高阻隔薄膜透氣透濕特性的模擬分析
發(fā)布時(shí)間：2018-10-05 17:04
【摘要】：本文利用分子模擬軟件Material studio6.1從微觀角度模擬研究了O_2、CO_2和H_2O三種小分子在高阻隔薄膜PET和EVOH中的滲透過程,計(jì)算得到了擴(kuò)散系數(shù)、溶解度系數(shù)和滲透系數(shù),并探討了溫度、聚合度、分子鏈構(gòu)型因素對滲透過程的影響。本文的主要研究工作包括:(1)在283K、288K、293K、298K、303K和100kPa條件下,分別對O_2、CO_2和H_2O在PET中的滲透過程進(jìn)行了模擬。結(jié)果表明:在同一溫度下,O_2、CO_2和H_2O分子在PET中的擴(kuò)散系數(shù)依次減小,溶解度系數(shù)和滲透系數(shù)依次增大,這表明三種小分子的滲透性能取決于溶解性能;隨著溫度的升高,同一種小分子的溶解度系數(shù)逐漸減小,擴(kuò)散系數(shù)和滲透系數(shù)逐漸增大,這表明溫度對小分子滲透過程的影響取決于擴(kuò)散過程。(2)在298K、100kPa下,分別對O_2、CO_2和H_2O在EVOH中的滲透過程進(jìn)行了模擬。結(jié)果表明:三種小分子相應(yīng)的同種系數(shù)的大小排列在EVOH和PET中是一致的;與PET相比,EVOH由于具有極低的O2和CO2溶解度系數(shù)和較高的H2O溶解度系數(shù),其阻氣性較優(yōu)、阻濕性較差。此外,針對食品包裝中最關(guān)注的阻氧性,模擬了O2在不同鏈結(jié)構(gòu)EVOH中的滲透過程。結(jié)果表明:相比全同立構(gòu)EVOH,間同立構(gòu)EVOH具有更小的自由體積和更低的分子鏈活動(dòng)性,阻氧性更優(yōu);聚合度對分子鏈活動(dòng)性的影響大于對自由體積的影響,因此高聚合度的EVOH具有更好的阻氧性。(3)通過對O_2、CO_2和H_2O分子在高阻隔薄膜PET和EVOH中的滲透過程模擬研究,小分子擴(kuò)散軌跡圖表明這些小分子在聚合物內(nèi)的擴(kuò)散是由長時(shí)間的空穴內(nèi)小幅振動(dòng)和瞬時(shí)的空穴間長距離躍遷相結(jié)合的擴(kuò)散機(jī)制支配;密度場分布圖表明小分子在聚合物中的溶解不是均勻分布,而是主要集中在自由體積較大的地方;通過自由體積分?jǐn)?shù)發(fā)現(xiàn)對于同種氣體、同種聚合物薄膜,自由體積分?jǐn)?shù)越大,擴(kuò)散系數(shù)和溶解度系數(shù)越大。本文的研究工作可為高阻隔性薄膜在食品、果蔬包裝及保鮮貯藏中的工程應(yīng)用提供良好的理論依據(jù)及指導(dǎo)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.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TS206.4;TB383.2
本文編號(hào)：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.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TS206.4;TB383.2
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