# WPC fire behaviour: LOI, cone calorimetry and flame retardants

Canonical: https://woodplasticcomposite.net/guides/wpc-fire-performance-loi-cone-calorimetry/
Language: en
Updated: 2026-10-16
Version: 1
Review: AI-assisted English article. Human technical review has not been recorded.

## Summary

A flame-retardant additive can change burning behaviour, but product fire performance must be established using the relevant test and end-use construction.

## Know what the measurements describe

Limiting oxygen index, or LOI, concerns the oxygen concentration needed to sustain burning under a specified procedure. Cone calorimetry can measure heat release under an imposed heat flux; peak heat-release rate is one result. Neither measurement is interchangeable with a building-product classification. [R19,R44]

Research has investigated ammonium polyphosphate, phosphorus/nitrogen systems, melamine-related additives and biochar-containing formulations. Their effects depend on the complete composition. A study of modified bamboo biochar in PLA reported burning-test improvements for its tested specimens. It does not qualify an unrelated WPC cladding system.

https://woodplasticcomposite.net/guides/wpc-fire-performance-loi-cone-calorimetry/#know-what-the-measurements-describe

## Compare systems rather than additive names

Another investigation combined a bio-based TPU, rice husk and ammonium polyphosphate. This is a different matrix and formulation from conventional PE decking. Results should remain attached to that distinction.

https://woodplasticcomposite.net/guides/wpc-fire-performance-loi-cone-calorimetry/#compare-systems-rather-than-additive-names

## Questions for a façade enquiry

Ask which product, thickness, surface and installation build-up were tested. Request the classification document and its field of application. Verify that the proposed backing, cavity, insulation and fixing arrangement fall within the documented use.

For an experimental formulation, evaluate conditioned properties and processing behaviour alongside burning results. A laboratory improvement is useful development evidence, but procurement needs the completed product and installation evidence.

Avoid the word fireproof for ordinary wood–polymer composites. A precise fire-performance description is more useful to an architect and more defensible than an absolute promotional label.

https://woodplasticcomposite.net/guides/wpc-fire-performance-loi-cone-calorimetry/#questions-for-a-fa-ade-enquiry

## Evidence and source scope

[1] Experimental study; publisher abstract/search extract consulted.

[2] Experimental study; laboratory burning behaviour.

[3] Experimental study; TPU system.

https://woodplasticcomposite.net/guides/wpc-fire-performance-loi-cone-calorimetry/#evidence-scope

## Key points



## Comparison





## Sources

1. Mechanical, Thermal, and Fire Retardant Properties of Rice Husk Biochar Reinforced Recycled High-Density Polyethylene Composite Material (2023) — https://www.mdpi.com/2073-4360/15/8/1827
2. Fabrication of Phytic Acid/Urea Co-Modified Bamboo Biochar and Its Application as Green Flame Retardant for Polylactic Acid Resins — https://www.mdpi.com/2073-4360/15/2/360
3. Eco-Friendly Flame-Retardant Construction Composites Based on Bio-Based TPU, Recycled Rice Husk, and Ammonium Polyphosphate — https://www.mdpi.com/2075-5309/15/18/3420