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Effect of the degree of substitution of cellulose nitrate on its thermodynamic compatibility with polyvinylnitrate
1443
Thermodynamic compatibility with polyvinylnitrate
12. V. A. ZHORIN, A. V. MAKSIMYCHEV, M. Ya. KUSHNEREV, D. P. SHASHKIN and N. S. YENIKOLOPYAN, Zhurn. fiz. khim. 53: II, 2772, 1979 13. A. S. BADAYEV, V. A. ZHORIN, I. I. PEREPECHKO and N. S. YENIKOLOPYAN, Dokl AN SSSR 289: 5, 1148, 1986
Polymer Science U.S.S.R. Vol. 31, No. 6, pp. 1443-1448, 1989 Printed in Poland
0032-3950/89 $10.00+ .00 (~) 1990 Pergamon Press pie
EFFECT OF THE DEGREE OF SUBSTITUTION OF CELLULOSE NITRATE ON ITS THERMODYNAMIC COMPATIBILITY WITH POLYVINYLNITRATE* A. A. TAGER, N. I. SHIL'NIKOVA,V. F. SoPm and G. N. MARCHENKO Gorkii State University of the Urals
(Received 15 January 1988) Gibbs energies of mixing have been determined for two cellulose nitrate samples with differing degrees of substitution with polyvinylnitrate. It was found that the CN sample containing 13.4~ nitrogen is incompatible with polyvinylnitrate over the entire range of compositions, while the sample containing 1270 nitrogen is compatible with the polyvinylnitrate only if its concentration in the mixture does not exceed 60~. As EARLYas 1947 the system C N - P V A was one of the first of the thermodynamically compatible polymer-polymer systems that were investigated. Subsequent studies [2, 3] showed that C N containing 12 ~o nitrogen is compatible with PVA and the Gibbs energy is reduced. The mixing o f the polymers is accompanied by high negative values for the enthalpy and entropy and the Gibbs energy of mixing such as appear typical for thermodynamically stable polymer-polymer systems [4-45]. Our aim in the present investigation was to examine the thermodynamic compatibility o f C N with polyvinylnitrate (PVN) and to determine the extent to which the degree o f substitution of C N affects the thermodynamic compatibility. A study was made of CN samples containing 13.4 and 12~/~nitrogen with 39/nequal to 6.5 × 10~ and 9"5x 104 respectively. PVN had 37/,=3 x 106. Evaluation of the thermodynamic compatibility of the polymers was based on the sign of the Gibbs energies of mixing determined by the method proposed by Tager and coworkers [2-4], for which an experimental study of the sorption of acetone vapours was carried out at 298 K in the pressure range 10-3-10 -4 Pa with samples of NC, PVN and their blends, using a sorption device fitted with a quartz spring balance, its sensitivity being (0.2-0.3) x 103 m/kg. By means of the * Vysokomol. soyed. A31" No. 6, 1316-1319, 1989.
I444
A.A. TAOERet al.
sorption isotherms we calculated the Gibbs energy of mixing with acetone, (10 -~ kg), for the individual polymers and their blends: zIG~, ziGn and AGm. These values were substituted in the equation ztg~ = .4Gin- (o~1 AG= + 0~2,dGu),
(1)
and equation (1) was then used to find the mean Gibbs energy of mixing for CN with PVN referred to 1 x 10 -3 kg of the system (in equation (1) o& and co2 are the weight fractions of polymer in the composition). Figures I a n d 2 show th~ sorption isotherms for acetone v a p o u r s (the sorbatc) a d s o r b e d by C N , P V N and their blends (the sorbents) on the coordinates x / m - p / p , ,
=/m kg/k9
=lrn,kg/k9
3 o
b
b~
0.10
=/"n'kg/skSI~o
74 2021
f'5
a
0.1
a_ 5
3
0"3
PIPs
1.5
o.1
q_ 6-
o.2 P/Ps
6 CL
2--
0.5
a
2--
0.5
0.25 Fie. 1
0.75P/Ps
0.2s
0.75P/Ps FIQ. 2
FIe. 1. Isotherms of sorption of acetone vapours by CN (12~/oN), PVN and their mixtures (a) and initial portions of the isotherms on an enlarged scale (b): I - C N (12~/o N), 2 - P V N ; 3-26~/0 PVN; 4 - 3 7 % PVN; 5-47~o PVN; 6-60Yo PVN. Fxo. 2. Isotherms of sorption of acetone vapours by CN (13.4~/o N), PVN and their mixtures (a) and initial portions of the isotherms on an enlarged scale (b): I - C N (13'4% N); 2 - P V N ; 3-5?/0 PVN; 4 - 1 9 % PVN; 5-43Yo PVN; 6-60~/o PVN; 7 - 8 8 % PVN.
Thermodynamic compatibility with polyvinylnitratc
1445
where x is the acetone concentration, m is the amount of sorbent absorbed and PIPs is the acetone vapour pressure above the system. The same Figures show initial portions of the isotherms on an enlarged scale. The sorption isotherms for CN are in the form of S-shaped curves with an initial portion that is convex in respect to the ordinate. The~e isotherms are associated with loosely packed polymers, in which in the initial stage of sorption, two processes take place simultaneously, viz. CN micropores are filled up with solvent molecules, and swelling of the polymer is accompanied by rearrangement of its structure [5]. The isotherm of acetone vapour sorption by PVN is of curved appearance over the entire interval of pips, which is typical for densely packed polymers. For systems containing a high CN concentration S-shaped isotherms are preserved; as the PVN concentration increases, the convex portion disappears from the isotherms. The placement of the isotherms, i.e. their order of adsorptive ability, is a function of structural looseness and ofthe chemical structure of the polymer. In the initial stage of sorption the adsorptive ability is highest for CN, while in the end stage it is highest for PVN. Consequently intersection of the isotherms occurs. Using the soprtion isotherms and the equation Apx =
RT M1
In p/ps
(2)
we calculated differences in the chemical potentials/zl for 1 g of acetone in swollen polymer phase (or in a polymer blend) and/z ° for l g of pure acetone d/z,. Using the Gibbs-Duhem equation differences in the specific chemical potentials were calculated for the polymer component A/z2 [4]; the average Gibbs energies of mixing were calculated by the equation ,dgm----aT! A/I1 +(-O2 A#2
(3)
for CN, PVN and their mixtures with acetone. In equation (3)ah and o~2 are weight fractions of acetone and of polymer (respectively) in a polymer-acetone mixture. For both systems Figs. :3 and 4 show the concentration dependence of Agm. The curves are all located in the negative region, pointing to a spontaneous process of dissolution or swelling for CN in acetone; the curves are convex downwards. This means that the resulting solutions are thermodynamically stable. It is seen from Fig. 3 that the CN curve goes lowest of all;'that for the PVN is significantly higher. It follows that the CN containing 12~o N has greater atfinity with acetone than PVN has. As the PVN concentration in the compositions increases their affinity with acetone is reduced, while the curve for the mixture containing 60 ~o PVN is situated even above that for PVN itself. On comparing Figs. 3 and 4 it is seen that the curve for the CN containing 13"4~o N is situated significantly higher than that for the low-nitrogen CN, and higher than that for the PVN. The curves for the mixtures are situated above those for CN and PVN, i.e. the mixtures have a greater affinity with acetone than the polymers themselves.
1446
wT=I(PVN)
A . A . TAGEIte t
0.5
w~=1(c~Se~N)
al.
m~=1(PVN)
O.S .
,.x
o~,=1(CN(~J.4~N))
l
8
x
7. 12
16
-Agm,lt
s
FIG. 3 FIG. 4 FIa. 3. Specific mean Gibbs energies of mixing for CN (12yo N), PVN and their mixtures with acetone: 1 - C N (12Yo N); 2-PVN; 3-26Yo PVN; 4-19yo PVN; 5-43yo PVN; 6-60yo PVN; 7 - 88~/o PVN. FIG. 4. Specific mean Gibbs energies of mixing for CN (13"4~o IN), PVN and their mixtures with acetone: 1 - C N (13"4~/oN); 2-PVN; 3-59/0 PVN; 4-199/o PVN; 5-439/0 PVN; 6--60y0 PVN; 7 - 88yo PVN. Moreover as the PVN concentration in the compositions increases, their affinity with acetone grows initially (curves 2 and 3), and afterwards decreases. Figures 3 and 4 show values of the average energies of mixing ,6a m referred to 1 g of solution. At a point where 0)2 = 1, tangents to these curves make intercepts on the ordinate equal to AG~, ,ffGiiand AGm. Substituting their values into equation (1) we obtain values of the average energies of mixing of the polymers with one another. These data appear in Fig. 5; it follows that for the system CN (13.4% N)-PVN the curve lies in the positive re#on over the entire range of composition, while for the system CN (12% N)PVN Agx<0 in the PVN-enriched region, and Agx>0 in the CN-enriched region. On the basis of the experimental results we calculated values of the Flory-Haggins interaction Z2,3, using the equation [6] I n a t = I n {01 + (1 - {01) -{"(1 - {01) (~1,2 {02 "{"Xl.3 {03) - X2,3 {02 {03,
, s=xlo- ,J/a 2
6 •
oJ, t(pv/~)
2
o~1(CN) -2
FxG. 5. Mean Gibbs energies of mixing for CN with PVN: I - C N (12yo N)-PVN; 2 - C N (13"49/o N)-PVN.
Thermodynamic compatibility with polyvinylnitrate
1447
where al is the solvent reactivity in the three-component polymer-polymer-solvent system; ~1, ~2 and ~P3 are volume fractions of the solvent and of both polymers in the latter system, respectively; 2'1,2 and 2'1,3 are interaction parameters for each polymer with solvent in the polymer-solvent binary system. VALUES OF 22,3 FOR TIlE C N - P V N SYSTEMS System C N (12Yo N ) - P V N
PVN, Yo 26 37 60
22.3 1"61 1.20 - 0.39
System C N (13"4Yo N ) - P V N
PVN, ~
Z2,a
5 19 43 60
7"21 1.54 1"41 0"15
It can be seen from the Table that for the system CN (13"4~o N)-PVN Z2,3>0 over the entire range of compositions, while for CN (127o N)-PVN in the region e f CNenriched compositions 2'2,3>0, while in the PVN-enriched region 2'2.3 <0. The results discussed above show a marked dissimilarity in the behaviour of the systems CN-PVA and CN-PVN. The first system is an example of a mixture with very good thermodynamic affinity of the components. The thermodynamic compatibility of CN with PV'N depends on the degree of substitution of CN. Whatever the composition, the high-nitrogen CN is incompatible with PVN (Agx>0, 2"2,3>0). The low-nitrogen CN is compatible with PVN only if the concentration in the composition exceeds 60 wt. 700-Unfortunately, no data are to be found in literature as regards thermodynamic interaction of low molecular analogs of the polymers studied. We surmise, however, that the energy of interaction between NO2 groups and - O - ( 2 - C H s
II
O is higher than between NOz - N O 2 . Evidence of this appears, in particular, in the enthalpies of mixing of some compounds. For instance, in the case of an equimolar ratio of the components the mixing of nitroglycerin with nitromethane is accompanied by heat evolution amounting to 377 J/mole, while in the mixipg of nitroglycerin with acetone A H = 1506 J/mole [7]. We deduce from this that CN may be energywise more favourably mixed with compounds containing carbonyl groups that with compounds containing NO2 groups. PVN and CN have therefore a propensity to form two-phase systems. Translated by R. J. A. HENDRY REFERENCES 1. A. DOBRY and F. BOYER-KAWENOKI, J. Polymer Sci. 2: 1, 90, 1947 2. A. A. TAGER, Vysokomol. soyed. A14: 12, 2690, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 12, 3129, 1972) 3. A. A. TAGER, T. I. SHOLOHOVITE and J. S. BESSONOV, Europ. Polymer J. 11: 4, 321, 1975
4. A. A. TAGER, Fizikokhimiya polimerov (Polymer Physicochemistry). p. 544, 3rd revised edit., Moscow, 1978
1448
A.A. ASKADSKJIet at,
5. A. A. TAGER and M. V. TSILIPOTKINA, Uspekhi khimii 47: 1, 152, 1978 6. R. L. SCOTT, J. Chem. Phys. 17: 3, 279, 1949 7. V. P. BELOUSOV, A. G. MORACHEVSKII and M. Yu. PANOV, Teplovye svoistva rastvorov neelektrolitov (Heat Properties of Nonelectrolyte Solutions). p. 263, Leningrad, 1981
Polymer Science U.S.S.R. Vol. 31, No. 6, pp. 1448-1457, 1989 Printed o n P o l a n d
0032-3950]89 $10.00+ .00 (~) 1990 Pergamon Press ple
A RELAXATION RELATIONSHIP TAKING ACCOUNT OF THE REVERSIBLE CHARACTER OF THE RELAXATORS' INTERACTION* A. A. ASKADSKII, G. V. SUROV, V. V. NEMCHINOV, A. A. BLYUMEI'CFEL'D
and Z. S. Vmm,USKAS(dec.) Kuibyshev Structural Engineering Institute, Moscow (Received 26 February 1988)
The novel relaxation relationship is based on an analysis of entropy changes occurring in systems during relaxation processes. In derivation of the relationship it has been assumed that reLaxators of various types interact during stress relaxation processes. Moreover in contradistinction to the relationship proposed in an earlier paper the reversible character of this i~teraction and the transition to the equilibrium state are taken into account. Trm novel relaxation relationships that were proposed in an eailier paper [1] were based on a study o f entropy changes occurring in systems during stress relaxation processes. The first relationship was obtained by means o f a kinetic analysis o f the interaction of relaxators and a study o f the conversion of interaction " p r o d u c t s " to a nonrelaxing type o f material. The t e r m "relaxators" refers to various kinetic units, including Individual groups of atoms (chain units, chain segments) that interact with one another within the limits o f their own kinetic volumes and, following rearrangement in the course o f this interaction, are changed into a nonrelaxing material. M o r e o v e r this is not a matter of chemical interaction, but is a physical type o f interaction, e.g. such as that involved in the formation o f microblocks, viz. regions that are structurally more compact and play the role o f physical crosslinks in a network. During stress relaxation processes these microblocks may disintegrate and reemerge at other sites which, in the final analysis, will lead to smaller relaxing stresses. There are other cases o f this type o f interaction. For instance, the interaction of kinetic units within the confines o f inidivual microcavities m a y result in their merging during the course of stress relaxation and a stress concentration m a y thus be eliminated. It therefore appears, as was noted above, * Vysokomol. soyed. A31: No. 6, 1320-1327, 1989.
Thermodynamic compatibility with polyvinylnitrate
12. V. A. ZHORIN, A. V. MAKSIMYCHEV, M. Ya. KUSHNEREV, D. P. SHASHKIN and N. S. YENIKOLOPYAN, Zhurn. fiz. khim. 53: II, 2772, 1979 13. A. S. BADAYEV, V. A. ZHORIN, I. I. PEREPECHKO and N. S. YENIKOLOPYAN, Dokl AN SSSR 289: 5, 1148, 1986
Polymer Science U.S.S.R. Vol. 31, No. 6, pp. 1443-1448, 1989 Printed in Poland
0032-3950/89 $10.00+ .00 (~) 1990 Pergamon Press pie
EFFECT OF THE DEGREE OF SUBSTITUTION OF CELLULOSE NITRATE ON ITS THERMODYNAMIC COMPATIBILITY WITH POLYVINYLNITRATE* A. A. TAGER, N. I. SHIL'NIKOVA,V. F. SoPm and G. N. MARCHENKO Gorkii State University of the Urals
(Received 15 January 1988) Gibbs energies of mixing have been determined for two cellulose nitrate samples with differing degrees of substitution with polyvinylnitrate. It was found that the CN sample containing 13.4~ nitrogen is incompatible with polyvinylnitrate over the entire range of compositions, while the sample containing 1270 nitrogen is compatible with the polyvinylnitrate only if its concentration in the mixture does not exceed 60~. As EARLYas 1947 the system C N - P V A was one of the first of the thermodynamically compatible polymer-polymer systems that were investigated. Subsequent studies [2, 3] showed that C N containing 12 ~o nitrogen is compatible with PVA and the Gibbs energy is reduced. The mixing o f the polymers is accompanied by high negative values for the enthalpy and entropy and the Gibbs energy of mixing such as appear typical for thermodynamically stable polymer-polymer systems [4-45]. Our aim in the present investigation was to examine the thermodynamic compatibility o f C N with polyvinylnitrate (PVN) and to determine the extent to which the degree o f substitution of C N affects the thermodynamic compatibility. A study was made of CN samples containing 13.4 and 12~/~nitrogen with 39/nequal to 6.5 × 10~ and 9"5x 104 respectively. PVN had 37/,=3 x 106. Evaluation of the thermodynamic compatibility of the polymers was based on the sign of the Gibbs energies of mixing determined by the method proposed by Tager and coworkers [2-4], for which an experimental study of the sorption of acetone vapours was carried out at 298 K in the pressure range 10-3-10 -4 Pa with samples of NC, PVN and their blends, using a sorption device fitted with a quartz spring balance, its sensitivity being (0.2-0.3) x 103 m/kg. By means of the * Vysokomol. soyed. A31" No. 6, 1316-1319, 1989.
I444
A.A. TAOERet al.
sorption isotherms we calculated the Gibbs energy of mixing with acetone, (10 -~ kg), for the individual polymers and their blends: zIG~, ziGn and AGm. These values were substituted in the equation ztg~ = .4Gin- (o~1 AG= + 0~2,dGu),
(1)
and equation (1) was then used to find the mean Gibbs energy of mixing for CN with PVN referred to 1 x 10 -3 kg of the system (in equation (1) o& and co2 are the weight fractions of polymer in the composition). Figures I a n d 2 show th~ sorption isotherms for acetone v a p o u r s (the sorbatc) a d s o r b e d by C N , P V N and their blends (the sorbents) on the coordinates x / m - p / p , ,
=/m kg/k9
=lrn,kg/k9
3 o
b
b~
0.10
=/"n'kg/skSI~o
74 2021
f'5
a
0.1
a_ 5
3
0"3
PIPs
1.5
o.1
q_ 6-
o.2 P/Ps
6 CL
2--
0.5
a
2--
0.5
0.25 Fie. 1
0.75P/Ps
0.2s
0.75P/Ps FIQ. 2
FIe. 1. Isotherms of sorption of acetone vapours by CN (12~/oN), PVN and their mixtures (a) and initial portions of the isotherms on an enlarged scale (b): I - C N (12~/o N), 2 - P V N ; 3-26~/0 PVN; 4 - 3 7 % PVN; 5-47~o PVN; 6-60Yo PVN. Fxo. 2. Isotherms of sorption of acetone vapours by CN (13.4~/o N), PVN and their mixtures (a) and initial portions of the isotherms on an enlarged scale (b): I - C N (13'4% N); 2 - P V N ; 3-5?/0 PVN; 4 - 1 9 % PVN; 5-43Yo PVN; 6-60~/o PVN; 7 - 8 8 % PVN.
Thermodynamic compatibility with polyvinylnitratc
1445
where x is the acetone concentration, m is the amount of sorbent absorbed and PIPs is the acetone vapour pressure above the system. The same Figures show initial portions of the isotherms on an enlarged scale. The sorption isotherms for CN are in the form of S-shaped curves with an initial portion that is convex in respect to the ordinate. The~e isotherms are associated with loosely packed polymers, in which in the initial stage of sorption, two processes take place simultaneously, viz. CN micropores are filled up with solvent molecules, and swelling of the polymer is accompanied by rearrangement of its structure [5]. The isotherm of acetone vapour sorption by PVN is of curved appearance over the entire interval of pips, which is typical for densely packed polymers. For systems containing a high CN concentration S-shaped isotherms are preserved; as the PVN concentration increases, the convex portion disappears from the isotherms. The placement of the isotherms, i.e. their order of adsorptive ability, is a function of structural looseness and ofthe chemical structure of the polymer. In the initial stage of sorption the adsorptive ability is highest for CN, while in the end stage it is highest for PVN. Consequently intersection of the isotherms occurs. Using the soprtion isotherms and the equation Apx =
RT M1
In p/ps
(2)
we calculated differences in the chemical potentials/zl for 1 g of acetone in swollen polymer phase (or in a polymer blend) and/z ° for l g of pure acetone d/z,. Using the Gibbs-Duhem equation differences in the specific chemical potentials were calculated for the polymer component A/z2 [4]; the average Gibbs energies of mixing were calculated by the equation ,dgm----aT! A/I1 +(-O2 A#2
(3)
for CN, PVN and their mixtures with acetone. In equation (3)ah and o~2 are weight fractions of acetone and of polymer (respectively) in a polymer-acetone mixture. For both systems Figs. :3 and 4 show the concentration dependence of Agm. The curves are all located in the negative region, pointing to a spontaneous process of dissolution or swelling for CN in acetone; the curves are convex downwards. This means that the resulting solutions are thermodynamically stable. It is seen from Fig. 3 that the CN curve goes lowest of all;'that for the PVN is significantly higher. It follows that the CN containing 12~o N has greater atfinity with acetone than PVN has. As the PVN concentration in the compositions increases their affinity with acetone is reduced, while the curve for the mixture containing 60 ~o PVN is situated even above that for PVN itself. On comparing Figs. 3 and 4 it is seen that the curve for the CN containing 13"4~o N is situated significantly higher than that for the low-nitrogen CN, and higher than that for the PVN. The curves for the mixtures are situated above those for CN and PVN, i.e. the mixtures have a greater affinity with acetone than the polymers themselves.
1446
wT=I(PVN)
A . A . TAGEIte t
0.5
w~=1(c~Se~N)
al.
m~=1(PVN)
O.S .
,.x
o~,=1(CN(~J.4~N))
l
8
x
7. 12
16
-Agm,lt
s
FIG. 3 FIG. 4 FIa. 3. Specific mean Gibbs energies of mixing for CN (12yo N), PVN and their mixtures with acetone: 1 - C N (12Yo N); 2-PVN; 3-26Yo PVN; 4-19yo PVN; 5-43yo PVN; 6-60yo PVN; 7 - 88~/o PVN. FIG. 4. Specific mean Gibbs energies of mixing for CN (13"4~o IN), PVN and their mixtures with acetone: 1 - C N (13"4~/oN); 2-PVN; 3-59/0 PVN; 4-199/o PVN; 5-439/0 PVN; 6--60y0 PVN; 7 - 88yo PVN. Moreover as the PVN concentration in the compositions increases, their affinity with acetone grows initially (curves 2 and 3), and afterwards decreases. Figures 3 and 4 show values of the average energies of mixing ,6a m referred to 1 g of solution. At a point where 0)2 = 1, tangents to these curves make intercepts on the ordinate equal to AG~, ,ffGiiand AGm. Substituting their values into equation (1) we obtain values of the average energies of mixing of the polymers with one another. These data appear in Fig. 5; it follows that for the system CN (13.4% N)-PVN the curve lies in the positive re#on over the entire range of composition, while for the system CN (12% N)PVN Agx<0 in the PVN-enriched region, and Agx>0 in the CN-enriched region. On the basis of the experimental results we calculated values of the Flory-Haggins interaction Z2,3, using the equation [6] I n a t = I n {01 + (1 - {01) -{"(1 - {01) (~1,2 {02 "{"Xl.3 {03) - X2,3 {02 {03,
, s=xlo- ,J/a 2
6 •
oJ, t(pv/~)
2
o~1(CN) -2
FxG. 5. Mean Gibbs energies of mixing for CN with PVN: I - C N (12yo N)-PVN; 2 - C N (13"49/o N)-PVN.
Thermodynamic compatibility with polyvinylnitrate
1447
where al is the solvent reactivity in the three-component polymer-polymer-solvent system; ~1, ~2 and ~P3 are volume fractions of the solvent and of both polymers in the latter system, respectively; 2'1,2 and 2'1,3 are interaction parameters for each polymer with solvent in the polymer-solvent binary system. VALUES OF 22,3 FOR TIlE C N - P V N SYSTEMS System C N (12Yo N ) - P V N
PVN, Yo 26 37 60
22.3 1"61 1.20 - 0.39
System C N (13"4Yo N ) - P V N
PVN, ~
Z2,a
5 19 43 60
7"21 1.54 1"41 0"15
It can be seen from the Table that for the system CN (13"4~o N)-PVN Z2,3>0 over the entire range of compositions, while for CN (127o N)-PVN in the region e f CNenriched compositions 2'2,3>0, while in the PVN-enriched region 2'2.3 <0. The results discussed above show a marked dissimilarity in the behaviour of the systems CN-PVA and CN-PVN. The first system is an example of a mixture with very good thermodynamic affinity of the components. The thermodynamic compatibility of CN with PV'N depends on the degree of substitution of CN. Whatever the composition, the high-nitrogen CN is incompatible with PVN (Agx>0, 2"2,3>0). The low-nitrogen CN is compatible with PVN only if the concentration in the composition exceeds 60 wt. 700-Unfortunately, no data are to be found in literature as regards thermodynamic interaction of low molecular analogs of the polymers studied. We surmise, however, that the energy of interaction between NO2 groups and - O - ( 2 - C H s
II
O is higher than between NOz - N O 2 . Evidence of this appears, in particular, in the enthalpies of mixing of some compounds. For instance, in the case of an equimolar ratio of the components the mixing of nitroglycerin with nitromethane is accompanied by heat evolution amounting to 377 J/mole, while in the mixipg of nitroglycerin with acetone A H = 1506 J/mole [7]. We deduce from this that CN may be energywise more favourably mixed with compounds containing carbonyl groups that with compounds containing NO2 groups. PVN and CN have therefore a propensity to form two-phase systems. Translated by R. J. A. HENDRY REFERENCES 1. A. DOBRY and F. BOYER-KAWENOKI, J. Polymer Sci. 2: 1, 90, 1947 2. A. A. TAGER, Vysokomol. soyed. A14: 12, 2690, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 12, 3129, 1972) 3. A. A. TAGER, T. I. SHOLOHOVITE and J. S. BESSONOV, Europ. Polymer J. 11: 4, 321, 1975
4. A. A. TAGER, Fizikokhimiya polimerov (Polymer Physicochemistry). p. 544, 3rd revised edit., Moscow, 1978
1448
A.A. ASKADSKJIet at,
5. A. A. TAGER and M. V. TSILIPOTKINA, Uspekhi khimii 47: 1, 152, 1978 6. R. L. SCOTT, J. Chem. Phys. 17: 3, 279, 1949 7. V. P. BELOUSOV, A. G. MORACHEVSKII and M. Yu. PANOV, Teplovye svoistva rastvorov neelektrolitov (Heat Properties of Nonelectrolyte Solutions). p. 263, Leningrad, 1981
Polymer Science U.S.S.R. Vol. 31, No. 6, pp. 1448-1457, 1989 Printed o n P o l a n d
0032-3950]89 $10.00+ .00 (~) 1990 Pergamon Press ple
A RELAXATION RELATIONSHIP TAKING ACCOUNT OF THE REVERSIBLE CHARACTER OF THE RELAXATORS' INTERACTION* A. A. ASKADSKII, G. V. SUROV, V. V. NEMCHINOV, A. A. BLYUMEI'CFEL'D
and Z. S. Vmm,USKAS(dec.) Kuibyshev Structural Engineering Institute, Moscow (Received 26 February 1988)
The novel relaxation relationship is based on an analysis of entropy changes occurring in systems during relaxation processes. In derivation of the relationship it has been assumed that reLaxators of various types interact during stress relaxation processes. Moreover in contradistinction to the relationship proposed in an earlier paper the reversible character of this i~teraction and the transition to the equilibrium state are taken into account. Trm novel relaxation relationships that were proposed in an eailier paper [1] were based on a study o f entropy changes occurring in systems during stress relaxation processes. The first relationship was obtained by means o f a kinetic analysis o f the interaction of relaxators and a study o f the conversion of interaction " p r o d u c t s " to a nonrelaxing type o f material. The t e r m "relaxators" refers to various kinetic units, including Individual groups of atoms (chain units, chain segments) that interact with one another within the limits o f their own kinetic volumes and, following rearrangement in the course o f this interaction, are changed into a nonrelaxing material. M o r e o v e r this is not a matter of chemical interaction, but is a physical type o f interaction, e.g. such as that involved in the formation o f microblocks, viz. regions that are structurally more compact and play the role o f physical crosslinks in a network. During stress relaxation processes these microblocks may disintegrate and reemerge at other sites which, in the final analysis, will lead to smaller relaxing stresses. There are other cases o f this type o f interaction. For instance, the interaction of kinetic units within the confines o f inidivual microcavities m a y result in their merging during the course of stress relaxation and a stress concentration m a y thus be eliminated. It therefore appears, as was noted above, * Vysokomol. soyed. A31: No. 6, 1320-1327, 1989.