What are the differences between PP and PE materials?

- Mar 08, 2019-

PE:

  1. Crystalline material has small moisture absorption, does not need full drying, excellent fluidity and pressure sensitivity. When forming, high pressure injection should be used. The material temperature is uniform, the filling speed is fast, and the pressure is sufficient. It is not suitable to use direct gate to prevent uneven shrinkage and increase internal stress. Attention should be paid to the selection of gate location to prevent shrinkage holes and deformation.

  2. The shrinkage range and shrinkage value are large, the orientation is obvious, and the deformation and warping are easy. The cooling speed should be slow. The die should have a cooling material hole and a cooling system.

  3. Heating time should not be too long, otherwise decomposition will occur.

  4. When soft plastic parts have shallow side grooves, they can be demoulded forcibly.

  5. Melt rupture may occur. It is not appropriate to contact with organic solvents in order to prevent cracking

PP:

 1.Crystalline material has low hygroscopicity, easy to melt rupture, and easy to decompose in long-term contact with hot metal.

 2.Fluidity is good, but the shrinkage range and shrinkage value are large. Shrinkage cavity, dent and deformation are easy to occur.

 3.Cooling speed is fast, casting system and cooling system should slow heat dissipation, and attention should be paid to controlling the forming temperature. Material temperature is easy to orient at low temperature and high pressure. When mould temperature is lower than 50 degrees, the plastic parts are not smooth, easy to produce poor welding, flow marks and warpage deformation over 90 degrees.

 4.Plastic wall thickness should be uniform to avoid glue shortage and sharp corners in order to prevent stress concentration.