Determination of the type of plastic by identification mark
The types of plastic that can be collected and recycled are indicated by different symbols. The codes are internationally harmonized to clarify the chemical composition of each plastic product and to determine the recyclability of those products.
1. PET or PETE - polyethylene terephthalate (PET or PET). This is the material from which plastic bottles are made. PET is widely used in the world for the manufacture of various packaging products (bottles, corners, bandage tape). In addition, PET is used for the manufacture of insulation "sintepon", as well as other non-woven materials.
2. HDPE - high density polyethylene (low pressure - HDPE). It is practically safe material. This plastic is used to make food containers, bottles and boxes.
3. PVC - polyvinyl chloride (PVC). Conventional PVC is a fairly tough plastic. To make it softer, plasticizers are added to it. Various products for economic and construction purposes are made from this material: pipes, finishing panels, window frames. Shoe soles and children's toys are made of PVC.
4. LDPE - low density polyethylene (high pressure LDPE). Basically, this plastic is used for the manufacture of films and bags.
5. PP - polypropylene (PP). This plastic is white or translucent. What kind of material is used as packaging for syrups and yoghurt. Polypropylene is prized for its thermal stability. When it heats up, it doesn't melt. Relatively safe.
6. PS - polystyrene (PS plastic). It is tough plastic. Used for the manufacture of consumer electronics housings. Many disposable tableware is made from polystyrene.
7. OTHER or O - others. This group includes any other plastic that cannot be included in the previous groups.
In addition, products made from recycled polymers are identified by the additional letter “R”. For example, RPET, RHDPE, RPVC, RLDPE, RPP, RPS. Such products are also subject to further recycling.
Forms of release, products from LDPE
Polyethylene is produced in three forms:
- sleeve;
- semi-sleeve;
- folded sleeve;
- with a cloth.
The difference between sleeves, half sleeves, folded sleeves and LDPE fabric
The film is widely used in the form of packaging material in the agricultural industry, construction industry, food industry, trade and greenhouse industry.
Polyethylene is divided into three grades:
- Polyethylene from primary raw materials - used for food packaging and other industries.
- Secondary LDPE - secondary raw materials are used for its manufacture. This type of film is considered technical, it is used everywhere, except for the food industry.
- Black LDPE film is a material with a characteristic odor, black tint. It is also called construction polyethylene. It is used in the manufacture of containers and plastic pipes. It is good to cover the beds with plants with such a film in order to get a good yield.
The second and third film grades are more affordable than primary polyethylene
Varieties
The packaging polyethylene sleeve is divided into two main types - LDPE and HDPE, that is, made of high and low pressure material, respectively. High pressure treatment allows flexibility, weightlessness and elasticity. The surface of the material will shine. The toxicity of LDPE is zero, which makes the material valuable for the food industry. But HDPE is used mainly for technical needs.
In terms of electrical insulating properties, HDPE also stands out favorably. In addition, it is worth pointing out that the film can consist of one or many layers. Additional additives include:
- canvas of the usual type (not containing additives);
- light-stabilized material (most often black, but this is not necessary);
- hydrophilic construction;
- a substance with the introduction of antistatic agents (such a canvas clogs up less than usual).
The sleeve can be black, black and white and colored. Additional gradation includes the following products:
- foamed sleeve;
- reinforced;
- heat shrinkable;
- stretch types;
- the sleeve itself;
- half-sleeve (with one-sided cut).
Production technology
The process of manufacturing a technical secondary film does not require expensive equipment and huge areas for workshops. Raw materials are available in any locality.
Raw materials
Granules for the production of recycled polyethylene made from virgin material. The raw materials are:
- waste production;
- group polymeric packaging of food products - polyethylene in which several bottles of mineral water, beer, canned food are packed;
- plastic boxes for fruits and vegetables;
- cases of household appliances.
Primary and secondary polyethylene granule
The production process of secondary (technical) polyethylene film consists of the following stages:
Before the production of pellets, waste is sorted by class and color. The paper is removed manually with scotch tape, glued labels and price tags.
Sorted waste plastic film
- Further, the material enters the washing machines, where organic and mineral impurities are removed with hot water and detergents.
- Pure polyethylene is fed into shredders - shredders. Agglomeration takes place here - sintering of pieces of material.
- The agglomerate is melted into pellets ready for re-extrusion.
For multi-layer items such as 3-layer stretch wrapping, additional ingredients will be required.
The outer layer that will be facing outward is made of high-pressure polyethylene regranulate. Regranulate is a secondary raw material from waste, which is described above. The addition of low pressure polyethylene is allowed.
The inner layer is polyethylene copolymers. The most affordable is a copolymer of ethylene and polypropylene. It is called a plastomer. Sometimes there is a "mixture" of ethylene with octene or butylene, called an elastomer.
The mechanical strength of the stretch film depends on the composition.
The outer layer, which faces inward, consists of an adhesive base - polyisobutylene. For convenience and simplification of the technology, polyisobutylene pellets are produced, suitable for extruders.
Equipment
The choice of equipment depends on the purpose of the product. The product is directly produced in an extruder loaded with polyethylene granules.
A separate unit is needed for each layer. A single layer secondary film is produced on one apparatus. For the "secondary", flat-slit extrusion technology is better suited, since "blowing" is difficult due to insufficient elasticity.
Extruders, as a rule, are adjustable to obtain technical polyethylene film up to 200 microns thick.
Completing with additional equipment - augers, ramps, etc. allows you to get products of different configurations, including secondary PVC sleeves and double sleeves.
Recycled Film Extruder
For multilayer products, Co-extruders are used, according to the number of layers. Their purpose is the same as that of the main unit - to melt the granules and evenly feed them onto the flat-slotted head.
The part is designed to provide a uniform - without overheating and stagnation zones - distribution of the PVD mass over the future web. In the case of multilayer compositions, they are also bonded here.
The hot mass in molten form is fed to a metal cooling drum.With a sharp cooling, the mass quickly hardens.
At the last stage, the fabric is wound on special drums, cutting to the required size is carried out.
Ways to increase the durability of technical films
Recycled films intended for outdoor use require a special increase in durability.
To increase resistance to ultraviolet light, light stabilizers are introduced into the composition. They allow you to extend the life of the material in the open air from 60 to 115 - 120 days, which is enough, for example, for one agricultural season or for packaging and storing products in a warehouse.
The addition of soot makes it possible to obtain black technical films that are UV resistant.
Peculiarities
A polyethylene sleeve, also known as a sleeve film, is a long polymeric structure sealed on both sides. It is used not only in its pure form, but also as a blank for the formation of special packages. In most cases, the sleeves are of standardized sizes. This is due to the use of carefully tuned production lines. The parameters are adjusted according to the practical purpose of a particular product.
The main qualities of the finished product are prescribed in GOST 10354-82. According to the standard, the plastic film must be extruded. The width of the produced material is normalized depending on the brand. Food products must also comply with the provisions of sanitary standards.
In any case, the normal technology implies the use in the production of granules with given quantitative parameters. Often, special components are used, especially plasticizing and modifying agents. Such additives can guarantee increased tensile strength. Additional manipulations are carried out by special order. The release of one-piece sleeves means that sleeve length is not standardized.
Important features of the material are:
- resistance to most substances found in everyday life;
- increased elasticity;
- almost zero permeability to water and steam;
- air tightness;
- transparency of a number of samples;
- rather high dielectric parameters;
- long period of operation;
- fusibility;
- susceptibility to ultraviolet light;
- unreliability at low temperatures.
Species overview
Polyethylene film is usually transparent, but there are also insulating, black, white, colored films. Marking will help you figure out what kind of material. The film differs in basic composition and additional components. And it can also have a different form of release.
The classification depending on the area of use includes several points.
Plain transparent. A good option for packing items and building greenhouses.
By composition
There are two main types: LDPE - high pressure polyethylene, and HDPE - low. The main differences lie in the chemical structure. Low pressure material is not afraid of mechanical stress, shows good vapor permeability and elasticity. You can even apply a drawing on such a film. There is also linear low-density polyethylene (LDL), but it is less common.
The film produced under high pressure has no crystal lattice. The material breaks easily when jerking. At the same time, there is high plasticity if the material is stretched smoothly. Such a film is less dense than HDPE. That is why LDPE is usually double.
Both types of films can be single-layer, double-layer or multi-layer. Additional additives are used to improve physical properties. There are types of films depending on the components, brands:
- unstabilized, ordinary - no additives;
- stabilized - the stabilizer allows you to protect the material from direct sunlight, which increases the service life;
- antifog (hydrophilic) - additives allow water droplets to drain from the material, this prevents the formation of a large amount of water;
- antistatic - the components repel dust and dirt from the material, the film remains clean and transparent longer.
There are modified films. Additional qualities are due to the composition and manufacturing technology. So, the film can be colored, stretch, technical and heat-shrinkable. Foamed and reinforced modifications are found.
By release form
PE is produced in factories in large quantities. The form of release is different: cloth, sleeve and half-sleeve, tube with folds, cut. It all depends on the scope of use. Initially, the film is made in the form of a sleeve, a tube.
The material is on sale in rolls. The cost from the manufacturer is usually calculated in terms of kilograms, not meters.
When packing large furniture, for the manufacture of waterproofing and roofing, half sleeves are used. If the roll is unwound by hand and the film is used in small pieces, a full sleeve is selected. Blades are used for covering the soil and other agricultural work. And also this option is relevant if several people are packing the goods at once.
Application of technical polyethylene films
The main application of the recycled film is in the packaging of goods, construction, agriculture.
Food manufacturers use secondary PVC sleeves for mulching the soil, warming up the earth after winter cold weather, and sheltering plants in the early stages of growth, when a high light transmission capacity is not yet required.
Drip irrigation tubes are also made from "secondary".
The low price attracts builders. Technical film sleeves:
- arrange waterproofing of floors and foundations;
- harbor tools and equipment;
- protect surfaces during finishing work from dust, dirt, paint ...;
- perforated membranes equip a vapor barrier.
Garbage bags and packaging for household chemicals are also made from recycled LDPE.
When choosing a secondary (technical) film, it is necessary to focus mainly on the conditions of use and purpose. Taking into account the dimensions, thickness, technical characteristics and qualities of the material will help you make the right choice.
Differences in application
Technical film is limited in use, while its cost is significantly lower compared to the cost of the primary one. It is not used, for example, for packaging medicines and food. The rapid destruction of the so-called "secondary" under ultraviolet exposure does not allow its use in greenhouses. The presence of its own odor and less attractive external characteristics should be taken into account when packaging industrial products.
Scope of use
The "secondary housing" has found active use as an agricultural film for mulching the soil, for steaming the soil and for arranging feed storage facilities, as well as as a secondary packaging film for doors, windows and other construction mechanisms and components.
Recycled LDPE film is used for finishing construction work, as well as for steam and waterproofing, in addition, it is used for the manufacture of garbage bags. This film is ideal for protecting building materials and equipment from moisture and rain.
In general, construction film can be used everywhere, provided that there is no prolonged exposure to sunlight and the appearance is not important, and also if there are no products, cosmetics or medicines in the place of its application - that is, where it can be dispensed with.
How to choose
Purchase of plastic wrap should be based on net weight (excluding packaging and spool) and film thickness. You can find out the real thickness and price of 1kg of film only by knowing its net weight. Indeed, many film manufacturers significantly underestimate its thickness, taking advantage of the plasticity of the film itself, which cannot be characterized by the same thickness at all points, and the lack of micrometers for buyers.
Weighing the film is the surest way to control film density.That is why specialists in the field of plastic film always focus on the price not per running meter, but per kilogram.
If, in the process of choosing a supplier, you went to a site that provides information only about the thickness of the film, but there is not a single word about the weight of the roll, leave from there, despite the attractiveness of its price. The actual thickness will not correspond to the declared one with almost 100% probability. For example, in the markets of the capital, the thickness is usually underestimated by 45-55%.
According to the standards, the final weight of a roll of 1 or 2 grade film with a width of 3 m, a thickness of 100 microns, with a 100-meter winding length should be equal to 27.6 kg. Unfortunately, due to the high cost of this quality film, it sells very poorly. Even in our country, the premium grade 100 micron film has a real thickness of 90 microns, since it weighs 25 kg. However, with the help of our equipment, a film of 10% thickness difference is produced (i.e., the thickness varies within 81-99 microns), therefore such a film has full compliance with GOST, which determines a thickness deviation of ± 20% (i.e. 80- 120μm) for premium grade.
MegaPlast produces secondary and primary films. Data on the price of the product per kilogram and its net weight can be clarified by calling (495) 970-43-59.