Injection Blow Molding Technology for Polyethylene Terephthalate

Abstract

Abstract A review of patents and the literature addressing the in ection blow molding (IBM) technology specific to PET bottles and containers is presented. Fabrication and polymer modification issues were cited. It was found that there is no model that includes all factors which enables a complete a priori prediction of in ection blow molded PET container performance, but there are several which cover certain aspects of the preform blowing step. Hot fill capability for PET is currently managed by both the control of crystallinity and container design considerations (i.e., wall profile, ribs, etc.). Depending on the desired result, both processing routes to enhance the level of crystallinity (generically referred to in the industry as heat set technology), and molecular modification to disrupt crystallinity have been patented, some quite recently. A number of patents address technologies that can be used to modify melt elasticity for blow molding. The modification of PET with PEN presents some new challenges due to transesterification during processing and fabrication. Biaxial stretch ratios of 18 are usually required for the blow molding of PET/PEN blends, and maximum filling temperature noticeably decreases only one day after fabrication.