Low density polyethylene (LDPE)


Low density polyethylene refers to branched low density polyethylene (high pressure polyethylene). It uses oxygen (or air) or organic peroxide as a catalyst at 130 - 280MP. The high pressure and high temperature of 300 to 350 ° C, the bulk polymerization method, a polymer obtained by addition polymerization of high purity ethylene. By controlling the polymer temperature, changing the type of catalyst, adjusting the feed amount of the monomer, and the like, it is possible to manufacture polyethylenes of different types and properties.
The low density polyethylene has a crystallinity of about 40% to 65% and a softening point of 90 to 100 ° C, which is lower than that of high density polyethylene. Low-density polyethylene has better low-temperature resistance than high-density polyethylene. It can be used in severe winter and cold storage conditions. The film is relatively transparent, but the heat resistance and low creep resistance of low-density polyethylene are poor. Performance is also worse than HDPE, LLDPE.
LDPE has more stable chemical properties and better environmental stress crack resistance than HDPE. The LDPE film has low aging resistance, a low barrier to far infrared ray, and a low electrical conductivity. The LDPE film has good electrical insulation and is easy to generate static electricity. The volume resistivity of the conventional LDPE film is about CM, and the LDPE modified by the additive can also be made into an antistatic or conductive film.
LDPE has good molding processability and can be easily processed into films of various widths. It can be selected from the extrusion blown film method, the extrusion cast film method, the extrusion coating method, the dry composite method, the co-extrusion composite blown film or the co-extruded composite cast film method to produce a single layer or Multilayer film. Among various film forming methods, the extrusion blown film method (including the multilayer co-extrusion composite blown film method) is the most widely used molding method for producing LDPE films. It has the characteristics of simple equipment, low equipment cost, high productivity and wide applicability. It can manufacture films with a width of 16m and a thickness of l mm, as well as films with a width of 30mm and a thickness of 0.01mm. Other materials are harder to do. The heat sealing performance of the LDPE film is better, and the heat sealing temperature is lower than that of the LLDPE film. LDPE can also produce crosslinked or non-crosslinked heat shrinkable films.
The melt flow rate of the resin during molding of the LDPE film is an important parameter of the molding process. For different kinds of films, LDPE resin should be selected within a certain range of melt flow rate; in the production of LDPE film, LDPE resin or LDPE/LLDPE blending method with different melt flow rates is also used to appropriately change the film properties. Choose when manufacturing films for different purposes or different sizes.

  • 12/03/2019
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