Shenzhen WT Hardware and Plastics
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There are many methods of plastic film molding, which are more common in the three process of rolling, extruding and blowing. Three kinds of process film have characteristics, this article from the process principle, application field two aspects of finishing analysis.
Process principle Comparison
Film-forming method of flow extension
is a non-stretch, non-directional flat extrusion film produced by molten cast cold. There is no apparent orientation structure.
There is a common method of unidirectional stretching and bidirectional stretching, in which two-way stretching is a production approach which is concerned in recent years. The basic principle of bidirectional tensile technology is that the polymer raw materials are heated and melted into thick slices by extruding machine, and then in the appropriate temperature range below the melting point of glass temperature. Through the Ruianshi successively along the longitudinal and transverse stretch, so that the molecular chain in parallel to the film on the plane of the orientation and orderly arrangement, and then in the tension in the state of thermal stereotypes, so that the structure of the macromolecule fixed, the final cooling and subsequent treatment of film.
Blow molding Film
Usually extrusion blow molding manufacturing, plastic extrusion materials, forming tube billet blow molding, then cooling, traction, coiling. Blow molding is the orientation of the film.
From the above three kinds of process molding methods, the film has a significant difference in conductivity; At the same time the tensile film and the non-tensile film compared to the barrier performance, the gas permeability decreased, optical properties, transparency and surface gloss improve, the size of good temperature, thickness uniformity.
Application Field Comparison
Comparison of CPP, Bopp and ordinary pp film for example
Products with transparent, soft, barrier and mechanical adaptability, high-temperature cooking (cooking temperature at 120 ℃ above) Low Temperature heat seal (thermal seal temperature less than 125 ℃) and so on. Mainly used as food, candy, native products, cooked food (applicable to sterilization packaging), frozen products, condiments, soup and other composite packaging of the internal substrate, can prolong the shelf life of food, increase aesthetics. can also be used for the surface of stationery products, insulation, can also do auxiliary films, such as photographs and collections of leaflets, labels and so on.
With excellent printing performance, can be combined with paper, pet and other substrates, with high clarity and gloss, excellent ink absorption and coating adhesion, tensile strength, excellent grease barrier properties, low electrostatic characteristics, etc. It is widely used in the printing complex field, as well as the packaging material in tobacco.
Because of the simple process, low cost, but the optical performance is slightly lower than CPP and BOPP. Mainly used for dessert, bread, textiles, folders, record sets, sports shoes and other packaging.