Thermal properties and flammability of nanocomposites based on diene rubbers and naturally occurring and activated halloysite nanotubes

This article presents a procedure of the activation of halloysite and a method of the synthesis of nucleus-sheath type filler. The effects of the nanoadditives obtained on the thermal properties, flammabilities and fire hazards of peroxide and sulfur vulcanizates of NBR and SBR rubbers, are discussed. Based on the test results obtained by derivatography, oxygen index, FAA micro-calorimeter and cone calorimeter, the thermal stability, flammability, and fire hazard of the nanocomposites investigated were determined. The results obtained were interpreted from the point of view of the chemical structure of the diene elastomers investigated, their spatial network structure, and the method of halloysite modification.     

Thermal stability and flammability of nanocomposites made of diene rubbers and modified halloysite nanotubes

This paper presents a method of modification of halloysite with the use of aqueous solutions of halogens and an alcoholic solution of boric acid. The effect of modified nanoadditives on the thermal properties, flammability, and fire hazard of peroxide and sulfur vulcanizates of butadiene–acrylonitrile (NBR) and butadiene–styrene (SBR) rubbers was described and assessed. The test results obtained by spectrometric methods, oxygen index, and cone calorimeter were interpreted from the point of view of the chemical structure of the investigated diene elastomers and the particular method of halloysite modification. The analysis of values obtained by the method of cone calorimetry it confirms that most NBR and SBR vulcanizates filled with modified halloysite are more resistant to fire when compared with material without modification. In addition, the modified halloysite are crucial in making self-extinguishing elastomeric materials.     

Effect of halogenless flame retardants on the thermal properties, flammability, and fire hazard of cross-linked EVM/NBR rubber blends

This paper presents the results of investigating the thermal stability, flammability, and fire hazard of cross-linked EVM/NBR blends unfilled and filled with halogenless flame-retardant compounds such as melamine cyanurate or magnesium hydroxide. The thermal analysis of the blends was carried out in the atmosphere of air. The activation energy of the composite destruction was determined by two non-isothermal methods: Flynn–Wall–Ozawa’s and Kissinger’s methods. The flammability of the composites obtained was determined by the method of oxygen index and on the basis of their combustion in air. The fire hazard of the vulcanizates investigated was determined with the use of a cone calorimeter and on the basis of toxicometric parameters W _LC50SM. The test results have shown that the flame retardants used increase the thermal stability of the cross-linked blends and decrease their flammability, and thereby allow one to obtain self-extinguishing or non-flammable polymeric materials. The cross-linked EVM/NBR blends filled with these flame-retardant compounds are characterized by good mechanical properties and reduced fire hazard.     

Thermal properties of diene elastomers

The paper presents the results of investigating the effect of the macromolecule chemical structure and the spatial network structure of butadiene (BR), butadiene-styrene (SBR) and butadiene-acrylonitrile (NBR) rubbers on their thermal properties. The rubbers were cross-linked by the conventional method by means of dicumyl peroxide or sulfur as well as by the non-conventional way using iodoform (CH₃I). The rubber and their vulcanizates were assessed by the derivatographic method (under air) and by means of differential scanning calorimetry (DSC) under inert gas. The thermal cross-linking degree of the polydienes and the efficiency of the cross-linking processes, dependent on both the chemical structure of elastomer macromolecules and their spatial network structure were determined. The cross-linking of elastomers with iodoform changes the thermal properties of polymers, significantly increasing their glass transition temperature during both sample heating and cooling, which results from the increase in mutual interaction of macromolecules connected with their modification with iodine compounds.     

The thermal properties and the flammability of pigmented elastomeric materials

This paper presents thermal properties of organic pigments such as zinc phthalocyanine and chloroaluminum phthalocyanine that were synthesized according to the literature data. These pigments were characterized by means of elementary analysis and measurements of particle size. They were then incorporated into butadiene-styrene rubber and butadiene-acrylonitrile rubber. The elastomeric mixtures were cross-linked by two methods: using organic peroxide or sulfur. The effect of phthalocyanines on the thermal properties, flammability, and fire hazard of the pigmented polymeric materials obtained as well as on their mechanical properties and cross-linking degree was studied. It has been shown that the phthalocyanine pigments not only impart appropriate esthetic values to the final goods but also increase their thermal stability and considerably reduce the flammability and fire hazard of elastomers and even make possible materials that are self-extinguishing under air atmosphere. These pigments also have a beneficial influence on the degree of cross-linking of the elastomers investigated and their mechanical properties.     

Experimental investigation of thermal properties and fire behavior of carbon/epoxy laminate and its foam core sandwich composite

According to structural characteristics, composites are classified as laminated structure and sandwich structure. Carbon/epoxy laminate and foam core sandwich composite are the most commonly used laminate and sandwich structure material in the aircraft industry. The flammability of epoxy resins and foam core material is an inherent hazard. Many previous studies focused primarily on their mechanical properties, while the studies on the thermal and fire properties of carbon/epoxy laminate and its foam core sandwich composite have rarely conducted. Therefore, to characterize their thermal and fire properties, a comprehensive experimental investigation and theoretical analysis were carried out in this work using thermogravimetric analysis, cone calorimeter, vertical/horizontal burning tests, limiting oxygen index and scanning electron microscope tests. Several typical characteristic parameters were obtained and analyzed, such as pyrolysis temperature, heat release rate, mass loss, flaming spread rate and limiting oxygen index. These experimental data coupled with theoretical analysis can provide support for fire risk assessment and fire protection design in aircrafts. The carbon/epoxy laminate and foam core sandwich composite are both characterized as the thermally thick materials. The ignition models and mass loss rate models were obtained. Foam core material negatively affects most of the thermal and fire properties of sandwich composite, but the foam core sandwich composite has self-extinguishing behavior during horizontal burning tests, whose LOI is higher than that of carbon/epoxy laminate. Thus, an important conclusion was reached that the ignition position and flame spread direction have critical effect on the fire behavior of foam core material.

     

Flammability of diene rubbers

This paper presents the results of testing the flammability and fire hazard of butadiene (BR), butadiene-acrylonitrile (NBR) and butadiene- styrene (SBR) rubbers with the use of oxygen index test, ignition temperature measurement, cone calorimetry and inverse liquid chromatography. Toxicometric indices, RTFH _CO/CO2, W_LC50SM and the concentration of polycyclic aromatic hydrocarbons (PAH) have been determined. The results obtained have been interpreted from the point of view of the chemical constitution of the polymers tested.     

Effect oftrans-polyoctenamer on thermal stability of rubbers determined by thermal analysis

An effect of a cyclic low molecular-weight polymertrans-polyoctenamer rubber (TOR) on the thermal stability of diene rubbers and their vulcanizates was investigated. The investigation was carried out in the air and nitrogen atmospheres using thermogravimetry, DSC and simultaneous thermoanalytical methods. The thermal stability indexes:T ₅,T _max and activation energy of degradation (E), as well asT _g andT _m values, have been determined.It was found thattrans-polyoctenamer (TOR) increases of the thermal stability indices of raw diene rubbers and their vulcanizates. The results show that the thermal degradation of diene rubbers occurred at higher temperature if they were blended with TOR. In our opinion, intermolecular structures formed between the cyclic low-molecular weight polymer and some linear rubber molecules may be the reason for the higher thermal stability of these rubber blends.The work was supported by State Committee for Research, Poland. Grant No. 7.T08 E 032-08.     

Thermal stability,flammability and fire hazard of butadiene-acrylonitrile rubber nanocomposites

This article presents the effect of the method of NBR cross linking on the thermal properties, flammability and fire hazard of its nanocomposites containing modified montmorillonite (NanoBent or Nanofil), using test results obtained by means of a derivatograph, oxygen index and cone calorimetry. It has been found that the thermal stability and flammability of the nanocomposites investigated depend on both the rubber network structure and the type of montmorillonite. The nanoadditives used reduce the flammability of cross-linked nitrile rubber and considerably limit its fire hazard.     

Incompatible reaction for (3-4-epoxycyclohexane) methyl-3′-4′-epoxycyclohexyl-carboxylate (EEC) by calorimetric technology and theoretical kinetic model

(3-4-Epoxycyclohexane) methyl-3′-4′-epoxycyclohexyl-carboxylate (EEC) is a typical epoxy resin (EP). In Asia, due to the unstable reactive natures of EP, various thermal hazard and runaway reaction incidents have been occasioned by EP in the manufacturing process, such as fire, explosion, and toxic release, resulting in loss of life as well financial catastrophes and social outcries. Certain catalysis substances, H₂SO₄, acetic acid, or NaOH, may accelerate the reaction or curing rate for EP. However, an incompatible reaction with these chemical substances may induce a thermal hazard, causing a runaway excursion during the last stage. We employed thermogravimetry (TG) to obtain thermal stability parameters under non-isothermal conditions to evaluate the runaway reactions for EEC. The experimental data were compared with kinetics-based curve fitting to assess thermally hazardous phenomena by optimizing curve fitting on the kinetic parameters. The aim of this study was to estimate the incompatible hazards for EEC, provide thermal hazard information in order to determine the optimum operation conditions, and diminish the likelihood of fire and explosion accidents incurred by EP.     

Effect of different humectants on the thermal stability and fire hazard of nitrocellulose

In order to ensure the thermal safety of nitrocellulose (NC) mixtures in the process of handing, storage, and usage, it is necessary to obtain the thermal stability and fire hazard of NC with different humectants. In this study, the thermogravimetry experiments with four heating rates (5, 10, 15, 20 C min^?1) under nitrogen and air atmospheres were performed to investigate the thermal stability of two NC-humectants, namely NC-water and NC-ethanol mixtures, and pure NC. Moreover, the influence of humectants on the fire hazard of NC was evaluated by the ISO 5660 Cone Calorimeter test. The humectant, water or ethanol, can increase the activation energy and reduce the fire risk of NC. Compared with the NC with water, the NC with ethanol exhibits lower activation energy and higher fire hazard.     

Thermal stability of acrylonitrile/chlorosulphonated polyethylene rubber blend

The properties of chlorosulphonated polyethylene (CSM) rubber, acrylonitrile rubber (NBR) and their blend (50/50 w/w) were studied. Fourier transform infrared (FTIR) studies supported that CSM/NBR rubber blend is self curable, when cross-linking takes place between acrylonitrile groups of NBR and –SO₂Cl groups or in situ generated allyl chloride moieties of CSM. The thermal stability of vulcanizates was analyzed in nitrogen by thermogravimetry. It was found that the initial degradation temperature of elastomer based on CSM rubber is lower than of pure NBR rubber. By adding NBR to CSM rubbers, the degradation temperature of crosslinked material increased, indicating higher thermal stability. The activation energy for the degradation are determined using the Arrhenius equation The activation energies for the rubber blends are higher than for elastomers based on pure rubbers. It was found that the mass loss of the blends at any temperature was between those of the pure rubbers. The differential scanning calorimetry (DSC) was used for the glass transition temperature determination. It is estimated thermodynamic immiscibility of NBR/CSM blend based on noticed two different glass transition temperatures, corresponding to CSM and NBR rubbers.     

Thermal behaviour and mechanical properties of novel RTV silicone rubbers using divinyl-hexa[(trimethoxysilyl)ethyl]-POSS as cross-linker

Divinyl-hexa[(trimethoxysilyl)ethyl]-POSS (DVPS) as an octavinyl-POSS derivative was first prepared. A series of novel polydimethylsiloxane (PDMS)/DVPS hybrid materials as room temperature vulcanized (RTV) silicone rubber were prepared. The chemical incorporation of novel POSS into hydroxyl-terminated PDMS system by hydrolytic condensation reaction was verified by attenuated total reflection (ATR) infrared spectroscopy. Thermal degradation, thermo-oxidative stability and mechanical properties of these novel RTV silicone rubbers were studied by means of thermogravimetric analysis and tensile testing. The results exhibited significantly enhanced effects on the thermal stabilities and mechanical properties as compared to the PDMS polymer prepared with tetraethoxysilane (TEOS). The observed improvements in thermal properties could be attributed to the effective three-dimensional network structures resulting from the structure of DVPS. The thermal decomposition of the RTV silicone rubbers in nitrogen was also monitored by TGA coupled with real-time FTIR, and the degradation residues were also characterized by FTIR. It was found that the POSS cross-linker facilitated the formation of cross-links in the degradation residues. The striking improvement in mechanical properties could be attributed to the synergistic action of the structure of three-dimensional multi-arm cross-linker (vinyl-POSS derivative), the plasticization of self-cross-linking Vinyl-POSS derivative and perfect distribution of vinyl-POSS derivative.     

Synergistic effect between POSS and fumed silica on thermal stabilities and mechanical properties of room temperature vulcanized (RTV) silicone rubbers

In this paper, both divinyl-hexa[(trimethoxysilyl)ethyl]-POSS (DVPS) and fumed silica were firstly introduced into polydimethylsiloxane (PDMS) system using as the cross-linker and the reinforcing filler respectively. And a series of novel RTV silicone rubbers synergistically enhanced by DVPS and fumed silica were prepared. The cross-linked networks in the novel RTV silicone rubbers have been studied by attenuated total reflection infrared spectroscopy, and the dispersions of POSS and fumed silica in these novel RTV silicone rubbers have been observed by means of scanning electron microscope (SEM). And thermal stabilities, thermo-oxidative stabilities and mechanical properties of these novel RTV silicone rubbers were studied by means of thermal gravimetric analysis and universal tensile testing machine, respectively. From the obtained results, it was found that synergistic effect between POSS-rich areas and fumed silica on thermal stability and mechanical property of RTV silicone rubber indeed existed. And the experimental results also exhibited that the thermal stabilities and mechanical properties of the novel RTV silicone rubbers were far better than those of the reference materials (DVPR and MTFR). The striking enhancements in thermal properties and improvements on mechanical properties of novel RTV silicone rubbers were likely attributed to the synergistic effect between POSS-rich domains and fumed silica. Meanwhile, it was found that the mechanical properties of RTV silicone rubbers prepared with a given amount of POSS cross-linker were enhanced with the increment of the loading amount of fumed silica.     

Thermal degradation mechanism of flame retarded epoxy resins with a DOPO-substitued organophosphorus oligomer by TG-FTIR and DP-MS

A novel phosphorus-containing oligomeric flame retardant, poly(DOPO substituted hydroxyphenyl methanol pentaerythritol diphosphonate) (PDPDP) was synthesized and applied to flame retarded epoxy resins. The thermal degradation behaviors of flame retarded epoxy composites with PDPDP were investigated by thermogravimetric analysis (TGA), thermogravimetric analysis/infrared spectrometry (TG-FTIR) and direct pyrolysis-mass spectrometry (DP-MS) techniques. The identification of pyrolysis fragment ions provided insight into the flame retardant mechanism. The results showed that the mass loss rate of the EP/PDPDP composites was clearly lower than pure EP when the temperature was higher than 300 °C in air or nitrogen atmosphere. The results also suggested that the main decomposition fragment ions of the EP/PDPDP composite were H₂O, CO₂, CO, benzene, and phenol. The incorporation of PDPDP can reduce the release of combustible gas and induce the formation of char layer, hence the fire potential hazard was reduced.     

Effect of acrylic polymer and nanocomposite with nano-SiO2 on thermal degradation and fire resistance of APP-DPER-MEL coating

Acrylic nanocomposite and flame retardant coatings with different acrylic polymers were prepared. The effect of molecular structure and molecular weight of acrylic resins and nanocomposite with nano-SiO₂ on the interaction and char formation of ammonium polyphosphate-dipentaerythritol-melamine (APP-DPER-MEL) coating was investigated using differential thermal analysis (DTA), thermogravimetry (TG), Limiting Oxygen Index (LOI), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and fire protection test. The interaction of APP, DPER, MEL and 3F-1 acrylic resin led to the formation of intumescent coherent char at 300-450 °C. Owing to low molecular weight and lack of benzene rings, F-963 acrylic resin decomposed at lower temperature than APP, and hence their endothermic interaction was destroyed. The well-distributed nano-SiO₂ particles in acrylic nanocomposite could modify char formation and anti-oxidation of char structure at high temperature. It is noted that the fire protection properties of nanocoating with acrylic nanocomposite were better than those of flame retardant coatings with conventional acrylic resins.     

Fire performances of unvulcanized rubbers and influences of horizontal flowing melts

Fire performances of typical unvulcanized rubbers are investigated and the properties of rubbers and their flowing melts are characterized. If the horizontal melt flow is allowed the burning area increases by 75%–473% and proportionally the peak mass loss rate promotes by 55%–300%. When the rubber converts to its flowing melt the viscosity and heat of complete combustion reduce, and the total crosslink density increases, which might be ascribed to the curing, the curing reversion and the decomposition mechanism. Except for acrylonitrile-butadiene rubber both the T_d,5% and the decomposition activation energy decrease. The pool fire development is related with the melt viscosity, the decomposition temperature and heat release rate (HRR) in the cone calorimeter. Low viscosity contributes to large pool area. High HRR and low decomposition temperature accelerate the extension of burning area.     

Flammability of vulcanizates of diene rubbers

This article discusses the effect of the cross-linking of diene elastomers (BR, SBR, NBR), with the use of an organic peroxide or sulfur, on their flammability and fire hazard. Flammability tests were carried out by the method of oxygen index, combustion time (in air) and ignition temperature measurements. Fire hazard was determined on the basis of test results obtained by means of a cone calorimeter. Toxicometric coefficients ( \textRTFH_{\textco/\textco 2} {\text{RTFH}}_{{{\text{co}}/{\text{co}}_{ 2} }} and W_LC50SM) and the emission of polycyclic aromatic hydrocarbons (PAH) were determined. Test results were interpreted from the point of view of the chemical constitution of elastomer macromolecules as well as the structure of its network structure.     

Influence of surface modification on thermal stability and flammability of cross-linked rubbers

The paper discusses the test results of thermal stability and flammability of cross-linked diene rubbers containing silica prepared “in situ” from alkoxysilane precursors. The effect of the surface modification of unfilled vulcanizates by means of aqueous solutions of halogens, boron and organo-phosphoric compounds on their flammability was also assessed. The thermal analysis has been performed in air with the use of derivatography. The flammability of vulcanizates has been determined by the method of oxygen index and in air. It has been found that the modification of the vulcanizates with tetraethoxysilane that makes it possible to form silica “in situ” considerably reduces the flammability of cross-linked rubbers. The surface modification of the vulcanizates with halide and organo-phosphoric compounds allows one to radically decrease their flammability. The boric flame-retardant agents are the most effective modifiers. The most beneficial results were obtained with the use of boric acid.     

Studies on phase morphology and thermo-physical properties of nitrile rubber blends

The study deals with the morphological and thermal analysis of binary rubber blends of acrylonitrile-co-butadiene rubber (NBR) with another polymer. Either ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA), chlorosulphonated polyethylene (CSM), or polyvinyl chloride (PVC) has been selected for the second phase. Depending on the relative polarity and interaction parameter of the components, the binary blends showed development of a bi-phasic morphology through scanning electron microscopy (SEM). Use of different types of thermal analysis techniques revealed that these blends are generally incompatible excepting one of NBR and PVC. Derivative differential scanning calorimetry (DDSC), in place of conventional DSC, has been used to characterize the compatibility behavior of the blends. NBR–PVC shows appearance of only one glass transition temperature (T _g) averaging the individual T _g’s of the blend components. The partially missible blend of NBR and CSM shows a broadening of T _g interval between the phase components, while the immiscible blends of either NBR–EPDM or NBR–EVA do not show any change in T _g values corresponding to the individual rubbers of their blend. The experimental T _g values were also compared with those calculated theoretically by Fox equation and observed to match closely with each other. Studies have also been made to evaluate the thermal stability of these blends by thermo-gravimetric analysis (TG) and evaluation of activation energy of respective decomposition processes by Flynn and Wall method. Thermo-mechanical analysis (TMA) was found to be effective for comparison of creep recovery and dimensional stability of the blends both at sub-ambient as well as at elevated temperatures.