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Polymers are used in every aspect of day-to-day life, from plastic packaging to engineering components of consumer goods such as refrigerators and washing machines. It has long been established that processing of polymeric materials to produce these components can lead to degradation through a range of different chemical, thermal, and mechanical pathways. In solution-based polymer processing, elongational flow, which imparts mechanical force, is inherent to many industrial processing techniques and is therefore difficult to avoid. Under sufficiently strong conditions, elongational flows can stretch polymer chains and may ultimately cause chain scission, resulting in polymer degradation. However, studying these flows during processing remains challenging as industrial equipment is based on closed systems made from metallic components, making visualisation of the flow impossible. On the other hand, microfluidic devices are ideal platforms to characterise the flow behaviour of polymer solutions. These devices are low-cost, transparent, and highly versatile in design, making them ideal platforms for replicating and studying the elongational flows that lead to polymer degradation in industrial processes. In this review, we discuss the use of microfluidic devices to mimic elongational flows found during solution-based industrial processes to understand the resulting polymer degradation. We outline how microfluidic device design controls elongational flow and thus controls polymer degradation. Finally, we highlight the potential to integrate novel characterisation methods to detect polymer degradation in-situ during flow in microfluidic devices. This review brings together an understanding of polymer degradation and microfluidic device design and fabrication. The ability to examine and characterise industrially relevant elongational flows shows immense promise for reducing polymer degradation during processing.
Zhu et al. (Mon,) studied this question.