PP: commonly known as polypropylene, the main raw material of plastic pallets, because of its anti-break performance, also called "pleated plastic."
PP is a semi-transparent, semi-crystalline thermoplastics with high strength, good insulation, low water absorption, heat to form high temperature, density, crystallinity and high degree. Modified fillers are usually glass fibers, mineral fillers, thermoplastic rubber. It also determines the performance of plastic pallets for the development and production.
Different uses of the PP is more difference in their mobility greatly, the general use of the PP flow rate range between ABS and PC.
1, PP plastic handle and plastic card processing board
PP is a translucent ivory pure white, can be dyed various colors. PP injection molding machine dyeing in general can only be used on the masterbatch can also be stained with dye. Products for outdoor use, general use of UV stabilizers and carbon black filled. The proportion of recycled material used should not exceed 15%, otherwise it will lead to decline and decomposition of color intensity. PP injection molding plastic pallets before the general without special drying.
2, PP injection molding machine and plastic pallets used
The selection of the injection molding machine has no special requirements, of course, large-scale production of plastic injection molding machine pallet becomes possible. Because of high crystallinity PP requires the use of higher injection pressure and can be computer controlled multi-stage injection molding machine. 3800t/m2 clamping force generally determined by the injection volume can be 20% -85%.
3, plastic pallet mold and gate design
Mold temperature 50-90 ¡æ, the higher the size requirements of high mold temperature. Core temperature is lower than the cavity temperature above 5 ¡æ, flow channel diameter of 4-7mm, needle-shaped gate length of 1-1.5mm, the diameter can be as small as 0.7mm. Polygon gate length as short as possible, about 0.7mm, a depth of half the thickness, width of twice the wall thickness, and with the length of the mold cavity by melting willing to increase. Mold must have a good exhaust of the ventilation holes are deep 0.025mm-0.038mm, thickness 1.5mm, to avoid shrinkage marks, we must use large, round and round nozzle flow channel, the thickness of the ribs is smaller (for example, is the wall thickness of 50-60%). PP homopolymer made products, the thickness of not more than 3mm, or there will be bubbles (thick-walled products can only be used copolymer PP).
4, melt temperature
PP''''s melting point 160-175 ¡æ, decomposition temperature is 350 ¡æ, but when the temperature setting in the injection process can not exceed 275 ¡æ. Melting temperature of the best in the 240 ¡æ, which is commonly used in injection molding of plastic pallets temperature control values.
5, the injection speed
To reduce the internal stress and deformation, should choose high-speed injection, but some level of PP and the mold is not applicable (person mantle is the bubble, gas lines). If the surface pattern engraved with the proliferation of light and dark by the gate stripes, then use the high speed injection and mold temperature.
6, melt back pressure
Available 5bar melt back pressure, back pressure can be properly colored powder increased.
7, injection and holding pressure
A higher injection pressure (1500-1800bar) and holding pressure (injection pressure of about 80%). Around 95% of the whole trip switch to holding pressure, with a longer dwell time.
8, plastic card products, forming the post-processing board
In order to prevent the later use of plastic pallets and shrinkage deformation, products normally subject to hem treatment.