Preparation Of Biodegradable Polyurethane Foam From Liquefied Bamboo Residues

Converting biomass materials into alternative petrochemical by liquefaction will reduce the dependence on fossil oils of the human society as well as the environment pollution. As one of the byproducts of fast growing biodiesel industry in China, crude glycerol is surplus for the traditional chemical industries, using crude glycerol as liquefaction solvent will not only reduce the liquefaction cost but also significantly reduce the secondary condensation of the lignin fragments in the liquefied mixture. The purpose of this study were to develop a liquefaction process for converting bamboo residues into reactive biopolyols using a solvent mixture consisting of polyethylene glycol 400 and crude glycerol, and to produce biodegradable semirigid polyurethane foams from the liquefied mixture of bamboo residues.Based on the preliminary results from liquefaction of bamboo residues, polyethylene glycol 400 and crude glycerol ratio of 4/1, (w/w) was chosen and used as the liquefaction solvent, and sulfuric acid as catalyst. The effects of key parameters including liquefaction temperature, bamboo/solvent (w/w) ratio, catalyst amount, and liquefaction time on the liquefied bamboo residues products (LB) were determined. At bamboo/solvent (w/w) ratio of 3/10, the effects of catalyst amount, liquefaction temperature, liquefaction time were investigated by the orthogonal test, the optimal parameters were determined as catalyst amount of 4%, liquefaction temperature of 170°C, liquefaction time of 150min. Under optimal condition, LB had low residue rate (0.615%), viscosity 977 mPa·s, hydroxy value 200.39 mgKOH/g, acid value 48.36 mgKOH/g, which satisfied the need for polyurethane foam production. Molecular structure of LB was analyzed using inrprtion absorption spectrum, and confirmed as having abundant -OH groups.A polyurethane foam from LB (LB-PU) was successfully prepared using water as vesicant. The effects of isocyanate index, LB with different bamboo/solvent ratio, water content, catalyst amount, and silicone amount on the mechanical properties of LB-PU foams were determined. Properties of LB-PU including molecular structure, cell structure, and thermal properties were analyzed. FT-IR showed LB-PU foam had same basic structure of carbamate bond with PU foam. SEM photos indicated that the variation of isocyanate index play an important role in the microstructure of LB-PU foam, as isocyanate index increased to 1.0, the cell of foams is uniform and spherical shape, and the mechanical property of the foam was directly related to the microstructure of the foam. The results of TG and DSC analysis showed that LB-PU foams had better heat resistance than conventional PU foams.Soil test were used to study the biodegradability of LB-PU foams. The results indicated that LB-PU foams was biodegradable, to some extent. After eight months, the weight loss of LB-PU foams reached 5.12%, while LB-PU foams added starch reached 6.59%. Through 45 days degradation under controlled composting condition, biodegradation rates of LB-PU foam reached 34.72%, and LB-PU foams added starch reached 38.57%. LB-PU foams added starch degrade faster than LB-PU foams, because starch can be degraded easily than liquefied lignocellulosic material.