Comparative Study of Fire Resistance and Char Formation of Intumescent Fire-Retardant Coatings Reinforced with Three Types of Shell Bio-Fillers

Synergistic effect of phytic acid and eggshell bio-fillers on the dual-phase fire-retardancy of intumescent coatings applied on cellulosic substrates

Cellulosic substrates, including wood and thatch, have become icons for sustainable architecture and construction, however, they suffer from high flammability because of their inherent cellulosic composition. Current control measures for such hazards include applying intumescent fire-retardant (IFR) coatings that swell and form a char layer upon ignition, protecting the underlying substrate from burning. Typically, conventional IFR coatings are opaque and are made of halogenated compounds that release toxic fumes when ignited, compromising the roofing's aesthetic value and sustainability. In this work, phytic acid, a naturally occurring phosphorus source extracted from rice bran, was used to synthesize phytic acid-based fire-retardants (PFR) via esterification under reflux, along with powdered chicken eggshells (CES) as calcium carbonate (CaCO3) bio-filler. These components were incorporated into melamine formaldehyde resin to produce the transparent IFR coating. It was revealed that the developed IFR coatings achieved the highest fire protection rating based on UL94 flammability standards compared to the control. The coatings also yielded increased LOI values, indicative of self-extinguishing properties. A 17 °C elevation of the IFR coating's melting temperature and a significant ∼172% increase in enthalpy change from the control were observed, indicating enhanced fire-retardancy. The thermal stability of the coatings was improved, denoted by reduced mass losses, and increased residual masses after thermal degradation. As validated by microscopy and spectroscopy, the abundance of phosphorus and carbon groups in the coatings' condensed phase after combustion indicates enhanced char formation. In the gas phase, TG-FTIR showed the evolution of non-flammable CO2, and fire-retardant PO and P-O-C. Mechanical property testing confirmed no reduction in the adhesion strength of the IFR coating. With these results, the developed IFR coating exhibited enhanced fire-retardancy whilst remaining optically transparent, suggestive of a dual-phase IFR protective mechanism involving the release of gaseous combustion diluents and the formation of a thermally insulating char layer.

Exploiting Waste towards More Sustainable Flame-Retardant Solutions for Polymers: A Review

The development of sustainable flame retardants is gaining momentum due to their enhanced safety attributes and environmental compatibility. One effective strategy is to use waste materials as a primary source of chemical components, which can help mitigate environmental issues associated with traditional flame retardants. This paper reviews recent research in flame retardancy for waste flame retardants, categorizing them based on waste types like industrial, food, and plant waste. The paper focuses on recent advancements in this area, focusing on their impact on the thermal stability, flame retardancy, smoke suppression, and mechanical properties of polymeric materials. The study also provides a summary of functionalization methodologies used and key factors involved in modifying polymer systems. Finally, their major challenges and prospects for the future are identified.

Assessing the Impact of Sepiolite-Based Bio-Pigment Infused with Indigo Extract on Appearance and Durability of Water-Based White Primer

The objective of this study is to evaluate how two varying amounts of sepiolite-based powder, infused with indigo extract, affect the appearance and durability of a water-based, white primer. To examine the influence of this eco-friendly pigment on the coatings' overall appearance, assessments were performed for color, gloss, and surface roughness. Additionally, the coatings were investigated through optical and electron microscopic observations, to evaluate the distribution of the pigment within the polymer matrix. The effect of the pigment on the coating's durability was assessed through accelerated tests, including exposure in a salt spray chamber and a UV-B chamber. These tests aimed to evaluate the emergence of defects and changes in the appearance of the samples over time. Furthermore, the impact of different quantities of sepiolite-based powder on the coating's ability to act as a barrier was assessed using liquid resistance tests and contact angle measurements. These evaluations aimed to understand how the coating responded to various liquids and its surface properties concerning repellency or absorption. In essence, this study underscores the considerable influence of the eco-friendly pigment, demonstrating its capacity to introduce unique color and texture variations in the paint. Moreover, the inclusion of the pigment has enhanced the coating's color stability, its ability to act as a barrier, and its overall durability when exposed to harsh environments.

Understanding the Flame Retardant Mechanism of Intumescent Flame Retardant on Improving the Fire Safety of Rigid Polyurethane Foam

Combinations of multiple inorganic fillers have emerged as viable synergistic agents for boosting the flame retardancy of intumescent flame retardant (IFR) polymer materials. However, few studies on the effect of multiple inorganic fillers on the flame retardant behavior of rigid polyurethane (RPU) foam have been carried out. In this paper, a flame retardant combination of aluminum hydroxide (ATH) and traditional flame retardants ammonium polyphosphate (APP), pentaerythritol (PER), melamine cyanurate (MC), calcium carbonate (CC), and expandable graphite (EG) was incorporated into RPU foam to investigate the synergistic effects of the combination of multiple IFR materials on the thermal stability and fire resistance of RPU foam. Scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) revealed that 8 parts per hundred polyols by weight (php) filler concentrations were compatible with RPU foam and yielded an increased amount of char residue compared to the rest of the RPU samples. The flame retardancy of multiple fillers on intumescent flame retardant RPU foam was also investigated using cone calorimeter (CCTs) and limiting oxygen index (LOI) tests, which showed that RPU/IFR1 (APP/PER/MC/EG/CC/ATH) had the best flame retardant performance, with a low peak heat release rate (PHRR) of 82.12 kW/m², total heat release rate (THR) of 15.15 MJ/m², and high LOI value of 36%. Furthermore, char residue analysis revealed that the use of multiple fillers contributed to the generation of more intact and homogeneous char after combustion, which led to reduced decomposition of the RPU foam and hindered heat transfer between the gas and condensed phases.

Understanding the Influence of Gypsum upon a Hybrid Flame Retardant Coating on Expanded Polystyrene Beads

A low-cost and effective flame retarding expanded polystyrene (EPS) foam was prepared herein by using a hybrid flame retardant (HFR) system, and the influence of gypsum was studied. The surface morphology and flame retardant properties of the synthesized flame retardant EPS were characterized using scanning electron microscopy (SEM) and cone calorimetry testing (CCT). The SEM micrographs revealed the uniform coating of the gypsum-based HFR on the EPS microspheres. The CCT and thermal conductivity study demonstrated that the incorporation of gypsum greatly decreases the peak heat release rate (PHRR) and total heat release (THR) of the flame retarding EPS samples with acceptable thermal insulation performance. The EPS/HFR with a uniform coating and the optimum amount of gypsum provides excellent flame retardant performance, with a THR of 8 MJ/m2, a PHRR of 53.1 kW/m2, and a fire growth rate (FIGRA) of 1682.95 W/m2s. However, an excessive amount of gypsum weakens the flame retardant performance. The CCT results demonstrate that a moderate gypsum content in the EPS/HFR sample provides appropriate flame retarding properties to meet the fire safety standards.

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.