Abstract
Followed by I-J Chiang [1], syndiotactic polystyrene (sPS) sheets made with two different cooling rates were examined by X-ray diffraction. Crystalline sPS can be made by air cooling processes, while amorphous sPS made by water quenching from the melt. For air-cooled sPS, the tensile test experiments were performed from 21℃ to 140℃ in air and 80℃ in water. The stress intensity factor experiments were performed from 21℃ to 90℃. For water-cooled sPS, the tensile test experiments were performed from 21℃ to 90℃ in air and 80℃ in water. The stress intensity factor experiments were performed from 21℃ to 70℃. Young’s modulus of water-cooled sPS is larger than air-cooled sPS because molecular weight is higher for water-cooled sPS than for air-cooled sPS. Chevron shape of crack is observed in water-cooled sPS specimen. The brittle-ductile transition temperature of air-cooled sPS and water-cooled sPS are about 75℃. The self-oscillation phenomenon occurs when temperature is higher than 75℃. The rate of extension is 0.014mm/sec. It is caused by heat effect. When temperature is increased, period and wavelength of oscillation are decreased. Stress intensity factor for water-cooled sPS is larger than that for ait-cooled sPS. Nanoindentation test can be obtained reduced modulus and hardness. Young’s modulus of air-cooled sPS and water-cooled sPS measured by nanoindenter are smaller about 8% than measured by tensile test. Because polymeric material will sink and pile-up, hardness measured by nanoindenter is different from microhardness tester about 16 times. Hardness obtained from indentation images is closer to microhardness tester about 35%. The viscosity of irradiated water-cooled sPS with dose range from 128 to 800kGy were obtained. We can find that the structural change was dominated by chain scission for the dose below 300kGy and by cross-linking for dose above 300kGy of water-cooled sPS.