Polypropylene applications biaxially oriented

Low density polyethylene is the most common film material in use today, although the new development of paper-like high density polyethylene films promises to be an area of large expansion. Films are also extruded from polypropylene (mainly biaxially oriented), PVC, nylon and polyester. The main application for polyethylene film is in packaging but considerable quantities of film are also used in building, industrial sacks and many other applications. 

Polystyrene films and polyester (polyethylene terephthalate) films are only used in the biaxially stretched form, because unstretched films are very weak and brittle. To a lesser extent this is also true for polypropylene films. Roll-quenched flat film is used for many packaging applications, but below 0°C these films become brittle. Biaxially oriented polypropylene film, on the other hand, is not brittle at a temperature as low as — 50°C and is suitable for packaging frozen foods. 

The optical properties, clarity and gloss, are also improved and biaxially oriented polystyrene and polypropylene films are used for envelope windows and overwraps. Biaxially oriented polyvinylidene chloride film is also used for food packaging in view of its good mechanical and optical properties, but for economic reasons it is only used if its low permeability to gases, especially oxygen, is required. The electrical properties are improved by biaxial orientation and the applications of polyester, polycarbonate and polypropylene films in capacitors are expected to show a rapid growth. In these electrical applications crystalline films are always annealed in order to improve the dimensional heat stability. 

ASTM D2673 provides a standard specification for oriented polypropylene film, and similarly ASTM D3664 provides a specification for biaxially oriented polyethylene terephthalate film for electrical applications. 

Polypropylene is generally used as oriented polypropylene. Polyvinyl chloride film is commonly used in plasticized form. Polyvinylidene chloride is often known as Saran and is generally used in copolymer form with acrylonitrile. Polyethylene terephthalate is a thermoplastic polyester. Polystyrene is sometimes used in biaxially oriented form. Polycarbonates, polysulfones, polyether sulfones, poly-imides, polyetherimides, and several fluoropolymers are also used for specialty applications. 

Biaxially oriented polymer sheet is now widely used in packaging. High- and low-density polythene are common and recently polypropylene has become a popular film material. Polypropylene film of this type is often laminated with polyester and aluminium and with polyester or nylon. Relatively thick oriented sheet PET is also being assessed for applications in automobile body panels. 

There are many applications for polyolefin compounds in the processing of pipes, tubings, and fittings from polyethylene (PE), crosslinked polyethylene (XPE), biaxially oriented polyethylene (PEO), polypropylene, and polybutylene. 

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