PP-H commonly known as polypropylene homopolymer, because of its good
resistance to fracture, also known as a hundred fold glue. PP-H is a kind of
semi transparent and semi crystalline thermoplastic, which has the
characteristics of high strength, good insulation, low water absorption, high
temperature, low density and high crystallinity. The modified filler is usually
made of glass fiber, mineral filler, thermoplastic rubber and so on. Different
uses of PP-H pipe has a large difference in liquidity, the general use of PP-H
flow rate between ABS and PC.
1. Plastics processing. Pure PP-H is translucent ivory white, can be dyed a variety of colors. PP-H staining in the general injection molding machine can only use color masterbatch. On the machine, there is an independent plasticizing component for strengthening mixing, and also can be dyed with toner. Outdoor products, generally use UV stabilizer and carbon black filling. The use of recycled material ratio of not more than 15%, otherwise it will cause the intensity degradation and decomposition. PP-H pipe processing generally do not need special treatment.
2. Injection molding machine selection of injection molding machine selection no special requirements. Because PP-H has high crystallinity. Injection molding machine with high injection pressure and multi section control. Clamping force is generally determined by 3800t/m2, the amount of injection can be 20%-85%.
3. Mold and gate design mold temperature 50-90 C, for high dimensional requirements of high mold temperature. The core temperature of the cavity than the low temperature above 5 DEG C, channel diameter 4-7mm, needle gate length 1-1.5mm, diameter up to 0.7mm. The shorter the length of the side gate, about 0.7mm, the depth of half the thickness of the wall, the width of the wall thickness of two times, and with the cavity length of the melt flow will be increased. The mold must be of air exhaust hole depth is 0.025mm-0.038mm, thickness of 1.5mm, in order to avoid shrinkage marks, it is necessary to use the large and round injection port and circular runner, the thickness of the stiffener is smaller (such as the wall thickness of 50-60%). Homopolymer PP-H manufactured products, the thickness can not be more than 3mm, otherwise there will be bubbles (thick wall products can only be used copolymer PP-H).
4. The melting point of the melting temperature PP-H is 160-175 DEG C, and the decomposition temperature is 350 DEG C, but the temperature setting should not exceed the temperature of 275 DEG C during injection. The melting temperature is preferably at 240.
5. Injection speed to reduce the internal stress and deformation, should choose high-speed injection, but some grades of PP-H and mold is not applicable (human mantle is now bubbles, air lines). If the pattern of the surface of the gate by the gate diffusion of light and dark stripes, the use of low speed injection and high mold temperature.
6. Melt back pressure can be used 5bar adhesive back pressure, toner material back pressure can be properly adjusted.
7. High injection pressure (1500-1800bar) and pressure holding pressure (about 80% of the injection pressure) were used for injection and packing. About 95% of the whole trip to the pressure, with a longer holding time.
8. The post processing of the product to prevent the shrinkage of the deformation produced after the crystallization, the product is generally hot water immersion treatment.
