Effects of High Pressure Treatments on Polymeric Films for Flexible Food Packaging

Effects of high pressure (HP) treatments on functional and morphological properties of commercial packaging films have been investigated, to assess their suitability for use in these processes. Experimental analyses have been performed on packaging films, used to make pouches containing four different types of food simulants, after HP pasteurization and sterilization treatments at 200, 500 and 700 MPa. The investigated polymeric flexible packaging structures were single layer as well as bilayer films. Effects of treatments on structural/morphological properties (i.e. crystallinity and density) and on thermodynamic and barrier properties were addressed. Quite all the investigated films were found to be suitable for HP pasteurization, which only determined a negligible effect on the glass transition temperatures and on density of the amorphous regions of some polymeric materials, without a significant effect on functional properties of the packaging. Only bilayer structures including metalized polyethyleneterephthalate were not able to withstand processing conditions because of an extensive delamination accompanied by loss of metallization layer. Conversely, in the case of HP sterilization, combined effects of HP and relatively high temperature caused significant modifications in some of the packaging materials, even those not including a metalized film. In particular, localized delamination occurred in the case of bilayer structures made by laminating polyethyleneterephtalate with linear low density polyethylene or with polypropylene. Films obtained by laminating cast polyamide and bioriented polyamide with polypropylene displayed no evidence of delamination. In the case of films not displaying delamination, only limited changes in gas and vapour barrier properties were detected. Copyright © 2014 John Wiley & Sons, Ltd.     

超高压保鲜包装技术的研究进展

目的研究超高压保鲜包装技术的保鲜机理、现状和未来的发展方向。方法超高压技术(UHPP)是一种新型的非热加工技术,它主要通过破坏微生物的细胞壁、细胞膜及细胞间隙的结构,使蛋白质等成分发生变性,使酶活性降低来达到杀菌的目的。从超高压技术在水产品工业、肉制品工业及果蔬、其制品工业等方面,阐述了超高压杀菌技术的应用现状及进展。结论超高压保鲜包装技术还处于起步阶段,目前的研究主要集中在技术工艺方面,对于保鲜机理的研究相对较少。随着对超高压保鲜包装技术研究的不断深入,关于其相关机理的研究会越来越深入。     

The Effect of High Pressure Processing on the Integrity of Polymeric Packaging – Analysis and Categorization of Occurring Defects

As high‐pressure processing is used increasingly for the treatment of packed products, different packaging has been investigated with respect to their structural behaviour and stability under high‐pressure processing. Often, failures and changes of the polymeric structure occur. Common damage symptoms of high‐pressure‐treated packaging materials are defined and classified in this review. These damage symptoms are allocated to the physico‐chemical effects that created them. The effects may be separated into direct effects induced by the action of the high‐pressure alone and indirect effects that are mediated via compressed contents of the package, i.e. filled product and gaseous headspace. The direct effects split up again in reversible and irreversible structural changes. The indirect effects are generated by compressed headspace gases, other compressed substances and the consequences of increased amounts of gases dissolved in the polymers. If applicable, current theoretical approaches have been allocated to the different categories of damage. Copyright © 2013 John Wiley & Sons, Ltd.     

超高压杀菌处理对包装材料稳定性的影响

在超高压条件下对PET/AL/PE和PET/VMPET 2种塑料薄膜进行处理,测定不同压强及保压时间对材料拉伸强度、断裂伸长率、热封性能及阻隔性能的影响。结果表明:超高压对2种材料拉伸强度及断裂伸长率均未表现出显著影响,但对PET/VMPET/PE材料的热封强度影响显著;在500 MPa压强下保压时间对2种材料的透湿性能影响显著。     

超高压处理对食品包装材料的影响研究进展

超高压杀菌处理对食品品质的影响较小,能较好地保持食品原来的营养和风味。阐述了超高压处理的杀菌机理及影响因素,综述了超高压处理对食品包装材料的机械性能、阻隔性能、物质迁移的影响研究状况,展望了超高压处理对食品包装材料影响研究的发展方向。     

包装和高压电场对去皮山药保藏的影响

采用不同包装材料,并用高压电场对去皮山药进行处理,将处理好的去皮山药于4～10℃保藏,测定其细菌菌落数,观察感观变化,研究不同包装和高压电场条件对去皮山药的保藏效果.结果表明:用护色液处理,50℃煮15min后,经真空PET/PE复合包装和高压电场64kV处理12min,低温4～10℃保藏去皮山药为最佳.     

基片温度对TiO2薄膜表面形貌和性能的影响

利用射频磁控溅射设备在玻璃基片上制备TiO2薄膜,采用AFM、UV-Vis分光光度、接触角测定仪等测试手段,研究基片温度对薄膜表面形貌、粗糙度和表面性能的影响.结果表明,随着基片温度增加,薄膜表面粗糙度增大,薄膜中颗粒由无定形态逐渐向定向排列的晶态转变,而薄膜结构、表面形貌和粗糙度的变化明显影响薄膜表面性能.最后,探讨了薄膜的生长机理.     

Hydrophobic Zeolite‐Filled Polymeric Films with High Ethylene Permselectivity for Fresh Produce Packaging Applications

Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of ‘mixed matrix membrane’, by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM‐5, and the surface‐modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene‐b‐(ethylene‐ran‐butylene)‐b‐styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78–2.67 × 10³ cm³ ? mm/m² ? day ? atm and ethylene/O₂ selectivity of 4.67–8.26, was obtained from the films containing octyl‐modified and phenyl‐modified zeolites. Particular enhancement was observed on the films containing phenyl‐modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface‐modified zeolites were superior. Particle–polymer interface could thus be improved. Copyright © 2014 John Wiley & Sons, Ltd.     

Diffusion of Aroma Compounds into Packaging Films under High Pressure

Diffusion of the aroma compounds p-cymene and acetophenone into three different packaging films was studied at 500 MPa for kinetic measurement, and in the range of 0.1–450 MPa for measurement of the diffusion rate as a function of pressure. Absorption of aroma compounds was lower in pressurized than in nonpressurized polymeric films. PET/A1/LDPE was impermeable to either substance; absorption was limited to the LDPE lining inside. Distribution of aroma compounds to solution and films depended on their polarity; acetophenone virtually did not diffuse into the films. Measurements of the diffusion rate as a function of pressure has shown a diffusion barrier in the range of 100–200 MPa for the films investigated. The assumption that this is due to transition into the glassy state has been supported by studies of diffusion as a function of temperature.     

Effect of High Pressure Processing on the Thermal and Mechanical Properties of Polyethylene Films Measured by Dynamical Mechanical and Tensile Analyses

This study investigated the influence of high pressure processing on the thermal and mechanical properties of low‐density polyethylene (LDPE) films used for food packaging. This was carried out by monitoring the thermal and mechanical properties of the materials before and after the pressure treatments. Pouches made from the LDPE films were pressured at 200, 400 and 800 MPa for 5 and 10 min at 25 and 75°C. The storage and loss moduli, tensile strength and elongation at break and yield of the film samples were then measured using dynamic mechanical analysis (DMA) and an Instron® Universal Tester (Canton, MA, USA), respectively. The DMA was performed at ?130 to 85°C, whereas the tensile and elongation analyses were carried out at room temperature. Results of the DMA experiments showed that the storage modulus increased with increasing pressure intensity. The tensile analysis showed that the tensile strength increased but the elongation decreased with increasing pressure treatment. Copyright © 2013 John Wiley & Sons, Ltd.     

高温高压下立方氮化硼晶体的生长机制

在４．５－５．０ＧＰａ，１５００－１８００℃范围内，对在Ｌｉ基复合氮化物或氮硼化物和催化体系中以及其中添加Ｌｉ８ＳｉＮ４后合成ｃＢＮ进行了研究。探讨了ｃＢＮ晶体的表面构造和生长机制，研究了由六方氮化硼向立方氮化硼转变过程中硅的存在在行为。本实验中合成的立方氮化硼为具有光泽的棕色透明单晶。     

从包装起源看包装设计对现代产品的作用和影响

通过包装的缘起提出包装设计发展的必然性以及产品发展所带来的包装设计的弊端;通过论证、例证、图片分析,提出如何解决包装设计适应社会需求,易于消费者产生识别,满足消费者的诉求及归属,从而强化包装设计对产品重要性的认识.     

重力对聚合物形成的影响

在聚合物合成过程呼聚合物凝固过程中,聚合物分子量和聚合物颗粒尺寸的大小,分布和聚合物聚集态结构强烈依赖于重力,本文分增力,减重力和微重力三部分阐述了近年来重力对聚合物形成影响研究概况,重点介绍了微重力下聚合物一些研究成果,并指出了今后的发展方向。     

高压热处理对AlN陶瓷显微结构及导热性能的影响

热处理是AlN陶瓷调整结构、改善性能的有效手段.利用国产六面顶压机,在5.0GPa高压条件下,对高压烧结制备的AlN(Y2O3)陶瓷进行了热处理,研究了高压热处理对AlN陶瓷显微结构及导热性能的影响.结果表明:经5.0GPa/970℃/2h高压热处理后的AlN陶瓷材料与未热处理的试样相比,晶粒尺寸显著增大,晶粒形状越发规整,第二相均位于晶界处或者三角晶界区域,热导率达到了173.2W/(m.K),是未经过热处理试样的2.2倍.但是,将高压热处理时间延长到4h,AlN陶瓷的气孔增大,出现了反致密化现象,热导率也降低到80.9W/(m.K).     

功能高分子材料在军用包装中的应用

阐述了功能高分子材料对武器装备防护包装的重要作用,简要介绍了功能高分子材料的主要种类及其特点,列举了在军用包装中应用较为普遍的几种功能高分子材料,分析了功能高分子材料在军用包装领域应用的发展趋势。     

素坯高压成型对纳米4YSZ烧结的影响

在纳米 4YSZ粉中加入少量纳米Al2 O3 粉 ,素坯两次 40 0MPa加压成型后在 4GPa高压下再成型 ,素坯相对密度达 72 4 %,降低了烧结致密温度。超密实坯体在 110 0℃常压下烧结 2小时 ,陶瓷体致密度达 99 2 %。烧结样品的晶胞四方度atc- 1t 为 1 0 12 ,晶胞体积V为 0 132nm3 。 110 0℃常压煅烧 ,烧结体晶粒大小在 40～ 70nm。烧结体研磨成粉后含有 12～ 14%的单斜相。     

高阻隔HDPE包装对NFC橙汁品质和货架期的影响

目的 研究高阻隔HDPE包装对NFC橙汁品质和货架期的影响,为果汁生产加工企业提供信息和参考.方法 采用巴氏杀菌法对NFC橙汁进行灭菌处理,研究在4,25,37℃时PET包装、普通HDPE包装、高阻隔HDPE包装的NFC橙汁各项指标的变化情况,通过对抗坏血酸和整体接受度的结果分析,建立NFC橙汁的动力学模型,利用阿伦尼乌斯方程对其货架期进行预测.结果 高阻隔HDPE包装相较于其他2种包装的NFC橙汁褐变小、抗坏血酸和胡萝卜素损失少、喜好度高.以抗坏血酸含量损失50％为标准,温度为4,25,37℃时的货架期分别为152,55,31 d;以整体接受度5分为标准,温度为4,25,37℃时的货架期分别为183,44,21 d.结论 高阻隔HDPE包装可以有效地延长NFC橙汁的保质期,并保证其在保质期内的品质,在NFC果汁中有很好的应用前景.     

Thin Laminate Films for Barrier Packaging Application – Influence of Down Gauging and Substrate Surface Properties on the Permeation Properties

A reduction in thickness of barrier laminated film systems generally leads to a quality decrease of the resulting packaging materials' functional properties. Especially for food packaging applications, adequate oxygen and water barrier properties are indispensable. The focus of this study was therefore the development of thin film systems using metallized aluminium or ethyl vinyl alcohol barrier laminates with low oxygen and water vapour transmission properties. Biaxially oriented polyethylene terephthalate and biaxially oriented polypropylene aluminium‐coated thin film laminates as well as corresponding ethyl vinyl alcohol film systems could be successfully produced with oxygen transmission rates of <0.5 cm³(STP)/(m² d bar) and water barrier values of <0.1 g/(m² d). It could be confirmed that the film thickness of these materials within the range of the investigated dimensions does not have an influence on the barrier properties. In fact, the parameters of the production process influence the functional properties of the film systems and must therefore be adapted. Machinability of these excellent thin film systems requires further investigation on packaging lines before they can be transferred to packaging application. Copyright © 2011 John Wiley & Sons, Ltd.     

高导热环氧/有机硅杂化封装胶的制备与性能

以γ-缩水甘油醚氧丙基三甲氧基硅烷为原料,通过水解缩聚制备出有机硅树脂,采用不同尺寸的改性氧化铝填充环氧/有机硅树脂基体以改善其耐热性能,并考察其力学性能、导热性能。结果表明,合成的有机硅树脂能提高封装胶的热分解温度,其热分解温度比环氧树脂高35.66℃。所制备封装胶的导热系数为1.01 W/(m.K),相比单一环氧树脂其导热性能提高了约5倍,其粘接强度为10.27 MPa,该导热封装胶表现出良好的的综合性能,可用于微电子器件封装领域。     

矩形管双焦点不对称翻领成型器曲面研究

研究了矩形管双焦点不对称翻领成型器领口交接曲线和曲面的形成,建立了矩形管双焦点不对称翻领成型器的肩曲面及其边界曲线的数学模型,给出了其高度与其它参数的关系式,为矩形管双焦点不对称翻领成型器的CAD/CAM提供了数学理论依据.