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.     

Control of the plasticity of organosilicon rubbers by their modification with polypyrrole

Modification of organosilicon rubbers SKTN and SKTV with polypyrrole was studied. The modifying agent was synthesized directly in the rubbers containing iron trichloride acting as oxidant and catalyst, using the diffusion procedure and impregnation of organosilicon rubbers with pyrrole-2-carboxylic acid in supercritical carbon dioxide. Changes in the ductility and viscosity of the composite materials were analyzed.     

Experimental branching results for diene polymers by use of gel-permeation chromatography

Branching analyses in styrene–butadiene rubbers and polybutadiene rubbers have revealed large differences in branching between rubbers polymerized in different ways. The functionalities of several star-branched solution-polymerized styrene–butadiene rubbers were calculated and compared to their expected structures. Emulsion-polymerized polybutadiene rubber and a series of solution-polymerized polybutadienes made with different catalysts had different degrees of random branching, and evidence is presented indicating that the different available catalyst systems provide some latitude in making rubbers of different branching contents. Random branching analyses on a series of emulsion-polymerized styrene–butadiene rubbers revealed the dependency of branching on molecular weight and molecular weight distribution. The influence of polymerization temperature on the branching of emulsion-polymerized styrene–butadiene rubber was also studied.     

Influence of carbon black on thermal properties and flammability of cross-linked elastomers

The paper presents the results of testing thermal properties and combustibility of butadiene-acrylonitrile rubber vulcanizates with different contents of bounded acrylonitrile: Perbunan NT 1845 and Perbunan NT 3945 from Bayer. The rubbers were cross-linked by means of dicumyl peroxide. Four types of carbon black with different specific surfaces were used as fillers. The test results were obtained with the use the derivatograph, DSC-204 of Netzsch, measurements of flammability by the method of oxygen index and in air. The results of measurements have shown that the thermal stability and flammability of the vulcanizates under investigation are affected by the activity of solid phase and the degree of surface development as well as the flexibility of polymeric chain and the degree of its unsaturation. A clear relationship has been found between the thermal properties and flammability of the cross-linked butadiene-acrylonitrile rubbers.     

Addition-curable type liquid silicone rubbers based on phenyl-containing organopolysiloxanes with terminal vinyl groups

Russian Chemical Bulletin - A series of organosilicon rubbers of the addition-curable type containing dimethyland methylphenylsiloxy, or diphenylsiloxy units with terminal vinyl groups were...     

The effect of different impact modifiers in halogen-free flame retarded polycarbonate blends - II. Fire behaviour

In this second of a series of two papers, the fire behaviour of halogen-free flame retarded polycarbonate (PC) blends with different impact modifiers was studied. The impact modifiers were acrylonitrile-butadiene-styrene (ABS), a poly(n-butyl acrylate) rubber (PBA) with a poly(methyl methacrylate) (PMMA) shell and two silicone-acrylate rubbers consisting of PBA with different amounts of polydimethylsiloxane (PDMS) and different shell materials (PMMA and styrene-acrylonitrile, SAN). The flame retardant was bisphenol A bis(diphenyl phosphate) (BDP). Flammability was determined by LOI and UL 94. The burning behaviour under forced flaming conditions was studied by cone calorimeter under different external irradiations and by pyrolysis combustion flow calorimeter measurements. The exchange of ABS with the pure acrylate rubber worsened flammability, while similar results were obtained in cone calorimeter measurements. The exchange of ABS with the silicone-acrylate rubbers is promising, particularly with higher amounts of PDMS. In flammability tests strongly enhanced LOI values were obtained and therefore silicone-acrylate rubbers look like promising alternatives for ABS.     

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.     

Derivatives of carbamide, symmetrical triazines, and heptazines: Ecologically clean fire retardants for different thermostable compositions

The problems of replacing conventional halogen-containing fire retardants with alternative products, such as carbamide and symmetrical triazines and heptazines obtained on its basis, as well as different phosphates and ammonium polyphosphates, are considered. The main properties of the suggested compounds are described. It is shown that the range of compounds can be used, not only as fire retardants, but also as curing or modifying agents for polymer compositions, thermostabilizers of resins (based on ethylene-propylene rubbers) and sealants, and components of thermostable organosilicon compositions.     

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 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.     

Poly(vinyl chloride) powder as a low-cost flame retardant modifier for epoxy composites

For the purpose of the study, epoxy (EP) composites modified with 5–40?wt% of poly(vinyl chloride) (PVC) powder were manufactured. The influence of PVC powder on the fire behavior of EP-based composites was determined with a UL-94 HB test and cone calorimetry, supplemented by a thermogravimetric analysis. The fire behavior study showed that PVC powder may effectively decrease the flammability of EP in case of at least 20?wt% filler content while composites containing lower amounts of PVC powder (5 and 10?wt%) were characterized with significant improvement in tensile strength without reduction in flammability in reference to the unmodified EP.     

Thermal properties and combustibility of elastomer–protein composites

This article presents the test results of thermal properties and flammability of crosslinked nitrile rubber in the presence of zinc oxide or nano-zinc oxide containing waste keratin, using the test results obtained by means of a derivatograph, DSC, and oxygen index. The influence of modified montmorillonite (NanoBent) on selected properties of investigated elastomer–protein composites has also been studied. The composites' thermal stability and flammability depend on the method of composite preparation and the quantity of added keratin. The addition of waste keratin reduces the flammability of NBR–keratin composites.     

Thermal stability and combustibility of rubbers and sealing plates

The present paper describes the test results concerning the thermal properties and flammability of the selected sealing plates and rubbers that may become components of plates. The thermal analysis methods (DTA, DSC, TG, and DTG) and flammability methods (OI, rate of burning in air, and ignition temperature) were used in this study. The thermal analysis of plates was also performed under isothermal conditions. It was stated that investigated sealing plates belong to the group of flame-retardant materials and type of rubber included in plate influences its thermal stability and combustibility.     

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.     

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.     

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.     

σ-π conjugation in group IVA compounds of indene and indane

A series of indanyl and indenyl derivaties of silicon and tin has been prepared and the molecular ionization potentials determined by electron impact mass spectrometry. Substitution of the hydrogen at C(1) by an organosilicon group results in a decrease of the ionization potential by ～0.6–0.8 eV, while extension of the π-system into the five-membered ring via the double bond produces a further decrease of the ionization potential by ～0.2–0.3 eV. The results are consistent with the postulate of a σ-gp hyperconjugative interaction between the β metal-carbon bond and the aromatic π-system.     

Flammability Tests and Investigations of Properties of Lignin-Containing Polymer Composites Based on Acrylates

In this paper flammability tests and detailed investigations of lignin-containing polymer composites’ properties are presented. Composites were obtained using bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BPA.GDA), ethylene glycol dimethacrylate (EGDMA), and kraft lignin (lignin alkali, L) during UV curing. In order to evaluate the influence of lignin modification and the addition of flame retardant compounds on the thermal resistance of the obtained biocomposites, flammability tests have been conducted. After the modification with phosphoric acid (V) lignin, as well as diethyl vinylphosphonate, were used as flame retardant additives. The changes in the chemical structures (ATR-FTIR), as well as the influence of the different additives on the hardness, thermal (TG) and mechanical properties were discussed in detail. The samples after the flammability test were also studied to assess their thermal destruction.     

Deactivation of small diameter fused silica capillary columns with organosilicon hydrides

Small diameter fused silica capillary columns (50–75 μm i.d.) were deactivated at relatively low temperatures (250–300°C) with a mixture of polymethylhydrosiloxanes and several lowmolecular-weight organosilicon hydrides. Reproducible surface deactivations of highest quality were achieved with the polymethylhydrosiloxane (PMHS) reagent. Deactivations performed with PMHS via dynamic coating with neat or diluted reagent were evaluated by gas chromatography. Deactivations achieved with organosiloxane mono-, tri-, and tetrahydrides were also evaluated and compared. Low-molecular-weight organosilicon hydride deactivations were less time consuming and required lower head pressures for filling and coating columns with the reagent. Critical surface tensions of capillary surfaces modified with PMHS and the low-molecular-weight organosilicon hydrides gave support to the dehydrocondensation reaction between silica surface silanols and silyhydride bonds of the reagents. Slopes from Zisman plots indicated that coverage of the surface ranged from highest for the polymer (PMHS) to lowest for the monomers (TMS and PMDS). Efficiency measurements showed the influence that surface modification had on the uniformity and stability of the coated capillary columns. Well-deactivated capillary columns permitted the chromatography of polar solutes using supercritical carbon dioxide as mobile phase.     

Surface modification of chlorobutyl rubber by plasma polymerization

Radio frequency (r.f.) plasma polymerization of vinylidene fluoride (CH₂CF₂) has been used to modify the surface properties of chlorobutyl rubber. FTIR-ATR spectra of the treated rubbers and transmission spectra of plasma polymer films on NaCl windows indicated that as power increased the F/H ratio decreased. SIMS tests supported the FTIR results, and showed that the decrease in the F/H ratio was due to a decrease in the amount of F and an increase in the amount of H in the plasma polymer. Sliding friction measurements showed a reduction in the coefficient of friction (μ) from 3.7 for the untreated rubber to values ranging between 0.4 and 1.9 for the plasma-treated rubbers. There did not appear to be any correlation between the coefficient of friction and plasma power or monomer flow rate, and the average coefficient of friction for the plasma-treated samples was 0.9, which was lower than a commercially used silicone oil treatment (μ = 1.1–1.3). Repetitive sliding friction tests showed that the plasma- and silicone oil treated-chlorobutyl rubbers had the similar lubricating lifetimes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1651–1660, 1997