Preparation And Properties Of Biodegradable PBST/Titanium Dioxide/Copper Oxide/Silver Composite Films

The resource crisis,environmental deterioration and food pollution problems caused by non-biodegradable traditional food packaging materials have been increasingly serious,the preparation of biodegradable antibacterial food packaging has become an increasingly important demand.Poly（butylene succinate-co-terephthalate）（PBST）is a type of aliphatic-aromatic copolyester,which combines excellent biodegradable properties of aliphatic polyesters and well mechanical properties of aromatic polyesters.Adding nano-antibacterial agent into PBST can prepare packaging film with excellent comprehensive performance and extend PBST’s application in food packaging field.In this paper,the TiO₂-CuO-Ag NPs（TCA）and modified TCA NPs were incorporated into PBST to prepare PBST-TiO₂-CuO-Ag composite film（PTCA）.The effects of TCA and modified TCA NPs on the properties of PTCA composite films were investigated.TiO₂ NPs with different crystal types were prepared via calcination method,where titanium tetrachloride（TiCl₄）and ammonium hydroxide（NH₃·H₂O）were used as titanium source and precipitation agent,respectively.The photocatalytic degradation of methylene blue solution（MB）of TiO₂ calcined at 450°C（T-450）was the highest,and the degradation rate reached 45.68%.So,the T-450 NPs were used as matrix for subsequent experiments.CuO-Ag NPs with different proportions of CuO and Ag were prepared using silver nitrate（Ag NO₃）and copper nitrate（Cu（NO₃）₂）as silver and copper sources,sodium borohydride（Na BH₄）and sodium hydroxide（Na OH）as reducing agents and precipitators,respectively.The minimum inhibitory concentration（MIC）results showed that the optimal ratio of CuO and Ag was 9:1.TCA NPs were prepared via wet impregnation method by blending T-450 with CuO-Ag（9:1）.CuO-Ag NPs increased the visible light absorbance of TCA NPs,and 5wt%CuO-Ag NPs increased the degradation rate of TCA NPs to 66.3wt%,and the prepared TCA NPs had well antibacterial activity.The PTCA composite films with different TCA NPs content（1/3/5/7wt%）was prepared by solvent casting method,where TCA NPs and PBST acted as antibacterial agent and matrix,respectively.The effect of TCA NPs on the properties of PTCA films was studied.Compared with pure PBST film,the addition of TCA NPs increased the surface roughness of PTCA film,and the agglomeration phenomenon of high content TCA NPs was obvious,TCA NPs also increased slightly the thickness of PTCA film.The tensile strength（TS）and elongation at break（EB）of PTCA films with 3wt%TCA NPs had increased from 23.17 MPa to 25.07 MPa and439.56%to 574.92%,respectively.The addition of TCA NPs improved the hydrophilicity,water vapor barrier,UV barrier properties and reduced the light transmittance of PTCA films,endowing PTCA films with excellent antibacterial activity.The preservation test of cherry tomatoes proved that PTCA could maintain food freshness and prolong food shelf life.TCA NPs were modified with stearic acid（SA）,lauryl sodium sulfate（SDS）and titanate coupling agent（NDZ-201）,and the composite films were prepared by incorporating modified TCA NPs into PBST.The effect of modified TCA NPs on the properties of PTCA films was explored.The results showed that SA,SDS and NDZ-201 bonded to the surface of TCA NPs via chelating bidentate,physical coating and chemical bonding,respectively.Compared with TCA NPs,the modified TCA NPs had better dispersibility in PBST and had less agglomeration.The mechanical properties,water vapor barrier,UV barrier properties,antibacterial activity and fresh-keeping ability of PTCA films with modified TCA NPs were improved to varying degrees.The modified PTCA films had greater potential as food packaging material.