Polyolefins (polypropylene and polyethylene)

The polyolefins are homopolymers and copolymers of hydrocarbons containing one double bond in their molecules. The most used plastics not only among the polyolefins but also others are polyethylene and polypropylenes. Usually, they are delivered in form of granules. Doped and non-doped types are under manufacture, containing different additives that assure a protection during processing and prolongate the service life and modifies the performance.

At the test labs, we focus on the evaluation of the natural (without addition of artificial pigments) low-density polyethylene and polypropylene or its copolymers, respectively (thermoplastics, impact-resistant and random copolymers).

The low-density polyethylene (hereinafter “LD-PE”) is produced by the high-pressure polymerization of ethylene at the autoclave or tubular reactor in presence of peroxide initiators or modifiers. The particular LD-PE types are qualitatively different by basic parameters, e.g. density, molecular mass and processing characteristics.

The polypropylene (hereinafter “PP”) are usually produced using the Ziegler-Natta catalysts by a polymerization in the fluidized bed. The properties of the produced PP depend on the length of created chains, which is the molecular mass and its distribution, molecular and hyper-molecular structure, i.e. on the isotactical structures, the cristallinity degree and, as for copolymers, on the ethylene content, in particular. These structural characteristics are given through the applied polymerization technology and the type of catalytic complex. The PP may be produced using the controlled rheology, or as the reactor type without peroxide addition.

Typical tests for polyolefins