Hydroxyapatite-Filled Acrylonitrile-Butadiene Rubber Composites with Improved Cure Characteristics and Reduced Flammability.

The goal of this work was to develop acrylonitrile-butadiene (NBR) elastomer composites filled with hydroxyapatite (HAP) characterized by improved cure characteristics and resistance to burning. Silane, i.e., (3-aminopropyl)-triethoxysilane, ionic liquid, i.e., 1-decyl-3-methylimidazolium bromide and surfactant, i.e., cetyltrimethylammonium bromide, were used to improve the filler's dispersibility in the elastomer matrix and to reduce the time and temperature of vulcanization. The effects of HAP and dispersants on the cure characteristics, crosslink density and physico-chemical properties of NBR composites were explored. The additives used, especially the ionic liquid and surfactant, effectively improved the dispersion of HAP in the NBR matrix. The amount of HAP and the dispersant used strongly affected the cure characteristics and crosslink density of NBR. The optimal vulcanization time significantly increased with HAP content and was pronouncedly reduced when ionic liquid and surfactant were applied. In addition, ionic liquid and surfactant significantly lowered the onset vulcanization temperature and improved the crosslink density and hardness of the vulcanizates while impairing their elasticity. HAP and dispersants did not significantly affect the damping properties or chemical resistance of NBR vulcanizates. Above all, application of HAP considerably enhanced the resistance of vulcanizates to thermo-oxidative aging and reduced their flammability compared with the unfilled NBR.

Effect of Silicone Oil on Properties and Performance of Ceramizable Styrene-Butadiene Rubber-Based Composites.

New trends in the circular economy and sustainability are pointing towards the gradual elimination of standard flame retardants such as phosphorus compounds or halogenated compounds. New solutions are therefore being sought in this area and ceramizable composites could be an interesting alternative. Weak rheological properties are one of the main disadvantages of ceramizable composites. This study tested ceramizable composites composed of styrene-butadiene rubber (SBR) as a polymer matrix and mica as a mineral filler and aimed to improve the viscoelastic properties of silicone oil as a plasticizer. To characterize this composite's mechanical properties before and after ceramization, the viscoelastic properties were tested with a dynamic oscillating rheometer and the thermal behavior with a cone calorimeter. This paper also provides results showing differences (via the abovementioned properties) between vulcanization with sulfur and that with peroxide for the ceramizable composites based on SBR. The presented results, showing changes in mechanical properties, dynamic viscosity or flammability, among others, allow a better understanding of elastomeric composites with ceramizable flame-retardant systems. Such composites can find a wide range of applications, from lagging for electrical cables to building elements such as floor coverings and fire barriers.

Effect of Hybrid Filler, Carbon Black-Lignocellulose, on Fire Hazard Reduction, including PAHs and PCDDs/Fs of Natural Rubber Composites.

The smoke emitted during thermal decomposition of elastomeric composites contains a significant number of carcinogenic and mutagenic compounds from the group of polycyclic aromatic hydrocarbons, PAHs, as well as polychlorinated dibenzo-p-dioxins and furans, PCDDs/Fs. By replacing carbon black with a specific amount of lignocellulose filler, we noticeably reduced the fire hazard caused by elastomeric composites. The lignocellulose filler reduced the parameters associated with the flammability of the tested composites, decreased the smoke emission, and limited the toxicity of gaseous decomposition products expressed as a toximetric indicator and the sum of PAHs and PCDDs/Fs. The natural filler also reduced emission of gases that constitute the basis for determination of the value of the toximetric indicator WLC50SM. The flammability and optical density of the smoke were determined in accordance with the applicable European standards, with the use of a cone calorimeter and a chamber for smoke optical density tests. PCDD/F and PAH were determined using the GCMS-MS technique. The toximetric indicator was determined using the FB-FTIR method (fluidised bed reactor and the infrared spectrum analysis).

The Morphology, Mechanical and Dynamic Properties, Fire Hazard and Toxicity of Chloroprene and Butadiene Rubber Composites Cross-Linked with Zinc.

This paper presents the influence of zinc on the cross-linking process, mechanical and dynamic properties, morphologies and balance of thermal degradation of blends containing chloroprene rubber (CR) and butadiene rubber (BR). The novel aspect of this research is a comprehensive approach presenting a new curing agent for the CR/BR blends to increase their cross-linking density and final properties, including non-flammability and low fire hazard. This is due to the need to find an alternative to zinc oxide, which is the standard curing agent for chloroprene rubber. The regulations of the European Union enforce a significant limitation on the use of this compound in elastomer technology, due to its harmful effect on aquatic organisms. In this paper, the CR/BR composites were cured with zinc and filled with natural silica fillers (sillitin or chalcedonite) or synthetic silica filler (aerosil). The investigation focused on the morphology characterization of the obtained compounds, their cross-linking degree, swelling, mechanical and dynamic properties, fire hazard and toxicity. The structure of cured CR/BR blends was characterized via scanning electron microscopy (SEM). The fire resistance studies were performed using cone calorimetry or oxygen index methods, whereas toxicity tests were performed with the use of the FB-FTIR (fluidized bed reactor coupled with FTIR analyzer) method. The results showed that obtained CR/BR products were characterized by satisfactory final properties. The properties determined by the oxygen index and cone calorimetry methods, including the behaviors of the tested CR/BR vulcanizates in fire conditions, showed that the produced compounds were characterized by a low fire hazard and can be classified as non-combustible rubber products. However, the toxicity of the decomposition products, determined at 450, 550 and 750 °C, was very high.

Advanced Ethylene-Propylene-Diene (EPDM) Rubber Composites Filled with Raw Silicon Carbide or Hybrid Systems with Different Conventional Fillers.

We studied the effects of silicon carbide (SiC) and SiC hybrid systems with different conventional fillers (silica, carbon black, graphene, hydrotalcite, halloysite) on the rheometric measurements, crosslink density, mechanical performance, aging stability, morphology, thermal behaviour, and flammability of ethylene-propylene-diene (EPDM) rubber composites. The hybrid filler systems showed technically promising synergetic effects on the performance of the EPDM composites. A pronounced reinforcing effect in EPDM composites filled with hybrid SiC filler systems was noted. Tensile strength increased in the systems with carbon black, silica, and graphene nanoplatelets, by 21%, 37%, and 68%, respectively, compared to the neat EPDM. Dynamic-mechanical analysis (DMA) revealed a shift of the glass transition temperature (Tg) of EPDM composites towards higher values following the incorporation of hybrid SiC fillers, indicating that the mobility of the macromolecule chains was restricted by the presence of filler particles. Importantly, the application of SiC as a filler in EPDM rubber composites contributed to a considerable reduction in flammability, as demonstrated by microscale combustion calorimetry (MCC). The most promising results were obtained for HAL/SiC and LDH/SiC hybrid systems, which produced final composites with high flame retardancy and good mechanical performance. The study highlights the significant potential of SiC and SiC hybrid systems as effective fillers improving the properties of elastomer composites.

Investigation into the Effect of Spinel Pigments on the Photostability and Combustion Properties of Ethylene-Norbornene Copolymer.

Multicolor ethylene-norbornene (EN) composites filled with three different spinel pigments (Cobalt Green-PG50, Zinc Iron Yellow-PY 119, Praseodym Yellow-PY159) were prepared by melt mixing and characterized in terms of their stability under destructive environmental conditions. The EN films were subjected to accelerated aging by ultraviolet (UV) photooxidation for 300 h, 600 h, or 900 h. The mechanical performance of the EN composites was investigated in static and dynamic mechanical tests. The morphologies of the EN samples and their color changes during the aging process were evaluated by scanning electron microscopy (SEM) and spectrophotometric measurements. Fourier transform infrared (FTIR) spectroscopy was applied to determine the amount of carbonyl groups resulting from surface oxidation at different aging times. The effects of the spinel pigments on the thermal stability and combustion properties of the multicolor polymer composites were also assessed, and compared with a sample containing the organic Pigment Yellow 139 (PY139). The results show that the color changes (ΔE) in the spinel pigments were minor in comparison to those in the organic pigment (PY139) and the reference film. The Zinc Yellow (PY119) pigment was the most effective stabilizer of EN copolymer. Moreover, the spinel pigments had a positive effect on the flame retardancy of the EN composites. Microcombustion tests (MCC) showed that the incorporation of both the spinels and the organic pigment PY139 into the EN matrix reduced the heat release rate (HRR) and total heat release (THR) parameters.

Cat-CrNP as new material with catalytic properties for 2-chloro-2-propen-1-ol and ethylene oligomerizations.

The contemporary search for new catalysts for olefin oligomerization and polymerization is based on the study of coordinating compounds and/or organometallic compounds as post-metallocene catalysts. However known catalysts are suffered by many flaws, among others unsatisfactory activity, requirement of high pressure or instability at high temperatures. In this paper, we present a new catalyst i.e. the crystalline complex compound possesing high catalytic activity in the oligomerization of olefins, such as 2-chloro-2-propen-1-ol and ethylene under very mild conditions (room temperature, 0.12 bar for ethylene oligomerization, atmospheric pressure for 2-chloro-2-propen-1-ol oligomerization). New material-Cat-CrNP ([nitrilotriacetato-1,10-phenanthroline]chromium(III) tetrahydrate) has been obtained as crystalline form of the nitrilotriacetate complex compound of chromium(III) with 1,10-phenanthroline and characterized in terms of its crystal structure by the XRD method and by multi-analytical investigations towards its physicochemical propeties The yield of catalytic oligomerization over Cat-CrNP reached to 213.92 g · mmol-1 · h-1· bar-1 and 3232 g · mmol-1 · h-1 · bar-1 for the 2-chloro-2-propen-1-ol and ethylene, respectively. Furthemore, the synthesis of Cat-CrNP is cheap, easy to perform and solvents used during preparation are environmentally friendly.

Characterization of Ethylene-propylene Composites Filled with Perlite and Vermiculite Minerals: Mechanical, Barrier, and Flammability Properties.

Perlite and vermiculite are naturally occurring minerals, commonly used by industry to obtain highly thermoisolative and/or non-flammable materials. However, there has been little research into the preparation and application of rubber compounds containing these inexpensive mineral fillers. Here, we show the benefits of perlite and vermiculite minerals as fillers for ethylene-propylene rubber (EPM) composites. To obtain more uniform dispersion and improved compatibility between the minerals and the elastomer matrix, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (AMIMTFSI) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIMTFSI) imidazolium ionic liquids (ILs) were added. The mineral fillers were found to be attractive semi-reinforcing fillers, which also act as flame retardants in the elastomer composites. Furthermore, a higher content of vermiculite mineral significantly reduced the air permeability of the composites. The incorporation of ionic liquids into the EPM-filled systems had a considerable effect on the torque increment, crosslink density, and more importantly the flammability of the studied compounds. The application of 2.5 parts per hundred parts of rubber (phr) BMIMTFSI, in particular, reduced the flammability of the EPM composite, as the maximum heat release rate (HRRmax) decreased from 189.7 kW/m2 to 170.2 kW/m2.

New Organic/Inorganic Pigments Based on Azo Dye and Aluminum-Magnesium Hydroxycarbonates with Various Mg/Al Ratios.

This study set out to investigate the impact of aluminum-magnesium hydroxycarbonates (LHs) with various Mg/Al ratios on the formation of hybrid pigments. The colorants were also evaluated for their flame-retardant properties. In the first part of the study, the hybrid pigments were submitted to comprehensive characterization using time-of-flight secondary ion mass spectrometry (TOF-SIMS), 27Al solid-state nuclear magnetic resonance (NMR) spectroscopy, powder X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and N2 adsorption as well as scanning and transmission electron microscopy (SEM/STEM). The relationship between the Mg/Al ratios of the LH carriers and the formation of lake pigments was explored. The TOF-SIMS spectrum of LH modified with azo chromophore (AC) showed an intense peak for the C19H15O5N2Mg+ ion, confirming metal-dye interactions. Incorporation of the organic colorant into the LH host enhanced its resistance to dissolution in organic solvent (butyl acetate), as well as improving its color stability under elevated temperatures. The second part of the study evaluated the flammability of ethylene-norbornene (EN) composites, in which the pigments had been applied as colorants. Cone calorimetry revealed that addition of the organic-inorganic pigments resulted in a substantial improvement of the flame retardancy, reflected by the decreased values of the heat release rate (HRRMAX) and total heat release parameter (THR) of the EN composites in comparison to a neat sample (unfilled EN).

Carminic Acid Stabilized with Aluminum-Magnesium Hydroxycarbonate as New Colorant Reducing Flammability of Polymer Composites.

In this study, hybrid pigments based on carminic acid (CA) were synthesized and applied in polymer materials. Modification of aluminum-magnesium hydroxycarbonate (LH) with CA transformed the soluble chromophore into an organic-inorganic hybrid colorant. Secondary ion mass spectroscopy (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV-Vis spectroscopy were used to study the structure, composition, and morphology of the insoluble LH/CA colorant. Successful modification of the LH was confirmed by the presence of interactions between the LH matrix and molecules of CA. XPS analysis corroborated the presence of CA complexes with Mg2+ ions in the LH host. The batochromic shift in UV-Vis spectra of the organic-inorganic hybrid colorant was attributed to metal-dye interactions in the organic-inorganic hybrid colorants. Strong metal-dye interactions may also be responsible for the improved solvent resistance and chromostability of the modified LH. In comparison to uncolored ethylene-norbornene copolymer (EN), a modified EN sample containing LH/CA pigment showed lower heat release rate (HRR) and reduced total heat release (THR), providing the material with enhanced flame retardancy.

Effect of POSS Particles and Synergism Action of POSS and Poly-(Melamine Phosphate) on the Thermal Properties and Flame Retardance of Silicone Rubber Composites.

This article presents flame retardant compounds for silicone rubber (SR) in the form of polyhedral oligomeric silsequioxanes (POSS), containing both isobutyl groups and amino-propyl (AM-POSS) or chloro-propyl group (HA-POSS) or vinyl groups (OL-POSS). Silsequioxanes were incorporated into the silicone rubber matrix in a quantity of 3 and 6 parts by wt by the method of reactive stirring with the use of a laboratory mixing mill. Based on the analyses performed by TG (Thermogravimetry) FTIR (Fourier Transform Infrared Spectroscopy), conical calorimeter, and SEM-EDX (Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy) methods, the thermal degradation mechanism of non-cross-linked and cross-linked silicone rubber has been elucidated. The effects of POSS, and POSS in a synergic system with melamine polyphosphate (MPP), on the thermal properties and flammability of silicone rubber composites were presented. Based on the test results obtained, a mechanism of flame retardant action POSS and POSS-MPP has been proposed. It has been shown that POSS, especially with MPP, considerably increases the thermal stability and decreases the flammability of the SR rubber composites under investigation.

Aluminum-Magnesium Hydroxycarbonate/Azo Dye Hybrids as Novel Multifunctional Colorants for Elastomer Composites.

This study presents the preparation and characterization of new organic-inorganic pigments based on aluminum-magnesium hydroxycarbonate (LH) and azo dyes. Solvent resistance studies, XRD, SEM, and TGA confirmed the successful formation of hybrid pigments, which were characterized in terms of their physicochemical properties. The new hybrid pigments were applied in acrylonitrile-butadiene (NBR) and ethylene-propylene (EPM) rubber composites and cured with sulfur and peroxide curing systems, respectively. The mechanical properties, dispersion quality, and flame-retardant properties of the NBR/hybrid and EPM/hybrid pigment composites were determined by dynamic mechanical analysis (DMA), SEM, and microscale combustion calorimetry (MCC). Complex experimental investigations revealed that the layered nature of hybrid pigments could improve the barrier ability and flame retardancy of elastomer composites. In comparison to unmodified aluminum-magnesium hydroxycarbonate, the modified LH dye structures contributed to significantly decrease the heat release rate and the total heat release of the NBR and EPM composites, offering a new approach to imparting low flammability to elastomer materials.

Thermal Stability and Flammability of Styrene-Butadiene Rubber-Based (SBR) Ceramifiable Composites.

Ceramifiable styrene-butadiene (SBR)-based composites containing low-softening-point-temperature glassy frit promoting ceramification, precipitated silica, one of four thermally stable refractory fillers (halloysite, calcined kaolin, mica or wollastonite) and a sulfur-based curing system were prepared. Kinetics of vulcanization and basic mechanical properties were analyzed and added as Supplementary Materials. Combustibility of the composites was measured by means of cone calorimetry. Their thermal properties were analyzed by means of thermogravimetry and specific heat capacity determination. Activation energy of thermal decomposition was calculated using the Flynn-Wall-Ozawa method. Finally, compression strength of the composites after ceramification was measured and their micromorphology was studied by scanning electron microscopy. The addition of a ceramification-facilitating system resulted in the lowering of combustibility and significant improvement of the thermal stability of the composites. Moreover, the compression strength of the mineral structure formed after ceramification is considerably high. The most promising refractory fillers for SBR-based ceramifiable composites are mica and halloysite.