With the burning issue of air, land and water pollution, the premonition of looking forward towards a future devoid of any kind of oil and gas reserves has caused a paradigm shift towards recycling, recovery of any synthetic polymer and also to dispose them off environmentally. Among them are plastics such as polyethylene terephthalate and poly vinyl chloride. Polyurethane (PU) is also under the scanner to dispose of or recycle it environmentally and sustainably. PU is at present the sixth most utilized polymer all over the world with a production of nearly 18 million tonnes per annum, which roughly estimates a daily production of PU products of greater than a million of cubic metres. Its thermostable nature is one of the major reasons for its higher preference over other polymers. This review article discusses the current disposal and technologies available to recycle waste PU foams and also sheds some light on some additional work being done in the field to upgrade the existing technology. Interestingly, some methods mentioned here are probably undergoing scale-up trials runs by now. Currently, the most researched and studied ones are mechanical recycling and glycolysis. But microbial and enzymatic disposal methods can be turned into full-scale industrial recycling processes in the near future. Additionally, we can see an archetypal shift from traditional oil-based sources to the agrarian sources.

Ferrofluids prepared by dispersing superparamagnetic Fe₃O₄@C core–shell nanoparticles in water exhibited exceptional enhancement in thermal conductivity without an external magnetic field.

This article aims at the synthesis of highly stable γ-Fe₂O₃ magnetic nanoparticles and their ferrofluids using different base liquids such as liquid paraffin, motor oil and sunflower oil for heat transfer applications. Phase and morphology of the synthesized nanoparticles were probed using XRD, SEM and FTIR spectroscopy. The average nanoparticle size of γ-Fe₂O₃ magnetic nanoparticles was found to be 13 nm. Stability of the ferrofluids was monitored by visually observing the aggregation nature of the nanoparticles for 180 days. The ferrofluid prepared using motor oil as a base fluid exhibited high stability (for more than 1 year) and a mean enhancement of 77% in thermal conductivity at 1.5 vol% nanoparticles was observed as compared to base fluid. The viscosity of the ferrofluids was also measured and found to be 18, 38 and 8 cP at 27 °C for the liquid paraffin based, motor oil based and sunflower oil based ferrofluid, respectively.