Study on the surface properties of the regenerated polyurethane foam micropowder via cryogenic pulverization and its application

The micropowder obtained by cryogenic pulverizing flexible polyurethane foam (FPUF) as a filler is a waste recycling approach which is highly efficient and eco-friendly. Currently, the micropowder has merely been applied roughly and simply in various fields, so it makes sense to study its surface activity in depth to achieve quantitative and efficient reuse. This paper is focused on studying the surface physicochemical properties of the micropowder and its reactivity and compatibility as a filler in polyurethane elastomers. The FPUF was pulverized into a particle of 0–900 μm. The hydroxyl and amine values of the micropowder surface increased from 48.82, 5.99 mg KOH/g to 73.78, 9.12 mg KOH/g, respectively, with the decrease of particle size range from 500-900 μm to 0–100 μm. However, the amount of substance of effective active hydrogens that could react with NCO groups in the polyurethane prepolymer was uncertain due to the viscosity and temperature. Thus, a preliminary attempt was to quantify the effective active hydrogens by FTIR coupled with titration of the NCO content. The mixture with 5% FPUF-1 micropowder had the maximum effective active hydrogens of 3.30 mmol, which could react with NCO groups to form new chemical crosslinking sites. Compared with the pure PU film, microcrosslinking and strong hydrogen bonding are contributors to the good mechanical properties of the composite. Thus, the FPUF micropowder as an organic filler exhibits considerable potential for converting thermoset FPUF into value-added performance materials.