Preparation And Properties Of Biodegradable PBST/Magnesium Oxide/Ag Composite Films

Poly(butylene succinate-co-terephthalate)(PBST)is an aliphatic-aromatic copolyester with independent intellectual property rights of China.It combines the excellent biodegradability of aliphatic polyester with the good mechanical and thermal stability of aromatic polyesters.The superior properties endow PBST with prospects to be used as food packaging film.Microbial contamination is one of the main reasons for reducing the shelf life of food,so the preparation of antibacterial and biodegradable packaging films has high application value.In this paper,nano-MgO were loaded with Ag to enhance their inherent antimicrobial activity,then PBST/MgO/Ag nanocomposite films were prepared and their application as food packaging materials were evaluated.The specific research content was as follows:MgO nanoparticles(NPs)were prepared by sol-gel method with the magnesium acetate,sucrose,and sodium lignosulfonate as dispersing agent.Ag NPs was loaded on the surface of MgO to prepare MgO/Ag NPs without adding external reducing agent.The nano-composite films were prepared via solvent evaporation method.The properties of NPs and composite films were studied using a variety of analytical methods,such as mechanical properties,barrier properties,thermal properties,antibacterial properties and food preservation properties.The main conclusions were as follows: the loading of Ag could enhance antibacterial properties of MgO.There was no chemical bond between the NPs and the matrix.The dispersion of NPs in the polymer matrix was poor.The addition of MgO/Ag promoted the crystallization of the composite film,improved the mechanical properties,hydrophilicity,UV barrier,water vapor barrier properties,thermal stability and antibacterial properties of the composite films,reduced the initial degradation temperature and light transmittance of the composite films,and the composite film had a better preservation effect on cherry tomatoes.To solve the problem of poor compatibility between MgO/Ag NPs and PBST,γ-aminopropyltriethoxysilane(KH-550),γ-methacryloxypropyltrimethoxysilane(KH-570),adipic acid(AA)and titanate coupling agent(NDZ-130)were used to modify the surface properties of MgO/Ag,the composite membrane containing modified MgO/Ag was prepared.The effects of modified MgO/Ag on the properties of the composite films were studied.The main conclusions were as follows: the surface properties of MgO/Ag were successfully modified.KH-550,KH-570 and NDZ-130 were connected to MgO/Ag through chemical bond,and hydrogen bonds were occurred between AA and MgO/Ag.Compared the composite films with MgO/Ag,the films incorporated with modified MgO/Ag had better dispersibility in the matrix.The composite films with modified MgO/Ag had better mechanical properties,thermal stability,UV barrier properties,and water vapor barrier properties.The antibacterial properties of both were almost identical,and the composite films with modified MgO/Ag had greater application potential as food packaging film.The degradation experiment of PBST composite films was carried out by alkaline accelerated degradation method,and the properties of the composite films before and after degradation were compared.The main conclusions were as follows: during the degradation process,the mass loss rate of the composite film increased continuously.The surface of the films becomes rougher,and holes appear,and the mechanical properties become worse.The initial degradation temperature and light transmittance of films decreased continuously,and the hydrophilicity becomes better,the crystallization temperature,melting temperature and enthalpy increase continuously.The addition of MgO/Ag accelerated the degradation of PBST.