Review: Nanocomposites in Food Packaging

ABSTRACT:  The development of nanocomposites is a new strategy to improve physical properties of polymers, including mechanical strength, thermal stability, and gas barrier properties. The most promising nanoscale size fillers are montmorillonite and kaolinite clays. Graphite nanoplates are currently under study. In food packaging, a major emphasis is on the development of high barrier properties against the migration of oxygen, carbon dioxide, flavor compounds, and water vapor. Decreasing water vapor permeability is a critical issue in the development of biopolymers as sustainable packaging materials. The nanoscale plate morphology of clays and other fillers promotes the development of gas barrier properties. Several examples are cited. Challenges remain in increasing the compatibility between clays and polymers and reaching complete dispersion of nanoplates. Nanocomposites may advance the utilization of biopolymers in food packaging.     

Effects of surface treatment on the mechanical properties of carbon fibers

Surface of the carbon fibers developed from PAN (polyacrylonitrile) has been modified using such methods as air oxidation, nitric acid treatment, and anodic (electrolytic) oxidation. By choosing optimum treatment parameters, the tensile strength of such fibers has been found to increase by about 60 percent over that of the untreated value. A quantitative estimation of the surface groups formed during the treatment shows an increase in number with severity of the treatment. Further, removal of these functional groups from the fiber surface during degassing at 1000°C also influences the mechanical properties of the carbon fibers considerably. Results have been discussed in detail.     

Experimental investigation on effects of dielectric mediums in near-dry electric discharge machining

Journal of Mechanical Science and Technology - A dielectric fluid plays a significant role on the machining efficiency of Electric discharge machining (EDM). Two phase (liquid-air) dielectric...     

Impacts of CO2 emission constraints on technology selection and energy resources for power generation in Bangladesh

This paper examines the impacts of CO₂ emission reduction target and carbon tax on future technologies selection and energy use in Bangladesh power sector during 2005–2035. The analyses are based on a long-term energy system model of Bangladesh using the MARKAL framework. The analysis shows that Bangladesh will not be able to meet the future energy demand without importing energy. However, alternative policies on CO₂ emission constraints reduce the burden of imported fuel, improve energy security and reduce environmental impacts. The results show that the introduction of the CO₂ emission reduction targets and carbon taxes directly affect the shift of technologies from high carbon content fossil-based to low carbon content fossil-based and clean renewable energy-based technologies compared to the base scenario. With the cumulative CO₂ emission reduction target of 10–20% and carbon tax of 2500 Taka/ton, the cumulative net energy imports during 2005–2035 would be reduced in the range of 39–65% and 37%, respectively, compared to the base scenario emission level. The total primary energy requirement would be reduced in the range of 4.5–22.3% in the CO₂ emission reduction targets and carbon tax 2500 Taka/ton scenarios and the primary energy supply system would be diversified compared to the base scenario.     

海尔兹山纪念堂

正海尔兹山纪念堂是一个独特的纪念场所。为了纪念耶路撒冷所有阵亡的士兵,设计中包含了他们名字。这是和平年代期冀希望的象征。尽管临近耶路撒冷繁华路段,纪念堂设计为一个平静的圣经式场地,整个空间孤隐而静谧。建筑主体空间通过挖掘山体而成,形成个人或集体纪念活动的私密空间。纪念堂上方的山体,以耶路撒冷石塑造出新的曲线。纪念堂形成一个波形漏斗状结构,缓缓通向天际。这种不规则的涡旋状结构为纪念堂营造出不断变化的自然光。     

Performance Evaluation of Wireless Communication Systems over Weibull/q-Lognormal Shadowed Fading Using Tsallis’ Entropy Framework

Wireless Personal Communications - In wireless communication channels, the signals arriving at the receiver may be of stochastic nature or be superpositioned due to non-uniform scattering and...     

A selective reaction of polyhydroxy fullerene with cycloaliphatic epoxy resin in designing ether connected epoxy star utilizing fullerene as a molecular core

A novel ether connected epoxy star like polymer was synthesized by selective reaction of water soluble polyhydroxy fullerene (fullerenol) with a commercial grade cycloaliphatic epoxy resin (CY-230, Ciba Geigy) in heterogeneous medium at ambient alkaline condition using tetrabutylammonium hydroxide as phase transfer catalyst. The reaction went well in such conditions and the hydroxy groups of fullerenol underwent selective nucleophilic addition reaction with polar carbonyl groups of the epoxy resin with the formation of a hemiketal. The progress of the reaction was monitored by FTIR analysis of the product formed. The disappearance of characteristic FTIR bands of fullerenol (at 1593.2, 1381.2, and 1068 cm⁻¹) and the typical carbonyl peak (at 1725 cm⁻¹) of parent epoxy resin and also changes of broad hydroxy peak (at 3431 cm⁻¹) of fullerenol into a sharp peak (at 3396.6 cm⁻¹, indicating reduced hydrophilicity) in the reaction product clearly demonstrated the chemical attachment of the epoxy units to the fullerene core. Multiple epoxy units (about 8-10) were attached to fullerene core. Non-reactivity of fullerenol towards DGEBA epoxy resin (LY 556 Ciba Geigy) in similar conditions further supports our result. The thermal properties of the product were influenced by the presence of fullerenol and exhibits higher thermal stability compared to parent epoxy. A probable reaction mechanism for the reaction has also been discussed.     

Design and Comparative Analysis of Heterogeneous Gate Dielectric Nanosheet TFET with Temperature Variance

Silicon - In this article, a Heterogeneous Gate-Dielectric Nanosheet Tunnel Field Effect Transistor (HD-NSH-TFET) with three channels is investigated using the 3-D Visual TCAD simulator. The HD...     

Modelling of multicomponent gas separation with asymmetric hollow fibre membranes—methane enrichment from biogas

A mathematical model for the dynamic performance of gas separation with high flux, asymmetric hollow fibre membranes was developed considering the permeate pressure build‐up inside the fibre bore and cross flow pattern with respect to the membrane skin. The solution technique provides reliable examination of pressure and concentration profiles along the permeator length (both residue/permeate streams) with minimal effort. The proposed simulation model and scheme were validated with experimental data of gas separation from literature. The model and solution technique were applied to investigate dynamic performance of several membrane module configurations for methane recovery from biogas (landfill gas or digester gas), considering biogas as a mixture of CO₂, N₂ and CH₄. Recycle ratio plays a crucial role, and optimum recycle ratio vital for the retentate recycle to permeate and permeate recycle to feed operation was found. From the concept of two recycle operations, complexities involved in the design and operation of continuous membrane column were simplified. Membrane permselectivity required for a targeted separation to produce pipeline quality natural gas by methane‐selective or nitrogen‐selective membranes was calculated. © 2012 Canadian Society for Chemical Engineering