Synthesis of sub‐micrometer core–shell rubber particles with 1,2‐azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditions

Abstract

BACKGROUND: Sub‐micrometer core‐shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2‐azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB‐g‐PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core‐shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ‘cluster’ dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge‐like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ‘cluster’ state leads to better impact resistance. The deformation mechanism in impact tests was multi‐crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry

Co-toughened Polystyrene by Submicrometer-Sized Core–Shell Rubber Particles and Micrometer-Sized Salami Rubber Particles

“…1−3 Some viewpoints insist that the dominant deformation mechanism is multiple crazing 4−8 and crazes are associated with rubber particles. 9 In particular, Donald and Kramer have investigated the crazing initiation, growth, and fracture mechanisms of HIPS with micrometer-sized salami rubber particles in detail. 10 They found that the effective toughness of HIPS was significantly dependent on the rubber particle size and crazes cannot be initiated from the rubber particles with a diameter less than 1 μm.…”

“…Nevertheless, the applications of polystyrene are significantly confined due to its brittleness. To improve its toughness, high-impact polystyrene (HIPS) was obtained consisting of polystyrene continuous phase and rubber dispersive phase. − Some viewpoints insist that the dominant deformation mechanism is multiple crazing − and crazes are associated with rubber particles . In particular, Donald and Kramer have investigated the crazing initiation, growth, and fracture mechanisms of HIPS with micrometer-sized salami rubber particles in detail .…”