processing aids are standard to high molecular weight acrylic copolymers which are very compatible with PVC. Added to the PVC compound in small quantities, they efficiently improve the PVC gelation from a slow, inhomogeneous melting process to a fast, homogeneous one. Furthermore, its addition remarkably enhances the melt strength and extensibility of PVC compounds required in production processes such as blow molding, film blowing, and thermoforming. Next to the improved processing, they upgrade the PVC surface quality from matt to the desired gloss level. They can improve the flow of the molten PVC, reduce the amount of heat needed to process it, and improve the final product’s physical properties. All of these benefits can lead to improved efficiency and productivity in the plastics manufacturing proces. Acrylic processing aid for PVC has a wide range of applications in industry, including: -PVC pipe and fittings -PVC windows and doors -PVC siding and trim -PVC flooring -PVC ceilings -PVC wall covering . Acrylic processing aids enhance the extrusion or injection molding performance of polymer compounds by promoting fusion, improving melt strength, eliminating surface defects, and decreasing plate out. Acrylic processing aids also improve metal release and surface finish properties in extrusion or calendering. Vinyl compounds require less stearate, oxidized polyethylene, or paraffin wax with Acrylic processing aids. Process aids are random copolymers, whose major component is methyl methacrylate. Other component may be styrene or acrylonitrile. They are PVC compatible.Process aids are produced by emulsion polymerization.
Processing aids have two categories : 1. That promotes fusion and adds rubber elasticity during processing, 2. That adds lubricity during processing.
Processing Aids that promotes fusion : They are acrylic polymer, high molecular weight MMA copolymers (MMA / styrene) or Acrylonitrile styrene.
Modified rheology (Viscosity & Elasticity) and morphology (how primary particles arrange – fuse together) of PVC compound during processing is a function of molecular weight of process aid. Selection of molecular weight of process aids depend upon the process: Lower the molecular weight of process aids and softening temperature, greater is the effect on fusion. They are used in rigid extrusion. Medium molecular weight processing aids are used for calendaring process. Medium – high molecular weight processing aids are used in injection moulding as well as thermoformed products. High molecular weight process aids are used in flexible PVC processing. Higher molecular weight process aids are used in foamed product extrusion at higher Phr level.
