Isolated Protective Char Layers by Nanoclay Network: Significantly Improved Flame Retardancy and Mechanical Performance of TPV/MH Composites by Small Amount of Nanoclay

High-Temperature Fire Resistance and Self-Extinguishing Behavior of Cellular Graphene

The ability to protect materials from fire is vital to many industrial applications and life safety systems. Although various chemical treatments and protective coatings have proven effective as flame retardants, they provide only temporary prevention, as they do not change the inherent flammability of a given material. In this study, we demonstrate that a simple change of the microstructure can significantly boost the fire resistance of an atomically thin material well above its oxidation stability temperature. We show that free-standing graphene layers arranged in a three-dimensional (3D) cellular network exhibit completely different flammability and combustion rates from a graphene layer placed on a substrate. Covalently cross-linked cellular graphene aerogels can resist flames in air up to 1500 °C for a minute without degrading their structure or properties. In contrast, graphene on a substrate ignites immediately above 550 °C and burns down in a few seconds. Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric studies reveal that the exceptional fire-retardant and self-extinguishing properties of cellular graphene originate from the ability to prevent carbonyl defect formation and capture nonflammable carbon dioxide gas in the pores. Our findings provide important information for understanding graphene's fire-retardant mechanism in 3D structures/assemblies, which can be used to enhance flame resistance of carbon-based materials, prevent fires, and limit fire damage.

Flame Retardant Coatings: Additives, Binders, and Fillers

This review provides an intensive overview of flame retardant coating systems. The occurrence of flame due to thermal degradation of the polymer substrate as a result of overheating is one of the major concerns. Hence, coating is the best solution to this problem as it prevents the substrate from igniting the flame. In this review, the descriptions of several classifications of coating and their relation to thermal degradation and flammability were discussed. The details of flame retardants and flame retardant coatings in terms of principles, types, mechanisms, and properties were explained as well. This overview imparted the importance of intumescent flame retardant coatings in preventing the spread of flame via the formation of a multicellular charred layer. Thus, the intended intumescence can reduce the risk of flame from inherently flammable materials used to maintain a high standard of living.

Effects of collagen fiber addition on the combustion and thermal stability of natural rubber

Abstract

Collagen fiber (CF) and silane coupling agent-modified collagen fiber (MCF) were used as flame retardant filler for natural rubber (NR) modification. The combustion phenomena and properties of composites blended with different dosages of CF or MCF were compared to elucidate the flame retardant mechanism of the composites. The flame retardancy of NR can be enhanced effectively by increasing nitrogen content (the nitrogen content of CF is about 18%), creating air pockets, and structuring the flame retardant network in the composites. MCF failed to structure a flame retardant network in the composite, indicating that its modification effects of MCF are weaker than those of CF. When CF dosage was 30 wt%, the composite can achieve the best flame retardancy, with limited oxygen index of 29.4% and without smoke and dripping during burning. This study demonstrated a new method for the flame retardant modification of NR.

Graphical abstract

Structure and Properties Study of PA6 Nanocomposites Flame Retarded by Aluminium Salt of Diisobutylphosphinic Acid and Different Organic Montmorillonites

Two different types of organic montmorillonite, namely quaternary ammonium salt intercalated MMT (CMMT) and quaternary phosphonium salt intercalated MMT (PMMT) were used as fillers in the flame-retardant polyamide (PA6) based on aluminium salts of diisobutylphosphinic acid (ABPA). The influence of different types of organic montmorillonite (OMMT) on the structure and properties of flame-retardant PA6 nanocomposites were systematically investigated. The X-ray diffraction and transmission electron microscopy results suggested that the introduction of OMMT improved the dispersion of the flame retardant particles independently of the type of OMMT. The derivative thermogravimetry (DTG) curve transformed to one peak from two peaks (representing the degradation of ABPA and PA6, respectively) after incorporation of the OMMT, which further confirmed better ABPA dispersion. Viscoelastic measurements demonstrated that a mechanically stable network structure was formed with the introduction of OMMT or ABPA and OMMT, while PA6/ABPA/PMMT presented the highest storage modulus and viscosity, suggesting a more efficient network structure. From UL-94 and limited oxygen index (LOI) tests, PA6/ABPA/PMMT presented the best flame performance, with a UL-94 of V-0 and a LOI of 33%. In addition, the PA6/ABPA/PMMT presented the lowest peak heat release rate (pHRR) among the investigated samples. Combined with the char layer analysis, it can be deduced that the introduction of PMMT improved the dispersion of ABPA, and promoted the formation of more efficient network structure, before promoting more compact char structures, which finally resulted in improved flame retardancy.