Thermodynamics of binary polymer blends. System polystyrene-polycarbonate obtained by mixing in the melt

1144

V . P . PmVALKO et aL

3. A. S. POLINSKII, V. S. PSHEZHETSKII and V. A. KABANOV, Dokl. Akad. Nauk SSSR 256: 129, 1981 4. A. S. POLINSKII, V. S. PSHEZHETSKII and V. A. KABANOV, Vysokomol. soyed. A25: 72, 1983 (Translated in Polymer Sci. U.S.S.R. 25: 1, 81, 1983) 5. Elementarnye metody khimicheskoi kinetiki (Elementary Methods of Chemical Kinetics). (Eds. N. M. Emanuel and G. B. Sergeyeva) p. 61, Vysshaya shkola, Moscow, 1980

PolymerScienceU.S.S.R.Vol. 27, No. 5, pp. 1144-I153,1985 Printedin Poland

0032-3950/85 $10.00+ .00 PergamonJournalsLtd.

THERMODYNAMICS OF BINARY POLYMER BLENDS. SYSTEM POLYSTYRENE-POLYCARBONATE OBTAINED BY MIXING IN THE MELT* V. P. PRIVALKO,Yu. S. LIPATOV,Yu. D. BESKLUBENKOand G. YE. YAREbIA Institute of High-Molecular Compounds, U.S.S.R. Academy of Sciences

(Received 7 September 1983) The thermodynamic state of PS-polycarbonate mixtures in the melt has been studied by measurement of equilibrium values of specific volume over a wide range of temperatures and pressures. The experimental data are discussed in the framework of the Flory theory. In spite of the macroscopic incompatibility of the studied polymers in the melt, the increase of pressure results in "spreading" of the interphase regions into the whole volume of the system. The agreement between theory and experiment breaks down for elevated pressures.

Fog a quick evaluation of the compatibility of components in a binary polymeric composite in the amorphous state an empiric criterion is widely used, according to which one glass transition temperature should be observed in a one-phased system. The temperature can be found in the interval between the glass transition temperatures of both components Tsl and Tg2 while the system is incompatible when two glass transition temperatures exist corresponding to Tgl and Tg2 [1]. The two glass transition temperatures can exist, in principle, as a consequence of phase separation which preceeds the glassy state when a homogenous (one-phase) melt is cooled down slowly. In this case the line of two-phase equilibrium (binodal) lies above Ts~ and Tg2. By our opinion, the more objective information about the "true" miscibility of polymers in the melt can be provided by measurement of the dependence of "superfluous" (in comparison with additive) values of a binary system thermodynamics characteristics on the composition at various temperatures and pressures. At higher pressures, judged according * Vysokomol. soyed. A27: No. 5, 1021-1028, 1985.

Thermodynamics of binary polymer blends

1145

to the. presented data [2-5], the binodal is displaced and it causes an enhancement of miscibility of the mixture components. The aim of this paper is to investigate the thermodynamic state of PS and polycarbonate (PC) in the melt by accurate measurements of equilibrium values of the specific v o l u m e for b i n a r y composites based o n the wide range of temperatures a n d p r essures. Materials for the investigation were industrial products of PS and PC, molecular mass .~/~ =4.7 x 105 and 0.5 x l0 s, respectively. The samples for the investigation were obtained by efficient preliminary mixing of the original powder-like polymers followed by hot pressing at 473 K and at pressure 50 MPa. The PS content fo rthe various composites was 1, 5, 20, 50, 80, 95 and 99 wt. ~. (Samples have been asigned correspondingly CSC-1, CSC-5 etc.) The heat capacity was measured by means of a differential scanning microcalorimeter DSM-2M at normal pressure and in the temperature range 333--473 K, the rate of temperature increase was 12 deg/min, the relative error of measure,ments was smaller than 3 %. The specific volume measurements were carried out by thermopiezometer in the temperature range 403--483 K and at pressures 27"7-94.1 MPa. This has been described in detail earlier [61. A sample studied was placed in a pressure cell furnished by firmly fixed thermocouple in the middle; after exposure for 350--450see the values ofv were registered at chosen isobaric-isothermic conditions (the error was ~ 5 x 10 -7 m3/kg). The first treatment ofv values was carried out using the Tait equation 1 -V/Co =0"08941n( 1 +p/B), and values of specific volume Vo were obtained for a sample at normal pressure so that the variation of the "material" constant B was minimal in the whole range of pressures. The values of specific coefficient of volume-thermic expansion for a blend (dv/dT)p were obtained from the slopes of the high temperature parts of the corresponding isobars, the coefficient of isothermic contraction Pr = - (~ In v/dp)r was ca;culated from relation/~r = 0"0894/(p + B). Instantaneous (quasiadiabatic) increase of pressure to the value Ap----9.5-9.7 MPa in the contraction cell leads to desirable increase of initial temperature of the sample-value AT. It is followed by slow decrease of temperature to the original value. This occurs due to gradual equalizing of the temperature fields in the sample due to conductivity. The distortion of the signal described is caused by the inertia of the system and it is manifested in deviation from linearity in the graphic dependence of the function In 0 on time t in the initial 5-7 see of relaxation. The distortion was eorriged by the choice of To value (i.e. the hight of jump in the temperature J T= T o - To) so that the graph presented would retain linearity in the whole range of relaxation time of temperature (here 0 = ( T - To)/ /(T, - To); To, T® and Tis the temperature of the sample in initial, end and intermediate moments of relaxation, respectively. The values of specific heat capacity Cp were found for every isobaric-isothermal regime by substitution of the corrected values zl T in the combination with the known values ,dp and (c~o/aT)p into the standard relationship for thermic elasticity

( ~TI~p)~ = ( a,,laT),

tic,,

The summ of relative errors for the calculated values of heat capacity was 5-7 %.

Individual components. A s it is seen f r o m Fig. 1, values v, (Ov/t3T)p a n d Cp show m o n o t o n i c decrease with increasing pressure for the melts of original PS a n d P C at 473 K. A n a l o g i c results were o b t a i n e d for all systems u n d e r study including other temperatures. F o r discussion o f the o b t a i n e d experimental d a t a the Flory state e q u a t i o n was used [7, 8] PV/T

=

~,,/3/(~,,/3 _ 1 ) - 1 / [ / T ,

(1)

1146

V . P . PRIVALKOet

al.

where ~' =p/P*, ~'=v/V*, T= T/T*, P* = CkT*/V*, T* =sq/2V*Ck and V* are reduced parameters, C is the number of outer (intermolecular) degrees of freedom and s is the number of the nearest adjacent segments of a chain, q is the energetic parameters of pair interaction. As usual [7, 8], the numerical values of reduced V*, T* and P* were evaluated by treatment of experimental data at normal pressure, according to equations T----(I'71/3-1)/[~4/3 (2a) 17= [1 + ~T/3 (1 + ~T)] 3

(2b)

P*=o~T~'2/flr,

(2c)

where ~=(a In o/dT)p is the coefficient of volume thermal expansion. The values V*, T* and P* are shown in the Table as an example for samples investigated at 443 and 473 K. Parameters V* and T* are not temperature independent as would be required for the full adequacy of the theory and experiment. They show tendency to increase with temperature, approximately in agreement with relation [8] 0 In T*/OT = (~T)- 10In V*/OT On the other hand, the observed decrease of P* with increasing temperature agrees with the constant value of product st/in relationship

srl=2P*V .2 The theoretical contraction isotherms for PS and PC in blends at 473 K (Fig. 1, continuous curves) were calculated according to equation (1) using characteristic parameters which are presented in the Table. They show the increasing deviation from experimental isotherms as the pressure increases. Analogous disagreement has been observed by Zoller [9] for many other polymers. This defect of the Flory theory is typical for all "cell" models. It is connected with inadequate calculation of liquid state entropy due to neglecting the contribution of holes [10]. The effect is even more pronounced when the experimental values of the derivative (Ov/OT)pfor PS and PC is compared with the corresponding theoretical curves calculated according to equation [8]

v/T (Ov/OT)p= 1/3 (~,1/3_ 1 ) - 1 + 2/7172/(/3172+ 1)

(3)

As it is seen from Fig. 1, the experimental values (Ov/OT)p for PS decrease with pressure more slowly but for PC more quickly than theoretical ones. When numerical values of Cp are analyzed for higher pressures, the fact must be considered that isobaric heat capacity of a melt presents an additive sum, composed of three contributions (in extreme case) [11]:

c.=cv+c.+ch, where Cv is the isobaric heat capacity evaluated from frequencies of skeletal oscillations and of side groups of the macromolecule, Ce= ~2vT/flr is the superfluous heat capacity caused by internal liquid pressure, Cn is the "hole" contribution. As it is seen from

Thermodyflamic~of binary polymer blends

1147

Fig. I, the experimental values of contribution C. at normal pressure for both original polymers practically coincide with theoretical values calculated according to the equation [12]

~ t = C*/Ce= 1-2/3v l/s-2(v 1/3- l)/~'I/S(p~ "2+ 1), where C*=P*II*/T *. When pressure increases the values of Ce for PS do not decrease, as the theory predicts, but even somewhat increase while the experimental values of C, for PC decrease, however, significantly quicker than the theoretical ones. The basic cause of the observed disagreement between theory and experiment is, in this given case, analogous to the disagreement for the coefficient of volume thermal expansion. It is seen from Fig. 1 that the contribution C, does not exceed 10 % of the whole value of isobaric heat capacity Cp. Calculation of C, according to Wunderlich's method [11] proceeds from the parameters found for "hole" model Hirai-Eyring (v® =0.890 × x 10 -3 m3/kg, eJkffi666 K, vh=13"6× 10 -6 m3/mole, o=1-86 for PS; v®=0.765 x

+I °' 1"00

o

OOoooo

! ;o+. ++, +

;~0"~

+

+![

,~ 1"8 L

*Z

,,,

1"8 ~6.

2 25o

+ooooooi:

"~ 750;

t~

,

1

50 p, HPa

Fu3. t

700

o, I

5O P~,wt.~

100

F£o. 2

Fie. 1. Dependeace of thermo4ynamic eharacterietke for 1~ (/) and PC (2) at 473 K o~ premtwe; 3, 4 - C+ and Ct are tht =orr~poadgng ~l~trt'bWio~* to the isobaric heat ~i~wity C~. ~ dimemteltl of the tx~int, approxima~y ¢ o r r ~ to tke erro¢ of mem~e.~a3t (here and in the £¢gJowing). FiG. 2. Empemleaee of ~ ckaracteriatie, e f eemlm~Jitm at 47$ K on ! ~ weii~tt oealmt at pa=WI (1~ al~d 94.! MPa (,2). 3-tiae tt~ereticaJ mlmm.

1148

v . P . PR/VALKO et al.

x 10 -a ma/kg, eh/k=666 K, vh=11"1 x 10-6 ma/mole, a=2.08 for PC). It was shown that the contributions Ch and Ce are comparable (Fig. 1) while values Ch with increasing pressure slightly increase. On the basis of the data obtained it is possible to conclude that the initial values of heat capacity Cv in the melt do not remain constant for both polymer but they show a tendency to decrease. According to our opinion, this result testifies the constancy of the Griinneisen effective coefficient 7'~= - t3 In vd~ In v-- - t~In Off /a In v due to increasing frequency of characteristic oscillations of a macromoleeule v~ and corresponding Debye temperature 0~. This is a consequence of the decrease in specific volume at higher pressures. This conclusion agrees qualitatively with experimental data for PE [13]. Obviously, the basic contribution to the decrease of Cv with pressure should be introduced by the optical part of the oscillation spectra of PS and PC; their Debye temperatures can be found above the temperature range of our measurements. Binary composites. In agreement with our results from calorimetric investigation, jumps in the heat capacity are observed on the curves of temperature dependence of the heat capacity for all binary systems studied at normal pressure. The temperature position and "partial" values (calculated for a given component) of the jumps in the heat capacity agree in the framework of experimental error with corresponding values for the original polymers (373+1 K and 0.284-0.02 kJ/kg.deg for PS; 4204-2 K and 0.22 4- 0.02 kJ/kg, deg for PC). According to these results, the given polymer pair is thermodynamically incompatible in the melt. This preliminary result qualitatively agrees with an empirical criterion which requires that close values of coefficients of volume thermal expansion enable compatibility at normal pressure only when the difference in characteristic temperatures of both components is not greater than 150-200 K [7]. Nevertheless, the number of deviations from additivity exist on the curves of the concentration dependence of the thermodynamic characteristics of composites at normal and higher pressures (Fig. 2) (especially in the region where the content of every component is small). The deviations significantly exceed the error of measurements. Commonly are found negative deviations from additive values of specific volume and the coefficient of volume thermal expansion at normal pressure for the composites with higher content of PC. The deviations change their sign stepwise in the range of "phase turn over" [14, 15] and they maintain the positive values for samples CSC-95 and CSC-99. Analogous change was found for the characteristical reduced parameters V*, T* and P* (Table and Fig. 3). The parameters were obtained by treating the experimental values of specific volume of composites according to the equations (2) (in the following these values of reduced parameters will be considered as "experimental"). The value of volume elasticity parameter B from the Tait equation for compositions is smaller than the additive one almost in the whole range of composition, however the values increase sharply for samples CSC-5 and CSC-1 (in correspondence with additive values 9 and 11, respectively). Finally, minima were observed on the curves of the dependence of the heat capacity at normal pressure on composition for samples CSC-1 and CSC-99. This analogous tendency has been manifested on the curves of concentration dependence of heat capacity at higher pressures. However, these data

Thermodynamicsof binary polymer blends

1149

are not considered because of their significant scatter which is caused by the existing difference in the dependence of Cp values on pressure for PS and PC (Fig. 1). The analysis of enumerated data proceeds from an idea that the melt of a composite of an arbitrary composition at normal pressure consists of a continuous phase A and a dispersed phase B with the length of insertions I (Fig. 4a). In agreement with Helfand theory [16], the length of the interphase zone l, which exists between two incompatible polymers, can be evaluated from relation l=2t/(6"Z) t/2 ,

(4)

where t is the effective length of a chain segment, X is the parameter of thermodynamic interaction between components of the mixture-the X value can be found from the equation Z=(v/RT)(,h

-,~2) 2 ,

~(5)

where v is the volume of a composite, gt and g2 are solubility parameters for componeiit 1 and 2. Using the thermodynamic relationship 62 ~_ T~/~ r - p

in combination with our experimental values of a and/~r, it can be shown that with increasing pressure the values of solubility parameters for PS and PC draw together in the region studied and they reach the same value at P>~60 MPa. In terms of the equations (4) and (5), this formally means the "spreading" of the interphase transition zone into whole volume, up to disappearance of the pure phases of individual components (Fig. 4b). In other words, we assume that the increasing pressure leads to the mutual enrichment of the continuous and dispersed phase by macromolecules of the other component. In that way it means the levelling of the compositional heterogeneity of the system (although some remaider fluctuations in composition can be expected, the type of which is shown on the Fig. 4b). So far, as shown above, the values Oo on Fig. 2 were obtained by extrapolation of the specific volume values of a melt to p=0.1 MPa. The values were measured at higher pressures and leads to a view that the deviations of experimental values vo from the additive ones may reflect the real effect of stronger interaction between PS and PC as a consequence of increasing compatibility in the melt at higher pressure. The Flory theory was used for the analysis of the excess thermodynamic functions of the investigated system [8, 17]. In the framework of this, the interaction of binary mixtures can be evaluated from Z1,2 parameter which is evaluated from X12 = s t dtl/2V .2 ,

where dr/=r/ll+r/22-r/12 is the excess pair interaction energy for components 1 and 2. The parameter 212 is connected with characteristic reduced parameters in the mixture by following relations [8, 17]: P* = ~1 P1 + 9 * P * - ~1 02 X12 • -.l- , -.---r n , , , /(~ot P *11 'T* .:'::

+ q J 2 P *2 / T ~* ) ,

(6 a) ~:: (6b)

1150

V.P. I~U'VAUCOet aL

where ~2--w2 V~2/(wx V~ + w2 V*) is the fraction of component 2 in the mixture, calculated for a "segment", wl and w2 ere the weight fractions of components 1 and 2, 02 =(sz/sl)~z/[qh +(s2/sl)q~2] is the fraction of component 2 calculated for the area of intermolecular contact. The reduced volume of the mixture ~r differs from the additive value V°=~I ~'~ +~2 ~'z by a value Ve which can be defined from relation

(7)

fZelf'° = ~vlv ° ,

where Jv is the deviation of the experimentally measured value of specific volume of the mixture v from the additive one v°. This approach enables one to calculate the theoretical value of the reduced volume of the mixture at normal pressure P"from the experimental values (Figs. 2 and 3) using the relation (7). The theoretical values of characteristic temperature T* can be obtained from equation (1) and the theoretical values of parameters P* and X~2 can be calculated according to equations (6). 0

I'~

0

OE

0

~ - - - ~

- lO

N

A

ol x2

B

__/\ . . . . j \.

0

I l j=

L j

I \

.5

b ^

~,

x

0

"~

-2.5

0

I

5O p.~ , wf. % FIG. 3

leo

l

L'-"O Fxo. 4

F~. 3. Dependence of exl~rimental (1) and theoretical O values of the ~ on PS weight content.

the~'y l~rameters

]P~. 4. Sc,hcmatic picture for the profile of relative content of A component (continuous curves) and of B (dashed lineO in tlm binary melt at nemml (~ and hillbr (b) pressure.

Thermodynamics of binary polymer blends

1151

THERMODYNAMIC CHARACTERISTICS AT NORMAL PRESSURE AND CHARACTERISTIC RF.DUCED PARAMETERS

VX10 3, Sample PS CSC-1 CSC-5 CSC-20 CSC-50 CSC-80 CSC-95 CSC-99 PC

T, K 443 473 443 473 443 473 443 473 443 473 443 473 443 473 443 473 443 473

ma/kg

axl07, K_t

1"0110 1.0260 0"8518 0.8632 0-8590 0-8701 0"8830 0.8951 0.9294 0.9412 0"9764 0.9967 1"0053 1-0203 1"0101 1-0239 0"8563 0-8673

5.07 5.00 4-17 4.11 4.13 4.08 4"41 4"35 4"54 4.48 5.27 5.17 5.09 5.02 4.98 4.01 4-44 4-38

B, MPa 155.6 + 1.2 152- I _~ 1.4 382.0_+3.6 263.9_+2.8 I 317.7_+ 5-1 255.1 +2.7 261"0+5'0 [ 216"3 +~6"8 187"7+ 1"4 ! 177.9~_ 1.3 I 168.5+1.0 i 119.1 +7.3 ! 154-4-+1-6 ] 150.0 -+0.9 [ 148.4+ 1"3 I 145.9_+0.9 I 286.6_+5.8 i 237.6 _+I "4

vxl03, mS/kg 0"8455 0"8523 0"7317 0"7367 0"7387 0"7433 0"7531 0'7582 0"7897 0"7941 0"8126 0.8240 0"8409 0.8471 0.8475 0"8529 0.7297 0.7340

T*, K 9193"5 9501"3 10434.4 10770.6 10497.6 10827"6 10049.8 10372"5

9864"8 10176-0 8967"5 9306.9 9105"2 9485.1 9298"4 9610-0 10011.6 10331.6

P*, MPa 593"9 580"8

1088.4 785"0 883"5 755"7 789"9 699-5 580"4 595"3 635.9 477" l 555.6 555.5 552.3 548.7 873.8 761.2

The experimental and theoretical values of parameters T*, P* and Z~2 are compared in Fig. 3. (In the calculations value s2/st =0.66 is assumed to be approximately equal to the ratio of the diametrical dimensions of PC and PS macromolecules "m a crystal. As seen from Fig. 3, the Flory theory predicts successfully not only the sign of the deviation from additivity but, in some cases, the absolute value of T* parameter as well. Analogous qualitative agreement (Fig. 2) has been observed also between the experimental values of the coefficient of thermal expansion at normal pressure and theoretical values which have been calculated according to the equation (3).The theoretical values of volume elasticity parameter B were evaluated according to the equation B=0-0894 [ 1 - 3 ( V t/3- I)] P*/3(~"~/3- I) (2, and they agree well with experimental values practically over the whole range of composition, with exception of the sample CSC-1 (Fig. 2). At the same time, the experimental and calculated values of parameters P* and X,2 differ, as a rule, not only in quantity but also in the sign of their deviation from additivity (Fig. 3). Apparently, the observed disagreement can be related (at least partially) to the inadequacy of the Flory state equation to the experiment in the region of higher pressures, as mentioned before. This conclusion is confirmed by comparison of experimental and theoretical values for specific volume for composites at pressure p=94.1 MPa (Fig. 2). Thus, the qualitatively agreement of the Flory theory with experime~al data at normal pressure in the region of middle compositions confirms the original assumption of relative homogenization of binary systems at higher hydrostatic pressures. Simultaneously, in the framework of the Flory theory there still remains unexplained the

1152

V.P. PRIVALKOet al.

anomalous increase of the B parameter for CSC-1 sample and the great negative deviation from additivity for the heat capacity values for samples CSC-1 and CSC-99. In our opinion, the jump in B values for CSC-1 sample reflects orderring of PC melt due to filling of PS maeromolecules into the loosely packed interstructural parts of the continuous phase. The assumption is supported by the high quantity of the experimental value of the interaction parameter 3f12 and its negative sign. This is characteristic for dissolution of a polymer in "orderring" solvents [18, 19]. On the other hand, the slight minimum of B and the high positive value of Z12 for CSC-99 sample is caused by an obvious effect when the structure of a melt is loosened and when PC is molecularly dispersed in the continuous PS phase. Finally, in framework of standard evaluation of Cp =(dH/~T)p, the decrease of heat capacity for samples CSC-1 and CSC-99 clearly shows, the decrease of the enthalpy of the system H as a consequence of outstanding temperature of molecular mixing of PS and PC. The local phase structure of the melt for these samples (maximal PS amount in continuous PC phase and vice versa) should be different when different signs of deviations from additivity of excess volumes of mixing and of Z12 parameters are taken into account. Thus, it is possible to consider in the framework of the Flory theory on the basis of the analysis of results from experimental investigation that, regardless of the macroscopic incompatibility PS and PC in the melt at normal pressure, the interphase interactions in composites based on PS and PC are stronger at higher pressure. This leads to "spreading" of the interphase regions between both components into the whole volume of the system. The Flory theory describes the thermodynamic properties of composites satisfactorily in the region of middle compositions only at normal pressure while at higher pressures the agreement between the theory and experiment breaks down. Apparently, minimal amounts of any components (up to 1 wt. unit) can be dispersed in the continuous phase but corresponding composites differ in phase structure. This seem to be typical for the "effect of small additions" [20, 21]. The authors express their thanks to S. S. Demchenko for the measurement of heat capacity for the composites at normal pressure and to M. M. Zhaldak for his help in working out the programmes for treatment of the experimental data and for calculation of the thermodynamic functions made on EVM. Translated by J. HORSKA REFERENCES

1. W.J. MacKNIGHT, F. E. KARASZ and J. R. FRIED, In: Polymer Blends (Eds. D. R. Paul and S. M. Newman) Vol. 1, chap, 5, p. 219, Mir, Moscow, 1981 2. L. P. MASTER, Macromolecules 6: 5, 760, 1973 3. G. BLAUM and B. A. WOLF, Macromolecules9: 4, 579, 1976 4. B. A. WOLF and H. GEERISSEN, Colloid and Polymer Sci. 259: 12, 1214, 1981 5. Y. SUZUKI, Y. MIYAMOTO, H. MIYAJI and K. ASAI, Polymer Letters 20: 11, 563, 1982 6. V. P. PRIVALKO,G. Ye. YAREMA,Yu. D. BESKLUBENKO and G. V. TITOV, In: Physical Methods of Polymer Investigation. p. 117, Naukova dumka, Kiev, 1981 7. I. C. SANCHES, In: Polymer Blends (Eds. D. R. Paul and S. M. ~qewman) Vol. 1, chap. 3, p. 145, Mir, 1981

Plastic flow and non-linear viscoelasticity 8. 9. I0. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.

1153

P. J. FLORY, R. A. ORWOLL and A. VRIJ, J. Amer. Chem. Soc. 86: 18, 3507, 1964 P. ZOLLER, J. Polymer Sci. Polymer Phys. Ed. 18: 4, 897, 1980 R. SIMHA and T. SOMCYNSKY, Macromolecules 2: 3, 342, 1969 V. BARES and B. WUNDERLICH, J. Polymer Sci. Polymer. Phys. Ed. 11: 12, 1301, 1973 D. PATTERSON and G. DELMAS, Trans. Faraday Soc. 65: No. 3, 708, 1969 C. WU, J. Polymer Sci. Polymer Phys. Ed. 13: 2, 387, 1975 G. Ye. YAREMA, Yu. D. BESKLUBENKO and V. P. PRIVALKO, Dokl. AN USSR B, 1, 93, 1982 T. KUNORI and P. H. GEIL., J. Macromol. Sci. B, 18: 1, 93, 1980 E. HELFAND, Accounts Chem. Res. 8: 2, 295, 1975 P. J. FLORY, R. A. ORWOLL and A. VRIJ, J. Amer. Chem. Soc. 86: 18, 3515, 1964 P. N. HONG and G. DELMAS, Macromolecules 12: 4, 740, 1979 V. N. KLrLEZNEV, (Polymer Blends). p., 303 Khimiya, Moscow, 1980 Yu. S. LIPATOV, J. Appl. Polymer Sci. 22: 7, 1895, 1978 Yu. S. LIPATOV, Ye. V. LEBEDEV and V. F. SHUMSKI, Vestnik AN USSR, 12, 22, 1981

Polymer ScienceU.S.S.R.Vol. 27, No. 5, pp. 1153-1159,1985 Printed in Poland

0032- 3950/85 $I0.00+.00

PergamonJournals Ltd.

RHEOLOGY OF MELTS OF A MODEL LOW-MELTING LIQUID CRYSTALLINE COPOLYMER OF BIS (4-CHLOROCARBONYLPHENYL) TEREPHTHALATE WITH POLYPROPYLENE GLYCOL. PLASTIC FLOW AND NON-LINEAR VISCOELASTICITY* L. S. BOLOTNIKOVA, A. YU. BILIBIN, A. K. YEVSEYEV, YU. N. PANOV, O. N. P1RANER, S. S. SKOROKRODOV and S. YA. FRENKEL' Institute of Macromolecular Compounds, U.S.S.R. Academy of Sciences

(Received 8 September 1983)

The dependence of viscosity on shear rate and of the Young modulus on frequency were measured for low-melting, thermotropic polyester - a copolymer of bis (chlorocarbonylphenyl) terephthalate and polypropylene glycol. In the temperature interval 120--180°C, where the copolymer exists in the liquid-crystalline state, it behaves as a pseudoplastic body. Above 230°C the copolymer melt becomes isotropic. In the region between 180 and 230°C its properties are not stable, probably due to a coexistence of smectic, nematic, and isotropic domains. When the polyester in the liquid-crystalline state undergoes dynamic deformation, its viscoelastic behaviour is non-linear. * Vysokomol. soyed. A27: No. 5, 1029-1034, 1985.