The title study has been made comparing the changes in chemical structure, molecular weight. elongation at break and density. The results obtained were as follows : Photodegradation og E /CO copolymers containing 0.9 and 2.4 wt% of CO group was affected by natural environment of the exposed places, especially total solar radiant exposure and total ultraviolet radiant exposure. Ambient temperature also affected the degradation. The overall degradability of the exposed places was as follows :
Haikou > Xining≅Naha> Choshi ≅Shenyang ≅ Qingdao> Zhengzhou ≅ Sapporo
Photodegradation proceeded remarkably within a week, and the elongation at break and the weight average molecular weight (_??_w) decreased to ca. 1 /3 1/6, ca. 1 /3 of its original values, respectively after only a half day exposure. The higher the content of CO group in E/CO was, the faster the photodegradation proceeded. A good relationship was observed between increase in density and decreases in the elongation and _??_w of sample during the exposure.

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On the purpose of obtaining fundamental data necessary for application of water glass as alkali silicate soluble in water for inorganic adhesives and surface coating materials, hardening processes of films of various types of water glass (MO₂ · nSiO₂ ; M = Na, K, Li) coated on steel plates, asbesto scement boards and cardboards were examined under controlled constant condition (20 °C, 60 % R. H.) by reflection-absorption type infrared spectroscopy. Water resistance of various types of films hardened at high temperatures were examined by the change with time of the weight loss under immersion in 50 °C hot water and the change with time of the concentration of Na ⁺ ions solved in hot water by flame photospectroscopy. It was found that hardened films of water glass are assinged as the most fundamental inorganic polymers having siloxane molecular structures, and that they deteriorate in water by depolymeriazation process. The weight loss of fims in immersion in 50 °C obeys the parabolic law concerning time involving a constant term, which shows a certain induction period before the weight loss occurs. Based upon consideration and comprehension of these experimental results, theoretical dynamic analysis are carried out on the deterioration mechanisms, and the parabolic law concerning time involving a constant term is derived.

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