Abstract:

In order to solve the problems of lignin involved in bio-polyurethane foam reaction due to its complex structure, low purity, large molecular weight, and low reactivity, phenolic lignin with high activity was extracted from natural bamboo powder by deep eutectic solvent(DES) prepared by choline chloride(ChCl) and oxalate hexahydrate(Oad) combined with ultrasonic assisted technology. It was used as a reaction monomer to partly replace petroleum-based polyols to prepare lignin-based polyurethane foam(LPUF) via all water foaming method, and the chemical structure, micromorphology and mechanical properties were analyzed. The results showed that the optimal process conditions were the ultrasonic temperature of 80℃, ultrasonic action time of 0.5 h, and ultrasonic power of 70 W. Under these conditions, the content of phenolic hydroxyl groups of the extracted lignin was 8.8%, and the lignin extraction rate reached to 87.8%. The basic structure of lignin was not destroyed by DES ultrasonic assisted treatment, and LPUF was successfully prepared. When the mass ratio of lignin: polyethylene glycol 200(PEG-200): polyethylene glycol 400(PEG-400): hexamethylene diisocyanate(HDI) was 1:84:23:155, the average cell size of the prepared lignin polyurethane foam(LPUF-2) was 261.66 μm, and the elasticity modulus reached to 3 MPa. After 1 000 compression cycles, the maximal stress of LPUF-2 still maintained initial 84%, reached 22.26 kPa, showing excellent mechanical properties and mechanical stability.

Key words: phenolic lignin, deep eutectic solvent, ultrasound, lignin-based polyurethane foam, all water foaming, resilience