Properties of poly(butylene terephthatlate) polymerized from cyclic oligomers and its composites

• Published in: Polymer (Guilford) Vol. 46; no. 23; pp. 9871 - 9880
• Main Authors: Parton, Hilde, Baets, Joris, Lipnik, Pascale, Goderis, Bart, Devaux, Jacques, Verpoest, Ignaas
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 14-11-2005; Elsevier
• Subjects: Applied sciences; Composites; Crystallinity; Exact sciences and technology; Forms of application and semi-finished materials; Mechanical properties; Polymer industry, paints, wood; Technology of polymers; Mechanical properties; Composites; Crystallinity; Ring opening polymerization; Ester polymer; Fiber reinforced material; Experimental study; Oligomer; Composite material; Melt crystallization; Spherulites; Cyclic polymer; Butene terephthalate polymer; Morphology; Thermal polymerization; Prepolymer; Kinetics; Glass fiber; Isothermal crystallization
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2005.07.082

The high viscosity of thermoplastic matrices hampers fiber impregnation. This problem can be overcome by using low viscous polymeric precursors such as cyclic butylene terephthalate (CBT
® resins), which polymerize to form a thermoplastic matrix. This allows thermoset production techniques, like resin transfer molding (RTM), to be used for the production of textile reinforced thermoplastics. Due to the processing route and more specifically the time–temperature profile, inherent to the RTM process, the crystallites of the matrix consist out of well-defined, thick and well-oriented crystal lamellae. Together with a high overall degree of crystallinity and a low density of tie molecules, these large and perfect crystals cause polymer brittleness. Matrix brittleness lowers the transverse strength of unidirectional composites to below the matrix strength, but leaves the mechanical properties in the fiber direction unaffected. Although not a valid option for the RTM production route, crystallization from a truly random melt and at a sufficiently high cooling rate would substantially improve the ductility.