Study On Antibacterial And Degradation Performance Of Polylactic Acid Packaging Materials

At present,the most commonly used food packaging materials in the food industry are polyolefin plastics such as PE?PP.This kind of food packaging only plays a simple physical protective role by isolating oxygen,water,microorganisms,etc.,it is difficult to inhibit the spoilage of food caused by microorganisms,and it is difficult to degrade and pollute the environment after use.In this paper,polylactic acid/nano-TiO₂ packaging material was prepared using polylactic acid as the base material and nano-TiO₂ as the antibacterial agent,and the conventional performance,antibacterial performance and degradation performance of the materials were studied.The main findings are as follows:The microscopic morphology of the materials were observed through SEM,and it was found that when 1%nano-TiO₂ was added,it could be evenly dispersed in PLA.The mechanical properties test showed that the tensile strength,elongation at break and impact strength of the packaging materials decreased with the increase of nano-TiO₂content.According to the infrared spectrum analysis,the packaging material contained nano-TiO₂ components and was physically mixed with PLA.Thermogravimetric analysis,Newkirk method and C-R method were used to calculate the thermal degradation activation energy.It can be seen that the addition of nano-TiO₂ improves the thermal stability of packaging materials.DSC analysis and isothermal crystallization showed that nano-TiO₂ could significantly improve the crystallization property of PLA.Antibacterial performance test showed that the antibacterial effect of packaging materials could be significantly improved by adding a small amount of nano-TiO₂.The antibacterial rate of PLA/TiO₂1%against Escherichia coli and Staphylococcus aureus was 81.9%and 84.4%respectively,with the addition amount exceeding 1%,and the antibacterial effect was improved and slowed down.According to the bacteriostatic circle test,nano-TiO₂ was insoluble in PLA.The results show that the packaging material has good long-term antibacterial property.The packaging materials were hydrolyzed and degraded.The water absorption test showed that the addition of nano-TiO₂ improved the hydrophilicity and water absorption of the packaging materials.The weight loss rate test showed that the weight loss rate of packaging materials was not significantly affected,PLA/TiO₂5%lost weight only 0.35%after 65 days of degradation.The change of the apparent morphology of the packaging material was observed by stereomicroscope.PLA became slightly white after degradation,and PLA/TiO₂1%showed discoloration spots on the surface after degradation.By observing the microscopic morphology of the material,it was found that with the extension of hydrolysis time and the increase of nano TiO₂ content,a large number of cavities appeared in the material.The molecular weight of the material decreased significantly after hydrolysis.Compost degradation of packaging materials was carried out.The weight loss rate test showed that the addition of nano-TiO₂ improved the weight loss rate of packaging materials to a certain extent.The apparent morphology of PLA turned white and opaque after degradation,and a large number of cracks appeared on the surface.PLA/TiO₂1%turned slightly yellow after degradation,and cracks and a large number of white spots appeared on the surface.With the extension of degradation time and the increase of nano-TiO₂ content,a large number of cavities and even large cracks appeared in the material.The molecular weight of the material decreases greatly after degradation.