Modification of polyvinyl chloride properties by nitrile butadiene rubber

Abstract

A study on the modification of polyvinyl chloride(PVC) properties by an acrylonitrile butadiene(NBR) rubber was conducted. The PVC used in the present study has been compounded with a plasticizer. NBR was mixed with the compounded PVC at 20, 30, 40 and 50 phr. Tests on the mechanical properties of the PVC/NBR systems under tension reveal that the elongation at break tends to increase. In addition, the tear strength, the compression set and the abrasion resistance are all improved. Physical properties such as the specific gravity and the hardness are found to decrease. The PVC/NBR systems exhibit more yellowness than the initial compound PVC. An immersion of the PVC/NBR systems in three petrol reagents, i.e., hexane, unleaded gasoline and motor oil, was found to affect their mechanical properties. Hexane and unleaded gasoline reduce the tensile strength, the elongation at break, the modules of elasticity and the specimen weight. Chemical analysis confirms that the reduction in weight is due to an extraction of the plasticizer initially compounded there in the PVC. The presence of the NBR rubber helps retaining the plasticizer and hence reducing the plasticizer extraction. Although motor oil tends to increase the tensile strength, other properties are unchanged. A study in the thermal properties in terms of the glass transition temperature (T(subscript g)) reavels that there exits only T(subscript g) for the PVC/NBR system. This implies that PVC and NBR are compatible as is evidenced by the microscopic observation. Photomicrographs show that there is no phase separation between the PVC and the NBR.