Reactive modification of PBT with applications in low density extrusion foaming

• Published in: Polymer engineering and science Vol. 47; no. 3; pp. 244 - 253
• Main Authors: Jeong, Byeong Joon, Xanthos, Marino
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.03.2007; Wiley Subscription Services; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd
• Subjects: Applied sciences; Cellular; Effects; Exact sciences and technology; Forms of application and semi-finished materials; Molecular weight; Plastic foams; Polyethylene; Polymer industry, paints, wood; Resins; Studies; Technology of polymers; United States; Branching; Branched polymer; Ester polymer; Experimental study; Cellular plastic; Optimization; Structure processing relationship; Chemical modification; Foaming process; Butene terephthalate polymer; Morphology; Epoxide; Addition reaction; Extrusion; Plastics
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.20699

By contrast to polyethylene terephthalate (PET), extrusion foaming of polybutylene terephthalate (PBT) to medium–low densities has been seldom reported in the literature. In this study, a commercial linear PBT resin was reactively modified in a batch mixer to a branched structure with a higher molecular weight (MW) and a broader molecular weight distribution (MWD) as evidenced by rheological analysis. Chain branching was also accomplished by single screw extrusion, where the competing degradation reaction needed to be taken into account. Optimization of the extrusion operational conditions, which also involved the use of suitable consititutive equations, led to the production of a branched resin with viscoelastic characteristics suitable for low density extrusion foaming by injection of physical blowing agents (PBA). The branched product made under the optimized conditions showed good foamability. The effect of pressure drop rate on cell nucleation rate and the effect of the crystallization rate on cell density and cell morphology are examined. POLYM. ENG. SCI., 47:244–253, 2007. © 2007 Society of Plastics Engineers.