ooooo C~=0.007. -0 .OSU. - o o o w tu=0.007. - 0 . l O U . +++++ fu=0.007. ==O.O§U.

0 11111 f,=0.020.

I .*:* a h = 0 0

0 I 0 500 1000 1600 2000

Time (minutes)

Figure 3. Reaction Rate P r O f i h at 40°C. Efea of Initiator Concentraton and Monomer Feed Ratio.

164


' O 0 1

0 o =

0 0 +

I

0 0

+ +

naooo fdN = 0.007, -m--m feAN = 0.007, ooooo f- = 0.020. ooooo f,,N = 0.020. +++++ fdw = 0.021,

figure 4. Reacn'on Rate Profiles at 60°C. Eflect of Initiator Concentrm'on and Monomer Feed Ratio.

Analysis of the copolymer composition data (see Figure 5) shows that the initial

stages of reaction are dominated by the polymerization of AN which is as expected

from consideration of the reactivity ratios. It may be calculated from composition

and conversion data that the AN is entirely consumed in these initial stages of reaction

(see Figure 6). Similar behaviour has been observed for the copolymerization of VAc

with butyl acrylate and methylmethacrylate [5 ] . All these systems exhibit large

differences between the reactivity ratio of the acrylate monomers and that of VAc.

Thus, copolymerization only takes place in the initial reaction stages and the latter

part of the reaction may be considered as a "virtual" homopolymerization of VAc.

Figure 5 also illustrates predicted composition vs conversion curves based on the

new reactivity ratios along with the experimentally obtained data at 60°C. It is

apparent that the copolymer composition data obtained are in agreement with

predicted values at both feed levels given an uncertainty in measurement of copolymer

composition of 5 % . This gives support to the reliability of the new reactivity ratio

N.T. McManw, A. Penlidis and G.L. Rempel

estimates for the copolymerization. It can also be seen that initiator concentration

does not affect copolymer composition. Selected samples obtained from runs at

40°C were also analysed and gave similar copolymer compositions ( not shown ) to

those shown in Figure 5

ooooo iu=0.007. I =0.05 Y. mmmmm iu=0.007. 1 -0.025 Y. ..-..I fu=0.020. 1-0.025 Y.

Uodel R s L c ions (replicate)

0.0

n conversion

E m 5. Dnj2 of Copolymer Composition. Temperature = 60°C.

1 00

80

C .-

60 0)

C V

z 4

40

U

20 we= I =0.025 M - [1]=0.05 M !d Total monomer conversion

figure 6. AN Consumption Relative to Overall Monomer Consumption. Temperature = 60°C. fAN = 0.02.

Figure 7 shows the effect of initiator concentration on the rates of polymerization at

low levels of monomer conversion. The ratio of the initial & for the two initiator

concentrations is 0.7, which is as expected from standard polymerization kinetics. The

effect of v-g initiator concentration on reaction rates may also be seen in Figures

3 and 4. The effect of temperature on reaction rates is illustmted in Figure 8. As expected, rates at 60°C are significantly higher than those at 40°C. Boiling of the

monomers in ampoules was observed during the rapid phase of reaction at 60°C,

prior to quenching. This suggested that non-isothermal behaviour could be a factor

in these experiments. It obviously stemmed from the extremely rapid rates of

polymerization at the corresponding conditions.

166


' O . O I 8.0

." 6.0 4 P

A .O

D

0 50 1W 150 200 time (minutes)

0

0 0

0 600 1WQ 1W t i e (minutes)

figure 7. Reaction Rates. Eflect of Initiator Concentrarion. Temperature

figure 8. Reaction Rates. Eflect of Initiator Concentration. Temperature

=wc. fAN = 0.02. =60"C. fAN = 0.02.

Cumulative molecular weight data were collected from selected samples. The

results are presented in Figures 9 and 10. Molecular weight averages show the

expected trends with respect to initiator concentration and temperature.

OEiwO 0 20 M 80

donversion

v I

I

I

sconversion

Figure 9. Trends in Copolymer Molecular Weights. Eflect of Initiator Molecular Weights. Eflect of Concentrm'on. Temperature = 60 "C. Temperature. [ D N J = 0.1 mlL.

figure 10. Trends in Copolymer

f-= 0.02.

167

N.T. McManw. A. Penlidis and G L Rempel

Increasing either the initiator concentration or the temperature leads to lower values

for aN and aw. The molecular weight profiles show rapid increase in aw as the

polymerization is dominated by VAc. This presumably stems from a high degree of branching which is well documented for VAc polymerization 1331.

Conclusions The studies reported here have elucidated the kinetics pertaining to the bulk

copolymerization of AN and VAc. Reactivity ratios have been determined using valid

non-linear estimation techniques. Kinetic studies over the full conversion range have

shown that there are essentially two phases over the polymerization. The first is a

copolymerization which continues until all AN in the monomer feed is consumed.

The latter part is a "virtual" homopolymerization of VAc. Our study represents the

first enamination of the copolymerization of these monomers over the full extent of

conversion in bulk. Further studies will examine the polymerization in other media

which are more appropriate to achieving the overall goal of terpolymerization of

ANNAcIE.

Acknowledgements Help from K. Afkhami with the experimental work at low conversion levels, and

financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada and the Ontario Centre for Materials Research (OCMR) are

gratefully acknowledged.

References

1. McManus, N.T. and Rempel, G.L. 1995. Modification of polymers. Catalytic hydrogenation and related reactions. J. Macromol. Sci., Revs. Mammol. Chem. Phys., a, 239-285.

2. Brackemann, H. and hback, M. 1989. Exima laser induced free radical copolymerization of ethylene and acrylonitrile. Makromol. Chem., l& ,3073-3084.

3. wlback, M. and Panter, K. 1993. Terpolymerization of cthcne, acrylonitrile and vinyl acetate.

4. Dub, M.A., Rilling, K. and Penlidis, A. 1991. A kinetic investigation of butyl aaylate. polymerization. J. App. Polymer Sci., fi 2137-2145.

5. Dube, M.A. and Penlidis, A. 1995. A systematic approach to the study of multicomponent polymerization kinetics-the butyl acrylatdmethyl methacrylaWviny1 acetate example: 1. Bulk

Maktomol. Ch., 194, , 2471-2481.

168

Kinetic investigarion of copolymerization of acrylonitrile and vinyl acetate

copolymerization. Polymer, 3, 587-598. 6. Dube, M.A. and Penlidis, A. 1995. A systematic approach to the study of multicomponent

polymerization Lin&cs-the butyl acrylate/me€hyl methacrylate/vinyl acetate example, 2. Bulk and solution terpolymerization. Macromol. Chem. Phys., m,, 1101-1 112.

7. Randall, J.C., Ruff, C.J, Kelchtermans M. and Gregory, B.H. 1992. Carbon-I3 Nh4R characterization of ethyleneacrylonitrile copolymers prepared by high pressure free radical polymerizations. Macromolecules, 25, 2624-2633.

8. Eisenbach, C.D., Bulow, U., Daum, U., Furderer, B., Schmidt, F.G. , Fischer, H. and Ulmschneider, D. 1986. Alterniende copolymere uber komplexie monomere. Angew. Makromol.

9. Scott, P.J., Penlidis, A. and Rempe4, G.L., 1996. EthyleneVinyl Acetate Semi Batch Emulsion Copolymerization: Use of Factorial Experiments for Improved Process Understanding. J. Polymer Sci, Polymer Chem., 3l, 2205-2230.

10. Mayo, F.R., Walling, C., Lewis F.M. and Hulse, W.F. 1948. Copolymerization. V. Some copolymerizations of vinyl acetate. J. Amer. Chem. Soc., 70, 1523-1527.

11. Alfrey, T., Bohrer, J., Haas, H.and Lewis, C. 1950. Experimental study of copolymerization. J. Polymer. Sci.,A, , 719-726.

12. Taniyama, M. and Oster, G. 1957. Dye-sensitized photopolymerization of acrylonitrile-vinylacetate copolymers. Bull Polymer Sci. lap., 30, , 856-859.

13. Dorokhina, I S . , Abkin, D. and Klmenkov, V.S . 1962. Copolymers of acryloniuile and vinyl acetate. Khim. Volokna, I, 49-54. CA 5 9 295611.

14. Dorokhina, I.S., Abkin, D. and Klmenkov, V.S. 1962. Studyofthecopolymerisationofacrylonitrile and vinyl acetate in connedion with the synthesis of fibrous materials. II. Fibre forming polymers of acrylonitrile and vinyl acetate. Khim. Volokna, 2, 16-21. CA 59: 6563c.

15. Dorokhina, IS., Abkin, D. and Klimenkov, V.S. 1962. Effect of distribution of monomers b e e n phases in emulsion copolymerization of acrylonitrile and vinyl acetate. Zh. Kolloidn, 24,549-553 CA 58: 8094h.

16. Dorokhina, IS., Abkin, D. and KLimenkov, V.S. 1963. Kinetics of copolymerization of acrylonitrile and vinyl acetate. Vyesokomolekul S d m , 5. 385-392. CA 59: 2956.

17. Guyot, A. 1975. New studies in radical copolymerization. J. Polymer Sci., Polymer. Symp., so,, 17- 32.

18. Guyot, A., Guillot, J. and Pichot, C. 1975. Determination of radical collcentrations in copolymerization. J. Mammol. Sci. Chem., A9,, 469481.

19. Chien , C.S.H. 1976. 1:l Alternating copolymer of acrylonitrile and vinyl acetateJ. Polymer Sci . , Polymer Chem, 14,2109-2120.

20. Mokhtar, S., Abdel-Aziz, S.M., Euchair, A. and Mostafa, B. 1989. Influnce of stannic chloride on the copolymerization behaviour of vinyl acetate with acrylontirile. Polymer. J., 2l, 99-102.

21. Shama, Y.N., Gandhi, V.G. and Bhardwaj, I.S. 1980. Investigations of the kinetics of copolymerization ofvinyl acetate with acrylonitrile by Co(acac),-Al(GH4,Catalyst system. J. Polymer Sci. Polymer Chem., l8,59-64.

22. Kalyanam, N., Gandhi, V.G., Sivaram, S. and Bhardwaj, I.S. 1982. Acrylonitrile copolymers using the Cobalt Acetylacelonatctriethythylalminum initiator system. 3. Monomer sequence distributions. Macromolecules, l5, 1636-1638.

23. Brar, A.S. and Sunita. 1991. Polymer Sequencc determination of aaylonitrilevinyl acetate copolymers prepared by emulsion copolymerization using carbon-13 NMR spectroscopy. Polymer Sci. [symp. proc. polymer 911, 2, 582.

24. Chectham, P.F., Huckerby T.N and Tabner, B.N. 1994. A high field "C-NMR study of the aqeous copolymerisation of acrylonitrile and vinyl acetate. Detemma ' tion of comonomer reactivity ratios. Eur. Polymer J., a , 581-587.

25. Cheetham, P.F. and Tabner, B.J. 1994. A high field 'C-NMR study of the aqeous copolymerisation of acrylonitrile and vinyl acetate. MicrostrucbJral observations. Eur. Polymer J. 30, 1367-1373.

26. Busfield, W.K., Grice, I.D. and JenLins, 1.D. 1992. Free radical initiation mechanisms in copolymerisation studied by &oxide trapping technique. Polymer Int., 27, , 119-123.

27. Cheetham, P.F. and Tabner, B.J. 1993. Aspin trap study ofaqueous heterogeneous copolymerization

Chem., 145/146,, 125-147.

169

N. T. McManur, A. Penlidis and G. L Rempel

of acrylonitrile and vinyl acetate. Eur. Polymer J., 29, , 451-454. 28. Dub& M A . , Amh Sanayei, R., Penlidis, A., O'DriscoU, KF. and Reilly, P.M. 1991. A

M i m m p u t e r Program for F,stimation of Copolymerization Reactivity Ratios. J. Polymer. Sci., Polymer. Chem., 29, 703-708.

29. Tidwell, P.W. and Mortimer, G.A. 1965. An impved method of calculating reactivity ratios. J. Polymer. Sci., (A), 2, 369-387.

30. Scott, P.J., Kumdersma, M.and Perdidis, A. 1992. GPC/HPLC Operating Manual, Internal Report. ( Available from A. Penlidis ).

31. O'DriscoU, KF. and Reilly, P.M. 1987. Detemum . tion of reactivity ratios in copolymerization. Makromol. Chem., Makromol. Symp., 10111,355-374.

32. McManus, N.T. and Penlidis, A. 1996. A kinetic study of Styrene Ethyl Acrylak Copolym&tion. J. Polymer. Sci., Polymer. Chem., a,, 1237-1248.

33. Hamiclec A. 1981 in " Emkion Potymerm*on of Wnyl Aceme ", El Aasser, M.S. and Vanderhoff, J.W. (ed~), Chapter 8, 49-61.

Received: 14 February 1997. Accepted after revision: 13 March 1997.

170

Documents

A Kinetic Investigation of the Copolymerization of Acrylonitrile and Vinyl Acetate in Bulk