Microwave synthesis of new star shaped polyester polyols based on L-lactide

The molecular architecture of biodegradable polymers can be adjusted by incorporating multifunctional polyols into the polyester backbone to obtain branched polymers. The aim of our work was to prepare biodegradable polyester polyols based on L-lactide and castor oil in presence of tin(II) 2-ethylhexanoate as catalyst in microwave field. The polyester polyol was synthesized by core-first method which involves a polymerization of L-lactide from OH groups on castor oil. FTIR and 1 H NMR spectroscopy measurements were used to confirm the molecular structure of the synthesized products. DSC measurements were used to evaluate the crystallinity of obtained polyols. Thermal stability was investigated by thermogravimetric analysis, and results have shown the dependence of thermal stability on the arm length of the star shaped polyesters.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Barrier Properties of Coated and Laminated Polyolefin Films for Food Packaging

The food packaging industry demands polymer films possessing a defined barrier against permeation of gases, moisture and flavor. The objective of this study was to assess the differences between the barrier properties of coated and un-coated polyolefine films. Eight types of packaging films are prepared by standard industrial procedure by cast film extrusion processing with chill rollers: biaxially oriented polypropylene (BOPP), BOPP coated by acrylic copolymer, metallized BOPP by aluminum, and low-density polyethylene (LDPE). The influence of lamination and metallization on the gas molecules ($CO_{2}$, $O_{2}$ and $N_{2}$) was determined by Lyssy's method. The moisture transparency was assessed according to the gravimetric method. The substantial differences between the barrier properties of the coated and un-coated films were estimated. It was estimated that the lamination process improves the oxygen barrier but not necessarily the moisture barrier, due to the different mechanisms for oxygen and moisture permeability. The obtained barrier properties data were considered from a practical point of view. It was concluded that films based on metallized BOPP has excellent barrier properties and can be used to over wrap food products

The changes of etheric oil content in powdered garlic during storage in different packaging materials

The etheric oil components in garlic are proven to have numerous positive effects on human health, and powdered garlic has long been widely used in both the food industry and private households. In order to prolong the stability of etheric oil components, different combinations of packaging materials are used for the storage of powdered garlic. Since the quality of dehydrated powder depends on the packaging used, the investigation was aimed to determine the effects of packaging material types on etheric oil content in industrially powdered garlic over the storage period. Powdered samples were analysed immediately after production and during long periods of storage (after 30, 90, 120, 180 and 270 days). The investigations were focused on the correlation between packaging materials performances (light, water vapour and air permeability), and the changes of etheric oil and moisture content in powdered garlic. In order to describe the changes in etheric oil content during time, as well as to predict changes in packed powdered garlic, a statistical procedure was applied for all examined packaging materials and curve fitting data were estimated (the least square approach)

The influence of nano silica particles on gamma-irradiation ageing of elastomers based on chlorosulphonated polyethylene and acrylonitrile butadiene rubber

The goal of this work was to study gamma irradiation ageing of rubber blends based on acrylonitrile butadiene rubber (NBR) and chlorosulphonated polyethylene rubber (CSM) reinforced by silica nano particles. The NBR/CSM compounds (50: 50, w/w) filled with different content of filler (0-100 phr) were crosslinked by sulfur. The vulcanization characteristics were assessed using the rheometer with an oscillating disk. The vulcanizates were prepared in a hydraulic press. The obtained materials were exposed to the different irradiation doses (100, 200, 300 and 400 kGy). The mechanical properties (hardness, modulus at 100% elongation, tensile strength and elongation at break) and swelling numbers were assessed before and after gamma irradiation ageing

Le Grand écho du Nord de la France

27 novembre 19041904/11/27 (A86,N332).Appartient à l’ensemble documentaire : NordPdeC