Polypropylene (PP), commonly known as "100 fold adhesive", is a crystalline plastic, its main properties and uses are as follows:
1, use: packaging plastic bags. Drawing. rope. Toys. Daily necessities. Bottles. Washing machine. Can be used for various mechanical parts, such as French blue. Gear. Joint. Pump impeller. Automotive parts. Chemical piping and container equipment. And can be used as lining. Surface coating. Medical and surgical instruments.
2. Large shrinkage rate (1.0-2.5%), usually 1.6% or 2.0%. The size is unstable, the plastic parts are easy to deform and shrink. Commonly used internal mold 718.
3, excellent wear resistance, and good impact resistance at room temperature.
4, transparent color, light weight (density 0.91) can float in water.
5, high molecular tensile strength and service strength (fatigue resistance) high.
6, high chemical stability, insoluble in organic solvents, oil injection. Hot stamping and bonding difficulties. Not plating.
7, good fluidity and molding, overflow edge value 0.03mm. Surface gloss, color. Trauma marks are superior to PE.
The molding process knowledge of polypropylene (PP) is as follows:
1, suitable for rapid injection in order to improve the poor exhaust exhaust groove should be slightly deep 0.03mm.
2. Due to the large shrinkage rate of the material, proper cooling time should be used to accurately control the size of the rubber parts.
3, the back pressure of 0.5mpa is appropriate, dry powder color process should be appropriately increased back pressure to improve the mixing effect.
4, various forms of inlet. Flow channel size ?0 14.0-7.0mm. Exhaust groove size 0.025-0.038mx 1.5mmx 4.0-6.0mm. Gate size 0.5TX2T.
5, the mold temperature is suitable for low temperature (20-40℃), the mold temperature is too high so that the crystallinity is large, the intermolecular interaction is strong, the products are good rigidity, good gloss, but softness. Poor transparency, shrinkage is also obvious.
6, polypropylene has good fluidity, low injection pressure can fill the cavity, too high pressure, easy to fly, but too low shrinkage will be serious. The injection pressure is generally 80-96mpa, and the holding pressure is about 80% of the injection pressure, which is suitable for compensation of longer holding pressure time.
7, polypropylene high degree of crystallinity, the barrel temperature is higher: temperature parameters: the temperature of the former barrel 200-240℃, the temperature of the middle barrel 170-220 ℃ after the barrel 160-190℃. Because of its forming temperature range, easy to shape. In practice, lower temperatures were used to reduce drape and shrinkage.