Research On The Liquefaction Processes Of Rice Straw And Its Product Application In The Synthesis Of Polyurethane Materials

In this dissertation, liquefaction rate as an evaluation index was used to evaluate the polyhydroxy alcohol liquefaction reaction of rice straw with different catalysts at the mixed solution of PEG400 and GL. The index values showed that the optimum reaction conditions of glycerin liquefaction were as folllows:(1) sulfuric acid content 3%, straw particle size 20-80 mesh, solid-liquid ratio 1:12, ratio of PEG400 and GL 4:1, liquefaction time 1 h, temperature 180℃ and the residue liquefaction rate 89.33%; (2) copper chloride content 5%, straw particle size 20-80 mesh, solid-liquid ratio 1:11, ratio of PEG400 and GL 4:1, liquefaction time 1 h, temperature 180℃ and the residue liquefaction rate 71.18%.Liquefaction of rice straw with different solvents was carried out, and then five liquefaction processes were obtained. The optimum conditions were as follows:(1) ratio of PEG200 and EG 4:1, rice straw particle size more than 200 mesh, solid-liquid ratio 1:6, sulfuric acid content 3%, liquefaction time 1 h, temperature 180℃ and the residue liquefaction rate 83.05%; (2) ratio of PEG400 and EG 2:1, rice straw particle size more than 200 mesh, solid-liquid ratio 1:6, sulfuric acid content 3%, reaction time 1 h, temperature 180℃ and liquefaction rate 77.20%; (3) rice straw particle size 20-80 mesh, liquid-solid ratio 9:1, sulfuric acid content 6%, temperature 160℃, liquefaction time 1 h and residue ratio 81.41%; (4) ratio of phenol and ethylene glycol 1:4, rice straw particle size 20-80 mesh, liquid-solid ratio 9:1, sulfuric acid content 3%, temperature 180℃, liquefaction time 1 h and liquefaction system of liquefied rate 93.89%; (5) ratio of rice ethylene glycol and glycerol 1:1, straw particle size 20-80 mesh, liquid-solid ratio 9:1, sulfuric acid content 3%, temperature 180℃, liquefaction time 1 h and the liquefaction system of liquefied rate 88.24%.Additionally, in order to further improve the efficiency of liquefaction, we used water as medium to pre process the rice straw under different microwave conditions to study the effect of microwave treatment on the liquefaction efficiency. The results showed that microwave can significantly enhance the efficiency of liquefaction. Performances were then studied including hardness, stretching strength and degradation with the biodegradable polyurethane materials obtained through high-pressure reaction kettle. Compared with conventional polyurethane materials, the biodegradable polyurethane materials prepared with the liquefaction products have a better degradation ability which is environmentally friendly, and their hardness is similar.