1.The processability of PP. The hygroscopicity of PP is very small, so in general do not need to be dried before molding processing, if more than the allowable value, it should be dry; containing tertiary carbon atoms in the molecular structure of PP, the antioxidant capacity is very low, the plasticizing should add antioxidant; PP in more than 280 degrees is the thermal degradation occurs, so that performance deterioration, melt and the metal wall surface contact will accelerate the thermal degradation, thus forming should avoid melt stranded for a long time in the barrel; PP good melt fluidity, between HDPE and LDPE, easy molding of thin, long process of plastic parts; PP has a range of crystallization, molding shrinkage rate is large, 1.0%-3.0%, and have more apparent after shrinking, so it is easy to produce the shrinkage, dents and deformation, and the direction of strong; melting and melt the heat content of PP is higher than LDPE, the crystallization and cooling process will produce more heat, so die to a cooling system is good, in order to reduce plastic deformation; due to thermal shrinkage and crystallization of PP, in the forming process of the specific volume changes greatly, plastic steel, hole and wall thickness larger parts easy to have a bubble and the dent defect; obvious orientation of PP melt temperature is low, especially in the Low temperature and high pressure even more, so to control the molding temperature; PP plastic stripping large shrinkage, should be in after stripping in shaping device placed more than 1 days to finalize the design, for the plastic parts size precision, time of heat treatment; the molding shrinkage rate of PP greatly, low temperature brittle, so the plastic pieces should be uniform wall thickness, avoid gap, since the establishment of diplomatic ties, prevent stress concentration; if the holding time is too long will make the plastic parts appear larger contraction and quality defects, thus to ensure added melt solidification contraction material, try to shorten the holding time; PP melt is non Newtonian obvious, viscosity shear rate and temperature sensitive call.
  2.The main forming conditions PP. Barrel temperature. In need of injection pressure and injection speed is small, can choose the barrel temperature low. General barrel temperature control in 210-280 degrees, nozzle temperature than the barrel temperature low 10-30 degrees. When forming thin-walled, complex plastic parts, barrel temperature is high; when the plastic is thick, the barrel temperature and die temperature is low. The crystallization of PP ability, improve the mold temperature is helpful to increase the degree of crystallinity, but also conducive to large molecular relaxation, reduce the orientation of molecules, thereby reducing the stress of the plastic parts, reduce material shortage, bubbles and other defects, often in the process of the mold temperature to 20-60 degrees; injection pressure. In injection molding, injection pressure is conducive to improve the liquidity of plastic melt. Injection pressure plunger type injection molding machine to be higher than that of the screw type. The general control in 70-100MPa, the specific value to test mode to decide, not lack of material to plastic parts, overflow and no dents and bubble prevail.