PE is Polyethylene, PE membrane is the most widely used polymer material in the world, which is made of ethylene polymerization. PE film is divided into high density polyethylene, medium density polyethylene and low density polyethylene. Low density polyethylene is soft and uses high pressure polymerization; high density polyethylene has the characteristics of rigidity, hardness and mechanical strength, and uses low pressure polymerization. High density polyethylene can be used as containers, pipes, and high frequency electrical insulation materials for radar and television. A large number of commonly used low density (high pressure) polyethylene. Polyethylene wax, wax like smoothness, no stain, low density polyethylene and high density polyethylene transparent, opaque polyethylene by ethylene (CH2=CH2) addition reaction and polymerization reaction, by repeated -CH2- unit connected to the polymer chain. The performance of polyethylene depends on its polymerization mode; Ziegler-Natta polymerization is carried out under the condition of medium pressure (15-30 ATM) organic compound catalysis, and the high density polyethylene (HDPE) is formed. Under these conditions, the polymerized polyethylene molecules are linear, and the molecular chain is very long, and the molecular weight is up to hundreds of thousands. If the polymerization is free radical polymerization under high pressure (100-300MPa) and high temperature (190 – 210 C), the low density polyethylene (LDPE), which is branched structure, is produced.
Polyethylene is not soluble in water, water is very small, is of some chemical solvents, such as toluene, acetic acid, and only at a temperature of 70 degrees Celsius above slightly dissolved. However, granular polyethylene can be melted or solidified at temperatures between 15 and ~40 degrees of temperature. When the temperature rises, it melts and absorbs heat; when the temperature is lowered, the heat is solidified and the heat is released. Because of its small water absorption, not easy to damp, insulation performance, so it is a very good building materials.
Characteristics and Application
LDPE (high pressure low density polyethylene): non-toxic, tasteless, odorless, translucent spherical or cylindrical particles, excellent resistance to low temperature, chemicals, with good elongation, electrical insulation, but poor humidity, flammable. Density: 0.910-0.9408G/CM3 (gram / cubic centimeter), suitable for extrusion, blister, injection molding, vacuum, molding, and transfer molding and other processing methods. The crystallinity is 55-65% and the melting point is 108-126.
HDPE (high density polyethylene): non-toxic, tasteless, odorless white powder or columnar or semicircle shaped particles, wear resistance, tolerable, watertightness, flammable, soft. The melting point is about 130, and the relative density is 0.941-0.965. It has good heat resistance and cold resistance. It has good chemical stability, high rigidity and toughness, good mechanical strength, dielectric property and good environmental stress cracking resistance.
Density: 0.941-0.9708G/CM3 (gram / cubic centimeter), purpose: mainly used for Blister molding, manufacturing a variety of bottles, cans, barrels, industrial storage tanks, hollow packaging.
LLDPE (linear low density polyethylene): odorless, odorless, non-toxic powder or particle, high hardness and anti-wear properties, good heat resistance and good thermal viscosity. Density: 0.91-0.940G/CM3 (gram / cubic centimeter); mainly used for making film, also for injection molding, blister. Compared with LDPE, it has the advantages of high strength, good toughness, strong rigidity, heat resistance, cold resistance, and has good environmental stress cracking resistance, tear strength and other properties, and can be acid, alkali, organic solvents, etc..
PE film is polyethylene plastic, stable chemical properties, usually made food bags and various containers, acid, alkali and salt water solution erosion, but should not be cleaned or soaked with strong alkaline detergent.
PE membrane is divided into high density, low density and linear PE, the most widely used is to make all kinds of plastic film and plastic cloth.
A medium density polyethylene pipe and PE pipe with high density polyethylene pipe. According to the wall thickness, they are divided into SDR11 and SDR17.6 series. The former is suitable for transporting gaseous artificial gas, natural gas and liquefied petroleum gas, and the latter is mainly used for transporting natural gas. Compared with steel pipe, the construction technology is simple, has certain flexibility, more important is not to do anti-corrosion treatment, will save a lot of process. The disadvantage is that the equipment is inferior to the steel pipe, and the construction pays special attention to the safety distance of the heating heating, and can not be exposed to the sunlight in the air, and is sensitive to chemicals, so as to prevent the leakage of the sewage pipe and cause harm. Specific gravity: 0.94-0.96 g / cm3; molding shrinkage: 1.5-3.6%; molding temperature: 140-220 C.
Material performance
Corrosion resistance, electrical insulation (especially high-frequency insulation) can be excellent, chlorination, irradiation modification, use of glass fiber reinforced polyethylene, melting point, hardness and rigidity, high strength, low water absorption, good electrical properties and radiation resistance; soft, high pressure polyethylene elongation, impact strength and good permeability; ultra high molecular weight polyethylene high impact strength, fatigue resistance, wear resistance, suitable for the production of low pressure polyethylene corrosion resistant parts and parts of high pressure polyethylene insulation; suitable for making films; ultra high molecular weight polyethylene is suitable for production of shock, abrasion and transmission parts.
Molding of release film
Crystalline material, moisture absorption is small, does not have to be fully dry, an excellent liquidity liquidity pressure sensitive, high pressure injection molding time, temperature uniformity, filling speed, holding pressure is sufficient, not by direct gate to prevent uneven shrinkage, stress increases, pay attention to the choice of gate location, to prevent the occurrence of shrinkage and deformation; contraction and contraction of the scope value, obvious direction, easily deformed, cooling slowly die with cold material, and a cooling system; the heating time should not be too long, otherwise it will decompose, burn; soft plastic parts with a lighter side of the groove, forcibly demoulding; likely melt broken, not with the organic solvent exposure, to prevent
