Hygrothermal aging and fracture behavior of styrene-acrylonitrile/acrylate based core-shell rubber toughened poly(butylene terephthalate)

Abstract

A study of hygrothermal aging in terms of the kinetics of moisture absorption by poly(butylene terephthalate) (PBT) and styrene-acrylonitrile/acrylate based core-shell rubber (CSR) toughened PBT (PBT-CSR) was undertaken. The diffusion of water into the PBT compounds with various CSR contents was investigated by immersion of specimens in water at temperatures between 30 and 90°C. It was observed that the equilibrium moisture content and the diffusion coefficient of the PBT both increased with increasing CSR content. The fracture behaviors of the PBT and PBT-CSR were investigated. The focus of investigation was on the effect of an internal parameter (rubber content) and external parameters (testing temperature, deformation rates, and hygrothermal aging) on the fracture behavior of these materials. The fracture response of the various materials was evaluated by the fracture toughness and energy measured on static-loaded compact tension specimens. The tensile and fracture behavior of PBT and PBT-CSR was affected by both the internal and external parameters. On its own the CSR impact modifier failed to improve the toughness of PBT at either high testing speed or subambient temperature (Ϫ40°C). Based on the dynamic mechanical analysis study, the CSR is believed to behave as a rigid particulate filler in the PBT that consequently reduces the ductility of the PBT. All the materials tested showed poor retention of the tensile and fracture properties upon exposure to hygrothermal aging at 90°C, and these properties could not be restored by subsequent drying. This was attributed to severe hydrolytic degradation of the PBT that caused permanent damage to the materials. The failure modes of PBT and PBT-CSR were assessed by fractographic studies in a scanning electron microscope.

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

“…In the presence of organoclay, the segmental mobility of the polymer molecules and the plastic deformation process in the form of crazing and shear yielding are very much restricted at high deformation rates. The reduction of toughness of the materials with increasing testing speed was also reported for core‐shell rubber toughened PBT blends [23] and PETG/POM/TPU blends [24]. The increase in K IC value observed in the PA6/PP/4C‐MMT with increasing the testing speed may be attributed to the plasticizing effect caused by high content of organic modifier (octadecylamine) in the commercial organo‐MMT, i.e., 34%.…”

Compatibilization of a poly(butylene terephthalate)/poly(ethylene octene) copolymer blends with different amounts of an epoxy resin

“…Poly(butylene terephthalate) (PBT) is an important engineering thermoplastic because of its good combination of properties,1, 2 such as rigidity, solvent resistance, and high rates of crystallization. The notched impact strength of PBT is very low, but it can be improved by the incorporation of elastomers 3–8. Until recently, the impact strength improvements with unmodified elastomers were moderate, but in the last few years, increases in the impact strength between 10‐ and 20‐fold have been achieved with the addition of functionalized elastomers to produce the so‐called supertough PBTs.…”

Degradation of recycled flame-retardant GFPBT during extrusion: Effect of screw types on the extrudate properties

“…With an increase of single screw shear, fiber pull out can be seen in the fracture. 3 Furthermore, debonding between GF and PBT matrix became a common phenomenon and were clearly visible in the PBT matrix in Figure 3(e) to (h). It was found that the fracture of RPBT-3316-T30 show a brittleness matrix with GFs embedded into the PBT matrix.…”

“…Mohd Ishak et al. 1,3,4 reported that the glass fiber (GF) also provides a function of preventing the PBT matrix from being hydrolyzed. The complex orientation of short GF obstructed the diffusion of absorbed water molecules into the matrix and hence reduced the extent of the hydrolysis of PBT matrix.…”