Functionalized lignin nanoparticles assembled with MXene reinforced polypropylene with favorable UV-aging resistance, electromagnetic shielding effects and superior fire-safety.

Deterioration in mechanical performances and aging resistance due to the introduction of flame retardants is a major obstacle for bio-based fire-safety polypropylene (PP). Herein, we reported a kind of functionalized lignin nanoparticles assembled with MXene (MX@LNP), and applied it to construct the flame-retardant PP composites (PP-MA) with superior fire safety, excellent mechanical performance, electromagnetic shielding effects and aging resistance. Specifically, the PP-MA doped with only 18 wt% flame-retardant additives (PP-MA18) achieved the UL-94 V-0 rating. In comparison to pure PP, PP-MA18 presented a greatly decreased peak of heat release rate (pHRR), total heat rate (THR), and peak smoke production rate (pSPR) by 79.7 %, 69.0 % and 75.8 %, respectively, and satisfactory decrease in total flammable and toxic volatiles evolved. The formed fine solid microstructure of carbon residuals effectively promoted the compactness of char layers. More importantly, the nano-effect and the strong interface interaction between the complexed MX@LNP and PP enhanced the tensile strength (45.78 MPa) and elongation at break (725.95 %) of PP-MA. Additionally, the significant ultraviolet absorption and electromagnetic wave dissipation performance of MXene and lignin enabled excellent aging resistance and electromagnetic shielding effects of PP-MA compared with PP. This achieved MX@LNP afforded a novel approach for developing flame retardant materials with excellent application performance.

Novel charge-mosaic membranes.

Novel charge-mosaic composite membranes composed of cation and anion permeable domains were prepared. Poly(4-methylstyrene-isoprene-styrene-isoprene-4-methylstyrene) pentablock copolymer (MsISIMs), poly(isoprene-4-methylstyrene) diblock copolymer (IMs), and poly(isoprene-styrene-isoprene) triblock copolymer (ISI), used as the precursor of the charge-mosaic membranes, were polymerized from styrene (S), isoprene (I), and 4-methylstyrene (Ms). MsISIMs and a blend of ISI and IMs were then dissolved in benzene and cast on a polypropylene microporous supporting membrane. After chemical modification, the MsISIMs and IMs/ISI charge-mosaic composite membranes were obtained. Our experimental results show that the IMs/ISI charge-mosaic composite membrane is similar in membrane structure and properties to the MsISIMs charge-mosaic composite membrane.

Effect of compatibility of PVC/P2 alloy system on membrane structure and performance.

The effects of the secondary polymer component (P(2)) on poly(vinyl chloride) (PVC)/P(2) alloy membrane structure and performance were systematically investigated. A series of P(2) with varying compatibility with PVC used in this study included vinyl chloride-vinyl acetate copolymer (VC-co-VAc); copolymer of vinyl chloride, vinyl acetate-maleic anhydride copolymer (VC-co-VAc-co-MAL); isobutylene-maleic anhydride copolymer (IB-co-MAL); poly(methyl methacrylate) (PMMA); poly(vinylidene dichloride) (PVDC); and styrene-acrylonitrile copolymer (SAN). Alloy membranes were prepared by means of solution blending-phase inversion technique. On the basis of our experimental results, the compatibility of PVC/P(2) was proved to be the most critical factor affecting the alloy membrane structure and performance. Systems with good compatibility, such as PVC/VC-co-VAc, are more suitable for preparing membranes with small pore size; whereas systems with partial compatibility, such as PVC/PMMA, are more favored for the formation of large-pore membranes.

Poly(vinyl alcohol)-based polyelectrolyte pervaporation membranes.

By modifying poly(vinyl alcohol) (PVA), phosphatic anionic PVA (P-PVA) and quaternary ammonium cationic PVA (C-PVA) with various degrees of substitution (D.S.) were synthesized. The effects of synthesis conditions on the degree of substitution were studied. With these two kinds of materials, polyelectrolyte complexes were formed and their solubilities in water were studied. Pervaporation composite membranes were prepared from P-PVA, C-PVA, and their polyelectrolyte complexes. Some of the membranes showed good separation performance. The polyelectrolyte complex membrane prepared by mixing P-PVA (D.S. 2.3%) and C-PVA (D.S. 2.9%) with weight ratio of 1/1, showed a permeation rate of 378 g/m(2)h and separation factor of 2,250 for dehydration of ethanol/water mixture (ethanol 95.4 wt%) at a feed temperature of 75 degrees C. Some factors that influenced pervaporation performance included type of polyelectrolyte, degree of substitution, ratio of polyanion and polycation, feed temperature, feed concentration, and elapsed time. Solvent resistance of pervaporation composite membranes was also evaluated.