| Starch is a renewable resource and is commonly used as raw materials for environmentally friendly materials.High amylose starch has a high content of amylose,which has strong intermolecular forces.The materials with it will have excellent properties and have brilliant application potential in food,medicine,materials,and other fields.However,its starch granules are too dense and difficult to be gelatinized,and its closed gelatinization temperature is higher than 100°C,so its practical application is limited.This paper focused on this bottleneck and used calcium chloride solution to disorganize starch granules with different amylose content(waxy corn starch（WCS,the amylose content is 0%）,normal corn starch（NCS,the amylose content is27%）,high amylose corn starch G50（the amylose content is 55%）and G70（the amylose content is 68%）,and discussed the influence of amylose content on the structure and properties of starch/Ca gels and starch/PVA blended films.Based on these,the new starch-based materials were designed and prepared.The main research work of this paper is as follows:For the structure and properties of starch/Ca gels:it was found that the G50/Ca gel and G70/Ca gel did not absorb water after being stored at 57%RH for 30 days,but WCS/Ca gel absorbed water because of its loose structure.At room temperature,the loss modulus（G”）of WCS/Ca gel was higher than the stored modulus（G’）,namely in the fluid state.For NCS/Ca gel,G50/Ca gel,and G70/Ca gel,their G’was higher than G”,meaning that they were in the solid state.Besides,among starch/Ca gels,G70/Ca gel had the highest tensile strength,elongation at break and fracture energy,and G50/Ca gel showed higher tensile strength and fracture energy than those NCS/Ca gel.These indicated that the intermolecular force of the amylose/Ca complex was greater than that of the amylopectin/Ca complex,and with the increase of amylose content,the cohesive force of starch/Ca gels would become more and more strong.The adhesive strength of four starch/Ca gels on corrugated paper was greater than the bonding strength of the corrugated fiber.When bonding wooden boards,G50/Ca gel showed the strongest bonding strength on the board.With a limiting oxygen index（LOI）of about 60,G50/Ca and G70/Ca gel showed excellent flame retardancy,which can be used as fire-retardant materials on papers and wooden boards.Furthermore,based on the good adhesive properties,the G50/Ca gels were used to prepare the wood plastic composite with flame retardancy.For the structure and properties of starch/PVA blended films:starch/PVA blended films were produced by the disorganization-alcohol precipitation-lyophilization-reconstitution process.There were no new chemical groups in the infrared absorption spectrum of starch/PVA blended films,indicating that they were just physical blending.The XRD pattern of blending films showed weak diffraction peaks,indicating the short-range ordered structure.After 30 days of storage,the blended films showed good stability with no change in the diffraction peaks.The elongation at break and tensile strength of the alcohol-precipitated G50/PVA blended film were 165.45±23.53%and21.98±2.38 MPa,respectively,which were better than those of NCS/PVA and alcohol-precipitated G70/PVA blended films.The water vapor transmittance of the three starch/PVA blended films was 950-1050 g·m-2·d-1.NCS/PVA blended film had the strongest water absorption ability,but the surface would fall out slightly after water absorption,indicating that its structure was loose.The results of the antibacterial experiment showed that when the addition amount of tannic acid was 1.15 mg/cm2,the starch/PVA composite film showed an excellent antibacterial effect on E.coli and S.aureus,and its antibacterial rate reached 90%.When the addition amount of PHMG was 0.16 mg/cm2,the starch/PVA composite film showed an excellent antibacterial effect on E.coli and S.aureus and the antibacterial rate was close to 100%.The release kinetics fitting results showed that the tannic acid release rate was slower than that of PHMG but more lasting.Experimental results of wound healing in animals showed that the alcohol-precipitated G50/PVA/PHMG composite film could not promote wound healing,which may be due to its low water vapor transmission rate.In conclusion,by discussing the influence of amylose content on the structure and properties of starch/Ca gels and starch/PVA blended films,this paper designs and prepares the starch-based flame-retardant adhesive and the starch/PVA blended antibacterial film. |
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