![]() This can present downstream issues, particularly now that sustainability has become a pressing issue and the integration of RPET anywhere from 10 - 100% has become a must.Īdditional factors that affect the IV are drying and processing parameters. RPET changes the IV of the material, as the metallic catalysts used in the initial polymerization loses its strength and cannot be revived, thus resulting in a loss of IV. PET inherently presents challenges in processing, and this can be further exacerbated with the integration of recycled PET, or RPET. The same follows at the thermoforming process stage with high deviation in the process and scrap rate. If a low or unknown IV grade PET is processed it will produce undesired effects, including extrusion pressure and melt viscosity variation which can result in sheet thickness variation or brittleness. There are great advantages in testing and controlling IV for its processability and overall quality of the product. The desired IV of PET is dependent on its application and classified in different grades as referenced in the table.Īdvantages of testing and controlling IV as it pertains to processing & quality: Therefore, the longer the polymer chains are, the more entanglements between the polymeric chains occur, and the higher the viscosity value resulting in a stiffer material. The IV is dependent upon the length of the polymer chains. IV, is thus a key quality control specification and perhaps the most important characteristic of PET. You have probably heard of the term IV when discussing PET materials, but why is this specification so important? As previously mentioned, the polymer chain reaction, or polymerization, is stopped at a point when polymer chain length reaches a certain level for its end-use application based on its IV test reading.Ī measure of the polymers molecular weight, IV reflects the material’s melting point, crystallinity, and tensile strength. This is measured using an intrinsic viscosity, or IV, testing technique. The reaction is stopped at the desired polymer chain length which is related to its end use application. As the viscosity increases during the polymerization stage, so does the polymer chain and chain length. Polymerization occurs through a polycondensation reaction of the monomers with water as the by-product. Perhaps the most critical specification when it comes to PET, control, or lack thereof, of PETs intrinsic viscosity at the extrusion stage can make or break packaging performance, resulting in issues ranging from downstream quality problems to added cost.Ĭontinue reading to learn more about the importance of intrinsic viscosity and ICPG’s quality control capabilities:īefore we get into the nitty-gritty on the importance of intrinsic viscosity - first, a quick refresher on how PET is made:Ī widely used material among various industry segments, most of us can probably picture what rigid PET packaging looks like in its end-use application, but how is it made? PET is produced by copolymerizing monomers including Ethylene Glycol and Terephthalic Acid under heat and pressure with the help of metallic catalysts. Outside of these key attributes, there is one specification in particular with the ability to drastically affect the functionality and processability of this material in both extrusion and thermoforming, and that is the Intrinsic Viscosity. ![]() PET presents many advantages including aesthetics, barrier properties, durability, recyclability and sustainability, thus making it the material of choice for wide range of packaging applications across various market segments.
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