HDPE plastic properties and applications
Chemical name: high density polyethylene
Typical applications: refrigerator containers, storage containers, household kitchen , commodity plastic product,medical plastic device ,sealing and so on.
Injection molding process conditions: dry: if the storage is appropriate without drying.
Melting temperature: 220 ~ 260℃. For larger materials, the proposed melting temperature range between 200 ~ 250℃.
Mold temperature: 50 ~ 95℃. 6mm below the wall thickness of the plastic parts should use a higher mold temperature, 6mm or more wall thickness of the plastic parts using a lower mold temperature. The cooling temperature of the plastic parts should be uniform to reduce the difference in shrinkage. For the optimum machining cycle time, the diameter of the cooling channel should be not less than 8 mm and the distance from the mold surface should be within 1.3 d (where "d" is the diameter of the cooling cavity).
Injection pressure: 700 ~ 1050bar.
Injection speed: high speed injection is recommended.
Runner and gate: the flow path diameter between 4 to 7.5mm, the length of the flow channel should be as short as possible. You can use various types of gate, gate length should not exceed 0.75mm. Particularly it is suitable for use with hot runner molds.
Chemical and physical properties: The high crystallinity of PE-HD results in its high density, tensile strength, high temperature twist temperature, viscosity and chemical stability. PE-HD has a stronger resistance to permeability than PE-LD. PE-HD has low impact strength. PH-HD characteristics are mainly controlled by density and molecular weight distribution. The PE-HD molecular weight distribution for injection molds is very narrow. For the density of 0.91 ~ 0.925g / cm3, we call the first type of PE-HD; for the density of 0.926 ~ 0.94g / cm3, known as the second type of PE-HD; for the density of 0.94 ~ 0.965g / cm3 , Known as the third type of PE-HD. The flow characteristics of the material are very good and the MFR is between 0.1 and 28. The higher the molecular weight, the worse the flow characteristics of the PH-LD, but with better impact strength. PE-LD is a semi-crystalline material, after molding shrinkage is high, between 1.5% to 4%. PE-HD is prone to environmental stress cracking. The cracking can be mitigated by using materials with very low flow characteristics to reduce internal stresses. PE-HD is easy to dissolve in hydrocarbon solvents when the temperature is higher than 60C, but its solubility is better than PE-LD.
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