Multielement Flame-Retardant System Constructed with Metal POSS–Organic Frameworks for Epoxy Resin

Abstract

The direct coordination between polyhedral oligomeric silsesquioxane (POSS) and Co forms an assembly of nanoparticles with low specific surface area and leads to a poor dispersion state in the epoxy resin matrix, resulting in unsatisfactory flame-retardant efficiency. Metal–organic frameworks (MOFs), for instance, ZIF-67, provide not only the cobalt element but also the porous framework that endows the nanocomposite of MOFs and POSS with high specific surface area and abundant Co sites in the silica skeleton. Herein, ZIF-67 is hybridized with octacarboxyl POSS, resulting in the removal of the alkaline ligand to form novel metal POSS–organic frameworks (MPOFs). The size differences for organic groups and silica nanocages of POSS vs. micropores of ZIF-67 gave rise to a reverse click reaction, reforming octavinyl POSS isolated on the outer surface of the Co complex, which could be further modified by a phosphorous flame retardant using an addition reaction. The obtained MPOFs-P with 2 wt % loading in epoxy resin could improve the limiting oxygen index value of the composites to 27.0% and pass the V-0 rating in the UL-94 test. Meanwhile, the peaks of the heat release rate and especially the total smoke production were reduced by 46.6 and 25.2%, respectively. The robust char layer reduces the emission of toxic gas CO by 39.8%. The above epoxy product with promising flame retardancy also improved mechanical properties, thanks to the filler with a unique nanostructure. The ingenious work offers enlightenment for the hybridization method of MOFs and POSS to fabricate a multielement flame-retardant system for epoxy resin with high efficacy.

Hollow Superstructure In Situ Assembled by Single‐Layer Janus Nanospheres toward Electromagnetic Shielding Flame‐Retardant Polyurea Composites

“…[ 38 ] It is well known that cobalt in a highly oxidized state has high catalytic activity, which is conducive to improving the compactness and strength of char residue. [ 39 ] In addition, the characteristic peak of Co 2 P 2 O 7 displayed in the XRD signal confirmed that Co‐PA participated in the charcoal formation process during combustion. The XPS results of the char residue are shown in Figure 5l,m, where Co, O, and C elements are present.…”

Novel functionalized isocyanate groups polyhedral oligomeric silsesquioxanes/epoxy composites with advanced thermal and moisture resistance properties

“…Figure 3 illustrates how FT‐IR was used to follow the changes in the chemical structure of MP. The FT‐IR spectrogram of the 3ONa‐POSS exhibits a distinct SiOSi antisymmetric stretching vibration peak at wave number 1133 cm −1 , 25 indicated that the product has a caged structure, and from the FT‐IR spectrogram of 3OH‐POSS, it can be seen that the product has a SiOH stretching vibration peak at 893 cm −1 , suggesting that the SiONa is acidified to SiOH 26 . Further the FT‐IR spectrogram demonstrates that γ‐aminopropylphenyl triethoxysilane reacted with 3OH‐POSS to form caged Ph 7 POSS‐NH 2 , and the disappearance of the stretching vibration peak of SiOH can be seen from the FT‐IR spectrum, while the stretching vibration peak of NH 2 appeared at 3304 cm −1 27 .…”

Flame retarded polyurethane vitrimers containing isocyanurate rings: Synthesis and properties

“…Polymers, including plastics, rubbers, and fibers, are manufactured in large quantities and are widely used in industry, civil, aerospace, furniture, clothing, automobiles, and many other fields. [1][2][3] Most polymeric materials are flammable and when they are ignited, lots of heat, soot, and toxic gases are released, which is harmful to the health of human beings and the environment. 4,5 To address these issues, in the past decades, efforts have been made to change their combustion performance via introducing additive flame retardants to suppress the flame propagation.…”

“…8 An alternative strategy is to explore intrinsic flame retarded polymers which are based on the monomers containing P, 5,9,10 N, [11][12][13] Si 14 or other flame retarded elements. 3,15 N-containing flame retarded components seem more promising, from the viewpoint of sustainability, since N-containing compounds can be sourced widely from biomass. N-containing components exhibit significant heat absorption during the combustion, thereby effectively cooling the polymer surface.…”