Polyethylene and Polypropylene（Introduction）

The main raw material for foreign production is polyethylene (PE), and domestic production is mainly polypropylene (PP), which is a thermoplastic resin obtained by polymerization of ethylene.

Polyethylene (PE)

Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum operating temperature can reach -70 ~ -100 ℃), good chemical stability, and can resist the erosion of most acids and alkalis (not resistant to oxidation properties). acid), insoluble in general solvents at room temperature, low water absorption, and excellent electrical insulation performance; but polyethylene is very sensitive to environmental stress (chemical and mechanical effects) and has poor heat aging resistance. The properties of polyethylene vary from variety to variety, mainly depending on the molecular structure and density. Different production methods can be used to obtain products with different densities (0.91-0.96g/cm3). Polyethylene can be processed by the usual thermoplastic molding methods (see Plastics Processing). It has a wide range of uses, mainly used to manufacture films, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulating materials for TVs, radars, etc. With the development of petrochemical industry, polyethylene production has developed rapidly, and the output accounts for about 1/4 of the total plastic output. In 1983, the world’s total polyethylene production capacity was 24.65Mt, and the capacity of the units under construction was 3.16Mt.

Polypropylene (PP)

A thermoplastic resin obtained by the polymerization of propylene. There are three configurations of isotactic, random and syndiotactic, and industrial products are mainly composed of isotactic. Polypropylene also includes copolymers of propylene with small amounts of ethylene. Usually translucent colorless solid, odorless and nontoxic. Due to the regular structure and high crystallization, the melting point is as high as 167 ° C, heat resistance, and the products can be sterilized by steam, which are its outstanding advantages. With a density of 0.90g/cm3, it is the lightest general-purpose plastic. Corrosion resistance, tensile strength 30MPa, strength, rigidity and transparency are better than polyethylene. The disadvantage is that it has poor low temperature impact resistance and is easy to age, but it can be overcome by modification and addition of antioxidants.

The color of woven bags is generally white or off-white, non-toxic and tasteless, and generally less harmful to the human body. Although they are made of various chemical plastics, they are environmentally friendly and have greater recycling efforts; woven bags are widely used. , mainly used for packaging and packaging of various items, and is widely used in industry; plastic woven bags are made of polypropylene resin as the main raw material, which is extruded and stretched into flat yarns, and then woven and bagged. 

The composite plastic woven bag is made of plastic woven cloth as the base material and compounded by the casting method. For packaging powdered or granular solid materials and flexible items.

Composite plastic woven bags are divided into two-in-one bags and three-in-one bags according to the main material.