Impact of crosslinking on organic solvent nanofiltration performance in polydimethylsiloxane composite membrane: Probed by in-situ low-field nuclear magnetic resonance spectroscopy

A solvent-free processed low-temperature tolerant adhesive

Ultra-low temperature resistant adhesive is highly desired yet scarce for material adhesion for the potential usage in Arctic/Antarctic or outer space exploration. Here we develop a solvent-free processed low-temperature tolerant adhesive with excellent adhesion strength and organic solvent stability, wide tolerable temperature range (i.e. -196 to 55 °C), long-lasting adhesion effect ( > 60 days, -196 °C) that exceeds the classic commercial hot melt adhesives. Furthermore, combine experimental results with theoretical calculations, the strong interaction energy between polyoxometalate and polymer is the main factor for the low-temperature tolerant adhesive, possessing enhanced cohesion strength, suppressed polymer crystallization and volumetric contraction. Notably, manufacturing at scale can be easily achieved by the facile scale-up solvent-free processing, showing much potential towards practical application in Arctic/Antarctic or planetary exploration.

Controllable hydrogen-bonded poly(dimethylsiloxane) (PDMS) membranes for ultrafast alcohol recovery

The lack of efficient separation membranes limits the development of bio-alcohol purification via a pervaporation process. In this work, novel controllable hydrogen-bonded poly(dimethylsiloxane) (PDMS) membranes are prepared from self-synthesized supramolecular elastomers for alcohol recovery. Different from the conventional covalently-bonded PDMS membranes, the hydrogen-bonding content and therefore the crosslinking degree in the as-synthesized PDMS membranes can be exactly regulated, by the suitable molecular design of the supramolecular elastomers. The effects of hydrogen-bonding content on the flexibility of the polymer chains and the separation performance of the resultant supramolecular membranes are investigated in detail. In comparison with the state-of-the-art polymeric membranes, the novel controllable hydrogen-bonded supramolecular PDMS membrane exhibits ultrahigh fluxes for ethanol (4.1 kg m-2 h-1) and n-butanol (7.7 kg m-2 h-1) recovery from 5 wt% alcohol aqueous solutions at 80 °C, with comparable separation factors. The designed supramolecular elastomer is therefore believed to provide valuable insights into the design of next-generation separation membrane materials for molecular separations.

Preparation and Properties of a Novel Cross-Linked Network Waterborne Polyurethane for Wood Lacquer

Waterborne polyurethane (WPU) is a waterborne coating with excellent physicochemical properties. Its deficiencies of water resistance, chemical resistance, staining, and hardness have limited the wide application of polyurethane in the wood lacquer market. In this study, polycarbonate diols (PCDL) were used as soft segments and WPCU was modified by cross-linking using Trimethylolpropane (TMP) to prepare polycarbonate type WPU (WPCU) with cross-linked network structure. The new wood lacquer was prepared by adding various additives and tested by applying it on wood board. The successful synthesis of WPCU was determined by FTIR testing, and the cross-linking degree of WPCU was probed by low-field NMR. The viscosity of the cross-linked WPCU emulsion showed a decreasing trend compared to the uncross-linked WPCU emulsion, and WPCU-2 had the smallest particle size. Compared with the uncrosslinked WPCU film, the crosslinked WPCU film had lower water absorption (2.2%), higher water contact angle (72.7°), excellent tensile strength (44.02 MPa), higher thermomechanical, and better water and alcohol resistance. The effect of crosslinker content on the microphase separation of WPCU chain segments on the surface roughness of the film was investigated by SEM. The wood paint prepared by WPCU emulsion has good dry heat resistance, chemical resistance, and adhesion, and the hardness of the wood paint when the TMP content is 3% reaches H. It also has good resistance to sticky stains, which can be used to develop new wood lacquer.