Infra-Red Spectra of Rubber and High Polymers

1941 ◽  
Vol 14 (3) ◽  
pp. 572-579
Author(s):  
W. C. Sears
Keyword(s):  
Methyl Methacrylate ◽  
Fair Agreement ◽  
Chain Molecules ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Gutta Percha ◽  
Infra Red ◽  
Related Compounds ◽  
Long Chain ◽  
High Polymers

Abstract The rubber industry is interested in all methods for studying the structure of highly polymerized substances. Infra-red spectroscopy has been recognized by recent workers as a possible means for determining the valence forces in long chain molecules. Accordingly, the infra-red spectra of rubber and related compounds have been measured by several workers. An investigation of rubber, gutta percha, indene, polyindene, styrene, polystyrene, polyvinylacetate and polyvinylchloracetate has been carried out by Stair and Coblentz. Later Williams measured natural and vulcanized rubber, rubber hydrochloride, isoprene, styrene and polymerized butadiene in the region between 2.5µ and 9µ, but his spectra of rubber did not agree with that of Stair and Coblentz. Williams and Taschek reported that the bands in rubber become broader with increasing stretch. Recently a rough survey of the infra-red transmission of rubber, Pliofilm, Vinylite XYSG, Shawinigan V-15, polystyrene, methyl methacrylate polymer and Cellophane has been made by Wells. The Raman data of rubber obtained by Gehman and Osterhof are in fair agreement with the infra-red results of Stair and Coblentz.

Permanent Set in Vulcanized Rubber

1949 ◽  
Vol 22 (4) ◽  
pp. 1036-1044 ◽  
Author(s):  
L. Mullins
Keyword(s):  
Plastic Flow ◽  
Room Temperature ◽  
Elastic Recovery ◽  
The Other ◽  
Initial Length ◽  
Chain Molecules ◽  
Permanent Set ◽  
Vulcanized Rubber ◽  
Rate Of Recovery ◽  
Long Chain

Abstract The residual extension which remains after a sample of rubber has been stretched for some period, then released and allowed to recover, is popularly called permanent set. This set, however, is far from being permanent since it continuously decreases with the period of recovery; furthermore, after the rate of recovery has become exceedingly slow and is no longer readily observable, an increase in temperature will usually result in a sharp increase in the rate of recovery. It has been usual to identify this set with irreversible plastic flow, but it will be immediately evident that this can rarely be justified for, owing to incomplete high-elastic recovery, the measured value of set is a combination of both plastic flow and high-elastic deformation which has not completely recovered. Thus before any attempt is made to discuss the interpretation of the results of set tests, a study must be made of the significance of set. Treloar has investigated this phenomenon in raw natural rubber and has shown that entanglements or cohesional linkages may form while the rubber is stretched, and these oppose recovery; further, although van der Waals forces between the long-chain molecules largely control the rate and the amount of recovery, the crystallization of rubber produced by stretching may profoundly influence the set. On the other hand Tobolsky has studied the set which results from stretching rubber vulcanizates at high temperatures ; in such cases the amount of set is controlled by two processes which take place while the rubber is stretched; one of these involves the oxidative breaking of network chains, the other the oxidative cross-linking of network chains. Although these ideas are well founded, they do not provide a completely satisfactory basis for the understanding of set, and the purpose of this work is to extend these ideas and to explain the significance of the results of normal set tests ; in these tests rubber samples were extended at room temperatures to moderate elongations for relatively short periods of time. Most of the tests performed in this investigation were made on dumbbell shaped samples, which were extended by 200 per cent of their initial length for fifteen minutes at room temperature and then allowed to recover for one hour at room temperature; the residual extension was then noted and expressed as a percentage of the initial length. These tests will be referred to as normal set tests. In some tests various periods and temperatures of extension and recovery were used.

scholarly journals Molecular structure and rubber-like elasticity I. The crystal structures of β gutta-percha, rubber and polychloroprene

1942 ◽  
Vol 180 (980) ◽  
pp. 40-66 ◽  
Keyword(s):  
Double Bond ◽  
Crystal Structures ◽  
Structural Unit ◽  
Chain Molecules ◽  
Space Group ◽  
Left Handed ◽  
Gutta Percha ◽  
Chain Unit ◽  
Pass Through ◽  
Long Chain

The crystal structures of β gutta-percha, rubber and polychloroprene have been determined by interpretation of X-ray diffraction photographs. β Gutta-percha (—CH 2 —C(CH 3 )=CH—CH 2 —)n is orthorhombic, with axial lengths a 0 = 7.78 A, b 0 = 11.78 A, c 0 = 4.72 A. Four long-chain molecules pass through this cell parallel to the c axis. The space group is P 2 1 2 1 2 1 , and the co-ordinates of the five carbon atoms of one structural unit are: (CH 2 ) 0.926 (C) 0.000 (CH) 0.000 (CH 2 ) 0.074 (CH 3 ) 0.970 0.110 0.146 0.074 0.110 0.277 0.676 0.960 0.177 0.462 0.980 The molecules are asymmetric; all the molecules passing through any one crystal are identical—either left-handed or right-handed, not mixed. The carbon chain is a non-planar zigzag; each chain unit C—C=C—C is planar, and has the trans configuration, but the connecting links (CH 2 —CH 2 ) lie in a different plane; the plane —C—C—C = makes an angle of 115° with plane —C—C=C—. a Gutta-percha molecules probably also have the trans double-bond configuration, and differ from β molecules only in the positions of the CH 2 —CH 2 bonds; the chain form is thus different from that of β molecules. Crystalline rubber (also (—CH 2 — C(CH 3 )=CH — CH 2 — ) n ) is monoclinic, and has a 0 = 12.46 A, b 0 = 8.89 A, c 0 = 8.10 A, β = 92°. Four long-chain molecules pass through this cell parallel to the c axis. The space group is P 2 1 / a and the co-ordinates of the ten carbon atoms of one structural chain unit are (CH 2 ) 0.753 (C) 0.854 (CH) 0.845 (CH 2 ) 0.745 (CH 3 ) 0.968 0.899 0.865 0.905 0.959 0.876 0.802 0.703 0.542 0.457 0.773 (CH 2 ) 0.744 (C) 0.644 (CH) 0.659 (CH 2 ) 0.757 (CH 3 ) 0.532 0.834 0.874 0.905 0.834 0.828 0.326 0.215 0.052 0.975 0.268 The molecules are asymmetric; two of the molecules passing through the unit cell are left-handed and two right-handed. The chain carbon atoms of any one molecule form a non-planar zigzag, in which the double-bond units C— C=C— C have the cis configuration. The two isoprene units C —C—C=C —C— which make up the structural unit are not identical in configuration; the distortion appears to be due to intermolecular forces. The structure of crystalline polychloroprene (—CH 2 —CCl=CH—CH 2 — ) n is completely analogous to that of (i gutta-percha. The cell is orthorhombic, with a 0 = 8.84 A, b 0 = 10.24 A, c 0 = 4.79 A. The co-ordinates of carbon and chlorine atoms are (CH 2 ) 0.077 (C) 0.033 (CH) 0.008 (CH 2 ) 0.970 Cl 0.167 0.054 0.115 0.034 0.099 0.243 0.278 0.000 0.787 0.509 0.000

The use of polarized infra-red radiation in the study of doubly oriented long-chain polymers

1949 ◽  
Vol 199 (1057) ◽  
pp. 183-198 ◽  
Keyword(s):  
Hydrogen Bonding ◽  
Polyvinyl Alcohol ◽  
Strong Support ◽  
Nylon 66 ◽  
Polyvinylidene Chloride ◽  
Infra Red ◽  
Valency Angle ◽  
Red Radiation ◽  
Long Chain ◽  
High Polymers

The use of polarized infra-red radiation in examining the structure and orientation of high polymers has been investigated quantitatively. It is shown that infra-red spectroscopy can furnish evidence for double orientation in rolled sheets of nylon 66, polyvinyl alcohol and (with less certainty) polythene. In the case of polyvinyl formate, acetate, chloride and polyvinylidene chloride such double orientation could not be detected. Evidence is given to show that in nylon the N -H bond is bent by hydrogen bonding forces, the angle between this bond and the plane of the skeleton being thereby reduced from 39° (the valency angle) to 22°. The structure of polyvinyl alcohol recently proposed by Bunn receives strong support from the absence of dichroism in the O-H frequency in the spectrum of that material, when a doubly oriented specimen is examined.

Molecular Structure and Rubberlike Elasticity. II. The Stereochemistry of Chain Polymers

1942 ◽  
Vol 15 (4) ◽  
pp. 731-741
Author(s):  
C. W. Bunn
Keyword(s):  
Molecular Geometry ◽  
Sufficient Evidence ◽  
Zigzag Chain ◽  
X Ray Diffraction ◽  
Molecular Physics ◽  
Chain Molecules ◽  
X Ray ◽  
Gutta Percha ◽  
Extended Plane ◽  
Long Chain

Abstract In Part I of this work, the determination of the crystal structures of three long-chain polymers by interpretation of x-ray diffraction photographs was described. In all three crystals—β-gutta-percha, rubber and polychloroprene—themolecules have nonplanar zigzag chain forms and are asymmetric. It is now necessary to consider the bearing of the new knowledge of molecular geometry on the possibility of understanding rubber like properties in terms of molecular physics. It is widely believed that the flexibility, softness and other characteristic properties of rubberlike substances are in some way due to the flexibility of the molecules themselves. Long-chain molecules owe their potential flexibility to the swivelling of the chain units around the single bonds as axes, and it is therefore necessary to consider which bond positions are the most stable and what hindrances there are to rotation away from these positions. The present paper deals chiefly with the question of the most stable bond positions. The enquiry has interest, not only in relation to the problem of the origin of rubberlike properties, but also because it opens the way to a systematic consideration of chain types. There is already evidence that in many crystalline long-chain polymers, such as rubber hydrochloride, polyisobutylene, and some of the polyesters, the chains have not the fully extended plane zigzag form of polyethylene, but somewhat shortened (necessarily nonplanar) forms. It should be possible to discover what these forms are by interpretation of x-ray diffraction photographs, but the difficulties are in some cases formidable; some assistance in the form of guiding principles for the construction of possible chain types is desirable. It is the purpose of this paper to show that sufficient evidence already exists to suggest a general principle regulating bond positions in aliphatic molecules containing sequences of singly linked atoms. It will be called the principle of staggered bonds. In the three molecules whose structures were determined in Part I, every fourth chain bond is a double bond; the question of bond positions is less simple for such molecules than it is for those in which all the bonds are single. The latter will therefore be considered first.

Torsional absorption spectra of long-chain substances in the solid state

1961 ◽  
Vol 264 (1317) ◽  
pp. 212-220 ◽  
Keyword(s):  
Solid State ◽  
Absorption Spectra ◽  
Intermolecular Forces ◽  
The Other ◽  
Torsional Vibrations ◽  
Chain Molecules ◽  
Absorption Intensity ◽  
Infra Red ◽  
Long Chain ◽  
Isolated Molecules

The absorption spectra connected with the torsional vibrations of long-chain substances are calculated. Ketones are treated in detail, but the results can also be applied to other long-chain molecules with simple dipolar groups. It is shown that the torsional frequencies of a long-chain ketone are very similar to those of the parent hydrocarbon. But the presence of the ketone group makes the vibrations active in the spectrum. For a molecule with L carbon atoms there are L — 3 torsional vibrations. For isolated molecules in the plane configuration, the frequencies range from a maximum d ) m in the far infra-red, down to low values. For an asymmetric ketone all the torsional frequencies are active, while for a symmetric ketone only half of them are active. However, the absorption intensity for frequencies near w m is expected to be very weak. In the solid state, the high and medium torsional frequencies are hardly affected by intermolecular interaction. In this region, therefore, the frequencies calculated for isolated molecules should be approximately correct. The low torsional frequencies, on the other hand, are strongly affected by intermolecular forces in the solid. This effect is discussed, and the absorption due to rigid libration of the molecules is also considered.

Entropy Elasticity in High Polymers

1967 ◽  
Vol 40 (3) ◽  
pp. 777-785
Author(s):  
Friedrich Linhardt
Keyword(s):  
Present Article ◽  
19Th Century ◽  
Experimental Approach ◽  
Operating Temperature ◽  
Elastic Behavior ◽  
Unusual Property ◽  
Vulcanized Rubber ◽  
Entropy Elasticity ◽  
The 19Th Century ◽  
High Polymers

Abstract Vulcanized rubber has an unusual property, known early in the 19th century, but not understood until 1935: it increases in stiffness with rise in operating temperature. A strip of rubber loaded with a weight and heated does not stretch; on the contrary, it contracts to some extent. Theoretical interpretations of this effect showed deformation of rubber, as well as its softness and high extensibility, to be determined by entropy, among other things. “Entropy elasticity” was looked upon as a peculiarity of rubber. It was thus only logical, when materials were classified as “rubbers” that they should be distinguished from all other materials by using the expression “entropy elastic behavior”. To be sure, one is inclined today to consider entropy elasticity a characteristic of all high polymers, including those not crosslinked. The present article reports an experimental approach to this problem.

Chemical Structure of Vulcanized Rubber

1939 ◽  
Vol 12 (1) ◽  
pp. 43-55
Author(s):  
J. R. Brown ◽  
E. A. Hauser
Keyword(s):  
Chemical Structure ◽  
Empirical Knowledge ◽  
Extensive Investigation ◽  
Practical Application ◽  
True Nature ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Metallic Salts ◽  
Other Substances

Abstract A CENTURY ago, Charles Goodyear in America and Th. Hancock in England found that the properties of crude rubber could be greatly improved by heating it with sulfur. The product resulting was more elastic, more resistant to tear and abrasion, less affected by solvents, and decidedly less thermoplastic. The treatment of rubber to give these desired properties is known generally as vulcanization and must be considered as the basis for the enormous growth of the rubber industry and the extensive use of rubber products in our everyday life. Broadly speaking, vulcanization involves the reaction, in some fashion, of sulfur with rubber. Extensive investigation has revealed other substances, such as benzoyl peroxide or polynitrobenzenes, which can transform rubber into a “vulcanized” condition. Experience has also shown that metallic salts of zinc or lead and especially certain organic compounds called “accelerators” greatly affect the rate of vulcanization, and these are favorably employed in practice. A vast amount of empirical knowledge has been gained which has greatly improved the practical application of vulcanization and the quality of rubber products, but which has failed as yet to reveal a complete picture of the true nature of the process.

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