Synthesis of ultra-high molecular weight PVC by addition of mutiunsaturated comonomer

Abstract

The conventional method of altering very high molecular weight of PVC is to adjust the polymerization temperature. The problems of Ultra-High Molecular Weight (UHMW) PVC synthesis are difficulties in controlling the very low polymerization temperature, and the risk and danger of using and handling the highly reactive initiators. In order to obtain the degree of polymerization (D̅P̅) of 2500 ± 50, the polymerization could be carried out at higher polymerization temperatures by addition of multiunsaturated comonomer during the polymerization reaction. In this work, UHMW PVCs with the D̅P̅ of 2500 ± 50 were synthesized by carrying out the normal polymerization temperature temperature at 40๐C first and the subsequent polymerization temperatures were increased to 43, 46, 49, 52, and 58๐C, respectively, along with various amounts of the comonomer at each temperature to achieve the desired DP values. The properties of UHMW PVCs so newly synthesized were characterized. The higher the polymerization temperature deviated from the normal condition, the higher the amount of the comonomer was needed. At the polymerization temperature of 43, 46, 49, 52, and 58๐C, the optimum comonomer contents are 0.075, 0.123, 0.166, 0.200, and 0.280 part by weight per hundred of vinyl chloride monomer, respectively. The better properties of UHMW PVC namely elongation, volume resistivity and dynamic heat stability are improved with increasing comonomer amounts. The inferior properties of UHMW PVC obtained from this technique are the lower tensile strength and the decreasing PVC porosity. The latter produces the unmelted PVC particles, during processing, to produce fisheyes on thin flexible films.