Weathering of Rubber

The product of this reaction, ozone, is a pollutant in the lower atmosphere. Ozone is an eye and lung irritant and also accelerates the weathering of rubber products. Write Lewis structures for each of the reactants and products in the preceding reactions. 

M. Tahan, Weathering of Plastics and Rubber, International Symposium of the Institute of Electrical Engineers, Eondon, June 1976, Chamelon Press, Ltd., London, 1976, p. A2.1. 

The first move in this direction was to improve the weatherability of impact-resistant polystyrene. Because polybutadiene, the most widely used rubber in impact-resistant polystyrene, is unsaturated, it is sensitive to photooxidation, and impact-resistant polystyrene is therefore not suitable for outdoor applications. A saturated rubber might be able to help here. In the ABS sector this has been successfully tried out with acrylate rubber (77) and EPDM (78, 79), and the latter has also been used in impact-resistant polystyrene (80, 81) This development has elicited satisfactory responses only in certain areas and more work still has to be done. For instance, attempts have been made to improve resistance to weathering by using silicone rubber (82 ). This approach is effective, but economic factors still stand in its way. Further impetus may also be expected from stabilizer research. Hindered secondary amines (83), to which considerable attention has recently been paid, are a first step in this direction. 

The type of rubber chosen depends on the desired mechanical properties and on the end use. If, for example, excellent outdoor weatherability is required, the use if saturated rubbers as elastomer phase is possible. 

Rubber becomes brittle in cold weather and tacky in hot weather, and it is odorous and perishable. It also has very low tensile strength and low resistance to abrasion. One of the major advances in the improvement of rubber was in the discovery by Charles Macintosh in Scotland in 1820 that coal-tar naphtha is a cheap and effective solvent for rubber. He placed a solution of rubber and naphtha between two fabrics, and in so doing he covered up the sticky or brittle surfaces that had been common in earlier single-texture garments treated with rubber. Macintosh patented the process in 1823. These double-textured waterproof cloaks, which were first introduced to the public in 1824, have been known ever since as mackintoshes. 

Brown R P, Butler T, Hawley S W. Ageing of Rubber, Accelerated Weathering and Ozone Test Results, Rapra Technology Ltd, Shawbury, 2001. 

Ultrahigh-frequency (UHF) energy may be used for preheating and precuring rubber compounds for continuous vulcanization (CV) of rubber, containing carbon black, for such applications as weather stripping, tubing, hose, and. in some instances, tire tread compounds. 

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. 

Early uses of rubber mostly involved the weather-proofing of fabric or leather. This must have been frustrating, since these coatings melted in hot sunlight. Charles Macintosh was a Scottish chemist who found that by combining rubber with naphtha, he got a more stable compound that would not melt if it got warm. Clothing made from fabric coated with this compound was called a Macintosh. 

Amount of Rubber. Generally the impact strength of rubber-modified plastics increases with an increase in rubber content. Although the impact improves, it is usually at the sacrifice of other properties such as strength, modulus, heat distortion, weather resistance, and creep. 

To obtain better outdoor weatherability, polybutadiene rubber is frequently replaced as the substrate in impact polystyrene and ABS by EPDM, EVA (19). or polybutyl acrylate. Grafting of styrene. 

Other studies of interest on rubbers include weathering and photolysis in the far ultraviolet." The resistance of rubbers to ultraviolet attack has been found to decrease in the order neoprene > polybutadiene > polychloroprene." ... 

Formulation E2-7249 is excellent for use in protecting battery terminals from oxidation. It can also be used to Lubricate and protect rubber weather stripping and grommets on windows, doors, car hoods, and trunk lids. This formulation will also prevent the sticking of rubber to metals, prolong the life of rubber parts, and eliminate miscellaneous squeaks. 

SMA copolymers and terpolymers have also been used for blending with PVC to improve the heat distortion temperature and processability of PVC. These blends also contain a rubbery component for impact modification that is usually a high rubber ABS or a polymethyl methacrylate grafted styrene-butadiene rubber (MBS). For improved weatherability, acrylic rubber modified PVC has been used for blending with SMA copolymers and terpolymers (Table 15.4). The market for SMA/PVC blends is still relatively low in volume with only a few applications such as in business machine housings as a low cost replacement for flame retarded ABS. 

EXPOSURE ROUTES mainly by burning coal and fly ash inhalation adsorption into digestive tract from drinking water locally grown food weathering of rocks volcanic eruptions incineration of rubber tires, paper, and municipal waste ingestion... 

The original habitat of the rubber tree in the Amazon valley is situated within 5° latitude and at altitudes less than 200 m. Naturally, the trees evolved in this environment prefer warm and humid weather [9]. The climatic conditions suitable for optimum growth of rubber trees include an annual rainfall of not less than 2000 mm, evenly distributed without any marked dry spell, a maximum temperature of 29-34°C and a minimum of 20°C or more, high atmospheric humidity of around 80% with moderate wind, bright sunshine amounting to about 2000 hours per year at the rate of six hours per day throughout the year [10]. Rubber needs a well-drained, fairly deep, loamy soil with a pH value of 4.5-6.0. South East Asia is particularly suitable for rubber cultivation as are countries in West Africa. Although not ideally suited, rubber is now successfully cultivated even up to latitudes of 25° in countries such as India and China. 

R.P. Brown, T. Butler and S.W. Hawley, Ageing of Rubber—Accelerated Weathering and Ozone Test Results, Rapra Technology Limited, 2001. 

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