Water-Assisted Injection Molding of PBT(Poly-butylene terephthalate)

• Main Authors: Ming-Ren,Lin, 林銘仁
• Other Authors: Shih-Jung,Liu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/39994033345027390909

碩士 === 長庚大學 === 機械工程研究所 === 93 === Abstract This report was to experimentally study the water assisted injection molding of poly-butylene-terephthalate (PBT) composites. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system, which included a water pump, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The materials used included a virgin PBT and a 15% glass fiber filled PBT composite. A plate cavity with a rib across the center was used. Various processing variables were studied in terms of their influence on the length of water penetrations in molded parts. Mechanical property tests were performed on the water assisted injection molded parts. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) have also been employed to identify the material and structural parameters. In addition, a comparison has been made between water assisted and gas assisted injection molded parts. It was found that the melt fill pressure, melt temperature, and short shot size were the dominant parameters affecting the water penetration behavior. Material at the mold-side exhibited higher crystallinity than that at the water-side. Parts molded by gas also showed higher crystallinity than those molded by water. In addition, the glass fibers near the surface of molded parts were found oriented mostly in the flow direction, and oriented substantially perpendicular to the flow direction with increasing distance from the skin surface.