Polyethylene (PE) is polymerized from ethylene monomers. The plastic made by granulating polyethylene resin with a small amount of plastic additives such as antioxidants and lubricants added as the base material is called polyethylene plastic.
Polyethylene is a high-density/(8 series) variety with multiple structures and characteristics that can be produced using multiple process methods. There are hundreds of varieties available. Currently, the most widely used varieties include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LL refractive index DPE), and some special performance varieties such as ultra-high molecular weight polyethylene (UHM WPE), low molecular weight polyethylene (LMWPE), high molecular weight high-density polyethylene (HMWHDPE), extremely low density polyethylene (VLDPE), cross-linked polyethylene stretching (VPE), chlorinated polyethylene (CPE), and various ethylene copolymers.
low density polyethylene
Low density polyethylene (LDPE) is polymerized using ethylene as a monomer and organic peroxides as initiators under high pressure of 100-300MP, hence it is also known as high-pressure polyethylene. The density ranges from 0.91 to 0.925g/cm3. Additionally, the density ranges from 0.926 to 0.940g/cm ³ It is called medium density polyethylene; A density below 0.910g/cm3 is called very low density polyethylene (VLDPE).
Performance characteristics
Low density polyethylene is a milky white waxy semi transparent solid particle, non-toxic and odorless, with a density range of 0.910~0.925g/cm3. Among polyethylene resins, it is the lightest variety except for ultra-low density polyethylene resin. Compared with high-density polyethylene, its crystallinity (55%~65%) and softening point (90~100 ℃) are lower; Has good flexibility, extensibility, transparency, cold resistance, and processability; Good chemical stability, can withstand acid, alkali, and salt aqueous solutions; Has good electrical insulation performance and breathability; Low water absorption; Easy to burn, emitting a gas with a smell of paraffin. The mechanical strength of low-density polyethylene is lower than that of high-density polyethylene, and its moisture permeability, heat resistance, oxidation resistance, and sunlight aging performance are poor. It is easy to age and decompose under sunlight or high temperature, resulting in color change and decreased performance. Therefore, when applying low-density polyethylene, antioxidants and UV absorbers should be added to improve its shortcomings. In addition, low-density polyethylene products have poor adhesion and printability. In order to improve their application in this area, the surface needs to undergo corona treatment or chemical corrosion before it can be applied.
Forming methods and applications
Low density polyethylene resin can be used to form plastic products through extrusion, injection, blow molding, and casting methods.
By using an extruder, products such as films, pipes, sheets, various profiles, and insulation protective layers for wires and wires can be extruded. In addition, the extrusion blow molding method can be used to form blow molded films, and to extrude hollow containers such as blow molded bottles and barrels.
Injection molding machines can be used to inject daily necessities, stationery, toys, and some industrial accessories.
In addition, extrusion coating and composite film are used to composite with paper, boards, and other plastic films to form packaging paper with moisture-proof function, which is used for packaging various items.
The rigidity, wear resistance, and breathability of medium density polyethylene are between low-density polyethylene and high-density polyethylene, and are generally only suitable for extruded pipes, lining films for cooking bags, and packaging films.
