| In order to guarantee the safety and quality of food,food packaging industries were facing many challenges.The antibacterial composite film of biodegradable polylactic acid(PLA)and nano titanium dioxide(TiO2)have shown broad prospects.However,TiO2 aggregates easily within the PLA matrix when it was mixed with PLA directly,which can reduce the photocatalytic antibiotic activity.Therefore,a simple and effective method of solution blending was developed.In this work,PLA/TiO2 composite film was made by mixing amophous TiO2 obtained by sol-gel method with PLA solution,and its properties and potential applicationin the preservation packingwere explored deeply.In this work,titanium iso-propoxide(TTIP)was chose as raw material to synthesize amophous TiO2 precursor solution using sol-gel method.TiO2was characterized by Fourier transform infrared spectroscopy(FT-IR),UV spectrum,X-ray diffraction(XRD)and its particle size was studied and optimized.The result indicated the minimum particle size of TiO2 was 6.29-11.1nm when n(TTIP):n(H2O)was 1:2.5 and the amorphous TiO2 was successfully detected by FT-IR and XRD.The preparation technology of PLA/TiO2 composite films were optimized by single factor and response surface methodology and the films achieved optimum at the conditions of 4%PLA concentration,60 min of TiO2 ultrasonic dispersion time,and 200W of the ultrasonic power.The effects of different TiO2 content on the structure and properties of composite films were characterized by FT-IR,XRD,scanning electron microscopy(SEM)differential scanning calorimeter(DSC),and mechanical and water resistance.XRD results showed that the addition of TiO2 could promote the crystallization of PLA.According to the SEM,TiO2 couldbe seen to be evenly distributed in the PLA matrix,and it was easy to reunite when the content of TiO2 was high.Simultaneously,testing of mechanical properties demonstrated that TiO2 could improve tensile strength of the film and reduceelongation at break.DSC results showed TiO2 increased the crystallization temperature and crystallinity of the composite film.The water resistant experiment indicated that the contact angle of PLA/TiO2 composite films was lower than that of pure PLA film due to the hydrophilicity of Ti0Oand the water absorption rate of PLA/TiO2 composite filmswas significantly higher than that of pure PLA film.Besides,the water vapor permeabilityof PLA/TiO2 composite films was higher comparing with PLA film and itgradually increased with the increasing content of TiO2.The photocatalytic properties of PLA/TiO2 composite films were further explored and the results indicated that the photocatalytic activity was greatly influenced by TiO2 under ultraviolet light.The photocatalytic effect was optimal when the content of TiO2 was 0.6%.The PLA/TiO2 composite film containing TiO2 presented a good antibacterial property under the condition of photocatalysis.And the inhibition of Escherichia coli and Salmonella was strongest with TiO2 content of 0.6%and the inhibition of Staphylococcus aureus was strongest with TiO2 content of 0.4%.In this study,pork was chosen as fresh-keeping object.The effect of PLA/TiO2 composite film on the preservation of pork was evaluated by studying and measuring the changes of various fresh-keeping indicators during the period of storage.The results showed that PLA/TiO2 composite films could inhibit the growth of bacteria at 4? a nd 25?,slow down pH value,maintain the sensory quality of pork and reduce the corruption rate of pork to acertain extent. |
PDF Full Text Request