Views: 67 Author: Site Editor Publish Time: 2019-03-21 Origin: Site
Both PP and PE are saturated hydrocarbons, which are similar in many respects, but differ in some important properties. In addition to ultra high molecular weight polyethylene, PP has a higher melting point and glass transition temperature than PE, but PP requires a higher processing temperature.
Polyethylene is abbreviated as PE, which is a thermoplastic resin obtained by polymerization of ethylene. Industrially, copolymers of ethylene and a small amount of an α-olefin are also included. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -70 ~ -100 °C), good chemical stability, and can resist most acid and alkali corrosion (not resistant to oxidizing properties) The acid is insoluble in common solvents at normal temperature, has low water absorption and excellent electrical insulation properties; however, polyethylene is very sensitive to environmental stress (chemical and mechanical action) and has poor heat aging resistance. The nature of polyethylene varies from species to species and depends primarily on molecular structure and density. Products of different densities (0.91 to 0.96 g/cm3) can be obtained by different production methods. Polyethylene can be processed by conventional thermoplastic molding methods (see plastic processing). It is widely used in the manufacture of films, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulation materials for televisions, radars, etc.
Polypropylene, abbreviated as PP, is a thermoplastic resin obtained by polymerizing propylene. There are three configurations of isotactic, random and syndiotactic, and industrial products are mainly composed of isotactics. Polypropylene also includes copolymers of propylene and a small amount of ethylene. Usually a translucent, colorless solid, odorless and non-toxic. Due to the regular structure and high crystallization, the melting point is as high as 167 ° C, heat resistance, steam sterilization of products can be 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 is poor in low temperature impact resistance and easy to age, but can be overcome by modification and addition of antioxidants.
The same: 1. PE, PP uncolored are all milky white translucent, waxy polymer. 2. Both are non-polar crystalline polymers with good compatibility. 3. Non-toxic, good chemical stability, easy to shape and process. 4. Poor weather resistance.
The difference: 1. PP has better rigidity, strength and heat resistance than PE, and PE is easily decomposed by photooxidation, thermal oxidation and ozone. 2. PP density is smaller than PE, and PP density is only 0.90~0.91g/cm3. 3. PP toughness is poor at low temperatures
