WPC, extruder, compounding, rotating, ICMA




WPC-WOOD PLASTIC COMPOSITES/co-rotating extruders/twin screw extruder/COMPOUNDING 

Example Application:

  • furniture
  • automotive interiors







Explanation for beginners:

  • DIRECT EXTRUSION LINES –  process that combines the compounding and extrusion technics in one step. These lines are conveniently  equipped with gravimetric dosing units, one or more co-rotating twin-screws designed to mix a resin (like a polyolefin) with other raw materials and usually a downstream systems (a calender or a die) forming a sheet/foil or a profile. Read more
  • CO-ROTATING TWIN-SCREW EXRTUDERS – an extruder two with intermeshing modular screws  rotating in the same direction. A very good solution to get quality technical compounds made of several ingredients. Read more 


Based in Italy, ICMA supplies turnkey systems equipped with state of the art co-rotating twin-screw extruders to cover a wide range of demanding formulations and application requests. Among these, compounding lines and extruders specially designed for wood plastic composites and, more generally, natural fibres compounding, have represented a key area of expertise for ICMA since many years.
In addition to compounding systems ICMA has developed the so-called direct extrusion, i.e. the simultaneous production of two distinct operations such as COMPOUNDING + EXTRUSION in one single step, has become a key theme in the present market conditions.

The reason, simple but obvious, is that the reduction of production costs in this period of a more and more challenging market, does overcome the obstacle of the use of a more complex technology.

What is it?

Simply (for those who are familiar with the compounding) in separate feeding of each individual component of the formulation, in different points of the ‘extruder, depending on the technological requirement of the process.

In the specific case of the WPC, this consists in feeding the wood flour separately, in a side feeder positioned downstream of the main one, to shorten the residence time and to avoid the degradation of wood that is very temperature sensitive.


Direct extrusion has always been one of the leading technologies of ICMA and the evidence is given by the number of international patents obtained from the 70’s and above all the one achieved in 1985, which expressly covered the combination CO-ROTATING TWIN SCREW EXTRUDER-CALENDER for the direct extrusion of WPC flat sheets.

This product is still used as a thermoformed support for all the internal car upholstery.

The automotive industry was the first sector where the cost of production has become the “key factor” that is why this product has been a worldwide success. In all countries where the automotive industry is present, you will find ICMA direct extrusion systems: USA, Japan, Korea, China, Malaysia, Brazil, and Russia and of course Europe.


The WPC products more visible and more easily met in everyday life are the profiles for decking. This type of market has started to have some weight from about a decade ago using a technology derived from the standard PVC profiles (it was relatively easy to replace mineral fillers with natural ones). The European market loves PVC FREE products and this has led to develop WPC profile on polyolefin base by adapting the existing technology to new product.

The highest percentage of wood (which among other things permits to balance/decrease the cost of the formulation) and the polyolefin matrix, however, can give productive stability only under the condition of having constant characteristics of the raw materials and formulation (very difficult to achieve with a “living” material such as wood). This is way also the leading manufacturers of extrusion lines have started recommending (someone quietly, someone clearly) that the ideal solution for industrial production of WPC profile is obtained starting from a pre-compounded/pelletized material product.

This element is very important considering that WPC market for decking application has become somehow mature and processors will be more and more open to consider innovative technologies that, even with an increased initial investment costs, will allow an effective cut in production costs with a sizeable better return on the investment. Given this new opportunity, ICMA decided to apply its 50 years’ experience in WPC direct extrusion technology and compounding to the development of these new lines dedicated to the WPC profile market. This is, again, a great success.

The main advantages granted by this technology, compared to the traditional one that uses counter-rotating extruder, can be summarized as follows:

  • Split feed technology (i.e. co-rotating extruders) allows material energy savings 
  • Higher mechanical characteristic due to better fibers/plastic mixing
  • Limited material degradation due to only one heat/shear history
  • Possibility to accept a higher degree of moisture of the fibre thanks to the presence of highly performing degassing units that enables production stability in several production conditions. This make also possible to a certain extent to use un-dried wood flour or fibre, with an evident cost saving.
  • No need of material pre-mixing/agglomeration
  • A higher freedom in formulation options leaving room to the use of local resins and fibers.
  • Less space needed with only one system for compounding and extrusion.
  • Simple logistic management
  • Lower maintenance/management cost due to smaller extruder size
  • Lower maintenance cost due to modular construction of screws and barrel
  • Formulations adjustable in-line
  • Maintain a proprietary know-how with in-house manufacturing process

This technology is addressed to all processors, existing or new. Some success cases fit in the following areas:

  • Companies already active in the WPC profile market that plan to improve their production efficiency and cut costs.
  • Companies located in areas where the fiber is present in big quantities and therefore there is limited interest to buy a compound already incorporating such fiber.
  • Companies active in highly competitive markets willing to position itself at the higher end with superior quality products but with competitive productions costs.


Type of News: Products, Environment

Keywords (Max. 5): WPC, extruder, compounding, rotating, ICMA