# UV stabilizers, antioxidants, pigments and biological protection

Canonical: https://woodplasticcomposite.net/guides/wpc-uv-stabilizers-pigments-biological-durability/
Language: en
Updated: 2026-10-16
Version: 1
Review: AI-assisted English article. Human technical review has not been recorded.

## Summary

Outdoor durability is a system property. A coloured surface, UV additive or biocide claim does not establish that a board will retain every required property outdoors.

## Separate appearance from function

Colour change, surface texture and mechanical retention are different observations. Research on stabilized cap layers examined photodegradation in co-extruded composites. Its value is the connection between a defined surface formulation and its weathering response, not a universal promise of permanent colour. 

UV stabilizers, antioxidants and thermal stabilizers have different functions. Calcium-zinc stabilization is associated with particular PVC formulations; it should not be listed as a mandatory ingredient in every WPC. Pigments and dyes also need to be selected for the actual matrix and exposure.

https://woodplasticcomposite.net/guides/wpc-uv-stabilizers-pigments-biological-durability/#separate-appearance-from-function

## Biological resistance needs moisture context

Forest Products Laboratory work on fungal and moisture durability demonstrates why the wood component cannot simply be ignored after it is embedded in plastic. A separate study of WPC properties after ageing provides an example of evaluating changes in the composite rather than trusting a generic durability label. [R46,R47]

Fungicides, biocides and antimicrobial claims should identify the intended target and the supporting product documentation. An antimicrobial statement does not, by itself, demonstrate resistance to structural decay or suitability for public surfaces.

https://woodplasticcomposite.net/guides/wpc-uv-stabilizers-pigments-biological-durability/#biological-resistance-needs-moisture-context

## A useful exterior specification

Ask for the weathering procedure, exposure duration, measured colour change, retained properties and permitted cleaning method. For Nordic projects, connect the evidence to the actual exposure: shaded damp areas and sun-exposed surfaces present different questions.

Choose maintenance instructions that users can realistically follow. Low maintenance should mean a clear, manageable care regime; it should not be interpreted as permission to leave debris, contamination or damaged connections unaddressed.

https://woodplasticcomposite.net/guides/wpc-uv-stabilizers-pigments-biological-durability/#a-useful-exterior-specification

## Evidence and source scope

[1] Research study; stabilization and weathering.

[2] Official research synthesis; FPL-GTR-303.

[3] Experimental study; natural weathering and potential particle formation.

https://woodplasticcomposite.net/guides/wpc-uv-stabilizers-pigments-biological-durability/#evidence-scope

## Key points



## Comparison





## Sources

1. Influence of a stabilized cap layer on the photodegradation of coextruded high density polyethylene/wood-flour composites — https://research.fs.usda.gov/treesearch/46196
2. Fungal and moisture durability of wood–plastic composites: summarizing 20 years of Forest Products Laboratory research — https://research.fs.usda.gov/treesearch/68010
3. Changes in Wood Plastic Composite Properties After Natural Weathering and Potential Microplastic Formation; Vasiljevs et al. (2024) — https://www.mdpi.com/1999-4907/15/12/2102