Because plastics have many of the above advantages, new plastics have also been continuously researched and developed, with various properties such as engineering plastics or polymer plastics. High-molecular polymers are high-molecular-weight compounds that contain a covalent bond as a binding atom or a binding force between molecules. In general, a molecular weight of 1,000 or more can be referred to as a polymer. In nature, natural rubber, protein, cellulose, starch, and asbestos are all high molecular substances.
The polymer is formed by the bonding of monomers. Usually, the structural unit is used to describe the structure of the polymer, and the structural units have different arrangement and connection methods, such as a linear polymer, whose structural units are The arrangement on the chain is X -(M)n -Y, where M is a structural unit, ie, a monomer, and n is a degree of polymerization, abbreviated as dp. When n is 2, they are called dimers. When n is 3, they are called trimers. When n is 4, they are called tetramers. The number of n can reach as many as 10 million. About two ends of a structural unit M are linked by X and Y, and X and Y may be the same or different. Polymers that contain the same repeating units are called homopolymers, such as polyethylene. Polymers containing two or more structural units, called copolymers. The polymerization forms include addition polymerization, condensation polymerization and combination polymerization.
In general, commonly used plastic printed materials can include the following:
1. Polyethlene
Referred to as PE, it is the most extensive plastic. The main raw material of polyethylene is ethylene. Can make use of the thermal cracking of pentane to produce ethylene: Pentane pressure cracking, available ethane and propylene, ethane and then dehydrogenation reaction can be ethylene. Its main products are polyethylene lids, cutlery, kitchen supplies, toys and lighting parts.
Polyethylene can be divided into two types, low density polyethylene and high density polyethylene. Low-density polyethylene, with a molecular weight of 50,000 to 300,000, a density of about 0.92 g/cm3 of high-density ethylene, a molecular weight of up to 3 million, and a density of about 0.96 g/cm3, can be understood from Table 6 for the physical properties of polyethylene.
1800 ~ 2000
In general, commonly used plastic printed materials can include the following:
1. Polyethlene
Referred to as PE, it is the most extensive plastic. The main raw material of polyethylene is ethylene. Can make use of the thermal cracking of pentane to produce ethylene: Pentane pressure cracking, available ethane and propylene, ethane and then dehydrogenation reaction can be ethylene. Its main products are polyethylene lids, cutlery, kitchen supplies, toys and lighting parts.
Polyethylene can be divided into two types, low density polyethylene and high density polyethylene. Low-density polyethylene, with a molecular weight of 50,000 to 300,000, a density of about 0.92 g/cm3 of high-density ethylene, a molecular weight of up to 3 million, and a density of about 0.96 g/cm3, can be understood from Table 6 for the physical properties of polyethylene.
1800 ~ 2000
2. Polypropylene
Polypropylene is produced in the same way as polyethylene, with titanium trichloride and triethylaluminum, tributylaluminum or diethylaluminum chloride as catalysts, dispersed in a solvent and reacted at 10 atm. Polypropylene is slurried, soluble in ethanol, dried after processing.
Polypropylene is harder than polyethylene, has a high softening point and is brittle at low temperatures. The molecular weight is between 80,000 and 150,000, with a specific gravity of 0.90 to 0.91. Related products include the manufacture of silk fibers, transportation equipment, laboratory glass, dropper and injection molding products.
3. Polyvinyl chloride (PVC)
The Chinese name is polyvinyl chloride, and its material properties are high in specific gravity and flame resistance. With high transparency. Good insulation. Good printability. Different formulations have different characteristics and are widely used. Cheap. When the processing temperature exceeds 190°C, cracking occurs and HCL gas is released. Great environmental impact. Molecular weight between 60000 and 150000, with good electrical resistance, fire resistance and so on. Related products include wire and cable jackets, raincoats, and curtains. Addition of additives can make records.
(to be continued)