EPE
EPE is also called pearl cotton. Polyethylene foamed cotton has a non-cross-linked obturator structure and is a new type of environmentally friendly packaging material. It is composed of low-density polyethylene grease that is physically foamed to produce countless independent bubbles. It overcomes the shortcomings of ordinary foam rubber such as brittleness, deformation and poor recovery. It has many advantages such as water and moisture proof, shockproof, sound insulation, heat preservation, good plasticity, strong toughness, recycling, environmental protection, strong impact resistance, etc. It also has good chemical resistance. It is an ideal substitute for traditional packaging materials. Widely used in electronic appliances, instruments, computers, audio, medical equipment, industrial control cases, lighting, handicrafts, glass, ceramics, home appliances, spray painting, furniture, wine and gift packaging, hardware products, toys, fruits, and leather shoes. Packaging, daily necessities and other products packaging. After adding antistatic agent and flame retardant, its excellent performance is even more obvious.
EPE pearl cotton is also widely used in elastic linings of handbags and luggage, industrial sound insulation and heat insulation materials, agricultural insulation materials, aquaculture floating equipment, protective pads for sporting goods, and life-saving equipment for water operations. , floor decoration, padding, etc. in homes and hotels. Its pipes are widely used in air conditioners, strollers, children's toys, furniture and other industries.
Adhesive products of EPE and various fabrics are good interior decoration materials for various vehicles and homes. The composite product of EPE and aluminum foil or aluminum-plated film has excellent anti-infrared ultraviolet capabilities and is a substitute for some chemical equipment refrigerators and camping equipment car sunshades.
Polyethylene
Polyethylene is the simplest polymer and the most widely used polymer material.
It is formed by joining repeated –CH2– units. Polyethylene is formed by the addition polymerization of ethylene (CH2=CH2).
The properties of polyethylene depend on how it is polymerized. High-density polyethylene (HDPE) is produced by Ziegler-Natta polymerization under moderate pressure (15-30 atmospheres) under organic compound catalysis. The polyethylene molecules polymerized under such conditions are linear and have very long molecular chains with molecular weights as high as hundreds of thousands. If free radical polymerization is performed under high pressure (100-300MPa), high temperature (190-210°C), and peroxide catalysis, low-density polyethylene (LDPE) is produced, which has a branched structure.
Polymerization pressure: high pressure, medium pressure, low pressure;
Polymerization implementation method: slurry method, solution method, gas phase method;
Product density: High density, medium density, low density, linear low density;
Product molecular weight: low molecular weight, ordinary molecular weight, ultra-high molecular weight.
Characteristics of polyethylene
Polyethylene is odorless, non-toxic, feels like wax, and has excellent low-temperature resistance (the lowest operating temperature can reach -70~-100℃). It has good stability, can resist the erosion of most acids and alkalis (not resistant to acids with oxidizing properties), is insoluble in general solvents at room temperature, has low water absorption, and has excellent electrical insulation properties; but polyethylene is resistant to environmental stress (chemical and mechanical effects). Very sensitive and has poor heat aging resistance.
The properties of polyethylene vary from species to species and mainly depend on molecular structure and density.
Types of polyethylene
(1) LDPE: low density polyethylene, high pressure polyethylene
(2) LLDPE: linear low density polyethylene
p>(3) MDPE: medium density polyethylene, bimodal resin
(4) HDPE: high density polyethylene, low pressure polyethylene
(5) UHMWPE: Ultra-high molecular weight polyethylene
(6) Modified polyethylene: CPE, cross-linked polyethylene (PEX)
(7) Ethylene polymer: ethylene-propylene* Polymers (plastics), EVA, ethylene-butylene polymers, ethylene-other olefin (such as octene POE, cyclic olefins) polymers, ethylene-unsaturated ester polymers (EAA, EMAA, EEA, EMA, EMMA, EMAH)
Linear polyethylene with a molecular weight of 3,000,000-6,000,000 is called ultra-high molecular weight polyethylene (UHMWPE). Ultra-high molecular weight polyethylene is very strong and can be used as body armor.
Main methods:
Liquid phase method (also divided into solution method and slurry method) and gas phase method (phase state type of materials in the reactor). Our country mainly uses the slurry method of Ziegler catalyst.
Conditions and process description: Ethylene with a purity of over 99 is polymerized in the presence of catalysts titanium tetrachloride and diethyl aluminum monochloride in gasoline at a pressure of 0.1-0.5MPa and a temperature of 65-75°C. HDPE slurry. After alcoholysis, the residual catalyst is destroyed, neutralized, washed with water, and gasoline and unpolymerized ethylene are recovered. The product is obtained through drying and granulation.
Chemical name: Polyethylene
English name: Polyethylene (PE for short)
Specific gravity: 0.94-0.96 g/cubic centimeter Molding shrinkage: 1.5-3.6 Molding temperature: 140-220℃
Features: corrosion resistance, excellent electrical insulation (especially high-frequency insulation), can be modified by chlorination, chemical cross-linking, radiation cross-linking, and glass fiber can be used Reinforcement. Low-pressure polyethylene has higher melting point, rigidity, hardness and strength, low water absorption, good electrical properties and radiation resistance; high-pressure polyethylene has better softness, elongation, impact strength and permeability; ultra High molecular weight polyethylene has high impact strength, fatigue resistance, and wear resistance. Low-pressure polyethylene is suitable for making corrosion-resistant parts and insulating parts; high-pressure polyethylene is suitable for making films, etc.; ultra-high molecular weight polyethylene is suitable for making shock absorption, wear-resistant and Transmission parts.
Molding characteristics:
1. Crystalline material, low moisture absorption, does not need to be fully dried, excellent fluidity. The fluidity is sensitive to pressure, so high-pressure injection is suitable for molding. The temperature is uniform, the filling speed is fast, and the pressure is sufficient. It is not suitable to use direct gate to prevent uneven shrinkage and increased internal stress. Pay attention to the location of the gate to prevent shrinkage holes and deformation.
2. The shrinkage range and value are large, the directionality is obvious, and it is easy to deform and warp. The cooling speed should be slow, the mold should be equipped with a cold material cavity and a cooling system.
3. The heating time should not be too long, otherwise it will happen Decompose.
4. When soft plastic parts have shallow side grooves, they can be forcibly demoulded.
5. Melt rupture may occur and should not be in contact with organic solvents. To prevent cracking