Effect Of Nucleation Agents On Starch-based Foams

Plastics are widely used in daily life.Although they are derived from non-renewable petroleum resources and cannot be naturally degraded,it causes a negative impact on the environment.As a natural polymer compound,starch is a potential nature polymer to replace traditional plastics due to its wide source,low price,and biodegradability.Recently,a few countries have passed regulations and laws to ban the disposable plastics,which has greatly promoted the research and development of starch-based degradable plastics.One of the particular products,starch-based foam,has showed greatly potential.Based on the previous research results,the effects of traditional inorganic nucleating agents,new organic nucleating agents,and functional bacteriostatic nucleating agents on starchbased foaming materials were studied.The main research conclusions are:1)The effects of calcium carbonate and diatomite on the appearance and properties of starch-based foam materials were studied.With gradual increase of the amount of nucleating agent,appearance of starch-based foam material is gradually flat and smooth,pore size of the material cell is relatively gradually reduced,cell distribution is more uniform,and nucleation effect of calcium carbonate is better.However,when the amount of calcium carbonate is 3%,starch foam material is more able to appear longitudinal cracks and affect overall appearance of foam material.The optimal amount of calcium carbonate is 2%.In this condition,foaming ratio of the material is 5.13,the compressive strength can reach 60.41±2.13 KPa,and the resilience is 84.31%.The optimal addition amount of diatomite is 3%.In this condition,appearance and performance of starch-based foam material are the best.The foaming ratio of the material is 5.20,the compressive strength is 74.55±1.52 KPa,and the resilience is 81.72%.2)Microcrystalline starch and microcrystalline cellulose were used as new nucleating agents.Studies have shown that both of them can maintain the crystalline structure and be evenly distributed in the starch matrix.As those tow nucleating agents' addition increases,appearance and performance of starch-based gradually become better.Although microcrystalline cellulose is better than microcrystalline starch.Starch-based foamed materials with the addition of 7% microcrystalline cellulose show the best appearance and performance,of which the apparent density is 27.33±0.46 kg/m3,the expansion ratio is 5.89±0.48 times,and the compressive strength can reach 54.57±1.16 KPa has 72.18±1.71% recovery and 86.09±1.85% resilience.3)Natural pomegranate skin powder was used as a new kind of functional antibacterial nucleating agent.It established a pomegranate skin powder/microcrystalline cellulose compound system to study the effect of compound nucleating agent on properties of starch-based foam materials.Although pomegranate peel powder shows good compatibility with starch matrix,it has poor nucleation effect on starch-based foam.With compound nucleating agent,the mechanical properties of foam material are significantly improved,and antibacterial performance still remains.With 7% pomegranate skin powder and 3% microcrystalline cellulose,the prepared starch-based foam material has the best bacteriostatic effect and mechanical properties,of which compression strength is 53.14±0.86 KPa,recovery is 77.18±1.71% and resilience is 88.59±1.85%.