射出接合における接合メカニズムの解明
Study on Welding Mechanism of Injection Welding Process
山口 進
Yamaguchi, Susumu
DRI (Die Rotary Injection) is a new injection molding method that can fabricate tubular products by the conventional injection molding process. The process of making tubular products by this method is as follows.
1. Fabricate a pair of half products.
2. Open the mold. (a half product is kept in the mold)
3. Rotate a part of the mold to oppose each half product.
4. Inject a resin in the gap between the half products.
The most important step in this process is to ensure the reliability of the welding.
In this paper, the welding mechanism, material properties and injection conditions for high welding strength were investigated. The possibility of welding with different materials was also discussed.
The results showed that the surface of the primary resin was melted by the molten secondary resin. The requirements for high welding strength were concluded as follows.
1. A primary resin should be compatible with a secondary resin.
2. The molding temperature of a secondary resin should be higher than that of a primary resin.
3. A secondary resin should be molded at high temperature and high injection speed.
4. In the case of crystalline polymers, it is necessary that the melting latent heat should be lower than the crystallization latent heat.
Key words: DRI process / Welding mechanism / Welding strength / Molding conditions / Latent heat