March 3, 2024
| Scientific name | High density polyethylene, low pressure polyethylene. |
| monomer | Ethylene - a gas produced in petroleum refining. |
| Colour | High density polyethylene (HDPE) is an opaque white waxy material that is lighter in weight than water, soft and resilient, but slightly harder than LDPE and can also elongate slightly. It is non-toxic and odorless |
| Combustion characteristics | Flammable, can continue to burn after leaving the flame. The upper end of the flame is yellow and the lower end is blue. It will melt during combustion, with liquid droplets and no black smoke coming out. At the same time, it emits the odor of paraffin burning. |
| Advantages | Acid and alkali resistance, organic solvent resistance, excellent electrical insulation, and can still maintain a certain degree of toughness at low temperatures. The mechanical strength such as surface hardness, tensile strength, and rigidity are higher than LDPE, close to PP, and tougher than PP, but the surface smoothness is not as good as PP. |
| Disadvantages | Poor mechanical performance, poor air permeability, easy deformation, easy aging, easy brittleness, lower brittleness than PP, easy stress cracking, low surface hardness, and easy scratching. Difficult to print, surface discharge treatment is required during printing, electroplating is not allowed, and the surface is dull. |
| Injection molding performance | The general melting point of HDPE is 142 ℃, and the decomposition temperature is 300 ℃. The adjustable range of injection temperature is relatively large. During injection molding, the general operating temperature is between 180 ℃ and 230 ℃. As it is an olefinic plastic, it does not absorb water and does not need to be dried during production. However, for product quality, it can be dried at 60 ℃ for 1 hour to discharge floating water. Polyethylene has a high melt viscosity and a low flow length ratio, and thin-walled products may lack adhesive. Therefore, the gate and runner are relatively large. The product is prone to static electricity and the surface is prone to dust absorption. The shrinkage rate is 16 ‰. The overflow value is 0.05mm. |
| Applications |
Used for extruding packaging films, ropes, woven bags, fishing nets, water pipes, for injection molding low-grade daily necessities and shells, non load bearing components, rubber boxes, turnover boxes, used for extrusion blow molding containers, hollow products, bottles. |
