Guobo Huang

Nanoclay, intumescent flame retardants, and their combination with chemical modification for the improvement of the flame retardant properties of polymer nanocomposites

AbstractThe flame retardancy of nanoclay, intumescent flame retardants (IFRs), and their combination with chemical modification is investigated in poly(methyl methacrylate) (PMMA) nanocomposites. 2,4,8,10-Tetraoxa-3,9-diphosphaspiro[5.5]-undecane-3,9-dioxide-disubstitutio-acetamide-N,N,N-triethyl-ammonium bromide (PDEABMMT) and 2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]-undecane-3,9-dioxide-disubstitutio-acetamide-N,N-dimethyl-N-hexadecyl-ammonium bromide (PDHAB-MMT) are prepared by ion exchange of sodium montmorillonite with phosphorus-nitrogen containing quarternary ammonium salts including PDEAB and PDHAB. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that PDHAB-MMT achieves tood dispersion in the PMMA matrix and the corresponding nanocomposites PMMA/PDHAB-MMT are formed. The incorporation of PDHAB-MMT into the PMMA matrix obviously improves the nanocomposite thermal properties. Cone calorimeter experiments indicate that the flame retardancy of nanoclay, IFRs, and their combination with chemical modification showed a 5%, 5%, and 9% reduction in the peak heat release rates of PMMA, respectively. The scanning electron microscopy and TEM images confirm that a compact and dense char is formed for PMMA/PDHAB-MMT nanocomposites after combustion.

A phosphorus–nitrogen containing dendrimer reduces the flammability of nanostructured polymers with embedded self-assembled gel networks

A novel phosphorus–nitrogen containing dendrimer DPC–PAMAM has been obtained by the functionalization of amine terminated poly(amidoamine) (PAMAM) with diphenyl phosphoryl chloride (DPC), which is used to modify polyurethane (PU) as an intumescent flame retardant. The gel-phase network, made up of a number of nanofibers, is formed by the self-assembly of DPC–PAMAM dendrimer, which is embedded in the PU matrix by in situ polymerization. The results from thermogravimetric analysis (TGA) and cone calorimeter testing indicate that the addition of the DPC–PAMAM gelator improves thermal stability and reduces significantly the flammability (including peak heat release rate (PHRR), total heat release (THR), average mass loss rate (AMLR), etc.) of PU resin. Furthermore, incorporating the DPC–PAMAM gelator into the polymer matrix enhances the strength of PU resin. The scanning electron microscopy (SEM) images show that a compact and dense intumescent char is formed for PU composites filled with DPC–PAMAM after combustion, which results in the improvement of flame-retardant properties of the polymer matrix by condensed phase flame retardancy.

A lignin-based nano-adsorbent for superfast and highly selective removal of phosphate

The design of an environmentally benign cost-effective adsorbent for superfast removal of phosphate from wastewater is vital but remains a huge challenge. Herein, we have developed a recyclable, low-cost nanostructured bio-adsorbent, poly(ethyleneimine)-graft-alkali lignin loaded with nanoscale lanthanum hydroxide (AL–PEI–La), by a facile fabrication. AL–PEI–La was found to exhibit an excellent adsorption performance toward phosphate ions. For example, 94% of the phosphate ions from 40 mL of a solution containing 50 mg P L−1 phosphate ions was removed in 60 min. Additionally, in a low phosphate concentration wastewater of 2.0 mg P L−1, 95% of phosphate was removed in just 1 min and 99% of phosphate was removed in 15 min and the phosphate concentration dramatically decreased below 50 μg P L−1, which met the standard of eutrophication prevention. The adsorption capacity of AL–PEI–La for phosphate ions was found to be 65.79 mg P g−1, which is 33 times larger than that of lignin. AL–PEI–La shows strong anti-jamming capability in terms of pH value (3.0–9.0) and the co-existing ions of the aqueous solution exhibiting highly selective capacity for phosphate removal. The interactions between surface precipitation and ligand exchange are predominantly responsible for the adsorption process. Importantly, it shows a good reusability and 85.76% of the original adsorption capacity remains after 3 cycles. Thus, the as-designed nanostructured bio-adsorbent with exceptional adsorption effectiveness and efficiency is expected to find extensive applications for remediating the phosphate-contaminated waters.