Preparation And Study On The Performances Of Cassava Starch-based Foams

The objectives of this work were to prepare starch-based foams from cassavastarch, polyvinyl alcohol, sisal fbers and other additives(blowing agent, plasticizer,filler)using a baking process.The performance of starch-based foams such as density,mechanical properties, water absorption properties, combustion performance, thermalstability, retrogradation and microstructure were studied in this paper. Some importantresults can be drawn below:1. The experimental results showed that when the foaming temperature of120℃, soak time for7h, plasticizer dosage of30~35phr, dosage of foaming agent for2~3phr, the dosage of the nucleating agent for5phr, the foaming process for starch--based foams was the best. When the proportion of formamide and dicyandiamide was25:10, the foam material not only had good mechanical properties but also had smalldensity, in addition, it had some flame retardant performance. Azobisformamide asfoaming agent, the foaming effect is better than sodium bicarbonate and foam powderpuff.2. The performance of the acetate starch preparation foam is superior to Theoriginal starch foams performance. The performance of starch based foams could beeffectively improved by adding polyvinyl alcohol.When the dosage of polyvinylalcohol at30phr, the density of material reached the minimum value (0.261g/cm3)and the mechanical performance was the best (1.98Mpa), in addition, the foambibulous rate was reduced to50%.3. The foaming effect of the ternary mixture (starch/polyvinyl alcohol/sisal)was worse than the binary mixture (starch/sisal). Added the sisal fiber couldeffectively enhance starch based foams, when the dosage of the sisal was15phr, thedensity of foam was minimal (0.292g/cm3) and the compression strength attained to 4.08Mpa. The bibulous rate of the foam was gradually reduced with the increase ofdosage of sisal.4. When the dosage of the magnesium hydroxide and aluminum hydroxide was20phr, the vertical combustion of foams could reach grade V-0, the oxygen index ofthe foam was30.2%with the magnesium hydroxide as fire retardant, however theoxygen index of the foam was28.8%with the aluminum hydroxide as fire retardant.The thermogravimetric analysis showed that magnesium hydroxide could effectivelyimprove the thermal stability of the foam. In terms of mechanical properties, thecompression strength of the foam which the magnesium hydroxide filled was morethan3.11Mpa and was about13%higher than that of aluminum hydroxide, besidesthe apparent density of the former (0.266g/cm3) was smaller than the latter by about8%.