Test inertness of packaging materials.A popular packaging material, PET--polyethylene terephthalate--is a polyester plastic resin. It is a polymer formed by combining two monomers: modified ethylene glycol ethylene glycol: see glycol. ethylene glycol Simplest member of the glycol family, also called 1,2-ethanediol (HOCH2CH2OH). It is a colourless, oily liquid with a mild odour and sweet taste. and purified terephthalic acid Terephthalic acid is one isomer of the three phthalic acids. It finds important use as a commodity chemical, principally as a starting compound for the manufacture of polyester (specifically PET), used in clothing and to make plastic bottles. . It's used by manufacturers because of its strength, thermostability Thermostability is the quality of a substance to resist irreversible change in its chemical or physical structure at high temperature. (Naturally, the meaning of high temperature will depend upon the type of material. and transparency. Customers choose PET because it is inexpensive, lightweight, resalable, shatter-resistant and recyclable. PET bottles used to hold soft drinks are often refillable. But the material must be regularly tested for its inertness to see if it absorbs and transmits flavors. Because no testing methods are adequate or standardized standardized pertaining to data that have been submitted to standardization procedures. standardized morbidity rate see morbidity rate. standardized mortality rate see mortality rate. , researchers in Finland, Germany, Sweden and the Netherlands decided to develop a sensory technique for testing the material's inertness. In this approach, there is an initial loading step. During this process, the packaging material is kept in contact with a cocktail of flavor-active substances. Then the material is placed in contact with water. Flavor-active substances then migrate into the water. Depending on the inertness of the bottle material, the odor intensity of the water will increase or decrease. Scientists developed a process evaluating the odor intensity. The odor intensities from unknown samples were compared with that from a reference sample. The results from the different laboratories testing the technique were quite similar. The repeatability in the evaluations was high in all laboratories, but the standard deviation In statistics, the average amount a number varies from the average number in a series of numbers. (statistics) standard deviation - (SD) A measure of the range of values in a set of numbers. between the non-trained sensory panel members was high. The scientists are currently finalizing a certification report on the chemical inertness test. They expect it to be available next year. The technique also can be applied to polycarbonate A category of plastic materials used to make a myriad of products, including CDs and CD-ROMs. materials. Further information. Roland Franz, Fraunhofer Institut fur Verfahrenstechnik und Verpackung, Giggenhauserstrasse 35, 85354 Freising, Germanny; phone: +49 8161491746; fax: +49 8161491777; email: franz@ivv.fhg.de; URL URL in full Uniform Resource Locator Address of a resource on the Internet. The resource can be any type of file stored on a server, such as a Web page, a text file, a graphics file, or an application program. : www.ivv.fhg.de. |
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