Plastic pipe equipment PE main molding conditions
Barrel temperature: barrel temperature is mainly related to the density of PE and the size of the melt flow rate, but also with the type and performance of the injection molding machine, the shape of the first level of plastic parts. As PE is a crystalline polymer, in the melt grain to absorb a certain amount of heat, so the barrel temperature should be higher than its melting point of 10 degrees. Degree of LDPE, barrel temperature control at 140 ~ 200 ℃, HDPE barrel temperature control at 220 ℃, the barrel back to take the minimum value, the front to take the maximum value.
Mold temperature: mold temperature has a greater impact on the crystalline condition of the plastic parts, high mold temperature, melt crystallinity, high strength, but shrinkage will also increase. Usually LDPE mold temperature control in 30 ℃ ~ 45 ℃, while the HDPE temperature is correspondingly high again 10 ~ 20 ℃.
Injection pressure: increase the injection pressure is conducive to the melt mold filling, due to the PE fluidity is very good, so in addition to thin-walled elongated products, it should be fine selection of lower injection pressure, the general injection pressure of 50 ~ 100MPa. shape is simple. After the wall of the larger plastic parts, the injection pressure can be lower, and vice versa is high.
Plastic Pipe Equipment
Plastic pipe equipment polyethylene PE molding processing performance
PE is a crystalline raw material, hygroscopicity is very small, not more than 0.01%, so there is no need for drying treatment before processing.
PE molecular chain of good flexibility, small inter-bond force, low viscosity of the melt, excellent fluidity, so no need for too high a pressure in the molding can be molded out of thin-walled long flow products.
PE shrinkage range, shrinkage value is large, the direction is obvious, LDPE shrinkage rate of 1.22% or so, HDPE shrinkage rate of 1.5% or so. Therefore, it is easy to deformation warping, mold cooling conditions have a great impact on the shrinkage rate, so it should control the mold temperature, keep the cooling uniform and stable.
PE's crystallization ability is high, the temperature of the mold has a very large impact on the crystallization of the plastic parts. Mold temperature is high, the melt cools slowly, the crystallinity of the plastic parts is high, and the strength is also high.
PE's melting point is not high, but the specific heat capacity is larger, so plasticizing still need to consume more heat, so the plasticizing device is required to have a larger heating power, in order to improve production efficiency.
PE softening temperature range is small, and the melt is easy to oxidize, so in the molding process should be avoided as far as possible to avoid contact between the melt and oxygen, so as not to reduce the quality of plastic parts.
PE parts are soft and easy to demold, so when the part has shallow side grooves, it can be strongly demolded.
The non-Newtonian nature of PE melt is not obvious, the change of shear rate has less effect on the viscosity, PE melt viscosity is also less affected by the temperature.
The cooling rate of PE melt is slow, so it must be cooled sufficiently. The mold should have a better cooling system.
If PE melt is injected with direct feed port feeding, it is easy to increase the stress and produce uneven search and direction of the obvious increase in deformation, so attention should be paid to the choice of feed port parameters.
PE molding temperature is wider, in the flow state, the temperature of the few fluctuations on the injection molding has no effect.
PE's thermal stability is better, generally below 300 degrees without significant decomposition phenomenon, there is little effect on the quality.
