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The sustainable development of innovative eco-friendly multifunctional nanocomposites, possessing superior characteristics, is a noteworthy topic. Novel semi-interpenetrated nanocomposite films based on poly(vinyl alcohol) covalently and thermally crosslinked with oxalic acid (OA), reinforced with a novel organophosphorus flame retardant (PFR-4) derived from co-polycondensation in solution reaction of equimolar amounts of co-monomers, namely, bis((6-oxido-6H-dibenz[c,e][1,2]oxaphosphorinyl)-(4-hydroxyaniline)-methylene)-1,4-phenylene, bisphenol S, and phenylphosphonic dichloride, in a molar ratio of 1:1:2, and additionally doped with silver-loaded zeolite L nanoparticles (ze-Ag), have been prepared by casting from solution technique. The morphology of the as prepared PVA-oxalic acid films and their semi-interpenetrated nanocomposites with PFR-4 and ze-Ag was investigated by scanning electron microscopy (SEM), while the homogeneous distribution of the organophosphorus compound and nanoparticles within the nanocomposite films has been introspected by means of energy dispersive X-ray spectroscopy (EDX). It was established that composites with a very low phosphorus content had noticeably improved flame retardancy. The peak of the heat release rate was reduced up to 55%, depending on the content of the flame-retardant additive and the doping ze-Ag nanoparticles introduced into the PVA/OA matrix. The ultimate tensile strength and elastic modulus increased significantly in the reinforced nanocomposites. Considerably increased antimicrobial activity was revealed in the case of the samples containing silver-loaded zeolite L nanoparticles. [ABSTRACT FROM AUTHOR]

In the view of the advantages of using P, N, Si and graphene oxide (GO) for the development of flame retardants materials, a multi-structure synergistic composite was synthesized by grafting a novel nitrogen-containing polyhedral oligomeric silsesquioxane (HAK) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) on the surface of GO nanosheet. In the first step, 2-hydroxyethyl acrylate was selectively reacted, and then, HAK was synthetized by the condensation of the aza-Michael addition product with 3-(methacryloyloxy)propyltrimethoxysilane. Finally, the GO obtained by an innovative variant of Marcano-Tour improved exfoliation method was functionalized, first with DOPO, and then with HAK. The structural, morphological and surface properties of GO and GO-DOPO-HAK were investigated by means of XRD, TEM–EDX, FT-IR, Raman, zeta potential and XPS techniques, and it was evidenced the functionalization of GO with DOPO, and then with HAK. The performed microscale combustion calorimetry (MCC) and TG measurements indicated a great potential of the GO-DOPO-HAK as flame retardant material as the obtained residual weight for this sample was found to be the highest one compared to the other investigated samples. MCC analyses further revealed a major decrease in heat release capacity (HRC) and a significant increase in char yield, results that confirm the great potential of GO-DOPO-HAK as flame retardancy material. [ABSTRACT FROM AUTHOR]

The preparation of a novel polyphosphonate (PSFR) is described here, starting from phenylphosphonic dichloride and an equimolecular mixture containing equal amounts of two bisphenols, namely 4,4′‐dihydroxydiphenyl sulfone and 2‐(6‐oxido‐6H‐dibenzo<1,2>oxaphosphorin‐6‐yl)‐1,4‐benzenediol, following the polycondensation reaction in solution. Then, new environmental‐friendly nanocomposites having improved flame retardancy have been prepared by incorporating PSFR and halloysite nanotubes (HNTs) into epoxy resin. The effect of PSFR and HNTs contents on the chemical and physical characteristics of epoxy nanocomposites was investigated. The success of the reactions was monitored by infrared spectroscopy (FTIR) while microscopic related techniques (SEM) gave information on the morphology of the products. The thermosets exhibit glass transition temperatures in the range of 62.4–97.1°C and thermal decomposition temperatures in the interval of 296–359°C. The appearance of the char residues obtained by pyrolysis was studied by SEM measurements. The flammability behavior has been studied by microscale combustion calorimetry (MCC) tests. A considerable improvement in the flame retardancy of the thermosets was obtained by simultaneous incorporation of HNTs (10 wt%) and PSFR (equivalent of 1 wt% P) into epoxy resin. [ABSTRACT FROM AUTHOR]

While plastics are regarded as the most resourceful materials nowadays, ranging from countless utilities including protective or decorating coatings, to adhesives, packaging materials, electronic components, paintings, furniture, insulating composites, foams, building blocks and so on, their critical limitation is their advanced flammability, which in fire incidents can result in dramatic human fatalities and irreversible environmental damage. Herein, epoxy-based composites with improved flame-resistant characteristics have been prepared by incorporating two flame retardant additives into epoxy resin, namely 6-(hydroxy(phenyl)methyl)-6H-dibenzo[c,e][1,2]oxaphosphinine-6-oxide (PFR) and boric acid (H3BO3). The additional reaction of 9,10-dihydro-oxa-10-phosphophenanthrene-10-oxide (DOPO) to the carbonyl group of benzaldehyde yielded PFR, which was then used to prepare epoxy composites having a phosphorus content ranging from 1.5 to 4 wt%, while the boron content was 2 wt%. The structure, morphology, thermal stability and flammability of resulted epoxy composites were investigated by FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry (MCC). Thermogravimetric analysis indicated that the simultaneous incorporation of PFR and H3BO3 improved the thermal stability of the char residue at high temperatures. The surface morphology of the char residues, studied by SEM measurements, showed improved characteristics in the case of the samples containing both phosphorus and boron atoms. The MCC tests revealed a significant reduction in flammability as well as a significant decrease in heat release capacity for samples containing both PFR and H3BO3 compared to the neat epoxy thermoset. [ABSTRACT FROM AUTHOR]