Polyethylene
Thermoplastics > Polyolefins > Polyethylene
Classification of Polyethylene | |
In general, you can classify three different types of polyethylene according to the density they have, since this is a good indicator of the type of structure that the polymer has. Polyethylenes can be classified into classes according to density, following the ASTM D-4976 standard: Class 1 (0.910 to 0.925) = Low Density Polyethylene Class 2 (> 0.925 to 0.940) = Medium Density Polyethylene Class 3 (> 0.940 to 0.960) = High Density Polyethylene Class 4 (> 0.960) = High Density Polyethylene Low density polyethylene is a branched chain polymer. It is obtained by polymerization of ethylene at high pressures by the mechanism of free radicals. Low density polyethylene is divided into: Low density polyethylene Linear low density polyethylene Very low density polyethylene and Ethyl Vinyl Acetate | |
The main characteristics of the different types of polyethylenes are: LDPE (Low Density Polyethylene): due to its flexibility, easily processable, high chemical resistance and good insulating properties, this polyethylene is widely used for the extrusion of films and wires and cables, in addition to its use for blow molding and injection molding. LLDPE (Linear Low Density Polyethylene): it is a thermoplastic with high resistance of hot welding, being used mainly in the production of films for packaging, industrial and stretch film. MDPE (Medium Density Polyethylene): it has intermediate rigidity, being used mainly in the production of containers and in the production of embossed films for the production of disposable diapers and hygienic absorbers and, in the process of rotomolding, for the production of boxes of water, toys, tanks and tanks for chemical products and components for agricultural machines. HDPE (High density polyethylene): the natural color is milky white, semi-translucent according to the density. Good impact resistance and resistance to stress cracking. Good chemical resistance Good vapor barrier but poor barrier to gases. Sterilizable through EtO or gamma radiation. ULDPE (Ultra Baixa Density Polyethylene) The main use of ULDPE is as a modifying resin for high polyethylene (HDPE) and low density (LDPE) densities. The addition of PEUBD to polyethylenes improves the impact resistance, tear resistance of these polymers and flexibility at low temperature. UHMWPE (Ultra High Polyethylene Massa Molar) is a high density polyethylene, white and opaque, with a melting temperature of 135 ° C. The high density and the absence of branches in its structure that gives the UHMWPE resistance to abrasion greater than that of other thermoplastics, good resistance to corrosion, high resistance to cyclic fatigue, high resistance to impact fracture, high chemical resistance, high hardness and low coefficient of friction. | |