Flame-retarded Polystyrene: Investigating Chemical Interactions between Ammonium Polyphosphate and MgAl Layered Double Hydroxide

Potential flame retardants, MgAl-LDH and ammonium polyphosphate (APP), were added to neat polystyrene (PS) individually or in combinations at weight fractions no greater than 10%. Structural morphologies of MgAl-LDH and the corresponding PS nanocomposites were established via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) and cone calorimetry were used to study the thermal stability and fire performance of the composites. Time to ignition is greatly reduced for PS composites when compared to the virgin polymer. Synergistic effects were observed in both TGA and cone calorimetry for formulations containing both MgAl-LDH and APP. Physical and chemical interactions between MgAl-LDH and APP are responsible for the observed synergy in thermal stability and fire performance

Nanostructured Layered Copper Hydroxy Dodecyl Sulfate: A Potential Fire Retardant for Poly(vinyl Ester) (PVE)

Composites of poly(vinyl ester) (PVE) with copper hydroxy dodecyl sulfate (CHDS) were prepared by thermal curing. The efficiency of the additive, CHDS, in reducing flammability is demonstrated via cone calorimetry and thermogravimetric analysis (TGA). The addition of 1-10% by mass of the CHDS additive resulted in significant increments in char formation (~4-11%) from thermogravimetric analysis (TGA). Incorporation of the CHDS into the polymer matrix at these low concentrations leads to substantial reductions in the total heat release (~20-30%) but no significant change in the peak heat release rate. The composite materials generally ignite more quickly, however, the flame extinguishes faster for the composites relative to the virgin polymer. X-ray diffraction (XRD) and infrared spectroscopic analyses of the residues collected at various stages during thermal decomposition of the composities, suggest the participation of copper-containing species in promoting enhanced thermal stability of PVE

Development of 2-D Nanostructured Layered Hydroxy Salts (LHSs) and Hydroxy Double Salts (HDSs) for New Applications: Anionic Exchange Kinetics and Polymer Modification

Hydroxy double salts (HDSs) and layered hydroxy salts (LHSs) are a class of 2-D nanostructured materials with nanometer sized galleries. These compounds exhibit interesting physical properties and have many potential and demonstrated applications in various fields, including: anion separations, drug delivery, environmental water decontamination, catalysis, magnetism, and fire retardancy. These compounds have structural properties that can be utilized as design parameters to fine-tune for improved effectiveness in chosen areas of application. The goal of this work is to explore the various synthetic methods and characterization techniques for HDSs and LHSs that will yield important structural information and corresponding reactivities of these nano materials. With this fundamental insight into structure/reactivity relationships, these compounds can be tailored for specific applications as detailed above. Chapter 1 gives a general introduction of these nanostructured materials and provides a detailed literature review on structurally similar smectite clays. In Chapter 2, preparation and characterization of three model compounds, zinc copper acetate (ZCA), zinc nickel acetate (ZNA), and zinc hydroxy acetate (ZHA) are described. Anionic exchange kinetics were performed using the three model compounds and the results were correlated to their structures and the exchange anion size. The effect of varying the exchange reaction conditions such as temperature, time, and anion concentration on the morphology of the exchange products are discussed. Chapter 3 presents an investigation of the thermal degradation of ZCA, ZNA, and ZHA and highlights the possible catalytic effect that ZnO may have on the ketonization of acetic acid to acetone in the gas phase. The presence of a second metal with Zn is investigated to see if that has an effect on the ZnO crystal growth. Chapter 4 describes the efforts taken to improve the thermal stability and fire retardancy of poly (methyl methacrylate) using copper-containing layered materials. Thermal stability and flammability are evaluated using thermogravimetric analysis and cone calorimetry respectively. Chapter 5 demonstrates the use of the Flynn-Wall-Ozawa (FWO) isoconversional method to estimate the apparent activation energy as a function of conversion fraction for pure polystyrene versus its respective composites containing putative thermal stabilizers. Copper hydroxy dodecyl sulfate is used as a potential fire retardant with poly (vinyl esters) and this work is presented in Chapter 6. The summary of this work and suggested future endeavors are described in Chapter 7

Enhancing the Fracture Toughness Properties by Introducing Anchored Nano-Architectures at the Metal–FRP Composite Interface

This paper presents a novel technique for improving aluminium⁻glass/epoxy composite interfacial bonding through the generation of metallic nano-architectures on the metal surface. Silver nanowires (AgNWs) deposited via solution casting at varying concentrations and annealed at different temperatures in an air atmosphere improved the aluminium-glass/epoxy composite fracture toughness as measured via mode I experiments. For AgNW concentrations of 1 and 3 g/m2 deposited via a single-stage process and annealed at 375 °C, the initiation fracture toughness of the aluminium-glass/epoxy composite improved by 86% and 157%, respectively, relative to the baseline composite without AgNWs. The corresponding steady-state fracture toughness of these nano-modified fibre metal laminates (FMLs) were at least seven times greater than the baseline composite. The FML variant in which AgNWs were deposited at a concentration of 3 g/m2 through a two-stage process followed by annealing at 375 °C and 300 °C, respectively after each deposition, achieved the highest steady-state fracture toughness of all nano-modified composites—a fracture toughness value that was 13 times greater than the baseline composite. Intrinsic and extrinsic toughening mechanisms dictated by the morphology of the silver nano-architectures were found to be responsible for the improved initiation and steady-state fracture toughness in nano-modified FMLs

Thermal degradation and flame spread characteristics of epoxy polymer composites incorporating mycelium

Abstract Although bioderived flame retardants are environmentally sustainable and less toxic, their impact on the thermal stability and flammability of polymers remains poorly understood. In this study, we assessed the influence of mycelium on the thermal stability and flame spread characteristics of epoxy through thermogravimetric analysis, Fourier transform infrared spectroscopy, the UL94 flammability test, and scanning electron microscopy. We observed a decrease in the maximum mass loss rate temperature when mycelium was incorporated into epoxy, indicating an earlier onset of thermal degradation. The inclusion of mycelium increased char yields above 418 °C due to mycelium’s inherent char-forming ability. However, mycelium did not alter the thermal degradation pathway of epoxy. Furthermore, according to the UL94 test results, the incorporation of mycelium reduced the flame spread rate compared to that of neat epoxy. These findings contribute to our understanding of the interaction between bioderived flame retardants and polymers paving the way for the development of more sustainable fireproofing materials

Evaluating the heat resistance of thermal insulated sandwich composites subjected to a turbulent fire

The fire structural response of sandwich composite laminates incorporating bio-derived constituents subjected to a turbulent flaming fire was investigated. Fire structural tests were conducted on thermal insulated sandwich composites incorporating a thin surface-bonded non-woven glass fibre tissue impregnated with char-forming fire retardant, ammonium polyphosphate. The sandwich composite laminates were loaded in compression at 10%, 15% or 20% of the ultimate compressive strength while simultaneously subjected to turbulent flames imposing an incident heat flux of 35 kW/m2. Generally, the failure time increased with the reduced applied compressive load. The thermal insulated sandwich composite laminates had considerably improved fire resistance in comparison to their unmodified counterparts. The unmodified composites failed 96 s earlier than the thermal insulated specimens when the compression load was 10% of the ultimate compressive strength. The presence of ammonium polyphosphate at the heat-exposed surface promoted the formation of a consolidated char layer, which slowed down heat conduction into composite laminate substrate. The fire reaction parameters measured via the cone calorimeter provided insights into the thermal response hence fire structural survivability of sandwich composite laminates