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Two types of relaxation in glassy polyarylates
~7.2
....
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A. A. ~ @ I { - L D R E I I
13. J. STAWITZ, Pharmaz, Ind., No. 3, 59, 1952 14. S. GLAESSON, Makromoi. Chem. 85: 83, 1960 15. CHIANG CHENG-YUAN, Opredelenlye molekulyarnyl~h ve/iov pol'lmerov. (Determina. tion of the Molecular Weight of Polymers.) p. 32, Foreign Lit. Publ. House, 1962 16. H. BARANSKA, Chemia Anal. 6: 1061, 1961 '
i ,'3
T W O T Y P E S OF R E L A X A T I O N IN GLASSY POLYARYYLATES*
A. A. ASKADSKII •
Institute of Hetevo-organio.Compounds, IJ.S.S.R. Academy of Sciences (Received 4 June 1965)
M ~ Y papers have been published on the relaxation properties 0f polymers in the high:elasti~ state, but problems associated with these properti6s in the glassy state have received little Study. I n this respect it is obviously of special interest to study the relaxation properties of rigid-chain polymers because in view of the large temperature range over which these polymers remain ih the glassy state the possibility is presented of making a detailed study of the temperature dependence of stress relaxation in the region where these polymers on the one hand do not display brittleness b u t - o n the 5ther hand do not soften. The materials chosen ~for s~udy-were polyarylates from isoph~halic and terephthalic acids with phenolphthalein (P-1 and P-2 respectively), of molecular Weight 48,000, prepared in ~-chloronaphthalene [1, 2]. Specimens o f the polyarylates in the f o r m of blocks were prel~ared by hot compression moulding and these were turned to cylinders of height 4.5 m m and diameter 3 r a m . Stress relaxation after uniaxial compression was studied over a w i d e r a n g e of temperatures in a micro-mechanical test machine [3]. For ~his purpose the specimens were rapidly compressed at a rate of 3 mm]min, after w h i c h the deformation, which in all cases was 4.4o//o, was kept constant during the whole experiment. The stress required to maintain this deformation was measured at set intervals of time, From these measurements the usual relaxation curve, represented schematically in Fig. 1, was obtained for each temperature: As a comparative characteristic of the relaxation properties of t h e polymers we took the reciprocal of the relative fall in Stress after relaxation for 1 hour. In terms of the values marked in Fig. 1 this value, 1[~, is given by 1
~.
~l~
0"(i - - 0" 1
* Vysokomol. soyed. 8: No. 8, 1342-1345, 1966..
(1)
1~73
Relaxatio~i~ in glassy pol~-arylates
where al is the s t r e s s after 1 ,hour and ~0 is t h e stress a t ' t h e m o m e n t of Cessation of deformation. -, ...... ' ~T e s t results for specimens of polyarylate P - 2 ~ r e given in ~ i g . 2. Similar curves were obtained for polyarylate P-1. I t is seen from lfig., 2 that in a cei~ain ~emperature region the relaxation curves! lie fairly close together and then at high temperatures t h e y gradually shift in the direction of lower stresses~ I n order to demonstrate more clearly the" temperature dependence of the relaxa~ tion properties o f these polyarylates curves ,of t h e temperature dependence of 6, g/cm 2 800
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152°
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il.i i i i i i)i 182o ..........
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400
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,1,300 ° dO
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FIG. I
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FIG. 2 ,
FIG. 1. Schematic illustration . .of, a .relaxation . curve: ~0--stress at moment of cessation of " increase in deformation, ~1--Stress after 1 hour. FIG. 2. Relaxation curves Of polyarylate P-2. 1/fl were constructed. One of.these Curves for p o l y a ~ t a t e P-2 is shown in Fig. 3. Analysis of this relationship shows clearly that lift remains constant over a cer.rain temperature interval, then falls s h a r p l y and finally decreases smoothly to unity at the softening point of the polyarylate. Thus the glassy state region Of these polyarylates is divided into two regions in which the temperature dependence of the relaxation rate is different. In the first region (up to 80 ° for P - ! and 150 ° for P-2) the reciprocal of the relative fall in stress, lift, remains Constant, indicating that the relaxation process is not sensitive to temperature. I n the second region i/fl decreases in a manner similar to that observed in m a n y Other polymers, i.e. the relaxation rate increases with increase in temperature. " In order to confirm with certainty the existence of these two regions with different relaxation mechanisms we determined the region of workability ( b y measurement of hardness) o f polyarylate P-2 b y the method described in reference [4]. It was shown in reference [4] that if stress relaxation involves a single mechanism (with one dependence of relaxation time on temperature) the curve defining the region of workability must fit the equation:
In
a U0-- 7a -aoo RT
(2)
1474
A.A.
AS~DSKIZ
where a is the stress, T the absolute temperature, R the universal gas constant and UQ, ~ and q~ are constants characterizing the polymer. The form of the curve desaribed b y ~his equation should be as illustrated in Fig. 4 (curve 2). • We carried out experiments over the temperature intervals from 20 ° to 320 ° (Fig. 4, curve 1 ) a n d from 180 ° to 320 ° (curve 2). I t is clearly seen from Fig. 4 that curve I does not fit equation (2) whereas curve 2 does fit this equation. It is interesting to note that the region of maximal curvature of curve 1 is in approximately the same temperature range as in Fig. 3.
"g/cm z 800
-
400
0
100
200 7",°C
3bO
FIG. 3
50
150
250 T,°C
FIG. 4
FIG. 3. Temperature dependence of the reciprocal of the relative fall in stress, I/p, for poly-
arylate P-2. FIG. 4. Curves defining the region of workability (by measurement of hardness) of polyarylate P-2:/--measurement started at 20°, 2--started at 180°. It has been clearly demonstrated that over the whole glassy-state region of polyarylate P-2 stress relaxation cannot follow any single mechanism, there being at least two such mechanisms. The question naturally arises of the nature of these two types of relaxation mechanism. At the present time, since the discovery of different types of supermolecular structure (these have been found in glassy polyarylates also [2]) it is evident that rearrangement of structure during relaxation can occur at different structural levels i.e. with involvement of smaller or larger elements of the supermolecular structure. The task arising from this, of constructing a structural theory of relaxation, which requires systematic studies to be made specially for this purpose is undoubtedly of great fu~ldamental interest. In conclusion the authors express their gratitude to G. L. Slonimskii for his interest in the work and for valuable advice, and to V. V. Korshak, S. V. Vinogradova and S. N. Salazkin for kindly providing the polyarylates for the investigation.
Modification of the structure of polyamides
1475
CONCLUSIONS (l) It is shown, with polyarylates in the glassy state as examples, that in the non-brittle glassy region a substantial change in the mechanism of relaxation occurs. (2) The glassy state region should be divided into two sub-states (excluding transition to the brittle state), between which there is yet another transition region. (3) The t y p e of transition discovered here is evidently particularly well manifested b y polymer glasses with rigid macromolecules, having high glass temperatures and consequently very large glassy-state temperature intervals. Translated by E. O. PHILLIP S REFERENCES
1. V. V. KORSHAK, S. V. VINOGRADOVA and S. N. SALAZKIN, Vysokomol. soyed. 4: 339, 1962 2. G. L. SLONIMSKII, V. V. KORSHAK, S. V. VINOGRADOVA, A. I. KITAIGORODSKII, A. A. ASKADSKII, S. N. SALAZKIN and Ye. M. BELAVTSEVA, Dokl. Akad. :Nauk SSSR 156: 924, 1964 3. G. A. DUBOV and V. R. REGEL', Zh. tekh. fiz. 25: 2542, 1955 4. G. L. SLONIMSKII and A. A. ASKADSKII, Mekhanika polimerov, No. 1, 36, 1965
MODIFICATION
OF T H E S T R U C T U R E
BY PHENOLFORMALDEHYDE
OF P O L Y A M I D E S OLIGOMERS*
A. V. YERMOLI~, I. ~I. ABR.~MOVAand V. A. ~ r s Scientific-Research Institute of Plastics (Received 10 June 1965)
FROM the fact that polymeric substances from a large variety of morphological types of supermolecular structure it has become obvious that the macroscopic properties of polymers must be associated not only with the chemical structure and mutual packing of the polymer chains, b u t also with their ability to exist in different structural forms. Consequently in the processing and use of polymeric materials there arises the most important task of creating structures in the polymer corresponding to the most valuable complex of properties for the prospective end use. However in most crystallizable polymers the amorphous fraction has a very low glass temperature and under conditions of use and storage there is a tend* Vysokomol. soyed. 8: :No. 8, 1346-1350, 1966.
....
i
A. A. ~ @ I { - L D R E I I
13. J. STAWITZ, Pharmaz, Ind., No. 3, 59, 1952 14. S. GLAESSON, Makromoi. Chem. 85: 83, 1960 15. CHIANG CHENG-YUAN, Opredelenlye molekulyarnyl~h ve/iov pol'lmerov. (Determina. tion of the Molecular Weight of Polymers.) p. 32, Foreign Lit. Publ. House, 1962 16. H. BARANSKA, Chemia Anal. 6: 1061, 1961 '
i ,'3
T W O T Y P E S OF R E L A X A T I O N IN GLASSY POLYARYYLATES*
A. A. ASKADSKII •
Institute of Hetevo-organio.Compounds, IJ.S.S.R. Academy of Sciences (Received 4 June 1965)
M ~ Y papers have been published on the relaxation properties 0f polymers in the high:elasti~ state, but problems associated with these properti6s in the glassy state have received little Study. I n this respect it is obviously of special interest to study the relaxation properties of rigid-chain polymers because in view of the large temperature range over which these polymers remain ih the glassy state the possibility is presented of making a detailed study of the temperature dependence of stress relaxation in the region where these polymers on the one hand do not display brittleness b u t - o n the 5ther hand do not soften. The materials chosen ~for s~udy-were polyarylates from isoph~halic and terephthalic acids with phenolphthalein (P-1 and P-2 respectively), of molecular Weight 48,000, prepared in ~-chloronaphthalene [1, 2]. Specimens o f the polyarylates in the f o r m of blocks were prel~ared by hot compression moulding and these were turned to cylinders of height 4.5 m m and diameter 3 r a m . Stress relaxation after uniaxial compression was studied over a w i d e r a n g e of temperatures in a micro-mechanical test machine [3]. For ~his purpose the specimens were rapidly compressed at a rate of 3 mm]min, after w h i c h the deformation, which in all cases was 4.4o//o, was kept constant during the whole experiment. The stress required to maintain this deformation was measured at set intervals of time, From these measurements the usual relaxation curve, represented schematically in Fig. 1, was obtained for each temperature: As a comparative characteristic of the relaxation properties of t h e polymers we took the reciprocal of the relative fall in Stress after relaxation for 1 hour. In terms of the values marked in Fig. 1 this value, 1[~, is given by 1
~.
~l~
0"(i - - 0" 1
* Vysokomol. soyed. 8: No. 8, 1342-1345, 1966..
(1)
1~73
Relaxatio~i~ in glassy pol~-arylates
where al is the s t r e s s after 1 ,hour and ~0 is t h e stress a t ' t h e m o m e n t of Cessation of deformation. -, ...... ' ~T e s t results for specimens of polyarylate P - 2 ~ r e given in ~ i g . 2. Similar curves were obtained for polyarylate P-1. I t is seen from lfig., 2 that in a cei~ain ~emperature region the relaxation curves! lie fairly close together and then at high temperatures t h e y gradually shift in the direction of lower stresses~ I n order to demonstrate more clearly the" temperature dependence of the relaxa~ tion properties o f these polyarylates curves ,of t h e temperature dependence of 6, g/cm 2 800
~
_
.
~
,
Time
•
.
.
200
:
_
--
.
;
.
.
.
.
.
.
.
.
.
.
.
152°
.
" -
""-
-204 °
. . . . . . . . . .
2oo, ~ _
i ....
_
il.i i i i i i)i 182o ..........
600
400
_
. "
~
,
•
20
• 40
,
•
270° .
,1,300 ° dO
T/me,
FIG. I
llT#l
FIG. 2 ,
FIG. 1. Schematic illustration . .of, a .relaxation . curve: ~0--stress at moment of cessation of " increase in deformation, ~1--Stress after 1 hour. FIG. 2. Relaxation curves Of polyarylate P-2. 1/fl were constructed. One of.these Curves for p o l y a ~ t a t e P-2 is shown in Fig. 3. Analysis of this relationship shows clearly that lift remains constant over a cer.rain temperature interval, then falls s h a r p l y and finally decreases smoothly to unity at the softening point of the polyarylate. Thus the glassy state region Of these polyarylates is divided into two regions in which the temperature dependence of the relaxation rate is different. In the first region (up to 80 ° for P - ! and 150 ° for P-2) the reciprocal of the relative fall in stress, lift, remains Constant, indicating that the relaxation process is not sensitive to temperature. I n the second region i/fl decreases in a manner similar to that observed in m a n y Other polymers, i.e. the relaxation rate increases with increase in temperature. " In order to confirm with certainty the existence of these two regions with different relaxation mechanisms we determined the region of workability ( b y measurement of hardness) o f polyarylate P-2 b y the method described in reference [4]. It was shown in reference [4] that if stress relaxation involves a single mechanism (with one dependence of relaxation time on temperature) the curve defining the region of workability must fit the equation:
In
a U0-- 7a -aoo RT
(2)
1474
A.A.
AS~DSKIZ
where a is the stress, T the absolute temperature, R the universal gas constant and UQ, ~ and q~ are constants characterizing the polymer. The form of the curve desaribed b y ~his equation should be as illustrated in Fig. 4 (curve 2). • We carried out experiments over the temperature intervals from 20 ° to 320 ° (Fig. 4, curve 1 ) a n d from 180 ° to 320 ° (curve 2). I t is clearly seen from Fig. 4 that curve I does not fit equation (2) whereas curve 2 does fit this equation. It is interesting to note that the region of maximal curvature of curve 1 is in approximately the same temperature range as in Fig. 3.
"g/cm z 800
-
400
0
100
200 7",°C
3bO
FIG. 3
50
150
250 T,°C
FIG. 4
FIG. 3. Temperature dependence of the reciprocal of the relative fall in stress, I/p, for poly-
arylate P-2. FIG. 4. Curves defining the region of workability (by measurement of hardness) of polyarylate P-2:/--measurement started at 20°, 2--started at 180°. It has been clearly demonstrated that over the whole glassy-state region of polyarylate P-2 stress relaxation cannot follow any single mechanism, there being at least two such mechanisms. The question naturally arises of the nature of these two types of relaxation mechanism. At the present time, since the discovery of different types of supermolecular structure (these have been found in glassy polyarylates also [2]) it is evident that rearrangement of structure during relaxation can occur at different structural levels i.e. with involvement of smaller or larger elements of the supermolecular structure. The task arising from this, of constructing a structural theory of relaxation, which requires systematic studies to be made specially for this purpose is undoubtedly of great fu~ldamental interest. In conclusion the authors express their gratitude to G. L. Slonimskii for his interest in the work and for valuable advice, and to V. V. Korshak, S. V. Vinogradova and S. N. Salazkin for kindly providing the polyarylates for the investigation.
Modification of the structure of polyamides
1475
CONCLUSIONS (l) It is shown, with polyarylates in the glassy state as examples, that in the non-brittle glassy region a substantial change in the mechanism of relaxation occurs. (2) The glassy state region should be divided into two sub-states (excluding transition to the brittle state), between which there is yet another transition region. (3) The t y p e of transition discovered here is evidently particularly well manifested b y polymer glasses with rigid macromolecules, having high glass temperatures and consequently very large glassy-state temperature intervals. Translated by E. O. PHILLIP S REFERENCES
1. V. V. KORSHAK, S. V. VINOGRADOVA and S. N. SALAZKIN, Vysokomol. soyed. 4: 339, 1962 2. G. L. SLONIMSKII, V. V. KORSHAK, S. V. VINOGRADOVA, A. I. KITAIGORODSKII, A. A. ASKADSKII, S. N. SALAZKIN and Ye. M. BELAVTSEVA, Dokl. Akad. :Nauk SSSR 156: 924, 1964 3. G. A. DUBOV and V. R. REGEL', Zh. tekh. fiz. 25: 2542, 1955 4. G. L. SLONIMSKII and A. A. ASKADSKII, Mekhanika polimerov, No. 1, 36, 1965
MODIFICATION
OF T H E S T R U C T U R E
BY PHENOLFORMALDEHYDE
OF P O L Y A M I D E S OLIGOMERS*
A. V. YERMOLI~, I. ~I. ABR.~MOVAand V. A. ~ r s Scientific-Research Institute of Plastics (Received 10 June 1965)
FROM the fact that polymeric substances from a large variety of morphological types of supermolecular structure it has become obvious that the macroscopic properties of polymers must be associated not only with the chemical structure and mutual packing of the polymer chains, b u t also with their ability to exist in different structural forms. Consequently in the processing and use of polymeric materials there arises the most important task of creating structures in the polymer corresponding to the most valuable complex of properties for the prospective end use. However in most crystallizable polymers the amorphous fraction has a very low glass temperature and under conditions of use and storage there is a tend* Vysokomol. soyed. 8: :No. 8, 1346-1350, 1966.