The Preparation And Characterization Of Bio-based Polyols And Polyurethane Foams

Bagasse and corncob were liquefied by microwave heating in the mixture ofpolyethylene glycol and glycerin as liquefying reagents in the presence of sulfuric acid ascatalyst by microwave heating. Rigid polyurethane foam was prepared from the liquefactionproducts and diisocyanates in the presence of catalysts and other additives. The polyurethanefoam was also prepared from phosphorus-modified liquefaction products of corncob.The impacts of reaction time, temperature, microwave power and the dosage of sulfuricacid on the liquefaction behavior were discussed. Both bagasse and corncob could be readilyliquefied by both microwave heating and oil-bath heating, but the liquefaction time bymicrowave heating was reduced by at least75%in contrast to that by oil bath heating. It wasfound that lignin and hemicelluloses degraded faster than cellulose. Cellulose in amorphousregion degraded faster than that in crystalline region did. Almost all the components in plantfiber can be liquefied if the liquefaction time is long enough.Corncob was liquefied in the mixture of polyethylene glycol (PEG400) and glycerin（3/7，by mass）as liquefying reagent using sulfuric acid as the catalyst. Then aphosphorus-containing liquefaction product was synthesized by reacting phosphorusoxychloride (POCl3) with the liquefaction product of corncob. The reaction time, the reactiontemperature and the dosage of phosphorus oxychloride as three parameters were investigatedto find optimal reaction conditions. The thermal stability of modified products wascharacterized by thermogravimetric analysis (TGA). It was found that the reactiontemperature had little influence over the thermal stability of modified liquefaction products,while the dosage of phosphorus oxychloride and the reaction time had big influence over thethermal stability of modified liquefaction products. The thermal stability of the modifiedproducts was better than ordinary liquid products. The effect of modified liquefactionproducts was further investigated by the analysis of rigid polyurethane foams that preparedfrom the modified compound, which was replaced a part of traditional polyether polyol. Thedensity of foam was less than that of the foams prepared from unmodified liquefactionproduct, and the strength of foams was a little improved when the modified compounds wasused in the preparation of polyurethane foams. The thermal stability of foams prepared frommodified products was improved. The density, the compressive strength, the thermaldecomposition temperature and the limiting oxygen index of the polyurethane foam weretested. Increasing the addition of modified products, the density of polyurethane foam willrise. The residue of polyurethane foam prepared with modified liquefaction products was12 at700°C, which was more than that of foam prepared with liquefaction products. Moreover,the limiting oxygen index (LOI) of polyurethane foam prepared with modified liquefactionproducts was26, which was higher than that of PUF prepared with unmodified liquefaction.