Study On The Preparation And Properties Of The Hybrid Composite Films On PLA Film Via Sol-gel Process

With oil and non-renewable resource consuming and white pollution increasingly serious,the preparation of a new type of biodegradable packaging materials has become a research hotspot. Polylactic acid （PLA） is a kind of biodegradable and environment-friendly aliphaticpolymer materials, in the environment can be completely decomposed into carbon dioxide andwater by the microbe. However, oxygen, water vapor, carbon dioxide and small organicmolecules and so on can easily through the PLA film, which limit the application of PLA as apackaging material.Therefore, In our work, in order to improve the barrier property of PLA film. Via sol-gelprocess was used in SiO₂coating on PLA film. Tertaethoxysilane（TEOS） was used as theprecursor. The KH560was used as a coupling agent. Besides, absolute alcohol was used as thecosolvent and hydrochloric acid was used the catalyst. Then, Hydroxypropyl methylcellulose（HPMC） and stearic acid（STA） were used as the organic compounds to prepare theHPMC/SiO₂hybrid composite film and STA/HPMC/SiO₂hybrid composite film. Finally, threekinds of composite films consisted of PLA film and the coatings were prepared. The structure ofthese films was charactered and properties was measured. The main conclusions are as follows:For the SiO₂composite films, the optimum experimental conditions of preparation barriercomposite films had been obtained through the orthogonal experiment and single factorexperiment. The molar ratio of （TEOS+KH560）: deionized water: absolute alcohol: hydrochloricacid was optimized at1:3:3:0.3, and the molar ratio of TEOS to KH560was3:2. Then, oxygenbarrier properties, water vapor barrier properties and tensile strength of PLA/SiO₂compositefilms was9.6times,1.7times and1.08times that of the bare PLA film. The PSiO₂compositefilms had a good transparency.For the PLA/HPMC/SiO₂hybrid composite films, HPMC combined with SiO₂by Si-O-Ccovalent bond and C=O bond, which formed a dense organic-inorganic network structure. As increased the HPMC content, the barrier properties of PLA/HPMC/SiO₂hybrid composite filmswas increased firstly and then decreased. As the Volume fraction of HPMC increased to6%, theoxygen barrier properties, water vapor barrier properties and tensile strength ofPLA/HPMC/SiO₂hybrid composite films was36times,3times and1.13times that of the barePLA film. At the same time, The PLA/HPMC/SiO₂hybrid composite films had a goodtransparency.For the PLA/STA/HPMC/SiO₂hybrid composite films, hybrid composite film and the PLAsubstrate film was closely adhere. No creaking and no phase separation were observed on thesurface of the coating. Along with the increase content of STA, the oxygen barrier properties ofPLA/STA/HPMC/SiO₂hybrid composite films was rised firstly and then reduced, while thewater vapor barrier property of the hybrid composite films continue to rise. As the Volumefraction of STA increased to5%, the oxygen barrier properties, water vapor barrier propertiesand tensile strength of PLA/STA/HPMC/SiO₂hybrid composite films was80.6times,7.3timesand1.16times that of the bare PLA film. At the same time, Because of the light transmission ratewas more than90%, The hybrid composite films of PLA/STA/HPMC/SiO₂still had a goodtransparency.