Several points need to be considered in extruding Rigid PVC profiles for the material formula and its characteristics.
- Rigid PVC profiles are generally extruded with no or little plasticizer added, which inevitably results in poor fluidity. In the extrusion process, the plastic is required to be in a viscous state. In order to gain a certain degree of fluidity, the extrusion temperature is increased. However, there is a certain limit to the increase in temperature. If the decomposition temperature of PVC plastic is exceeded, it will not be able to operate normally. Therefore, in formula design, it is necessary to consider the characteristics of the rigid PVC extrusion temperature and decomposition temperature, try to choose a reasonable formula to make up for this defect.
- Each component in the PVC plastic formula has a certain relationship with each other and cannot be isolated. When choosing additives, all aspects should be considered. The physical property indicators often influence and restrict each other. In order to improve the impact resistance of PVC, it is effective to add rubber or elastic polymers, but it will cause a decrease in modulus, rigidity, and heat resistance. As another example, in order to improve the heat resistance of PVC, chlorination can increase the glass transition temperature Tg of PVC. However, the melting temperature Tm is also increased accordingly, which significantly deteriorates the processability and fluidity.
- The evaluation of the quality of the formula should be based on the physical properties of the product. Of course, the physical properties are also dependent on the different factors and conditions of the product. For example, according to the environment, color, and size of the window frame used indoors and outdoors, The required physical properties also vary.
- Compared with other thermoplastic resins, the rigid physical properties and processing performance of PVC are greatly affected by additives, mixing technology, and extrusion processing in the formulation. The formulation of hard PVC is a very complex and important task. The rigid PVC plastic formula is prepared by mixing more than ten kinds of additives such as PVC resin, stabilizers, modifiers, lubricants, fillers, colorants, etc. The types and quantities of additives used are different, and they can be formulated into different performance formulas.
For this reason, after clarifying the performance characteristics of rigid PVC plastics, it is necessary to determine the role of each additive in the formulation, study the entire system including molding conditions, and make comprehensive judgments to obtain door and window profiles with excellent performance indicators.