WPC glossary: 100 terms, materials, methods and standards

Definitions and material structure #

Wood–plastic composite (WPC) — A material combining wood particles or fibres with a polymer. The formulation and finished profile determine performance; WPC is not a quality grade.
Names and abbreviations: wood-polymer composite; woodfiber-plastic composite. [1, 2]

Natural fibre composite (NFC) — A composite containing natural fibres or particles in a matrix. NFC is broader than WPC: flax, hemp and agricultural fibres need not contain wood.
Names and abbreviations: plant-fibre composite. [1, 2]

Wood–thermoplastic composite (WTC) — A wood-filled composite with a thermoplastic matrix that softens when heated. The name excludes cured thermoset systems.
Names and abbreviations: wood thermoplastic. [1, 2]

Composite material — A material made from distinguishable constituents working together. “Composite” alone does not identify the resin, reinforcement or suitable application.
Names and abbreviations: composite. [1, 2]

Matrix — The continuous phase surrounding the filler or reinforcement. Its chemistry influences processing, temperature response and moisture behaviour.
Names and abbreviations: polymer matrix; binder phase. [1, 2]

Thermoplastic — A polymer that softens on heating and hardens on cooling. Repeated processing can degrade it; remeltability does not guarantee practical recyclability.
Names and abbreviations: melt-processable polymer. [1, 2]

Thermoset — A polymer system forming a cured network that cannot simply be remelted. Phenolic and epoxy systems differ from ordinary thermoplastic decking.
Names and abbreviations: crosslinked resin. [1, 2]

Compound — A prepared blend of polymer, filler and additives. It may be supplied as pellets or processed directly into a product.
Names and abbreviations: composite compound. [1, 2]

Filler — A dispersed ingredient modifying cost, processing or properties. A filler may improve stiffness without improving every strength or impact measure.
Names and abbreviations: particulate filler. [1, 2]

Reinforcement — A constituent used to improve selected mechanical properties. Fibre length, orientation and bonding determine how effectively loads are transferred.
Names and abbreviations: reinforcing fibre. [1, 2]

[1] [2]

Fibres, fillers and core polymers #

Wood flour — Finely ground wood particles. Particle-size distribution, species and moisture matter; wood flour is not identical to long reinforcing fibres.
Names and abbreviations: wood powder. [1, 2]

Wood fibre — An elongated wood-derived component. Fibre damage during compounding can reduce its aspect ratio and alter reinforcement efficiency.
Names and abbreviations: wood fiber. [1, 2]

Natural fibre — A fibre of natural origin; here mainly wood, flax, hemp or other plant material. Natural origin does not establish composite biodegradability.
Names and abbreviations: plant fibre; natural fiber. [1, 2]

Cellulose — A structural polysaccharide in plant cell walls. Its hydroxyl-rich surface contributes to water affinity and challenges bonding with nonpolar polymers.
Names and abbreviations: cellulosic fibre component. [1, 2]

Lignin — A complex plant polymer associated with cell-wall rigidity. Its behaviour differs from cellulose and influences wood chemistry and weathering.
Names and abbreviations: wood lignin. [1, 2]

Rice husk — The protective covering of rice grains, usable as a composite filler after preparation. Its silica content distinguishes it from ordinary wood flour.
Names and abbreviations: rice hull. [1, 2]

Aspect ratio — The ratio of particle or fibre length to its transverse dimension. Higher values can assist reinforcement, but dispersion and processing damage also matter.
Names and abbreviations: length-to-diameter ratio. [1, 2]

Moisture content — The amount of water in a material on a stated wet or dry mass basis. Excess moisture can cause processing defects.
Names and abbreviations: feedstock moisture. [1, 2]

High-density polyethylene (HDPE) — A polyethylene grade family used as a WPC matrix. Resin grade, melt flow and additives matter more than the acronym alone.
Names and abbreviations: PE-HD. [1, 2]

Polypropylene (PP) — A thermoplastic matrix used in natural-fibre composites. Processing conditions and compatibility with fibres must suit the selected grade.
Names and abbreviations: polypropene. [1, 2]

[1] [2]

Polymers and interface chemistry #

Polyvinyl chloride (PVC) — A thermoplastic used in some composite profiles. WPC does not mean PVC-free; confirm the actual formulation rather than assuming resin identity.
Names and abbreviations: vinyl polymer. [1, 2]

Polyethylene (PE) — A family of thermoplastics including HDPE and LDPE. Different grades have different density, flow and mechanical behaviour.
Names and abbreviations: polythene. [1, 2]

Low-density polyethylene (LDPE) — A more highly branched polyethylene family. Its properties differ from HDPE; changing resin can alter composite stiffness and processing.
Names and abbreviations: PE-LD. [1, 2]

Polylactic acid (PLA) — A polyester often made from renewable feedstocks. Bio-based origin does not establish outdoor durability or degradation under ordinary garden conditions.
Names and abbreviations: polylactide. [1, 2]

Recycled HDPE (rHDPE) — HDPE recovered for reuse. Contamination, previous ageing and batch consistency must be controlled when producing repeatable WPC formulations.
Names and abbreviations: reprocessed high-density polyethylene. [1, 2]

Maleated polypropylene (MAPP) — A functionalised polypropylene used to improve fibre–matrix compatibility in suitable systems. Dosage and effectiveness depend on the formulation.
Names and abbreviations: maleic-anhydride-grafted polypropylene. [1, 2]

Maleated polyethylene (MAPE) — A functionalised polyethylene used as a compatibiliser in suitable PE-based composites. It is not automatically interchangeable with MAPP.
Names and abbreviations: maleic-anhydride-grafted polyethylene. [1, 2]

Coupling agent — An additive promoting interaction between dissimilar constituents. A compatibiliser has a related role, but the terms are not exact synonyms in every chemistry.
Names and abbreviations: interface modifier. [1, 2]

Lubricant — An additive reducing friction during processing. Excess or unsuitable lubricant can affect bonding, surface quality and mechanical properties.
Names and abbreviations: processing lubricant. [1, 2]

UV stabiliser — An additive intended to reduce light-driven deterioration. It does not make every colour or exposed wood component permanently unchanged.
Names and abbreviations: light stabiliser. [1, 2]

[1] [2]

Additives and primary processing #

Antioxidant — An additive limiting oxidative damage during processing or use. Its effectiveness depends on chemistry, concentration and exposure.
Names and abbreviations: oxidation stabiliser. [1, 2]

Pigment — A dispersed colouring material. Colour influences appearance and can affect solar heating; a dark surface is not necessarily cool underfoot.
Names and abbreviations: colourant. [1, 2]

Flame retardant — An ingredient intended to modify burning behaviour. Its presence does not establish a product fire classification without appropriate testing.
Names and abbreviations: fire-retardant additive. [1, 2]

Extrusion — Continuous shaping of a heated compound through a die. Cooling and calibration help establish the profile dimensions.
Names and abbreviations: profile extrusion. [1]

Co-extrusion — Simultaneous formation of multiple material streams into a layered product. A cap can differ chemically from the composite core.
Names and abbreviations: multilayer extrusion. [1]

Cap layer — An outer layer modifying surface behaviour. Coverage, thickness and adhesion matter; a cap does not make cut ends or joints automatically waterproof.
Names and abbreviations: capping; protective shell. [1]

Injection moulding — Shaping a molten compound by injecting it into a mould. Flow, fibre orientation and cooling influence the finished component.
Names and abbreviations: injection molding. [1]

Compression moulding — Shaping material under pressure in a mould, often with heat. It differs from continuous extrusion and can suit panels or formed parts.
Names and abbreviations: compression molding. [1]

Compounding — Mixing constituents to distribute filler and additives through a polymer. Dispersion must be balanced against heat exposure and fibre damage.
Names and abbreviations: melt blending. [1]

Drying — Reducing moisture before processing. The required target depends on feedstock, polymer and equipment; one universal drying schedule is inappropriate.
Names and abbreviations: feedstock drying. [1]

[1] [2]

Finishing, printing and product types #

Extrusion die — The tool opening that shapes an extrudate. Die geometry must account for flow, swelling, cooling and dimensional tolerances.
Names and abbreviations: profile die. [1]

Calibration — Controlling an extruded profile's shape and dimensions while it cools. Poor control can produce distortion or inconsistent wall thickness.
Names and abbreviations: profile sizing. [1]

Embossing — Creating a pattern on a surface, often to imitate grain. Visual texture alone does not prove wet slip resistance.
Names and abbreviations: surface texturing. [1]

Sanding — Removing surface material to change finish or texture. Sanding a capped board can damage its protective layer; follow product instructions.
Names and abbreviations: surface abrasion. [1]

Fused filament fabrication (FFF) — Layer-by-layer printing with heated filament. Wood-filled feedstocks require suitable moisture control, nozzle selection and extrusion settings.
Names and abbreviations: fused deposition modelling; FDM. [1]

Melt flow rate (MFR) — Mass passing through a specified die over time at stated temperature and load. Values measured under different conditions are not directly comparable.
Names and abbreviations: melt flow index; MFI. [9]

Solid profile — A profile without intentional longitudinal hollow chambers. Solid geometry alone does not establish structural capacity or a permitted support span.
Names and abbreviations: solid composite board. [1]

Hollow profile — A profile with internal chambers. Wall thickness, rib arrangement, impact resistance and end detailing affect its suitability.
Names and abbreviations: hollow-core board. [1]

Composite decking — Boards intended as an outdoor walking surface over supports. Verify span, slip behaviour, fastening and exposure for the exact product.
Names and abbreviations: WPC decking; composite deck boards. [1]

Composite cladding — Profiles used as an exterior covering. Fire, wind, fixing and ventilation requirements belong to the complete façade system.
Names and abbreviations: WPC cladding; façade profiles. [1]

[1] [9]

Applications and installation #

Composite fencing — Composite elements used in fences or screens. Posts, foundations and connections must resist the site's wind loads.
Names and abbreviations: WPC fencing; privacy screen boards. [1]

Joist — A member supporting decking boards. Some WPC joists require continuous support and must not be assumed to be spanning structural beams.
Names and abbreviations: deck support member. [1]

Fascia board — A finishing board covering deck edges or risers. Decorative fascia is not automatically suitable as a load-bearing tread or joist.
Names and abbreviations: edge trim; finishing board. [1]

Tongue and groove — A joint with a projecting tongue fitting a groove. A closed-looking joint is not proof of a watertight assembly.
Names and abbreviations: T&G; interlocking profile. [1]

Hidden fastener — A fixing system reducing visible screw heads. Clip spacing, movement allowance and compatibility must follow the board manufacturer's instructions.
Names and abbreviations: concealed fixing; decking clip. [1]

Expansion gap — A designed clearance for dimensional movement. Required gaps depend on board length, temperature, material and the installation system.
Names and abbreviations: movement allowance. [1]

Joist spacing — The distance between support centre lines. Approved values depend on board geometry, loads, temperature and application, including stairs.
Names and abbreviations: support centres; centre-to-centre spacing. [1]

Ventilation — Air exchange around an assembly to assist drying. Necessary clearances depend on the construction; an enclosed damp cavity can retain moisture.
Names and abbreviations: under-deck airflow. [1]

Drainage — Providing a route for water to leave an assembly. Board joints alone do not replace drainage design beneath a deck.
Names and abbreviations: water management. [1]

Maintenance — Cleaning and inspection needed to retain function and appearance. Low maintenance does not mean no cleaning or no inspection.
Names and abbreviations: deck care; routine cleaning. [1]

[1]

Mechanical properties and durability #

Tensile strength — Stress sustained during a defined pulling test. Specimen preparation, direction and conditioning affect results; it is not a deck span rating.
Names and abbreviations: strength in tension. [7]

Flexural strength — A strength measure obtained in bending under a stated method. Compare geometry and conditioning before comparing numerical values.
Names and abbreviations: bending strength; MOR. [6]

Elastic modulus — The relationship between stress and strain in a specified range. Stiffness differs from strength; tensile and flexural moduli are not interchangeable.
Names and abbreviations: stiffness modulus; MOE. [6, 7]

Creep — Progressive deformation under sustained load. Temperature, stress and time affect it, so short bending tests cannot establish long-term deflection alone.
Names and abbreviations: time-dependent deformation. [1, 3]

Impact strength — Resistance measured under a specified impact test. Notched and unnotched results, and different test methods, are not interchangeable.
Names and abbreviations: impact resistance. [1, 3]

Water absorption — Water taken up under specified exposure conditions. Duration, temperature and specimen geometry must accompany a reported percentage.
Names and abbreviations: moisture uptake. [3, 8]

Thickness swelling — Increase in thickness following moisture exposure. It differs from mass-based water absorption and should be reported separately.
Names and abbreviations: moisture-induced swelling. [1, 3]

Thermal expansion — Dimensional change as temperature changes. The relevant coefficient, board length and temperature range inform movement allowances.
Names and abbreviations: temperature-driven movement. [1, 3]

Weathering — Changes caused by sunlight, moisture and temperature exposure. Colour retention and retained mechanical performance are different outcomes.
Names and abbreviations: outdoor ageing. [1, 3]

Slip resistance — Resistance to slipping under specified test conditions. Wetness, contamination, footwear and surface wear matter; grooves alone are not proof.
Names and abbreviations: slip performance. [14]

[1] [3] [6] [7] [8] [14]

Laboratory methods and service evidence #

Density — Mass divided by volume using a stated measurement basis. Profile geometry and internal voids complicate comparisons with material density.
Names and abbreviations: mass per unit volume. [1, 3]

Thermogravimetric analysis (TGA) — A method measuring mass changes during a controlled temperature programme. It helps study decomposition but does not directly determine service life.
Names and abbreviations: thermal mass-loss analysis. [1, 3]

Differential scanning calorimetry (DSC) — A method measuring heat-flow differences during heating or cooling. It can investigate polymer melting and crystallisation.
Names and abbreviations: thermal analysis. [1, 3]

Scanning electron microscopy (SEM) — Imaging that reveals fine surface or fracture features. Images can support interface analysis but do not alone quantify bond strength.
Names and abbreviations: electron microscopy. [1, 3]

Fourier-transform infrared spectroscopy (FTIR) — A technique probing molecular vibrations through infrared absorption. It helps identify chemical groups; interpretation requires suitable controls.
Names and abbreviations: infrared spectroscopy. [1, 3]

Service life — The period a product meets stated requirements in its actual exposure and maintenance conditions. It is not identical to a warranty period.
Names and abbreviations: useful life. [1, 3]

Warranty — A supplier's stated contractual remedy with conditions and exclusions. Its duration is not a measured physical lifespan.
Names and abbreviations: commercial guarantee. [1, 3]

Traceability — Connecting delivered products to manufacturing, raw-material and quality records. A supplier name alone is not complete batch evidence.
Names and abbreviations: batch traceability. [1, 3]

Recycled content — The proportion of recycled material on a declared basis. Distinguish whole-product percentages from percentages referring only to the polymer fraction.
Names and abbreviations: recycled material share. [1, 3]

Recyclability — The ability to collect and process material into a useful output. Actual acceptance, sorting and local facilities must also exist.
Names and abbreviations: recycling potential. [1, 3]

[1] [3]

Circularity and technical documentation #

Bio-based — Made wholly or partly from biological feedstock. Bio-based content does not mean biodegradable, compostable or automatically lower impact.
Names and abbreviations: biomass-derived. [1, 13]

Biodegradability — Breakdown through biological activity under specified conditions. Results depend on environment and time; wood content does not make ordinary WPC compostable.
Names and abbreviations: biological degradation. [1, 13]

Life cycle assessment (LCA) — Assessment of environmental impacts across a defined system. Comparisons require compatible functions, boundaries, assumptions and service-life scenarios.
Names and abbreviations: life-cycle analysis. [13]

Environmental product declaration (EPD) — A structured declaration of environmental data based on defined rules. An EPD is not by itself an environmental superiority label.
Names and abbreviations: environmental declaration. [12, 15]

Carbon footprint — Greenhouse-gas emissions expressed as carbon-dioxide equivalents within a defined boundary. Transport distance alone does not establish the total product footprint.
Names and abbreviations: greenhouse-gas footprint. [13]

Batch — A traceable production quantity sharing defined manufacturing conditions. Batch identification helps connect deliveries, samples and quality records.
Names and abbreviations: production lot. [1, 13]

Test method — A defined way to measure a property. Naming a method does not provide a result or prove a product passed a requirement.
Names and abbreviations: testing procedure. [4, 5]

Product specification — A document defining required characteristics and intended scope. It should identify the product, applicable tests, acceptance criteria and installation conditions.
Names and abbreviations: technical specification. [4]

EN 15534 — A multi-part series for cellulose-based materials combined with thermoplastics. Select the relevant test or product part; the number alone is insufficient.
Names and abbreviations: European WPC/NFC standards series. [4]

ISO 16616 — A standard addressing test methods for exterior natural-fibre composite deck boards. A test report must identify the applicable edition and product.
Names and abbreviations: NFC deck-board test methods. [5]

[1] [4] [5] [12] [13] [15]

Product standards and test standards #

EN 15534-4 — The decking product part of EN 15534. Its scope is not automatically interchangeable with the cladding or fencing parts.
Names and abbreviations: decking profiles and tiles. [4]

EN 15534-5 — The cladding product part of EN 15534. A decking result does not establish compliance for a façade application.
Names and abbreviations: cladding profiles and tiles. [4]

EN 15534-6 — The fencing product part of EN 15534. Product requirements do not replace site-specific design of posts and foundations.
Names and abbreviations: fencing profiles and elements. [4]

ISO 178 — A method for investigating flexural properties of plastics. Use the stated edition, specimen and conditions; a draft revision is not a published replacement.
Names and abbreviations: plastics flexural testing. [6]

ISO 527 — A series addressing tensile properties of plastics. Select the appropriate part and specimen conditions for the material being evaluated.
Names and abbreviations: plastics tensile testing. [7]

ISO 62 — A standard for determining water absorption under controlled conditions. It is not a blanket declaration that a finished assembly is waterproof.
Names and abbreviations: plastics water absorption. [8]

ISO 1133-1 — A standard covering melt mass-flow and volume-flow measurement. Temperature and applied load are essential parts of a reported result.
Names and abbreviations: thermoplastic melt-flow testing. [9]

EN 13501-1 — A classification standard using reaction-to-fire test data. Classification applies within its documented scope, not automatically to every assembly or profile.
Names and abbreviations: reaction-to-fire classification. [10]

ASTM D7032 — A performance-rating specification covering composite and plastic-lumber deck boards, stair treads, guards and handrails. It is not a European approval.
Names and abbreviations: composite decking performance ratings. [11]

EN 15804 — Core rules for construction-product environmental declarations. Meaningful comparisons require compatible rules, declared units, modules and scenarios.
Names and abbreviations: construction-product EPD rules. [12]

[4] [6] [7] [8] [9] [10] [11] [12]

Green Plank products and documentation #

Explore Green Plank product ranges and request the current technical data for your selected profile. These are commercial manufacturer links, not independent evidence for the definitions.

[16] [17] [18] [19] [20]