One of the PC extrusion molding conditions -- material analysis

The mainstream ratio of PC/ABS materials in the market is that PC accounts for 60% to 70%, and ABS accounts for 30% to 40%. The different proportions are mainly to improve the melt fluidity, formability, electroplatability and appearance of PC, and to improve the heat resistance, impact resistance and rigidity of ABS products. But in terms of the overall modification goal, obtaining good formability, appearance and reducing PC cost are the most important. PC/ABS, like PVC-U, is an amorphous polymer material, and its shape changes with temperature as shown in Figure 1, where Tg represents the glass transition temperature, Tf represents the viscous fluid transition temperature, and the subscripts 1 and 2 represent PVC-U and PC/ABS materials. It can be seen from Figure 1 that the overall shape of the two is similar with temperature, but the PC/ABS material has a relatively high glass transition temperature and viscous flow transition temperature.

According to the comparison of the performance parameters of the two materials, the density and expansion coefficient of the two materials are equivalent, and the shrinkage rate is not much different. Except for the large difference in the shape transformation temperature, there is only a certain difference in the melt flow rate. This shows that the extrusion molding structure of PC/ABS material can be established on the basis of PVC-U extrusion molding structure, but due to the difference of some performance parameters, the extrusion molding structure cannot be completely the same, otherwise there will be a Series molding problems. For example, the melt flow rate of PC/ABS is much higher than that of PVC-U material, indicating that its flow state is better in the molten state, so the distance between the extrusion die head and the shaping die should not be too large, otherwise the parison will enter the shape from the die head During the molding process, mold blocking may easily occur due to excessive bending deformation.

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