POLYURETHANE FOAMS MADE FROM COMBINED LIQUEFACTION MIXTURES OF BAMBOO RESIDUES AND STARCH

Abstract

The goal of present investigation is to produce high biomass content biopolyol,which has the potential of replacing the expensive polyether polyol in manufacturing of polyurethane foams,through a thermochemical liquefaction process by using bamboo residues combined with corn starch as raw material.Single factor experimental design was adopted to test the effect of the composition of liquefaction reagent,the different liquid ratio and the proportion of bamboo to starch on the physical and chemical properties of the resulting liquefaction products.Polyurethane foam was prepared by using this liquefaction products instead of polyether polyol.Finally,the physical mechanical properties and biodegradability of the resulting polyurethane foam were determined according to the simplified ASTM D5338-98 test method.The experimental results showed that the best resulting biopolyol was obtained by using 50 wt% of ethylene carbonate+50 wt% of ethylene glycol as complex liquefaction solvent,adding 3 wt% of fuming sulfuric acid to liquefaction solvent as catalyst,under the reaction temperature of (150±5)℃ (oil bath) and atmosphere pressure,and the reaction time lasted for 150 min with constant agitation within present experimental design.Only less than 30% of the bamboo residues can be well dissolved in the complex solvent due to the tendency of secondary condensation of the liquefied components.In order to reduce the production cost of the biopolyol by increasing its biomass content,15 wt%～25 wt% of bamboo residue combined with 125 wt%～135 wt% of corn starch over the liquefaction solvent was liquefied stepwise.The viscosity of the liquefaction mixture resulting from the combined liquefaction of 25 wt% bamboo residue and 125 wt% corn starch is as high as 8.85 Pa·s,which is not suitable for polyurethane foam preparation,and the polymer segment content in the liquefaction product of the pure bamboo residues was so low that the resulting polyurethane foam collapsed badly.When combined liquefaction mixture of 20 wt% of bamboo residue and 130 wt% of corn starch was blend with 4,4′-diphenylmethane diisocyanate (MDI) and the other additives with the molar ratio of (—NCO/—OH) equal to 1.1,polyurethane foams with acceptable mechanical properties:apparent density of 33.6 kg/m~3,compressive strength of 118 kPa and elastic modulus of 6.91 MPa were obtained.The biodegradability determined was 12.63%, expressed by weight loss in one year round.