Making wooden construction materials fire-resistant with an eco-friendly coating (video)
Coated wood (left) can resist flames, limiting fire damage, unlike bare wood (right). Credit: Ethan Iverson

In terms of deaths and injuries, residential fires and wildfires take a terrible toll. Researchers will report on a new type of coating that could limit the flammability of wood used in construction, potentially providing more time to escape fires and also curtailing their spread. The flame retardant could be used for other materials that could be dangerous.

The results will be presented at the spring meeting of the American Chemical Society.

According to the National Fire Protection Association, home fires account for the majority of fire deaths and lead to billions of dollars in property damage every year. Adding fire sprinklers and smoke detectors can help, but another approach is to make construction materials less dangerous. Thomas Kolibaba is working on a new coating that could make homes safer.

The research was carried out by Kolibaba as a graduate student and post-doc at Texas A&M University, building on the polyelectrolyte coating technology invented by the group in 2009. Most of these coating are formed by dipping fabric or other items in a solution containing one or more of the following: positive or negative charges on it, followed by a dip in another solution containing a different type of material, and then repeating these steps to reach the desired thickness. The opposing charges draw the polyelectrolyte molecule in the alternating layers together into complexes on the item's surface, forming a coating that can extinguish a flame.

The multistep process is not feasible for manufacturers because wood takes too long to soak up the chemicals. He found a way to cut the number of steps down to two: one dip to coat the wood, followed by a dip in a different solution to cure the coating. The streamlined process was not convenient for industrial or consumer applications because the second solution kept turning into a sticky mess.

The latest modification, which will be presented at the spring of 2022, Kolibaba says it would be easy for industry or consumers to adopt. He dipped the plywood in the solution containing the polyethylenimine (PEI), the hydroxyethyl methacrylate (HMP) and a photoinitiator. He exposed the wood to the UV light for a few minutes, instead of dipping it in a second solution to cure. The HMP was turned into a negatively charged polymer by TPO. The coating was transparent and only a few micrometers thick, so it didn't change the wood's appearance or add much to its weight.

In lab flame tests, the treated wood lowered the amount of heat released during burning and quickly formed a surface layer of char that protected the underlying wood. This one is covalently bonding, which is different to the team's prior coating. It is expected to be water-resistant, durable, and possibly also water-repellent.

Industrial users could coat construction materials, such as wooden studs and other framing, or strand oriented board, a type of engineered wood similar to particle board. Homeowners can use a backpack sprayer to protect their structures from wildfires. Other potential applications include textiles and foam for clothing, home furnishings, and the automotive and aviation sectors. The UV-curable polyelectrolytes could be used to make 3-D-printed parts that are safe to use. He notes that it could be beneficial in the International Space Station.

More information: Polyelectrolyte photopolymer complexes for flame retardant wood, ACS Spring 2022. Citation: Making wooden construction materials fire-resistant with an eco-friendly coating (2022, March 22) retrieved 22 March 2022 from This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.