PE: polyethylene characteristics (molding)
1. Crystal material, low moisture absorption, no need to be fully dried, excellent fluidity, fluidity is sensitive to pressure, high pressure injection should be used during molding, material temperature is uniform, filling speed is fast, pressure is sufficient. Direct gate is not suitable to prevent shrinkage Unevenness increases internal stress. Pay attention to the location of the gate to prevent shrinkage and deformation.
2. The shrinkage range and shrinkage value are large, the direction is obvious, and it is easy to deform and warp. The cooling speed should be slow, the mold is provided with a cold cavity, and there is a cooling system.
3. The heating time should not be too long, otherwise decomposition will occur.
4. When the soft plastic parts have shallow side grooves, they can be forcedly demolded.
5. Melt rupture may occur, it is not appropriate to contact with organic solvents to prevent cracking.
PP: Polypropylene characteristics (molding)
1. Crystal material, low hygroscopicity, prone to melt fracture, easy to decompose after long-term contact with hot metal.
2. The fluidity is good, but the shrinkage range and shrinkage value are large, which is prone to shrinkage, dents and deformation.
3. The cooling speed is fast, the pouring system and the cooling system should dissipate heat slowly, and pay attention to controlling the molding temperature. The material temperature is easy to orient when the temperature is low and high pressure, and the mold temperature is less than 50 degrees, the plastic parts are not smooth, easy to produce poor welding, flow marks, Warpage deformation is easy to occur above 90 degrees.
4. The thickness of the plastic wall must be uniform to avoid lack of glue and sharp corners to prevent stress concentration.
The scientific name of PET is polyterephthalic acid plastic. The raw material of PET plastic is milky white or light yellow and highly crystalline. Compared with PVC materials, PET has good optical properties and weather resistance, non-toxic stability, but is not immersed in hot water and alkali. PET bottle packaging is suitable for packaging food, medicine, cosmetics and other industries.
PET plastic steel strapping is better than steel straps, saving cost and ensuring quality. Support the use of electric baler, pneumatic baler, etc.