Thermomechanical studies on natural rubber in torsion and simple extension
Journal of the Chemical Society Faraday Transactions 1 Physical Chemistry in Condensed Phases (1975)
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Thermomechanical heat of deformation studies have been made on crosslinked natural rubber using a Calvet microcalorimeter. Using the Gaussian statistical theory of elasticity to correct for volume changes, torsional experiments gave a value for the relative energy contribution to the retractive force of 0.202± 0.017(=Me/M); simple extension experiments gave 0.19 ± 0.02 (=fe/f). When the data from simple extension experiments were corrected using two empirical dilation equations, values for fe/f of 0.13 ± 0.02 and 0.14 ± 0.02 were obtained. An assessment was made of the various routes available for studying the energetics of rubber deformation.Keywords:
Rubber elasticity
고무 조성비가 다른 카본블랙으로 보강된 고무 배합물의 가황 특성을 연구하였다. 한 가지 고무로 이루어진 고무 배합물, 두 가지 고무로 이루어진 고무 배합물, 그리고 세 가지 고무로 이루어진 고무 배합물을 실험 대상으로 삼았다. NR/BR과 SBR/BR 배합물 중에서 BR의 함량이 높은 것의 델타토크는 단일 고무 배합물의 경우보다 높다. 삼중 고무 배합물의 델타 토크의 경우에는 세가지 고무의 함량비가 유사할수록 델타 토크가 낮아졌다. 스코치 시간과 적정 가황 시간은 NR이 증가할수록 빨라졌고 SBR이 증가할수록 느려졌다. 가황 속도는 SBR 함량이 증가할수록 느려졌다. 가교 역전(reversion) 현상은 SBR 함량이 증가할수록 감소하였다. 【Cure characteristics of carbon black-filled rubber compounds with different rubber composition were studied using a rheometer. The carbon black-filled rubber compounds with single, binary, and ternary rubber compositions of natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR) were used. Delta-torques of the NR/BR- and SBR/BR-based compounds with a high BR content were higher than those of the single rubber-based compounds. For ternary rubber-based compounds, the delta-torques of the compounds were lower when the difference in the rubber content ratios was small than when it was big. Scorch and optimum cure times of the rubber compounds became shorter by increasing the content of NR in the compounds while those became longer by increasing the SBR content. Cure rates of the rubber compounds increased with a decrease of the SBR content in the rubber compounds. Reversion ratios decreased with an increase of the SBR content in the rubber compounds.】
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This chapter contains sections titled: Introduction Rubber Yielding Plants History Plantation Rubber Rubber Cultivation Biosynthesis of Rubber Chemistry of Latex Primary Processing Current Global Status of Production and Consumption Properties of NR Blends of Natural Rubber Modified Forms of Natural Rubber Introduction to the Manufacture of Rubber Products Applications of Natural Rubber Natural Rubber, a Green Commodity Conclusions
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Abstract The pyrolysis products of sodium rubber have been compared with those of natural rubber. They indicate that sodium rubber is isomeric with natural rubber in the positioning of its methyl groups, and that the double bond of sodium rubber differs from the true ethylenic bond of natural rubber. In the latter respect sodium rubber closely resembles overvulcanized rubber.
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Non-Gaussian theory for rubber elasticity has been developed using the distribution function which was proposed for the excluded volume problem. An equation of state which is based on a very simple model yields remarkably good results when the non-Gaussian parameters are adjusted. A distribution function for network study has been suggested. The computed simple shear-strain curve also closely agrees with that of the experimental curve predicting the relationship to be nonlinear. The equations for swelling phenomenon have been derived using the non-Gaussian network concept.
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Abstract With continued progress in technology, highly elastic products have come to be of great importance at the present time. Whereas in earlier years rubber was the only product which could be classed in this category, in the last few years many new products with properties resembling those of rubber have been added to the list. This is to a great extent due to the fact that chemical research has given a better insight into the parent substance of rubber and the structural nature of rubber itself. According to these researches, rubber is representative of a group of highly polymeric, organic natural substances, whose long molecules are composed of small structural units in uninterrupted repetition. By reproducing artificially the relations existing in the structure of the rubber molecule, it has been possible by chemical synthesis to prepare highly elastic substances from allied substances or from substances which polymerize in an analogous way. But in spite of this success, chemical investigations have not yet reached a point where it is possible to explain the mechanism of elasticity, for actually elastic phenomena do not depend on chemical changes ; an explanation is rather to be sought in changes which take place in the relative positions and forms of the rubber molecules.
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Abstract The morphology of natural rubber was observed by transmission electron microscopy. Nanomatrix of non‐rubber components such as proteins and phospholipids was found to be inherently formed in natural rubber, in which natural rubber particles of about 0.5 µm in average diameter were dispersed. The nanomatrix of non‐rubber components disappeared after deproteinization of natural rubber with urea. Stress at break of serum rubber was higher than that of deproteinized natural rubber, while strain at break did not change. When the amount of the non‐rubber components increased, the stress at break became significantly dependent upon the amount of non‐rubber components. Viscoelastic properties of natural rubber were also dependent upon the nanomatrix of non‐rubber components. Storage modulus of natural rubber increased significantly, when the amount of the non‐rubber components increased. Copyright © 2010 John Wiley & Sons, Ltd.
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