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Investigation of the effect of supermolecular structure on the relaxation properties of crystalline and amorphous polymers
Relaxation properties of crystalline and amorphous polymers
433
8. Yu. A. ZUBOV, G. S. MARKOVA and V. A. KARCIN, Vysokomol. soyed. 5: 1171, 1963 (Translated in Polymer Sci. U.S.S.R, 5: No. 2, 1961) 9. G. FARROX, Polymer 1: 518, 1960 10. D. Ya. TSVANKIN, Vysokomol. soyed. 6: 2078, 2083, 1964 (Translated in P o l y m e r Sci. U.S.S.R. 6: 11, 2304; 2310, 1964) 11. A. TAYLOR and H. SINCLAIR, Proc. Phys. Soc. A57: 108, 1945 12. Yu. A. ZUBOV and D. Ya. TSVANKIN, Vysokomol. soyed. 6: 2131, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 12, 2358, 1964) 13. Ch. RUSCHER and V. SCHRODER, Faserforseh und Textiltechn. 11: 165, 1960 14, H. C. KILIAN, H. HALROTH and E. JENKEL, Kolloid.-Z., 172: 166, 1960 15, R. P. I)AUBENY, C. W. BUNN and C. J. BROWN, Proc Roy, Soc, A226: 531, 1954
INVESTIGATION OF THE EFFECT OF SUPERMOLECULAR STRUCTURE ON THE RELAXATION PROPERTIES OF CRYSTALLINE AND AMORPHOUS POLYMERS* V. I. PAVLOV, A. A. ASKADSKIIand G. L. SLOI~'IMSKII Institute for Elementary Organic Compounds, U.S.S.R. Academy of Sciences I n s t i t u t e for the Chemistry of High Molecular Compounds, Ukrainian S.S.R. A c a d e m y of Sciences
(Received 25 May 1966) THE objective of the present work was a structural and mechanical investigation of monolithic crystalline and solid amorphous polymers, with the aim of establishing quantitative connections between the characteristics of their supermolecular structures and the parameters of their relaxation properties. EXPERIMENTAL Two polymers, which m a y exist in different phase states, were selected as the experimental materials; crystalline isotactic polypropylene, in which different supermolecular structures m a y be obtained comparatively easily [1-8], and amorphous polyarylates, which are exceptionally interesting new glassy polymers with rigid macromolecules [9-11]. The different supermolecular structures in the bulk polypropylene specimens were obtained from the melt b y the method of changing the cooling rate during pressing. F o r the investigation, a highly crystalline isotactic polypropylene "Moplen" was used in t h e form of granules with an intrinsic viscosity [F/]=3.83, as measured in tetralin at 135°C. A pressing regime was selected for the preparation of the specimens which m a d e it possible to obtain a structure, the elements of which were individual spherulites; the regime eliminated the appearance of various supra-spherulitic formations which are known [3, 12] to exert an effect on t h e mechanical properties of the polymer body. The specimens were * Vysokomol. soyod. A9: :No. 2, 385-392, 1967.
434
V . I . PAVLOV et at.
pressed u n d e r a pressure of 100 kg/mm 2 and held at 240°C for 30 min. The rate of cooling of the pressed shapes was varied in the range from 0.2 to 600°C/min. As a result, five types of bulk specimens of isotactic polypropyleno wore obtained; these differed in the dimensions of the sphcrulites, the characteristics of which are shown in Table 1. The polyarylato selected to be studied, made from isophthalic acid and phenolphthaloin (P-l), could be prepared with two forms of supermolocular structure depending on the conditions under which the synthesis was carried out; namely, globular, and predominantly fibrillar (with the same chemical structure of the chain) [13J. Polyarylates synthesized in a medium of ditolylmethano had a stable globular supormolecular structure, and those TABLE
1.
EFFECT
OF F O R M I N G
CON-DITIONS
ON S T R U C T U R E F O R M A T I O N (AVERAGE SIZE OF STRUCTURAL ELEMENTS)
I N B U L K SPECII~ENS
OF ISOTACTIC P O L Y P R O P Y L E N E
Specimen No.
Cooling rate of specimen during pressing, deg/min
Average size of the structural elements (spherulites), g
600 8.5 1.75 0.38 0.2
25 80 175 350 475
synthesized in a medium of ~-chloronaphthaleno had a predominantly fibrillar structure. The molecular weights of the two types of polyarylates wore the same (36000*). The monolithic specimens from these polyarylates wore obtained b y hot pressing at 310°C with a specific pressure of 600 kg/cm t. The study of the stress relaxation at constant relative compression strain was carried out on specimens 4 × 4 × 6 m m (for polypropylenot) and 3 × 3 × 4.5 m m (for polyarylatos) over a wide temperature range on a stress relaxation machine of Rogel' design [14]. This stress relaxation machine is characterized b y the groat rigidity of the measuring system a n d the automatic recording of the quantities to be measured. This value of the given strain for polypropyleno speeimons was 5.8~o, and for the polyarylates, 4"8~o. The relaxation tests were carried out for 1 hr. * Determined b y the light scattering method in solution. t Preliminary investigations of the process of structure formation in bulk specimens of polypropylene revealed a considerable non-uniformity in the different sections of the specimen, this being caused b y the presence of a gradient in the rate of cooling through the specimen section. This fact considerably complicates the elucidation of quantitative relationships between the supcrmolecular structure and mechanical properties. Therefore, to carry o u t the mechanical tests, comparatively large fiat blocks were pressed, from the central part of which specimens 4 × 4 × 6 m m in size were cut. This considerably reduced the structural non-uniformity in the specimens to be tested.
435
Relaxation properties of crystalline and amorphous polymers
The structural investigations of the bulk specimens of isotactic polypropylene were c a r r i e d o u t o n a M I N - 8 p o l a r i z i n g m i c r o s c o p e in t r a n s m i t t e d p o l a r i z e d l i g h t ( × 100). T h i n s e c t i o n s f r o m t h e b u l k s p e c i m e n s w e r e o b t a i n e d b y m o a n s o f a sledge m i c r o t o m e . T h e p h o t o g r a p h y o f t h e l i g h t - o p t i c a l p i c t u r e s w a s c a r r i e d o u t w i t h a " Z e n i t h - 3 M " c a m e r a . Microscopic p i c t u r e s o f t h e s u p e r m o l e c u l a r s t r u c t u r e s in t h e p o l y a r y l a t e s w e r e o b t a i n e d o n a UEM-V-100 e l e c t r o n m i c r o s c o p e ( x 85000). T h e q u a n t i t a t i v e p a r a m e t e r s o f t h e stress r e l a x a t i o n process w e r e d e t e r m i n e d f r o m t h e e x p e r i m e n t a l r e l a x a t i o n c u r v e s b y m e a n s o f m e t h o d s d e v e l o p e d b y us p r e v i o u s l y [15].
EXPERIMENTAL RESULTS AND DISCUSSION
Crystalline isotacti~ polypropylene. To throw light on the quantitative connections between the characteristics of supermolecular structures and the me chanical property parameters of crystalline polymers, the relaxation behaviour of five types of bulk specimens of isotactic polypropylene was investigated under conTABLE
2. ]~FFECT
OF '±'li.~ D I M E N S I O N S
OF S U P E R M O L E C U L A R S T R U C T U R A L E L E M E N T S
IN
]3U'LK SPEC1MEI~'S OF ISOTACTIC POLYPROPYI,EI~IE ON T H E PARAM]gTERS OF T H E R E L A X A T I O I ~ P R O P E R T I E S OF T H E P O L Y M E R
Specimen No.
Test temperature, °C 18 40 62 87 100 128 18 40 84 100 129 19 51 75 100 130 17 43 77 112 136 14 41 61 82 102 133
E~
E0~
kg/cm ~
kg/cm 2
1413 1085 1007 1027 1033 700 1760 1518 1077 965 561 1890 1510 1242 932 5OO 2140 1745 1077 730 364 2650 2210 1760 1207 862 362
6580 2050 2270 1077 259 3O2 3400 lll7 788 676 177 6420 1213 1785 787 286 4000 1680 1505 511 2O0 4140 1672 1363 1085 743 359
r, m i n
0.13 0.21 0.12 1.83 5.5 53.1 5-6 5.5 9.0 1.35 13.0 0.4 5.6 1.5 4.8 39.8 4.8 5.4 4.8 11.5 55.9 8.3 7-3 7.2 8.8 2.5 0.5
J/, poise
0.271 0.281 0.234 0-246 0.477 0.441 0.2 0.431 0.295 0.202 0.588 0.114 0.344 0.192 0.247 0.414 0-176 0.319 0.222 0.397 0.524 0.197 0.550 0.474 0.848 0.265 0.241
1.739 1.551 1.641 0.862 0.436 0.173 0.708 0.480 0.523 0.941 0.221 1.110 0.553 0.925 0.679 0.218 0-758 0.584 0.706 0.379 0.121 0.659 0.336 0.393 0.158 0.785 1.182
7"78 x 1011 3"23 X 10 n 6'05 x lO u 2"82 × 10 tz 1.87 × 10 n 2.49 >, 101~ 1'37 × 10 t~ 1"01 x 10 la 4.25 X 1012 6"0 :< 10 t~ 2"17 × 1011 3.24 × 10 t~ 2" 18 × 10 lz 2"72 X lO ts 5"93 × 10 TM 2.32 X 10 ~z 4.77 × 1014 3"85 × 1012 2.31 X 10 ta 1" 18 × 1012 1"23 X 10 t~ 2-78 X 1014 6"72 × 1011 1-31 X 1012 1"08 × 1012 1.92 × 1012 3'20 X 1011
436
V.I.
PAVLOV et al.
ditions of uniaxial compression in the temperature range from 14 to 136°C, the specimens differing in spherulite dimensions. As a result of this investigation, stress relaxation curves were obtained for all the dimensions of the spherulitic structures at various temperatures, which could be satisfactorily described b y the Kohlrauseh equation: a (t) = a ~ +aoe ~tk = E ~ - E @ e -ark where t is the time; a~ and E~ are the equilibrium stress and elastic modulus; a0 and E 0 are the relaxed parts of the stress and elastic modulus respectively; a and k are constants. B y means of the method referred to in [15] the parameters of the Kohlrauseh equation were calculated from these curves; these parameters characterize the relaxation properties of the material (equilibrium stress a~, relaxed portion of the stress a o, or the equilibrium and relaxed modulus of elasticity E~----a~/~ and E o =ao/e), the relaxation time v = 1/a k, the constants a and k, and also the viscosity parameter ~/=F0v (1 q-I/k). These data are shown in Table 2. In this way, quanti-
~Y,~, kg / crnz 200
,!
I00
5g
0
//' '/
Tnt,°C 125L
I
loo I ~
\~.ii !
751 0
t
L 20
I
"e FIG. 1
I 40
I
I
5'O t, rntn
FIG. 2
FIG. 1. Relation between the equilibrium stress, ace, T and average spherulite dimension d in three-dimensional coordinates. FTQ. 2. R e l a t i o n b e t w e e n t h e t e m p e r a t u r e Tnt a n d t h e d u r a t i o n of t h e r e l a x a t i o n process t.
tative relationships were obtained between the parameters of the Kohlrausch equation, the temperature (T) and the average spherulite size (d). These relationships are shown in Fig. 1 for the equilibrium stress in three-dimensional coor4inates (a~, T, d).
Relaxation properties of crystalline and amorphous polymers
437
It may be seen from Fig. 1 that specimens with the ooarser spherulites have, at temperatures below 92°C, a greater value for the equilibrium stress (and, consequently, also for the equilibrium modulus of elasticity E®) than the specimens with fine spherulites, but above 92°C, the contrary is observed. Thus, the reduction in a~ (or E®) with an increase in temperature takes place approximately linearly for the coarse spherulitic structures, whereas the curve for the temperature dependence of a~ for fine spherulitic structures has its own course in the various temperature intervals. This curve has two sharp inflections and a horizontal portion with a stable equilibrium stress ~ (or E~) over a comparatively wide temperature region (from 40 to 100°C); this fact should have a certain practical interest in the use of polymers in designs and machine components working over a wide temperature interval under load. Moreover, extrapolation of the temperature relationships obtained for the various spherulitic structures towards higher temperatures shows that they converge towards a single straight line (at which the equilibrium stresses ~ fall to zero) corresponding to a temperature of 160°C, which is the melting point of isotactic polypropylene. The trend mentioned for the temperature dependence of the equilibrium stress a~ (or E~) is evidence of the fact that there exists a certain temperature Tn~ (in our case ~ 92°C) at which all spherulitie structures exhibit the same equilibrium elastic properties. From Fig. 1 it may also be seen that the greatest dependence of a® on average spherulite size is observed at low temperatures (20-40°C) at which the value of a~ (and consequently of E~) increases by a factor of approximately 2 with an increase in average spherulite size from 25 to 475/~. Increase in temperature leads to a gradual fall-off in this relationship, which ends at Tn~----92°, and above this temperature its qualitative characteristics alter; with an increase in spherulite size (within the range investigated by us) the equilibrium stress a® (or E~) falls somewhat. If the monotonic character of the relationship between a~ and temperature may be easily explained for the coarse spherulitic structures, starting from the stability of the structural elements (perfect, definitely shaped spherulites cannot grow further), then the character for the graph of the temperature dependence of a~ for the fine spherulitic structure, having two inflections and a region of stable elastic properties, gives at first glance a basis for supposing that, with an increase in temperature, further growth of the fine spherulites takes place in the stress field. Some investigations of other authors also give evidence of this [16, 17]. Comparative optical investigations of specimens before and after relaxation tests at 92°C indicated that externally (spherulite dimensions, degree of perfection and defectiveness) they hardly differ at all. This indicates that the observed differences in the temperature dependences of the stress or elastic modulus are not connected with any change in the spherulite dimensions during the process of the experiment. Consequently, these should be caused by a change in the fine structure of the sphcrulites themselves, and this presents a very interesting problem for electron microscope investigations.
438
V . I . PAVLOVet
a~.
In view of the large dispersion in the value of the remaining parameters in the Kohlrausch equation, namely, a o (or E0), z, a and k and also 0, the dependence of these on temperature and spherulite size are shown in Table 2. Analysis of the relationships between the kinetic parameters of the Kohlrauseh equation and the temperature and spherulite size (Table 2), and also the optical observations, make it possible to draw the conclusion t h a t the large scatter in their values is connected in the first place with a considerable non-uniformity and defectiveness in the specimens' structure, which, although it was considerably reduced by the use of special measures for preparing the specimens, nevertheless still remained comparatively large; and, in the second place with the impossibility of strictly Observing the ideal conditions for carrying out the stress relaxation experiment *. I n this way, it m a y be seen from what has been put forward above t h a t there exists a temperature (in our case, Tn®:92°C), at which the equilibrium stress is the same for all the spherulite sizes investigated. Similar temperature dependences were also obtained for the equilibrium stresses corresponding to given times of relaxation (0, 5, 30, 60 rain). Consequently, the observed trend in these temperature dependences is evidence of the fact t h a t for a n y given duration of the relaxation process there exists a value of the temperature T~t at which all the spherulite structures exhibit the same elastic properties. With an increase in the relaxation times t, these temperatures T~t fall, tending to a limit (Fig. 2). I t is interesting to note t h a t this relationship is well described by the same Kohlrausch function. Therefore, having formally applied this relationship by use of the method in [15], it was possible to calculate the equilibrium value of the temperature Tn~ which turned out also to be equal to 92°C, t h a t is, it coincides with the value of this quantity found from the temperature dependence of the equilibrium stress for spherulite structures differing in dimensions, which had been discussed previously (Fig. 1). From all t h a t has been said above, it is clear t h a t at the temperature T.: the stresses (and, consequently, the elastic modulus as well) will be the same at any time t for all structures. In particular, this makes it possible to write down by means of the Kohlrausch equation the following equality, which must be obeyed at * Necessary conditions for carrying out the stress relaxation experiment are that the deformation should be applied instantaneously and held constant during the experiment. Whereas the latter condition was strictly cbserved in our case (the dynamometer had a large rigidity), under the real conditions of the experiment the time taken to apply the deformation was always finite. Therefore, during the time when the deformation was applied to the specimen, part of the stress in it was able to relax. In carrying out the investigations at a raised temperature, the relative value of the loss in stress during the time of application of the deformation will be greater at higher temperatures than at lower temperatures. The difficulty in allowing for these losses also leads to a greater or smaller deviation of the values of the kinetic parameters from the actual values, that is, to a large dispersion in the calculated values of the parameters in the Kohlrausch equation obtained by us.
Relaxation properties of crystalline and amorphous polymers
439
this temperature, for the two structures with the extreme, spherulite dimensions E¢¢+Eoe-(#~)k = E~ + E'oe-(tl~')k' where t is the time of stress relaxation, E~, E0, r, and k are the parameters of the relaxation process according to Kohlrausch for the fine spherulite structure which depend on temperature; E ' , E~, z' and k' are the corresponding parameters for the coarse spherulite structure. At the present time, hovewer, there is no possibility of giving this equation in the form of an explicit relationship between t and T,t, since the accurate data required for this about the temperature dependence of the kinetic parameters in the Kohlrausch equation are not available. Clarification of these relationships is a very important task in further investigations, which will make it possible to throw light on new parameters, which will include the dimensions of the supermolecular structures and will quantitatively characterize their effect on the polymer properties. Amorphous polyarylates. To clarify the effect of the type of supermolecular structure on the mechanical propetries of amorphous polymers, stress relaxation under uniaxial compression was investigated in bulk specimens of the globular and fibrllar poylarylate P-1 over the temperature range 20-245°C. Stress relaxation curves were obtained experimentally over these temperatures for both types of supermolecular structure, and from these curves the parameters of the relaxation properties were determined by means of the method referred to in [15]. Almost all the relaxation curves for the globular polyarylate are described well by the Kohlrausch equation. At the same time, the majority of the curves for this same polyarylate, but having a predominantly fibrillar supermolecular structure, do not in general obey this equation, or do not obey it over the whole of their course*. This fact is again evidence that the relaxation properties of amorphous glassy polyary!ates are determined not only by their chemical structure, but also by their physical structure at the supermolecular level. As a result of the experiments carried out and the calculations for both types of polyarylate it was possible to establish the relationship between the relaxed equilibrium stress a~ and temperature (Fig. 3). As m a y be seen, the values of a~ decrease monotonically with an increase in temperature, falling to zero at the corresponding softening points for these types of polymer. Thus, for the globular polyarylate the values of equilibrium stress were greater than those for the fibrillar polyarylate ar temperatures < 140°C, but at temperatures > 140°C the reverse was true, that is, relationship is similar to that discussed previously for crystalline polypropylene. This means that at low temperatures the stress relaxation takes place more rapidly and to a greater extent in the fibrillar polymer, but at high temperatures in the globular polymer. Such a trend in the rates of the relaxation * In connection with this, only the value of the equilibrium stress a~ was calculated for the latter curves.
440
V . I . PArLor et al.
processes is evidently caused by the fact that at low temperatures the fibrillar structure has a greater internal mobility (the polymer is not so hard), whereas at high temperatures the globular structure undergoes a more rapid partial breakdown under stress. This appears especially noticeable at the softening points, at which the breakdown of secondary formations into the elements from which they are made begins. Thus for the globular polyarylate, the structure of which is formed from coiled macromoleeules, this breakdown sets in at lower temperatures (Fig. 3), since the spherical shaped particles and the clusters of these particles ~..,kg/cm 2
800 GO0 ~00 200
o
x K
I
~o
12o
\
2oo
\i
zgo r,°c
FIG. 3. Temperature dependence of the equilibrium stress a~ for (1) globular and (2) fibrillar polyarylates. are connected together comparatively weakly. In the ease of the fibrillar supermolecular structure, formed from elongated bundles in which uncoiled macromolecules are grouped together, this breakdown sets in at higher temperatures since the interaction between the elements of the structure is here strong. In this way, from what has been proposed above the conclusion m a y be drawn that, on going from low to high temperatures the relationship between the relaxation process mechanisms, caused by the difference in supermolecular structures, changes. The presence of a point of intersection of the curves in Fig. 3 is in agreement with this. Similar intersecting relationships were also obtained for nonequilibrium stresses (or elastic moduli), corresponding to given relaxation times (0, 5, 30 and 60 rain). The presence of a point of intersection between the lines for the temperature dependence of the stress (or elastic modulus) for a polyarylate having different types of supermoleeular structure is evidence for the fact that at the temperature corresponding to the point of intersection, a change in the type of supermolecular structure has no effect on the elasticity of the polymer body. The temperature dependences of the kinetic parameters of the Kohlrausch equation and the viscosity parameter ~/are shown in Fig. 4. With an increase in the temperature of the globular polyarylate, the relaxed part of the stress a o and the parameter a increase smoothly, but the parameter k falls linearly in the range from 0.46 to 0.24; ~/ decreases slightly over the range investigated by us (from 5 × 10TMto 5 × 1011poise). For the fibrillar polyarylate, the temperature dependence
Relaxation properties of crystalline and amorphous polymers
441
of these parameters could not succesfully be established because of the large scatter in their values. In this way, the presence of fairly clearly defined temperature relationships for these parameters in the case of globular structures, and their absence in the case of fibrillar structures, makes it possible to conclude that the globular polyarylate is more uniform than the fibrillar polyarylate in its physical structure; this is in good agreement with electron-microscope investigations [13]. g/cmz
n pof,~e
v, m/n
7)xF~
125~ -
~
10 z°~
/1o \ 755
l'O 0"5
5
'
,
I
,
o 5o too ,:o 2oo
05
o o
04'
25~ 0
Jo
'
250 0 50 I00 ISOT,~C0 50 100 I50 200T,~ O 50 ZOO I50 200 2~TW
FIG. 4. Temperature dependence of the kinetic parameters in the Kohlrausch equation. a0, relaxed part of the stress; a and k, parameters; T, relaxation time; t/, viscosity. The investigation carried out b y us on the quantitative level indicates that the relaxation properties of polymers existing in the amorphous state (and not only in the crystalline state) depend on their supermolecular structure as well as on their chemical structure. From the practical point of view, the results obtained indicate that, in the use of polyarylate P-1 in rigid constructions under load*, at low temperatures it is more suitable to use a polyarylate with a globular supermolecular structure, and at high temperatures a polyarylate with a fibrillar supermolecular structure. In this way, the present work indicates that the study of relaxation processes uncovers wide possibilities both for the quantitative investigation of the connection between mechanical properties and the supermolecular structure of polymer bodies, and also for the correct and thorough utilization of polymers having a certain chemical structure. CONCLUSIONS
(1) For the particular case of monolithic crystalline isotactio polypropylene and the amorphous glassy polyarylate prepared from isophthalic acid and phenolphthalein, a quantitative investigation has been made of the effect of the characteristics of the supermolecular structure on the parameters of the relaxation properties over a wide temperature interval. * Static loading is envisaged here, because under dynamic conditions the globular polyarylate is less suitable for use because of its high brittleness.
442
K. KH. RAZIKOV et al.
(2) It has been quantitatively demonstrated that the relaxation properties of polymers existing both in the crystalline and also in the glassy state depend on the type and dimensions of the elements of the supermolecular structure as well as on their chemical structure. (3) I t has been established that for any particular duration of the relaxation process in the crystalline and amorphous polymers investigated, there exist temperatures at which the elastic properties do not depend on the supermolecular structure of the polymer body. Translated by G. F. ~V[ODLEN REFERENCES 1. 2. 3. 4. 5.
F. J. PADI)EN and H. D. K E I T H , J. App]. Phys. 16: 1479, 1959 T. I. SOGOLOVA, Dissertation, ]963 G. P. ANDRIANOVA, Dissertation, 1963 L. I. NAD_~LI~EISHVILI, Dissertation, 1964 V. A. KARGIN, N. F. BAKEYEV, LI LI-SHEN and T. S. OCH_APOVSKAYA, Vysokomol. soyed. 2: 1280, 1960 (Translated in Polymer Sei. U.S.S.R. 3: 2, 291, 1962) 6. B. G. RANBY, F. F. MOREHEAD and N. W. WALTER, J. Polymer Sci. 44: 349, 1960
CHANGES IN THE SUPERMOLECULAR STRUCTURE OF CELLULOSE AFTER TREATMENT WITH CERTAIN ACTIVATING REAGENTS*t K. K~. RAzmov, E. D. TYAGAI, 13.P. LARnV and K~. U. USMAXOV Institute of Chemistry and Technology of Cotton Cellulose (Received 2 July 1966)
Du~ to its peculiar supermolecular structure, natural cellulose is known to be an inactive polymer. To produce its wide variety of derivatives, the cellulose must therefore be activated. This usually consists in loosening up its microstrueture by some treatment or other. One way of increasing the chemical activity of cellulose preparations is t h a t of inclusion, which consists in swelling the cellulose and fixing this state by treatment in certain organic materials [1]. Different kinds of amines are often used for activation [2-5]. Swelling in a mixture of glycerine and water is also known for cellulose it causes the microstructure to loosen Ul5, and therefore increases the reactivity of cellulose. * Vysokomol. soyed. A9. No. 2, 393-397, 1967. t 2nd Report of the series "Influence of different treatments on the mJerostrueture of cellulose fibres".
433
8. Yu. A. ZUBOV, G. S. MARKOVA and V. A. KARCIN, Vysokomol. soyed. 5: 1171, 1963 (Translated in Polymer Sci. U.S.S.R, 5: No. 2, 1961) 9. G. FARROX, Polymer 1: 518, 1960 10. D. Ya. TSVANKIN, Vysokomol. soyed. 6: 2078, 2083, 1964 (Translated in P o l y m e r Sci. U.S.S.R. 6: 11, 2304; 2310, 1964) 11. A. TAYLOR and H. SINCLAIR, Proc. Phys. Soc. A57: 108, 1945 12. Yu. A. ZUBOV and D. Ya. TSVANKIN, Vysokomol. soyed. 6: 2131, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 12, 2358, 1964) 13. Ch. RUSCHER and V. SCHRODER, Faserforseh und Textiltechn. 11: 165, 1960 14, H. C. KILIAN, H. HALROTH and E. JENKEL, Kolloid.-Z., 172: 166, 1960 15, R. P. I)AUBENY, C. W. BUNN and C. J. BROWN, Proc Roy, Soc, A226: 531, 1954
INVESTIGATION OF THE EFFECT OF SUPERMOLECULAR STRUCTURE ON THE RELAXATION PROPERTIES OF CRYSTALLINE AND AMORPHOUS POLYMERS* V. I. PAVLOV, A. A. ASKADSKIIand G. L. SLOI~'IMSKII Institute for Elementary Organic Compounds, U.S.S.R. Academy of Sciences I n s t i t u t e for the Chemistry of High Molecular Compounds, Ukrainian S.S.R. A c a d e m y of Sciences
(Received 25 May 1966) THE objective of the present work was a structural and mechanical investigation of monolithic crystalline and solid amorphous polymers, with the aim of establishing quantitative connections between the characteristics of their supermolecular structures and the parameters of their relaxation properties. EXPERIMENTAL Two polymers, which m a y exist in different phase states, were selected as the experimental materials; crystalline isotactic polypropylene, in which different supermolecular structures m a y be obtained comparatively easily [1-8], and amorphous polyarylates, which are exceptionally interesting new glassy polymers with rigid macromolecules [9-11]. The different supermolecular structures in the bulk polypropylene specimens were obtained from the melt b y the method of changing the cooling rate during pressing. F o r the investigation, a highly crystalline isotactic polypropylene "Moplen" was used in t h e form of granules with an intrinsic viscosity [F/]=3.83, as measured in tetralin at 135°C. A pressing regime was selected for the preparation of the specimens which m a d e it possible to obtain a structure, the elements of which were individual spherulites; the regime eliminated the appearance of various supra-spherulitic formations which are known [3, 12] to exert an effect on t h e mechanical properties of the polymer body. The specimens were * Vysokomol. soyod. A9: :No. 2, 385-392, 1967.
434
V . I . PAVLOV et at.
pressed u n d e r a pressure of 100 kg/mm 2 and held at 240°C for 30 min. The rate of cooling of the pressed shapes was varied in the range from 0.2 to 600°C/min. As a result, five types of bulk specimens of isotactic polypropyleno wore obtained; these differed in the dimensions of the sphcrulites, the characteristics of which are shown in Table 1. The polyarylato selected to be studied, made from isophthalic acid and phenolphthaloin (P-l), could be prepared with two forms of supermolocular structure depending on the conditions under which the synthesis was carried out; namely, globular, and predominantly fibrillar (with the same chemical structure of the chain) [13J. Polyarylates synthesized in a medium of ditolylmethano had a stable globular supormolecular structure, and those TABLE
1.
EFFECT
OF F O R M I N G
CON-DITIONS
ON S T R U C T U R E F O R M A T I O N (AVERAGE SIZE OF STRUCTURAL ELEMENTS)
I N B U L K SPECII~ENS
OF ISOTACTIC P O L Y P R O P Y L E N E
Specimen No.
Cooling rate of specimen during pressing, deg/min
Average size of the structural elements (spherulites), g
600 8.5 1.75 0.38 0.2
25 80 175 350 475
synthesized in a medium of ~-chloronaphthaleno had a predominantly fibrillar structure. The molecular weights of the two types of polyarylates wore the same (36000*). The monolithic specimens from these polyarylates wore obtained b y hot pressing at 310°C with a specific pressure of 600 kg/cm t. The study of the stress relaxation at constant relative compression strain was carried out on specimens 4 × 4 × 6 m m (for polypropylenot) and 3 × 3 × 4.5 m m (for polyarylatos) over a wide temperature range on a stress relaxation machine of Rogel' design [14]. This stress relaxation machine is characterized b y the groat rigidity of the measuring system a n d the automatic recording of the quantities to be measured. This value of the given strain for polypropyleno speeimons was 5.8~o, and for the polyarylates, 4"8~o. The relaxation tests were carried out for 1 hr. * Determined b y the light scattering method in solution. t Preliminary investigations of the process of structure formation in bulk specimens of polypropylene revealed a considerable non-uniformity in the different sections of the specimen, this being caused b y the presence of a gradient in the rate of cooling through the specimen section. This fact considerably complicates the elucidation of quantitative relationships between the supcrmolecular structure and mechanical properties. Therefore, to carry o u t the mechanical tests, comparatively large fiat blocks were pressed, from the central part of which specimens 4 × 4 × 6 m m in size were cut. This considerably reduced the structural non-uniformity in the specimens to be tested.
435
Relaxation properties of crystalline and amorphous polymers
The structural investigations of the bulk specimens of isotactic polypropylene were c a r r i e d o u t o n a M I N - 8 p o l a r i z i n g m i c r o s c o p e in t r a n s m i t t e d p o l a r i z e d l i g h t ( × 100). T h i n s e c t i o n s f r o m t h e b u l k s p e c i m e n s w e r e o b t a i n e d b y m o a n s o f a sledge m i c r o t o m e . T h e p h o t o g r a p h y o f t h e l i g h t - o p t i c a l p i c t u r e s w a s c a r r i e d o u t w i t h a " Z e n i t h - 3 M " c a m e r a . Microscopic p i c t u r e s o f t h e s u p e r m o l e c u l a r s t r u c t u r e s in t h e p o l y a r y l a t e s w e r e o b t a i n e d o n a UEM-V-100 e l e c t r o n m i c r o s c o p e ( x 85000). T h e q u a n t i t a t i v e p a r a m e t e r s o f t h e stress r e l a x a t i o n process w e r e d e t e r m i n e d f r o m t h e e x p e r i m e n t a l r e l a x a t i o n c u r v e s b y m e a n s o f m e t h o d s d e v e l o p e d b y us p r e v i o u s l y [15].
EXPERIMENTAL RESULTS AND DISCUSSION
Crystalline isotacti~ polypropylene. To throw light on the quantitative connections between the characteristics of supermolecular structures and the me chanical property parameters of crystalline polymers, the relaxation behaviour of five types of bulk specimens of isotactic polypropylene was investigated under conTABLE
2. ]~FFECT
OF '±'li.~ D I M E N S I O N S
OF S U P E R M O L E C U L A R S T R U C T U R A L E L E M E N T S
IN
]3U'LK SPEC1MEI~'S OF ISOTACTIC POLYPROPYI,EI~IE ON T H E PARAM]gTERS OF T H E R E L A X A T I O I ~ P R O P E R T I E S OF T H E P O L Y M E R
Specimen No.
Test temperature, °C 18 40 62 87 100 128 18 40 84 100 129 19 51 75 100 130 17 43 77 112 136 14 41 61 82 102 133
E~
E0~
kg/cm ~
kg/cm 2
1413 1085 1007 1027 1033 700 1760 1518 1077 965 561 1890 1510 1242 932 5OO 2140 1745 1077 730 364 2650 2210 1760 1207 862 362
6580 2050 2270 1077 259 3O2 3400 lll7 788 676 177 6420 1213 1785 787 286 4000 1680 1505 511 2O0 4140 1672 1363 1085 743 359
r, m i n
0.13 0.21 0.12 1.83 5.5 53.1 5-6 5.5 9.0 1.35 13.0 0.4 5.6 1.5 4.8 39.8 4.8 5.4 4.8 11.5 55.9 8.3 7-3 7.2 8.8 2.5 0.5
J/, poise
0.271 0.281 0.234 0-246 0.477 0.441 0.2 0.431 0.295 0.202 0.588 0.114 0.344 0.192 0.247 0.414 0-176 0.319 0.222 0.397 0.524 0.197 0.550 0.474 0.848 0.265 0.241
1.739 1.551 1.641 0.862 0.436 0.173 0.708 0.480 0.523 0.941 0.221 1.110 0.553 0.925 0.679 0.218 0-758 0.584 0.706 0.379 0.121 0.659 0.336 0.393 0.158 0.785 1.182
7"78 x 1011 3"23 X 10 n 6'05 x lO u 2"82 × 10 tz 1.87 × 10 n 2.49 >, 101~ 1'37 × 10 t~ 1"01 x 10 la 4.25 X 1012 6"0 :< 10 t~ 2"17 × 1011 3.24 × 10 t~ 2" 18 × 10 lz 2"72 X lO ts 5"93 × 10 TM 2.32 X 10 ~z 4.77 × 1014 3"85 × 1012 2.31 X 10 ta 1" 18 × 1012 1"23 X 10 t~ 2-78 X 1014 6"72 × 1011 1-31 X 1012 1"08 × 1012 1.92 × 1012 3'20 X 1011
436
V.I.
PAVLOV et al.
ditions of uniaxial compression in the temperature range from 14 to 136°C, the specimens differing in spherulite dimensions. As a result of this investigation, stress relaxation curves were obtained for all the dimensions of the spherulitic structures at various temperatures, which could be satisfactorily described b y the Kohlrauseh equation: a (t) = a ~ +aoe ~tk = E ~ - E @ e -ark where t is the time; a~ and E~ are the equilibrium stress and elastic modulus; a0 and E 0 are the relaxed parts of the stress and elastic modulus respectively; a and k are constants. B y means of the method referred to in [15] the parameters of the Kohlrauseh equation were calculated from these curves; these parameters characterize the relaxation properties of the material (equilibrium stress a~, relaxed portion of the stress a o, or the equilibrium and relaxed modulus of elasticity E~----a~/~ and E o =ao/e), the relaxation time v = 1/a k, the constants a and k, and also the viscosity parameter ~/=F0v (1 q-I/k). These data are shown in Table 2. In this way, quanti-
~Y,~, kg / crnz 200
,!
I00
5g
0
//' '/
Tnt,°C 125L
I
loo I ~
\~.ii !
751 0
t
L 20
I
"e FIG. 1
I 40
I
I
5'O t, rntn
FIG. 2
FIG. 1. Relation between the equilibrium stress, ace, T and average spherulite dimension d in three-dimensional coordinates. FTQ. 2. R e l a t i o n b e t w e e n t h e t e m p e r a t u r e Tnt a n d t h e d u r a t i o n of t h e r e l a x a t i o n process t.
tative relationships were obtained between the parameters of the Kohlrausch equation, the temperature (T) and the average spherulite size (d). These relationships are shown in Fig. 1 for the equilibrium stress in three-dimensional coor4inates (a~, T, d).
Relaxation properties of crystalline and amorphous polymers
437
It may be seen from Fig. 1 that specimens with the ooarser spherulites have, at temperatures below 92°C, a greater value for the equilibrium stress (and, consequently, also for the equilibrium modulus of elasticity E®) than the specimens with fine spherulites, but above 92°C, the contrary is observed. Thus, the reduction in a~ (or E®) with an increase in temperature takes place approximately linearly for the coarse spherulitic structures, whereas the curve for the temperature dependence of a~ for fine spherulitic structures has its own course in the various temperature intervals. This curve has two sharp inflections and a horizontal portion with a stable equilibrium stress ~ (or E~) over a comparatively wide temperature region (from 40 to 100°C); this fact should have a certain practical interest in the use of polymers in designs and machine components working over a wide temperature interval under load. Moreover, extrapolation of the temperature relationships obtained for the various spherulitic structures towards higher temperatures shows that they converge towards a single straight line (at which the equilibrium stresses ~ fall to zero) corresponding to a temperature of 160°C, which is the melting point of isotactic polypropylene. The trend mentioned for the temperature dependence of the equilibrium stress a~ (or E~) is evidence of the fact that there exists a certain temperature Tn~ (in our case ~ 92°C) at which all spherulitie structures exhibit the same equilibrium elastic properties. From Fig. 1 it may also be seen that the greatest dependence of a® on average spherulite size is observed at low temperatures (20-40°C) at which the value of a~ (and consequently of E~) increases by a factor of approximately 2 with an increase in average spherulite size from 25 to 475/~. Increase in temperature leads to a gradual fall-off in this relationship, which ends at Tn~----92°, and above this temperature its qualitative characteristics alter; with an increase in spherulite size (within the range investigated by us) the equilibrium stress a® (or E~) falls somewhat. If the monotonic character of the relationship between a~ and temperature may be easily explained for the coarse spherulitic structures, starting from the stability of the structural elements (perfect, definitely shaped spherulites cannot grow further), then the character for the graph of the temperature dependence of a~ for the fine spherulitic structure, having two inflections and a region of stable elastic properties, gives at first glance a basis for supposing that, with an increase in temperature, further growth of the fine spherulites takes place in the stress field. Some investigations of other authors also give evidence of this [16, 17]. Comparative optical investigations of specimens before and after relaxation tests at 92°C indicated that externally (spherulite dimensions, degree of perfection and defectiveness) they hardly differ at all. This indicates that the observed differences in the temperature dependences of the stress or elastic modulus are not connected with any change in the spherulite dimensions during the process of the experiment. Consequently, these should be caused by a change in the fine structure of the sphcrulites themselves, and this presents a very interesting problem for electron microscope investigations.
438
V . I . PAVLOVet
a~.
In view of the large dispersion in the value of the remaining parameters in the Kohlrausch equation, namely, a o (or E0), z, a and k and also 0, the dependence of these on temperature and spherulite size are shown in Table 2. Analysis of the relationships between the kinetic parameters of the Kohlrauseh equation and the temperature and spherulite size (Table 2), and also the optical observations, make it possible to draw the conclusion t h a t the large scatter in their values is connected in the first place with a considerable non-uniformity and defectiveness in the specimens' structure, which, although it was considerably reduced by the use of special measures for preparing the specimens, nevertheless still remained comparatively large; and, in the second place with the impossibility of strictly Observing the ideal conditions for carrying out the stress relaxation experiment *. I n this way, it m a y be seen from what has been put forward above t h a t there exists a temperature (in our case, Tn®:92°C), at which the equilibrium stress is the same for all the spherulite sizes investigated. Similar temperature dependences were also obtained for the equilibrium stresses corresponding to given times of relaxation (0, 5, 30, 60 rain). Consequently, the observed trend in these temperature dependences is evidence of the fact t h a t for a n y given duration of the relaxation process there exists a value of the temperature T~t at which all the spherulite structures exhibit the same elastic properties. With an increase in the relaxation times t, these temperatures T~t fall, tending to a limit (Fig. 2). I t is interesting to note t h a t this relationship is well described by the same Kohlrausch function. Therefore, having formally applied this relationship by use of the method in [15], it was possible to calculate the equilibrium value of the temperature Tn~ which turned out also to be equal to 92°C, t h a t is, it coincides with the value of this quantity found from the temperature dependence of the equilibrium stress for spherulite structures differing in dimensions, which had been discussed previously (Fig. 1). From all t h a t has been said above, it is clear t h a t at the temperature T.: the stresses (and, consequently, the elastic modulus as well) will be the same at any time t for all structures. In particular, this makes it possible to write down by means of the Kohlrausch equation the following equality, which must be obeyed at * Necessary conditions for carrying out the stress relaxation experiment are that the deformation should be applied instantaneously and held constant during the experiment. Whereas the latter condition was strictly cbserved in our case (the dynamometer had a large rigidity), under the real conditions of the experiment the time taken to apply the deformation was always finite. Therefore, during the time when the deformation was applied to the specimen, part of the stress in it was able to relax. In carrying out the investigations at a raised temperature, the relative value of the loss in stress during the time of application of the deformation will be greater at higher temperatures than at lower temperatures. The difficulty in allowing for these losses also leads to a greater or smaller deviation of the values of the kinetic parameters from the actual values, that is, to a large dispersion in the calculated values of the parameters in the Kohlrausch equation obtained by us.
Relaxation properties of crystalline and amorphous polymers
439
this temperature, for the two structures with the extreme, spherulite dimensions E¢¢+Eoe-(#~)k = E~ + E'oe-(tl~')k' where t is the time of stress relaxation, E~, E0, r, and k are the parameters of the relaxation process according to Kohlrausch for the fine spherulite structure which depend on temperature; E ' , E~, z' and k' are the corresponding parameters for the coarse spherulite structure. At the present time, hovewer, there is no possibility of giving this equation in the form of an explicit relationship between t and T,t, since the accurate data required for this about the temperature dependence of the kinetic parameters in the Kohlrausch equation are not available. Clarification of these relationships is a very important task in further investigations, which will make it possible to throw light on new parameters, which will include the dimensions of the supermolecular structures and will quantitatively characterize their effect on the polymer properties. Amorphous polyarylates. To clarify the effect of the type of supermolecular structure on the mechanical propetries of amorphous polymers, stress relaxation under uniaxial compression was investigated in bulk specimens of the globular and fibrllar poylarylate P-1 over the temperature range 20-245°C. Stress relaxation curves were obtained experimentally over these temperatures for both types of supermolecular structure, and from these curves the parameters of the relaxation properties were determined by means of the method referred to in [15]. Almost all the relaxation curves for the globular polyarylate are described well by the Kohlrausch equation. At the same time, the majority of the curves for this same polyarylate, but having a predominantly fibrillar supermolecular structure, do not in general obey this equation, or do not obey it over the whole of their course*. This fact is again evidence that the relaxation properties of amorphous glassy polyary!ates are determined not only by their chemical structure, but also by their physical structure at the supermolecular level. As a result of the experiments carried out and the calculations for both types of polyarylate it was possible to establish the relationship between the relaxed equilibrium stress a~ and temperature (Fig. 3). As m a y be seen, the values of a~ decrease monotonically with an increase in temperature, falling to zero at the corresponding softening points for these types of polymer. Thus, for the globular polyarylate the values of equilibrium stress were greater than those for the fibrillar polyarylate ar temperatures < 140°C, but at temperatures > 140°C the reverse was true, that is, relationship is similar to that discussed previously for crystalline polypropylene. This means that at low temperatures the stress relaxation takes place more rapidly and to a greater extent in the fibrillar polymer, but at high temperatures in the globular polymer. Such a trend in the rates of the relaxation * In connection with this, only the value of the equilibrium stress a~ was calculated for the latter curves.
440
V . I . PArLor et al.
processes is evidently caused by the fact that at low temperatures the fibrillar structure has a greater internal mobility (the polymer is not so hard), whereas at high temperatures the globular structure undergoes a more rapid partial breakdown under stress. This appears especially noticeable at the softening points, at which the breakdown of secondary formations into the elements from which they are made begins. Thus for the globular polyarylate, the structure of which is formed from coiled macromoleeules, this breakdown sets in at lower temperatures (Fig. 3), since the spherical shaped particles and the clusters of these particles ~..,kg/cm 2
800 GO0 ~00 200
o
x K
I
~o
12o
\
2oo
\i
zgo r,°c
FIG. 3. Temperature dependence of the equilibrium stress a~ for (1) globular and (2) fibrillar polyarylates. are connected together comparatively weakly. In the ease of the fibrillar supermolecular structure, formed from elongated bundles in which uncoiled macromolecules are grouped together, this breakdown sets in at higher temperatures since the interaction between the elements of the structure is here strong. In this way, from what has been proposed above the conclusion m a y be drawn that, on going from low to high temperatures the relationship between the relaxation process mechanisms, caused by the difference in supermolecular structures, changes. The presence of a point of intersection of the curves in Fig. 3 is in agreement with this. Similar intersecting relationships were also obtained for nonequilibrium stresses (or elastic moduli), corresponding to given relaxation times (0, 5, 30 and 60 rain). The presence of a point of intersection between the lines for the temperature dependence of the stress (or elastic modulus) for a polyarylate having different types of supermoleeular structure is evidence for the fact that at the temperature corresponding to the point of intersection, a change in the type of supermolecular structure has no effect on the elasticity of the polymer body. The temperature dependences of the kinetic parameters of the Kohlrausch equation and the viscosity parameter ~/are shown in Fig. 4. With an increase in the temperature of the globular polyarylate, the relaxed part of the stress a o and the parameter a increase smoothly, but the parameter k falls linearly in the range from 0.46 to 0.24; ~/ decreases slightly over the range investigated by us (from 5 × 10TMto 5 × 1011poise). For the fibrillar polyarylate, the temperature dependence
Relaxation properties of crystalline and amorphous polymers
441
of these parameters could not succesfully be established because of the large scatter in their values. In this way, the presence of fairly clearly defined temperature relationships for these parameters in the case of globular structures, and their absence in the case of fibrillar structures, makes it possible to conclude that the globular polyarylate is more uniform than the fibrillar polyarylate in its physical structure; this is in good agreement with electron-microscope investigations [13]. g/cmz
n pof,~e
v, m/n
7)xF~
125~ -
~
10 z°~
/1o \ 755
l'O 0"5
5
'
,
I
,
o 5o too ,:o 2oo
05
o o
04'
25~ 0
Jo
'
250 0 50 I00 ISOT,~C0 50 100 I50 200T,~ O 50 ZOO I50 200 2~TW
FIG. 4. Temperature dependence of the kinetic parameters in the Kohlrausch equation. a0, relaxed part of the stress; a and k, parameters; T, relaxation time; t/, viscosity. The investigation carried out b y us on the quantitative level indicates that the relaxation properties of polymers existing in the amorphous state (and not only in the crystalline state) depend on their supermolecular structure as well as on their chemical structure. From the practical point of view, the results obtained indicate that, in the use of polyarylate P-1 in rigid constructions under load*, at low temperatures it is more suitable to use a polyarylate with a globular supermolecular structure, and at high temperatures a polyarylate with a fibrillar supermolecular structure. In this way, the present work indicates that the study of relaxation processes uncovers wide possibilities both for the quantitative investigation of the connection between mechanical properties and the supermolecular structure of polymer bodies, and also for the correct and thorough utilization of polymers having a certain chemical structure. CONCLUSIONS
(1) For the particular case of monolithic crystalline isotactio polypropylene and the amorphous glassy polyarylate prepared from isophthalic acid and phenolphthalein, a quantitative investigation has been made of the effect of the characteristics of the supermolecular structure on the parameters of the relaxation properties over a wide temperature interval. * Static loading is envisaged here, because under dynamic conditions the globular polyarylate is less suitable for use because of its high brittleness.
442
K. KH. RAZIKOV et al.
(2) It has been quantitatively demonstrated that the relaxation properties of polymers existing both in the crystalline and also in the glassy state depend on the type and dimensions of the elements of the supermolecular structure as well as on their chemical structure. (3) I t has been established that for any particular duration of the relaxation process in the crystalline and amorphous polymers investigated, there exist temperatures at which the elastic properties do not depend on the supermolecular structure of the polymer body. Translated by G. F. ~V[ODLEN REFERENCES 1. 2. 3. 4. 5.
F. J. PADI)EN and H. D. K E I T H , J. App]. Phys. 16: 1479, 1959 T. I. SOGOLOVA, Dissertation, ]963 G. P. ANDRIANOVA, Dissertation, 1963 L. I. NAD_~LI~EISHVILI, Dissertation, 1964 V. A. KARGIN, N. F. BAKEYEV, LI LI-SHEN and T. S. OCH_APOVSKAYA, Vysokomol. soyed. 2: 1280, 1960 (Translated in Polymer Sei. U.S.S.R. 3: 2, 291, 1962) 6. B. G. RANBY, F. F. MOREHEAD and N. W. WALTER, J. Polymer Sci. 44: 349, 1960
CHANGES IN THE SUPERMOLECULAR STRUCTURE OF CELLULOSE AFTER TREATMENT WITH CERTAIN ACTIVATING REAGENTS*t K. K~. RAzmov, E. D. TYAGAI, 13.P. LARnV and K~. U. USMAXOV Institute of Chemistry and Technology of Cotton Cellulose (Received 2 July 1966)
Du~ to its peculiar supermolecular structure, natural cellulose is known to be an inactive polymer. To produce its wide variety of derivatives, the cellulose must therefore be activated. This usually consists in loosening up its microstrueture by some treatment or other. One way of increasing the chemical activity of cellulose preparations is t h a t of inclusion, which consists in swelling the cellulose and fixing this state by treatment in certain organic materials [1]. Different kinds of amines are often used for activation [2-5]. Swelling in a mixture of glycerine and water is also known for cellulose it causes the microstructure to loosen Ul5, and therefore increases the reactivity of cellulose. * Vysokomol. soyed. A9. No. 2, 393-397, 1967. t 2nd Report of the series "Influence of different treatments on the mJerostrueture of cellulose fibres".