Use of plastic
Plastic crucibles are widely used in agriculture, industry, construction, packaging, defense industry and people's daily life of plastic bags, plastic mesh, plastic barrels, plastic molds, plastic bottles and other fields.
Agriculture: A large number of plastics are used to make mulch, seedling films, greenhouse membranes, irrigation and drainage pipes, fishing nets, and culture floats.
Industry: Electrical and electric power are widely used in industry to make insulating materials and packaging materials; In the machinery industry, transmission gears, bearings, bearings and many parts and components are used to replace metal products; in the chemical industry, plastic is used as the pipeline, each Containers and other anti-corrosion materials; doors and windows in the construction industry, stair handrails, floor tiles, ceilings, heat-insulating panels, wallpapers, falling water fittings and pit tubes, decorative panels, and sanitary ware.
Buy plastic trays should choose a good manufacturer
In the defense industry and cutting-edge technologies, plastics are indispensable materials for conventional weapons, aircraft, ships, rockets, missiles, artificial satellites, spacecraft, and the atomic energy industry.
Agriculture: A large number of plastics are used to make mulch, seedling films, greenhouse membranes, irrigation and drainage pipes, fishing nets, and culture floats.
Industry: Electrical and electric power are widely used in industry to make insulating materials and packaging materials; In the machinery industry, transmission gears, bearings, bearings and many parts and components are used to replace metal products; in the chemical industry, plastic is used as the pipeline, each Containers and other anti-corrosion materials; doors and windows in the construction industry, stair handrails, floor tiles, ceilings, heat-insulating panels, wallpapers, falling water fittings and pit tubes, decorative panels, and sanitary ware.
Buy plastic trays should choose a good manufacturer
In the defense industry and cutting-edge technologies, plastics are indispensable materials for conventional weapons, aircraft, ships, rockets, missiles, artificial satellites, spacecraft, and the atomic energy industry.
In people's daily life, plastics are more widely used, such as plastic sandals, slippers, raincoats, handbags, children's toys, toothbrushes, soap boxes, hot water bottle shells, and the like, which are marketed on the market. At present, various home appliances such as televisions, tape recorders, fans, washing machines, refrigerators, etc. have also been widely used.
As a new type of packaging material, plastic has been widely used in the field of packaging, such as various plastic bags, plastic nets, plastic barrels, plastic molds, hollow containers for plastic bottles, injection containers (turnover boxes, containers, barrels, etc.), packaging Films, woven bags, corrugated boxes, foams, tying ropes, strapping belts, etc.
concept
Common common plastics generally refer to homopolymers and copolymers of ethylene, propylene, butylene.
Main varieties: LDPE, LLDPE, MDPE, HDPE, UHMWPE, CPE, ethylene-propylene copolymers (plastics), EVA, ethylene-butene copolymers, copolymers of ethylene-other olefins (such as octene, cycloolefins), ethylene -Unsaturated ester copolymers (EMA, EEA, EAA); PP, CPP; poly(1-butene); poly(4-methylpentene-1) (transparent material, impact resistant, medical).
Among them, the largest output: PE (LDPE, LLDPE, HDPE) and PP.
Polyethylene (PE) Poly(ethylene)
What is polyethylene
Polyethylene is the most simple polymer, and it is also the most widely used polymer material.
It is made up of repeating –CH2– units. Polyethylene is formed by the addition polymerization of ethylene (CH2=CH2).
It is made up of repeating –CH2– units. Polyethylene is formed by the addition polymerization of ethylene (CH2=CH2).
The properties of polyethylene depend on how it is polymerized. Under medium pressure (15-30 atmospheres), Ziegler-Natta polymerization under the catalysis of organic compounds is high density polyethylene (HDPE). Under these conditions, the polymerized polyethylene molecules are linear, and the molecular chains are long and have a molecular weight of several hundred thousand. If it is under high pressure (100-300 MPa), high temperature (190-210 °C), peroxide catalyzed free radical polymerization, the production of low density polyethylene (LDPE), which is a branched structure.
Polymerization pressure: high pressure, medium pressure, low pressure;
Polymerization 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, normal molecular weight, ultra high molecular weight.
Polyethylene characteristics
Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -70～-100°C), good chemical stability, resistance to most of the acid and alkali corrosion (intolerance has oxidation properties The acid) is insoluble in common solvents at room temperature, has low water absorption, and is excellent in electrical insulation; but polyethylene is very sensitive to environmental stress (chemical and mechanical) and has poor heat aging resistance.
The nature of polyethylene varies from species to species, depending on the molecular structure and density.
Types of polyethylene
(1) LDPE: low-density polyethylene, high-pressure polyethylene
(2) LLDPE: linear low density polyethylene
(3) MDPE: Medium Density Polyethylene, Bimodal Resins
(4) HDPE: high density polyethylene, low pressure polyethylene
(5) UHMWPE: UHMWPE
(6) Modified Polyethylene: CPE, Crosslinked Polyethylene (PEX)
(7) Ethylene copolymers: ethylene-propylene copolymers (plastics), EVA, ethylene-butene copolymers, copolymers of ethylene-other olefins (such as octene POE, cycloolefins), ethylene-unsaturated ester copolymers ( EAA, EMAA, EEA, EMA, EMMA, EMAH)
Linear polyethylene having a molecular weight of 3,000,000 to 6,000,000 is called Ultra High Molecular Weight Polyethylene (UHMWPE). Ultra-high molecular weight polyethylene is very strong and can be used as a body armor.
The main method:
Liquid-phase method (divided into solution method and slurry method) and gas-phase method (phase type of material in the reactor). China mainly uses Ziegler catalyst slurry method.
Liquid-phase method (divided into solution method and slurry method) and gas-phase method (phase type of material in the reactor). China mainly uses Ziegler catalyst slurry method.
Conditions and Process Description: Ethylene with a purity of 99% or more is polymerized in the presence of a catalyst of titanium tetrachloride and diethylaluminum monochloride in a gasoline having a pressure of 0.1-0.5 MPa and a temperature of 65-75°C to obtain HDPE slurry. The residual catalyst was destroyed by alcoholysis, neutralized, washed with water, and gasoline and unpolymerized ethylene were recovered, dried, and granulated to obtain a product.
Polypropylene Poly(propylene)
(1) Production Process of Polypropylene (PP) Polypropylene is composed of propylene, CH2=CHCH3, polymerized by ZN metal catalyst.
(2) Production method of polypropylene (PP) 1 Slurry method. Polymerization in diluents such as hexane is the earliest industrialized and also the most productive method ever produced.
2 liquid phase bulk method. Polymerization in liquid propylene at 70°C and 3 MPa.
3 gas phase method. The polymerization takes place under the gaseous conditions of propylene. The latter two methods do not use thinner, the process is short, and the energy consumption is low. Liquid-phase mass spectrometry has now shown its advantages of being the first to come. Gas-phase methods are also rapidly developing.
2 liquid phase bulk method. Polymerization in liquid propylene at 70°C and 3 MPa.
3 gas phase method. The polymerization takes place under the gaseous conditions of propylene. The latter two methods do not use thinner, the process is short, and the energy consumption is low. Liquid-phase mass spectrometry has now shown its advantages of being the first to come. Gas-phase methods are also rapidly developing.
Polypropylene classification
According to the structure, it is divided into isotactic polypropylene and atactic polypropylene.
The commonly used polypropylene is isotactic polypropylene.
PP characteristics
Its molecular structure is similar to polyethylene, but the carbon atoms on the carbon chain have a methyl group (–CH3). Polypropylene is slightly more brittle than polyethylene and has a melting temperature of 160°C.
Usually translucent colorless solid, odorless and non-toxic.
Because of the regular structure and high degree of crystallization, the melting point of up to 167 °C, heat, steam sterilization products is its outstanding advantages.
Density 0.90g/cm3, is the lightest universal plastic.
Corrosion resistance, tensile strength 30MPa, strength, rigidity and transparency are better than polyethylene.
The disadvantages are poor low-temperature impact resistance and easier aging, but they can be overcome by modification and addition of antioxidants, respectively.
Usually translucent colorless solid, odorless and non-toxic.
Because of the regular structure and high degree of crystallization, the melting point of up to 167 °C, heat, steam sterilization products is its outstanding advantages.
Density 0.90g/cm3, is the lightest universal plastic.
Corrosion resistance, tensile strength 30MPa, strength, rigidity and transparency are better than polyethylene.
The disadvantages are poor low-temperature impact resistance and easier aging, but they can be overcome by modification and addition of antioxidants, respectively.