Fu Zhimin, He Guoshan, Wang Wanjuan
Papers # 2016 Berlin
Our research shows that in a torque rheometer test the greater the fusion degree of PVC-U is, the higher the minimum torque of the torque curve is, and the smaller the difference between the maximum torque and the minimum torque of the torque curve. According to the relationship, the method of evaluating the fusion degree of PVC (Df) was proposed and has been used in the production process control.
The fusion degree of unplasticized poly (vinyl chloride) (PVC-U) is an important factor affecting the performance of PVC-U pipes, especially the long-term hydrostatic strength. The Dichloromethane Test (DCMT, ISO 9852) is a standard method of evaluating the fusion degree of PVC-U but DCMT cannot evaluate the fusion degree quantitatively and the use of dichloromethane is an environmental concern. ISO 18373-1:2007 “Rigid PVC pipes -- Differential scanning calorimetry (DSC) method -- Part 1: Measurement of the processing temperature” and ISO 18373-2:2008 “Rigid PVC pipes -- Differential scanning calorimetry (DSC) method -- Part 2: Measurement of the enthalpy of fusion of crystallites” are both indirect methods of evaluating the degree of fusion. A local region of PVC pipe could be detected by DSC accurately. However, due to the terminal temperature of micro-crystalline melting progress having different calibrations, fusion degree cannot be measured directly by DSC.