Synthetic Styrene-butadiene Rubber Research Articles

Evaluating exposure-response relationship in 1,3-butadiene and leukemia studies.

1,3-Butadiene (BD) exposure's link to leukemia is under regulatory scrutiny. The assessment methods for BD exposure risks have evolved from early animal and limited human studies to advanced exposure-response modelling with comprehensive quantitative data. The objec- tive of this study is to explore the nuances of exposure-response modelling, investigating how various statistical methods have influenced the quan- tification of exposure-response relationships. Although this study was not conducted as a formal systematic review, a search was performed in Medline/Pubmed to identify all human studies on leukemia risk assessment for BD exposure. This search included articles written in English. The electronic search spanned from inception of records until July 23, 2023, using the search term: "butadiene AND (leukaemia OR leukemia OR myeloid OR lymphoid)" and was restricted to human species. Focusing on the synthetic styrene-butadiene rubber (SBR) industry cohort study conducted by the University of Alabama at Birmingham, USA, this review evaluates various statistical models and factors influenc- ing exposure-response modelling. Peak exposures to BD may be more influential in the dose-response relationship than cumulative or long-term exposure. The authors recommend utilizing β-coefficients derived from the latest SBR study update, employing Cox proportional hazard modelling, non-lagged and non-transformed cumulative BD exposure, and adjusting for age and peak BD exposure. The study reveals that statistical model selection has a limited impact on the calculated dose-response effects. The significant variation in estimated cancer mortality values arises from additional assumptions needed for metrics like the excess leukemia risk or the occupational BD effective concentration. In con- clusion, this study provides insights into exposure-response modelling for BD exposure and leukemia mortality, highlighting the importance of peak exposures. The recommended statistical approach offers a reliable basis for regulatory risk assessment and public health population metrics. Int J Occup Med Environ Health. 2024;37(3):300-10.

Experimental Investigation of the Performance of SBR and RSS Materials as a Sliding Bearing Element

Conventional bearing systems and materials, which are important components of machine elements, have often failed to fulfil requirements, especially in places where sealing is required. In such cases, sliding bearings with PTFE- and NBR-based polymer and elastomer materials operating in water or oil are preferred. In this study, the performance of two alternative rubber-based materials, synthetic styrene butadiene rubber (SBR) and natural rubber smoked sheet (RSS), as a sliding bearing was experimentally investigated in terms of frictional resistance using pin-on-disc and pin-on-cylinder devices. In the study, very low friction forces emerged at low sliding speeds compared to PTFE and NR operating in water. The friction force values and friction coefficients obtained are presented in diagrams and tables.

An updated lymphohematopoietic and bladder cancers risk evaluation for occupational and environmental exposures to 1,3-butadiene

EPA designated 1,3-butadiene (BD) as a high priority chemical in December 2019 and is presently performing an evaluation under the Toxic Substances Control Act (TSCA). EPA's cancer dose-response assessment for BD was published in 2002 and was primarily based on a study on workers exposed to BD in the North American synthetic Styrene-Butadiene Rubber (SBR) Industry developed by the University of Alabama at Birmingham (UAB). EPA relied upon a Poisson regression of leukemia mortality data from this cohort (hereinafter referred to as the SBR study) to estimate the cancer potency of BD. At the time, the SBR cohort included more than 15,000 male workers that were followed up through 1991. The SBR cohort has undergone multiple updates over the past two decades. Most recently, Sathiakumar et al. (2021a, b) published an update, with 18 more years of follow up in addition to approximately 5,000 female workers and updated exposure concentration estimates. Recent EPA assessments (e.g., for ethylene oxide, USEPA 2016) based on epidemiological studies use Cox proportional hazards models because they offer better control of the effect of age in cancer development and are less restrictive than Poisson regression models. Here, we develop exposure-response models using standard Cox proportional hazards regression. We explore the relationship between six endpoints (all leukemia, lymphoid leukemia, myeloid leukemia, multiple myeloma, non-Hodgkin's lymphoma, and bladder cancer) and exposures to BD using the most recent exposure metrics and the most recent update of the SBR study. After adjusting for statistically significant covariates, an upper 95% confidence level on the cancer potency based on leukemia derived herein is 0.000086 per ppm, which is approximately 1,000-fold less than EPA's (2002) estimate of 0.08 per ppm and about 10-fold less than TCEQ's (2008) estimate of 0.0011 per ppm.

Comparative evaluation of Clusia multiflora wood flour, against mineral fillers, as reinforcement in SBR rubber composites

Clusia multiflora sawdust (CMS) was evaluated as filler in rubber composites. CMS at 40 phr was mixed with synthetic styrene butadiene rubber (SBR 1502), the blend was compatibilized with 8 phr of maleated polyethylene (MAPE). To evaluate the curing and mechanical behavior of CMS, it was compared with precipitated silica (reinforcing filler); calcium carbonate and kaolin (non-reinforcing minerals). The addition of CMS reduced the mechanical properties of rubber compound compared to silica rubber/silica composite. The tensile and tear strength values for SBR/CMS were similar to SBR/CaCO3 and SBR/kaolin. The addition of MAPE to SBR/CMS composite slightly improved the tensile strength, tear strength, abrasion resistance and hardness. In general, CMS performed as diluent filler which reduced the weight of the composite. CMS slightly affected curing speed of SBR/CMS blends. CMS is a waste generated by the use of Clusia multiflora (a timber species endemic of mountains region of Colombia) in the furniture industry. The novelty of this research consists of evaluating the CMS as an alternative to mineral fillers in rubber compounding to improve its mechanical properties, seeking to contribute to the sustainability and to reduce environmental impacts.

ON THE IMPACT OF SILICA AND BLACK CARBIDE IN IMPROVING THE ANTI-VIBRATION OF THE RUBBER BLENDS BASED ON NATURAL RUBBER (NR) AND STYRENE BUTADIENE RUBBER (SBR)

This paper presents some results on the survey of the impact of silica and black carbide on the mechanical – physical properties and vibration resistance of the rubber blended on natural rubber (NR) and synthetic styrene butadiene rubber (SBR), for application in manufacturing diesel engine mounts. Based on this research, the article also introduces some results in building up anti-vibration rubber and the process of diesel engine mounts manufacture. Development of the method to test the vibration resistance of the diesel engine mounts has initially resulted in some good results such as the natural frequencies are lower than 20 Hz and the damping factor is higher than 10.

High Performance Concrete Improvement by Styrene-Butadiene Rubber Addition

In this paper, the properties of high performance concretes modified by polymer were studied. Liquid synthetic styrene-butadiene rubber (SBR) was added (5%, 10% and 15%) by weight of cement to high performance concrete (HPC) to elucidate the effect of the polymer additive to their properties.The compressive strength, splitting tensile strength, flexural strength, porosity, dry density and total water absorption were measured.Thermal conductivity, thermal diffusivity and specific heat of HPC isalso measured. In addition, SEM micrographs are compared reference and polymer modified HPC.The results show that there is an improvement in the workability for HPC after the addition of the polymer. Furthermore, the density of the set concrete was increased and both the porosity, total water absorption was decreased. Thermal conductivity, thermal diffusivity, and specific heat show improvement after polymer addition, which indicate better endurance.The SBR modified HPC, exhibits a significant improvement in splitting tensile strength and flexural strength, although it was at the expense of the compressive strength to some extent.The HPC has shown balanced microstructure before and after the addition of polymer, although they noticed improved on the ductile properties.

Relationship on research publications and productivity-export volumes for natural rubber

This article investigated contributions of natural rubber (NR) research through research articles and patents in Science Citation Index Expanded (SCI-Expanded) and SCOPUS databases and related the results with productivity-export volumes during 2002–2006. 1,771 research papers and 5,686 patents on “natural rubber” were retrieved from the databases. The results revealed that the top five countries produced the NR raw material by the order of productivity volumes were Thailand, Indonesia, Malaysia, Vietnam and China whereas those produced the synthetic rubber were the United States, China, Japan, Russia and Germany. Among the top three countries for NR production, Malaysia became a NR producer for its own use, whereas Thailand and Indonesia still had higher export volumes. Research articles and patents on natural rubber had contribution shares of about 20.9% and 47.5% of all rubber publications, respectively. The patents on natural rubber were found to increase with time while the research articles remained unchanged. Journal of Applied Polymer Science was the most preferable for publishing the research papers on rubbers. Eight countries ranked in the top countries for contributing the research articles on natural rubber were the United States, India, Malaysia, France, Germany, Thailand, Japan and China, similar country distributions being also found for research articles on synthetic styrene-butadiene rubber except for Thailand and Malaysia. No linear relationship between the productivity-export volume and research publication number was observed, but the results implied that the growth rate for commercializing the rubber was greater than that for research and development of natural rubber. Most NR research works focused on neat NR, which was contributed the most by USA while NR blend and NR composite papers were mainly published by Indian researchers.

Fast and Robust Method for the Determination of Microstructure and Composition in Butadiene, Styrene-Butadiene, and Isoprene Rubber by Near-Infrared Spectroscopy

In the tire industry, synthetic styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR) elastomers are essential for conferring to the product its properties of grip and rolling resistance. Their physical properties depend on their chemical composition, i. e., their microstructure and styrene content, which must be accurately controlled. This paper describes a fast, robust, and highly reproducible near-infrared analytical method for the quantitative determination of the microstructure and styrene content. The quantitative models are calculated with the help of pure spectral profiles estimated from a partial least squares (PLS) regression, using (13)C nuclear magnetic resonance (NMR) as the reference method. This versatile approach allows the models to be applied over a large range of compositions, from a single BR to an SBR-IR blend. The resulting quantitative predictions are independent of the sample path length. As a consequence, the sample preparation is solvent free and simplified with a very fast (five minutes) hot filming step of a bulk polymer piece. No precise thickness control is required. Thus, the operator effect becomes negligible and the method is easily transferable. The root mean square error of prediction, depending on the rubber composition, is between 0.7% and 1.3%. The reproducibility standard error is less than 0.2% in every case.

Surface Characterization of Chlorinated Synthetic Vulcanized Styrene-Butadiene Rubber Using Contact Angle Measurements, Infra-Red Spectroscopy and XPS

The surface of a sulfur-vulcanized synthetic styrene-butadiene rubber (SBR) was treated with ethyl acetate solutions containing different amounts of trichloroisocyanuric acid (TCI). The chlorinated SBR surfaces were characterized using contact angle measurements (water, ethane diol, n-hexadecane), infra-red (IR) spectroscopy and XPS. Chlorination produced an increase of surface free energy which was mainly due to the enhancement of the acid-base component of the surface free energy, which remained almost unchanged when the amount of TCI was increased. Depending on the amount of chlorination agent, several chemical species were present on the SBR surface: i) For low amounts of TCI (up to 2 wt%), mainly chlorinated hydrocarbon and C – O species were present on the surface; ii) For medium amounts of TCI (between 2 and 5 wt%), an excess of unreacted TCI remained on the surface and a relatively small amount of isocyanuric acid was deposited; iii) For high amounts of TCI (larger than 5 wt%), a weak boundary layer (mainly composed of isocyanuric acid) was formed on the surface and thus the effects due to chlorination were decreased. There was good agreement between the experimental results obtained with contact angle measurements and XPS because both provided information on a surface region close to 100 Å, whereas IR spectroscopy results showed deeper penetration of the chlorinating agent into the SBR surface. The estimated thickness of the chlorinated layer was near 5000 Å as estimated from XPS measurements of SBR surfaces modified by argon ion bombardment.