Current Market Scenario
In the west, USA and Europe Thermoplastic natural fibre composites are
having a good market demand. No doubt that during the last five years,
demand for wood-plastic composites has grown by 35-40 %. By the end of 2007
WPC would do business worth $2.0 billion in North America and western
Europe. In the European market the main driving force for further product
development of WPC is the Automobile market. In context of the present
scenario, there lies a huge potential for extruded WPC profiles in products
like decking, window or door profiles.
Main Ingredients of WPC Profiles
The following material forms the main ingredient of extruded WPC profiles.
- Wood Flour
Wood flour is essentially a wood cellulose that is finely ground. For
a product to be termed as a wood flour the particle size should be above
20 mesh but below 850 microns. The following table lists some of the
chemical and mechanical properties of Wood flour.
| Physical/Chemical
Properties |
Specifications |
| Acidity (pH) |
3.5 - 4.6 |
| Density |
0.66 P>Density |
| Solubility in Water |
Less than 0.1% |
| Ash Content |
.23 to 0.25 Hardgrove Index |
| Moisture Content |
4% to 6% (depends on relative humidity) |
| Specific Gravity |
0.5-0.8 |
| Colour |
Brown (light) to tan |
- Thermoplastic Resins
The choice of resin selected for use in thermoplastic composites is
dependent on many factors. Wood tends to a show a nature for degradation
at higher temperatures, so a thermoplastic resins which can be processed
at a temperature below 2000, centigrade is to be selected for processing
of the composites. Let's have look at the choices available for
thermoplastics available for extruded plastic profile.
| Polyethylene(PE) |
Polypropylene |
PVC |
| Relatively less expensive |
Good service temperature |
Strongest resin |
| Excellent toughness and impact strength |
Lowest Density as compared To PE and PVC |
Highest service temperature, |
| Can be used both in virgin & recycled form |
Best suited to building and automobiles |
Excellent weather resistance |
| Shows a tendency to stabilize against thermal degradation |
|
Has a tendency towards brittleness |
- Additives
The main function performed by additives in thermoplastic composites
are as under:
- Improve mechanical properties
- Provide chemical stability during processing
- Improve the flow of raw material blend

Manufacturing of WPC
Extruded WPC profiles are typically manufactured using extrusion process.
In the Extrusion process there is a continuous heating, compressing and
conveying of raw ingredients that has already been premixed. The extrusion
process consists of shaping of the material with the help of extrusion dies,
cooling of a product upon its exit from the die and down stream handling
including cutting, embossing, sanding and other treatments. This process
saves the cost of machining and fabrication. Shape of the final product
obtained would be replication of the die opening. The products/profiles made
by this process can be cut into small pieces, moulded, routed, sanded etc.,
with the same tools, feeds and speeds as with wood.
While coming to the extruder type there are variety of equipment available
the most common are single-screw extruders, counter-rotating twin-screw
extruders or set ups using custom extruders. Out of the three the
single-screw system is the cheapest. But typically it has some limitations.
Twin-screw extruders on the other hand are good option for extruded woo
thermoplastic composites or WPC because here the mixing action is able to
blend the wood filler and polymer perfectly in a single process. Along with
that it gives low screw speed as well as low-shear mixing, so essential for
keeping down the temperatures.
Application of WPC Profile
| Industry |
Application |
| Building & Construction |
Window and door frames, Cladding |
| Industrial/Infrastructure |
Industrial flooring, railings, bulkheads, Railway sleepers etc. |
| Automotive |
Door & head liners, interior panels, rear shelves, Truck floors
etc |
| Garden/ Outdoor |
Decking, Fencing, garden furniture, shelters sheds, playground
equipment etc. |
| Interiors and Internal finishes |
Interior panels, Office furniture, Kitchen cabinets, shelving,
shutters/Blinds etc. |
WPC Extruded Profiles in Construction
Applications
Salient Features
- Cross section optimization for construction applications.
- Hollow sections for reduced weight.
- Surface texture provides improved slip resistant surface.
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