Preparation Of Biomass-based Polyol And Its Application In Degradable Polyurethane

Due to the deteriorating environment and the increasing shortage of resources,biomass resources,which are widely sourced,renewable and easily degradable,have been gradually attached to people,and the development and utilization of biomass resources have become a hot research topic in recent years.Polyurethane materials are widely used in insulation materials,coatings,elastomers and other fields because of their simple production process,low cost and excellent stability.The preparation of traditional polyurethane must use polyol,which comes from petroleum and is not renewable.For this key problem,making full use of biomass resources instead of petrochemical resources is a hot research topic nowadays.In this paper,two bio-based polyols were designed and prepared using epoxidized soybean oil and corn starch as raw materials,and used to prepare biodegradable polyurethane foam with excellent mechanical properties and degradation performance.The main contents and results are as follows:(1)A green process technology for the preparation of soybean oil polyol by ringopening reaction of epoxidized soybean oil with ethylene glycol was developed.The effect of catalyst amount,reaction time and temperature on the ring opening rate of epoxidized soybean oil and hydroxyl value of the product was investigated by single-factor method.The optimum reaction conditions were: the amount of itaconic acid was 0.5 wt%,and the reaction was carried out at 140℃ for 2 h.By then,the ring opening rate of epoxidized soybean oil was as high as 97.5%,the hydroxyl value of soybean oil polyol was 326.2±20 mg KOH/g,the acid value of soybean oil polyol was 0.06±0.02 mg KOH/g,the water content was0.37±0.05%,and the viscosity was 1508±20 m Pa·s.(2)A green process technology was developed for the preparation of bio-based polyol from enzymatically liquefied starch with high efficiency.The effects of liquid-to-solid ratio,amylase dosage,liquefaction temperature and liquefaction time on the starch liquefaction rate and hydroxyl value of the product were investigated.The optimum conditions were as follows: liquid-solid ratio 1:1,amylase dosage 0.8 wt%,liquefaction temperature 95℃,and liquefaction time 1.5 h.The starch liquefaction rate was 98.2%,and the hydroxyl value of the resulting starch liquefaction polyol was 435±20 mg KOH/g,acid value 0.04±0.02 mg KOH/g,water content 0.43±0.5%,and viscosity 430±20 m Pa·s.The comprehensive performance index of the polyol was better than that of the national standard "GB/T 12008.2-2010".(3)Bio-based polyurethane foams were prepared from two self-made bio-based polyols.The foams were tested and analyzed for FT-IR,foaming curve,mechanical properties,SEM,thermal stability,degradation properties,bio-carbon content and thermal conductivity.The results showed that the mechanical properties of the two foams were comparable to those of the petroleum-based counterpart,with the highest compressive strength of 260.4 KPa for the starch-based polyurethane foam and the lowest compressive strength of 207.5 KPa for the soybean oil polyurethane foam;The foaming curves of the three foams were basically the same,with all of them reaching the top of the bubble in about 120 s,but the time to reach the top of the bubble was shorter for the starch-based polyurethane foam;In terms of thermal stability,soybean oil polyurethane foam showed the best thermal stability;In terms of degradation performance,starch-based polyurethane foam had the highest degradation rate of 31.8% degradation in 30 days,soybean oil polyol degraded 15.5%,while petroleum-based polyurethane foam only degraded 1.0%;The bio-carbon content of the three was the highest35.8% for starch polyurethane foam,28.7% for soybean oil polyurethane foam,and zero bio-carbon for petroleum-based polyurethane foam;The highest thermal conductivity of the three was 0.038 W/(m·K)for soybean oil polyurethane foam and 0.021 W/(m·K)for starchbased polyurethane foam similar to petroleum-based.