The rheooptical properties of polymer blends: Polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Abstract

SynopsisThe stress-optical coefficients ( SOCs) of miscible polystyrene (PS) /poly( 2,6-dimethyl-1,4-phenylene oxide) (PPO) blends were measured in the melt state over a wide range of compositions. The flow birefringence measurements were performed with a slit die rheometer using a simplified procedure which eliminates the need to specify the distribution of extinction angles in the flow space. The SOC of the PS/PPO system at -T8 + llO°C follows a linear blending law and full optical compensation (SOC = 0 ) is observed at -61 wt % PS. This value is lower by -10% relative to values obtained by film stretching techniques. Measurements of SOC in the glassy state also yield linear dependence of SOC on composition but no compensation is obtained in this case because of the sign reversal in the SOC of PS in the glass transition range.

Simulation of injection-compression-molding process. II. Influence of process characteristics on part shrinkage

“…According to Greener,25 if the melt temperature somewhere inside the mold reaching detachment is still above the T g , the subsequent cooling without the constraint of the mold wall will lead to uncontrollable shrinkage. The molding will not be geometrically conformable to the cavity.…”