Degradation of Polymers

1962 ◽  
Vol 35 (5) ◽  
pp. 1157-1221 ◽  
Author(s):  
Leo A. Wall ◽  
Joseph H. Flynn
Keyword(s):  
Ionizing Radiation ◽  
Thermal Degradation ◽  
Natural Rubber ◽  
Ultraviolet Light ◽  
Recent Literature ◽  
Chain Scission ◽  
Experimental Results ◽  
Gel Formation ◽  
Vinyl Polymers ◽  
Kinetic Mechanisms

Abstract Recent literature pertaining to both the theoretical aspects and experimental results of the degradation of polymers by heat and radiation is reviewed and critically evaluated. Theories of random and chain thermal degradation of vinyl polymers and co-polymers are reviewed. The degradation of polymethacrylates, polyacrylates, poly-α-methylstyrene, polyolefins, polystyrene, other vinyl polymers, cellulose, polyesters, polyamides, dienes, natural rubber, and copolymers are discussed in the light of these theories. The thermodynamics and energetics of the degradation of these polymers is also reviewed. Chain scission, crosslinking, and gel formation and the kinetic mechanisms of these processes which take place during degradation of polymers by ionizing radiation and ultraviolet light are included. Degradative, rather than synthetic, effects are emphasized in the discussion.

Multi‐scale simulations of the thermal degradation of thin wooden plates: Evaluation of two kinetic mechanisms

2021 ◽  
Author(s):  
Guillaume Gerandi ◽  
Virginie Tihay‐Felicelli ◽  
Frederic Morandini ◽  
Paul‐Antoine Santoni
Keyword(s):  
Thermal Degradation ◽  
Multi Scale ◽  
Kinetic Mechanisms

Relation between Molecular Weights and Physical Properties of Rubber Fractions

1941 ◽  
Vol 14 (3) ◽  
pp. 580-589 ◽  
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
High Molecular Weight ◽  
Elastic Properties ◽  
Elastic Material ◽  
Experimental Results ◽  
Molecular Weights ◽  
High Elasticity ◽  
Latex Rubber

Abstract As high elasticity is a property possessed only by substances of high molecular weight, it is of interest to enquire into the relation between the elastic properties of a highly elastic material such as rubber and its molecular weight. An investigation on these lines has been made possible through the work of Bloomfield and Farmer, who have succeeded in separating natural rubber into fractions having different average molecular weights. The more important physical properties of these fractions have been examined with the object of determining which of the properties are dependent on molecular weight and which are not. Fairly extensive observations were made on the fractions from latex rubber referred to as Nos. 2, 3 and 4 by Bloomfield and Farmer, and some less extensive observations were carried out on the less oxygenated portion of fraction No. 1 obtained from crepe rubber (called hereafter 1b) . Before considering these experimental results, and their relation to the molecular weights of the fractions, it will be necessary to refer briefly to the methods used for the molecular-weight determinations, and to discuss the significance of the figures obtained.

Tire Black Sidewall Surface Discoloration and Non-Staining Technology: A Review

1998 ◽  
Vol 71 (3) ◽  
pp. 590-618 ◽  
Author(s):  
Walter H. Waddell
Keyword(s):  
Fatigue Life ◽  
Natural Rubber ◽  
Outer Surface ◽  
Chain Scission ◽  
Butadiene Rubber ◽  
Ethylene Propylene ◽  
Polymer Decomposition ◽  
Sidewall Surface

Abstract The tire black sidewall is the outer surface that protects the casing against weathering. It is formulated for resistance to weathering, ozone aging, abrasion, tearing and cracking, and for good fatigue life by using blends of natural rubber and cis-butadiene rubber. Protection against ozone aging is of particular interest since reaction with these olefinically unsaturated elastomers results in polymer decomposition via chain scission. Use of N-alkyl, N′-aryl-para-phenylenediamine antiozonants has proved most effective. However, their use also results in a surface discoloration, and thus they can be used in only limited amounts when tire appearance is also an important factor. A review is made of the literature describing this surface discoloration problem and approaches to formulate a black sidewall compound to eliminate this surface discoloration upon exposure to ozone. Methods include use of non-staining antiozonants, and uses of elastomers with saturated backbones such as ethylene-propylene-diene terpolymers, halobutyl rubbers and brominated-isobutylene- co-para-methylstyrene.

Cis-Trans Isomerization of Natural Rubber under the Influence of Organo-Aluminum Compounds and Titanium Tetrachloride

1959 ◽  
Vol 32 (4) ◽  
pp. 1036-1038 ◽  
Author(s):  
B. A. Dolgoplosk ◽  
E. N. Kropacheva ◽  
K. V. Nelson
Keyword(s):  
Natural Rubber ◽  
Ultraviolet Light ◽  
Titanium Tetrachloride ◽  
Chemical Properties ◽  
Regular Structure ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Aluminum Compounds ◽  
Physical And Chemical ◽  
First Time

Abstract Ziegler catalysts have become of prime importance for synthesis of polymers with regular structure, particularly cis-polyisoprene. The disruption of the structure of the chain by the formation of trans units was, until now, connected only with the influence of the physical and chemical properties of the catalyst on the nature of the addition of the diene monomers during the polymerization process. In the present work it is shown that destruction of regularity of structure can be caused by isomerization of cis units in complete polymer chains into trans units under the influence of the compounds used for initiating the polymerization process. Attempts to isomerize natural rubber by means of ultraviolet light and iodine did not give the expected effect. Ferri established for the first time that under the influence of zinc chloride and titanium tetrachloride natural rubber undergoes changes accompanied by disappearence of crystallization on stretching as shown by x-ray structure analysis. On the basis of these results the authors presumed that under the influence of these agents isomerization of cis units to trans units occurs in the natural rubber chain. The isomerization of cis-1,4 units to trans units in polybutadiene by means of ultraviolet light in the presence of organic bromine or sulfur compounds was first accomplished and proved by Golub. The formation of trans units in natural rubber under similar conditions was not observed. The study of the isomerizing effect of TiCl4 and organo-aluminum compounds was conducted by us on solutions of milled natural rubber (NK) in benzene in sealed glass ampoules. The benzene used was dried and distilled over sodium. All work was conducted in an atmosphere of dry argon. Unsaturation and microstructure of the chain was determined on each sample. The study of microstructure of polyisoprenes was carried out by means of infrared spectra, the relative content of the different configurations of the polymer chain being determined by the absorption in the 800–1000 cm−1 region. The method previously developed by one of us was used for this purpose.

Mastication of Elastomers II. Cold Mastication of Natural Rubber

1963 ◽  
Vol 36 (1) ◽  
pp. 102-110 ◽  
Author(s):  
G. M. Bristow
Keyword(s):  
Low Temperature ◽  
Natural Rubber ◽  
Thermal Oxidation ◽  
Chain Scission ◽  
Oxidative Process ◽  
Radical Acceptor

Abstract The cold mastication of natural rubber in oxygen is shown to proceed rather more rapidly than that in air. Reasons for this difference are considered. Mastication under these conditions is considered as a low temperature oxidative process and consistent with this the subsequent reactions of RO2 radicals produced by mechanical shear are shown to lead to some additional chain scission. The thermal oxidation of rubber masticated in oxygen is rather more rapid than that of rubber masticated in nitrogen in the presence of a radical acceptor.

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