1) PBT has a low hygroscopicity, but it is more sensitive to moisture at high temperatures. It will degrade the PBT molecules during the molding process, darken the color and produce spots on the surface, so it should usually be dried.
2) PBT melt has excellent fluidity, so it is easy to form thin-walled, complex-shaped products, but pay attention to mold flashing and nozzle drooling.
3) PBT has an obvious melting point. When the temperature rises above the melting point, the fluidity will increase suddenly, so attention should be paid to it.
4) PBT has a narrow molding processing range, crystallizes quickly when cooling, and good fluidity, which is especially suitable for rapid injection.
5) PBT has a larger shrinkage rate and shrinkage range, and the shrinkage rate difference in different directions is more obvious than other plastics.
6) PBT is very sensitive to the response of notches and sharp corners. Stress concentration is likely to occur at these positions, which greatly reduces the load-bearing capacity, and is prone to rupture when subjected to force or impact. Therefore, this should be paid attention to when designing plastic parts. All corners, especially the internal corners, should use arc transitions as much as possible.
7) The elongation rate of pure PBT can reach 200%, so products with smaller depressions can be forced out of the mold. However, after filling with glass fiber or filler, its elongation is greatly reduced, and if there are depressions in the product, forced demolding cannot be implemented.
8) The runner of the PBT mold should be short and thick if possible, and the round runner will have the best effect. In general, both modified and unmodified PBT can be used with ordinary runners, but glass fiber-reinforced PBT can only have good results when hot runner molding is used.
9) The point gate and the latent gate have a large shearing effect, which can reduce the apparent viscosity of the PBT melt, which is conducive to molding. It is a frequently used gate. The gate diameter should be larger.
10) The gate is best to face the core cavity or core, so as to avoid spraying and minimize the filling of the melt when flowing in the cavity. Otherwise, the product is prone to surface defects and deteriorates performance.
Post time: Feb-18-2022
