The effects of γ irradiation on toughening mechanisms in rubber‐modified polymers

Abstract

SYNOPSISHigh-impact polystyrene (HIPS) and acrylonitrile butadiene styrene ( ABS ) have been subject to y irradiation in doses up to 20 and 12.5 Mrad, respectively. During tensile testing, both longitudinal extension and lateral contraction were simultaneously measured, allowing determination of volume strain, and from this to identify the relative contributions of crazing and shear yielding to the tensile deformation process. Both materials show a doserelated increase in the strain at which crazing commences, though the relative change with dose in HIPS is much greater than in ABS. However, the contribution of crazing to total deformation remains high in HIPS when compared with ABS. Shear yielding is an important deformation process in ABS and the results indicate that this is relatively unaffected by irradiation, whereas the ability to craze is severely limited. The reduced ability to craze observed in both materials is considered to be the result of crosslinking in the rubbery phase. The notched impact strength of ABS is particularly sensitive to irradiation and again reflects the reduced ability to craze observed in the tensile testing. ABS fracture surfaces examined by scanning electron microscopy display reduced ductility in the irradiated material.

Microstructure, deformation, and fracture behavior of commercial ABS resins

“…Our results are consistent with the suggestions of Birkinshaw et al 36 and Bucknall and coworkers33 who proposed that the two toughening mechanisms in ABS have different rates of response. At higher rates of strain and at relatively high stresses, crazing and crack fibrillation are more important; and a t the lower strain rates encountered in the tensile tests, shear yielding can also play an effective toughening role.…”

Morphological, mechanical properties, and fracture behavior of bulk‐made ABS resins toughened by high‐cis polybutadiene rubber

“…In the case of small-sized particles, crazes initiate from the equator of the particle and lie in a plane perpendicular to the applied stress axis, and the ''activity'' of large particles is far higher than that of the small ones [42]. The results are also in good agreement with the previous investigations [43,44]. It is shown that the different deformation rates could mainly produce two toughening mechanisms in ABS.…”

Cavitation of rubber particles in high‐impact polystyrene: Effects of crosslinking by γ‐irradiation

“…Previous studies of the effects of γ‐irradiation on HIPS and PS have been made by Birkinshaw, Buggy, and coworkers,19, 20 who measured changes in molecular weight, tensile stress–strain behavior, and impact strength. They showed that only minor changes occur in PS, whereas the properties of HIPS alter dramatically.…”