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Tuesday, March 18, 2014

Does recycled glass have the same properties as the original material?

Glass recycling industry
Structural integrity is key when recycling glass 
The ease and accessibility of glass recycling has revolutionized the bottling, window and packaging industries. Through the abundant adoption of glass recycling technologies, there has been a worldwide decrease in the demand for new glass products to be manufactured, reducing the carbon footprint and raw material use of materials such as sodium carbonate, lime, dolomite, silicon dioxide, aluminium oxide, sodium sulfate, and sodium chloride. The properties of recycled glass is an interesting area of manufacturing to consider from a quality and an environmental perspective.

A background to commercial glassware


Soda-lime-silica glass, the most abundant form of commercial glass, is utilized in products such as bottles, windowpanes and glass containers and bakeware. The process by which glass in recycles varies from municipality to municipality, however the common method is for recyclers to separate glass by chemical composition, then by colour, then allow the glass to be crushed into a substance called cullet, ready for remelting. As the process of recycling glass saves the manufacturing industry millions of dollars on energy costs and saves the environment hundreds of thousands of kilograms of raw materials annually, the practice is one that is celebrated by businessmen and environmental activists alike. However, the question about the similarities of the material properties of recycled glass in comparison to its original material is one that is valid in terms of product quality.

Properties of recycled glass


Recycled glass is a material that is fully recyclable, if done in the proper manner with attention to detail and correctly configured equipment. Through the melting of glass at temperatures greater than 1200 degrees Celsius, the material becomes a liquid phase that can be set into molds for new applications. Through this very high temperature melting process, impurities in the crushed glass material are separated from the existing material, which allows for the new glass components to be free from defect. With a proper cooling process that allows for an even distribution of commonly-temperature air, the glass can settle into its final solid state with the material properties identical to those that it once had in a previous generation. Simply put, glass is a material that has the potential to recycle itself for an indefinite number of iterations in a closed-loop, maintaining a high degree of material properties throughout its recycling process. This process, however, must be conducted in a proper manner to ensure the high material property standards of commercial manufacturers and consumers alike.

Concerns for glass recycling


Glass recycling is a great potential money saver while maintaining the structural integrity of the original product, but the process is one that must be done so in an optimal manner in order to ensure the highest degree of product quality. A misassportment of glass type by a recycler of glass collecting agency can potentially lead to different chemical compositions of glass being melted together to form a mixture of impure glass material for a specific application. In addition, the improper cleaning of glass material may lead to defects in the eventual product if there are foreign contaminants in the mixture of liquid material. Finally, an unoptimized cooling process can lead to cracks, coring or a heterogeneous material composition of the final recycled product, all factors that may inadvertently lower the properties of the recycled glass in comparison to the original material.

Image license: Chmouel Boudjnah, GFDL, CC BY-SA 3.0