ABSTRACT
302PVC is well known as a versatile thermoplastic material. Alterations in PVC polymer morphology, molecular weight, and/or the compound additive system can yield dramatic transformations in the processing characteristics and physical properties of PVC compounds. Over the last 40 years this versatility has enabled PVC to participate in a number of diverse extrusion market areas, such as pipe, house siding, windows, and wire and cable. During the late 1970s, a new family of low-molecular-weight, higher melt flow rigid vinyl compounds designed specifically for injection molding emerged. These new materials have successfully overcome many of the processing problems formerly associated with injection molding of rigid vinyl. Combined with the excellent processability are a gamut of other specialized property potentials: toughness, transparency, weatherability, and higher modulus, among others. Of course, these unique features are always combined with the inherent chemical resistance, flame retardance, and favored economics of vinyl. This chapter describes the evolution of the new higher melt flow rigid vinyl injection-molding compounds, as well as discussions of the product characteristics, market trends, typical formulations, part design, and processing of these materials.
