Preparation And Characterization Of Chitosan/Polyhedral Oligomeric Silsesquioxane Composite Films

Development of biodegradable polymer materials to replace or reduce the use of synthetic plastics,can effectively alleviate the worldwide shortage of oil resources crisis and the ‘white pollution' problem caused by plastic waste.Among them,chitosan(CS)-based biodegradable film is one of the hotspots.However,the fatal disadvantages,such as poor mechanical properties and weak water resistance of chitosan-based film have largely limited its commercial applications.In recent years,the emergence and rapid development of nanotechnology have provided a new idea and direction for improving the properties of chitosan-based materials.In this study,polyhedral oligomeric silsesquioxane(POSS)and oxide graphene(GO)were used as nano-fillers to fabricate chitosan-based composite films by solution blending casting method,aiming to improve the mechanical properties and moisture resistance of chitosan film.Firstly,water-soluble Octa TMA POSS(POSSA)was selected as the filler to investigate the effects of POSS concentration on the film structure and properties;Secondly,three kinds of hydrophobic POSS carrying alkyl groups,amine group and carboxyl group,respectively,were selected as fillers,to compare the effects of POSS structure on the structure and performance of composite films;Thirdly,POSS Amid Acid-lsobutyl was pre-treated by wet ball-milling to enhance its dispersibility in film,in order to study the effects of dispersion state of POSS on the properties of films;Finally,POSSD after wet ball-milling and GO were incorporated into chitosan films to explore the synergy effects of these two nanoparticles on the performance of composite films.The rheological propertes,micro-morphologies,crystal morphology,contact angle,swelling ratio,solubility,water vapor adsorption isotherm,water vapor permeability,tensile properties,as well as dynamic mechanical behaviors of the prepared composite films were characterized.The main results are as follows:1.Addition of POSSA with certain amout improved the water vapor barrier properties and moisture resistance of the composite films.When the loading amount of POSSA was 3%,the water vapor permeability(WVP),swelling ratio and solubility of the composite films was 15.9%,36.9% and 28.0% lower than that of the pure chitosan film,while the tensile strength and Young's modulus were increased by 13.7% and 21.4%,respectively.2.Incorporation of three kinds of hydrophobic POSS(POSSB,POSSC and POSSD)individually into chitosan films improved the hydrophobicity and moisture sensitivity of films,enhanced their water vapor barrier properties and tensile properties.However,the improvements were dependent on the structure of POSS.Among the three kinds of POSS,POSSD with carboxyl groups presented the best dispersibility in the films,which also showed the highest improvements on the properties of the films.When the loading amount of POSSD was 5%,the WVP,swelling ratio and solubility of the composite films was 20.4%,30.4% and 30.9% lower than that of the pure chitosan film,while the tensile strength and Young's modulus were increased by 9.6% and 16.7%,respectively.3.When POSSD was pre-treated by wet ball-milling(POSSD-WBU),its dispersibility in chitosan was further enhanced,therefore the mechanical properties,water resistance and barrier properties of the films were further improved.When the loading amount of POSSD-WBU was 3%,the composite film showed the best performance with the WVP,swelling ratio and solubility decreasing by 20.4%,33.2% and 33.7%,while the tensile strength and Young's modulus increasing by 17.8% and 45.7%,respectively,compared to the neat chitosan film.4.The combined application of GO and POSSD after wet ball-milling further improved the performance of composite films.The addition of GO increased the crystallinity of the composite films,and enhance the dispersibility of POSSD in the film.Compared with the composite films containing the same amount of GO or POSSD alone,the WVP,swelling degree and solubility rate of the CS/GO/POSSD-WBU composite film were significantly lower.Furthermore,these composite films showed excellent mechanical properties,with the WVP,swelling ratio and solubility decreasing by 28.8%,38.0% and 36.6%,while the tensile strength and Young's modulus increasing by 48.1% and 42.2%,respectively,when the loading amount of POSSD-WBU was 3%,compared to the neat chitosan film.