PE-HD (high-density polyethylene)

plastic-raw-materials

PE-HD (high-density polyethylene)



Typical Applications:

Containers (refrigerator containers, storage containers, household kitchen utensils), building materials (shutters, synthetic wood, synthetic paper, synthetic films, decorative boards, pipes,  calcium molded products), industrial accessories, medical supplies, toys, shells, bottle plugs, protective covers, sealing covers, films, stretch strips, bundling belts, single wires, wire and cable sheaths, etc.


Injection Molding Process Conditions:

Drying treatment: unnecessary if stored properly.

Melting temperature: 220 ~ 260. For larger-molecular materials, it is recommended that the melting temperature range between 200 ~ 250.

Mold temperature: 50 ~ 95. Making plastic parts with a wall thickness below 6mm needs a higher mold temperature, while making of plastic parts with a wall thickness above 6mm needs a lower mold temperature. The cooling temperature of the plastic parts should be uniform to reduce the difference of shrinkage rate. For the optimal machining cycle time, the diameter of the cooling cavity shall not be less than 8mm, and the distance from the mold surface shall be within 1.3d (" d "is the diameter of the cooling cavity).

Injection pressure: 700~1050 bar.

Injection speed: high speed injection is recommended.

Runner and pouring gate: If the runner diameter is between 4 mm and 7.5mm, the runner length should be as short as possible. Various types of pouring gates may be used and the pouring gate length shall not exceed 0.75mm. PE-HD is suitable for the use of hot runner mold.

 

Chemical and Physical Properties:

The high degree of PE-HD’s crystallinity results in its high density, tensile strength, distortion temperature, viscosity and chemical stability. PE-HD has stronger permeability than PE-LD. PE-HD has low impact resistance. PE-HD’s properties are primarily controlled by its density and molecular weight distribution. The molecular weight distribution of PE-HD suitable for injection molding is very narrow. For density of 0.91~ 0.925g/cm3, we call it PE-HD of the Type I. For the density of 0.926~ 0.94g/cm3, we call it the Type II. For density of 0.94~ 0.965g/cm3, we call it the Type III. The material has good flow characteristics with its MFR between 0.1 and 28. The higher the PE-LD’s molecular weight, the worse its flow performance, and the better its impact resistance. PE-LD is a semi-crystalline material with a high shrinkage of 1.5% to 4% after molding. PE-HD is prone to cracking due to environmental stress. Cracking can be reduced by using materials with very low flow performance to reduce the internal stress. PE-HD is easy to dissolve in the hydrocarbon solvents when the temperature rises above 60, but its resistance to dissolve proves better than PE-LD.


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