纳米粒子的结构对EVOH纳米复合物性能的影响

为研究纳米填充物对EVOH基体性能的影响,采取熔融共混的方法,用EVOH-56作为基体,按照不同比例填充了化学结构或聚集态结构不同的纳米粉体,从而制备出不同的EVOH纳米复合体系。根据TPT方程,计算出与复合体系中各组分间相互作用相关的参数B值,EVOH-56/纳米TiO_2复合材料的B值(16.493)大于EVOH-56/纳米ZnO复合材料的B值(3.806);随着纳米粉体含量的增加,两种复合物体系的熔体温度升高约6%;而在相同纳米粉含量条件下,EVOH-56/纳米ZnO体系的加工扭矩比EVOH 56/纳米TiO_2体系低5%～10%;在力学性能方面,EVOH-56/nano-ZnO体系的屈服强度值和弹性模量值均优于EVOH 56/nano-TiO_2体系。     

PVA/EVOH纤维力学性能研究

通过凝胶纺丝获得PVA／EVOH纤维，当纺丝原液浓度为16％而PVA／EVOH配比低于93／7时即会形成凝胶。为了获得可纺性较好的原液和避免凝胶的产生，配制了不同比例的PVA／EVOH(100／0，98／2，97／3和95／5)的纺丝原液。通过凝胶纺丝获得PVA／EVOH初生纤维经过拉伸后，可获得不同机械性能的纤维。另外，在PVA中加入少量的EVOH可以提高拉伸倍数，适当的PVA／EVOH配比及适当的拉伸倍数可获得机械性能较好的纤维。     

气相色谱-质谱联用法检测乙烯-乙烯醇活性食品包装膜中的香叶醇和α-松油醇

建立乙烯-乙烯醇包装膜中活性物质香叶醇和α-松油醇的气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)联用检测方法。实验首先讨论了样品前处理条件和GC-MS测定条件,对迁移至模拟液中的活性物质采用所建方法检测,外标法定量分析。结果表明香叶醇和α-松油醇在0.02~2.0 mg/L范围内均线性关系良好,相关系数分别为0.999 2和0.999 0。该方法的检出限分别为0.003 mg/kg和0.007 mg/kg,定量限分别为0.010 mg/kg和0.020 mg/kg。以0.1、0.2 mg/kg和1.0 mg/kg添加水平进行方法学验证,回收率为82.5%~98.5%,相对标准偏差为3.6%~10.4%。本方法快速、简便、灵敏度高,可为进一步研究活性物质在食品包装材料中的释放机理及活性食品包装膜的应用安全性方面提供有效的检测方法。     

乙烯-乙烯醇与聚丙烯共混物的形态及性能

以聚丙烯接枝马来酸酐(PP-g-MAH)为增容剂,共混聚丙烯(PP)与乙烯-乙烯醇(EVOH)制备可润湿性PP.用扫描电镜(SEM)、动态粘弹谱仪(DMA)和差示扫描量热仪(DSC)分析了EVOH/PP共混物的形态结构、力学性能和热性能.用接触角测定仪表征了共混物的可润湿性.SEM结果表明共混物呈明显两相结构,EVOH...     

HDPE/EVOH共混物结晶行为研究

使用示差扫描量热方法对聚乙烯接枝马来酸酐相容改性的HDPE／EVOH共混体系的结品行为进行了研究。实验发现相容作用对HDPE／EVOH共混物中两组分的结晶行为有较大影响,由于熔融共混过程中相容剂与EVOH之间形成的EVOH-g-HDPE对EVOH的结晶具有阻碍作用,导致EVOH分散相的结晶速度下降,晶粒尺寸分布变宽,结晶熔点和结晶度明显低于共混前纯组分。共混物中EVOH分散相对HDPE基体的结晶具有异相成核作用,而且相容作用使异相成核更加明显,从而使HDPE相结晶速度加快,结晶度增大。     

尼龙11/EVOH共混物的流变性能研究

使用XLY-Ⅱ型毛细管流变仪研究了尼龙11/EVOH共混物的流变特性.实验结果表明:尼龙11/EVOH共混物为假塑性流体,在195～225℃的非牛顿指数为0.46～0.63,其表观粘度随着EVOH含量的增加先减小后增加,当EVOH含量为10%时,表观粘度最小.EVOH的加人使体系的粘流活化能增大,故熔体的流变性受温度的影响较大.     

Controlling interfacial instabilities in PP/EVOH coextruded multilayer films through the surface density of interfacial copolymers

Coextruded polypropylene/tie/ethylene vinyl alcohol/tie/polypropylene (PP/tie/EVOH/tie/PP) films often exhibit optical defects which appear as randomly distributed scattering objects, in the submillimeter range. These defects may strongly affect the film transparency and prevent their practical use in packaging. Based on an objective optical test aimed at quantifying the film transparency, and on a systematic analysis, through optical microscopy, of transverse cuts of films obtained in various coextrusion conditions, the nature of the defects could be identified as resulting from a modulation of the thickness of the inner ethylene vinyl alcohol (EVOH) layer, with no variation in the overall thickness of the multilayer films. Thanks to a recently developed method to dose the surface density of interfacial copolymers, a clear correlation between the amplitude of the thickness modulation of the inner EVOH layer and the density of copolymer molecules formed in situ at the EVOH/tie layer interface during the coextrusion process was established. These results open the way to a better design of tie layers composition to avoid these kinds of defects.     

水辅助注塑PP/EVOH共混物制品的相形态与阻渗性能

选择3种不同黏度的聚丙烯(PP)与聚乙烯醇(EVOH)共混制备质量比为90/10的共混物,并采用水辅助注塑(WAIM)将这3种共混物成型为中空制品。从WAIM制品靠近浇口(1^#)和末端(2^#)两个位置取出样品,通过扫描电镜观察样品壁厚上3个位置的相形态,并测试所取样品的甲苯渗透率。借助WAIM中高压水作用下模腔内熔体的流场对样品中3个位置的相形态进行了分析。对WAIM的高黏度比共混物制品2^#样品,在外表层和内表层分散相呈粗纤维状,芯层主要呈液滴状,其阻渗性能与相应的WAIM PP样品比有适度提高(约2.4倍);对WAIM的2种低黏度比共混物制品2^#样品,外表层和内表层分散相呈细纤维状,芯层呈粗长纤维状,其阻渗性能与相应的WAIM PP样品比提高幅度较大(其中对黏度比最小的共混物达9.8倍)。1^#位置所取3种WAIM PP/EVOH样品中分散相纤维的平均直径比2^#位置的大,导致1^#位置所取样品的阻渗性能比2^#位置的低。     

Gas barrier changes and morphological alterations induced by retorting in ethylene vinyl alcohol–based food packaging structures

Ethylene vinyl alcohol (EVOH)–based packaging structures were analyzed in terms of both barrier properties and morphological alterations after a retorting process and as functions of ethylene content. From the results, it was found that the samples do have a substantial decrease in oxygen barrier properties and that the kinetics of recovery strongly depends on the copolymer ethylene fraction. A morphological deterioration was also observed as a result of retorting, particularly for packaging structures composed of EVOH copolymers of low ethylene contents. However, the polymer morphology and barrier properties were restored after a dry thermal treatment of the retorted samples. Interestingly, preannealing of copolymers of low ethylene content rendered them more resistant to the retorting process by means of promoting both a more robust crystallinity and a lower water sorption capacity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2192–2202, 2005     

Active Packaging Films from Ethylene Vinyl Alcohol Copolymer and Clove Essential Oil as Shelf Life Extenders for Grass Carp Slice

Active packaging provides a way to prevent the food putrefaction effectively . Various studies provide information on the actual preservation effect of active packaging or the migration of active agents from active films into various food stimulants separately. However, there is little related data available regarding the combined analysis of release and preservation effect. In this work, we examined the properties of active food packaging films successfully produced by extrusion of ethylene vinyl alcohol copolymer (EVOH) films with clove essential oil (C). The characterization of mechanical, thermal and barrier properties of the packaging polymers film showed that the addition of clove essential oil did not decrease their properties and C as plasticizer improved process fluidity of EVOH resin. The release of C from film to various food stimulants was measured by using HPLC, and Fickian diffusion models were used to fit the data with appropriate equation. The effects of E/C (ethylene vinyl alcohol copolymer/clove essential oil) films on quality assessment of Grass Carp slice based on sensory analysis and biochemical indices during refrigerated storage (4 ± 1°C) were examined over the period of 10 days. Total volatile basic nitrogen (TVB‐N), total viable counts, pH, TBA, water holding capacity (WHC) and texture properties were evaluated. The results indicated that the active film containing 3% clove essential oil had different release parameters in four food stimulants and it could effectively maintain the fish freshness and extend the shelf life to 7–8 days during cold storage compared with control group, which was only 4 days. Copyright © 2016 John Wiley & Sons, Ltd.