Woodforce | Natural Strength for Plastics

Compounding Woodforce

Woodforce stands alone in the world of natural fibre extrusion. Designed to be the friendliest alternative in the compounding industry. The Woodforce dice are very easy to dose during the extrusion process. With Woodforce there are no complications. Woodforce is used with standard dosing equipment and does not require any chopping or preparation.

Sonae industria has a set of recommendations to maximize the productivity of the compounding lines:

Before processing:

Woodforce dice have an average moisture content of 5 to 8% by weight when stored under "normal" low humidity conditions. Depending on extruding conditions and type of equipment (vents, etc.), pre-drying might be critical to obtain a good compound. However, with proper venting during extrusion (both atmospheric and vaccum venting), the standard product 5-8% moisture content has been successfully compounded in many manufacturing sites. Dried wood fibres are hygroscopic, meaning the fibres will readily absorb moisture from air. It is therefore essential to keep Woodforce in a proper low humidity storage area.

Feeding into the extruder:

Woodforce is made of high density, free-flowing pellets, which overcomes the feeding issues usually associated with natural fibres (low bulk density). Woodforce is unlikely to cause bridging or funnel-flow/plugging issues.

Feeding Woodforce downstream, using a side feeder port, into the molten polymer is recommended (especially with higher melting point thermoplastics) to shorten the Wood Fibre residence time in the extruder and limit the wood fibre thermal degradation. The advantage of this configuration is that the polymer can be aggressively melted, using mixing elements and higher temperatures. While in contrast, after the fibre is introduced, the fibre and the polymer are mixed together using mild dispersive elements and a lower temperature.

A side feeder with a stirred hopper has been successfully used to feed the wood fibre dice into an extruder. Loss in weight feeder systems can be used and would ensure better control of the pellet feeding rate.

Extrusion conditions of Woodforce:

A key attribute of Woodforce is that it does not require severe mixing extrusion conditions (shear forces/rate) to fully release the dice into individual fibres. As a result of gentler extrusion, fibre length is preserved. A short residence of the wood fibre dice and a melt temperature below 200ºC are essential to avoid thermal degradation of the wood fibres. Woodforce's patented recipe was engineered to ensure proper release in individual fibres with a superior aspect ratio.

For a successful extrusion:

  1. 1. Use a co-rotating twin screw extruder
  2. 2. Keep temperature below 200°C or 390°F
  3. 3. Side feed the Woodoforce dice
  4. 4. Vent with both vaccum and atmospheric
  5. 5. Add a coupling agent
  6. 6. Design screw with medium dispersion discs, 1/3 mixing - 2/3 conveying
  7. 7. Use a co-polymer with MFI greater or equal to 35