射出圧縮成形による結品化制御に関する研究第1報 ポリプロピレンの結晶化制御
Crystallization Control Using Injection Compression MoldingPart I Crystallization Control of Polypropylene
鎌田 悟・工藤 素・守時 一・小山清人
Kamata, Satoru / Kudo, Makoto / Moritoki, Hitoshi / Koyama, Kiyohito
It is known that the crystallization behavior of crystalline polymers are influenced by the pressure during the solidification process. Therefore, it should be possible to control the crystallinity by changing the loading pressure. In general injection molding, the holding pressure does not play a role in controlling the pressure in the cavity after gate-freezing. Therefore, it is impossible to control the pressure during the entire crystallization process, whereas the injection compression molding is able to control the cavity pressure throughout the compression process even after gate-freezing. In order to investigate the possibility of crystallinity control in the crystalline polymer molded by the injection compression molding, we have examined experimentally about the relationships among crystallinity, crystal structure and molding conditions for polypropylene. The results obtained were as follows : (1) Crystallinity of the molded parts decreased with increasing the compression pressure, (2) It was possible to control the crystallinity distribution in the thickness direction by changing the compression pressure during the process of polymer solidification. Controlling crystallinity is useful for an improvement in quality of the molded parts, and it should be possible to produce new molded parts with special characteristic such as functionally graded materials.
Key words: Injection compression molding / Crystallization control / Crystallinity / Density / Polypropylene