Sandwich injection molding of thermotropic copolyesters and filled polyester

✍ Scribed by D. G. Baird; G. L. Wilkes

• Publisher: Society for Plastic Engineers
• Year: 1983
• Tongue: English
• Weight: 446 KB
• Volume: 23
• Category: Article
• ISSN: 0032-3888
• DOI: 10.1002/pen.760231108

✦ Synopsis

Abstract

Mold filling studies have shown that thermotropic liquid crystalline copolyesters of p‐hydroxybenzoicacid (PHB) and polyethyleneterephthalate (PET) fill by an advancing front mechanism similar to flexible chain polymers. The structure and orientation developed during filling as determined on solid specimens by an etching method, X‐ray diffraction, and shrinkage study on thin microtomed samples appear to be most pronounced at the surface. Based on this information copolymers of 60 and 80 mole percent PHB/PET were co‐injection molded with filled PET under various processing conditions. Because of the low viscosity of the copolyesters, they readily coated filled PET under most processing conditions to give a sheath/core structure. The bending modulus of co‐injection molded bars with as little as 35 percent PHB/PET was as high as the sample consisting of 100 percent liquid crystalline copolyester. Electron micrographs of fracture surfaces revealed excellent adhesion between the two polymers.