Reduction of notch sensitivity and improvement in low‐temperature impact strength of PVC

Abstract

AbstractPVC is a notch‐sensitive polymer. The drop weight impact strength is also lost dramatically below 0°C. This requires special formulation considerations for critical applications. The general trend is to use polymeric impact modifiers, which are rubbery, graft polymers or blends of both hard and rubbery materials. This is achieved with some sacrifice in flexural modulus and formulation economics. A recent study conducted to relate calcium carbonate particle size with notched Izod and low‐temperature drop weight impact strength has shown that the stearate‐coated Ultrafine precipitated calcium carbonate (0.07 μ), at 15 phr loading, substantially improves both properties without sacrifice in flexural modulus. The formulation cost is also favorable. It is hypothesized that improvement in the above properties is primarily due to uniform stress distribution and lack of defect structure, as observed with coarse fillers. Surprisingly, the optimum‐particle‐size, coated, precipitated calacium carbonates also improved the Ultraviolet light stability of the PVC.