Thermal stability and flammability of butadiene- acrylonitrile rubber cross-linked with iodoform

Summary The paper discusses the results of thermal analysis and flammability of butadiene-acrylonitrile rubber, Perbunan NT 1845 of Bayer, cross-linked with iodoform. The properties of the iodoform vulcanizate have been compared with those of peroxide vulcanizate. The thermal analysis has been performed in air with use of a derivatograph under air and nitrogen atmosphere as well as dynamic scanning calorimetry (DSC). The flammability of vulcanizates has been determined by the method of oxygen index and in air. The toxicity of the thermal decomposition and combustion products of the vulcanizates under investigation has been also determined. Based on complementary examinations, DTA and DSC curves have been interpreted from the point of view of thermal transitions of the conventionally and non-conventionally cross-linked nitrile rubbers. The glass transition temperature of the cross-linked polymer both in cooling and heating has been determined.     

Effect of the modification of silica on thermal properties and flammability of cross-linked butadiene-acrylonitrile rubbers

The paper presents the results of testing the thermal stability and flammability of butadiene-acrylonitrile rubber vulcanizates with different contents of combined acrylonitrile: Perbunan NT 1845 and Perbunan NT 3945 from Bayer, containing unmodified and bromine- or iodine-modified silica. The test results were obtained with the use of a derivatograph, measurements of flammability by the method of oxygen index, in air and also with the use of a cone calorimeter. The effect of the modification on the zeta potential was also examined. A considerable reduction in the flammability of nitrile rubber vulcanizates filled with silica can be obtained by the modification of filler with bromine or iodine. All the vulcanizates containing modified silica are self-extinguishing. An appropriate filling of NBR 39 vulcanizates with bromine-modified silica makes it possible to obtain non-flammable polymeric materials. They neither ignite nor glow under the action of a flame source for 30 s. The findings can be a rational basis for the synthesis of modified silica that can act as active filler and effective flame-retardant agent at the same time.     

Effect of the top layer modification of polymers on their thermostability and flammability

Thermal properties, ageing resistance and flammability of peroxide vulcanizates of butadiene-acrylonitrile rubber Perbunan NT 1845 (NBR) of Bayer, modified in bulk and on a surface with synthesized hybrid functional poly(methylsiloxanes) were investigated. The derivatographic, DSC, oxygen index and FTIR methods were applied. It was stated that addition of poly(methylsiloxanes) caused distinct increase of ageing resistance and of NBR vulcanizates and decrease of their thermal decomposition rate and flammability, providing self-extinguishing samples. The mechanism of addition reactions of Si–H bond to multiple bonds of NBR has been proposed.     

Influence of cryogenic modification of silica on thermal properties and flammability of cross-linked nitrile rubber

The article presents the results of testing thermal properties and combustibility of butadieneacrylonitrile rubber with 18% contents of bounded acrylonitrile, NBR 18. Two types of silica, Zeosil 175C and Ultrasil VN-3, with different specific surfaces were used as filler. Zeosil 175C and Ultrasil VN-3 were modified via cryogenic dezaggregation method. The activity of unmodified and cryogenic modified silica toward butadiene-acrylonitrile rubber were investigated. The sulphur and peroxide vulcanizates contained 20, 30, 40, and 50 phr. of the filler were studied. The article discusses also the test results of thermal stability and flammability of NBR 18 containing silica prepared "in situ" from alkoxysilane precursor. The test results were obtained with the use of derivatograph, measurements of flammability by the method of oxygen index, and in air. The effect of the silica modification on the SEM and AFM was also examined. The method of cryogenic modification enables to achieve increase of mineral fillers activity towards elastomer and reduction in the flammability of NBR 18 vulcanizates. It has been found that the modification of the vulcanizates of NBR 18 with tetraethoxysilane that makes it possible to form silica "in situ" reduces the flammability of cross-linked rubbers.     

Flammability of butadiene-acrylonitrile rubbers

The paper discusses the test results of butadiene-acrylonitrile rubber, Perbunan NT 1845 and Perbunan NT 3945, flammability and properties that characterise these elastomers under fire conditions. The flammability was tested by means of oxygen index and thermovision methods. The thorough testing of flammability performed by means of a cone calorimeter made it possible to assess the behaviour of these polymers under fire conditions. The following properties of the tested copolymers were taken into account in this assessment: ignitability, heat release during combustion, smoke-forming capability and toxicity of the gaseous products of thermal decomposition and combustion. It has been found that the increase in the acrylonitrile unit content in the copolymer decreases its flammability and the relative toxic fire hazard, but clearly increases the smoke-forming capability and so the specific extinction area.The interpretation of test results of the elastomers under investigation takes into consideration their thermal stability assessed on the basis of differential thermal analysis, thermogravimetry and other complementary methods.This revised version was published online in November 2005 with corrections to the Cover Date.     

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.     

Thermal properties of swollen butadiene-acrylonitrile rubber vulcanizates

The present paper discusses the results of assessing thermal properties of nitrile rubber, Perbunan NT 3945 and its peroxide vulcanizates, before and after their swelling in solvents such as benzene, toluene and dimethylformamide. The measurements were carried out by means of differential scanning calorimetry (DSC) and thermogravimetry (TG) under nitrogen. It has been found that a slight rise in the glass transition temperature due to the elastomer cross-linking is clearly revealed under the influence of its vulcanizates swelling in solvents whose solubility parameters considerably differ from the solubility parameters of the polymer. The thermal curves of swollen samples reveal processes resulting from polymer-solvent interactions and thermodesolvation processes, which accompany the initial stage of solvent evaporation.The authors would like to express their thanks to the Bayer company for providing free of charge samples of Perbunan NT 1845 and Perbunan 3945 which were used in this study.     

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.     

Thermal stability and flammability of styrene–butadiene rubber (SBR) composites

The article presents the effect of attapulgite (ATT) and its synergic action with carbon or silica on the thermal properties and flammability of cross-linked styrene–butadiene rubber. It has been shown that ATT is active filler improving the thermal and mechanical properties of composites containing this aluminosilicate. The decreased flammability of vulcanizates containing ATT compared to that of unfilled vulcanizates results from good insulating properties of the ATT used. The considerable reduction in the flammability of composites containing ATT and carbon nanofiber or silica is connected, first of all, with the formation of a homogeneous boundary layer.     

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.     

Effect of mineral fillers on thermal properties and flammability ofcis-1,4-polyisoprene vulcanizates

The effect of mineral fillers such as Ultrasil VN-3, Ze?O?Sil P-45, Aerosil 200, Frantex 8, Kaolin and precipitated calcium carbonate on the thermal properties sulphur vulcanizates ofcis-1,4-polyisoprene were studied by means of thermal analysis. It was found that the addition of a mineral filler did not change the nature of the thermal processes in isoprene vulcanizates essentially, but it distinctly affected the positions of the peaks recorded in the DTA curves. The mineral fillers affected the temperatures and rates of degradation and destruction of polyisoprene cross-linked with sulphur. The presence of a mineral filler brought about a decrease in the flammability ofcis-1,4-polyisoprene sulphur vulcanizates.     

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.     

Effect of the spatial network structure and cross-link density of diene rubbers on their thermal stability and fire hazard

The paper presents the results of investigating the effect of the density and spatial network structure of diene rubbers (NBR and SBR) on their thermal properties and fire hazard. The rubbers were either conventionally cross-linked by means of sulfur and organic peroxide or nonconventionally with the use of iodoform (CH₃I). Based on thermo-kinetic analysis, the destruction activation energy of the elastomers investigated and their vulcanizates was determined under air and inert gas. The analysis of particular stages of their thermal decomposition was also presented. During the combustion of the elastomeric materials obtained, it has been found that their fire hazard depends not only on the elastomer chemical structure but also on the method of its cross-linking.     

Sulfur-Free Vulcanization of Modified Butadiene-Acrylonitrile Rubber SKN-40PVKh-30, Aimed To Obtain Elastomeric Materials Resistant to Aggressive Media

A study was made of the thermal, peroxide, and radiation vulcanization of modified butadiene-acrylonitrile rubber SKN-40PVKh-30 in the presence of a polyhalomethyl compound, 1,4-bis[(4-trichloromethylphenyl)dichloromethyl]benzene, with epoxy and phenol-formaldehyde resins and 4,4′-dithiobis-N-phenylmaleimide (a sensitizer) additionally included in the formulation with the aim to improve the technical properties of the vulcanizates and elastomeric materials. The parameters of the three-dimensional network of the vulcanizates were studied by sol-gel analysis; the total number of active chains of the network (1/M_c), number of cross-linked molecules \((1/M_{n_\tau } )\), and gel fraction content were determined for the thermal, peroxide, radiation, and thermoradiation vulcanizates.     

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.     

Thermal properties and combustibility of cross-linked XNBR/CSM blends

The article describes the measurement results of the thermal properties of cross-linked blends of carboxylated butadiene-acrylonitrile rubber (XNBR, Krynac X.7.50) and chlorosulfonated polyethylene (CSM, Hypalon 48) under inert gas (DSC, TG) and in air (derivatography). The blends were cross linked at a temperature of 150 °C by means of MgO in the presence of stearic acid. The thermal curves were interpreted from the point of view of phase transitions and chemical reactions of high-molecular components. It has been found that the polymers under investigation show a good compatibility resulting from the presence of both inter-polymeric covalent bonds and inter-polymeric ionic bridges containing magnesium ions that fulfill the role of chemical compatibilizer. The study has shown that XNBR/CSM blends belong to a group of polymeric materials that are self-extinguished in air. Their flammability, determined by OI and the combustion time in air, clearly depends on the cross-linking degree associated with the quantity of MgO incorporated into the blend of elastomers.     

Thermal properties and combustibility of elastomer–protein composites

The article describes the measurements results of the influence of waste keratin on the properties of cross-linked styrene-butadiene rubber especially taking its thermal properties and flammability into consideration. The biopolymer used was thoroughly examined by means of derivatography, elementary analysis, FTIR spectroscopy, Zetasizer nano S90, and Zetasizer 2000. It has been found that the presence of protein facilitates the cross-linking of the elastomer investigated and the elastomeric-protein materials are characterized by good thermal and mechanical properties as well as a considerably increased resistance to thermooxidative aging. Under the influence of keratin, the flammability of the composites obtained is decreased.     

Thermal stability and combustibility of butyl and halogenated butyl rubbers

The effects of flame retardants such as hydrated aluminium oxide, antimony trioxide and chloroparaffin on the thermal properties and flammability of sulphur vulcanizates of butyl and halogenated butyl elastomers were studied. The thermoanalytical curves of the elastomers were interpreted. Greater tendencies to thermal degradation were observed for halogenated butyl elastomers than for the original butyl rubber elastomer. This was confirmed by elastomer combustibility studies. The use of these flame retardants allowed the formation of self-extinguishing vulcanizates of the investigated elastomers.     

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.