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Synthesis and properties of graft copolymers of cotton cellulose with fluoroethylenes in presence of Ce4+
Graft copolymers of cotton cellulose with fluoroethyleaes
2275
REFERENCES 1. A. A. KONKIN, Uglerodnye i drugiye zharostoikiye voloknistye materialy (Carbon and Other Heatproof Fibrous Materials) p. 286, Khimiya, Moscow, 1974 2. N. JUDD, Brit. Polymer J. 9: 272, 1977 3. O. P. BAHL and L. M. MANOCHA, Angew. Makromolek. Chemie 75: 137, 1979 4. Declaration Japan 58-115123, Pub. in RZhKhim 14T3040P, 1984 5. Declaration Japan 56-128362, Pub. in RZhKhim 3T209P, 1983 6. S. BRELANT, Carbon 19: 142, 1981 7. L. T. DROAL, M. J. RICH and P. F. IBOYD, J. Amer. Chem. Soc. 22: 199, 1981 8. R. V. SUBRAMANIAN, Pure Appl. Chem. 52: 1929, 1980 9. Tekhnika elektronnoi spektroskopii (Technique of Electron Spectroscopy) (Ed. D. Ke) p. 142, Mir, Moscow, 1965 10. A. Ye. FAINERMAN, Novye metody issledovaniya polimerov (New Methods of Investigating Polymers) p. 17, Naukova dumka, Kiev, 1975 11. T. E. LIPATOVA, V. A. BUDNIKOVA and Yu. S. LIPATOV, Vysokomol. soyed. 4: 1398, 1962 (Not.translated in Polymer Sci. U.S.S.R.) 12. J. SHULTZ, C. CAZENEUVE, M. E. R. SHANADON and J. B. J. DONNET, J. Adhesion 12: 221, 1981
Polymer ScienceU.S.S.R. Vol.28, No. 10, pp. 2275-2282, 1986
Printed in Poland
0032-3950]86 $10.00+.00 © 1987 Pergamon Journals Ltd.
S Y N T H E S I S A N D P R O P E R T I E S OF GRAFT C O P O L Y M E R S OF C O T T O N C E L L U L O S E WITH F L U O R O E T H Y L E N E S I N P R E S E N C E OF Ce 4 ÷* S. N. USMANOV, E. D. TYAGAI, A. VALIYEV a n d M. K. ASAMOV Lenin State University, Tashkent
(Received 10 February 1985) Chemical graft polymerization of some fluoromonomers on cotton cellulose has been investigated in presence of a redox system containing tetravalent cerium. Physical chemical methods have been used to study the structural features of graft copolymers of cotton cellulose with fluorine-containingpolymers. It is assumed that the grafting process of the fluoromonomers occurs, in the main, in the amorphous regions of cellulose. A GREATdeal o f work has been done o n the synthesis a n d properties o f graft c o p o l y m e r s of cellulose with vinyl m o n o m e r s using redox systems [1-8] whereas modification o f the * Vysokomol. soyed. A28: No. 10, 2050--2055, 1986.
2276
S.N. USMANOVet al.
p r o p e r t i e s o f cellulose a n d its derivatives b y f l u o r i n e - c o n t a i n i n g p o l y m e r s using Ce 4+ as o x i d a n t has been v e r y little e x p l o r e d . T h e p r e s e n t p a p e r outlines the results o f investigations o f the r e a c t i o n o f graft p o l y m e r i z a t i o n o f vinyl fluoride (VF), vinylidene fluoride ( V D F ) a n d t e t r a f l u o r o e t h y l e n e ( T F E ) w i t h c o t t o n cellulose in p r e s e n c e o f Ce*~- a n d i n f o r m a t i o n o n some p h y s i c a l c h e m i c a l p r o p e r t i e s o f the graft c o p o l y m e r s o b t a i n e d . Before modification Ekspress-1 cotton fibre was first cleared of the attendant substances by boiling in 2% NaOH solution for 2 hr followed by extraction with ethyl alcohol for 14 hr in a Soxhlet apparatus; cotton fabric (C-tissue) was extracted with ether for 12 hr. As initiator we used an aqueous solution of cerium ammonium nitrate (Ce(NH4)2(NOa)6) of chemically pure grade with a concentration of 5 x 10-3 mole/l. An acid medium was produced by adding nitric acid in a concentration 1.5 mole/l. VF was synthesized by catalytic hydrofluorination of acetylene [9] and cleared of difluoroethane by distillation in a rectifying column. VDF was obtained by pyrolytic dehydrochlorination of 1-chloro-2,2-difluoroethane (Freon-142) by the technique in [10]. TFE was synthesized by debromination of 1,2-dibromotetrafluoroethane (Freon-114-B2) under the influence of zinc dust in boiling isopropyl alcohol [11]. The purity of all the monomers was evaluated with the Vyrukhrom A-1 chromatograph. Their impurity content did not exceed 10 -* wt. %. To carry out graft polymerization 0.5 g cotton fibre or C-issue were kept in an aqueous solution of cerium ammonium nitrate for 0.5 hr at 0°C, squeezed out and placed in a one-chamber ampoule. Then 1 ml nitric acid and 2-3 ml of 80 ~ aqueous solution of acetone added and the monomer dosed (weight ratio of cellulose : monomer= 1 : 3). The ampoule was degassed by repeated freezing and thawing at 0.133 Pa, sealed and the reaction run at 25+2°C. The content of graft polymer was determined by analysis for fluorine by the Shoeniger method [12]. The sorption properties were studied with a vacuum-sorption apparatus on McBain balances [13] at a residual pressure 0.133 Pa at 25°C. The density of the graft copolymers was measured by hydrostatic weighing [14] at 25°C. The X-ray investigations were undertaken with the DRON-2.0 diffractometer using monochromatized CuK~ radiation at a voltage 35 kV, strength of current 30 A by the scheme for reflexion with rotation of the sample in the plane of the goniometer; the sample was in the holder in the form of a pellet consisting of comminuted fibre. The degree of crystallinity of the samples was determined by the Segal method [15]. Chemical stability was evaluated from the weight loss on keeping the fibres in different acids for 24 hr [16] and by determining their dissolution times. G r a f t p o l y m e r i z a t i o n o f f l u o r o m o n o m e r s on cellulose in a b s e n c e o f a n y s o l v e n t leads to the f o r m a t i o n o f graft c o p o l y m e r s with a low c o n t e n t o f the g r a f t e d c o m p o n e n t . T h e use as swelling a g e n t o f an a q u e o u s s o l u t i o n o f a c e t o n e g r e a t l y raises the degree o f grafting. T h e r e a s o n is a p p a r e n t l y t h a t in p r e s e n c e o f w a t e r t h e r e is l o o s e n i n g o f the m i c r o p o r e s o f the cellulose m a t e r i a l s a n d a c e t o n e acts as a solvent o f the f l u o r o m o n o mers facilitating their p e n e t r a t i o n a n d t h a t o f Ce 4+ into the less accessible regions o f cellulose. S t u d y o f the effect o f the a c e t o n e c o n c e n t r a t i o n in its a q u e o u s s o l u t i o n on the yield o f g r a f t c o p o l y m e r s h o w e d (Fig. l a ) t h a t with i n c r e a s e in the c o n t e n t o f a c e t o n e to 80~o the a m o u n t o f g r a f t e d P V F , P V D F a n d P T F E rises b u t t h e n t o g e t h e r with the
Graft copolymers of cotton cellulose with fluoroethylenes
2277
graft copolymers homopolymers of these monomers form. Therefore, all the experiments were conducted in a mixture containing 80 % acetone and 20 % water. The data on the kinetics of graft polymerization of VF, VDF and T F E on cotton cellulose showed (Fig. lb) that in the initial stage the yield of the graft polymers rises to then remain constant. This is apparently due to fall in the concentration of the Ce 4+ ions and, accordingly, fall in the number of macroradicals formed in the reaction medium. As the Figure shows, the yield of graft polymers for the fluoromonomers used differs ( T F E - V D F - V F ) . Evidently, this is explained by their different chemical activities and the specifics of sorption of these monomers by cotton cellulose.
aw~ %
b 0
0
,,,O
q O
I
qO
t
0
I o
1
80 OAc,Wt%
aw,%
3
,0
q
C
Time, hi,
3
I
I
2
q
%e4 ~I0 2, mole/L FIG. 1. Yield of graft cotton fibre copolymers with PVF (1), PVDF (2) and PTFE (3) at 25°C as a function of the concentration of acetone in water (a), the reaction time (b) and the concentration of Ce4+ (c). a-Ce*+ =2.0x 10-2 mole/l., 3 hr;b-ccc,+ =2.0x 10-2 mole/l., cA0--80 °~,• C--CA°=80%, 4 hr. The degree of grafting is also influenced by the concentration of Ce 4+. As may be seen f r o m Fig. lc, change in the oxidant concentration within the limits 2.0 x 10 - 2 3.0 x 10 -2 mole/1, for a reaction time of 4 hr at 25°C raises the yield o f the graft copolymer; with further increase in the Ce 4+ concentration this yield remains constant with simultaneous initiation of the formation of the homopolymer. Apparently, this may be explained by the fact that with rise in the concentration of the oxidant in solution the number of active centres increases, which raises the rate of termination as a result of the interaction of the macroradicals with Ce 4 ÷ and also accelerates chain transfer to the monomer leading to the formation o f the homopolymer.
2278
S . N . USMANOV et al.
It might have been assumed [17] that the fluorine-containing polymers would raise the hydrophobicity and chemical stability of cellulose when grafted. In fact, with increase in the content of the grafted polymers in the copolymers their sorption capacity diminished (Fig. 2) most obvious in the case of the graft copolymer with PTFE (Fig. 2c). These changes are apparently linked with the formation of grafted chains in the cellulose macromolecule and with fall in the number of cellulose pores accessible for the action of water vapour and also with the appearance of hydrophobicity in the samples. The formation of graft copolymers was earlier confirmed by IR spectroscopy and electron microscopy [18]. The structural changes in the graft copolymers were characterized from their specific volumes [1]. Comparison of the experimental and calculated values of the specific volumes showed (Fig. 3) that the true values for graft copolymers are greater than those calculated by the additivity principle. This points to the loosening of the structure of cotton cellulose as a !
b N :Z:: 4-.
"~4
•
0
I
l
l
l
80
40
40
80
Pl/P0 8
C
I 2
4,.
3
g
4
0
I
I
I
4O
I
8O
Fit. 2. Sorption isotherms of the water vapours of graft cotton fibre copolymers with PVF (a), PVDF (b) and PTFE (c) at 25°C (/-initial fibre), a: 2,3-graft copolymerscontaining 1"5 and 3.3 % PVF; b: 2,3- graft eopolymerscontaining8.7 and 1 I. 1% P V D F ; c: 2 - 4 - graft copolymerscontaining 3.3, 6.1 and 16"4~o PTFE.
2280
S . N . USMANOVet al.
no change. C o n s e q u e n t l y in this case, too, the p r o c e s s o f g r a f t i n g d o e s n o t affect t h e crystalline regions. The P T F E reflexions are m o r e intense t h a n those o f P V D F . This e x p l a i n s the d e t e c t i o n o f the P T F E reflexions a l r e a d y for a 6.1 wt. ~ gain. ~ It m a y be c o n c l u d e d f r o m the s t r u c t u r a l investigations t h a t the p r o c e s s o f g r a f t i n g f l u o r o m o n o m e r s on c o t t o n cellulose d o e s n o t affect its crystalline regions and, therefore, does not lead t o c h a n g e in the d . c , The grafting p r o c e s s evidently occurs in the uno r d e r e d regions o f the c~llulose structure ( b o t h b~tween a n d within the microfibrils).
/ / / /
I
22.4
I •
I
17
I
I, I
22.4 17.5
20.7 17ff
20 °
FIG. 4. Radiographs of initial CC (1), graft copolymers of cotton fibre (2-5) and initial PVDF (6) and PTFE (7). Content of grafted PVDF (2) and PTFE (3-5), wt. %; 2 - 7.6; 3 - 2"1; 4 - 6 . I; 5-20-6.
EFFECT OF THE CONTENT OF GRAFT POLYMER ON THE CHEMICAL STABILITY OF GRAFT COTTON CELLULOSE COPOLYMERS IN ACIDS
Graft copolymers Initial
cotton
cellulose
(CC)
Contont of grafted polymer, % m
Dissolution time in H2SO,, in min 7
Weight loss on treatment with acids, 70 HNOa
HCI
CHaCOOH
77"4 59"3 53"6 51"0
6-7 5.7 7"3 5"1
1'1 1'3 1'5
10 11
34"0 26"1 22.5 21-7
CC-PVDF
4'7 7'2 8"7
20 22 25
12.7 9"0 7.2
42 "4 37"6 36'3
4.0 2.0 1-I
CC-PTFE
6"1 7"0 10:7
26 29 31
7'6 4.9 3"7
25"0 15"9 12. !
2"0 0.7 0"4
CC-PVF
8
Graft copolymers of cotton cellulose with fluoroethylenes
2281
Study of the stability of graft cotton cellulose copolymers to the action of organic and mineral acids established (Table) that concentrated sulphuric acid causes rapid dissolution of the initial cotton fibre during 7 min while the graft copolymers containing 1-5 % PVF, 8.7% PVDF and 10.7% PTFE dissolve in 11, 26 and 31 min respectively. The weight loss of the graft copotymers on treatment with concentrated nitric, hydrochloric and acetic acids with increase in the content of the grafted fluoropolym~r decreases pointing to increase in their chemical stability (Table). This eff.~ct is dug to the screening o f the cellulose macromolecules by the g;af~ed chains of the fluoropolymers characterized by high stability to the action of acids. Thus, chemical graft polymerization of some fluoromonomers on cotton cellulose has been investigated and the structural features ofth~ graft copolymers obtained studied. It is assumed that the process of grafting of fluoropolymers essentially takes place in the amorphous regions of cellulose. The grafted polymers filling the most accessible regions o f the cellulose structure promote increase in its hydrophobicity and chemostability. Translated by A. CRozY
REFERENCES
1. B.A. DOLGOPLOSK and Ye. I. TINYAKOVA,Okislitel'no-vosstanovitel'nye sistemy kak istochniki svobodnykh radikalov (Redox Systems as Free Radical Sources) p. 134, Nauka, Moscow, 1972 2. V. I. KURLYANKINA, A. K. KHRIPUNOV, V. A. MOLOTKOV and O. P. KOZ'MINA, Vysokomol. soyed. B10: 179, 1968 (Not translated in Polymer Sci. U.S.S.R.) 3. F. K. GUTHRIE, Khimiya i tekhnologiya polimerov, 5, 94, 1965 4. R. M. LIVSHITS, V. P. ALACHEV, M. V. PROKOF'EVA and Z. A. ROGOVIN, Vysokomol. soyed. 6: 655, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 4, 723, 1964) 5. M. S. BAINS, J. Polymer Sci. C37: 125, 1972 6. R. M. LIVSHITS and Z. A. ROGOVIN, Progress polimernoi khimii (Progress in Polymer Chemistry) p. 158, Nauka, Moscow, 1969 7. Z. A. ROGOVIN, Khimiya tsellyulozy (The Chemistry of Cellulose) p. 485, Nauka, Moscow, 1972 8. R. M. LIVSHITS and Z. A. ROGOVIN, Usp. khim. 34: 1100, 1965 9. Kh. U. USMANOV, A. A. YUL'CHIBAYEV, R. MUKHAMEDZHANOV, A. VALIYEV, A. A. GORDIYENKO, A. A. PATENKO and G. S. DORDZHIN, Vysokomol. soyed. 5: 1277, 1963 (Translated in Polymer Sci. U.S.S.R. 5: No. 2, 1964) 10. R. YUSUPALIYEV, Dissert. Cand. Chem. Sci., 182 pp., Tashkent State Univ., Tashkent, 1975 11. I. Yu. YAKUBOV, Author's Abstr. Dissert. Cand. Chem. Sci., 26 pp., Tashkent State Univ., Tashkent, 1980 12. T. N. KASTERINA and L. S. KALININA, Khimicheskiye metody issledovaniya sinteticheskikh stool i plasticheskikh mass (Chemical Methods of Investigating Synthetic Resins and Plastics) p. 55, Goskhimizdat, Moscow, 1963 13. S. A. TASHMUKHAMEDDV, Author's Abstr. Dissert. Cand. Chem. Sci., 18 pp., Tashkent State Univ., Tashkent, 1966 14. A. WEISBERGER, Fizicheskiye metody organicheskoi khimii (Physical Methods in Organic Chemistry) Vol. 1, p. 99, Inost. Lit., Moscow, 1950 15. M. A. MARTYNOV and K. A. VYLEGZHANINA, Rentgenografiya polimerov (X-ray Study o f Polymers)p. 15, Khimiya, Moscow, 1972
2282
Yu. K. GODOVSKIIand I. A. VOLEGOVA
16. A. P. GRIGOR'EV, Laboratornyi praktikum 13o tekhnologii plasticheskikh mass (Laboratory Practicum on Plastics Technology) Vol. 2, p. 227, Vyssh. shk., Moscow, 1977 17. Yu. A. PANSHIN, S. G. MAL'KEVICH and 'Is. S. DUNAYEVSKAYA, Ftoroplasty (Fluoroplasts) p. 100, Khimiya, Leningrad, 1978 18. S. G. YUL'CHIBAYEVA, A. MURATOV, A. A. YUL'CHIBAYEV and S. N. USMANOV, Vysokomol. soyed. A24: 722, 1982 (Translated in Polymer Sci. U.S.S.R. 24: 4, 800, 1982)
Polymer Science U.S.S.R. Vol. 28, No. 10, pp. 2282-2289, 1986 Printed in Poland
0032-3950]86 $10.00 + . 0 ~ © 1987 Pergamon Journals Ltd.
CRYSTALLIZATION AND MELTING OF POLYETHYLENE OXIDE IN A SYSTEM WITH A JOINTLY CURED DENSELY CROSSLINKED POLYMER* Yu. K. GODOVSKIIand I. A. VOLEGOVA Karpov Physicochemical Research Institute (Received 11 February 1985)
The calorimetric method has been employed to study the patterns of crystallization and melting of polyethylene oxide in a system with a melamine formaldehyde polymer cured jointly with it. The topology of the spatial densely crosslinked polymer network and chemical binding of the terminal groups of polyethylene oxide were found to have a strong influence on its behaviour on crystallization and melting. STUDY o f phase separations in polymer-polymer systems with one crystallizable c o m ponent is usually made in systems where the second amorphous component is also linear [1, 2]. However, it is of interest to investigate the behaviour of the crystallizable component in systems with a densely crosslinked polymer. The high density o f the threedimensional polymer network of the second component may lead to profound changes in the behaviour of the crystallizable component in such systems as compared with the homopolymer. Therefore the aim of this work is to study the features of the crystallization and melting of polyethylene oxide (PEO) in a polymer system with a melamine formaldehyde (MF) polymer jointly cured with it and which is the product o f polycondensation o f melamine derivatives and characterized by high density of the spatial network [3]. To obtain the MF-PEO systems investigated we used the hexamethyl ether of hexamethylot melamine (HM-3) of the following structure * Vysokomol. soyed. A28: No. 10, 2056-2062, 1986.
2275
REFERENCES 1. A. A. KONKIN, Uglerodnye i drugiye zharostoikiye voloknistye materialy (Carbon and Other Heatproof Fibrous Materials) p. 286, Khimiya, Moscow, 1974 2. N. JUDD, Brit. Polymer J. 9: 272, 1977 3. O. P. BAHL and L. M. MANOCHA, Angew. Makromolek. Chemie 75: 137, 1979 4. Declaration Japan 58-115123, Pub. in RZhKhim 14T3040P, 1984 5. Declaration Japan 56-128362, Pub. in RZhKhim 3T209P, 1983 6. S. BRELANT, Carbon 19: 142, 1981 7. L. T. DROAL, M. J. RICH and P. F. IBOYD, J. Amer. Chem. Soc. 22: 199, 1981 8. R. V. SUBRAMANIAN, Pure Appl. Chem. 52: 1929, 1980 9. Tekhnika elektronnoi spektroskopii (Technique of Electron Spectroscopy) (Ed. D. Ke) p. 142, Mir, Moscow, 1965 10. A. Ye. FAINERMAN, Novye metody issledovaniya polimerov (New Methods of Investigating Polymers) p. 17, Naukova dumka, Kiev, 1975 11. T. E. LIPATOVA, V. A. BUDNIKOVA and Yu. S. LIPATOV, Vysokomol. soyed. 4: 1398, 1962 (Not.translated in Polymer Sci. U.S.S.R.) 12. J. SHULTZ, C. CAZENEUVE, M. E. R. SHANADON and J. B. J. DONNET, J. Adhesion 12: 221, 1981
Polymer ScienceU.S.S.R. Vol.28, No. 10, pp. 2275-2282, 1986
Printed in Poland
0032-3950]86 $10.00+.00 © 1987 Pergamon Journals Ltd.
S Y N T H E S I S A N D P R O P E R T I E S OF GRAFT C O P O L Y M E R S OF C O T T O N C E L L U L O S E WITH F L U O R O E T H Y L E N E S I N P R E S E N C E OF Ce 4 ÷* S. N. USMANOV, E. D. TYAGAI, A. VALIYEV a n d M. K. ASAMOV Lenin State University, Tashkent
(Received 10 February 1985) Chemical graft polymerization of some fluoromonomers on cotton cellulose has been investigated in presence of a redox system containing tetravalent cerium. Physical chemical methods have been used to study the structural features of graft copolymers of cotton cellulose with fluorine-containingpolymers. It is assumed that the grafting process of the fluoromonomers occurs, in the main, in the amorphous regions of cellulose. A GREATdeal o f work has been done o n the synthesis a n d properties o f graft c o p o l y m e r s of cellulose with vinyl m o n o m e r s using redox systems [1-8] whereas modification o f the * Vysokomol. soyed. A28: No. 10, 2050--2055, 1986.
2276
S.N. USMANOVet al.
p r o p e r t i e s o f cellulose a n d its derivatives b y f l u o r i n e - c o n t a i n i n g p o l y m e r s using Ce 4+ as o x i d a n t has been v e r y little e x p l o r e d . T h e p r e s e n t p a p e r outlines the results o f investigations o f the r e a c t i o n o f graft p o l y m e r i z a t i o n o f vinyl fluoride (VF), vinylidene fluoride ( V D F ) a n d t e t r a f l u o r o e t h y l e n e ( T F E ) w i t h c o t t o n cellulose in p r e s e n c e o f Ce*~- a n d i n f o r m a t i o n o n some p h y s i c a l c h e m i c a l p r o p e r t i e s o f the graft c o p o l y m e r s o b t a i n e d . Before modification Ekspress-1 cotton fibre was first cleared of the attendant substances by boiling in 2% NaOH solution for 2 hr followed by extraction with ethyl alcohol for 14 hr in a Soxhlet apparatus; cotton fabric (C-tissue) was extracted with ether for 12 hr. As initiator we used an aqueous solution of cerium ammonium nitrate (Ce(NH4)2(NOa)6) of chemically pure grade with a concentration of 5 x 10-3 mole/l. An acid medium was produced by adding nitric acid in a concentration 1.5 mole/l. VF was synthesized by catalytic hydrofluorination of acetylene [9] and cleared of difluoroethane by distillation in a rectifying column. VDF was obtained by pyrolytic dehydrochlorination of 1-chloro-2,2-difluoroethane (Freon-142) by the technique in [10]. TFE was synthesized by debromination of 1,2-dibromotetrafluoroethane (Freon-114-B2) under the influence of zinc dust in boiling isopropyl alcohol [11]. The purity of all the monomers was evaluated with the Vyrukhrom A-1 chromatograph. Their impurity content did not exceed 10 -* wt. %. To carry out graft polymerization 0.5 g cotton fibre or C-issue were kept in an aqueous solution of cerium ammonium nitrate for 0.5 hr at 0°C, squeezed out and placed in a one-chamber ampoule. Then 1 ml nitric acid and 2-3 ml of 80 ~ aqueous solution of acetone added and the monomer dosed (weight ratio of cellulose : monomer= 1 : 3). The ampoule was degassed by repeated freezing and thawing at 0.133 Pa, sealed and the reaction run at 25+2°C. The content of graft polymer was determined by analysis for fluorine by the Shoeniger method [12]. The sorption properties were studied with a vacuum-sorption apparatus on McBain balances [13] at a residual pressure 0.133 Pa at 25°C. The density of the graft copolymers was measured by hydrostatic weighing [14] at 25°C. The X-ray investigations were undertaken with the DRON-2.0 diffractometer using monochromatized CuK~ radiation at a voltage 35 kV, strength of current 30 A by the scheme for reflexion with rotation of the sample in the plane of the goniometer; the sample was in the holder in the form of a pellet consisting of comminuted fibre. The degree of crystallinity of the samples was determined by the Segal method [15]. Chemical stability was evaluated from the weight loss on keeping the fibres in different acids for 24 hr [16] and by determining their dissolution times. G r a f t p o l y m e r i z a t i o n o f f l u o r o m o n o m e r s on cellulose in a b s e n c e o f a n y s o l v e n t leads to the f o r m a t i o n o f graft c o p o l y m e r s with a low c o n t e n t o f the g r a f t e d c o m p o n e n t . T h e use as swelling a g e n t o f an a q u e o u s s o l u t i o n o f a c e t o n e g r e a t l y raises the degree o f grafting. T h e r e a s o n is a p p a r e n t l y t h a t in p r e s e n c e o f w a t e r t h e r e is l o o s e n i n g o f the m i c r o p o r e s o f the cellulose m a t e r i a l s a n d a c e t o n e acts as a solvent o f the f l u o r o m o n o mers facilitating their p e n e t r a t i o n a n d t h a t o f Ce 4+ into the less accessible regions o f cellulose. S t u d y o f the effect o f the a c e t o n e c o n c e n t r a t i o n in its a q u e o u s s o l u t i o n on the yield o f g r a f t c o p o l y m e r s h o w e d (Fig. l a ) t h a t with i n c r e a s e in the c o n t e n t o f a c e t o n e to 80~o the a m o u n t o f g r a f t e d P V F , P V D F a n d P T F E rises b u t t h e n t o g e t h e r with the
Graft copolymers of cotton cellulose with fluoroethylenes
2277
graft copolymers homopolymers of these monomers form. Therefore, all the experiments were conducted in a mixture containing 80 % acetone and 20 % water. The data on the kinetics of graft polymerization of VF, VDF and T F E on cotton cellulose showed (Fig. lb) that in the initial stage the yield of the graft polymers rises to then remain constant. This is apparently due to fall in the concentration of the Ce 4+ ions and, accordingly, fall in the number of macroradicals formed in the reaction medium. As the Figure shows, the yield of graft polymers for the fluoromonomers used differs ( T F E - V D F - V F ) . Evidently, this is explained by their different chemical activities and the specifics of sorption of these monomers by cotton cellulose.
aw~ %
b 0
0
,,,O
q O
I
qO
t
0
I o
1
80 OAc,Wt%
aw,%
3
,0
q
C
Time, hi,
3
I
I
2
q
%e4 ~I0 2, mole/L FIG. 1. Yield of graft cotton fibre copolymers with PVF (1), PVDF (2) and PTFE (3) at 25°C as a function of the concentration of acetone in water (a), the reaction time (b) and the concentration of Ce4+ (c). a-Ce*+ =2.0x 10-2 mole/l., 3 hr;b-ccc,+ =2.0x 10-2 mole/l., cA0--80 °~,• C--CA°=80%, 4 hr. The degree of grafting is also influenced by the concentration of Ce 4+. As may be seen f r o m Fig. lc, change in the oxidant concentration within the limits 2.0 x 10 - 2 3.0 x 10 -2 mole/1, for a reaction time of 4 hr at 25°C raises the yield o f the graft copolymer; with further increase in the Ce 4+ concentration this yield remains constant with simultaneous initiation of the formation of the homopolymer. Apparently, this may be explained by the fact that with rise in the concentration of the oxidant in solution the number of active centres increases, which raises the rate of termination as a result of the interaction of the macroradicals with Ce 4 ÷ and also accelerates chain transfer to the monomer leading to the formation o f the homopolymer.
2278
S . N . USMANOV et al.
It might have been assumed [17] that the fluorine-containing polymers would raise the hydrophobicity and chemical stability of cellulose when grafted. In fact, with increase in the content of the grafted polymers in the copolymers their sorption capacity diminished (Fig. 2) most obvious in the case of the graft copolymer with PTFE (Fig. 2c). These changes are apparently linked with the formation of grafted chains in the cellulose macromolecule and with fall in the number of cellulose pores accessible for the action of water vapour and also with the appearance of hydrophobicity in the samples. The formation of graft copolymers was earlier confirmed by IR spectroscopy and electron microscopy [18]. The structural changes in the graft copolymers were characterized from their specific volumes [1]. Comparison of the experimental and calculated values of the specific volumes showed (Fig. 3) that the true values for graft copolymers are greater than those calculated by the additivity principle. This points to the loosening of the structure of cotton cellulose as a !
b N :Z:: 4-.
"~4
•
0
I
l
l
l
80
40
40
80
Pl/P0 8
C
I 2
4,.
3
g
4
0
I
I
I
4O
I
8O
Fit. 2. Sorption isotherms of the water vapours of graft cotton fibre copolymers with PVF (a), PVDF (b) and PTFE (c) at 25°C (/-initial fibre), a: 2,3-graft copolymerscontaining 1"5 and 3.3 % PVF; b: 2,3- graft eopolymerscontaining8.7 and 1 I. 1% P V D F ; c: 2 - 4 - graft copolymerscontaining 3.3, 6.1 and 16"4~o PTFE.
2280
S . N . USMANOVet al.
no change. C o n s e q u e n t l y in this case, too, the p r o c e s s o f g r a f t i n g d o e s n o t affect t h e crystalline regions. The P T F E reflexions are m o r e intense t h a n those o f P V D F . This e x p l a i n s the d e t e c t i o n o f the P T F E reflexions a l r e a d y for a 6.1 wt. ~ gain. ~ It m a y be c o n c l u d e d f r o m the s t r u c t u r a l investigations t h a t the p r o c e s s o f g r a f t i n g f l u o r o m o n o m e r s on c o t t o n cellulose d o e s n o t affect its crystalline regions and, therefore, does not lead t o c h a n g e in the d . c , The grafting p r o c e s s evidently occurs in the uno r d e r e d regions o f the c~llulose structure ( b o t h b~tween a n d within the microfibrils).
/ / / /
I
22.4
I •
I
17
I
I, I
22.4 17.5
20.7 17ff
20 °
FIG. 4. Radiographs of initial CC (1), graft copolymers of cotton fibre (2-5) and initial PVDF (6) and PTFE (7). Content of grafted PVDF (2) and PTFE (3-5), wt. %; 2 - 7.6; 3 - 2"1; 4 - 6 . I; 5-20-6.
EFFECT OF THE CONTENT OF GRAFT POLYMER ON THE CHEMICAL STABILITY OF GRAFT COTTON CELLULOSE COPOLYMERS IN ACIDS
Graft copolymers Initial
cotton
cellulose
(CC)
Contont of grafted polymer, % m
Dissolution time in H2SO,, in min 7
Weight loss on treatment with acids, 70 HNOa
HCI
CHaCOOH
77"4 59"3 53"6 51"0
6-7 5.7 7"3 5"1
1'1 1'3 1'5
10 11
34"0 26"1 22.5 21-7
CC-PVDF
4'7 7'2 8"7
20 22 25
12.7 9"0 7.2
42 "4 37"6 36'3
4.0 2.0 1-I
CC-PTFE
6"1 7"0 10:7
26 29 31
7'6 4.9 3"7
25"0 15"9 12. !
2"0 0.7 0"4
CC-PVF
8
Graft copolymers of cotton cellulose with fluoroethylenes
2281
Study of the stability of graft cotton cellulose copolymers to the action of organic and mineral acids established (Table) that concentrated sulphuric acid causes rapid dissolution of the initial cotton fibre during 7 min while the graft copolymers containing 1-5 % PVF, 8.7% PVDF and 10.7% PTFE dissolve in 11, 26 and 31 min respectively. The weight loss of the graft copotymers on treatment with concentrated nitric, hydrochloric and acetic acids with increase in the content of the grafted fluoropolym~r decreases pointing to increase in their chemical stability (Table). This eff.~ct is dug to the screening o f the cellulose macromolecules by the g;af~ed chains of the fluoropolymers characterized by high stability to the action of acids. Thus, chemical graft polymerization of some fluoromonomers on cotton cellulose has been investigated and the structural features ofth~ graft copolymers obtained studied. It is assumed that the process of grafting of fluoropolymers essentially takes place in the amorphous regions of cellulose. The grafted polymers filling the most accessible regions o f the cellulose structure promote increase in its hydrophobicity and chemostability. Translated by A. CRozY
REFERENCES
1. B.A. DOLGOPLOSK and Ye. I. TINYAKOVA,Okislitel'no-vosstanovitel'nye sistemy kak istochniki svobodnykh radikalov (Redox Systems as Free Radical Sources) p. 134, Nauka, Moscow, 1972 2. V. I. KURLYANKINA, A. K. KHRIPUNOV, V. A. MOLOTKOV and O. P. KOZ'MINA, Vysokomol. soyed. B10: 179, 1968 (Not translated in Polymer Sci. U.S.S.R.) 3. F. K. GUTHRIE, Khimiya i tekhnologiya polimerov, 5, 94, 1965 4. R. M. LIVSHITS, V. P. ALACHEV, M. V. PROKOF'EVA and Z. A. ROGOVIN, Vysokomol. soyed. 6: 655, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 4, 723, 1964) 5. M. S. BAINS, J. Polymer Sci. C37: 125, 1972 6. R. M. LIVSHITS and Z. A. ROGOVIN, Progress polimernoi khimii (Progress in Polymer Chemistry) p. 158, Nauka, Moscow, 1969 7. Z. A. ROGOVIN, Khimiya tsellyulozy (The Chemistry of Cellulose) p. 485, Nauka, Moscow, 1972 8. R. M. LIVSHITS and Z. A. ROGOVIN, Usp. khim. 34: 1100, 1965 9. Kh. U. USMANOV, A. A. YUL'CHIBAYEV, R. MUKHAMEDZHANOV, A. VALIYEV, A. A. GORDIYENKO, A. A. PATENKO and G. S. DORDZHIN, Vysokomol. soyed. 5: 1277, 1963 (Translated in Polymer Sci. U.S.S.R. 5: No. 2, 1964) 10. R. YUSUPALIYEV, Dissert. Cand. Chem. Sci., 182 pp., Tashkent State Univ., Tashkent, 1975 11. I. Yu. YAKUBOV, Author's Abstr. Dissert. Cand. Chem. Sci., 26 pp., Tashkent State Univ., Tashkent, 1980 12. T. N. KASTERINA and L. S. KALININA, Khimicheskiye metody issledovaniya sinteticheskikh stool i plasticheskikh mass (Chemical Methods of Investigating Synthetic Resins and Plastics) p. 55, Goskhimizdat, Moscow, 1963 13. S. A. TASHMUKHAMEDDV, Author's Abstr. Dissert. Cand. Chem. Sci., 18 pp., Tashkent State Univ., Tashkent, 1966 14. A. WEISBERGER, Fizicheskiye metody organicheskoi khimii (Physical Methods in Organic Chemistry) Vol. 1, p. 99, Inost. Lit., Moscow, 1950 15. M. A. MARTYNOV and K. A. VYLEGZHANINA, Rentgenografiya polimerov (X-ray Study o f Polymers)p. 15, Khimiya, Moscow, 1972
2282
Yu. K. GODOVSKIIand I. A. VOLEGOVA
16. A. P. GRIGOR'EV, Laboratornyi praktikum 13o tekhnologii plasticheskikh mass (Laboratory Practicum on Plastics Technology) Vol. 2, p. 227, Vyssh. shk., Moscow, 1977 17. Yu. A. PANSHIN, S. G. MAL'KEVICH and 'Is. S. DUNAYEVSKAYA, Ftoroplasty (Fluoroplasts) p. 100, Khimiya, Leningrad, 1978 18. S. G. YUL'CHIBAYEVA, A. MURATOV, A. A. YUL'CHIBAYEV and S. N. USMANOV, Vysokomol. soyed. A24: 722, 1982 (Translated in Polymer Sci. U.S.S.R. 24: 4, 800, 1982)
Polymer Science U.S.S.R. Vol. 28, No. 10, pp. 2282-2289, 1986 Printed in Poland
0032-3950]86 $10.00 + . 0 ~ © 1987 Pergamon Journals Ltd.
CRYSTALLIZATION AND MELTING OF POLYETHYLENE OXIDE IN A SYSTEM WITH A JOINTLY CURED DENSELY CROSSLINKED POLYMER* Yu. K. GODOVSKIIand I. A. VOLEGOVA Karpov Physicochemical Research Institute (Received 11 February 1985)
The calorimetric method has been employed to study the patterns of crystallization and melting of polyethylene oxide in a system with a melamine formaldehyde polymer cured jointly with it. The topology of the spatial densely crosslinked polymer network and chemical binding of the terminal groups of polyethylene oxide were found to have a strong influence on its behaviour on crystallization and melting. STUDY o f phase separations in polymer-polymer systems with one crystallizable c o m ponent is usually made in systems where the second amorphous component is also linear [1, 2]. However, it is of interest to investigate the behaviour of the crystallizable component in systems with a densely crosslinked polymer. The high density o f the threedimensional polymer network of the second component may lead to profound changes in the behaviour of the crystallizable component in such systems as compared with the homopolymer. Therefore the aim of this work is to study the features of the crystallization and melting of polyethylene oxide (PEO) in a polymer system with a melamine formaldehyde (MF) polymer jointly cured with it and which is the product o f polycondensation o f melamine derivatives and characterized by high density of the spatial network [3]. To obtain the MF-PEO systems investigated we used the hexamethyl ether of hexamethylot melamine (HM-3) of the following structure * Vysokomol. soyed. A28: No. 10, 2056-2062, 1986.