Modification And Application Of Bacterial Cellulose

Bacterial Cellulose(BC)is a natural nano-fiber produced by microbial fermentation with high purity,high crystallinity,high modulus and ultra fine network structure.BC can be used as polymer reinforcement material due to its excellent mechanical properties.Recently,BC has a wide range of applications,such us food,medical treatment,paper making,environment,etc.Polylactic acid(PLA)is a kind of biodegradable material.However,its use in aqueous systems is hampered by limited poor toughness and slow crystallization rate.Generally,with the addition of BC into PLA,biodegradable composites with excellent comprehensive properties can be obtainted.However,OH-groups are abundant in of the surface of BC,which results in the unevenly dispersion of BC in polymer and poor compatibility between BC and polymer.Therefore,it is very important to modify BC to make it more compatibile.Based on the PLA matrix and the reinforcement of bacterial cellulose acetate(BCA)modified by acetic anhydride,PLA/BCA composites were prepared via solution blending with the solvent of dichloromethane.The influence of the dosage of acetic anhydride on the modified BC,the thermal,mechanical,microstructure,crystallization properties and spherulite morphology of the composites were investigated by using fourier infrared spectrum(FTIR),titration reaction,dispersion test,X-ray diffraction(XRD),thermogravimetric analysis(TGA),scanning electron microscope(SEM),electronic universal testing machine,differential scanning calorimetry(DSC)and polarizing microscope(POM),respectively.The results showed that:(1)After acetylation reaction,the hydroxyl in the BC was successfully replaced by acetyl groups.With the increase dosage of acetic anhydride,BC got higher degree of substitution(DS),higher solubility in dichloromethane,but poor network structure and lower crystallinity.(2)The DS of BC had significantly effects on the reinforcemen of cellulose on PLA.With lower DS,BCA can not disperse well in PLA.However,with high DS,the crystal structure and network structure of BC can be destroyed,which resulted in the low reinforcement into PLA.As DS=1.11,mechanical properties and crystallinity of PLA/BCA composites were maximum,so the modification effect was best.(3)With the addition of suitable amount of BCA(DS=1.11),the mechanical properties,crystallinity and thermal stability of PLA/BCA composites can be improved.BCA worked best at 1.0 wt%.(4)Avrami equation can be used to analysis isothermal crystallization of PLA/BCA composites well.Acted as heterogeneous nucleating agent,the addition of BCA can increase the crystallization rate and refine the spherulite size of the composites.The addition of 1.0 wt%BCA was best.