Thermal Degradation and Fire Behavior of High Performance Polymers

Abstract

High performance and high temperature polymers are a class of polymeric materials exhibiting high thermal stability and their resistance to fire makes them valuable assets for many applications. Those applications include as typical examples high temperature gas separation membranes, automotive and aerospace industry as well as the construction industry. The high performance polymers have been synthesized since the early 1960s, and have developed rapidly over the past few decades. Most high performance polymers comprise a highly aromatic backbone, linear chains, and strong inter-chain interactions. This review deals mostly with commercial polymeric materials. Studies regarding their thermal behavior, degradation mechanism and their reaction to fire have been synthetically combined in order to bring out potential insight concerning the effect of the thermal decomposition and thermal behavior on the fire properties of those polymers.     

Fire‐Retardant and Thermally Insulating Phenolic‐Silica Aerogels

Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co‐polymerization and nanoscale phase separation of the phenol‐formaldehyde‐resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO₂ aerogel can resist a high‐temperature flame without disintegration and prevents the temperature on the non‐exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures.     

Comparative studies on fire-rated and standard gypsum wallboard

The long-term goal of this research is to improve the fire resistance of gypsum wallboard (GWB). GWB consists mainly of gypsum, i.e., calcium sulfate dihydrate, CaSO₄·2H₂O. In buildings, the chemical, mechanical, and thermal properties of GWB play an important role in delaying the spread of fire. To build a fire resistant GWB, it is very important to study the thermal, mechanical, physical, and chemical properties of regular GWB and various types of fire resistant wallboards available commercially in the market. Various fire resistant GWBs have been compared and contrasted with reference to a standard wallboard in this study. Regardless of the type of wallboard, the main component is gypsum. The fire resistance property is mainly attributed to the absorption of energy related with the loss of hydrate water going from the dihydrate (CaSO₄·2H₂O) form to the hemihydrate (CaSO₄·½H₂O) and from the hemihydrate to the anhydrous form (CaSO₄) in a second decomposition. The present paper is a comparative study of commercially available standard, fire-rated Type X, and fire-rated Type C GWBs. Type X wallboards are typically reinforced with non-combustible fibers so as to protect the integrity of the wallboard during thermal shrinkage, while the Type C wallboards are incorporated with more glass fibers and an additive, usually a form of vermiculite. These Type C wallboards have a shrinkage adjusting element that expands when exposed to elevated temperature. Differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and powder X-ray diffraction were used to characterize and compare the materials. Various properties, such as the heat flow, mass loss, dimensional changes, morphology, and crystalline structures of the GWBs were studied using these techniques.     

Modification chimique des polyalcadienes par les composes du type cx3poz2-I: Modification des polybutadienes-1,2 par le dichlorure de trichloromethylphosphonyle

The cupric chloride catalysed radical addition of trichloromethylphosphonyl dichloride (CCI₃POCI₂) (1) to 1,2-polybutadi6ne (M_n < 10,000) is described. The influences of various parameters (reaction temperature, reagent concentrations, catalyst concentration, nature and concentration of solvents, reaction time) on the yield have been examined. Polymers having dichloromethylphosphonyldichloride groups are obtained, but cyclization and cross-linking reactions compete with the addition of (1) to carbon-carbon double bonds. The fire resistance of these modified polybutadienes has been tested: the products are non-flammable and their use as fire proofing additives for polybutadiene is investigated.     

Synthesis,Crystal Structure,and Flame Retardance of 2-(3-Silatranyl-Propylamino)-4-(2,4-Dichlorophenyl)-5,5-Dimethyl-1,3,2-Dioxaphosphinane-2-Sulfide

Abstract

2-(3-Silatranylpropylamino)-4-(2,4-dichlorophenyl)-5,5-dimethyl-1,3,2-dioxa phosphinane-2-sulfide 4 was synthesized by a nucleophilic substitution reaction of 2-chloro-1,3,2-dioxaphosphinane-2-sulfide 2 with γ-aminopropylsilatrane 3, which was prepared by the cyclization reaction of triethanolamine and γ-aminopropyltriethoxysilane. The structure of the title compound was confirmed by IR, ¹H NMR, ³¹P NMR, EI-MS, and elemental analysis as well as by single crystal X-ray diffraction and its thermal properties were studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). Thermal analysis and preliminary fire retardance testing suggest that compound 4 should function as a good flame retardant.     

Synthesis of Acid-Resistant P-Quinone Monoketals and Thermally Stable 4,4-Dialkoxycyclohexa-2,5-Dien-1-OLS

Preparation and high resistance to acid hydrolysis of sterically hindered p-quinone monoketals 1a, 1b and 1c are described. Thermal stability of ketal alcohols 2a and 2b derived from 1a and 1c, respectively, is also mentioned.     

The Future of Flame Retardant Polymers – Unmet Needs and Likely New Approaches

ABSTRACT

Thermoplastic and thermoset polymers in use today have fire risk and fire hazard associated with them that is not always well known to the public or material scientists. Recent events in the United Kingdom and California show that, if not considered carefully, use of flammable materials can result in catastrophic losses of both life and property. Further, current understanding has shown that simply adding flame retardant chemicals to polymers to address fire hazard and risk is not sufficient, as there is an increased demand from consumers, government, and industry for improved durability, recyclability, fire safety, and reduced environmental impact. These new requirements are beginning to change flame retardant chemistry for polymers, which has been mostly unchanged for the past 50 years. Existing flame retardant chemical technology will be briefly reviewed to show what is available today, followed by a discussion of potential future flame retardant approaches. Future possibilities such as polymeric, reactive, inorganic, and transition metal chemistries will be surveyed and discussed, with emphasis on what is not fully understood or validated for commercial use or future research and development investment. Current unmet fire safety needs of polymers, based upon current information and technological trends, will also be discussed.     

High heat applications for ELIX® 300 modified rigid PVC in injection moulding,extrusion, calandering and blow moulding

ELIX^® 300 resins - impact modified styrene maleic anhydride terpolymers - allow for improvements in practical heat distortion resistance of PVC to temperatures over 100°C whilst adding impact resistance and maintaining its chemical resistance and fire retardancy. This paper describes what is meant by practical heat distortion resistance and how the semi-compatible nature of PVC/ELIX^® 300 blends helps to meet higher in-use temperature requirements. Main properties of PVC/ELIX^® 300 blends as a function of concentration and K-value of the PVC, considerations concerning formulations and the influence of compounding techniques on morphology and properties are discussed and some practical application examples are given.     

Cross-linking of oligoalumosiloxanes

It is shown that cross-linking of the oligomer Al{[OSi(CH₃)₂]₂₉₀OH}₃ involves terminal hydroxyl groups and is accelerated by the introduction of metalloporphyrazines into the oligomer. The reaction is described by the first-order kinetic equation for irreversible reactions. The effective cross-linking rate constants at 180, 190, and 200°C and the activation energies of the reaction are calculated. A protective material with vulcanized coating based on oligoalumosiloxane has high fire resistance.     

A new approach on improving the fire resistance of polyamide 11 by incorporating sulfur‐based flame retardant

In this work, a novel sulfur‐based flame retardant (SA‐M) was synthesized by the self‐assembly of melamine and sulfamic acid. The chemical structure of SA‐M was fully characterized. SA‐M, in company with Al₂O₃, was then introduced into polyamide 11 (PA 11) by melt compounding in order to improve the fire resistance of the polymer substrate. The observation by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) indicated the well dispersion of SA‐M in PA 11 matrix. The fire performance of PA 11 composites was evaluated by limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimeter tests, respectively. The results showed that the presence of 17.5% SA‐M and 2.5% Al₂O₃ increased the LOI value from 22.4% to 30.9%, upgraded the UL‐94 rating from no rating to V‐0, significantly eliminated the melt dripping, and decreased the peak heat release rate from 1024 to 603 kW/m². The thermal behaviors were investigated by thermogravimeric analysis (TGA) and TGA‐Fourier transform infrared spectroscopy (FTIR). It was suggested that SA‐M took effects mainly in gas phase by diluting the combustible fuel, leading to the improvement of the fire resistance of PA 11.     

“I am the Poison Dripping Dragon”: Iguanas and Their Symbolism in the Alchemical and Occult Paintings of David Teniers the Younger

Abstract

“I am the poison-dripping dragon, who is everywhere and can be cheaply had … my water and fire destroy and put together; from my body you may extract the green lion and the red … From my snout there comes a spreading poison that has brought death to many …By the philosophers I am named Mercurius … I am the old dragon found everywhere on the globe of the earth … I am the carbuncle of the sun, the most noble purified earth through which you may change iron, tin, and lead into gold …”

“The Spirit Mercurius”

Theatrum Chemicum, 1659     

Improving the gas barrier,mechanical and thermal properties of poly(vinyl alcohol) with molybdenum disulfide nanosheets

New multifunctional materials with both high structural and gas barrier performances are important for a range of applications. Herein we present a one‐step mechanochemical process to prepare molybdenum disulfide (MoS₂) nanosheets with hydroxy functional groups that can simultaneously improve mechanical strength, thermal conductivity, and gas permittivity of a polymer composite. By homogeneously incorporating these functionalized MoS₂ nanosheets at low loading of less than 1 vol %, a poly(vinyl alcohol) (PVA) polymer exhibits elongation at break of 154%, toughness of 82 MJ/m³, and in‐plane thermal conductivity of 2.31 W/m K. Furthermore, this composite exhibits significant gas barrier performance, reducing the permeability of helium by 95%. Under fire condition, the MoS₂ nanosheets form thermally stable char, thus enhancing the material's resistance to fire. Hydrogen bonding has been identified as the main interaction mechanism between the nanofillers and the polymer matrix. The present results suggest that the PVA composite reinforced with 2D layered nanomaterial offers great potentials in packaging and fire retardant applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 406–414     

Organic conductors with BiIII and SbIII chloride-based anions

New layered organic conductors, (BEDT-TTF)4(BiCl5)1 7 (1), δ-(BEDT-TTF)2BiCl5 (2), and δ-(BEDT-TTF)6Sb3Cl12 (3), were obtained (BEDT-TTF is bis(ethylenedithio)tetrathia-fulvalene). In the crystal structures of 1—3, organic radical cation layers are composed of di-merized stacks. The dimers are formed by BEDT-TTF radical cations rotated through angle ω relative to each other, which results in twisted stacks, giving rise to so-called twisted overlap mode in the layers. These layers alternate with non-conductive inorganic layers consisting of chains in which the Cl, Bi, and Sb sites are partially occupied. This indicates discontinuities in the chains of anions, and, apparently, the absence of continuous polymer chains in the crystal structure. According to measurements of the temperature dependence of the electrical resistance, the compounds are semiconductors.

     

Modelling the role of dual specificity phosphatases in herceptin resistant breast cancer cell lines

BackgroundBreast cancer remains the most lethal type of cancer for women. A significant proportion of breast cancer cases are characterised by overexpression of the human epidermal growth factor receptor 2 protein (HER2). These cancers are commonly treated by Herceptin (Trastuzumab), but resistance to drug treatment frequently develops in tumour cells. Dual-specificity phosphatases (DUSPs) are thought to play a role in the mechanism of resistance, since some of them were reported to be overexpressed in tumours resistant to Herceptin.ResultsWe used a systems biology approach to investigate how DUSP overexpression could favour cell proliferation and to predict how this mechanism could be reversed by targeted inhibition of selected DUSPs. We measured the expression of 20 DUSP genes in two breast cancer cell lines following long-term (6 months) exposure to Herceptin, after confirming that these cells had become resistant to the drug. We constructed several Boolean models including specific substrates of each DUSP, and showed that our models correctly account for resistance when overexpressed DUSPs were kept activated. We then simulated inhibition of both individual and combinations of DUSPs, and determined conditions under which the resistance could be reversed.ConclusionsThese results show how a combination of experimental analysis and modelling help to understand cell survival mechanisms in breast cancer tumours, and crucially enable us to generate testable predictions potentially leading to new treatments of resistant tumours.     

Influence of water content on failure of phenolic composites in fire

This paper evaluates the structural performance of flame resistant phenolic matrix composites exposed to fire. Experimental fire tests were performed on a glass-phenolic composite under combined static loading and one-sided radiant heating. The reduction to the tension and compression failure strengths of the phenolic composite was measured in these tests for heat flux conditions ranging from 10 kW/m² (∼225 °C) to 75 kW/m² (∼700 °C). It was discovered that the failure strengths of the phenolic composite decreased rapidly in the event of fire, particularly under compressive loading when failure occurred more rapidly than under tensile loading. The phenolic composite, despite having high flame resistance, loses strength more rapidly and fails sooner than a more flammable vinyl ester composite. The study shows that greater flammability resistance does not necessarily result in better structural performance in fire. The poor structural performance of the phenolic composite was due to explosive delamination damage and cracking caused by vaporisation of water in the matrix phase. It is shown that removing water from phenolic composites by natural or artificial ageing reduces the incidence of delamination cracking and thereby improves the materials' structural performance in fire. It is concluded that phenolic composites do not provide good structural performance in fire, even though they have low flame and smoke properties. However, reducing the water content in the matrix phase below about 10% can greatly improve the structural performance of phenolic composites during fire.     

New pivot for investigating flame‐retarding mechanism: Quantitative analysis of zinc phosphate doped aliphatic waterborne polyurethane‐based intumescent coatings for flame‐retarding plywood

The quantitative analysis of zinc phosphate (ZnP) on the flame resistance of intumescent flame retardant coatings (IFRCs) is presented including cone calorimeter (CC) and pyrolysis kinetics, using aliphatic waterborne polyurethane (AWP) as the coating binder. The CC results show that an appropriate dosage (2 wt%) of ZnP in the AWP‐based coating constitutes an improved flame resistance, evidenced by the fire performance index increased from 0.41 to 0.71 seconds m² kW^?1, as well as the reduced fire growth index. The characterization analysis determines the dehydrated ZnP facilitates the formed amorphous char‐residue with a heat‐sink effect, leading to an increase in heat absorption, which climbs from the 253.00to 351.30 J·g^?1. Besides, the pyrolysis kinetics verifies that the 3D Jander model (n = 2) mainly governs the whole pyrolysis process of pure coatings by the modified Coats‐Redfern integral method. The ZnP‐containing coating exerts an improved E_α corresponding to 95–200°C, which climbs from 24.96 to 35.80 kJ mol^?1, leading to the formation of a continuous and compact char layer. It explores an effective quantitative analysis of the flame resistance of organic–inorganic hybrid IFRCs, deepening the flame‐retarding mechanism.     

Etude ATD-ATG du polyethylene ignifuge par l’hydroxyde de magnesium

Fire resistance of polyethylene is realized by magnesium hydroxide which is distinguished from halogenated fire-proofing agents by its lower cost and its non toxicity. Magnesium hydroxide decomposed by an endothermic reaction with liberation of water, contributing to fire proofing. The sample used (Kisuma 5A-N^*) is constituted from a powder (0.6–0.8 micrometre) its surface is treated by plastic material in order to ameliorate its compatibility. We studied the thermal decomposition by DTA and TG, of mixtures constituted by polyethylene and magnesium hydroxide. A sudden decomposition began at 385°C for pure polyethylene and decomposition took place at 429°C for the mixture polyethylene-Kisuma (50–50). Incorporation of magnesium hydroxide in polyethylene increases fire resistance.     

“In vitro” activity of Melaleuca cajuputi against mycobacterial species

Abstract

The increasing incidence of resistance in tuberculosis and in atypical mycobacterial infections has prompted the search for alternative agents. We explored the antimycobacterial activity of Melaleuca cajuputi essential oil against tubercular and non tubercular mycobacterials isolates. The good activity observed towards M. cajuputi indicated that this essential oil might represent a promising antimicrobial agents, particularly in the management of microbial resistance.     

Polysulfide Polymers: Synthesis,Blending, Nanocomposites,and Applications

Abstract

Polysulfide polymers as an important class of polymers are used in different applications as sealants, adhesives, etc. They are usually synthesized by reaction of disodium polysulfides with dihalo compounds to yield liquid or solid polymers. Their most important advantages are excellent adhesion to different surfaces, creation of no defect in sealant under stress and pressure, resistance against to fuels and solvents, very low gas and steam permeability, and high resistance to ozone and UV. This article aims to review methods of synthesis, properties, and applications of polysulfide polymers. Also, polysulfide-based nanocomposites and blends are also briefly discussed.     

Moisture Resistance,Thermal Stability and Fire Behavior of Unsaturated Polyester Resin Modified with L-histidinium Dihydrogen Phosphate-Phosphoric Acid

In this paper, the fire behavior of unsaturated polyester resin (UP) modified with L-histidinium dihydrogen phosphate-phosphoric acid (LHP), being a novel intumescent fire retardant (IFR), was investigated. Thermal and thermomechanical properties of the UP with different amounts of LHP (from 10 to 30 wt. %) were determined by thermogravimetric analysis (TG) as well as dynamic mechanical thermal analysis (DMTA). Reaction to small flames was studied by horizontal burning (HB) test, while fire behavior and smoke emission were investigated with the cone calorimeter (CC) and smoke density chamber. Further, the analysis of volatile products was conducted (TGA/FT-IR). It was observed that the addition of LHP resulted in the formation of carbonaceous char inhibiting the thermal decomposition, burning rate and smoke emission. The most promising results were obtained for the UP containing 30 wt. % of LHP, for which the highest reduction in maximum values of heat release rate (200 kW/m²) and total smoke release (3535 m²/m²) compared to unmodified polymer (792 kW/m² and 6895 m²/m²) were recorded. However, some important disadvantage with respect to water resistance was observed.