Fracture behavior of rubber-modified injection molded poly(butylene terephthalate) with and without short glass fiber reinforcement

• Published in: Journal of applied polymer science Vol. 84; no. 6; pp. 1233 - 1244
• Main Authors: Yow, B. N., Ishiaku, U. S., Ishak, Z. A. Mohd, Karger-Kocsis, J.
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 09.05.2002; Wiley
• Subjects: Applied sciences; Composites; Exact sciences and technology; fiber-reinforced thermoplastics; Forms of application and semi-finished materials; fracture; poly(butylene terephthalate); Polymer industry, paints, wood; rubber-toughened; Technology of polymers; Terpolymer; Short fiber; Polymer blends; Volume fraction; Stress strain relation; Fiber reinforced material; Mechanical properties; Experimental study; Composite material; Fracture toughness; Bending strength; Glycidyl methacrylate copolymer; Butene terephthalate polymer; Ethylene copolymer; Acrylate copolymer; Methacrylate copolymer; Glass fiber; Fracture mode; Strain rate
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.10446

Fracture behavior of poly(butylene terephthalate) (PBT) and its rubber‐toughened (RT) 10 wt %) grades; ethylene‐co‐glycidyl methacrylate‐co‐methacrylate terpolymer‐toughened poly(butylene terephthalate) PBT/AX8900 (90/10), and Paraloid acrylic‐based rubber‐toughened poly(butylene terephthalate) PBT/EX2314 (90/10) was investigated using the fracture mechanics approach. The effects of controlling parameters such as type of impact modifier and deformation rate on fracture behavior of PBT and RT‐PBT were investigated. Fracture tests were carried out on notched compact tension (CT) specimens. Fracture toughness, Kc, and fracture energy, Gc, of PBT decreased as the test speed increased from 1 to 500 mm/min. An opposite trend was observed in PBT/AX8900 and PBT/EXL2314. The fracture properties of 30 wt % short glass fiber‐reinforced PBT (SGF‐PBT) and 10 wt % impact‐modified PBT composite (SGF‐RT‐PBT) were also studied. Incorporation of SGF into PBT has profoundly increased the fracture properties both at high and low speed. However, inclusion of 10 wt % of AX8900 into the reinforced PBT (PBT/AX8900/SGF) (60/10/30) adversely affected the fracture properties. EXL2314, on the other hand, showed a different effect, especially at high testing speed. Both types of impact modifiers were able to retain the flexural strength and flexural modulus of PBT. However, PBT/EXL2314 showed a better retention of flexural properties than PBT/AX8900. Incorporation of SGF in the EXL2314‐toughened PBT, i.e., PBT/EXL2314/SGF (60/10/30) also gave a better balance of flexural properties compared to PBT/AX8900/SGF (60/10/30). Both PBT/AX8900 and PBT/EXL2314 showed enhancement of impact strength on the unnotched specimens. The failure modes of CT and impact specimens of PBT, RT‐PBTs, and SGF‐RT‐PBTs were assessed using a scanning electron microscope (SEM). Brittle failure was observed for CT specimens of PBT at high testing speed, while incorporation of the impact modifier AX8900 and EXL2314 resulted in a shift of failure mode from brittle to ductile. SEM micrographs also revealed extensive fiber pull out in SGF‐PBT and SGF‐RT‐PBT. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1233–1244, 2002; DOI 10.1002/app.10446