纸塑复合包装材料中化学物迁移的改进预测模型及其通用性

以真实纸塑包装-化学物-食品体系为依据,基于一维Fick扩散理论,考虑化学物在纸和塑料涂层内具有不同的扩散系数及纸的厚度为有限厚,引入纸和塑料涂层界面处的分配系数,给出初始条件和边界条件,建立迁移预测模型,得到解析解。同时,对模型进行简化处理,分析其用于双层同种塑料-化学物-食品体系的使用通用性,并与Laoubi-Vergnaud模型进行对比分析,结果发现所建模型不仅可用于纸塑复合包装材料中化学物的迁移预测,同时还可用于双层同种塑料包装材料中化学物的迁移预测。     

塑料食品包装材料化学物迁移的数值模拟

基于有限差分方法数值模拟了塑料食品包装材料化学物向食品（模拟物）的迁移及迁移物在食品内的不稳定性。结果表明,扩散系数DP决定了迁移的动力学过程,分配系数KP,F表征平衡时化学物在包装材料和食品内的浓度比值,平衡时食品内的化学物浓度随化学物在包装材料内的初始浓度Cin的增加而增加。对于多层复合包装,阻隔层可显著减缓污染物层内化学物向食品的迁移,从而达到保证食品安全的目的,阻隔层厚度LR影响阻隔功效。化学迁移物在食品内存在不稳定现象,这将导致实验结果低估其向食品的迁移。     

密胺塑料中三聚氰胺在食品模拟物中的迁移规律研究

采用超高效液相色谱串联质谱(UPLC-MS/MS)法,研究食品模拟物种类、接触时间、接触温度、乙酸浓度、乙醇浓度、重复使用和微波加热等迁移条件下,密胺塑料中三聚氰胺在水、4%乙酸(w/v)、10%乙醇(v/v)、95%乙醇(V/V)和异辛烷等5种食品模拟物和牛奶样品中的迁移规律。结果表明:模拟物的属性对迁移行为有显著影响,迁移量随温度的升高和时间的增加而变大。酸性食品和牛奶中的三聚氰胺迁移风险较高,且需控制密胺塑料的使用温度、盛放时间、重复使用次数及微波加热功率和时间以降低密胺塑料中三聚氰胺迁移风险。     

热障涂层体系中各界面失效行为的研究进展

主要介绍了关于高温合金表面热障涂层体系中界面失效行为的研究进展,针对热障涂层中的基体/粘结层界面、粘接层/TGO界面和TGO/陶瓷层界面,进行了高温服役过程中的退化失效及结构演变行为分析,提出了影响热障涂层界面性能的研究重点和方向。     

SA/CS-CaCl2/PMCG新型生物微胶囊的扩散与截留性能

通过测定不同相对分子质量的PEG传递透过SA/CS-CaCl₂/PMCG生物微胶囊的性能,确定了SA/CS-CaCl₂/PMCG膜的截留相对分子质量在2000左右。同时又测量了小分子物质葡萄糖、乳糖、乙醇和谷氨酸在3种SA/CS-CaCl₂/PMCG微胶囊中的扩散性能,并用数学模型计算出了这些物质在不同微胶囊的混合扩散系数D_m以及相应的微胶囊膜层中扩散系数D₁。结果表明： D_m随PMCG浓度的增大先增大而后呈减小趋势,而D₁则随PMCG浓度的增大而增大;并且D₁《D_m,说明微胶囊中的传质阻力主要在微胶囊膜层中。     

不同溶剂对聚丙烯中抗氧剂168迁移规律的影响

研究了含抗氧剂168的聚丙烯(PP)母料的比表面积、溶剂的极性及温度对抗氧剂168向溶剂中迁移规律的影响。结果表明:通过Origin 8.5软件进行模拟,抗氧剂168的浸泡时间(t)和浓度(C_t)符合C_t=A(1-e~(-Bt))方程式,且迁移速度和平衡分配系数(溶剂/塑料)随温度和比表面积的增大而提高,抗氧剂168向正己烷和无水乙醇溶剂中迁移的平衡分配系数(D_r)与比表面积(S)分别符合方程ln D_r=-3.47+2.98e~(-22.3/S)和ln D_r=-6.76+4.29e~(-31.04/S);决定抗氧剂168从PP迁移到溶剂中的迁移量(平衡分配系数)的大小与溶剂、PP和抗氧剂168三者的溶解度参数间的关系有关,即抗氧剂168与PP的溶解度参数差值越大,与溶剂溶解度参数差值越小,溶剂与PP相容性越好(溶解度参数差值越小),则抗氧剂168从PP中的迁移趋势越大,平衡分配系数越高。     

一次性塑料饭盒中双酚A在食品模拟溶剂中的迁移

文章研究了一次性塑料饭盒中的双酚A在不同食品模拟溶剂条件下的迁移规律.实验采用高效液相色谱法对在不同食品模拟溶剂中迁移的双酚A进行了检测.结果表明,双酚A在不同食品模拟溶剂中的迁移量,主要受温度、溶剂极性及萃取方式的影响.随着水浴温度的升高,双酚A迁移量逐渐增加,但由于双酚A易挥发,温度过高时,溶出物中双酚A的量反而减小;相同温度时,在不同食品模拟溶剂中,溶剂极性越小,溶出物中双酚A的迁移量越高;溶剂相同时,不同萃取方式下的迁移量不同,实验表明：一次性塑料饭盒中的双酚A用微波萃取比水浴加热萃取时的迁移量明显增加.     

食品接触用生物降解塑料购物袋材质鉴别与总迁移量研究

采用红外光谱仪（FTIR）对市售的6种食品接触用生物降解塑料购物袋（1^#~6^#）材质进行鉴别,测试了其在不同浸泡条件下的总迁移量,并对部分样品的蒸发残渣成分进行了表征。结果表明,2^#与4^#样品材质定性结果与其标注材质不一致;生物降解塑料购物袋总迁移量远大于传统聚乙烯（PE）塑料购物袋,2^#~6^#样品在4 %（体积分数,下同）乙酸模拟液中浸泡及1^#~6^#样品在95 %乙醇模拟液中浸泡时的总迁移量均超过限量要求（10 mg/dm²）,说明生物降解塑料购物袋直接接触食品存在一定食品安全风险;样品中的PBAT能在95 %乙醇中溶解;样品中掺杂的CaCO₃在4 %乙酸模拟液中出现了大量迁移,这是由于CaCO₃本体发生迁移及CaCO₃与乙酸发生反应生成了乙酸钙;淀粉（ST）颗粒在水中会发生糊化脱落,而乙酸进入ST颗粒中会破坏ST的分子结构,导致掺杂ST的生物降解塑料购物袋总迁移量显著增大。     

垃圾填埋气体抽排影响半径的预测

垃圾填埋气体迁移是对流和扩散效应共同作用的结果。以多孔介质渗流力学和溶质运移理论为基础,结合垃圾填埋气体（LFG）产气特征, 推导了二维极坐标下LFG迁移控制方程, 给出了LFG影响半径的计算模型, 实现了对气井影响关径 R _i的预测及模型参数的灵敏度分析。结果表明,垃圾土渗透率的增大使气体流量增多, 进而扩大了LFG R _i; 扩散效应所引起的气体流量在径向分布相差较大, 是导致不同扩散系数条件下 R _i 变化的主要原因。扩散系数越大使外部与井口流量比值越小, 导致LFG R _i越小;LFG R _i随易降解有机物比例的降低而扩大, 但增幅较小。在填埋高度≤ 10 m的情况下, 有机物组分含量对LFG R _i 的影响并不明显。 R _i技术指标的确定可为垃圾填埋场气井设计及LFG资源化开发利用及评价提供技术参数。     

MFI沸石中Maxwell-Stefan扩散系数与覆盖率的关系

基于描述多孔介质中表面扩散的Maxwell-Stefan（M-S）方程,结合本文动力学Monte Carlo（KMC）模拟及文献中分子动力学（MD）模拟数据,提出了MFI沸石中M-S扩散系数与覆盖率依赖关系的新表达式.该关系式考虑了分子间相互作用以及饱和吸附覆盖量对扩散系数与覆盖率依赖关系的影响,用于预测强受限组分CF₄、弱受限组分CH₄以及中度受限组分Xe等7种单组分在MFI沸石中的M-S扩散系数时,结果较现有其他关系式更为合理.     

A new method for the prediction of diffusion coefficients in poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) is used in several packaging applications, especially for beverages. Due to the low concentration of potential chemical compounds like polymer additives or monomers leached out of the polymers and found in food or beverages, the compliance of a PET packaging material is shown often by use of migration modeling. Diffusion coefficients for migrants, however, are rare in the scientific literature. The aim of the study was to develop an equation for the prediction of diffusion coefficients in PET on the basis of activation energies of diffusion for possible migrants in PET. As a result, a correlation between experimentally determined activation energies of diffusion E_A and the volume of the migrant V was established for PET. In addition, a correlation of the pre‐exponential factor D₀ with the activation energy E_A was found. Combining both correlations lead to an equation where the diffusion coefficients D_P are predictable from the molecular volume V of the migrant. The equation might be useful for migration prediction and consumer exposure estimations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Kinetic migration of PBS and PBSA biopolymers prepared by cast film extrusion and biaxial stretching: A combined experimental and modeling approach

The kinetic migration of poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) biopolymers, prepared by cast film extrusion (thin film) and biaxial stretching (biaxially oriented [BO] film) techniques, were investigated based on experimental and mathematical modeling. MATLAB coding was used to fit the migration data to a diffusion model. BO films significantly reduced the migration rate compared with thin films, with reductions of 29% and 41% for BO-PBS and BO-PBSA, respectively, due to the increased degree of molecular crystallinity. Higher ethanol content increased the quantity of substance diffusing from plastic film. PBS and PBSA are more suitable for packaging hydrophilic foods than alcoholic beverages. PBS exhibited a lower migration rate than PBSA due to its more rigid polymer matrix. Remarkably, BO-films exhibited 31% and 41% lower diffusion coefficients (D) compared with thin films, but significantly higher partition coefficients (K_P,F) by 44% and 267% for BO-PBS and BO-PBSA, respectively. This suggests a stronger affinity of migrant for BO film matrix. However, at 70°C, PBSA films may be hydrolyzed with a high ethanol, resulting in an inadequate diffusion model. The diffusion–reaction concept should be implemented for a better fit. These findings provide valuable insights for selecting appropriate packaging materials and predicting migration under diverse conditions, ultimately promoting consumer safety.     

A unified conjugate mass transfer model of VOC emission

This paper develops a unified conjugate mass transfer model for VOC (Volatile Organic Compound) emission, which implies conjugate boundary condition for mass transfer at the material-air interface. Thus, no special treatment is needed at the material-air interface and numerical methods for conjugate heat transfer problem can be applied directly. The material-air partition coefficient has been taken into account and its effect is the same as specific heat in the energy equation. The equivalent diffusion coefficient in the material K_maD_m instead of D_m characterizes the rate of mass transfer. The ratioK _ma D _m /D _a indicates whether VOC emission is controlled by the internal diffusion or not. The equivalent air-phase initial concentration C₀/K_ma determines the order of maximum concentration in the air. VOC emission contains two stages: the initial stage and the pseudo-steady stage when the emission rate nearly equals mass rate through the outlet of the air. Diffusion coefficient of VOC in the material has a significant effect on VOC emission in the two stages. The effect of partition coefficient on VOC emission depends on the value of K_maD_m/D_a.     

离子液体中的相互作用对硝基苯扩散系数的影响

应用紫外吸收光谱法和循环伏安法研究了离子液体中的相互作用及对离子液体中硝基苯的扩散系数的影响。结果表明,硝基苯的紫外光谱受离子液体EMimBF₄(1-甲基-3-乙基咪唑四氟硼酸盐)与其相互作用的影响,硝基的吸收峰红移,210 nm以下的末端吸收消失,而苯环的吸收基本不变;离子液体与硝基苯之间的作用主要发生在硝基上。在离子液体中电还原,硝基苯的扩散系数受硝基苯与离子液体、水与离子液体的相互作用的影响。同一离子液体中,随硝基苯浓度增加,扩散系数减小。相同硝基苯浓度时,不同离子液体的咪唑阳离子侧链越长扩散系数越小,但扩散系数减小得越缓慢;同一离子液体中,随着水浓度增加,硝基苯扩散系数增大;不同离子液体中,咪唑侧链越长,随着水的浓度增加,硝基苯扩散系数增加越快。     

Determination of the activation energies of diffusion of organic molecules in poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) is a highly inert packaging material that exhibits low interaction with foodstuff and consequently a limited diffusion of migrants. Migration modeling can therefore be used as an alternative to experimental migration tests in order to confirm compliance of PET packaging materials with food laws. The most important factor for predicting migration using mathematical models is the diffusion coefficient of the migrant in PET. However, current models that predict this parameter are typically based on worst‐case scenarios and thereby significantly over‐estimate the degree of migration. The key parameter for developing more realistic migration models is the activation energy of diffusion of potential migrants in PET, but experimental data on this are scarcely available in the scientific literature. The aim of the present study was therefore to develop a fast and precise method for determining diffusion coefficients and activation energies of diffusion of organic compounds in PET. Activation energies of diffusion for 13 organic compounds in PET were determined via their diffusion coefficient temperature dependencies. The molecular weight and activation energy of diffusion for the compounds investigated in this study were correlated, offering a basis for a new approach in predicting diffusion coefficients for use in migration modeling. The proposed method is a suitable tool to establish the datasets needed to refine the current migration model. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

微波条件塑料包装化学物质迁移研究

塑料广泛应用食品于食品包装中,并且常常会在塑料包装加工过程中添加许多化学添加剂以提高其性能,可能会对人的健康产生影响。就微波条件下塑料包装化学物质的迁移进行了研究,采用500,700,900W三个不同加热功率下分别对食品模拟物三种食用油(橄榄油、菜籽油和葵花籽油)的迁移率进行实验。以期对预防塑料包装危害产生积极影响。     

Determination of effective diffusion coefficient and interfacial mass transfer coefficient of bovine serum albumin (BSA) adsorption into porous polyethylene membrane by microscope FTIR-mapping study

Here, a new method for simultaneous determination of diffusion coefficient D and interfacial mass transfer coefficient (or convective mass transfer coefficient) k was proposed for bovine serum albumin (BSA) adsorption into porous polymeric membranes. The experimental data for BSA concentration at different membrane depth and different time were determined from FTIR-mapping measurements. Then the diffusion coefficient D and interfacial mass transfer coefficient k were estimated from the calculated dimensionless concentration data at different time and membrane depth by a trial-and-error method based on the diffusion equation initiated in this paper. The diffusion coefficient D and interfacial mass transfer coefficient k evaluated in this manner are respectively: and . The theoretical concentration values calculated from the determined parameters were compared with experimental reading from FTIR mappings, which showed a good agreement between them, especially for the case of a relatively long-time adsorption.