Rubber Samples Research Articles

Thermogravimetric Analysis of Rubber for Forensic Purposes: A Case Report

The main objective of this study was to determine the inorganic elemental components and thermal behavior of rubber samples collected from crime scenes and to compare them with a control sample. Thermal decomposition study revealed that decomposition temperature of rubber samples by TGA collected from crime scene exhibit 1 and 2 were consistent with decomposition temperature of control rubber sample exhibit 3. The DSC analysis showed that the decomposition temperature of the rubber samples exhibits 1 and 2 were 378.3 and 377.1 0C, respectively, consistent with that of the control sample exhibit 3 (378.8 0C). The micro-XRF analysis showed that elemental composition of rubber samples exhibits 1 and exhibit 2 matched with that of control sample exhibit 3. Thermal analysis was shown to be an important tool for characterizing the thermal behavior of rubber samples. Rubber samples collected from the scene of the crime with the rubber sample from the suspect’s vehicle can prove very valuable objective evidence.

How the Crosslinking Agent Influences the Thermal Stability of RTV Phenyl Silicone Rubber.

In this work, a thermal degradation mechanism of room temperature vulcanized (RTV) phenyl silicone rubber that was vulcanized by different crosslinking agents was discussed. Firstly, RTV phenyl silicone rubber samples were prepared by curing hydroxyl-terminated polymethyldiphenylsiloxane via three crosslinking agents, namely, tetraethoxysilane (TEOS), tetrapropoxysilane (TPOS), and polysilazane. Secondly, the ablation properties of RTV phenyl silicone rubber were studied by the muffle roaster test and FT-IR. Thirdly, thermal stability of the three samples was studied by thermogravimetric (TG) analysis. Finally, to explore the thermal degradation mechanism, the RTV phenyl silicone rubber vulcanized by different crosslinking agents were characterized by TG analysis-mass spectrum (TG-MS) and pyrolysis gas chromatogram-mass spectrum (pyGC-MS). Results showed that the thermal stability of RTV phenyl silicone rubber is related to the amount of residual Si–OH groups. The residual Si–OH groups initiated the polysiloxane chain degradation via an ‘unzipping’ mechanism.

Role of Divalent Metal Ions on the Basic Properties and Molecular Chains of Natural Rubber

Metal ions are a kind of components that cannot be completely removed in natural latex, which have an important influence on the basic quality of natural rubber, such as ash, impurities, Wallace plasticity value, plasticity retention index, etc. The six kinds of common divalent metal ions in natural rubber including calcium ion, magnesium ion, copper ion, manganese ion, iron ion and zinc ion are targeted to explore their influence on the storage characteristics of natural rubber. The fresh latex was added the designed divalent ions, then became the raw natural rubber via some procedures such as solidification, drying. Based on divalent metal ion and their content, the storage characteristics of natural rubber and the microstructure of corresponding natural rubber sample were examined. Wallace plasticity value (P0), Plasticity retention index (PRI), accelerated storage-hardening number (ΔP) of the resultant samples were tested. The tensile strength, and rubber molecular weight were also determined to explore the effects of different divalent metals on the structural changes of natural rubber. In the experiment, the blank control group was designed. Through the contrast analysis with the blank control group, it was found that the storage stability of the raw rubber depends on not only the type but also the content of divalent metal ions.

Py-GC/MS analysis of tyre rubber in traffic accident cases

ABSTRACTTyre rubber residue is a common trace material used as evidence in certain traffic accidents. The composition of tyre rubber varies among different vehicles. In this article, 76 tyre rubber samples of different brands and vehicle models were analysed by Py-GC/MS. The chemical structure of the main characteristic pyrolysis product was also identified. The tyre rubber samples were then classified according to the characteristic pyrolysis products of the rubber materials. Comparative analysis on the samples of the same class was conducted according to the similarities and differences between the relative contents of their pyrolysis products.

Assessment of failures of nitrile rubber vulcanizates in rapid gas decompression (RGD) testing: Effect of physico-mechanical properties

Rapid gas decompression (RGD) test is used to evaluate structural failures such as bubbles, blisters, internal and external cracks in rubber vulcanizates exposed to gas environment under high pressure and high temperature (HPHT) conditions. Physico-mechanical properties of vulcanizates may greatly affect the RGD resistance of rubber products. In this study, effect of the most important physico-mechanical properties such as hardness, modulus, elongation at break, tensile strength, tear strength, compression set and crosslink density of nitrile rubber (NBR) samples cured by different sulfur curing systems including conventional system (CV), semi-efficient system (SEV) and efficient system (EV) on RGD resistance has been investigated. Results showed that the type of sulfur curing system and resultant physico-mechanical properties had pronounced effects on RGD resistance. The NBR rubber samples prepared by CV system exhibited highest failures under RGD testing. Moreover, by increasing crosslink density, hardness and modulus of NBR vulcanizates, the internal cracks were increased during RGD test. Furthermore, the RGD resistance was improved at higher tear strength of rubber samples. Also, lower compression set specially in CV curing system and higher tensile strength of NBR samples lead to less structural failures.

THE EFFECT OF NON-POLYMERIC COMPONENTS OF A RUBBER MIXTURE ON SURFACE PROPERTIES OF ELASTOMER COMPOSITIONS

The effect of non-polymeric components of a rubber mixture on the surface properties of butadienestyrene rubber obtained by solution polymerization was studied in the article. As non-polymeric components, ingredients widely used in the practice of the rubber industry were introduced into the rubber: fillers, surfactants of various types, and also sulfur - as a vulcanization agent. The surface free energy of the samples, a quantitative characteristic of the surface properties, was determined using the Owens-Wendt-Rabel-Kaelble method. It has been found that the surface properties of elastomeric compositions depend significantly on the solubility of the ingredients of the rubber composition and their adsorption properties. It has been shown that the most significant influence on the surface energy of butadiene-styrene rubber is exerted by the filler, on the surface of which rubber adsorption does not occur. The effect of surfactants on the surface energy of rubber compounds is different and depends on the nature of the surfactant. A partially soluble component - sulfur - in small quantities does not affect the surface energy of rubber samples. However, if it is present in the system in quantities greater than the solubility limit, it significantly reduces the surface free energy of the samples.

Stick-slip frictional instabilities of rubbers on oiled glass surfaces

Abstract This work proposes an analytical model for the stick-slip friction of a solid mass on oiled surfaces. The dynamic friction was described as Fd = λAv, where λ is a parameter related to the surface conditions, A is the contact area and v is the sliding velocity. A mass-spring system with a dashpot with damping constant c (=λA) was used to determine the slip motions of the solids. The applicability of the model is examined by comparing the experimental slip displacements of rubber samples on oiled smooth glass surfaces. The model represents the important aspects of slip motions and suggested that an abrupt change in the acceleration force from positive to negative magnitudes was responsible for the unstable stick-slip phenomenon.

Inspection of internal filler alignment in visibly opaque carbon-black–rubber composites by terahertz polarization spectroscopy in reflection mode

As the industrial utilization of polymeric materials is increasing owing to recent improvements in material durability and functionality, product safety becomes an important issue. Therefore, various inspection methods for polymeric materials are being developed. In this work, the rapid and non-destructive inspection of the averaged internal orientation of conductive carbon black fillers in rubber composites is demonstrated using a handmade high-speed terahertz polarization spectroscopy system that employs reflection geometry. From the birefringent information obtained from the black rubber sample (with arbitrary stretching condition), the internal orientation of the conductive fillers, which plays an essential role in the properties of the rubber composite, was determined. In addition, since data acquisition with the reflection method is fast, the spatially resolved measurement of the filler orientation could also be performed. The information of the internal orientation of the carbon black fillers allows verification of the condition of the rubber product.

A Characteristic of Selected Properties of Vulcanised Rubber Elements Used on the “Izabel” Inland Vessel

Abstract Vulcanised rubber as a complex system is made from the basic component being virgin rubber and various components amounting to 10-15 per cent or even more. The material gains its most valuable properties in the final phase of processing i.e. vulcanisation. In mechanical as well as automotive engineering it is important for vulcanised rubber to be resistant to grease, oil and fuel in high operating temperatures. Being one of the very valuable isolation materials, vulcanised rubber is also characterised by dielectric and elastic properties as well as distinguished resistance to operating conditions (high/low temperature, weather conditions). All the above mentioned applications of vulcanised rubbers are also found in the shipyard industry. Their use is also very much predicated on the properties such as: ability to attenuate mechanical vibrations, high elasticity, considerable elastic deformability under static and dynamic loads, low permeability of water and gas, resistance to various chemicals, and other. The purpose of this article was to determine the hardness of vulcanised rubber samples obtained from various places on the “Izabel” inland barge. The scope of the study covered sampling and preparing the samples for testing (i.e. cleaning and degreasing the samples). Then, the hardness of the samples was measured using the Shore hardness test. The first part of the article presents the general concept of vulcanised rubber, its main components, properties, applications, and ageing. The second part focuses on the research scope and measuring the hardness of vulcanised rubber samples obtained from the “Izabel” inland barge.

Properties Characterization of Vulcanized Natural Rubber Filled with Uncarbonized Particulate Cow Bone

This work investigates the effects of addition of 63 µm uncarbonized particulate cow bone as fillers in vulcanized natural rubber on the tensile properties, hardness and abrasion resistance of the composites. Cow bones were procured from an abattoir, cleaned, crushed, pulverized, ball milled and sieved to obtain the particles that passed through the 63 µm mesh size. Natural rubber composites materials were prepared varying the filler loading as 5, 10, 15 and 20 pphr respectively. The compounded rubber samples were cured in a hot press using compression moulding technique. The control sample was produced using 20 pphr of carbon black. The cured rubber samples were conditioned at room temperature for two weeks before they were characterized. The tensile strength and elastic modulus of the samples filled with cow bone increased with filler loading up to 15 pphr before they started decreasing. Carbon black reinforced sample possessed higher tensile strength, modulus and hardness than the samples filled with uncarbonized particulate cow bone. The hardness for all samples maintained an increasing trend with increase in the filler loadings. Particulate cow bone reinforced natural rubber offered higher elongation than carbon black reinforced samples. At 10, 15 and 20 pphr, cow bone reinforced composites exhibited higher abrasion resistance than carbon black filled sample. The optimal filler loading of uncarbonized particulate cow bone reinforced natural rubber was 15 pphr. Cow bone reinforced natural rubber can find applications in areas where moderate strength, hardness, elongation and wear resistance are required such as in protective footwear, bouncing balls and cases of children toys.Keywords— carbon black, cow bone, fillers, natural rubber, composites.

Performance evaluation of alumina trihydrate and silica-filled silicone rubber composites for outdoor high-voltage insulations

In recent years, silicone rubber-based composites have been widely investigated for outdoor applications due to their promising insulating properties. However, mechanical, thermal, and tracking properties of pure silicone rubber are very poor, which restrains its application for long-term performance. In this research work, the influence of microsized alumina trihydrate (ATH) and micro/nanosized silica (SiO$_{2})$ fillers on mechanical, thermal, and electrical properties of room temperature vulcanized silicone rubber (RTV-SiR) has been studied. SiR-blends with varying amounts of ATH and SiO$_{2}$ particles were prepared by blending in a two-roll mixing mill, compression molding, and postcuring processes in sequence. In order to evaluate relative tracking and erosion resistance of SiR-blends, an inclined plane test (IPT) was conducted in accordance with the ASTM D2303 standard procedure. Surface temperature distribution was recorded using a Fluke-Ti25 infrared camera during IPT experiments. Thermogravimetric analysis was carried out to analyze the thermal stability of ATH and silica-filled silicone rubber samples. Tensile strength, percent elongation at break, hardness, erosion, tracking resistance, and thermal properties were also investigated and discussed. Results showed that the mechanical, thermal, tracking, and erosion performances of SiR-blends are improved by the incorporation of ATH and silica particles, which is governed by filler type, size, and wt. % in the polymer matrix.

Chemical and Physical Characterization of Tire Crumb Rubber Used in Synthetic Turf Fields to Improve Exposure Assessment

Tire crumb rubber from recycled tires is widely used as infill material in the 12,000+ synthetic turf fields in the United States. Tire crumb rubber is a complex material, with many potential chemical substances, presenting challenges for assessing human exposures. As part of U.S. Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields and Playgrounds, researchers collected tire crumb rubber samples from nine tire recycling plants and infill from 25 outdoor and 15 indoor synthetic turf fields across the U.S. Fields were recruited from all four U.S. census regions, and ranged in age from new installations to 12 years old. Multiple analytical methods were applied to measure a wide range of metals, VOCs, and SVOCs. Particle sizes were characterized using gravimetric and SEM methods. Microwave acid digestion of tire crumb rubber with ICP-MS analysis was used to measure 20 elements. Tire crumb rubber was solvent extracted for analysis of approximately 50 PAHs, phthalates, thiazoles, and other rubber chemicals by GC/MS/MS and LC/TOFMS methods. Dynamic emission chamber testing was performed for VOCs and SVOCs at 25° and 60°C. Suspect screening and non-targeted analysis approaches were applied to assess the larger range of VOCs and SVOCs that may be associated with the material. Bioaccessibility of metals from tire crumb rubber was measured using simulated saliva, sweat, and gastric fluids. The range and variability in chemical substances measured within and between recycling plants and synthetic turf fields was examined. Differences in measurements among indoor and outdoor fields and fields with different age and region characteristics were assessed. This presentation will focus on key results from the application of this array of analytical methods, with a goal of improving our understanding and knowledge for assessing synthetic field user exposures.

Interpretation of surface degradation on polymeric insulators

Abstract Silicone rubber based polymeric insulators are being used widely used as outdoor insulation for high voltage applications. However, their long-term service life performance is highly dependent on local environmental conditions that cause deterioration of material properties of the insulators. In the present work, tracking and erosion studies are conducted on silicone rubber samples using. Inclined Plane Tracking (IPT) and Erosion method based on IEC 60587. The contaminants used to simulate different environmental conditions are as per standard and in addition acidic rain composition is used. Leakage current flowing through samples was continuously monitored and recorded over the experimental duration. The consequence of leakage current variation is analyzed using. Recurrent Plot (RP) Analysis and this resulted in variation of quantitative parameters Recurrence Rate (RR), Determinism (DET), Entropy (ENT) and Length (L) these are used to interpret the tracking and erosion performance of silicone rubber samples. Further, physico-chemical analysis is conducted using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX) and Fourier Transform Infra-Red (FTIR) spectroscopy to observe surface morphology and chemical changes happened in the samples. Thermo-Gravimetric Analysis (TGA) is performed to observe thermal stability and presence of Aluminum Tri-hydrate (ATH) fillers before and after experiments. The investigations show RP method as a potential tool for detection and diagnostic of polymeric insulators.

Swelling of samples of automotive rubber products in standard fluid, engine oil and tribotechnical compound

In this paper the change in the properties of rubber products of automobile under the influence of temperatures and when working in an aggressive environment was studied by authors. The radial tire protector samples (Barum 155/70 R13 75T Brillantis 2) with dimensions not exceeding 2×10-2×1.5×-2×5×10-3 [m], seal samples (of 2108-170342-01 type) in the form of a semicircle of 2.7·10-2×7·10-3×2·10-3 [mm] size, both original and aged rubber samples were tested. Aging was carried out in a stream of air, forcibly pumped through the reactor with the rubber placed in it. The heat treatment time was 12-100 hours, the temperature was 70-150 ° C. The change in the properties of rubber was evaluated by the parameter of the change in the mass of the samples (original and aged) after their contact with the liquid. The resistance of rubber to the action of liquids was studied, the kinetics of rubber swelling was studied. As the standard liquid the isooctane (2,2,4-trimethylpentane) was used. The experiments were carried with synthetic engine oil (SEO) “GENESIS CLARITECH” 5W-30 and tribotechnical composition (tribotechnical compounds; TC) “ACTIVE PLUS” (“suprotec”). The use of tribotechnical composition as a test fluid for rubbers was motivated by the purpose of assessing the chemical activity of the “suprotec”, when used in engines operating under conditions of high loads. The kinematic viscosity of SEO and TC was determined (in the temperature range from 20 ° C to 100 ° C) by the HPLC-4 viscometers, the density (ρ) of the liquids was measured with oil-meters. The hardness of the rubber samples was evaluated by measuring the resistance of the rubber by immersion of the indenter (a spring-loaded rod) into it. The indicator of the hour type ICh-02 (accuracy class 0) was used as a gauge.

Performance evaluation of carbonized rubber seed shell (CRSS) filler as reinforcer in rubber binder

The use of rubber-seed shell as a raw material for the production of carbonized filler was investigated. The produced carbonized rubber seed shells (CRSS) waste were characterized by its particle size, density and FTIR value. In this study, the effect of CRSS on the rheological and mechanical properties of rubber had shown great changes and nearly meet the properties of conventional used of filler which is carbon black. Five samples of rubber compounded with different loading of CRSS (0, 10, 15, 20 and 30 phr) were prepared. The higher filler loadings show increment in tensile strength, tensile modulus and hardness but decrease in elongation at break properties. At optimum CRSS loading (20 phr), the tensile strength and tensile modulus (M300) depict positive improvement. Meanwhile, the higher CRSS loading that have less developed structure also will worn the surfaces of rubber compound, thus result in decreasing abrasion resistance index (ARI) value as filler loading increase. This is due to higher CRSS loading will result in poor interaction between rubber matrix and filler content. Lastly, crosslinked density via Flory-Rehner equation depicts solvent uptake decrease linearly by adding more CRSS filler. Therefore, from the conclusive data and observations, the produced CRSS as alternative to current rubber black has great potential to be used as reinforcement filler in rubber compounding along with commercializing the waste materials to the next level.

Characterization of thermal decomposition and combustion for commercial flame-retardant rubber floor cloth in TG–FTIR and FPA

The commercial flame-retardant rubber samples were investigated in a TG–FTIR with different heat rates and fire propagation apparatus under different external heat fluxes to study thermal and fire characteristics, respectively. The thermal decomposition, ignition time, heat release rate, limiting oxygen concentration, mass loss rate and CO/CO2 yield qualitatively and quantitatively are analyzed, respectively. It was found that the second main reaction of sample was the main decomposition process. The sample was recognized as thermal thin material. The first peak heat release rate of commercial flame-retardant rubber was lower than the second one due to the internally formed charred layer, and the sample would break into two pieces when the external heat flux was less than 40 kW m−2. The limiting oxygen concentration of sample was gradually reducing with external heat flux increasing. The mass loss rate was effected by radiation heat blockage, thus the increase rate of mass loss rate would reduce under higher external heat flux. CO yield increased first and then decreased with the heat flux increasing. These data and models could be used to evaluate the fire risk of flame-retardant rubber for high-speed train department.

Morphology and micromechanics of liquid rubber toughened epoxies

Abstract In the present work, a diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin was modified with the help of a liquid rubber (LR) obtained from the pyrolysis of rubber. Tensile tests on samples of rubber modified epoxy resins (REs) containing varying rubber volume fractions (RVF) were conducted to obtain their tensile properties. Fractographic analysis of fractured samples using field emission scanning electron microscopy (FESEM) revealed the presence of phase separated rubber zones characterized by microvoids, distributed uniformly in the epoxy domain. Young’s modulus and yield strength of REs were observed to drop with RVF. A three-dimensional (3D) finite element model was employed to predict the elastic properties and stress distributions in REs. Various stress distributions and their dependence on the properties of rubber were examined in detail through the model. The effect of rubber properties on bulk elastic properties of the REs were also studied. Lastly, the effective stress-strain relationship was predicted with the help of an elastic-plastic analysis. Predicted results showed coherence with experimental results.

Direct replication of micro-nanostructures in the fabrication of superhydrophobic silicone rubber surfaces by compression molding

We describe a simple method for fabricating superhydrophobic high temperature vulcanized (HTV) silicone rubber surfaces by direct replication using a compression molding system. The resulting rubber samples possessed micro-nanostructures on the surface. This micro- and nano-scale roughness produced a water contact angle of >160° and a contact angle hysteresis of <3°. The roughness patterns on chemically etched aluminum surfaces, which served as templates, were successfully replicated on the rubber surfaces. An antistiction coating applied to the template surface ensured that the rubber was completely removed during demolding and that the replicated micro-nanostructures on the silicone surface were preserved. Surface roughness of the aluminum templates was optimized at HCl concentrations of 15 wt.%, with a lower roughness value observed at acid concentrations above and below this value. The developed HTV silicone rubber surfaces also demonstrated a freezing delay and a self-cleaning capacity.

Viscoelastic maps obtained by nanorheological atomic force microscopy with two different driving systems

We previously developed nanorheological atomic force microscopy (AFM) that enables dynamic nanorheological mapping in a wide frequency range. We have used it for investigating the reinforcing mechanism of various filled rubber materials in more detail. However, in this type of nanorheological AFM, temperature control is difficult. In order to solve this serious problem, we changed the driving system of the instrument from a stage-driving system to a probe-driving system. In this study, we compare these two driving systems by measuring the viscoelastic properties of styrene-butadiene rubber (SBR) vulcanizate as a model rubber sample and also show the result obtained by the new type of nanorheological AFM with the probe-driving system with temperature control capability.

Investigation of the mechanical, thermal and transport properties of NR/NBR blends: impact of organoclay content

In the present study efforts have been made to prepare organoclay nanocomposites of NR/NBR (natural rubber/nitrile rubber) blends using 0-4 wt% cloisite 93A by mixing on a laboratory type two-roll mill as per ASTM procedure. The organoclay-filled NR/NBR blends exhibited high tensile strength due to the formation of inter-phase crosslinks. The modulus values were also found increase in line with tensile strength. The clay platelets could be aligned in the direction of stretching of the rubber sample and the strong interfacial interaction between the NR and the NBR chains and the clay platelets could support local load transfer, resulting in enhanced modulus. The results of Scanning Electron Microscopy (SEM) fractographic analysis were in agreement with the mechanical test results and support the observed changes in the NR/NBR blend properties as the clay content increases. Transmission Electron Microscopy (TEM) images showed intercalated clay layers in both phases of the blend, indicating good compatibilization. Crosslink densities of the vulcanized samples exhibited an increase in the values on the increase in dosage of the nanoclay, supporting the fact that high specific surface area of the layered silicates enhanced reinforcement of the polymer matrix.