Fire Retardancy Of Polymers Research Articles

Simulation of fatty acid adsorption at the magnesia surface

In this study, wet surface modification converted the hydrophilic magnesia (MgO) surface to a hydrophobic surface, which is crucial for magnesia additives in polymer fire retardants, inks, cosmetics and paint and paper materials and in the flotation of magnesia. For this reason, the adsorption of fatty acids at the magnesia surface in the wet surface modification process was examined by molecular dynamics simulations. The sessile drop contact angles at the magnesia surface with monolayer adsorption of lauric acid (C12H24O2), oleic acid (C18H34O2) and stearic acid (C18H36O2) and the interfacial water structures at the magnesia surface with sub-monolayer, monolayer and bilayer fatty acid adsorption were analyzed and compared with the experimental results. The sessile drop contact angle at the magnesia surface increased as a function of the carbon (C) chain length with fatty acid adsorption and agreed with the experimental results. All the fatty acids were adsorbed at the magnesia surface, and the interaction energy results agreed with the adsorption phenomenon. A hydrophobic surface was established in monolayer stearic acid adsorption and was transformed into a hydrophilic surface in stearic acid bilayer adsorption.

Flame Resistant Silicone-Containing Coating Materials

The flame resistance of applied coating materials affects the safety of innovative technological solutions. Silicone-containing polymeric materials are one of the most economical solutions in the field of coatings due to the effect of the unique combination of very good thermal, resistance, and surface properties. The rich chemistry of silicon compounds, which results in their very good thermal stability, allows their use as flame-resistant coating materials or as flame retardants in polymer composites. In this review, the flame resistance of PDMS systems based on their thermal degradation data, as well as possible paths of thermal degradation depending on external conditions including the effect of additives, flame resistance of hybrid silicone-containing coating materials and most important innovative applications of these materials, are reviewed. Very good results from the use of organic silicon compounds as fire retardants in polymers obtained by many research teams are one of the promising ways of overcoming the health, safety, and availability concerns of traditional halogenated fire retardants.

Instrumentation of UL‐94 test: understanding of mechanisms involved in fire retardancy of polymers

A quantitative approach of phenomena occurring in UL‐94 test setting up selected instrumentation was developed in this work. The instrumentation permits to measure the weight of droplets, the weight loss of the sample as well as the temperature gradients during the fire test. Three flame retardant formulations of PA6 exhibiting different modes of action (melamine cyanurate, melamine pyrophosphate, and guanidine sulfamate/melamine polyphosphate) were compared with the neat matrix and the corresponding formulations reinforced with 20 wt% glass fibers. It was shown that depending on the mode of action of the flame retardant, the heat propagation, the volatilization and the release of drops are significantly different with or without glass fibers. The measured parameters include the endothermic effect of MCA, the volatilization of guanidine sulfamate/melamine polyphosphate, the formation of an intumescent barrier with melamine pyrophosphate and the measurement ex situ of the thermal diffusivity of the drops. From this approach, the behavior of the samples and the influence of glass fibers are understood. Copyright © 2015 John Wiley & Sons, Ltd.

SEM/EDX: Advanced investigation of structured fire residues and residue formation

Heterogeneous, gradual or structured morphology of fire residues plays an important role in fire retardancy of polymers. A scanning electron microscope with an attached energy dispersive X-ray spectrometer (SEM/EDX) is highlighted as a powerful tool for the advanced characterization of such complex fire residues, since it offers high resolution in combination with both good depth of field and analysis of chemical composition. Two examples are presented: First, comprehensive SEM/EDX investigation on a complex structured fire residue of glass fibre reinforced polyamide 6,6 (PA 66-GF) flame retarded by diethylaluminium phosphinate, melamine polyphosphate and some zinc borate. A multilayered surface crust (thickness ∼ 24 μm) covers a rather hollow area stabilized by GF glued together. The resulting efficient thermal insulation results in self-extinguishing before pyrolysis is completed, even under forced-flaming combustion. Second, sophisticated, quasi online SEM/EDX imaging of the formation of residual protection layer in layered silicate epoxy resin nanocomposites (LSEC). Burning specimens were quenched in liquid nitrogen for subsequent analyses. Different zones were distinguished in the condensed phase characterized by distinct processes such as melting and ablation of organic material, as well as agglomeration, depletion, exfoliation and reorientation of the LS.

Electrospun nanofiber mats coating—new route to flame retardancy

A novel route toward halogen‐free fire retardancy of polymers through innovative surface coating is described. Nanofiber mats based on polyimide are deposited on PA66 through electrospinning. Scanning electron microscopy is used to characterize the nanofibers. Cone calorimeter tests were performed to evaluate the fire performance. Because of their low thermal conductivity, electrospun nanofiber mats act not only as sacrificial layers but also as a protective surface that delays ignition. The effect is influenced by the fiber diameters and the imidization. Copyright © 2011 John Wiley & Sons, Ltd.

Clays basal spacings effect on fire retardancy of polymers by TG/DTA

In this study, poly (ethylene-co-butyl acrylate, EBA-30) samples containing an intumescent formulation of ammonium polyphosphate and pentaerythritol and clays of different basal spacings had their flame retardant properties evaluated by thermogravimetric analysis, differential thermal analysis, and heating microscopy. Samples without polymeric matrix were also analyzed to observe possible interactions between the clays and the intumescent formulation. Thermal Analyses revealed that the basal spacings of the clays strongly influence their synergistic effect with the intumescent formulation studied.

Weathering resistance of halogen-free flame retardance in thermoplastics

The influence of weathering on the fire retardancy of polymers is investigated by means of a cone calorimeter test, before and after artificial weathering. The surface degradation was monitored using different techniques (ATR–FTIR, microscopy, colour measurement). Different kinds of polymeric materials were chosen, all as they are used in practice: polycarbonate (PC) blends, polyamide (PA) and polypropylene (PP) flame-retarded with arylphosphate, melamine cyanurate (MC) and intumescent formulation based on ammonium polyphosphate (APP), respectively. All samples show material degradation at the surface due to weathering. No significant weathering influence occurs on the flame retardancy when it is a bulk property, as was observed for aryl phosphates in PC blends and MC in PA. When the fire retardancy is dominated by a surface mechanism, dependence on the duration of weathering is detected: for intumescent formulations based on ammonium APP in PP, a worsening in the formation of the intumescent network was observed.

Fire retardancy of polymers: challenges and new concepts

The rapidly growing polymer market increases the risk of fire. The competition for reducing the costs and the activities for increasing the recyclability are advantageous from many aspects but promote the use of cheap and flammable polymers. The relative amount of the types of fire retardants (FRs) used in polymers is changing. The halogen containing compounds initiate corrosion, furthermore, some of them proved to be harmful to the environment and human health. Therefore the new European regulations promote the substitution of some conventional flame retardants by environmental-friendly ones. Reactive processing methods bond the additives to the polymer chains thus provide solution against their release to the environment, which is critical especially for some potential pseudohormones. Beyond the increasing importance of reactive methods the nano-concept is the most widely investigated novel approach to fire retardancy. Promising is the low environmental impact of nanofillers and influence on the macromolecular arrangement owing to their high surface area (reducing the heat distortion and melt dripping at high temperature). However, their fire retardancy performance should be enhanced, which requires better understanding of the mechanism of their action. It has to be clarified what is the relative role of their catalytic and physical action. The importance of the geometric dimensions, quality of dispersion and the potential synergism between different types should be clarified as well. Furthermore, the undesirable by-effect of removing stabilizers from the polymer matrix through their high surface area has to be eliminated. Most recent concepts are the in situ formation of nanofillers (during extrusion of the polymers) and of FR-active interfaces or surfaces around inclusions. Advancement of these concepts require the development of new micro-scale fire modeling/testing methods. Based on the described research activities increasing use of reactive, halogen free solutions in combination with nanofillers of well designed interfaces are predicted. Economic approaches applying recycled polymer matrices, nanofillers and multifunctional additives will increase in the close future. A multifunctional flame retardant can be applied for example as adaptive interlayer in a multiphase systems facilitating good mechanical, transport or adhesive performance at ambient temperature and transforming to protective (heat and combustiblegas barrier) layer at the temperature of combustion.

Fire behaviour of polyamide 6/multiwall carbon nanotube nanocomposites

Nanocomposites of polyamide 6 with 5 wt.% multiwall carbon nanotubes are investigated to clarify their potential as regards the fire retardancy of polymers. The nanocomposites are investigated using SEM, electrical resistivity, and oscillatory shear rheology. The pyrolysis is characterized using thermal analysis. The fire behaviour is investigated with a cone calorimeter using different external heat fluxes, by means of the limiting oxygen index and the UL 94 classification. The fire residue is characterized using SEM. The comprehensive fire behaviour characterization not only allows the materials’ potential for implementation in different fire scenarios and fire tests to be assessed, but also provides detailed insight into the active mechanisms. The increased melt viscosity of the nanocomposites and the fibre-network character of the nanofiller are the dominant mechanisms influencing fire performance. The changes are found to be adjuvant with respect to forced flaming conditions in the cone calorimeter, but also deleterious in terms of flammability.

98/03282 Crystallization of a castable apatite glass-ceramics: Liao, Y. Shengwu Yixue Gongchengxue Zazhi, 1997, 14, (2), 105–107, 114. (In Chinese)

The use of organosilicon compounds as fire retardants in polymers is one of the promising ways to overcome health, safety, and availability concerns of traditional halogenated fire retardants. Several types of organosilicon compounds with different degrees of oxidation are currently available, including silanes, polysiloxanes, and polysilsesquioxanes, as well as structures containing heteroatoms in the main chain, such as polycarbosilane and polysilazanes. Dispersion of such compounds into organic polymers may affect the polymer behavior in case of fire by a condensed phase action, producing a ceramic thermally stable protecting phase during the early stage of combustion. This chapter reviews the use of organosilicon compounds as fire retardants in polymers, discussing present achievements and perspectives.

Press Release: Fire Retardancy of Polymers: The use of Intumescence

Press Release: Fire Retardancy of Polymers: The use of Intumescence

XPS study of an intumescent coating application to the ammonium polyphosphate/pentaerythritol fire-retardant system

Fire retardancy of polymers may be due to the formation of a protective surface coating, i.e. a swollen charred layer (intumescence). An intumescent coating resulting from thermal treatments of the association of ammonium polyphosphate (APP) and pentaerythritol (PER) is studied by X-ray photoelectron spectroscopy. The O 1s, P 2p, C 1s and N 1s spectra are discussed. In the formation of the intumescent material the presence is shown of nitrogen in pyrrole and pyridine type structures of aromatic phosphate esters. A degradation mechanism is suggested which involves a reaction with O 2 via the formation of carbonyl and carboxylic groups.

Performance and mechanisms of fire retardants in polymers—A review

The fundamental mechanisms by which fire retardant additives can interrupt the self-sustained combustion cycle of organic polymers are reviewed. Evaluation of fire retardant performance and methods used for mechanism assessment are discussed. Examples are given of recent mechanistic studies of halogen-based and intumescent systems indicating that some previous generalisations should be revised. It is shown that a deeper understanding of fire retardance mechanisms acquired through detailed thermal degradation studies is the only way to answer the ever increasing demand for polymeric materials characterised by minimised overall fire hazard.

Combustion and Fire Retardancy of Polymers

Combustion and Fire Retardancy of Polymers