With the aim of clarifying the effect of a small ethylene incorporation (5.3 mol%) on the thermal stability of one PP chain and photo stability of PP solid, homo isotactic PP (hPP) and ethylene-propylene random copolymer (rPP) were studied in respect of thermal and photo degradation. The thermal dega dation was performed under a dilute solution of trichlorobenzene. The decreasing in rate of molecular weight of the degraded rPP was slower than that of the degraded hPP, suggesting that the stability of one PP chain was improved by the ethylene incorporation. Whereas, the photo degradation of rPP was performed by a film sample having the same crystallinity (56 vol/%) as the hPP's. The formation rate of hydroperoxide and carbonyl groups in degraded rPP film increased against irradiation time as well as those of degraded hPP. However, those in the irradiated rPP were almost constant over 96 h. Also the molecular weight of irradiated rPP did not change over this time. This behavior implied that the degradation reaction cycle was stopped. It was found that the ethylene incorporation caused the decreasing in rate and the changing pathway of PP degradation reaction.

View full abstract

Photoinduced formation of cellulose peroxides was examined at 30°C under air atmosphere. Filter paper with thickness of 0.2 mm was used as a cellulose sample. When the cellulose sample, which was pretreated with acetone solution of photoinitiators such as benzophenone and benzoin ethyl ether, was irradiated with light longer than 300 nm in water, peroxides were formed on cellulose part, while hydrogen peroxide was yielded in water part. Formation mechanism of the both peroxides, in which cellulose peroxide of α-hydroxy hydroperoxide type is formed, was proposed. The irradiated cellulose sample was subjected to measurement of chemiluminescence (CL) at 100°C under nitrogen atmosphere. It was found that the irradiated sample exhibites CL and a higher CL intensity is afforded for the irradiated sample with a higher peroxide content. Aldehyde groups were introduced into cellulose sample by oxidation with periodic acid. The resultant oxidized cellulose samples were subjected to the oxidation with hydrogen peroxide in the presence of methanesulfonic acid to prepare cellulose peroxide of α-hydroxy hydroperoxide type. It was observed that the cellulose peroxides exhibite CL curve similar to that of the irradiated sample and the CL intensity increases with increasing the peroxide content.

View full abstract