High density polyethylene material properties

【English full name】High Density Polyethylene
[English abbreviation] HDPE
【Chinese full name】High density polyethylene
[Commonly known as] low pressure ethylene
【Composition monomer】Ethylene
[Basic characteristics] High-density polyethylene is an opaque white waxy material with a specific gravity lighter than water, with a specific gravity of 0.941~0.960. It is soft and tough, but slightly harder than LDPE and slightly stretchable. It is non-toxic and tasteless.
[Combustion Characteristics] It is flammable and can continue to burn after leaving the fire. The upper end of the flame is yellow and the lower end is blue. It will melt when burning, with liquid dripping and no black smoke coming out. At the same time, it emits the smell of burning paraffin.
[Main advantages] Resistant to acids and alkalis, organic solvents, excellent electrical insulation, and can still maintain a certain degree of toughness at low temperatures. The surface hardness, tensile strength, rigidity and other mechanical strengths are higher than LDPE, close to PP, and tougher than PP, but the surface finish is not as good as PP.
[Main Disadvantages] Poor mechanical properties, poor air permeability, easy to deform, easy to age, easy to become brittle, less brittle than PP, easy to stress crack, low surface hardness, easy to scratch. It is difficult to print. When printing, surface discharge treatment is required, electroplating is not allowed, and the surface is dull.
[Applications] Used for extruding packaging films, ropes, woven bags, fishing nets, water pipes; injection molding of low-end daily necessities and shells, non-load-bearing components, plastic boxes, turnover boxes; extrusion blow molding containers, hollow products, bottles.
[Injection Molding Process] HDPE has countless applications, ranging from reusable thin-walled beverage cups to 5-gsl cans, consuming 1/5 of domestically produced HDPE. Injection molding grades generally have a melt index of 5 to 10, and there are tough and low-fluidity grades and high-fluidity grades with processability. Uses include thin-wall packaging for household goods and food; tough, durable food and paint cans; and high environmental stress cracking resistance applications such as small engine fuel tanks and 90-gal garbage cans.
The general melting point of HDPE is 142°C and the decomposition temperature is 300°C; the injection molding temperature has a large adjustable range. When injection molding, the general operating temperature is 180℃-230℃; because it is an olefin plastic, it does not absorb water and does not need to be dried during production. However, for the sake of product quality, it can be dried at 60℃ for 1 hour to discharge floating water; polyethylene The melt viscosity is high and the flow length ratio is small. Thin-walled products may lack glue. Therefore, the gates and flow channels are relatively large; the products are prone to static electricity and the surface is easy to absorb angstroms. The shrinkage rate is 16‰ and the overflow value is 0.05mm.