HDPE is a kind of opaque white wax material, with a specific gravity of 0.941-0.960, which is lighter than that of water. It is soft and tough, but slightly harder than LDPE, and slightly elongated, nontoxic 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. When burning, it will melt, with liquid dripping, without black smoke. At the same time, it will emit the smell of paraffin combustion.
[main advantages]
Acid and alkali resistance, organic solvent resistance, excellent electrical insulation, and certain toughness can be maintained at low temperature. The surface hardness, tensile strength, rigidity and other mechanical strength of LDPE are higher than that of LDPE, close to that of PP, which is tougher than PP, but the surface finish is not as good as PP.
[main disadvantages]
Poor mechanical performance, poor ventilation, easy deformation, easy aging, easy brittleness, lower brittleness than PP, easy stress cracking, low surface hardness, easy scratching. It is difficult to print. When printing, it needs surface discharge treatment. It cannot be electroplated and the surface is lusterless.
[application]
Used for extruding packaging film, rope, woven bag, fishing net, water pipe; injection molding low-grade commodity and shell, non load bearing component, rubber box, turnover box; extrusion blow molding container, hollow product, bottle.
[injection molding process]
HDPE has a wide range of applications, ranging from reusable thin-wall beverage cups to 5-gsl cans, consuming 1 / 5 of HDPE produced in China. The general melt index of injection grade is 5-10, with lower toughness and higher processability. Applications include daily necessities and thin-walled food packaging; tough and durable food and paint cans; high resistance to environmental stress cracking applications, such as small engine fuel tanks and 90 gal garbage cans.
Generally, the melting point of HDPE is 142 ℃, the decomposition temperature is 300 ℃, and the injection temperature is adjustable. When injection molding, the general use temperature is 180 ℃ - 230 ℃; because it is alkene plastic, it does not absorb water, and does not need to be dried during production, but for the sake of product quality, it can be dried for 1H at 60 ℃ to discharge the floating water; the melt viscosity of polyethylene is large, the flow length ratio is small, and thin-walled products may lack glue, so the gate and flow channel are relatively large; the products are easy to carry static electricity, and the surface is easy to absorb. The shrinkage is 16 ‰ and the overflow value is 0.05mm.