Â鶹ÒùÔº

A new bio-based hot glue derived from a byproduct of the wood pulp industry beats traditional epoxy resins and commercial hot-melt glues in terms of adhesive performance.

Researchers from Beijing Forestry University derived from xylan—a complex sugar found in plant cell walls—that can be applied in a molten state and reused over 10 times without any loss of its original strength.

The synthesis strategy was reported in Nature Sustainability.

Adhesives don't just bond materials, they are the backbone of industrial manufacturing in sectors like packaging, construction and electronics. They are often divided into groups—solvent-based adhesives, reactive adhesives, and hot-melt adhesives (HMAs)—based on how they cure (dry or harden).

Unfortunately, most industrial-grade adhesives available on the market are extracted from petroleum-based products, which can have a negative impact on human and environmental health.

Despite being derived from fossil fuels, HMAs have been preferred over other potentially toxic adhesives since their introduction in the 1950s. They are primarily composed of four key ingredients: polymers, which provide strength and control tackiness; resins, which enhance adhesion to various surfaces; waxes, which improve curing speed and heat resistance; and additives, which help boost stability and extend shelf life.

Being solvent-free and solid at room temperature, HMAs must be melted before use. Once applied and cooled, they form strong bonds quickly—delivering excellent mechanical performance without releasing harmful volatile organic compounds (VOCs).

With the world moving towards more sustainable options, researchers have been on the lookout for high-performance, non-toxic adhesives derived from renewable resources.

Several studies have ventured into the extraction of bio-based adhesives from natural sources like soybean protein, starch, chitin, cellulose, and lignin. However, they suffered from limitations such as low bonding strength and lack of reusability.

To synthesize the high-performance bio-based adhesive, the researchers sourced xylan from viscose fiber mills, which were then freeze-dried and oxidized in the sodium periodate (NaIO₄) solution. This step selectively oxidized the 2,3-hydroxyl groups of xylan into aldehyde groups while cleaving the carbon bonds (C2–C3) in the anhydroxylose units, resulting in dialdehyde xylan (DAX).

After purification, the DAX powder was treated with a monobasic sodium phosphate solution, followed by sodium borohydride (NaBH₄), which reduced the hydroxyl groups and yielded the final product, dialcohol xylan (RDAX).

The researchers used the xylan adhesive to bond together some woodchips and found that it exhibited a lap-shear strength—the ability to maintain adhesion when force is applied parallel to the bonded joint—of up to around 30 MPa, a value that surpasses many commercially available HMAs. High-performance hot-melt adhesive (XA) also works well in extreme cold, too, maintaining strong adhesion even at –25°C.

This enhanced adhesion strength traces back to the formation of a continuous layer that mechanically interlocks with the wood by penetrating its vessel pores. At the molecular level, strong adhesion arises primarily from hydrogen bonding and van der Waals forces between the adhesive and the substrate surface.

A biocompatible and reusable adhesive obtained from a waste byproduct strengthens the shift towards a greener and more circular economy.

© 2025 Science X Network