Believe that a lot of people don't know what is PP, I don't know, before contact with the industry PP is a kind of plastic, when it comes to plastic always didn't know. I found some introduction about the PP for everybody to understand:

PP plastic, chemical name: polypropylene. English name: Polypropylene (PP) : the proportion of 0.9 to 0.91 grams per cubic centimeter Molding shrinkage rate: 1.0 2.5% molding temperature: 160-220 鈩�.

PP for crystalline polymer, commonly used plastic PP in the light, only 0.91 g/cm3 density (smaller than water). General plastic, PP had better heat resistance, its thermal deformation temperature is 80-80 鈩�, can in the boiling water. PP has good resistance to stress cracking resistance, high bending fatigue life, commonly known as the "hundred fold glue". The comprehensive performance of PP is better than that of PE material. PP products light weight, good toughness, good chemical resistance. PP disadvantages: low dimensional accuracy, insufficient rigidity, poor weather resistance, easy to produce "copper pollution", it has the shrinkage phenomenon, after demoulding, easy to become fragile, easy to deformation. In daily life, the commonly used preservation box is made of PP materials.

Process characteristics:

PP in the melt temperature have good liquidity, good formability, PP on processing has two characteristics: one: PP melt viscosity with the increase of shear rate has a significant reduction (less affected by temperature); Second: the high degree of molecular orientation in larger shrinkage rate.

Processing temperature of PP at about 200-300 鈩�, it has good thermal stability (decomposition temperature is 310 鈩�), but high temperature (270-300 鈩�), for a long time to stay in the gun barrel will have the possibility of degradation. Because of the viscosity of PP have significantly lower with the increase of shear rate, so improve the injection pressure and injection speed will increase its liquidity, improve the shrinkage deformation and sag. Die WenYi control within 30 to 50 鈩�. PP melt mold through narrow gap and appear front. PP in the melting process, to absorb a lot of heat of fusion (specific heat is larger), the product after the mold is hot. PP material process does not need to dry, and crystallinity of PP shrinkage rate is lower than PE.