Abstract
In the evaluation of plastic materials at their deterioration, it is regretable that there have been but poor discussions made so far concerning the correlation between their physical properties and internal structure during their deterioration.
Hereunder is presented the report of kinetic studies made of the accelerated aging of plastic films (polystyrene, polyvinyl chloride and polypropylene) in ultraviolet rays.
The deterioration is evaluated as follows;
(1) By changes of their physical properties (ultimate strength and relative elongation at break) which are measured by the auto-graph, and their activation energy and the entropy of activation are calculated by using the accelerated aging time as the criterion for their kinetic evaluation. The degree of deterioration is evaluated by these two values.
(2) By changes of their internal structure which are measured by the infrared spectrophotometer (NaCl system), and their activation energy and the entropy of activation are calculated by using the changes in percent transmission of each characteristic absorption group during their deterioration.
(3) By the suitable mechanism of their deterioration which is proposed by the infrared absorption method and by using these two values as the measure. The correlation of their physical properties with changes of internal structure is thus evaluated from the kinetic point of view.
