Food packaging based on polymer nanomaterials

Since its starting in the 19th century, modern food packaging has made great advances as results of global trends and consumer preferences. These advances are oriented to obtain improved food quality and safety. Moreover, with the move toward globalization, food packaging requires also longer shelf life, along with the monitoring of safety and quality based upon international standards. Nanotechnology can address all these requirements and extend and implement the principal packaging functions - containment, protection and preservation, marketing and communications. Applications of polymer nanotechnology in fact can provide new food packaging materials with improved mechanical, barrier and antimicrobial properties, together with nano-sensors for tracing and monitoring the condition of food during transport and storage.The latest innovations in food packaging, using improved, active and smart nanotechnology will be analyzed. It will be also discuss the limits to the development of the new polymer nanomaterials that have the potential to completely transform the food packaging industry.     

水体富营养化及其防治对策研究

水体的富营养化是当今社会面临的重大环境问题之一,已成为经济社会发展的重要影响因素,经济而有效的控制水体富营养化已经成为当代亟待解决的环境问题。本文回顾了水体富营养化问题的产生,从对人类健康、经济发展、生态保护等方面探讨了水体富营养化的环境危害,从控制水体的外源负荷和内源负荷等角度来提出了控制水体富营养化的对策。     

Influence of nanoclay on urea–glyoxalated lignin–formaldehyde resins for wood adhesive

In this research, the influence of nanoclay on urea–glyoxalated lignin–formaldehyde (GLUF) resin properties has been investigated. To prepare the GLUF resin, glyoxalated soda baggase lignin (15 wt%) was added as an alternative for the second urea during the UF resin synthesis. The prepared GLUF resin was mixed with the 0.5%, 1%, and 1.5% nanoclay by mechanically stirring for 5 min at room temperature. The physicochemical properties of the prepared resins were measured according to standard methods. Then the resins were used in particleboard production and the physical and mechanical properties of the manufactured panels were determined. Finally, from the results obtained, the best prepared resin was selected and its properties were analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectrometry (FTIR), and X-ray diffractometry (XRD). Generally the results indicated that the addition of sodium-montmorillonite (NaMMT) up to 1.5% appears to improve the performance of GLUF resins in particleboards. The results also showed that nanoclays improved mechanical strength (modulus of elasticity (MOE), Modulus of Rupture (MOR), and internal bond (IB) strength) of the panels bonded with GLUF resins. The panels containing GLUF resin and nanoclay yielded lower formaldehyde emission as well as water absorption content than those made from the neat GLUF resins. XRD characterization indicated that NaMMT only intercalated when mixed with GLUF resin. Based on DSC results, the addition of NaMMT could accelerate the curing of GLUF resins. The enthalpy of the cure reaction (ΔH) of GLUF resin containing NaMMT was increased compared with neat GLUF resin. Also the results of FTIR analysis indicated that addition of NaMMT change the GLUF resins structures.     

Overview of disbonding technologies for adhesive bonded joints

ABSTRACT

The ability to separate adhesive bonded assemblies without causing damage to the substrates is clearly very desirable. There are many applications such as in electronics, medical surgery, dentistry, building and general manufacturing where the opportunity to separate assemblies is important. This may be for repositioning in manufacturing, repair in service or recovery of materials at end of life. Various methods for adhesive reversibility or disbonding have been proposed over the last 40 years but there currently exist no universally accepted solutions for disbond-on-demand bonded applications. This paper considers the motivation for disbonding, the requirements and considerations associated with possible methods, and the overall effectiveness of the various mechanisms in the context of non-structural, semi-structural and structural joints. The range of technologies and mechanisms is reviewed, together with the associated methods for activation. The variety of methods is evaluated for their effectiveness in the context of different applications. Particular attention is given to the adverse effects on the performance of bonded assemblies in service, and the ways of mitigating these effects. It is shown that a total materials system approach must be adopted when seeking a disbonding technology for a particular set of circumstances.     

Effect of annealing on the properties of waterborne polyurethane adhesive containing urethane-based thickener

Different amounts of hydrophobically modified ethoxylated urethane-based thickener (HEUR) were added to improve the rheology of waterborne polyurethane adhesives. The thickened solid adhesive films were thermally annealed and characterised by IR spectroscopy, plate–plate rheology, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Hydrogen bonds played a key role in the thickening mechanism of polyurethane dispersions containing urethane-based thickener, along with ionic adsorption and micelles formation between hydrophobic groups. The adhesion properties were measured from T-peel test of leather/polyurethane adhesive/vulcanised styrene-butadiene rubber joints. Optimal results were obtained when water in the waterborne polyurethane adhesive (just before joint formation) was removed under open air, while forced air drying impeded the complete removal of water. On the other hand, the thermal annealing did not greatly affect the rheological and thermal properties of the thickened polyurethanes.     

中国机器人的发展战略思考

现阶段机器人的智能和自主能力仍很薄弱,作业能力的提升、人机交互能力的改善和安全性能的提高是发展的首要目标,需要解决制约人-机交互、人-机合作、人-机融合发展的瓶颈问题,突破三维环境感知、规划和导航、类人的灵巧操作、直观的人-机交互、安全机器人行为等单元技术,建议我国采取发展战略:1加强工业机器人整机设计理论与方法研究,寻求新思维,突破精密减速机、控制器、伺服系统以及高性能驱动器等核心基础部件瓶颈,提升机器人操作灵活性、在线感知能力;2加强服务机器人研究,提升机器人理解人的行为和抽象指令、人机沟通与协调合作能力,建立机器人安全机制;3针对在核辐射、军事战场、自然和人为灾害等危险甚至不可达区域执行任务的需要,开展特种机器人研究,解决在线实时交互、动态未知环境中自主作业等问题,实现机器人与人共处同一环境空间互助作业,为开发国家亟需的现代机器人提供科学理论和关键技术支撑。     

长江采砂执法若干法律问题思考

作为当前水行政执法的热点工作,长江采砂执法中面临着较多难题.从行政执法和刑事责任等方面对其中的一些法律问题进行了探讨,对常见的一般偷采江砂的行为,认为<刑法>中最接近的罪名是非法采矿罪.非法开采长江江砂同一般的非法采矿又有不同,它不仅造成国有资源损失,还影响河势稳定,威胁防洪和水上交通安全,社会危害性更大;另外,其主管机关是水行政部门,而非地矿部门.同时,直接适用该罪名还有障碍,如刑法条文中"对矿产资源造成破坏"难以解释.建议最高人民法院对非法采砂专门出台司法解释,并明确当事人因偷采次数、数量和造成其他后果而承担刑事责任的具体界限.     

二氧化碳捕获与封存技术

二氧化碳捕获与封存技术是未来实现低碳经济转型的重要环节.二氧化碳捕获与封存工作分为三个阶段:①捕获阶段;②运输阶段;③封存阶段.CCS产业链即在上述三阶段基础上增加油气采收率一节.包括中国在内的许多国家也进行了与二氧化碳收集、捕获项目密切相关的实践.但仍有主要法律问题制约二氧化碳捕获与封存工作发展.使CCS工作真正达到...     

水利与国民经济协调发展研究

水利对国民经济的支撑作用,社会各界已经达成了广泛共识,但这种认识基本上是从定性的角度进行分析的．缺少定量的佐证。水利部“十五”重大科技项目“水利与国民经济协调发展研究”,揭示了水利与国民经济之间存在各种定量关系。     

农村水电可持续发展及管理对策

农村水电具有一定的开发优势，但在开发中存在着水能资源管理缺位、部门职责不清、缺乏统一规划和统一调度管理等问题。针对这些问题,从编制流域综合规划、建立和完善水能资源许可制度、加强政府监管力度、实行统一调度、协调水电开发与生态保护的关系等方面提出了管理对策。