The effect of diblocks and ripening on the Izod impact of bulk PS/PB blends

Abstract

Bulk blends were used to study the effectiveness of various PS-PB diblock copolymers in improving the impact strength of PS/PB blends. The blends were produced by compositional quenching, and further ripened to control particle size and the diblock concentration at the homopolymer interface. It was found that an optimal molecular weight of diblock copolymer exists for the maximum notched Izod. Low molecular weight diblocks provided insufficient adhesion due to lack of entanglements, and high molecular weight diblocks provided insufficient interfacial concentration due to stearic crowding. The maximum notched Izod, for 23% rubber phase volume, was achieved with 1-particles, a copolymer surface density of 0.17 chains/nm 2 , some crosslinking, and a medium molecular weight, tapered diblock, M w ϭ 154,000, having a 30% PS content. The combination of high impact strength, 6.2 ft.-lbf./in., and high modulus, 2.2 GPa, significantly exceeds that of commercially available super highimpact polystyrene.

Toughening modification of PS with n‐BA/MMA/styrene core–shell structured copolymer from emulsifier‐free emulsion polymerization

“…Polystyrene (PS) is a typical example of a brittle thermoplastic, and over the last several decades many efforts have been made to improve its fracture resistance. According to the literature, modifiers for toughening PS can be divided into two classes: (1) blending with rubbery materials, for example, styrene–butadiene rubber (SBR), a styrene–butadiene–styrene copolymer (SBS), natural rubber (NR),1, 2 polybutadiene (PB),3–5 or ethylene propylene rubber (EPR)6–9; however, with this modification method the aging resistance is poor if the modifiers are polybutadiene (PB) or PB‐containing copolymers, which have double bonds and are immiscible with PS. Furthermore, there are processing difficulties when a rubber is used as the modifier.…”

Calix[6]pyrrole and Hybrid Calix[n]furan[m]pyrroles (n+m=6): Syntheses and Host–Guest Chemistry

“…More importantly, the entanglement density of the molecular chain is rather low 46. The combined effect causes a low impact strength of PA1010 47. As for iPP, the order parameters of both LMW‐iPP and HMW‐iPP are largely enhanced, resulting in improvement of the impact property 29, 48…”

Toughness enhancement of high‐impact polystyrene based on γ‐radiation vulcanized natural rubber latex by using block copolymer

“…The presence of KRATON caused an increase in the impact energy of HIPS over the uncompatibilized PS, indicating the role of KRATON as a compatibilizer. This block copolymer provided good interfacial adhesion by the attachment of a long PI block length to the NR particle, due to its high MW, which is entangled enough in the homopolymer, 3, 4 while two short PS blocks of KRATON protruded into the PS matrix. The maximum impact resistance was obtained using 5% KRATON, an amount which possibly caused the exact saturated rubber/PS interface.…”

“…This was possibly due to the lamella at the interface formed by the excess copolymer causing weak interfacial adhesion. 3, 4 The use of higher than 20% of KRATON resulted in an increase in the impact resistance of HIPS. This could be explained in terms of the formation of a microdomain of KRATON molecules, a thermoplastic elastomer, in the PS phase owing to the high viscosity of the block copolymer 17, 18.…”

“…Since rubber–matrix adhesion is an important factor in influencing the toughness of a brittle polymer, it was the aim of this present study to investigate the effect of a block copolymer on the enhancement of the impact property of HIPS, prepared according to the RVNR latex/phase transfer/bulk polymerization technique. 1, 2 It has been postulated that the effectiveness of the block copolymer depends on different structural characteristics, such as the chemical structure of the block, molecular weight of each block and of the copolymer, and the mode of addition of the compatibilizer 3–6. Two types of triblock copolymers composed of relevant homopolymers [polyisoprene (PI) and PS)], that is, PS‐ b ‐PI‐ b ‐PS (SIS) and PI‐ b ‐PS‐ b ‐PI (ISI), were, therefore, incorporated into HIPS.…”