ポリプロピレンの紫外線劣化と防止剤の効果

抄録

We previously reported the kinetic studies of the accelerated aging of plastic films (polystyrene, polyvinyl chloride and polypropylene) in ultraviolet rays. But in case of polypropylene no remarkable change of internal structure (measured by the infrared spectrophotometer) was observed because of the inhibitory effects of several additives.
Hereunder presented is the report of kinetic studies of the accelerated aging of polypropylene samples with or without various inhibitors such as ultraviolet absorbers and antioxidants in ultraviolet rays. Particularly, the inhibitory effects of the samples with various inhibitors were investigated from kinetic point of view.
The results from these experiments are as follows:
(1) The mechanism of deterioration of pure polypropylene is autoxidation which is induced by the hydroperoxide. The breakup of polymer chain frequently accompanies with the formation of carbonyl groups (ketonic and aldehydic types) and consequently the deterioration is accelerated.
(2) Normal-propyl gallate (antioxidant) acts as an effective inhibitor for the deterioration of polypropylene.
(3) Phenyl salicylate, 4-hydroxy benzophenone (ultraviolet absorbers) and β-naphthol (antioxidant) show little inhibitory effects.
(4) In case of the sample with 4-hydroxy benzophenone the accelerative effect is observed rather than the inhibitory effect. It is presumed that this additive acts as an accelerator but on this matter more detailed experiments are required.