Bio-Sourced Flame Retardants for Textiles: Where We Are and Where We Are Going.

After the period of halogenated compounds, the period of nano-structured systems, and that of phosphorus (and nitrogen)-based additives (still in progress), following the increasingly demanding circular economy concept, about ten years ago the textile flame retardant world started experiencing the design and exploitation of bio-sourced products. Indeed, since the demonstration of the potential of such bio(macro)molecules as whey proteins, milk proteins (i.e., caseins), and nucleic acids as effective flame retardants, both natural and synthetic fibers and fabrics can take advantage of the availability of several low-environmental impact/"green" compounds, often recovered from wastes or by-products, which contain all the elements that typically compose standard flame-retardant recipes. The so-treated textiles often exhibit flame-retardant features that are similar to those provided by conventional fireproof treatments. Further, the possibility of using the same deposition techniques already available in the textile industry makes these products very appealing, considering that the application methods usually do not require hazardous or toxic chemicals. This review aims to present an overview of the development of bio-sourced flame retardants, focusing attention on the latest research outcomes, and finally discussing some current challenging issues related to their efficient application, paving the way toward further future implementations.

Synergistic Effect between Piperazine Pyrophosphate and Melamine Polyphosphate in Flame Retardant Coatings for Structural Steel.

Piperazine pyrophosphate (PAPP) combined with melamine polyphosphate (MPP) was adopted to prepare a waterborne fire retardant intumescent coating (IC) for structural steel. Silicone acrylic emulsion was used as binder. In the 2-h torch test, PAPP/MPP-IC coating presented excellent fire resistance performance. The equilibrium temperature at the backside of the steel board decreased to 170 °C with protection of MPP/PAPP-IC, compared with 326 °C of APP/PER/MEL-IC. After 72-h water immersion, MPP/PAPP-IC could still provide sufficient thermal isolation, but APP/PER/MEL-IC failed the test. The water absorption of the MPP/PAPP coating was also reduced. The thermogravimetric analysis measured that the PAPP/MPP-IC had unique initial decomposition temperature of 296 °C and higher residue of 33.8 wt%, which demonstrated better thermal stability and fire retardancy in condensed phase. In addition, Scanning Electron Microscope (SEM) images illustrated that the structure of the carbon layer formed by MPP/PAPP-IC was dense, complete and consistent, indicating the improvement of mechanical strength and thermal isolation of the char. The synergistic effect between piperazine and phosphoric acid groups in MPP/PAPP contributed to the superior flame retardancy. Consequently, MPP/PAPP-IC was much more efficient than the traditional APP/PER/MEL-IC. This work provides a novel way for designing flame retardant coatings for structural steel with excellent comprehensive performance.

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.

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials.

Fireproof inorganic coatings based on sodium silicate solution with intumescent additions were prepared and tested to assess their ability to limit the negative effect of a fire. The intumescent materials were obtained by the alkali activation of waste glass powder (obtained by the grinding of recycled soda-lime culet) and slag (waste resulting from the metallurgical industry). The replacement of talc (used as filler in paint formulation) with the intumescent materials obtained by the alkaline activation of waste glass powder (WGP), determined an increase in the intumescence coefficient (up to 65%) and decreased the activation temperature of this process. To evaluate these coatings' abilities to prevent or delay the temperature increase in metal structures, the paints were applied on steel plates and tested in direct contact with the flame of a butane burner for 60 min. The coatings prevented the increase in the steel substrate temperature over one considered critical (500°C) for steel mechanical properties; the combination of two coatings, with different intumescence activation temperatures, correlated with the increase in the coating's thickness, sensibly reduced the rate of temperature increase (up to 75%) in the steel substrate.

Bioinspired Adenosine Triphosphate as an "All-In-One" Green Flame Retardant via Extremely Intumescent Char Formation.

The development of eco-friendly flame retardants is crucial due to the hazardous properties of most conventional flame retardants. Herein, adenosine triphosphate (ATP) is reported to be a highly efficient "all-in-one" green flame retardant as it consists of three essential groups, which lead to the formation of char with extreme intumescence, namely, three phosphate groups, providing an acid source; one ribose sugar, working as a char source; and one adenine, acting as a blowing agent. Polyurethane foam was used as a model flammable material to demonstrate the exceptional flame retardancy of ATP. The direct flammability tests have clearly shown that the ATP-coated polyurethane (PU) foam almost did not burn upon exposure to the torch flame. Importantly, ATP exhibits an extreme volume increase, whereas general phosphorus-based flame retardants show a negligible increase in volume. The PU foam coated with 30 wt % of ATP (PU-ATP 30 wt %) exhibits a significant reduction in the peak heat release rate (94.3%) with a significant increase in the ignition time, compared to bare PU. In addition, PU-ATP 30 wt % exhibits a high limiting oxygen index (LOI) value of 31% and HF-1 rating in the UL94 horizontal burning foamed material test. Additionally, we demonstrated that ATP's flame retardancy is sufficient for other types of matrices such as cotton, as confirmed from the results of the standardized ASTM D6413 test; cotton-ATP 30 wt % exhibits an LOI value of 32% and passes the vertical flame test. These results strongly suggest that ATP has great potential to be used as an "all-in-one" green flame retardant.

Synergistic Action of Montmorillonite with an Intumescent Formulation: The Impact of the Nature and the Strength of Acidic Sites on the Flame-Retardant Properties of Polypropylene Composites.

A raw montmorillonite (Mt) was submitted to different acidic activation times in order to investigate the influence of the strength and the nature (Brønsted and Lewis) of acidic sites on the synergistic action with an intumescent formulation (IF) composed of ammonium polyphosphate (APP) and pentaerythritol (PER) when incorporated into a polypropylene (PP) matrix. The acidity of the Mt samples was quantified by ammonia temperature-programmed desorption (TPD-NH3) and Fourier transform infrared spectroscopy (FTIR) with pyridine adsorption. The mineral clays were also characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), nitrogen adsorption analysis and particle size distribution. Thermogravimetric analysis (TGA), limit oxygen index (LOI) and UL-94 were performed to evaluate the flame-retardant properties and the thermal stability. The TGA results show that the final residue increased 2 to 3 fold in comparison to the values predicted theoretically. The flammability properties achieved a maximum for the system containing an excess of moderate-strength Brønsted sites relative to the Lewis ones, reaching 38% in the LOI test. This result suggests that the presence of these Brønsted acidic sites is important, as they take part in the esterification reaction between APP and PER which gives rise to the char formation. The FTIR-Pyr adsorption and flammability results indicate that both the nature and strength of the acidic sites influence the flame-retardant properties.

Base Promoted Intumescence of Phenols.

: The intumescent process of sodium (substituted) phenolates has been studied. The generation of hydrogen radical via a homolytic cleavage of the Ar-H bond and the subsequent hydroarylation of phenolates to cyclohexadienes along with cyclization and elimination reactions of cyclohexadienes are critical steps in the base promoted intumescence of phenols. The substituents show great influence on the intumescence of phenolates. Phenolates substituted with a weak electron donating group enable intumescence while those with an electron withdrawing group or strong electron donating group suppresses intumescence. This distinction can be justified by both electronic and steric effects of substituents on the generation of hydrogen radical and the degree of hydroarylation.

Vertebromedullary Topography of the Red-Rumped Agouti (Dasyprocta leporina Linnaeus, 1758).

The agouti is a wild rodent located almost throughout the Brazilian territory, with great scientific importance and high reproductive potential when farmed. In the clinical routine, clinical and surgical procedures are performed on the nervous system of these animals, such as epidural anesthesia and cerebrospinal fluid (CSF) collection; however, data available are limited in literature on the main points of these procedures in this species. In this aspect, the objective was to describe the vertebromedullary topography of the agouti in order to identify and quantify it, with the intention of expanding the information regarding the clinical-surgical procedures in this system. Ten animals were incised longitudinally in the dorsal median line, removing the skin, the musculature, and dorsal fascia of the vertebral column; then, removed the vertebral arches and consequent exposure of the spinal cord and meninges. The morphometry of the animals was done by obtaining the total length, body length, and crown-rump length, as well as the total length of the spinal cord and its segments. The cervical intumescence in the agouti is located between C4-T1 and measures 2.45 cm. The lumbar intumescence is between L5-L7 and is 2.52 cm long. The cauda equina arises from S2 and the filum terminale from S3. As for the medullary cone, it is located between L7-S1 and is 2.52 cm long. The suggested localization for epidural anesthesia or CSF puncture for laboratory tests in agoutis is the lumbosacral space, with the insertion of the needle to be carried out at angle of 90° in the sphinx position. Anat Rec, 303:1472-1477, 2020. © 2019 American Association for Anatomy.

Halogen-Free Flame-Retardant Compounds. Thermal Decomposition and Flammability Behavior for Alternative Polyethylene Grades.

The effect of six halogen-free flame retardant (FR) formulations was investigated on the thermal stability of two low-density polyethylenes (LDPE) and one linear low-density polyethylene (LLDPE), by means of thermogravimetric analysis (TGA) under nitrogen and air atmosphere. The relative data were combined with flammability properties and the overall performance of the FRs was correlated with the type of branching in the polyethylene grades and to their processing behavior. The thermal degradation kinetics was further determined based on the Kissinger and Coats-Redfern methods. In terms of flammability, the addition of a triazine derivative and ammonium polyphosphate at a loading of 35 wt. %. was found to be the most efficient, leading to UL 94 V0 ranking in the case of the LDPE grade produced in an autoclave reactor.

The Efficiency of Biobased Carbonization Agent and Intumescent Flame Retardant on Flame Retardancy of Biopolymer Composites and Investigation of their Melt-Spinnability.

The objective of this study is to assess the efficiency of biobased carbonization agent in intumescent formulations (IFRs) to examine the flame retardant properties of polylactic acid (PLA) composites and to investigate their melt-spinnability. We used phosphorous-based halogen free flame retardant (FR) and kraft lignin (KL) as bio-based carbonization agent. After melt compounding and molding into sheets by hot pressing various fire related characteristics of IFR composites were inspected and were characterized by different characterization methods. It was fascinating to discover that the introduction of 5-20 wt% FR increased the limiting oxygen index (LOI) of PLA composites from 20.1% to 23.2-33.5%. The addition of KL with content of 3-5 wt% further increased the LOI up to 36.6-37.8% and also endowed PLA/FR/KL composites with improved anti-dripping properties. Cone calorimetry revealed a 50% reduction in the peak heat release rate of the IFR composites in comparison to 100% PLA and confirmed the development of an intumescent char structure containing residue up to 40%. For comparative study, IFR composites containing pentaerythritol (PER) as a carbonization agent were also prepared and their FR properties were compared. IFR composites were melt spun and mechanical properties of multifilament yarns were tested. The analysis of char residues by energy dispersive X-ray spectrometry (EDS) and SEM images confirmed that PLA/FR/KL composites developed a thicker and more homogeneous char layer with better flame retardant properties confirming that the fire properties of PLA can be enhanced by using KL as a carbonization agent.

Topography of the medullary cone of the feline night monkey: Clinical implications in epidural anesthesia / Topografia do cone medular do macaco-da-noite: auxiliando a abordagem peridural

Feline night monkey (Aotus azarae infulatus) is an arboreal primate that sleeps during the day hidden among branches of trees, leaving its hideout after nightfall. Little is known about the morphology of these animals, which leads to some difficulty in clinical and surgical approaches, as there has been substantial growth in the veterinarian's role in maintaining the health and well-being of wildlife. Thus, we sought to investigate the topography and morphometry of the medullary cone, a small portion of the nervous system of the feline night monkey, which is of paramount importance in approaches for epidural anesthesia. Specimens from five young females were used, each with eight lumbar vertebrae, three sacral vertebrae, and a medullary cone with an average length of 7.5 cm, located between L5 and S3. Based on this finding, we suggest that a probable site for the application of epidural anesthesia is the space between S3 and Cc1.

O macaco-da-noite (Aotus azarae infulatus) é um animal arborícola que dorme durante o dia escondido entre os ramos, saindo do esconderijo após o anoitecer. Pouco se sabe sobre a morfologia destes animais, o que gera certa dificuldade nas abordagens clínico-cirúrgicas, uma vez que cresce substancialmente o papel do médico veterinário nas questões de saúde e bem-estar de animais selvagens. Visando contribuir com esses profissionais, buscou-se investigar a topografia e morfometria de uma pequena porção do sistema nervoso do macaco-da-noite, o cone medular, que é de suma importância nas abordagens quanto à anestesia peridural. Foram utilizados cinco espécimes fêmeas, jovens, de macaco-da-noite, que apresentavam oito vértebras lombares e três vértebras sacrais, e cone medular possuindo em média de 7,5 cm de comprimento, localizando-se entre L5 e S3. Este achado nos leva a sugerir como sítio provável para a aplicação de anestesia epidural, o espaço entre S3 e Cc1.

Topography of the medullary cone of the feline night monkey: Clinical implications in epidural anesthesia / Topografia do cone medular do macaco-da-noite: auxiliando a abordagem peridural

Feline night monkey (Aotus azarae infulatus) is an arboreal primate that sleeps during the day hidden among branches of trees, leaving its hideout after nightfall. Little is known about the morphology of these animals, which leads to some difficulty in clinical and surgical approaches, as there has been substantial growth in the veterinarian’s role in maintaining the health and well-being of wildlife. Thus, we sought to investigate the topography and morphometry of the medullary cone, a small portion of the nervous system of the feline night monkey, which is of paramount importance in approaches for epidural anesthesia. Specimens from five young females were used, each with eight lumbar vertebrae, three sacral vertebrae, and a medullary cone with an average length of 7.5 cm, located between L5 and S3. Based on this finding, we suggest that a probable site for the application of epidural anesthesia is the space between S3 and Cc1.

O macaco-da-noite (Aotus azarae infulatus) é um animal arborícola que dorme durante o dia escondido entre os ramos, saindo do esconderijo após o anoitecer. Pouco se sabe sobre a morfologia destes animais, o que gera certa dificuldade nas abordagens clínico-cirúrgicas, uma vez que cresce substancialmente o papel do médico veterinário nas questões de saúde e bem-estar de animais selvagens. Visando contribuir com esses profissionais, buscou-se investigar a topografia e morfometria de uma pequena porção do sistema nervoso do macaco-da-noite, o cone medular, que é de suma importância nas abordagens quanto à anestesia peridural. Foram utilizados cinco espécimes fêmeas, jovens, de macaco-da-noite, que apresentavam oito vértebras lombares e três vértebras sacrais, e cone medular possuindo em média de 7,5 cm de comprimento, localizando-se entre L5 e S3. Este achado nos leva a sugerir como sítio provável para a aplicação de anestesia epidural, o espaço entre S3 e Cc1.

Key Role of Reinforcing Structures in the Flame Retardant Performance of Self-Reinforced Polypropylene Composites.

The flame retardant synergism between highly stretched polymer fibres and intumescent flame retardant systems was investigated in self-reinforced polypropylene composites. It was found that the structure of reinforcement, such as degree of molecular orientation, fibre alignment and weave type, has a particular effect on the fire performance of the intumescent system. As little as 7.2 wt % additive content, one third of the amount needed in non-reinforced polypropylene matrix, was sufficient to reach a UL-94 V-0 rating. The best result was found in self-reinforced polypropylene composites reinforced with unidirectional fibres. In addition to the fire retardant performance, the mechanical properties were also evaluated. The maximum was found at optimal consolidation temperature, while the flame retardant additive in the matrix did not influence the mechanical performance up to the investigated 13 wt % concentration.

All-Inorganic Intumescent Nanocoating Containing Montmorillonite Nanoplatelets in Ammonium Polyphosphate Matrix Capable of Preventing Cotton Ignition.

In the present manuscript a new concept of completely inorganic intumescent flame retardant nanocoating comprised of sodium montmorillonite nanoplatelets embedded in an ammonium polyphosphate matrix has been investigated using cotton as model substrate. The coating, deposited by multistep adsorption from diluted water-based suspensions/solutions, homogenously cover each cotton fibers with average thicknesses below 50 nm and add-on up to 5% in weight. Combustion characterization evidences the interesting properties: indeed, the so-treated fabrics reached self-extinguishing during horizontal flame spread tests. Furthermore, when the coating add-on reaches 5%, no ignition has been observed during cone calorimetry tests under 35 kW/m² heat flux. Residue analyses pointed out the formation of an expanded all-inorganic coating capable of greatly improving char formation by exerting barrier function towards volatile release and heat transfer.

Important Parameter Groups in Thermal Protection of Polymers.

The problem of thermal protection is explored for two idiosyncratic reactive systems, namely a sacrificial heat-sink material and an intumescent system where a dynamically evolving insulation layer is produced from an initially thin coating. Relatively simple mathematical models of both systems are proposed that encompass the important physical characteristics of each situation and these models are analysed using a mixture of numerical and analytical techniques. Important dimensionless parameter groups are identified and domains of parameter space where thermal performance is particularly good- or particularly bad- are identified.

Phosphorus-based Flame Retardancy Mechanisms-Old Hat or a Starting Point for Future Development?

Different kinds of additive and reactive flame retardants containing phosphorus are increasingly successful as halogen-free alternatives for various polymeric materials and applications. Phosphorus can act in the condensed phase by enhancing charring, yielding intumescence, or through inorganic glass formation; and in the gas phase through flame inhibition. Occurrence and efficiency depend, not only on the flame retardant itself, but also on its interaction with pyrolysing polymeric material and additives. Flame retardancy is sensitive to modification of the flame retardant, the use of synergists/adjuvants, and changes to the polymeric material. A detailed understanding facilitates the launch of tailored and targeted development.