JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016 - 63

Focus
Green Dot Holdings LLC, a bioscience social
enterprise headquartered in Cottonwood
Falls, Kansas (USA), is committed to
improving the environment through material
advances. The company believes that
through the research, invention and creation
of renewable, biobased resins, it can make
actual improvements in peoples' lives by
putting less stress on the planet. Through a
variety of properties - recyclability, compostability, sustainability - Green Dot intends
to make plastics a part of the solution, not
the problem.
This full-service bioplastics company is
dedicated to delivering the very best of sustainable materials to its customers. That's
the thinking behind the Terratek® line of
bioplastics, developed to meet the growing
demand for biobased and compostable
materials with fewer of the drawbacks
associated with traditional plastics.

be dedicated to drying. Organic fillers
need to be dried properly before being
added to the plastic, or the two will not
bond correctly.
The composites need to be dried again
before being packaged to avoid the
onset of mould and eventual degradation of the product. Ideally, customers
themselves will not have to dry composite plastics once they have arrived at
their facility. Low moisture content is
something manufacturers should simply
demand from their suppliers.
Processing temperatures are one of
the few portions of the manufacturing
phase where wood-plastic composites
differ significantly from conventional

plastics. Wood-plastic composites are
generally processed at temperatures
around 50 degrees lower than the same,
unfilled material. Most wood additives will begin to burn at around 400
degrees Fahrenheit (200°C).

gate size and positioning, but the overall
process remains the same. With standard extruding equipment, uniformly
sized wood-plastic composite pellets
will have no problem performing up to
expectations.

Melting wood-plastic composites at too
high of a temperature increases the risk
of shearing - pushing a material that
is too hot through too small of a gate,
where the increased friction burns the
wood and causes discolouration and a
degraded plastic. This problem can be
avoided by running wood-plastic composites at a lower temperature, ensuring
the gate size is adequate and removing
any unnecessary turns or right angles
along the processing pathway.

Wood-plastic composites are also
compatible with foaming agents. The
addition of these foaming agents can
create a balsa-like material. This is a useful property when the finished product
needs to be especially lightweight or
buoyant.

Relatively low processing temperatures
means that manufacturers seldom need
to achieve higher temperatures than a
traditional polypropylene. This eliminates the difficult task of taking heat out
of the manufacturing process. There is
no need for the addition of mechanical
cooling equipment, moulds specifically designed to reduce heat or other
extraordinary measures. This means further reduced cycle times for manufacturers, on top of already faster cycle times
due to the presence of organic fillers.
When it comes to processing techniques, wood-plastic composites once
again behave similar to any other
plastic. During foaming, extrusion and
injection moulding, they are compatible
with existing machinery. For injection
moulding, the above considerations
should be taken into account regarding

The long and short of working
with wood-plastic composites
The specifics of wood-plastic composite
formulations should be discussed and
considered throughout product design
and manufacturing. Designers must
keep in mind that material decisions
concerning wood particle size and
species will have implications for manufacturers. Manufacturers will no doubt
have some questions about the chosen
material. Will it work with my existing
machinery? Will I need to redesign my
tooling? What sort of cycle time should
I expect with wood-plastic composites?
Knowing the answers to these questions
will help manufacturers become more
comfortable working with wood-plastic
composites. As it turns out, these materials are remarkably similar to conventional plastics, with the added benefit of
environmental sustainability. n

No104 April - May 2016 / jec

More information:
www.greendotpure.com

composites magazine 63

http://www.greendotpure.com http://www.mikrosam.com

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #104 - April/May 2016