A triol‐functional crosslinker combining the thermoreversible properties of Diels–Alder (DA) adducts in one molecule is designed, synthesized, and used as an ideal substitute of a traditional crosslinker to prepare thermal recyclable cross‐linked polyurethanes with excellent mechanical properties and recyclability in a very simple and efficient way. The recycle property of these materials achieved by the DA/retro‐DA reaction at a suitable temperature is verified by differential scanning calorimetry and in situ variable temperature solid‐state NMR experiments during the cyclic heating and cooling processes. The thermal recyclability and remending ability of the bulk polyurethanes is demonstrated by three polymer processing methods, including hot‐press molding, injection molding, and solution casting. It is notable that all the recycled cross‐linked polymers display nearly invariable elongation/stress at break compared to the as‐synthesized samples. Further end‐group functionalization of this single molecular DA crosslinker provides the potential in preparing a wide range of recyclable cross‐linked polymers.
Developing a green and sustainable method to upgrade biogas wastes into high value-added products is attracting more and more public attention. The application of solid residues as a performance enhancer in the manufacture of biofilms is a prospective way to replace conventional plastic based on fossil fuel. In this work, solid digestates from the anaerobic digestion of agricultural wastes, such as straw, cattle and chicken manures, were pretreated by an ultrasonic thermo-alkaline treatment to remove the nonfunctional compositions and then incorporated in plasticized starch paste to prepare mulching biofilms by the solution casting method. The results indicated that solid digestate particles dispersed homogenously in the starch matrix and gradually aggregated under the action of a hydrogen bond, leading to a transformation of the composites to a high crystalline structure. Consequently, the composite biofilm showed a higher tensile strength, elastic modulus, glass transition temperature and degradation temperature compared to the pure starch-based film. The light, water and GHG (greenhouse gas) barrier properties of the biofilm were also reinforced by the addition of solid digestates, performing well in sustaining the soil quality and minimizing N2O or CH4 emissions. As such, recycling solid digestates into a biodegradable plastic substitute not only creates a new business opportunity by producing high-performance biofilms but also reduces the environmental risk caused by biogas waste and plastics pollution. 相似文献
This study was conducted in a continuous three-stage system of anaerobic (R1)-anoxic(R2)-aerobic (R3) reactors with synthetic
wastewater containing phenol (1000 mg/L), chemical oxygen demand (COD) (3000 mg/L), CN− (30 mg/L), SCN−(400 mg/L), and NH
4+
-N (600 mg/L) as principal pollutants and well-acclimated heterogeneous microbial cultures. The final effluent was partially
returned to R2 with a recycle ratio of 1. Anaerobic stage served to detoxify the feed by removing up to 80% of cyanide. Complete
SCN− removal and denitrification could be achieved in the anoxic stage by utilizing phenol as an internal source of carbon. Nitrification
efficiency of 93% was obtained in the aerobic reactor. The results demonstrated that the three-stage system can give the desired
final treated effluent quality (0 mg/L of phenol, 0.2 mg/L of CN−, 210 mg/L of COD, and 20 mg/L of NH
4+
-N) and that the NO
3−
-N concentration can be lowered by a higher recycle ratio. 相似文献