Rubber materials degradation/aging

Without antioxidants virtually all rubber products, including those made from modem synthetic rubbers, undergo unacceptable performance degradation upon aging [195]. Various aromatic materials and particularly phenols have proven to... 

TG-DTA Characterisation of carbon black [149], flammability evaluation [64], polymer degradation studies [65], ageing studies [70-72], product control [77, 81], combustion performance [83], safety evaluation [83], antioxidation activity [68], pyrolysis of rubbers [82], thermal stability [67, 69, 76, 77], interfacial junctions in viscoelastic composites [78], weathering [72], vulcanisation [73], oxidative behaviour [79], materials evaluation [80], failure analyses [81],... 

Functional properties and stability of rubbery materials Chapters 1, 3, 4, 7, 12 and 13, give examples of applications of spectroscopic techniques for the characterisation of thermal stability and degradation, kinetics of thermal decomposition, ageing, oxidation and weathering, self-diffusion of small molecules in rubbery materials, adhesion of rubbers to metals, fluid adsorption and swelling. 

The polyacrylate and ethylene-acrylic copolymers and one of the ethylene-propylene terpolymers (Nordel) were the best of the Intermediate temperature elastomers. Except for resistance to compression set, these materials were Inferior to the silicones in thermal stability as measured by their retention of tensile properties. The other EPDM compounds and butyl rubber were considerably inferior to the above-mentioned elastomers. It is not expected that the service life of the tested materials will be limited solely by their ability to resist hydrolytic degradation. The only caulking compositions which retained moderate physical integrity on thermal aging were the silicones. 

Liquids can swell rubber, leach out extractible materials, and react chemically to modify or degrade the compound. The results are changes in mass, dimensions, physical properties, and resistance to aging, and each of these is accommodated in the standard test ISO 1817 (BS903, Part A16) and its U.S. equivalent ASTM D471. 

It should be noted that it is the rubber phase which toughens these types of blends and small losses of rubber through process degradation can be expected to yield a material with significally lower impact strength and tensile elongation. Data from a recent aging study of ABS at 710 illustrates this point. Analysis of the rubber content... 

Aging, rubbers n. The process of oxidation and other degradations of rubber or elastomeric materials. 

First, the stability of these polymer materials is very important for their practical use and processing. Assessment of surface chemical modification of rubber after aging treatment is, by example, primordial for pneumatic manufacturing. Similar to conventional methods, LA-MS is allowed to evaluate and follow the oxidation effects on model polymers such as polybutadiene (PB), polystyrene (PS), and styrene butadiene rubber (SBR) by both detection and identification of the degradation products. The thermooxidative stability of SBR has been then investigated. 

This chapter deals with ageing processes of HDPE geomembranes, with their durability and the resulting service lives. Implicitly, statements on material resistance and functional reserves are always implied. Explicit statements about resistances of HDPE geomembranes to individual influences (chemical resistance, resistance to thermo-oxidative degradation, resistance to stress crack, resistance to weathering, biological resistance) have been made in Chap. 3 in connection with the respective resistance test methods. A concise summary of durability and resistance of plastics and rubber is published by (Dolezel 1978). 

A number of impurities found in compounding ingredients are known to influence the ageing behaviour of rubbers, especially NR. High iron oxide impurity levels, and some forms of copper and manganese impurities are known to be the cause of rapid oxidative degradation. There is little literature available that relates either the active form of impurities or that identifies the level of impurities found in fillers to specific effects on polymer degradation. Nonetheless, it is occasionally an area of concern. It should be noted that every source of filler will be different in its level and type of impurities, so each material must be considered in isolation. Specification values may not be an indicator of performance in polymer. 

In addition to influences of mechanical load on degradation in polymer chains, unexpected degradation can occur due to the initiation of specific micromechanical processes and mechanisms. Such mechanisms (shear flow, craze formation, cavitation, etc.) are initiated in particular in inhomogeneous polymers (blends, filled and reinforced plastics, etc.) by inhomogeneous stress distributions caused by external mechanical loads. Typical examples for such physical aging processes are ABS materials with an unfavorable size distribution of rubber particles [72],... 

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