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Study of the supermolecular structure of superstrong viscose cord fibre
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6. T. ALFREY and H. MORAWETZ, J. Amer. Chem. Soc. 72: 1864, 1950 7. E. J. COHN and J. T. EDSALL, Proteins, Amino Acids and Peptides, Ch. 20, Reinhold Publishing Corp., New York, 1943 8. T. ALFREY and H. MORAWETZ, J. Amer. Chem. Soc. 74: 436, 1952 9. H. L. WAGNER and E. A. LANG, J. Polymer Sci. 55: 1512, 1951 10. A. KATCHALSKY and I. R. MILLER, J. Polymer Sci. 13: 57, 1954 11. F. W. FOREMAN, Biochem. J. 14: 451, i920 12. E. J. COHN and J. T. EDSALL, Proteins, Amino Acids and Peptides, Ch. 4, Reinhold Publishing Corp., New York, 1943 13. N. A. IZMAILOV, Elektrokhimiya rastvorov, (Electrochemistry of Solutions.) p. 541, Khar'kov University, 1959 14. R. M. FUOSS, J. Polymer Sci. 3: 603, 1948; 4: 96, 1949 15. W. SKODA and I. SCHURZ, Z. analyt. Chem. 162: 259, 1958
STUDY OF THE SUPERMOLECULAR STRUCTURE OF SUPERSTRONG VISCOSE CORD FIBRE* V. A . BERESTNEV, K . K H . RAZIKOV a n d V. A . K A R G I N Scientific-Research Institute of the Tyre Industry Institute of Polymer Chemistry, U.S.S.R. Academy of Sciences L. Ya. Karpov Physicochemical Institute (Received 23 June 1962)
I N A STUDY of u l t r a t h i n s e c t i o n s of C a p r o n c o r d fibre v a r i o u s t y p e s of c o m p o n e n t s u p e r m o l e c u l a r m a c r o f o r m a t i o n s were f o u n d t o be p r e s e n t in t h e s t r u c t u r e [1]. A n o t h e r f o r m of c o r d fibre u s e d i n d u s t r i a l l y is fibre f r o m r e g e n e r a t e d cellulose. A t t h e p r e s e n t t i m e t h e s o - c a l l e d s u p e r s t r o n g viscose fibre is w i d e l y u s e d for t h e p r o d u c t i o n of cord. S t u d y o f t h e s t r u c t u r a l p e c u l i a r i t i e s of t h i s fibre b y d i r e c t o b s e r v a t i o n is of b o t h t h e o r e t i c a l a n d p r a c t i c a l i n t e r e s t . EXPERIMENTAL The material chosen for investigation was the fibre of superstrong viscose cord of textile structure 5.45/1 × 2, the mechanical properties of which have been described in references [1] and [2]. The method of preparation of ultrathin sections was described in reference [3]. The ultrathin sections were examined in an electron microscope at direct electron-optical magnifications up to 30,000. In addition electron and X-ray diffraction investigations were carried out. The X-ray diffraction patterns were obtained from the scattering of Cu- and K~-radiation from a bundle of paraUel fibres, using a plane-walled cell. The limited-area electron diffraction patterns were obtained in the electron microscope. * Vysokomol. soyed. 6: No. 7, 1167-1173, 1964.
Superstrong viscose cord fibre
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RESULTS AND DISCUSSION
It has been shown previously [4, 5] t h a t cellulose hydrate fibre consists of macrofibrils within which there are large, supermolecular structural formations. The nature of these maeroformations differs in different fibres. The difference between the supermolecular structure of superstrong and low-strength fibre has been studied previously [5] and it was shown t h a t in the superstrong fibre the most widely distributed supermolecular formations are anisodiametric, needle-shaped particles distributed at random in the macrofibrils. I t was mentioned also t h a t there are other types of macroformation present. Some of these are examined in greater detail in the present work. Figure 1 shows a longitudinal section of a macrofibril. I t is seen t h a t the needle-shaped formations are not distributed in a random fashion but in distinct groups, in which t h e y are packed either parallel to one another or arranged radially about some central point. Larger macroformations, of which the elements are either parallel to one another or arranged radially are shown in Figures 2a and b. I t should be noted t h a t the component elements of these formations are not thin, needle-shaped particles but anisodiametrie plates or scales. The ordered, large, structural formations are present in the fibre in a substance of low optical density. Figure 3a shows an oblique section of a macrofibril from which some of this substance has fallen out. I n the remaining part there are globular, dense particles in addition to the large, ordered macroformations. Thus in viscose fibre, as in Capron [1] different types of structural macroformation can co-exist. These structural forms are not foreign particles or macroformations formed from the uniform structure during the process of preparation of the specimen. The t r u t h of the first statement will be confirmed below. The second is based on the following facts. On the one hand these macroformations are ordered to a considerable extent, therefore it is difficult to believe t h a t they arise as a result of breakdown of the material under the microtome knife during preparation of the specimen. Moreover the formation of structures during preparation of the section is a process made up of chance events and should lead to production of aggregates of very diverse form. However in fact perfectly uniform macrostructures occur, consisting of needle- or plate-like particles and globular structural elements. Furthermore it is seen from Figure 3a t h a t the ordered macroformations are distributed in a material of low optical density without a n y trace of disturbance in the b o u n d a r y layer, whereas when dense macroformations are formed from a material of low density there should be some disruption of the surface between these structural elements. Finally it has been shown [1] by shadowing ultrathin sections of Capron fibre with palladium t h a t there are depressions in the "binding" material of
t
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lOW optical density, left b y macroformations that have fallen out of the specimen. A similar picture can be obtained b y shadowing ultrathin sections of viscose fibre. That the material of which the above structural formations consist is identical with the material of the fibre as a whole is shown b y the X-ray and electron diffraction studies. Figure 4b shows half of an X-ray texture pattern obtained with a bundle of parallel fibres. The other half of this diagram (Fig. 4a) shows a limited-area electron diffraction pattern obtained in the electron microscope b y scattering from the edge of the macroformation shown in Figure 2b. The great similarity of the two diffraction patterns can be seen even b y visual examination. For a more detailed comparison of the patterns the interplanar spacings were calculated from the experimental data. The results obtained from the X-ray and electron diffraction investigation indicate that the optically dense macroformations consist of the same cellulose hydrate material as the fibre as a whole. The possibility of the existence in viscose fibre of structural macroformations giving a fairly sharp limited-area electron diffraction pattern is of particular interest. This indicates that the micromorphological forms of cellulose hydrate fibre can possess a very high degree of order. I t should be noted that the highest degree of order, though far from the possible maximum, observed in a large number of specimens (200-250) is possessed b y the macroformation shown in Figure 2b. The degrees of order of the other macroformations are lower than this. The electron diffraction patterns of these particles consist of fairly diffuse rings with individual, sharp, point reflections indicating different degrees of perfection of the structure. Similar patterns were obtained b y scattering of fast electrons b y the macroformations shown in Figures 1, 2a and 3a. From examination of the electron diffraction data it m a y be surmised however that disordering of the structure occurs on irradiation of the specimen with fast electrons during the examination of the specimen in the electron microscope, as was observed in the case of polyethylene spherulites [6-9]. In fact however the breakdown of structure under the beam occurs to only a slight extent and does not substantially alter the degree of order of the material. This is due firstly to the fact that all possible measures were taken to protect the specimen from the action of fast electrons (by observation of the following definite sequence in the production of the photographs: first the diffraction pattern ; the electron-micrograph of the specimen ; lowering of the anode current ; a check photograph after holding the specimen under the beam for a given time etc.). Secondly preparations with macroformations not giving a sharp diffraction pattern (see Figs. 1, 2a and 3a) were under the beam for the same length of time as preparations showing ordered particles. Consequently breakdown of structural order does not occur in this period of time. Thirdly the fact of the existence in cellulose fibres of structural forms that although externally ordered, are not perfect internally, is not surprising because it is known that
S u p e r s t r o n g viscose cord fibre
21
FIG. 1. P h o t o m i c r o g r a p h o f a l o n g i t u d i n a l section of a m a c r o f i b r i l of s u p e r s t r o n g viscose fibre. FIG. 2a, b. P h o t o m i c r o g r a p h s of a large, o r d e r e d m a c r o f o r m a t i o n f r o m a longit u d i n a l s e c t i o n of a m a e r o f i b r i l of s u p e r s t r o n g viscose fibre. FrG. 3a, b. P h o t o m i c r o g r a p h s of a n oblique section of a m a c r o f i b r i l of s u p e r s t r o n g viscose fibre. Fro. 4. D i f f r a c t i o n p a t t e r n s : a - - f a s t e l e c t r o n d i f f r a c t i o n p a t t e r n , b - - X - r a y diffraction pattern. FIG. 5. P h o t o m i c r o g r a p h o f a l o n g i t u d i n a l s e c t i o n of a m a c r o f i b r i l of s u p e r s t r o n g viscose fibre.
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such forms of macrostructure in cellulose can be obtained even in the form of pseudomorphs of monocrystals by saponification of its esters [10, 11]. The above data, indicating a high degree of order, call for a re-examination of the question of the crystallinity and amorphous condition of cellulose. All affirmations of the crystallinity of cellulose are based on experimental data on its high degree of order. This feature of the structure of cellulose is not in doubt. I t has been proved frequently by very different methods of investigation and finally has been shown clearly by direct observation in the present work. However the existence of ordering alone, even of a high degree, is not sufficient basis for calling the material crystalline. Another condition is also necessary, which is of itself a basic criterion of crystallinity, namely the occurence of the phase transition. This does not occur in cellulose, and this is also supported by a large amount of experimental data. The absence of the phase transition is the basis of the assertion that cellulose is amorphous. This fact, like the high degree of order is undoubted and denied by no-one. The fundamental error of authors who claim that cellulose is crystalline is t h a t they do not take the above fact into account, identifying the amorphous state only with complete disorder. Meanwhile it is well known t h a t even in typically amorphous polymeric materials a fairly high degree of order can arise, with formation of large, supermolecular aggregates. The existence of large, highly ordered regions does not contradict the fact t h a t cellulose is an amorphous material. The presence of maeroformations in cellulose is due to the great rigidity of the macromolecules, because the source of disorder in the structure of a polymer is deviation of the elements of molecular structure from the straightened form, as a result of which t h e y cannot lie in large aggregates. On the other hand the more rigid and the more linear the molecular chains the less the hindrance to the formation of complex structural forms. However the flexibility of the polymer chain (of regular structure) has a considerable effect on the ability of the polymer to crystallize. Very high rigidity of the macromolecules precludes the possibility of the occurence of crystalline order. Cellulose possesses such properties to the same degree as a number of other polymers. I n such polymers the formation of large structural formations is the result of chance aggregation of straightened elements of molecular structure. From these elements, which differ from one another, large, secondary macroformations are compiled. The fact that these primary aggregates are different predetermines the impossibility of development of the macroformations into complex, perfect structural forms. I n other words rigid chain polymers, of which cellulose is an example, can form structural aggregates, but however far reaching the degree of order of these m a y be they never attain the degree of perfection observed in crystalline polymers. The experimental data presented support this conclusion. They indicate
Superstrong viscose cord fibre
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that in superstrong viscose fibres there are very highly ordered structural macroformations. However attempts to obtain perfect structural forms of cellulose have not been successful--the artificially produced, large aggregates in the form of monocrystals were found to be only pseudomorphic forms [10, 11J. The presence in the fibres of the ordered macroformations seen in the photomicrographs shown above indicates that the structure of cellulose hydrate fibre is not uniform. However in our experiments as in a large number of other X-ray analyses of superstrong viscose fibre (see for example reference [12]) diffraction patterns from two (or more) types of molecular structure were not obtained. It m a y therefore be assumed that the molecular structure within the optically dense, large structural formations is approximately the same as that of the surrounding substance of low density. However this substance is not aggregated into large macroformations. In other words it follows from this that the molecules of the material of low optical density are orientated and ordered to a considerable extent. In the study of supermolecular structural formations the questions associated with investigation of the processes involved in their origination and develol)ment are of considerable interest. Some suggestions concerning the origin of macrostructural forms in superstrong viscose fibre can be made on the basis of the experimental results of the present work. Figure 3b shows a photomicrograph of an oblique section of a macrofibril of superstrong fibre. In this section can be seen semitransparent particles consisting of microfibrillar formations, either arranged radially or parallel to one another, which are still not perfectly formed. The individual sites of these formations are fairly well packed. It is evident that ordering of the macromolecules began at these sites. In addition to fibrillar macropartieles, globular forms also occur. These are probably formed b y the coiling of individual macromolecules that have not succeeded in aggregating, or of small, thin bundles of polymer chains of sufficient flexibility. Complete packing and ordering of the micro fibrils shown in Figure 3b leads to formation of aggregates of thin needles such as those illustrated in Figure 1. Subsequently these aggregates of small structural elements can continue to develop and enlarge to coarse particles such as those shown in Figures 2a and b. These particles, as mentioned above, consist of plate-like elements that are also probably formed b y aggregation of the needle-shaped microfibrils illustrated in Figure 1. I t is in fact seen in Figures 2a and b that the elements in the large macroformations, as in the small, are made up of either radial or parallel bundles. When the fibres are drawn breakdown of the structural macroformations occurs. B y analogy with the results of studies of the breakdown of large structural aggregates in polyethylene during orientation it m a y be supposed that the macroformations in superstrong viscose fibre break down either to individual, large, ordered elements [13] for example needle-shaped or plate-like elements,
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or to very small structural forms, for example bundles of macromolecules [6]. In practice it is evident that both processes occur simultaneously during stretching. If the first predominates a very large number of anisodiametric particles will have accumulated in the fibre after drawing, and these have a kind of, reinforcing effect, altering the properties of the fibre. This is the situation in superstrong cord fibre (Fig. 5). I f however the second process predominates a fibre is formed of heavy elements of molecular dimensions (bundles~ of macromolecules), orientated in the direction parallel to the axis of stretching. All these elements are more or less detached from one another [6] consequently there can be small voids (pores) between them, constituting defects in the structure of the specimen. This imparts different properties to the fibre from those imparted b y the first process. The effect of the presence or absence of reinforcing, ordered particles in viscose fibre has been discussed previously [5]. Structure formation during preparation of a fibre can be controlled by various means. One of these for example consists in variation of the parameters of the mechanical field in which the material is orientated, as is done in the drawing of Capron fibre [14, 15]. Another method consists in the addition of certain reagents to the material. In this connection the action of so-called modifiers is of interest, i.e. the compounds added in small quantities during various stages in the production of a fibre. Consideration of the nature of structure formation in superstrong viscose fibre must obviously take into account the addition of such modifiers during the commercial production of the fibre. It is of interest to take note of some of the special features (apart from those well known) of the action of these substances. In the formation of the fibre the modifier is probably the material added to the solvent for the cellulose xanthogenate that makes it a "poor" solvent for this cellulose ester. This causes aggregation of the polymer molecules and formation of macroformations already in the viscose solution. During the deposition of cellulose from this solution at the time of fibre formation these structural forms develop further. The majority of the modifiers used are surface-active substances. They lower the surface energy of the material, which favours the formation of new surfaces, and this accelerates the breakdown of large particles in the mechanical field [16]. Moreover the modifiers can function as so-called interstructural plasticizers, situated between the large, structural macroformations (for example between the separate plate-like elements shown in Figure 2b), b u t not penetrating into these (between the polymer molecules). During orientation of the fibre a plasticizer of this type assists in the breakdown of the macro-aggregates to large structural elements without disrupting the molecular structure of the elements themselves, and consequently without altering their properties. Thus during the drawing process the |arge macroformations break down into their component elements of large dimensions, and this is facilitated to a considerable extent b y the presence of modifiers in the fibre: As a result of
Superstrong viscose cord fibre
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this a fibre is produced that is self-reinforced by ordered (and therefore probably of high mechanical strength), anisodiametric particles, as was shown in references [5] and [17]. In the absence of modifiers however, for example in the formation of low-strength viscose fibre, in the first place fewer large aggregates are formed and secondly those macroformations that nevertheless do form do not break down to large elements during the time of drawing, but to very small structural forms (molecular bundles), forming a continuous structure full of fine pores. It was observed in reference [2] that low-strength fibre is more porous than superstrong f~re. From the above information it follows that superstrong viscose fibre has a complex micromorphology. The structure of this fibre contains various macroformations, the development of which has been slowed down at different stages of growth. The effect of the modifiers used in the productioll of the fibres has a considerable effect on the formation of the specific structure of superstrong viscose fibre. Comparison of the above results with those obtained in studies of the changes in macrostructure during orientation of polymeric materials such as films of polyethylene [6, 13] and polyethyleneterephthalate [ 18], polyamide fibres [ 14,15] etc., suggests that the formation of micromorphological structural forms in all truly orientated polymers takes place in two stages. During the production of the undrawn polymer large, ordered macroformations arise in its structure (evidently this already occurs in the viscose solution). When the polymer is drawn macrofibrils form, within which breakdown of these structural macroformations occurs, at first partially--into separate large elements (in which the internal ordering is preserved) and then completely--to small formations of the dimensions of molecular bundles. Therefore in order to obtain fibres of high mechanical strength, and selfreinforced fibre is of this class [5, 17], it is necessary to direct the above-mentioned stages in the process of micromorphological structure formation toward the production of ordered, anisodiametric particles.
:CONCLUSIONS 1. An experimental study of the micromorphology of superstrong viscose fibre has been made by electron microscopy and electron and X-ray diffraction analysis. 2. It is shown that in the drawn fibre there exist various structural macroformations, which can be highly ordered. 3. A mechanism of formation and growth of the large structural forms is proposed and discussed. Translated by E. O. PHILLIPS
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1. V . A . BERESTNEV, K. Kh. RAZIKOV and V. A. 'KARGIN, Vysokomol. soyed. 5: 1156, 1963 2. V. A. BERESTNEV, M. B. LYTKINA, T. V. GATOVSKAYA and V. A. KARGIN, K~im. volokna, No. 1, 71, 1962 3. K, Kh. RAZIKOV and G. S. MARKOVA, Vysokomol. soyed. 4: 913, 1962 4. V. A. BERESTNEV, K. Kh. RAZIKOV, E. S. ALEKSEYEVA and V. A. KARGIN, Dokl. Akad. N a u k SSSR 139: 1093, 1961 5. V. A. BERESTNEV, K. Kh. RAZIKOV a n d V. A. KARGIN, Khim. volokna, No. 4 51, 1962 6. V. A. KARGIN and T. A. KORETSKAYA, Dokl. Akad. l~auk S S S R d l O : 1015, 1957 7. V . A . KARGIN, J. Polymer Sci. 30: 252, 1958 8. B. I. ZVEREV, V. L. KARPOV and S. S. LESHCHENKO, Sb: Tr. 1-go Vses. soveshch. po radiatsionnoi khimii. (Transactions of the 1st All-Union Conference on R a d i a t i o n Chemistry.) p. 274, Izd. Akad. N a u k SSSR, 1958 9. A. KELLER, J. Polymer Sci. 36: 361, 1959 10. B. G. R A N B ¥ and R. W. NOE, J. Polymer, Sci. 51: 337, 1961 I I . R. St.-J. MANLEY, Nature 189: 390, 1961 12. D. Ya, TSVANKIN, Dissertation, I n s t i t u t e of Hereto-Organic Compounds, U.S.S.R. A c a d e m y of Sciences, Moscow, 1958 13. A. BROWN, J. Appl. Phys. 20: 552, 1949 14. M. P. NOSOV and V. A. BERESTNEV, Vysokomol. soyed. 5: 1080, 1963 15. D. C. HOOKWAY, J. Text, Inst. 49: 292, 1958 16. P. A. REBINDER, Yubileinyi sbornik k X X X - l e t i y u Okt. sots. rev. (Jubilee Collection for the 30th Anniversary of the October Socialist Revolution.) p. 533, Izd. Akad. l~auk SSSR, 1947 17. V. A. BERESTNEV a n d V. A. KARGIN, Vysokomol. soyed. 5: 581, 1963 18. V. A. BERESTNEV, G. I. BERESTNEVA, T. V. GATOVSKAYA, V. A. KARGIN a n d P. V. KOZLOV, Vysokomol. soyed. 3: 801, 1961
THE EFFECT OF THE cis- AND trans-CONFIGURATIONS OF ETHYLENE-1,2-DICARBOXYLIC ACIDS ON THE PROPERTIES OF THEIR COPOLYMERS WITH 2-METHYL-5-VINYLPYRIDINE* V. S. LEBEDEV, N. N. LOGINOVA and R. K. GAVURINA Lensoviet Technological Institute, Leningrad
(Received 24 December 1962)
WE HAVE previously reported a study of an amphoteric copolymer of fumaric acid (FA) and 2-methyl-5-vinylpyridine (MVP) [1]. In the present work a study was made of the analogous copolymer of MVP and maleic acid (MA). * Vysokomol. soyed. 6: No. 7, 1174-1180, 1964.
V. A. BERESTNE¥ et al.
6. T. ALFREY and H. MORAWETZ, J. Amer. Chem. Soc. 72: 1864, 1950 7. E. J. COHN and J. T. EDSALL, Proteins, Amino Acids and Peptides, Ch. 20, Reinhold Publishing Corp., New York, 1943 8. T. ALFREY and H. MORAWETZ, J. Amer. Chem. Soc. 74: 436, 1952 9. H. L. WAGNER and E. A. LANG, J. Polymer Sci. 55: 1512, 1951 10. A. KATCHALSKY and I. R. MILLER, J. Polymer Sci. 13: 57, 1954 11. F. W. FOREMAN, Biochem. J. 14: 451, i920 12. E. J. COHN and J. T. EDSALL, Proteins, Amino Acids and Peptides, Ch. 4, Reinhold Publishing Corp., New York, 1943 13. N. A. IZMAILOV, Elektrokhimiya rastvorov, (Electrochemistry of Solutions.) p. 541, Khar'kov University, 1959 14. R. M. FUOSS, J. Polymer Sci. 3: 603, 1948; 4: 96, 1949 15. W. SKODA and I. SCHURZ, Z. analyt. Chem. 162: 259, 1958
STUDY OF THE SUPERMOLECULAR STRUCTURE OF SUPERSTRONG VISCOSE CORD FIBRE* V. A . BERESTNEV, K . K H . RAZIKOV a n d V. A . K A R G I N Scientific-Research Institute of the Tyre Industry Institute of Polymer Chemistry, U.S.S.R. Academy of Sciences L. Ya. Karpov Physicochemical Institute (Received 23 June 1962)
I N A STUDY of u l t r a t h i n s e c t i o n s of C a p r o n c o r d fibre v a r i o u s t y p e s of c o m p o n e n t s u p e r m o l e c u l a r m a c r o f o r m a t i o n s were f o u n d t o be p r e s e n t in t h e s t r u c t u r e [1]. A n o t h e r f o r m of c o r d fibre u s e d i n d u s t r i a l l y is fibre f r o m r e g e n e r a t e d cellulose. A t t h e p r e s e n t t i m e t h e s o - c a l l e d s u p e r s t r o n g viscose fibre is w i d e l y u s e d for t h e p r o d u c t i o n of cord. S t u d y o f t h e s t r u c t u r a l p e c u l i a r i t i e s of t h i s fibre b y d i r e c t o b s e r v a t i o n is of b o t h t h e o r e t i c a l a n d p r a c t i c a l i n t e r e s t . EXPERIMENTAL The material chosen for investigation was the fibre of superstrong viscose cord of textile structure 5.45/1 × 2, the mechanical properties of which have been described in references [1] and [2]. The method of preparation of ultrathin sections was described in reference [3]. The ultrathin sections were examined in an electron microscope at direct electron-optical magnifications up to 30,000. In addition electron and X-ray diffraction investigations were carried out. The X-ray diffraction patterns were obtained from the scattering of Cu- and K~-radiation from a bundle of paraUel fibres, using a plane-walled cell. The limited-area electron diffraction patterns were obtained in the electron microscope. * Vysokomol. soyed. 6: No. 7, 1167-1173, 1964.
Superstrong viscose cord fibre
1283
RESULTS AND DISCUSSION
It has been shown previously [4, 5] t h a t cellulose hydrate fibre consists of macrofibrils within which there are large, supermolecular structural formations. The nature of these maeroformations differs in different fibres. The difference between the supermolecular structure of superstrong and low-strength fibre has been studied previously [5] and it was shown t h a t in the superstrong fibre the most widely distributed supermolecular formations are anisodiametric, needle-shaped particles distributed at random in the macrofibrils. I t was mentioned also t h a t there are other types of macroformation present. Some of these are examined in greater detail in the present work. Figure 1 shows a longitudinal section of a macrofibril. I t is seen t h a t the needle-shaped formations are not distributed in a random fashion but in distinct groups, in which t h e y are packed either parallel to one another or arranged radially about some central point. Larger macroformations, of which the elements are either parallel to one another or arranged radially are shown in Figures 2a and b. I t should be noted t h a t the component elements of these formations are not thin, needle-shaped particles but anisodiametrie plates or scales. The ordered, large, structural formations are present in the fibre in a substance of low optical density. Figure 3a shows an oblique section of a macrofibril from which some of this substance has fallen out. I n the remaining part there are globular, dense particles in addition to the large, ordered macroformations. Thus in viscose fibre, as in Capron [1] different types of structural macroformation can co-exist. These structural forms are not foreign particles or macroformations formed from the uniform structure during the process of preparation of the specimen. The t r u t h of the first statement will be confirmed below. The second is based on the following facts. On the one hand these macroformations are ordered to a considerable extent, therefore it is difficult to believe t h a t they arise as a result of breakdown of the material under the microtome knife during preparation of the specimen. Moreover the formation of structures during preparation of the section is a process made up of chance events and should lead to production of aggregates of very diverse form. However in fact perfectly uniform macrostructures occur, consisting of needle- or plate-like particles and globular structural elements. Furthermore it is seen from Figure 3a t h a t the ordered macroformations are distributed in a material of low optical density without a n y trace of disturbance in the b o u n d a r y layer, whereas when dense macroformations are formed from a material of low density there should be some disruption of the surface between these structural elements. Finally it has been shown [1] by shadowing ultrathin sections of Capron fibre with palladium t h a t there are depressions in the "binding" material of
t
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lOW optical density, left b y macroformations that have fallen out of the specimen. A similar picture can be obtained b y shadowing ultrathin sections of viscose fibre. That the material of which the above structural formations consist is identical with the material of the fibre as a whole is shown b y the X-ray and electron diffraction studies. Figure 4b shows half of an X-ray texture pattern obtained with a bundle of parallel fibres. The other half of this diagram (Fig. 4a) shows a limited-area electron diffraction pattern obtained in the electron microscope b y scattering from the edge of the macroformation shown in Figure 2b. The great similarity of the two diffraction patterns can be seen even b y visual examination. For a more detailed comparison of the patterns the interplanar spacings were calculated from the experimental data. The results obtained from the X-ray and electron diffraction investigation indicate that the optically dense macroformations consist of the same cellulose hydrate material as the fibre as a whole. The possibility of the existence in viscose fibre of structural macroformations giving a fairly sharp limited-area electron diffraction pattern is of particular interest. This indicates that the micromorphological forms of cellulose hydrate fibre can possess a very high degree of order. I t should be noted that the highest degree of order, though far from the possible maximum, observed in a large number of specimens (200-250) is possessed b y the macroformation shown in Figure 2b. The degrees of order of the other macroformations are lower than this. The electron diffraction patterns of these particles consist of fairly diffuse rings with individual, sharp, point reflections indicating different degrees of perfection of the structure. Similar patterns were obtained b y scattering of fast electrons b y the macroformations shown in Figures 1, 2a and 3a. From examination of the electron diffraction data it m a y be surmised however that disordering of the structure occurs on irradiation of the specimen with fast electrons during the examination of the specimen in the electron microscope, as was observed in the case of polyethylene spherulites [6-9]. In fact however the breakdown of structure under the beam occurs to only a slight extent and does not substantially alter the degree of order of the material. This is due firstly to the fact that all possible measures were taken to protect the specimen from the action of fast electrons (by observation of the following definite sequence in the production of the photographs: first the diffraction pattern ; the electron-micrograph of the specimen ; lowering of the anode current ; a check photograph after holding the specimen under the beam for a given time etc.). Secondly preparations with macroformations not giving a sharp diffraction pattern (see Figs. 1, 2a and 3a) were under the beam for the same length of time as preparations showing ordered particles. Consequently breakdown of structural order does not occur in this period of time. Thirdly the fact of the existence in cellulose fibres of structural forms that although externally ordered, are not perfect internally, is not surprising because it is known that
S u p e r s t r o n g viscose cord fibre
21
FIG. 1. P h o t o m i c r o g r a p h o f a l o n g i t u d i n a l section of a m a c r o f i b r i l of s u p e r s t r o n g viscose fibre. FIG. 2a, b. P h o t o m i c r o g r a p h s of a large, o r d e r e d m a c r o f o r m a t i o n f r o m a longit u d i n a l s e c t i o n of a m a e r o f i b r i l of s u p e r s t r o n g viscose fibre. FrG. 3a, b. P h o t o m i c r o g r a p h s of a n oblique section of a m a c r o f i b r i l of s u p e r s t r o n g viscose fibre. Fro. 4. D i f f r a c t i o n p a t t e r n s : a - - f a s t e l e c t r o n d i f f r a c t i o n p a t t e r n , b - - X - r a y diffraction pattern. FIG. 5. P h o t o m i c r o g r a p h o f a l o n g i t u d i n a l s e c t i o n of a m a c r o f i b r i l of s u p e r s t r o n g viscose fibre.
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such forms of macrostructure in cellulose can be obtained even in the form of pseudomorphs of monocrystals by saponification of its esters [10, 11]. The above data, indicating a high degree of order, call for a re-examination of the question of the crystallinity and amorphous condition of cellulose. All affirmations of the crystallinity of cellulose are based on experimental data on its high degree of order. This feature of the structure of cellulose is not in doubt. I t has been proved frequently by very different methods of investigation and finally has been shown clearly by direct observation in the present work. However the existence of ordering alone, even of a high degree, is not sufficient basis for calling the material crystalline. Another condition is also necessary, which is of itself a basic criterion of crystallinity, namely the occurence of the phase transition. This does not occur in cellulose, and this is also supported by a large amount of experimental data. The absence of the phase transition is the basis of the assertion that cellulose is amorphous. This fact, like the high degree of order is undoubted and denied by no-one. The fundamental error of authors who claim that cellulose is crystalline is t h a t they do not take the above fact into account, identifying the amorphous state only with complete disorder. Meanwhile it is well known t h a t even in typically amorphous polymeric materials a fairly high degree of order can arise, with formation of large, supermolecular aggregates. The existence of large, highly ordered regions does not contradict the fact t h a t cellulose is an amorphous material. The presence of maeroformations in cellulose is due to the great rigidity of the macromolecules, because the source of disorder in the structure of a polymer is deviation of the elements of molecular structure from the straightened form, as a result of which t h e y cannot lie in large aggregates. On the other hand the more rigid and the more linear the molecular chains the less the hindrance to the formation of complex structural forms. However the flexibility of the polymer chain (of regular structure) has a considerable effect on the ability of the polymer to crystallize. Very high rigidity of the macromolecules precludes the possibility of the occurence of crystalline order. Cellulose possesses such properties to the same degree as a number of other polymers. I n such polymers the formation of large structural formations is the result of chance aggregation of straightened elements of molecular structure. From these elements, which differ from one another, large, secondary macroformations are compiled. The fact that these primary aggregates are different predetermines the impossibility of development of the macroformations into complex, perfect structural forms. I n other words rigid chain polymers, of which cellulose is an example, can form structural aggregates, but however far reaching the degree of order of these m a y be they never attain the degree of perfection observed in crystalline polymers. The experimental data presented support this conclusion. They indicate
Superstrong viscose cord fibre
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that in superstrong viscose fibres there are very highly ordered structural macroformations. However attempts to obtain perfect structural forms of cellulose have not been successful--the artificially produced, large aggregates in the form of monocrystals were found to be only pseudomorphic forms [10, 11J. The presence in the fibres of the ordered macroformations seen in the photomicrographs shown above indicates that the structure of cellulose hydrate fibre is not uniform. However in our experiments as in a large number of other X-ray analyses of superstrong viscose fibre (see for example reference [12]) diffraction patterns from two (or more) types of molecular structure were not obtained. It m a y therefore be assumed that the molecular structure within the optically dense, large structural formations is approximately the same as that of the surrounding substance of low density. However this substance is not aggregated into large macroformations. In other words it follows from this that the molecules of the material of low optical density are orientated and ordered to a considerable extent. In the study of supermolecular structural formations the questions associated with investigation of the processes involved in their origination and develol)ment are of considerable interest. Some suggestions concerning the origin of macrostructural forms in superstrong viscose fibre can be made on the basis of the experimental results of the present work. Figure 3b shows a photomicrograph of an oblique section of a macrofibril of superstrong fibre. In this section can be seen semitransparent particles consisting of microfibrillar formations, either arranged radially or parallel to one another, which are still not perfectly formed. The individual sites of these formations are fairly well packed. It is evident that ordering of the macromolecules began at these sites. In addition to fibrillar macropartieles, globular forms also occur. These are probably formed b y the coiling of individual macromolecules that have not succeeded in aggregating, or of small, thin bundles of polymer chains of sufficient flexibility. Complete packing and ordering of the micro fibrils shown in Figure 3b leads to formation of aggregates of thin needles such as those illustrated in Figure 1. Subsequently these aggregates of small structural elements can continue to develop and enlarge to coarse particles such as those shown in Figures 2a and b. These particles, as mentioned above, consist of plate-like elements that are also probably formed b y aggregation of the needle-shaped microfibrils illustrated in Figure 1. I t is in fact seen in Figures 2a and b that the elements in the large macroformations, as in the small, are made up of either radial or parallel bundles. When the fibres are drawn breakdown of the structural macroformations occurs. B y analogy with the results of studies of the breakdown of large structural aggregates in polyethylene during orientation it m a y be supposed that the macroformations in superstrong viscose fibre break down either to individual, large, ordered elements [13] for example needle-shaped or plate-like elements,
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or to very small structural forms, for example bundles of macromolecules [6]. In practice it is evident that both processes occur simultaneously during stretching. If the first predominates a very large number of anisodiametric particles will have accumulated in the fibre after drawing, and these have a kind of, reinforcing effect, altering the properties of the fibre. This is the situation in superstrong cord fibre (Fig. 5). I f however the second process predominates a fibre is formed of heavy elements of molecular dimensions (bundles~ of macromolecules), orientated in the direction parallel to the axis of stretching. All these elements are more or less detached from one another [6] consequently there can be small voids (pores) between them, constituting defects in the structure of the specimen. This imparts different properties to the fibre from those imparted b y the first process. The effect of the presence or absence of reinforcing, ordered particles in viscose fibre has been discussed previously [5]. Structure formation during preparation of a fibre can be controlled by various means. One of these for example consists in variation of the parameters of the mechanical field in which the material is orientated, as is done in the drawing of Capron fibre [14, 15]. Another method consists in the addition of certain reagents to the material. In this connection the action of so-called modifiers is of interest, i.e. the compounds added in small quantities during various stages in the production of a fibre. Consideration of the nature of structure formation in superstrong viscose fibre must obviously take into account the addition of such modifiers during the commercial production of the fibre. It is of interest to take note of some of the special features (apart from those well known) of the action of these substances. In the formation of the fibre the modifier is probably the material added to the solvent for the cellulose xanthogenate that makes it a "poor" solvent for this cellulose ester. This causes aggregation of the polymer molecules and formation of macroformations already in the viscose solution. During the deposition of cellulose from this solution at the time of fibre formation these structural forms develop further. The majority of the modifiers used are surface-active substances. They lower the surface energy of the material, which favours the formation of new surfaces, and this accelerates the breakdown of large particles in the mechanical field [16]. Moreover the modifiers can function as so-called interstructural plasticizers, situated between the large, structural macroformations (for example between the separate plate-like elements shown in Figure 2b), b u t not penetrating into these (between the polymer molecules). During orientation of the fibre a plasticizer of this type assists in the breakdown of the macro-aggregates to large structural elements without disrupting the molecular structure of the elements themselves, and consequently without altering their properties. Thus during the drawing process the |arge macroformations break down into their component elements of large dimensions, and this is facilitated to a considerable extent b y the presence of modifiers in the fibre: As a result of
Superstrong viscose cord fibre
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this a fibre is produced that is self-reinforced by ordered (and therefore probably of high mechanical strength), anisodiametric particles, as was shown in references [5] and [17]. In the absence of modifiers however, for example in the formation of low-strength viscose fibre, in the first place fewer large aggregates are formed and secondly those macroformations that nevertheless do form do not break down to large elements during the time of drawing, but to very small structural forms (molecular bundles), forming a continuous structure full of fine pores. It was observed in reference [2] that low-strength fibre is more porous than superstrong f~re. From the above information it follows that superstrong viscose fibre has a complex micromorphology. The structure of this fibre contains various macroformations, the development of which has been slowed down at different stages of growth. The effect of the modifiers used in the productioll of the fibres has a considerable effect on the formation of the specific structure of superstrong viscose fibre. Comparison of the above results with those obtained in studies of the changes in macrostructure during orientation of polymeric materials such as films of polyethylene [6, 13] and polyethyleneterephthalate [ 18], polyamide fibres [ 14,15] etc., suggests that the formation of micromorphological structural forms in all truly orientated polymers takes place in two stages. During the production of the undrawn polymer large, ordered macroformations arise in its structure (evidently this already occurs in the viscose solution). When the polymer is drawn macrofibrils form, within which breakdown of these structural macroformations occurs, at first partially--into separate large elements (in which the internal ordering is preserved) and then completely--to small formations of the dimensions of molecular bundles. Therefore in order to obtain fibres of high mechanical strength, and selfreinforced fibre is of this class [5, 17], it is necessary to direct the above-mentioned stages in the process of micromorphological structure formation toward the production of ordered, anisodiametric particles.
:CONCLUSIONS 1. An experimental study of the micromorphology of superstrong viscose fibre has been made by electron microscopy and electron and X-ray diffraction analysis. 2. It is shown that in the drawn fibre there exist various structural macroformations, which can be highly ordered. 3. A mechanism of formation and growth of the large structural forms is proposed and discussed. Translated by E. O. PHILLIPS
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1. V . A . BERESTNEV, K. Kh. RAZIKOV and V. A. 'KARGIN, Vysokomol. soyed. 5: 1156, 1963 2. V. A. BERESTNEV, M. B. LYTKINA, T. V. GATOVSKAYA and V. A. KARGIN, K~im. volokna, No. 1, 71, 1962 3. K, Kh. RAZIKOV and G. S. MARKOVA, Vysokomol. soyed. 4: 913, 1962 4. V. A. BERESTNEV, K. Kh. RAZIKOV, E. S. ALEKSEYEVA and V. A. KARGIN, Dokl. Akad. N a u k SSSR 139: 1093, 1961 5. V. A. BERESTNEV, K. Kh. RAZIKOV a n d V. A. KARGIN, Khim. volokna, No. 4 51, 1962 6. V. A. KARGIN and T. A. KORETSKAYA, Dokl. Akad. l~auk S S S R d l O : 1015, 1957 7. V . A . KARGIN, J. Polymer Sci. 30: 252, 1958 8. B. I. ZVEREV, V. L. KARPOV and S. S. LESHCHENKO, Sb: Tr. 1-go Vses. soveshch. po radiatsionnoi khimii. (Transactions of the 1st All-Union Conference on R a d i a t i o n Chemistry.) p. 274, Izd. Akad. N a u k SSSR, 1958 9. A. KELLER, J. Polymer Sci. 36: 361, 1959 10. B. G. R A N B ¥ and R. W. NOE, J. Polymer, Sci. 51: 337, 1961 I I . R. St.-J. MANLEY, Nature 189: 390, 1961 12. D. Ya, TSVANKIN, Dissertation, I n s t i t u t e of Hereto-Organic Compounds, U.S.S.R. A c a d e m y of Sciences, Moscow, 1958 13. A. BROWN, J. Appl. Phys. 20: 552, 1949 14. M. P. NOSOV and V. A. BERESTNEV, Vysokomol. soyed. 5: 1080, 1963 15. D. C. HOOKWAY, J. Text, Inst. 49: 292, 1958 16. P. A. REBINDER, Yubileinyi sbornik k X X X - l e t i y u Okt. sots. rev. (Jubilee Collection for the 30th Anniversary of the October Socialist Revolution.) p. 533, Izd. Akad. l~auk SSSR, 1947 17. V. A. BERESTNEV a n d V. A. KARGIN, Vysokomol. soyed. 5: 581, 1963 18. V. A. BERESTNEV, G. I. BERESTNEVA, T. V. GATOVSKAYA, V. A. KARGIN a n d P. V. KOZLOV, Vysokomol. soyed. 3: 801, 1961
THE EFFECT OF THE cis- AND trans-CONFIGURATIONS OF ETHYLENE-1,2-DICARBOXYLIC ACIDS ON THE PROPERTIES OF THEIR COPOLYMERS WITH 2-METHYL-5-VINYLPYRIDINE* V. S. LEBEDEV, N. N. LOGINOVA and R. K. GAVURINA Lensoviet Technological Institute, Leningrad
(Received 24 December 1962)
WE HAVE previously reported a study of an amphoteric copolymer of fumaric acid (FA) and 2-methyl-5-vinylpyridine (MVP) [1]. In the present work a study was made of the analogous copolymer of MVP and maleic acid (MA). * Vysokomol. soyed. 6: No. 7, 1174-1180, 1964.