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

Abstract

Fracture behavior of poly(butylene terephthalate) (PBT) and its rubbertoughened (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, K c , and fracture energy, G c , 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.

Effects of compatibilizers and testing speeds on the mechanical properties of organophilic montmorillonite filled polyamide 6/polypropylene nanocomposites

“…It is interesting to note that the addition of SEBS‐ g ‐MA has effectively toughened the nanocomposites and its toughening effect is more prominent at high testing speed, i.e., 500 mm/min. The better fracture toughness at high testing speed was also reported by Yow et al [29] on rubber‐toughened poly(butylenes terephthalate)/short glass fiber system. Compared to PP‐ g ‐MA, SEBS‐ g ‐MA showed more efficient in improving the fracture toughness of the nanocomposites.…”

“…Table 3). The more extensive fibrillation was also found on rubber‐toughened PBT/short glass fiber system tested at high testing speed [29]. The softer nature of SEBS‐ g ‐MA which can provide a better toughening effect than the relatively higher PP‐ g ‐MA is probably believed to be responsible for the observed trend.…”

Mechanical properties of mica‐filled PBT/ABAS composites

“…Fillers have always played an important role in plastics technology to meet the continued demand for improved materials with higher strength, modulus, thermal, and/or electrical properties and chemical resistance. 4 Significant improvements in physical, mechanical, and frictional properties of PBT by various fillers and reinforcements such as glass fibers, [5][6][7] carbon fibers 8 etc. have been reported.…”

Mechanical and fracture properties of ternary PE/PA6/GF composites

“…To compensate for this some researchers have considered the addition of fibrous reinforcement, resulting in the formation of a ternary composite, i.e. short fiber reinforced blend (SFRB) [4][5][6][7][8][9][10][11][12][13]. The rubber introduced to toughen the matrix is mainly in dispersed form and practically no interaction between the fibers and the rubber particles occurs.…”