The potential of yeast as eco-filler for waterborne polyurethane and its reinforcing mechanism

• Yeast is proven to be an excellent eco-filler for waterborne polyurethane.
• Highly dispersed PU-yeast composite matrix is obtained.
• PU-yeast composite retains the clarity of polyurethane.
• Thermal stability and mechanical properties of PU-yeast composite are enhanced.
• Yeast acts as craze initiator during plastic deformation.

The potential of using yeast as the eco-filler for waterborne polyurethane (WPU) has been investigated in this research. The composites are synthesized by dispersing yeast into the 3-Triethoxysilyl Propylamine modified WPU solution followed by drying at 85 °C. The effects of yeast on the chemical structure, optical properties, thermal properties and mechanical properties of the polyurethane (PU)-yeast composites have been investigated. Yeast is well dispersed in the composite matrix and can crosslink with the WPU. Unlike many other PU composites, the PU-yeast composite has a higher clarity. It has a better thermal stability than the pure PU. Its stiffness, tensile strength and elongation at break are improved simultaneously because yeast can reinforce the composite with its cell wall and induce crazing during plastic deformation. As a result, yeast is an excellent eco-filler for the WPU and can be a low cost replacement for nano-cellulose.

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