Fire Performance of Intumescent Waterborne Coatings with Encapsulated APP for Wood Constructions

Atif Hussain,Christian Dagenais,Doan-Trang Hoang,Véronic Landry,Pierre Blanchet

doi:10.3390/coatings11111272

Atif Hussain, Christian Dagenais + Show 3 more

Open Access

https://doi.org/10.3390/coatings11111272

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Abstract

In this work, intumescent coatings were prepared for protection of wood from fire. The fire-retardant chemical ammonium polyphosphate (APP) is known to have poor resistance to water and high humidity as it is hygroscopic in nature. To improve the water resistance, durability and fire resistance of the intumescent coating, APP was modified using a hybrid organic-inorganic polysiloxane encapsulation shell prepared by the sol–gel method. The physical and chemical properties of the intumescent mix containing microencapsulated ammonium polyphosphate (EAPP) particles were characterized by X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), water absorption, dynamic vapor sorption (DVS) and thermogravimetric analysis (TGA). The EAPP mix showed 50% reduction in water absorption, 75% reduction in water vapor sorption and increased thermal stability when compared to the APP mix. The intumescent coatings were applied on wood samples, and their fire performance was evaluated using a cone calorimeter test. The intumescent coatings containing EAPP mix showed better fire retarding properties with longer time to ignition, lower heat release rate and shorter heat release peak when compared to the coating without EAPP mix. The prepared intumescent coating shows higher resistance to water and moisture, and it has great potential to be used in bio-based construction industry for enhancing the fire resistance of wood.

Highlights

The intumescent coating containing silica encapsulated ammonium polyphosphate (APP) (EAPP Coating) clearly shows a lower water absorption rate when compared to the intumescent coating containing non encapsulated APP (APP Coating)
The water absorption curve of the EAPP Coating stabilizes after 2 h of exposure to 100% relativewood humidity (RH) level
At the end of test, the APP Coating curve shows a steady increase in water absorption predicting that the water saturation is significantly higher than that for the EAPP Coating

Summary

Introduction

Wood is an outstanding material that has been widely used in construction due to its unique properties such as low density, good mechanical and physical properties, environmental friendliness and natural beauty. Some of the major concerns regarding the use of wood products are its durability and flammability [1,2]. Treatments with flame retardant additives have been used for improving the fire resistance properties of wood and delaying fire propagation through building structures [3,4]. In terms of treatment application, coatings are generally preferred over wood impregnation as they are economical, less time consuming and do not cause swelling or shrinkage of the substrate [5]. Coatings provide an insulation barrier isolating the substrate from heat flux and influencing its ignition, thermal degradation and combustion characteristics [6]

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