FAQs

Polyethylene is ideal for use in exterior, and especially wet or underground applications because it is:

  Tough and durable

  High impact strength

  Resistant to degradation by most acids and rot

  Maintenance free

  Chemically inert

  Flexible, with a high degree of expansion and contraction in warm or cold weather

Dimensions

The relatively high degree of thermal expansion means the material dimensions can vary by up to 3% from the sizes stated in the product description.

Colour

The standard pigment used for our products is carbon black, but we also supply brown and grey profiles, although the manufacturing process is more complex for these colours which affects the pricing.

For custom colours, especially lighter colours, a light coloured source material is required which does affect pricing. We also don’t recommend painting the products as paint does not bond well on low energy polymers.

Lifespan

Most tests show no degradation at all after 15 years. In our experience, our very first installations show no signs of degradation despite being in full sunlight. The literature says that over a 50-year period the top tenth of a millimetre can fade due to UV degradation, but this only causes slight fading and does not have any structural impact.

How to Work with Recycled Plastic Wood

Key things to note about working with Filcris Recycled HDPE:
• Can generally be treated like wood, including drilling, sawing, milling and planing
• Avoid using high drill or saw speeds to prevent melting
• Use a large-toothed saw to ensure waste material is shed efficiently
• Trial your drill or cutting tool on an off-cut first – we happily supply these free of charge
• In cold weather Filcris Recycled HDPE will be slightly stiffer and more brittle
• In warm weather the material tends to become slightly tougher and more flexible.

Drilling

• Use metal or wood bits (HSS or HM type)
• Spiral or speed bits are both applicable
• Keep cutting speeds lower than with real wood

Sawing

• This can be done with a handsaw, circular saw, chainsaw, table saw etc.

Ripping, Milling, Planing, Routing Etc.

You can plane, rout and mill Filcris Recycled HDPE and rip down planks. However, bear in mind that planks and posts tend to have a core which is less dense (often described as ‘honeycomb’) and that most of the strength is located in the wall of the product.

If this is disrupted the material may warp or curl in towards the cut face. We recommend that you seek specific advice from us relating to this.

Note that this is not an issue with recycled plastic sheet including Stokbord, which can be cut into complex shapes without this problem occurring.

How to fix Recycled Plastic Wood products

We recommend using mechanical fixings where possible to ensure structural integrity and longevity.

Screwing

If screwing, we strongly recommend pre-drilling the screw holes, and countersinking may be necessary (high quality screws such as the ones shown above can self countersink but this depends on the density of the material). The diameter of the screw hole should be slightly less than the diameter of the screw to ensure a tight fit. Bolt holes should be slightly larger than the diameter of the bolt (0.5mm – 1mm).
Standard wood or chipboard screws are suitable, but we generally screw smaller joints using stainless steel countersunk screws such as these. Larger joints, such as bearers, should be bolted.

If screwing, we strongly recommend pre-drilling the screw holes, and countersinking may be necessary (high quality screws such as the ones shown above can self countersink but this depends on the density of the material). The diameter of the screw hole should be slightly less than the diameter of the screw to ensure a tight fit. Bolt holes should be slightly larger than the diameter of the bolt (0.5mm – 1mm).

Nailing

Recycled plastic materials can be nailed but it is a dense material so it’s better to pre-drill unless a nail gun is used. In either case, galvanised or stainless steel ring-shank nails should be used to reduce the risk of the nails pulling out.

Welding

Recycled plastic wood can be welded by melting, for which special extrusion welding devices exist. The results of this welding can be quite variable and will depend on the specific product being welded, and the material used as the weld. A good weld can reach 30 – 50% of the strength of the original material. Without an extrusion welding device, the material can also be melted and welded with other heat sources, with more variable results.

Gluing and other adhesives

The general rule is that HDPE cannot be glued or bonded with tape since it is a low-energy polymer with a slightly greasy surface that repels adhesives. However, there are now several specialist adhesive products which allow the material to be bonded together or to other materials.

Please note, though, that these are expensive and the bond is not, in our opinion, sufficiently strong for structural applications, but we use it very successfully for sign-making and other light applications.

General Construction Rules

Recycled plastic wood can be used for many applications and, in principle, it is possible to use it anywhere where wood can be used.

However, plastic is a different material and behaves differently from timber. In general recycled plastic wood is more flexible than wood. This means it is not possible to apply the same span used for wood constructions in a 1:1 way. Generally either the span will have to be smaller or a thicker plank will have to be used. You can either use the data in Table 1 to calculate the correct thickness, or discuss your requirements with us – we are always happy to assist.

Expansion/Shrinkage Due to Temperature Fluctuations

Recycled plastic wood can be used for many applications and, in principle, it is possible to use it anywhere where wood can be used.

However, plastic is a different material and behaves differently from timber. In general recycled plastic wood is more HDPE expands in warmer weather and contracts in colder weather, and this needs to be taken into account, especially for use in longer or larger applications. For smaller applications, this is more manageable but still needs to be taken into account.

Key assumptions include:

• Expansion to a maximum of 2 mm per meter plank at 10°C
• For outdoor applications mounting normally occurs between 10 and 20°C
• -20°C is the minimum temperature
• In summer, the temperature can rise to approximately 50°C due to the black colour
• The largest possible temperature variance is between plus or minus 40°C.
• This means the length of the plank can become up to 8 mm longer or 8 mm shorter per span meter.
  than wood. This means it is not possible to apply the same span used for wood constructions in a 1:1 way. Generally either the span will have to be smaller or a thicker plank will have to be used.

Creep

A load on plastic will show a certain deflection which can be calculated using the elasticity modulus. If the load is maintained and the deflection is calculated again later on, you will find an increased deflection over time, which can be calculated using the creep modulus.

Most of the creep will occur during the first few months, after which the process will slow down. After a couple of years, there will hardly be increased deflection due to creep. The short-term strength can equally not be used for tensile strength or bending strength in long-term stress situations. The breakage behaviour of plastics in long-term applications, however, is rather complex.

When specifying projects, it’s best to ask for advice from us in terms of loads, creep calculations and other stress factors.

Maintenance

One of the benefits of recycled plastic is that it requires no maintenance to preserve it. Over time lichens and possibly algae can grow on the surface of the material, and dirt or dust from the surrounding environment can make it appear dirty.

Our recycled plastic wood products can, however, be cleaned with a high-pressure hose now and then using clean water without any additional chemicals. Unless a high-pressure hose fails to clean sufficiently, we don’t recommend using a steam cleaner, as the material’s surface may become somewhat fibrous.

In the case of graffiti, if it hasn’t been on the material too long a high-pressure hose should also be able to remove this to a reasonable extent.

Fire Conduct

All plastics will burn when in contact with a flame; they are combustible as are most materials. However, there are significant differences in behaviour once the flame is removed. Some materials keep on burning, while others extinguish.

NEN 6065

In NEN 6065, a norm used in the construction industry, a number of tests are performed to judge flame extension and flame spreading. Then the material is classified, ranging from class 1 for the least combustible to class 5 for the most combustible materials. Recycled plastic is classified in class 3.

For guidance and advice on the best practices to specify, install and maintain recycled plastic wood products speak to our team. We are always on hand to help whether at the start of a project or further into its lifespan.