Recycling thermosets have become extremely important due to their ecological and economic benefits. The development of thermosets that undergo reversible polymerization provides a solution to the end-life disposal issue of thermosetting materials. However, the synthesis and recycling of the current chemically recyclable thermosets are harsh, complex, and energyintensive, and their stability is often low. Here, we designed asymmetric acetal-containing thermosets (PRCs) from general phenolic resin and 1,4-cyclohexanedimethanol divinyl ether through one-step "click" cross-linking without using catalysts and solvents and without releasing small-molecule byproducts. PRCs exhibited conspicuous stress relaxation via a dissociative mechanism, corresponding to the superior malleability and reprocess recyclability. Importantly, PRCs presented excellent creep resistance even at 100 °C. In addition, PRCs could be readily and highly efficiently recovered to original phenolic resin via hydrolysis under specific mild acidic conditions but possessed high chemical stability under neutral conditions and even weak acidic conditions or acidic conditions in the absence of organic solvents with outstanding wettability and swellability toward the samples. Thermosets with different properties could be easily achieved via regulating raw materials. This work provides a promising dynamic covalent motif and a practical method to produce readily dual-recyclable (reprocess recyclable and chemically recyclable) thermosets with superior performance and stability.
Polylactide (PLA) is a bio-based polymeric material which is earth abundant in nature. It also possesses abundant strength and stiffness making it a promising material for industrial applications. However, its brittle behavior is currently limiting research work on them. As such, an eco-friendly blending approach is developed in this study in order to fabricate a ductile and toughen PLA composites using renewable bio-based materials as a precursor. Specifically, PLA, epoxidized soybean oil (ESO), and frangible powder form of cellulose nanocrystals (CNCs) are melt blended to prepare the ternary composite system (PLA/CNC/ESO). During the composite routing, it is found out that the ESO successfully attached to the surface of CNC which in turn results in CNC/ESO mixtures in the PLA matrix. This intrinsic combination induces cavitation which consumes the energy produced under the stretching and impacting, resulting in the turning of the PLA's brittle phenomenon. In fact, a reasonable increase in the ductility is observed. The elongation and notched impact strength of the ternary nanocomposite are found to be $32% and $4.8 kJ m −2 , respectively, which are comparatively higher than that of neat PLA or PLA/CNC composites. Differential scanning calorimetry analyses show that the ESO layer on CNC affects the thermal characteristics of PLA in the ternary composite while thermogravimetric analysis shows that there is an increase in the char yield of the composite. Furthermore, scanning electron microscopy analysis shows that the synthesis approach adopted here enables a mechanistically turning of the PLA's brittle phenomenon to ductile.
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