Soaking test with physiological salt and bile solutions was carried out for polylactic acid (PLA), polycaprolacton (PCL), polyglycolic acid (PGA) and their copolymers. Biodegradability was evaluated by measuring mechanical properties and molecular weight of these polymers as a function of soaking time. In homopolymers, PGA degraded very quickly, but other two polymers kept the mechanical strength for more than 100 days. In the copolymer composed of lactic acid and glycolic acid, the degradation rate varied with mole ratio. Generally the degradation rate of copolymers was found to be rapid as compared with hompolymers. The polymers that are useful in the field of bio-science can be prepared from the copolymers of biodegradable components by changing the monomer ratio.
The luminescent value of green tea leaves is different by the different processing methods : that of brown rice tea (genmaicha) is the highest because of the luminescence of brown rice, and followed, in order, by boiled tea (sencha) and roasted tea (hojicha). It was also revealed that the higher the measurement temperature, more the luminescent value increases.
Effect of photocatalyst TiO2 on weatherability of poly (vinyl chloride) sheets was investigated and the following results were obtained. On both artificial light exposure and natural exposure, total transmittance (Tt) of the samples with photocatalyst TiO2 on the surface was higher than that of uncoated one. Parallel transmittance (Tp) of the coated samples was larger than that of uncoated one during the natural exposure. On the artificial light exposure, parallel transmittance of uncoated one was larger than that of the coated samples. On the natural exposure, diffuse transmittance (Td) and Haze value of uncoated one were larger than that of the coated samples. On the artificial light exposure, Td and Haze values of the coated samples were larger than that of uncoated one. These conversely results between the natural and artificial light exposure were probably caused by difference between the experimental conditions of light irradiation and the supply water so on. As mentioned above, it was confirmed that weatherability of sheets increases and the life of sheets becomes longer by means of coating photocatalyst TiO2 on poly (vinyl chloride) sheets.
Photodegradation of Nylon 6 was evaluated by chemiluminescence method comparing with spectroscopic analyses and the following results were obtained. Evaluation of the photo-degradation of Nylon 6 at a very early stage was possible by the chemilumiscence method. While it was difficult by conventional infrared and ultravioletet · visible spectroscopic analyses. Similar results were obtained in the weathered samples. The results apparently indicate that chemiluminescence method is also useful to evaluate photodegradation of Nylon 6 at a very early stage.
The characteristics of combustibility and pyrolysis of polyurethane were compared with other polymeric materials. The usual vertical combustion tests and heat flux measurements were conducted regarding combustibility. Ignitability was also examined and the combustion speed during the vertical combustion test was measured by using a device developed by the authors. From the results of the combustion measurements, it could be seen that in the vertical combustion tests, the ignition time of polyurethane was faster than other polymeric materials but the combustion time was shorter because the flame dripped off immediately, therefore the gross calorific value was low. In the heat flux measurements, the calorific value increased because the melted sample further resolved secondarily to become a gas and contributed to the combustion. From the observation of ignition, it could be inferred that although PU was somewhat harder to ignite than PP, it can be categorized as an easily ignitable material. The weight loss temperature of PU was over 100°C lower than other polymeric materials in terms of pyrolyis, and a large amount of MDI, which is a raw material of PU, was included in its resolution products. Ether and products of ester origin were also generated.