Sustainable wood coating transforming from dark liquid to light wood finish

Sustainable Wood Coatings: Turning Waste into Durable Finishes

Elliot Brynn in Climate & Environment December 2025 • 4 min read.

"Explore how innovative techniques are transforming liquefied wood waste into aesthetically pleasing and high-performance polyurethane coatings, reducing reliance on fossil fuels and enhancing wood protection."

Polyurethane (PU) coatings are widely used to protect and enhance wood products, from furniture to flooring. Traditionally, these coatings rely on fossil fuel-derived components, contributing to environmental concerns. The depletion of fossil resources has spurred research into alternative, renewable materials for PU production.

One promising avenue involves using liquefied wood (LW) as a key ingredient in PU coatings. Liquefied wood is created by breaking down wood into a liquid form through solvolysis. However, LW often has a dark color, limiting its appeal for applications requiring lighter finishes. Researchers have been exploring bleaching methods to lighten LW and make it more suitable for a wider range of aesthetic preferences.

This article delves into the innovative process of creating two-component polyurethane coatings from bleached liquefied wood. It examines how bleaching affects the properties of LW and the resulting PU films, offering a sustainable approach to wood protection without compromising performance or appearance.

From Dark Waste to Light Finish: The Liquefied Wood Transformation

Sustainable wood coating transforming from dark liquid to light wood finish

The journey begins with black poplar wood, a fast-growing species. This wood is ground into a fine powder and then liquefied through solvolysis, a process that uses a mixture of polyethylene glycol and glycerol to break down the wood structure. Sulfuric acid acts as a catalyst to speed up the reaction.

The resulting liquefied wood is dark brown, limiting its aesthetic appeal. To overcome this, a bleaching process using hydrogen peroxide is employed. This treatment lightens the LW to a yellowish product, making it suitable for coatings where a lighter color is desired. The bleaching process involves carefully controlled conditions to prevent drastic degradation of the wood material.

Solvolysis: Black poplar wood is broken down into a liquid form using polyethylene glycol and glycerol.
Bleaching: Hydrogen peroxide lightens the dark brown liquefied wood to a more desirable yellowish color.
Two-Stage Process: Bleaching is conducted in two stages, first under acidic conditions, then under alkaline conditions, to maximize color change while minimizing degradation.

Once the liquefied wood is bleached, it's time to create the polyurethane coating. This involves curing the LW with either polymeric diphenylmethane diisocyanate (PMDI) or trimethylolpropane toluene diisocyanate prepolymer (TMP/TDI). These isocyanates react with the hydroxyl groups in the LW to form the polyurethane film. Additives, such as n-octyltriethoxysilane, can be incorporated to further enhance the film's properties, particularly its resistance to water.

The Future of Wood Coatings: Sustainable, Durable, and Beautiful

This research demonstrates the feasibility of creating high-performance polyurethane coatings from bleached liquefied wood. The resulting coatings exhibit comparable mechanical properties to those made from traditional, oil-derived materials. Bleaching enhances the aesthetic appeal of LW, expanding its potential applications.

The addition of n-octyltriethoxysilane significantly improves the water resistance of the coatings, addressing a key limitation of previous LW-based formulations. This makes them more suitable for demanding environments where moisture exposure is a concern.

By utilizing wood waste and renewable resources, this approach reduces reliance on fossil fuels and promotes a more sustainable approach to wood finishing. As environmental awareness grows, expect to see more innovations in bio-based coatings that deliver both performance and ecological benefits.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.15376/biores.10.2.3347-3363, Alternate LINK

Title: Preparation Of Two-Component Polyurethane Coatings From Bleached Liquefied Wood

Subject: Waste Management and Disposal

Journal: BioResources

Publisher: BioResources

Authors: Arnaud Maxime Cheumani-Yona, Franc Budija, David Hrastnik, Andreja Kutnar, Matjaž Pavlič, Pavel Pori, Črtomir Tavzes, Marko Petrič

Published: 2015-04-20

Everything You Need To Know

How is liquefied wood made, and what role does solvolysis play in the process?

Liquefied wood is created through a process called solvolysis, which breaks down wood, such as black poplar, into a liquid form. This involves using chemicals like polyethylene glycol and glycerol, with sulfuric acid acting as a catalyst. The initial result is a dark brown liquid, which then undergoes a bleaching process using hydrogen peroxide to achieve a lighter, more desirable color for various applications.

Why is the bleaching process necessary when creating polyurethane coatings from liquefied wood?

The bleaching process is crucial because the initial liquefied wood produced through solvolysis is dark brown, limiting its use in applications where lighter finishes are preferred. Bleaching with hydrogen peroxide lightens the liquefied wood, making it suitable for a broader range of aesthetic preferences. This involves a carefully controlled two-stage process to maximize color change while minimizing degradation of the wood material, first under acidic conditions, and then under alkaline conditions.

What are the key ingredients, besides bleached liquefied wood, used to create the polyurethane coating, and what is their role?

The two key ingredients used to create the polyurethane coating from bleached liquefied wood are polymeric diphenylmethane diisocyanate (PMDI) or trimethylolpropane toluene diisocyanate prepolymer (TMP/TDI). These isocyanates react with the hydroxyl groups in the liquefied wood to form the polyurethane film. Additionally, additives like n-octyltriethoxysilane can be incorporated to enhance the film's properties, such as water resistance.

How does using bleached liquefied wood in polyurethane coatings contribute to sustainability and reduce reliance on fossil fuels?

Creating polyurethane coatings from bleached liquefied wood helps reduce our reliance on fossil fuels because it utilizes a renewable resource—wood—instead of traditional oil-derived components. By transforming wood waste into a durable and aesthetically pleasing product, this method offers a sustainable alternative that minimizes environmental impact and promotes the use of renewable materials in coating production. There is also a significant move towards using bio-based solvents and additives to further reduce the environmental impact of coatings. More research can be done on the long-term performance and cost-effectiveness compared to traditional coatings.

What are the performance characteristics of polyurethane coatings made from bleached liquefied wood compared to traditional coatings, and what are the long-term implications for the industry?

The resulting polyurethane coatings made from bleached liquefied wood exhibit comparable mechanical properties to those made from traditional, oil-derived materials. This means that the sustainable coatings offer similar levels of durability and protection for wood products. The bleaching process also enhances the aesthetic appeal of the liquefied wood, making it suitable for a wider range of applications without compromising performance. Further studies would need to explore how the coatings perform under extreme weather conditions and how they age over extended periods. More details about the specific mechanical properties like hardness, flexibility, and impact resistance need to be analyzed. Also, an important consideration is whether these sustainable coatings can meet or exceed the performance of traditional coatings while also being environmentally responsible.