Effect of supercritical carbon dioxide on PMMA/rubber and polystyrene/rubber blending: Visosity ratio and phase inversion

Abstract

Supercritical carbon dioxide (scCO2) was added during blending of polystyrene or poly(methyl‐methacrylate) (PMMA) and a rubber impact modifier (SP 2207). The resulting blend morphologies were compared. The compounding took place in a Leistritz ZSE‐27 twin‐screw extruder at 100 RPM, at a temperature of 200°C, and with 2.0 wt% CO2 Injection. The viscosity reduction of PMMA, polystyrene, and SP 2207 was measured using a slit die rheometer attached to the twin‐screw extruder. A viscosity reduction of up to 84% was seen with PMMA, 70% with polystyrene and 30% with SP 2207. The solubility of CO2 in these polymers was measured in a high‐pressure vessel at 200°C and 13.78 MPa (2000 psi). A solubility of 5.79 wt% CO2 was seen with PMMA, 3.65 wt% with polystyrene, and 2.60 wt% with SP 2207. The injection of CO2 reduced the size of the dispersed rubber phase in both polystyrene and PMMA. For both blends (polystyrene/SP 2207 and PMMA/SP 2207) with and without the injection of CO2, the extruder length for phase inversion was shortened by about L/D = 4, or 10% of the total extruder length. The impact strength for a 70/30 polystyrene/SP 2207 blend was increased by 26% by the addition of CO2. The improvement in impact strength was not as large for blends of PMMA and SP 2207.

Experimental and numerical studies on the effects of pressure release rate on number density of bubbles and bubble growth in a polymeric foaming process

“…The zero shear viscosity was used as the value of viscosity. Although CO 2 -induced viscosity depression has been reported by many authors (Elkovitch et al, 2000(Elkovitch et al, , 2001Han et al, 2002;Kwag et al, 1999Kwag et al, , 2001Lee et al, 2000;Royer et al, 2000;Utracki and Simha, 2001;Xue and Tzoganakis, 2003), its effect on bubble growth may be limited (Chen et al, 2006). The zero-shear viscosity used in this study was not measured under a high-pressure CO 2 condition (Table 1).…”

Effects of nano- and micro-fillers and processing parameters on injection-molded microcellular composites

“…The effect of CSR particle sizes on toughening highly relates to the matrix material and rubber property [23][24][25][26][27][28]. The dissolved gas and the processing method also influence the mechanical properties of the polymer with the rubber impact modifier [29].…”

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

“…If the latter effect is more pronounced than the former, the capillary number can be sufficiently increased to surpass j c , thereby resulting in CO 2 -enhanced droplet breakup. Experimental evidence confirms [173][174][175][176][177] that scCO 2 can substantially decrease the dispersion size of various polymer blends by lowering the viscosity and/or reducing the interfacial tension. For instance, the addition of scCO 2 to an immiscible PMMA/PS blend with an initial viscosity ratio of ca.…”

“…The role of scCO 2 has also been investigated in blends of PS and PMMA with rubber (an ethylene-methacrylate copolymer). [177] A reduction of the viscosity ratio again results in reduced dispersion sizes: the diameter of rubber domains embedded in a PS matrix is reduced from ca. 10 to 1-2 lm upon the addition of scCO 2 .…”