High-density polyethylene (LDPE)

High-density polyethylene (LDPE)

Recycled LDPE granules: high pressure low density LDPE polyethylene

Many sectors of human activity involve using low density polyethylene (LDPE). It is made of the same monomer as low-pressure PE, but under completely different conditions, which give the material completely different from HDPE properties. LDPE polyethylene is prepared by polymerization of ethylene with the use of the initiator, which acts as oxygen, at a temperature of 150-200 ° C and a pressure of up to 300 MPa. The desire to reduce the cost of products often encourages manufacturers of polymer products to use recycled LDPE instead of the virgin one, because it has a lower price, but similar performance.

High-pressure low density polyethylene: properties, characteristics and types

LDPE polyethylene is produced in the form of granules, the structure of which consists of a large number of branched macromolecules, folding into a crystal lattice. Due to the weak intermolecular bonds, this material has a low density, for which it received a second name – low density polyethylene (LDPE). Its main characteristics are:

  • molecular weight: 80000 – 500000;

  • density: 0.910-0.930 g / cm3;

  • softening temperature: +80 – +90° C;

  • melting point: +103 - +115° C ;

  • Brinell hardness: 14-25 MPa.

LDPE has universal properties that allow it to be used for different purposes. Distinctive features of granules and products from this material are:

  • Flexibility, ductility and softness, making the product pleasant to the touch;

  • good resistance against exposure to a chemically active environment;

  • the possibility of obtaining products with a shiny and perfectly smooth surface, which gives the product a more attractive appearance comparing with matte products from HDPE;

  • impermeability to moisture and air;

  • resistance to UV radiation of the sun;

  • complete inertia and lack of odor, including recycled granules;

  • excellent dielectric properties.

In addition, LDPE is a non-toxic and environmentally friendly material for humans and the environment, so it can be used for contact with food and toys for children.

There are different types of LDPE granules, which can be obtained by further processing. The main modifications of this polymer material are:

  • Foamed PE having a porous structure due to the introduction of a gas mixture of hydrocarbons in LDPE, which makes it plastic and durable at the same time. Such material is produced in sheets, rolls or in the form of bundles;

  • cross-linked high-pressure PE with increased density and strength, due to the presence of cross-links formed by a chain of hydrogen atoms between branches of macromolecules – this structure is achieved by introducing hydrogen peroxide into the molten raw material;

  • copolymers of LDPE with PE, or another type of different monomers

Technology of production of recycled LDPE granules

Recycled LDPE is obtained by using waste of this material, which is formed in the manufacture of various products from it, as well as the products themselves, which have served their time or become unusable. Today there are two ways of processing such recycled raw materials.

The first method is mechanical, involving grinding into crumbs or powdered mass of pre-selected, washed and dried recyclable materials, followed by its melting and casting. This method of processing allows preserving the physical and mechanical properties of recycled materials.

The second method is physico-chemical, which provides the sequential passage of the next stages of the technological cycle of processing of LDPE:

1. Sorting of recycled raw materials by grades and cleaning it from impurities;

2. Washing of the prepared waste in special complexes with the addition of detergents for the removal of complex, stable contaminants and their subsequent drying. At this stage, metal separation and flotation methods can be used, as well as removal of solid fraction residues and excess moisture in the centrifuge;

3. Crushing and grinding of raw materials using knife crushers, jet mills, rotary and hammer mills;

4. Agglomeration of the crushed material by heating it to the plasticizing temperature with a sharp cooling of the sintered raw material, which turns it into pellets. The resulting agglomerate can already serve as a semi-finished product for the manufacture of polymer products;

5. Pelletizing of pellets, where they are melted again and passed through the extruder: at this stage, plasticizers, bactericidal materials, antioxidants or dyes can be added to the raw material in order to obtain the necessary consumer properties. The threads of the recycled low density PE obtained at the output of the extruder are cooled with water or air, and cut into granules.

Where is high-pressure polyethylene used?

The scope of application of recycled and virgin LDPE granules is quite diverse. This material is used to make:

  • pipes for pressure lines or irrigation networks, as well as fittings to them;

  • housings of household appliances;

  • blow molding products, for example, canisters and bottles;

  • thermal insulation, which is used for foam LDPE(HPPE);

  • electrical insulation shell for cable products;

  • sleeves, bags and foils of different types, including shrinkable ones;

  • thermal glue of powder form, obtained from crushed granules;

  • the tiles of the polymer mixture and the roofing material;

  • components for the automotive industry;

  • non-woven materials, yarns, textile industry, and other products.

Flexx LLC is the largest processor of polymeric waste in the country. It also makes recycled high pressure polyethylene (LDPE) which can be bought at the most favorable price in Ukraine. Order recycled low density PE with the desired consumer properties and characteristics on our website!

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