New study demonstrates CH-Bioforce lignins as promising building blocks for pressure-sensitive adhesives

A new peer-reviewed study has explored how lignins produced with CH-Bioforce’s BIOFORSENSE® technology can be transformed into soft, functional materials for pressure-sensitive adhesives (PSA). These adhesives are widely used in everyday products such as sticky notes, labels, tapes and the well-known Blu Tack®.

The research investigated lignins from birch, spruce and wheat straw, all produced with the CH-Bioforce process, and evaluated how they perform when grafted with poly(n-butyl acrylate) (PnBA). The work highlights how bio-based lignin can replace fossil-based polymers in entirely new adhesive applications.

Modified lignins successfully grafted with polyacrylate

The researchers first prepared lignin-based macroinitiators and then grafted them with PnBA using ATRP polymerisation.
The study confirmed:

• Successful lignin–polyacrylate grafting, verified through FTIR, NMR and SEC/GPC
• Clear differences between hardwood, softwood and straw lignins in macroinitiator formation and polymerisation efficiency
• Birch and spruce lignins showed the most effective copolymerisation behaviour, while wheat straw lignin displayed lower reactivity due to structural complexity

Gel permeation chromatography further demonstrated clear molecular-weight shifts, distinguishing true copolymers from simple blends.

Thermal and rheological properties support adhesive performance

The resulting lignin-g-PnBA copolymers displayed:

• Increased glass-transition temperatures compared to pure polyacrylate
• Structural differences between lignin sources reflected in their thermal decomposition profiles
• Strong viscoelastic behaviour, with birch-based copolymers showing particularly good performance in rheology tests
• Compliance with the Dahlquist criterion, the established requirement for pressure-sensitive adhesives (low modulus under deformation)

Notably, birch-lignin-based materials (BLNBA2 and BLNBA4) showed adhesive behaviour comparable to commercial Blu Tack®, confirming excellent tack and softness in real-world use.

Lignin as a renewable route to soft, functional adhesive materials

This study provides strong evidence that CH-Bioforce lignins can be converted into soft, elastic materials suitable for PSA applications.
Unlike conventional petroleum-based polymers, lignin offers:

• Rapid renewability
• A high-value outlet for side streams
• The potential to reduce fossil-based content in consumer products
• Compatibility with circular economy principles

By demonstrating high-performing, lignin-based PSA materials, the research opens the door to sustainable alternatives for everyday adhesive products.

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