Unmodified Plant and Waste Oils as Functional Additives in PU Flooring Adhesives: A Comparative Study

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Chemistry

Background:

• Polyurethane (PU) adhesives are widely used in flooring applications.
• There is a growing demand for sustainable and eco-friendly adhesive formulations.
• Vegetable oils offer a potential renewable resource for modifying polymer properties.

Purpose of the Study:

• To evaluate the performance of polyurethane parquet adhesives modified with various unmodified vegetable oils.
• To compare the mechanical properties, inorganic leaching, and volatile organic compound (VOC) emissions of these formulations.
• To assess the feasibility of using reactive and non-reactive oils as direct replacements or modifiers in PU adhesives.

Main Methods:

• Incorporation of reactive (castor) and non-reactive (rapeseed, sunflower, linseed, used cooking) oils at 10 wt% into a two-component PU adhesive.
• Mechanical property testing according to EN ISO 17178.
• Inorganic leaching analysis using EN 12457-4.
• Volatile organic compound screening via headspace gas chromatography-mass spectrometry (HS-GC-MS).

Main Results:

• All in-house formulations met the EN ISO 17178 mechanical performance limits.
• Sunflower oil exhibited the highest shear strength; rapeseed and castor oils showed stable tensile performance.
• Used cooking oil formulation displayed increased variability and elevated zinc (Zn) and antimony (Sb) leaching.
• HS-GC-MS analysis did not provide high-confidence VOC identifications for regulatory claims.

Conclusions:

• Standard-compliant performance is achievable with 10 wt% loading of both reactive and non-reactive unmodified oils in PU parquet adhesives.
• Physical modification with non-reactive oils can be sufficient, while reactive oils like castor oil may participate in the PU reaction.
• Using unmodified oils avoids additional chemical modification steps, potentially lowering the carbon footprint compared to derivatized oils.