Internal water circulation mediated synergistic co-hydrolysis of PET/cotton textile blends in gamma-valerolactone.

Recycling strategies for mixed plastics and textile blends currently aim for recycling only one of the components. Here, we demonstrate a water coupling strategy to co-hydrolyze polyester/cotton textile blends into polymer monomers and platform chemicals in gamma-valerolactone. The blends display a proclivity for achieving an augmented 5-hydroxymethylfurfural yield relative to the degradation of cotton alone. Controlled experiments and preliminary mechanistic studies underscore that the primary driver behind this heightened conversion rate lies in the internal water circulation. The swelling and dissolving effect of gamma-valerolactone on polyester enables a fast hydrolysis of polyester at much lower concentration of acid than the one in the traditional hydrolysis methods, effectively mitigating the excessive degradation of cotton-derived product and undesirable product formation. In addition, the system is also applicable to different kinds of blends and PET mixed plastics. This strategy develops an attractive path for managing end-of-life textiles in a sustainable and efficient way.

Exploiting valuable supramolecular materials from waste plastics.

A new family of supramolecular materials is exploited from waste thermosets via a one-step retrosynthetic approach, which exhibits distinguished adhesion properties in dry/wet environments, good corrosion resistance and dynamic reversibility. This work opens up a wide design space for supramolecular materials with excellent performances and proposes a new strategy for efficient utilization of hybrid degraded products.

Multicycling of Epoxy Thermoset Through a Two-Step Strategy of Alcoholysis and Hydrolysis using a Self-Separating Catalysis System.

Plastic has now become a contradiction between civilization and pollution that human society has to resolve. The recycling of thermosetting plastics in waste plastics is a huge challenge since they are difficult to remold like thermoplastic plastics due to their high crosslinking density. Here, a new strategy was developed to achieve multicycling of anhydride-cured epoxy thermosets. The process consisted of mild and high-efficiency alcoholysis catalyzed by potassium phosphate/low-boiling alcohol system, and subsequent fast hydrolysis to obtain degradation products rich of carboxyl groups. The degradation products were reused as curing agent to prepare new anhydride-cured epoxy thermosets without sacrifice of high strength and stability. Moreover, the new epoxy thermosets could still be repeatedly recycled using the same protocol. The insolubility of potassium phosphate in ethanol at room temperature made the separation and reuse of the catalyst more convenient. The use of low-boiling alcohol not only allowed high-efficiency degradation but also enabled easy separation from the degradation products. The excellent degradation performance was attributed to the improved swelling of the thermoset and the increased solubility of potassium phosphate induced by small amounts of water in the alcohol. This research provides a recycling method that can reintegrate thermoset waste plastics into remodeling ones under the background of circular economy.

Multiple functional materials from crushing waste thermosetting resins.

Novel applications of waste thermosetting resins are developed by facile mechanical crushing, and their excellent performances are demonstrated in oil-water separation, superhydrophobic coatings with diverse water adhesion, acid liquid/gas monitoring and information storage. This work provides new ideas for waste treatments and functional material design, as well as speeds up the transformation of waste resins from laboratory achievements to industrial applications. Moreover, it can also improve the utilization efficiency of non-renewable resources and meet the requirements of energy conservation and environmental protection.