The polymer resin component coming from the separate collection for WPC plastic - wood products

The WPC, characterized as a wood-polymer compound, was born in Italy in the 60s of the last century by the Covema brothers who began the experimentation of blends made with fiber or wood flour with polymers and additives.

Today the production of WPC is a worldwide reality and the use of floors and coatings, not only in the construction sector, has reached an appreciable market by virtue of the qualities expressed by this compound.

Production takes place, in most cases, through the extrusion of the selected materials in plants that can use single or twin screws with different profiles. The advantage of using twin-screw extruders is expressed by the greater capacity of the mass processing plant in terms of mixing and processing uniformity of the material without degrading it.

The recipes that make up the future element in WPC strongly depend on the machine used for extrusion (or molding), on the finish of the material you want obtain and the characteristics of durability and impermeability of the product according to its final location.

In general it can be said that the percentage share of wood compounds can vary from 40 to 60% of the recipe and that polymeric components, considering an average 5% such as additives such as dyes, coupling agents, UV stabilizers, blowing agents, foaming agents and lubricants, account for the remaining part.

Most of the world production of WPC uses polyethylene as a polymer binder by virtue of the compatibility in the melting temperatures of the two masses that make up the mixture and for the easy availability of recycled raw material on the market.

The recycled polyethylene used can be in HDPE or LDPE, let's see the differences:

• HDPE is a waste that comes from separate collection in the form of detergent bottles, shampoos, creams, milk and other consumer packaging that are collected from our homes, selected in automatic systems that read the chemical nature (density of the material), ground into small flakes, washed in industrial plants, selected by color, if necessary, through machines optical reading and subsequently extruded to create a raw material in the form of granules. HDPE is a stable, clean, single-component product with only small traces of PP inside (caps), lending itself well to the extrusion action typical of WPC. It is found in abundance on the market in those countries where separate collection is efficient.

• LDPE is a waste that comes from the separate collection of plastic films that come from domestic and industrial waste which by their nature of use are less selectable, in terms of mono-plastics than HDPE. They can be of different origin and therefore of different quality:

 Agricultural film is normally collected with a certain percentage of sandy residues that must be eliminated, though not always totally, through careful washing. The film, during its lifetime, undergoes a degradation from the sun which is to be considered when choosing the additives of the recipe of the WPC that will have to compensate for this deficit.

 Industrial or first-use film are those materials that are collected from packaging waste of companies or distribution chains and which normally represent clean films never recycled. The quality of this waste is among the best to be used for recycling. 

 Films deriving from separate collection that contained waste organic or other contaminants, both solid and oily, whose mechanical recycling significantly reduces components other than LDPE, but fails to completely eliminate these substances.

• Polypropylene is a material that can derive from separate collection in the form of rigid waste or in the form of packaging film. The mechanical selection yields a good quality raw material that may also have a certain percentage of PE inside. PP is a cheap and ductile material in the production of WPC.

• The PVC in the form of waste can derive from the industrial supply chain, therefore as primary processing waste or in the form of separate collection such as the waste of pipes, window profiles, packaging, tiles and other materials to be selected. Post industrial waste is certainly the best in terms of cleaning from pollutants and final yield but it has a high cost and a limited quantity available on the market. The advantage of using PVC as a polymeric binder is the dimensional stability of the pieces produced and the smoothness.

The function of recycled polymers and protective additives within the wood mixture create numerous advantages to the final product:



 Waterproof

 Imputrescence

 Resistant to U.V.

 Excellent cold workability

 Good flexural strength

 Excellent color maintenance

 Recyclable in the WPC sector

 Resistance to the corrosive action of sea water

 No surface maintenance

Automatic translation. We apologize for any inaccuracies. Original article in Italian.