It was investigated that photodegradation of diene polymer in the presence of sensitizer and ketones. Shredded diene polymers were dipped in a small quantity of ketones, with addition of a sensitizer, and ultraviolet irradiation was applied for 6h. Significant decreases in the molecular weights of diene polymers were confirmed. In particular, anthraquinone reduced the molecular weight of cis-1,4-polyisoprene sample to around 3,500. This reduction was ascribed to the small amount of energy required for first excitation of the polycyclic aromatic quinone, which allowed this substance to easily change into an active species. Degradation product had highly enhanced solubility, being soluble in alcohol, ketone, and many other organic solvents. From the structure analysis results of the degradation product, it is suggested that the reaction that reduced the molecular weight is ascribable to auto-oxidation reaction.
General methods of the measurement of the deteriorated conditions of plastics are 1) : the characterization of the oxidized and decomposed structure of ones by infrared spectroscopy, 2) : the observation of the structural changes of ones by electron microscopy, 3) : the analyses of the additive and the decomposed compounds of ones by the composition analysis, and 4) : the measurement of properties of ones. These methods are qualitative, however, are not quantitative. In order to quantify the deteriorated conditions of plastics, we noted the infrared emission, which is utilized in the evaluation of far infrared effect of plastics. The determination of relationship between the deteriorated conditions and infrared emissivity of plastics was tried. Samples of polyvinylchloride and styrene / butadiene copolymer containing carbon black were used in accelerated aging test. The infrared emissivity of the deteriorated polymers was measured. The deteriorated conditions of plastics were found to be correlated with infrared emissivity of plastics.
In the industrial equipments for beverage and food, the functional parts made by austenitic stainless steel are widely used in combination with other types of materials in order to fulfill the requirement of resistance to corrosion. The pitting and/or crevice corrosions are tending to observed when the parts are contacted with the corrosible beverage and food. The crevice corrosion was also frequently observed when the parts are attached with the gaskets in the industrial equipments. Moreover, seriousness of crevice corrosion was changed depending on the kinds of materials of gasket in the industrial plants. However, there has been few report studied about the effect of the rubber materials of gasket on the crevice corrosion of stainless steel. Thus in the present report, the relationship between the crevice corrosion of stainless steel and the rubber materials used for gasket was investigated under the influence of aqueous acids which are included in the refreshing beverages, because most of the refreshing beverage are acidic. Since ascorbic acid has been widely used as a sour agent of refreshing beverage, the present report focused on the corrosion behavior of this type of non-oxidative acids.