After we achieved good dehydrogenation ratio, preliminary microwave-initiated oxidation has been carried out to depolymerize the polymer to our desired functional monomers (Figure 2). Later on, other strong oxidation catalysts will be evaluated for their ability to perform oxidative degradation of the dehydrogenated HDPE into dicarboxylic acid end products. The second stage in our depolymersiation strategy can be adapted to yield variety of raw materials such as acids, alcohols and amines, which we would like to explore in future projects.
Figure 2. Further development plan of DeHPOL.
Long-chain aliphatic diols, diacids and diamines are essential monomers to develop new long-chain aliphatic polymers (polyesters, polyamides, polyurethanes, polyureas, polyepoxides etc.), which gives the possibility to bridge the gap between semicrystalline polyolefins and traditional polycondensates.
3 They will have more stable connections than polycondensates and less stable connections than pure polyolefins. They can thus increase the degradability and recyclability of “polyethylene-like” long-chain polycondensates in coatings, packaging, adhesives, foam, and plastic parts, at the same time maintaining the quality like polyolefins. Desirably, such polycondensates could be depolymerized to their respective monomers to be an essential part of a closed loop economy.
There is a start-up working on similar concept, which is under development in the US (as
link here). Yet compared to the recycling demand growth and growing market, the methods and solutions for HDPE uprecycling are very limited, therefore with our method we have a chance to be a solution provider.