Toughening of polystyrene and poly(phenylene oxide) matrices with elastomeric styrene‐based block copolymers: Role of molecular architecture

Abstract

SYNOPSISThe effects of the molecular architecture of elastomeric styrene-based block copolymers on efficiency of toughening a brittle (polystyrene) and a ductile [ a miscible blend of 80% phenylene oxide copolymer and 20% polystyrene (8OPEC) ] polymer were explored experimentally. Toughening appears to be mainly controlled by the blend morphology, which is determined by the rheological characteristics of the block copolymer relative to that of the matrix. The formation of dispersed particles during melt blending in a Brabender Plasticorder is strongly influenced by the ratio of the matrix and block copolymer viscosities (estimated here by Brabender torque). The size of the dispersed particles was found to be proportional to the 1.77 power of the torque ratio when this ratio is greater than unity. Thus, to a first approximation the effect of block copolymer architecture on toughening efficiency is related to how this structure affects the rheological behavior of the copolymer. Excellent toughness of polystyrene was achieved when the particle size was larger than 1-2 pm. The 80PEC resin is best toughened by block copolymers that form a cocontinuous phase morphology. The extent of toughening of this matrix appears to be a strong function of the styrene block molecular weight, whereas this structural feature seems to have no significant effect in toughening polystyrene.

The Role of the Order−Disorder Transition Temperature of Block Copolymer in the Compatibilization of Two Immiscible Homopolymers

“…During the past decade, a number of research groups reported on compatibilization of two immiscible homopolymers, theoretically [1][2][3][4][5][6][7] and experimentally. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Some researchers [23][24][25] investigated the adhesion between two immiscible homopolymer layers in the presence of a diblock copolymer in between, and still others 26,27 investigated fracture mechanisms and the interface toughness of two immiscible homopolymers layers in the presence of a diblock copolymer in between.…”

“…In the experimental studies on compatibilization of two immiscible homopolymers using a block copolymer, for instance, Paul and co-workers [8][9][10][11][12] published a series of papers, reporting an improvement of some mechanical properties of binary blends of polystyrene (hPS) with high-density polyethylene (HDPE) or low-density polyethylene (LDPE) in the presence of a polystyrene-blockpoly(ethylene-co-1-butene)-block-polystyrene (SEBS triblock) copolymer, which is a hydrogenated polystyreneblock-polybutadiene-block-polystyrene (SBS triblock) copolymer. However, they did not investigate the morphology of the ternary blends at the interface between SEBS triblock copolymer and homopolymer.…”

“…Although in the past many experimental studies [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] were reported on the compatibilization of two immiscible homopolymers, little is mentioned in the literature about the role that the order-disorder transition temperature (T ODT ) of a block copolymer plays in the compatibilization. Specifically stated, even when a block copolymer meets with all the thermodynamic requirements for compatibilization of two immiscible homopolymers, the block copolymer would not play the role of an effective compatibilizing agent unless the melt processing temperature is chosen to be above the T ODT of the block copolymer, because an intimate mixing between homopolymers and a microphase-separated block copolymer is not expected to occur at melt processing temperatures below the T ODT of the block copolymer.…”

“…A block copolymer, when properly designed in terms of chemical structure, architecture, and molecular weight, can be used as an effective compatibilizing agent for a pair of immiscible homopolymers. During the past decade, a number of research groups reported on compatibilization of two immiscible homopolymers, theoretically − and experimentally. − Some researchers − investigated the adhesion between two immiscible homopolymer layers in the presence of a diblock copolymer in between, and still others , investigated fracture mechanisms and the interface toughness of two immiscible homopolymers layers in the presence of a diblock copolymer in between.…”

The effect of compatibilization and rheological properties of polystyrene and poly(dimethylsiloxane) on phase structure of polystyrene/poly(dimethylsiloxane) blends

“…A block copolymer, when properly designed in terms of chemical structure, architecture, and molar mass, can be used as an effective compatibilizing agent or as an interfacial agent for a pair of immiscible homopolymers. During the past decade, a number of research groups reported on miscibility of two immiscible homopolymers, theoretically and experimentally 5–7, 17, 21–26. Some researchers27–30 investigated the adhesion between two immiscible homopolymer layers in the presence of a diblock copolymer, and still others31, 32 investigated fracture mechanisms and the interface toughness of two immiscible homopolymer layers in the presence of a diblock copolymer.…”