The history of this material began abroad in the middle of the last century,. It was used for packaging food products. Technical film was the result of multiple modifications of the chemical composition and release technologies, which provided it with a wide range and a high level of use.
Composition
Properties possessed by technical polyethylene film and its purpose depend on composition:
- High Density Polyethylene (LDPE).
- High Density Polyethylene (HDPE).
- Linear LDPE with modified composition.
- Compound variations: for example, LDPE and HDPE, with polypropylene.
Specifications
Polyethylene is non-toxic, belongs to the group of flammable non-toxic materials with an ignition temperature of 300°C, other characteristics depend on the composition:
Polyethylene film lowpressure:
- Mechanically strong material (0.94÷0.96 g/cm2).
- Resistant to high temperatures (flow rate at 112 C°).
- Resistant structure to edible fats, oils. Neutral to acidic and alkaline substances.
- The disadvantage is a high level of permeability, almost 6 times higher than the VD film. Contact with hydrocarbons is unacceptable and undesirable - with easily oxidizing substances.
- Technical film based on low pressure polyethylene is indispensable for packaging products subject to sterilization and a certain range of food products.
High density polyethylene film:
- Has a density of 0.91÷093 g/cm2.
- Moderate tensile strength.
- Low flow allows welding of pieces of material.
- Frost-resistant: up to -60С°.
- Easy to paint on surface.
Linear LDPE: the basis for creating stretch multilayer films.
Each type of material produced must comply with the requirements of government regulations:
- Technical polyethylene film - GOST 10354 - 82.
- Shrinkable polyethylene - GOST 25951 - 83.
- HDPE GOST 16338 - 85.
- LDPE GOST 16337 - 77.
Production
Technical film is produced using extrusion technology in several stages:
Melting and blowing of a semi-liquid composition passed through different types of nozzles at the outlet:
- Ring, giving a sleeve type of packaging. At the exit from the nozzle, the material is blown up and dried along the entire length, followed by tightening onto rollers and winding full-fledged rolls. A labor-intensive process that allows you to get a canvas up to 2400 mm long.
- Flat, allowing you to get a straight film sheet. After extrusion, the material is dried, stretched and cut. This is a faster technology, but polyethylene sheets do not exceed 1.5 m.
Polyethylene undergoes modification to obtain a material with the desired properties:
- Chemical, with the addition of certain elements.
- Mechanical, by stretching.
- "Stitching" using ion radiation
- Thermal stabilization. After heat treatment, the structure of the material becomes more resistant to mechanical damage.
Technical film: characteristics and types of finished products
Depending on the modifications of the feedstock, the following types of technical polyethylene can be seen on sale:
- Light stabilized: highly resistant to solar radiation, service life depends on the concentration of stabilizers. Has bright colors: yellow, green and so on.
- Shrinkable: when heated, it changes its size, fitting the object inside. Linen width up to 150 mm, sleeves up to 2500 mm.
Shrink:
- Longitudinal: 40 to 80%.
- Side: 10÷50%.
- Composite shrink:various types of coatings with the addition of reagents that change the property of the material to the required characteristics.
- Reinforced: technical film with a mesh of polypropylene or polyethylene.
- Transparent: raw material - LDPE. Ethylene vinyl acetate copolymer hydrophilic film has increased transparency.
- Color: material - LDPE, dyes, stabilizers.
Technical polyethylene film: applications
The variety of types allows the use of polyethylene in almost all areas of human activity:
Construction: in the form of a sleeve or canvas, thickness 60÷200 microns. Used to wrap and cover pallets of materials and keep surfaces free from contamination
Agriculture:
- Technical film with black pigment: various types of work, including covering shoots “for steam” (thickness from 60 microns), mulching, density 10÷60 microns.
- Hydrophilic with increased transparency: for greenhouses.
Packaging:
- Thermoshrinkable film (sleeve, fabric) from primary and secondary, cheaper raw materials.
- In the form of bags: for packing garbage and waste.
Technical polyethylene film has a large assortment that allows you to satisfy any desires of the buyer. The main disadvantage is the high decomposition time of the material and the low level of its processing.
