In the production of PVC pipe & fitting, 1~5 phr of PVC lubricants are usually added into PVC Resin in order to enhance the lubrication between materials and equipment’s contact face and surface finish of end products and improve the processability and processing speed. It is found that PVC lubricants have critical effect on the plasticization of materials and mechanical property like water pressure resistance of PVC pipe fitting.
Classification of Lubricants Used in PVC Pipe Fitting
Lubricants used in PVC pipe can be divided into two types.
1. Some lubricants can be compatible with Polyvinyl Chloride (PVC). Its function is to decrease internal friction among all materials and improve the fluidity of materials. This type of lubricants is called internal lubricant, such as Stearic Acid, glycerin monostearate and Stearic Xylitol, etc.
2. The other type of lubricant has low compatibility with Polyvinyl Chloride (PVC). It will be extracted to the surface between between materials and equipment’s contact face so as to reduce the adhesion and friction on such contact face. This type is called external lubricant, including Paraffin Wax, PE Wax, etc.
There is no strict division criterion between two types of PVC lubricants in the processing. The functions of external and internal lubricants will be changed under different processing temperature.