Properties of PVC/ABS blends

Properties of PVC/ABS blends Introduction Polymer blending is one of the fastest growing areas of polymer technology. Blending of polymer has become an increasingly important technique because it is an economical, viable and versatile way in which new material can be produced with a wide range of properties by merely using conventional processing equipment such as extruder or internal mixer. Polyvinyl chloride is most versatile material in plastic family and second largest consumption material in plastic industries compared to polyolefin’s. It is characterized by rigidity, hardness, excellent tensile modulus and low cost. However, it has low impact strength and poor thermal stability. Which limit’s it’s used. Similarly, Acrylonitrile-Butadiene-Styrene (ABS) is one of most largely used engineering plastics. It has excellent mechanical, thermal, electrical & chemical properties. Followed by inferior properties such as poor weather resistance, highly flammable and merely high cost. Polyvinyl c hloride is largely blended with number of polymers and rubbers. In most cases, to improve properties of PVC and rarely to improve properties of other materials. One of most inferior properties of PVC is low impact strength. To overcome this problem, it is blended with many rubbery materials. It has been shown that impact strength of PVC increases by blending with rubbery material such as NBR, SBR etc. But, it follows the decrease in tensile strength, rigidity and in most cases thermal stability. Hence to achieve high impact strength, better thermal properties along with rigidity, PVC is blended with ABS. The blend of PVC and ABS posses their advantage of impact strength, rigidity, chemical resistance, electrical properties and overall low cost. In ABS, generally the rubbery phase is made of emulsion polymerized polybutadiene, which constitutes the main polymer chain. The glassy phase is made of styrene and acrylonitrile grafted on Polybutadiene. Thus, it combines the impact strength of rubber and tensile strength, heat stability of styrene Acrylonitrile (SAN) Matrix. Thus properties of styrene acrylonitrile (SAN) and polybutadiene are imparted in PVC/ABS blend. Compatibility of Polyblend of PVC/ABS blends Compatibility is characteristics, which shows that components of blends are soluble in one another in all proportion. However, compatible blends are susceptible to phase separation at elevated temperature. While preparing blend, it is necessary to consider compatibility of components of blend with each other, which are used to prepare blends. In case of PVC/ABS blend, PVC and ABS are used as blend components. ABS is made by emulsion polymerization of SAN grafted by Polybutadiene. Polystyrene and Polybutadiene, have solubility parameter close to PVC. Although, solubility parameter of PS and Polybutadiene are close to PVC, they do not have good compatibility because of their being non-polar nature. While Acrylonitrile imparts good compatibility because of itâ⠂¬â„¢s polar nature (as shown in table). Solubility parameter of components of PVC/ABS blend    Yodouchi and Seto reported that in ABS material, the brittle and glassy component ( PS and SAN) improves tensile strength while Polybutadine contribute to toughness. The mechanical properties have been shown to be affected by type of ABS used, due to different Polybutadiene content.