Development of a constitutive model for the compaction of recovered polyethylene terephthalate packages.

To date, PET (polyethylene terephthalate) is the most widely used plastic in packaging and also one of the most recycled polymers worldwide. However, the high transport costs and stagnated prices of recycled PET undermine recycling process profits. Transport costs can lower through compaction, which is still not a completely well-known process. Due to heterogeneous designs, the output density of the compaction process varies. This poses problems during equipment design, selection or operation processes as recovery costs sharply increase if the required density is not met. In this manuscript, the authors develop a constitutive model for the compaction of recovered PET packaging. This experimentally validated model, based on the elasto-plastic behaviour of PET packages, allows the output density range to be predicted according to the compression pressure during PET compaction. Unlike other generic compaction models that need more than two parameters, this model uses only one and better correlates with the experimental results. Unlike existing generic models, the model parameters have a physical meaning, which allows the influence of different factors on the compaction process to be assessed. Finally as a result of the model analysis, we provide some tips to enhance compaction equipment efficiency.

Selective laser fiber welding on woven polymer fabrics for biomedical applications.

Localized cartilage damage is a common problem for younger patients. This can heal, but often results in a painful condition that requires intervention. A welded-woven three-dimensional polymer fabric has been suggested as a suitable cartilage replacement because such materials closely match the mechanical properties of cartilage. However, such materials fare poorly when evaluated with respect to wear. A microscopic investigation of wear mechanisms showed that it is critical that the fibers not deflect laterally under a normal load. This observation led to the use of a new process for selective laser welding of the surface layers of three-dimensional fabrics in order to improve their wear resistance. Experimental evaluations were made in a pin-on-disc arrangement with a biomimetic loading. All materials used in the studies have previously been used in orthopedic devices or meet the requirements for United States Pharmacopeial Convention (USP) Class VI biocompatibility approval. The wear rates were significantly reduced and the lifespan of the fabrics was markedly improved due to surface welding, making this a viable option for cartilage replacement in vivo.