When major sporting events are being held, many fans constantly check their news feeds to see their country’s medal count. There’s nothing like a shiny gold medal that brings out a country’s pride. (Surprisingly a gold medal contains very little gold!).
Many sporting organizations are also utilizing recycled materials in their awards. The Brazilian Mint recently made use of recycled raw silver at 92.5 per cent purity, coming from leftover mirrors, waste solders and X-ray plates. And 40 per cent of the copper used in bronze medals comes from waste at the mint itself.
Metal isn’t the only recycled material in awards, however. The colorful ribbons on which the metal medallions hang are made from 50 percent recycled PET. Officials on one website claimed that half of the plastic in the ribbons which hang around athletes’ necks comes from recycled plastic bottles.
Polyethylene terephthalate (PET) is a strong, lightweight, transparent plastic. You’ve probably heard of PET as the material of drink bottles and take-out containers. It is the most recycled plastic in the world, at a rate of 31% in the United States and 52% in Europe. It can be commercially recycled by washing and re-melting, or by chemically breaking it down to its component materials to make new PET resin. (You can read more about the recycling of PET in this previously published article: Improving Processing of PET.)
PETRA, the PET Resin Association, website explains how PET is made:
The basic building blocks of PET are ethylene glycol and terephthalic acid, which are combined to form pellets of PET. These resin pellets are then heated to a molten liquid that can be easily extruded or molded into items of practically any shape.
More specifically, when the two raw materials of PET are combined under high temperatures and low vacuum pressure, long chains of the polymer are formed. As the mixture becomes thicker, the chains grow longer. Once the appropriate chain length is achieved, the reaction is stopped. The resulting spaghetti-like strands of PET are then extruded, quickly cooled, and cut into small pellets.
When the resin pellets are reheated to a molten liquid stage, the polymer chains can be stretched in one direction (for fibers) or in two directions (for bottles and films). If the polymer is cooled quickly while it is stretched, the chains are frozen with their orientation intact. Once set in stretched form, the material is extremely tough.
When PET is used to make fabric, it’s known as polyester, a popular material for sportswear because it is crease-resistant, tear-proof, weather-proof and hydrophobic — the perfect material to be worn on an athlete’s neck.
Needless to say, the final material has to be as perfect as an elite athlete’s performance. So the look and feel of the award, including the ribbon itself, has to be a product of excellence. To help ensure that quality, we can guess that several quality assurance and analysis techniques are used throughout the process.
Hydroxyl value and other related parameters are very important Quality Control (QC) measurements for manufacturers and users of polyols. Specifically, polyester producers must monitor the material’s acid value. Fourier transform near infrared (FT-NIR) spectroscopy has been proven to be advantageous for these measurements and for assurance of proper esterification reactions, and for the determination of the reaction end-point. (Read FT-NIR for Online Analysis in Polyol Production which describes the use of FT-NIR spectroscopy for the determination of the hydroxyl value and other critical polyol properties.)
X-ray photoelectron spectroscopy (XPS) is a technique for analyzing the surface chemistry of a material. XPS can measure the elemental composition, empirical formula, chemical state and electronic state of the elements within a material. We don’t know the manufacturer’s production requirements, but we can guess that a surface analysis system is used to investigate the surface treatment of the polyester fabric to help ensure surface modifications, such as a fabric protection coatings, have been applied, and also for finding the amount of coating present. It can also be used for quality control of invisible coatings on fabrics and other materials to determine whether they have been applied uniformly. (Click here to read more about how XPS Identifies Production Failures in Surface-treated Polyester Fabric.)
With a rheometer, the mechanical properties such as the viscosity and the dynamic moduli of polymer solutions, polymer melts as well as semi-solids can be measured as a function of stress, strain, time, frequency, temperature etc., not only in shear but also in extensional flow. In a previous article we discussed how a minilab micro compounder can be used to screen the effect of different additives. The whole exercise was done to do re-active extrusion in the mini compounder and use recycled PET with additives to give “recycled” PET the similar properties as fresh material. The problem with PET is that after it is recycled a number of times, the material properties change dramatically and molding (e.g., for a bottle) is no longer possible. Instead of dumping/burning the old PET, re-active extrusion could help to restore the conditions so that a further usage is possible. (Click here to read more and access a scientific poster on the Analysis of PET with Additives.)
Ribbons aren’t the only “fabrics” made from PET. Carpet and clothing, industrial strapping, rope, upholstery fabrics, boat sails, fiberfill for winter jackets and sleeping bags, and many other items are produced using recycled PET bottles and containers.
It seems that when it comes to manufacturing and recycling of a variety of products, PET is a real winner.