高阻隔薄膜透气透湿特性的模拟分析
发布时间：2018-10-05 17:04
【摘要】：本文利用分子模拟软件Material studio6.1从微观角度模拟研究了O_2、CO_2和H_2O三种小分子在高阻隔薄膜PET和EVOH中的渗透过程,计算得到了扩散系数、溶解度系数和渗透系数,并探讨了温度、聚合度、分子链构型因素对渗透过程的影响。本文的主要研究工作包括:(1)在283K、288K、293K、298K、303K和100kPa条件下,分别对O_2、CO_2和H_2O在PET中的渗透过程进行了模拟。结果表明:在同一温度下,O_2、CO_2和H_2O分子在PET中的扩散系数依次减小,溶解度系数和渗透系数依次增大,这表明三种小分子的渗透性能取决于溶解性能;随着温度的升高,同一种小分子的溶解度系数逐渐减小,扩散系数和渗透系数逐渐增大,这表明温度对小分子渗透过程的影响取决于扩散过程。(2)在298K、100kPa下,分别对O_2、CO_2和H_2O在EVOH中的渗透过程进行了模拟。结果表明:三种小分子相应的同种系数的大小排列在EVOH和PET中是一致的;与PET相比,EVOH由于具有极低的O2和CO2溶解度系数和较高的H2O溶解度系数,其阻气性较优、阻湿性较差。此外,针对食品包装中最关注的阻氧性,模拟了O2在不同链结构EVOH中的渗透过程。结果表明:相比全同立构EVOH,间同立构EVOH具有更小的自由体积和更低的分子链活动性,阻氧性更优;聚合度对分子链活动性的影响大于对自由体积的影响,因此高聚合度的EVOH具有更好的阻氧性。(3)通过对O_2、CO_2和H_2O分子在高阻隔薄膜PET和EVOH中的渗透过程模拟研究,小分子扩散轨迹图表明这些小分子在聚合物内的扩散是由长时间的空穴内小幅振动和瞬时的空穴间长距离跃迁相结合的扩散机制支配;密度场分布图表明小分子在聚合物中的溶解不是均匀分布,而是主要集中在自由体积较大的地方;通过自由体积分数发现对于同种气体、同种聚合物薄膜,自由体积分数越大,扩散系数和溶解度系数越大。本文的研究工作可为高阻隔性薄膜在食品、果蔬包装及保鲜贮藏中的工程应用提供良好的理论依据及指导作用。
[Abstract]:In this paper, the permeation process of three kinds of small molecules, O _ 2C _ 2O _ 2 and H _ 2O _ 2 in high barrier film PET and EVOH were studied by using the molecular simulation software Material studio6.1. The diffusion coefficient, solubility coefficient and permeability coefficient were calculated, and the temperature was discussed. The influence of polymerization degree and molecular chain configuration on the osmotic process. The main work of this paper is as follows: (1) at 283K / 288K / 293K / 298K / 303K and 100kPa, respectively, the osmotic process of O _ 2O _ 2O and H _ 2O in PET is simulated. The results show that at the same temperature, the diffusion coefficients of the two molecules in PET decrease in turn, the solubility coefficient and the permeability coefficient increase in turn, which indicates that the permeability of the three small molecules depends on the solubility, and increases with the increase of the temperature. The solubility coefficient of the same small molecule decreases gradually, the diffusion coefficient and permeability coefficient increase gradually, which indicates that the influence of temperature on the permeation process of small molecule depends on the diffusion process. (2) at 298KN 100kPa, The infiltration process of O _ 2 and H _ 2O in EVOH was simulated respectively. The results show that the homogenous coefficients of the three kinds of small molecules are the same in EVOH and PET, and because of the very low solubility coefficients of O2 and CO2 and the higher solubility coefficients of H2O, the gas resistance and moisture resistance of the three kinds of small molecules are better than those of PET. In addition, O _ 2 permeation process in EVOH with different chain structure was simulated in view of the oxygen resistance of food packaging. The results show that the isomorphic EVOH has smaller free volume and lower molecular chain activity and better oxygen resistance than homostatic EVOH, and the effect of polymerization degree on molecular chain activity is greater than on free volume. Therefore, EVOH with high degree of polymerization has better oxygen resistance. (3) the permeation process of O _ 2CO _ 2 and H _ 2O molecules in high barrier membrane PET and EVOH is simulated. The diffusion path diagram of small molecules indicates that the diffusion of these small molecules in the polymer is controlled by the diffusion mechanism which combines the small vibration in the hole for a long time and the transient long distance transition between the holes. The density field distribution shows that the dissolution of small molecules in the polymer is not uniformly distributed, but mainly concentrated in the large free volume, and the larger the free volume integral is for the same gas, the same polymer film, the larger the free volume fraction is. The greater the diffusion coefficient and solubility coefficient are. The research work in this paper can provide good theoretical basis and guidance for the engineering application of high barrier film in food, fruit and vegetable packaging and preservation and storage.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TS206.4;TB383.2
本文编号：2254171
[Abstract]:In this paper, the permeation process of three kinds of small molecules, O _ 2C _ 2O _ 2 and H _ 2O _ 2 in high barrier film PET and EVOH were studied by using the molecular simulation software Material studio6.1. The diffusion coefficient, solubility coefficient and permeability coefficient were calculated, and the temperature was discussed. The influence of polymerization degree and molecular chain configuration on the osmotic process. The main work of this paper is as follows: (1) at 283K / 288K / 293K / 298K / 303K and 100kPa, respectively, the osmotic process of O _ 2O _ 2O and H _ 2O in PET is simulated. The results show that at the same temperature, the diffusion coefficients of the two molecules in PET decrease in turn, the solubility coefficient and the permeability coefficient increase in turn, which indicates that the permeability of the three small molecules depends on the solubility, and increases with the increase of the temperature. The solubility coefficient of the same small molecule decreases gradually, the diffusion coefficient and permeability coefficient increase gradually, which indicates that the influence of temperature on the permeation process of small molecule depends on the diffusion process. (2) at 298KN 100kPa, The infiltration process of O _ 2 and H _ 2O in EVOH was simulated respectively. The results show that the homogenous coefficients of the three kinds of small molecules are the same in EVOH and PET, and because of the very low solubility coefficients of O2 and CO2 and the higher solubility coefficients of H2O, the gas resistance and moisture resistance of the three kinds of small molecules are better than those of PET. In addition, O _ 2 permeation process in EVOH with different chain structure was simulated in view of the oxygen resistance of food packaging. The results show that the isomorphic EVOH has smaller free volume and lower molecular chain activity and better oxygen resistance than homostatic EVOH, and the effect of polymerization degree on molecular chain activity is greater than on free volume. Therefore, EVOH with high degree of polymerization has better oxygen resistance. (3) the permeation process of O _ 2CO _ 2 and H _ 2O molecules in high barrier membrane PET and EVOH is simulated. The diffusion path diagram of small molecules indicates that the diffusion of these small molecules in the polymer is controlled by the diffusion mechanism which combines the small vibration in the hole for a long time and the transient long distance transition between the holes. The density field distribution shows that the dissolution of small molecules in the polymer is not uniformly distributed, but mainly concentrated in the large free volume, and the larger the free volume integral is for the same gas, the same polymer film, the larger the free volume fraction is. The greater the diffusion coefficient and solubility coefficient are. The research work in this paper can provide good theoretical basis and guidance for the engineering application of high barrier film in food, fruit and vegetable packaging and preservation and storage.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TS206.4;TB383.2
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