A Dual Active-Passive Coating with Intumescent and Fire-Retardant Properties Based on High Molecular Weight Tannins

Francisco Solis-Pomar,David Rojas,Andrés Felipe Jaramillo,Manuel Francisco Melendrez,María Elizabeth Berrío,Eduardo Pérez-Tijerina,Andrés Díaz-Gómez,Katherina Fernández,Jesús Ramírez

doi:10.3390/coatings11040460

Francisco Solis-Pomar, David Rojas + Show 7 more

Open Access

https://doi.org/10.3390/coatings11040460

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Abstract

In this study, the tannins extracted from the Pinus radiata bark were used to develop an active–passive dual paint scheme with intumescent (IN) and fire-resistant (FR) behaviors. The properties of the coating were observed to depend on the concentration of high-molecular-weight tannins (H-MWT) incorporated into the formulation. At high concentrations (13% w/w), the coating exhibits fire-retardant properties due to the generation of a carbonaceous layer; however, at low concentrations (2.5% w/w), it generates an intumescent effect due to the formation of a carbonaceous foam layer. The dual IN–FR scheme was evaluated against fire by flame advance tests, carbonization index, mass loss, and intumescent effect, and was also compared to a commercial coating. The dual scheme presented good mechanical properties with a pull-off adhesion value of 0.76 MPa and an abrasion index of 54.7% at 1000 cycles, when using a coating with a high solid content (>60%) and the same thickness as those of the commercial coatings. The results of the fire resistance test indicate that the dual scheme generates a protective effect for wood and metal, with an excellent performance that is comparable to that of a commercial intumescent coating.

Highlights

Construction safety considering accidents due to fire is an ever-present concern, requiring the development of new materials capable of offering better fire protection and providing longer escape and rescue times [1,2]
The tannins extracted from Pinus radiata showed a yield of 6.2% for high-molecular-weight tannins (H-MWT) and 15.4% for L-MWT per 100 g of bark
They evaluated the reactivity of formaldehyde against tannin extracts of 1500 to 4800 Da, obtained from aromatic shrubs of the Myricaceae family known as bayberry

Summary

Introduction

Construction safety considering accidents due to fire is an ever-present concern, requiring the development of new materials capable of offering better fire protection and providing longer escape and rescue times [1,2] For this purpose, intumescent and fire-retardant coatings have received great attention. The formation of the protective layer and, the increase in the time that the structure resists flame depends on the coating composition These coatings are composed of three main components: a carbon source (commonly polyalcohols), an acid source responsible for the dehydration of the carbon source and for triggering the intumescence reaction (acting as a catalyst), and a blowing or foaming agent, which is responsible for producing gases that lead to the expansion of the coating. The fire-retardant reaction involves only the first two steps, since no blowing agents are required [10]

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