PP is polypropylene plastic
Specific gravity: 0.9-0.91g/cm3 molding shrinkage: 1.0-2.5% molding temperature: 160-220 ℃
Low density, strength and rigidity, can be used at about 100 degrees. It has good electrical performance and high frequency insulation, not affected by humidity, but brittle at low temperature, not resistant to die aging. It is suitable for making general mechanical parts, corrosion-resistant parts and insulation parts
Molding properties 1. Crystalline material, small moisture absorption, easy to occur melt fracture, long-term contact with hot metal easy to decompose
2. Good fluidity, but large shrinkage range and shrinkage value, easy to cause shrinkage cavity, dent and deformation
3. The cooling speed is fast, the pouring system and cooling system should slowly dissipate heat, and pay attention to the control of molding temperature. The direction of low material temperature is obvious. It is especially obvious at low temperature and high pressure. When the mold temperature is lower than 50 degrees, the plastic parts are not smooth, prone to poor fusion, leaving traces, and prone to warping and deformation above 90 degrees
4. The wall thickness of the plastic must be uniform to avoid lack of glue and sharp corners, so as to prevent stress concentration
PVC, PVC, English poly (vinyl chloride)
Specific gravity: 1.38g/cm3 molding shrinkage: 0.6-1.5% molding temperature: 160-190 ℃
Good mechanical and electrical properties, strong acid and alkali resistance, good chemical stability, but low softening point. It is suitable for making sheet, wire and cable insulation layer, seal, etc
Molding performance 1. Amorphous material, small moisture absorption, poor fluidity. In order to improve the fluidity and prevent bubbles, the plastic can be dried in advance. The mold pouring system should be coarse and short, the gate section should be large, and there should be no dead angle. The mold must be cooled and the surface should be chrome plated
2. It is easy to decompose. It is easy to decompose when contacting with steel and copper at 200 ℃. During decomposition, corrosion, irritant gas and molding temperature range are small
3. When the screw type injection machine nozzle is used, the hole diameter should be large to prevent dead angle stagnation. Without inserts, if any, the inserts should be preheated