A brief historical review has been made of rheological instrumentation developed for measuring the flow properties of vinyl materials. During this maturation of techniques the need for more complete flow characterizations spawned the development of dynamic mechanical instruments. These instruments provided convenient and accurate means of generating complex viscosity (n*) data composed of elastic (C') and (C") elements. Examples have been presented illustrating how these newer techniques are able to reliably provide critical data needed to control productivity and product performance properties. Extension of these techniques to on-line rheometry has improved quality control link in the compounding operation.
PVC 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 p), 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 calcium carbonates also improved the Ultraviolet light stability of the PVC.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.