Manufacture Of Rubber Products Research Articles

Unveiling the surface of carbon black via scanning probe microscopy and chemical state analysis

Carbon black (CB) has wide range of industrial applications, including in the manufacturing of automobile tires, rubber products, inks, and plastics. To improve the properties of the target products and establish recycling systems, it must be fully characterized. However, characterization of CB is challenging owing to its structural complexity and the limitation of conventionally used experimental techniques, especially for surface structures at the nanoscale. In this study, we characterized the surface structures of two commercial CB via atomic force and scanning tunneling microscopy. Analysis of well-dispersed aggregates on atomically flat solid surfaces revealed primary particles of diverse sizes. The particle surfaces lacked edges, grooves, and steps that should be observed between stacked graphene sheets, which contradicts the widely accepted crystallite model. Observed images suggest that the graphene sheets exhibit a size distribution, inferring that multiple non-uniformly sized small graphene sheets are stacked turbostratically, with each sheet displaying a localized curvature rather than the ideal planar form. Varying size of sheets and curvature indicate the presence of a decent number of edges terminated with hydrogen and oxygen-containing functional groups. This interpretation was corroborated by conventional spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and infrared absorption spectroscopy.

Evaluation of Energy Performance Indicators and Energy Saving Opportunities for the Italian Rubber Manufacturing Industry

The objective of this work is the energy characterisation and evaluation of the energy efficiency potential of the rubber manufacturing industry in Italy, exploiting the detailed data included in energy audits by large and energy-intensive companies. This sector is divided into two sub-activities: the manufacture of rubber products and the production of tyres. Existing studies are focused mainly on tyre production, and there is a lack of quantitative evaluation of energy indicators that can provide guidance for improving process efficiency. In this work, updated global and specific energy performance indicators (EnPIs) related to the production process and to the auxiliary and general services are defined and evaluated. At the same time, targeted actions and interventions to improve the energy efficiency of the sector are analysed, showing the role of different intervention areas and their cost-effectiveness. The analysis is based on 100 Italian mandatory energy audits of the sector collected according to Art.8 EU Directive 27/2012. The applied methodology made it possible to calculate specific energy performance indicators by considering the overall and sub-process energy consumption of different production sites. Based on a detailed database containing real data from recent energy audits, this study provides an up-to-date and reliable benchmark for the rubber industry sector. In addition, the analysis of energy audits allows the identification of the most effective energy efficiency interventions for the rubber industry in terms of cost-effectiveness and payback time.

Determinants of efficient water use and conservation in the Colombian manufacturing industry using machine learning

Water is a fundamental aspect of achieving sustainable industries, and it is essential for firms to make efficient use of it. However, not all companies have sustainable water management practices in place. In this study, we aim to answer the research question: What factors influenced the efficient use and saving of water in the Colombian manufacturing industry in 2020? We used data from the Annual Manufacturing Survey and the Industrial Environmental Survey conducted by DANE to investigate this question. Our study grouped the variables into four categories: Environmental commitment, Risk mitigation, Innovation, and Location. We used two supervised learning machine-learning algorithms—decision tree and logit regression with LASSO regularization—to analyze the data. The results underscore those investments in wastewater treatment, total water consumption, and commitments to air and climate protection emerge as pivotal drivers for embracing sustainable practices. Moreover, the geographical location of companies significantly influences the likelihood of implementing water conservation initiatives. To enhance efficient water use and conservation in the Colombian manufacturing sector, several targeted public policies are recommended. These include offering fiscal and financial incentives to encourage investments in advanced wastewater treatment and reuse technologies. Additionally, advocating for specialized training and environmental education programs tailored for corporate personnel is crucial. Moreover, establishing initiatives for environmental certification and eco-labeling within the corporate sector can significantly promote sustainable water practices. Lastly, enforcing more stringent environmental regulations and standards, especially for industries like Textile, Metallurgy, and Manufacturing of rubber and plastic products, is essential to ensure responsible water management across the sector.

Spherical CaCO3: Synthesis, Characterization, Surface Modification and Efficacy as a Reinforcing Filler in Natural Rubber Composites

Natural rubber (NR), an important natural polymer derived from the Hevea brasiliensis tree, has been widely used in the rubber industry owing to its excellent elastic properties. However, it requires reinforcing fillers to improve its mechanical properties for the manufacturing of rubber products. Generally, calcium carbonate (CaCO3) is employed as a non-reinforcing filler. This work aimed to synthesize spherical-shaped CaCO3 at a submicrometric scale without and with surface treatment and explore its utilization as a reinforcing filler in NR composites. The morphological shape and polymorphic phase of CaCO3 were investigated using SEM, TEM, XRD, ATR-FTIR and Raman techniques. The mechanical properties of various amounts (0 to 60 phr) of CaCO3-filled NR composites were explored. As a result, the NR/treated CaCO3 composites provided higher tensile strength than the NR/untreated CaCO3 composites and pure NR at all filler loadings. This may have been due to the improved interfacial interaction between NR and CaCO3 with the improved hydrophobicity of CaCO3 after treatment with olive soap. The optimal filler loading was 20 phr for the highest tensile strength of the rubber composites. In addition, the elongation at break of the NR/treated CaCO3 was slightly decreased. Evidence from SEM and FTIR revealed the vaterite polymorph and shape stability of CaCO3 particles in the NR matrix. The results demonstrate that the particle size and surface treatment of the filler have essential effects on the mechanical property enhancement of the rubber composites. Synthesized spherical CaCO3 could be a potential reinforcing filler with broader application in polymer composites.

ISOLATION AND PURIFICATION OF ISOPRENE FROM CYCLOPENTADIENE

Isoprene is a basic monomer in the petrochemical industry. It is used in the synthetic rubber production for the manufacture of rubber products for the electrical, aviation and engineering industries, for the manufacture of food and medical products. In the Republic of Bashkortostan, Sintez-Kauchuk OJSC (Sterlitamak) produces isoprene by the two-stage dehydrogenation of isopentane with an annual product output of hundreds of thousands of tons. The disadvantage of this technology for producing isoprene is the significant content of impurities in raw isoprene, which seriously affect the kinetics of polymerization and the quality of the final product. Of all the impurities present in the monomer, cyclopentadiene is the most detrimental to the stereoregular polymerization process. Its content in isoprene should not exceed 0.0001 % wt. Due to the urgency of the problem, a technical solution was developed to remove cyclopentadiene impurities from monomers.Currently, there is a problem of accumulation of cyclopentadiene in the system of purification and treatment of isoprene at the operating production. The paper proposes to purify isoprene from cyclopentadiene before the stage of extractive distillation. This purification method allows to reduce the content of cyclopentadiene in the isoprene-isoamylene fraction from 0.10 % wt. to 0.00014 % wt, which reduces its concentration in all recycle flows of the isoprene isolation and purification system. To implement this solution, laboratory experiments were carried out to purify the isoamylene-isoprene fraction formed at the second stage of isopentane dehydrogenation. In order to assess the energy efficiency of the studied method for reducing cyclopentadiene, a computer model of the isoprene isolation and purification process was built in the Honeywell Unisim Design software environment.

Development of a Test Method for the Estimation of SBR-BR Blend Ratio in Tyre Tread Formulation and Validating It through Robust Statistical Tools

Blends of synthetic rubbers are widely used by rubber product manufacturing industries depending on the end use and product application. The estimation of individual rubber in blends is an important aspect to characterise the correctness of the mixing process. In tyre industry, Styrene butadiene rubber/Polybutadiene rubber (SBR/BR) blend is commonly used to achieve different performance properties, particularly for passenger car tyre. Out of the different quantitative analysis techniques to characterise the blend, one of the widely used techniques Gas Chromatography-Mass Spectrometry (GC-MS) has been used to develop and later validate a method to quantify the SBR/BR blend ratio. Through this GC-MS technique detection capability is measured, with a minimum limit of detection (LOD) of 5.17% and a limit of quantification (LOQ) of 15.67% Styrene butadiene rubber (SBR) in an SBR-BR vulcanizate. It is observed that the bias percentage is highest in case of a lower SBR content sample, i.e. 11.1% while in the case of other sets, it is varying from (–)1.4% to (+)1.5%. During the recovery study, it is observed that with increasing SBR content, recovery is also improving. All requirements for a successful method validation: Accuracy, precision, selectivity, detection capability, calibration range and robustness have been carried out in this entire work.

Preparation of skim natural rubber and polypropylene blends via melt blending: A study on physico-mechanical properties

High percentage of non-rubbers in Skim Natural Rubber (SNR) has restricted its use in manufacture of advanced rubber products. SNR were melt blended with polypropylene (PP) at different blend ratios to generate thermoplastic elastomers (TPEs). Standard Lanka Rubber (SLR) and PP blends were also prepared for the purpose of comparison. Tensile, hysteresis, hardness, water absorption, and dynamic mechanical properties of unvulcanized (UV) and dynamically vulcanized (DV) SNR/PP and SLR/PP blends were compared. Stress-strain behavior and TPE characteristics of both blends were similar. Tensile strength and modulus of SNR/PP blends decreased with the increase of SNR percentage. Elongation at break showed a decrease in UV blends and maxima at 50:50 blend ratio for DV blends. Dynamic vulcanization of the rubber phase improved tensile properties and hardness of the blends. Water absorption studies showed significantly higher equilibrium moisture content in SNR/PP blends, while difference in this property diminished with the increase of rubber phase. Water absorption and equilibrium moisture content decreased with dynamic vulcanization of rubber phase. Dynamic mechanical analysis confirmed multi-phase microstructure of the blends. Both blend systems showed similar dynamic mechanical properties and almost comparable thermo-mechanical properties confirming the potential of SNR as an alternative to SLR for selected applications.

Labour Productivity as a Factor of Tangible Investment in Companies Producing Wind Energy Components and Its Impacts: Case of Lithuania

This paper aims at justifying the significance of investment in the improvement of labour productivity (LP) and importance of the latter on economic performance of companies manufacturing wind energy components (WEC) in Lithuania in terms of value added (VA) created, profitability and wage earned. The time period covered is 2000–2020. The following methods have been employed: analysis of legal acts, programmes, strategies, and business structure and finance indicators, interdependence (correlation and regression), trend, case analysis, logical economical reasoning and graphical representation. The research results of current status analysis showed that the business of WEC manufacturing is small in regard to their variety of products but increasing in terms of VA and employment in Lithuania. Investment has been found as a driver of improvement in LP. The calculated historical ratio of change in LP to investment showed that, on average, after 1000 EUR per employee has been invested in tangible assets (TA), the LP increased by 0.13 EUR/h. A higher than average ratio was found in the manufacture of other transport and repair and installation of machinery and equipment (1.41), such as rubber, plastic and other non-metallic mineral products (0.17), but lower in the manufacture of electronic and communication (0.12) and metal (0.06) products. Taking into account the linear curves of LP to investment in TA curve and the average volumes of investment in different manufacturing activities, it is estimated that LP could grow by 5.3% a year in the manufacture of electronic products, and communication equipment are expected to increase by two-fold to 33 EUR/h in 2030, but it could grow only by 2.0% a year in the manufacture of rubber, plastic and other non-metallic mineral products to reach 28 EUR/h in 2030. Due to investment related changes in LP, the VA created by WEC companies could increase by 5.9% a year and account to 2.9 billion EUR during 2021–2030. Net profitability and real wages (and salaries) could also increase in future. Seeking to use the potential of companies to manufacture WEC for domestic wind installations and exports, investment supporting programmes are of high importance in the fields of promotion of innovations, development of human capital and adaptation of new technologies.

Lysozymes from natural rubber latex (Hevea brasiliensis): Assay development and recovery using ammonium sulphate and surfactant precipitations

To date, the C-serum and the bottom fraction of natural rubber latex (NRL) are still generally being considered as waste. However, they are rich sources of lysozyme, which is a bacteriolytic enzyme that has huge potential for biotechnological exploitations. So far, there are no reports on lysozyme recovery for the valorisation of NRL by-products. Therefore, this study aimed to (1) develop and validate a lysozyme assay based on the lysoplate method using the cloudy NRL sample and Micrococcus lysodeikticus cells and (2) recover lysozyme from the NRL fractions using ammonium sulphate ([NH4]2SO4) precipitation (direct and fractional modes) and the novel sodium di-(2-ethylhexyl) sulfosuccinate (AOT) surfactant precipitation. The assay developed in this study was high in both accuracy (97.54%) and precision (13.61% relative standard deviation). The detection and quantification limits, as well as the linearity range of the assay were 0.13 U/mL, 0.04 U/mL and 0-10,445.40 U/mL, respectively. As for the lysozyme recovery from the C-serum of NRL, the performance of the AOT precipitation via negative mode (activity recovery [AR] = 67.29%; purification factor [PF] = 2.42) was comparable (p > 0.05) to that of (NH4)2SO4 precipitation (direct mode: AR = 88.44%, PF = 2.18; fractional mode: AR = 95.44%, PF = 3.05). Meanwhile, for the lysozyme recovery from the bottom fraction of NRL, the AOT precipitation (AR = 71.94%; PF = 1.73) was shown to be superior than (NH4)2SO4 precipitation (direct mode: AR = 25.68%, PF = 3.23; fractional mode: AR = 27.88%, PF = 12.87). Hence, considering its effectiveness, simplicity, rapidity, as well as its great potential to be integrated with rubber product manufacturing, the AOT precipitation is an attractive alternative recovery method for lysozyme recovery from NRL. The findings described herein are significant for the development of a downstream processing scheme for lysozyme recovery from NRL.

Эконометрический анализ влияния монетарной политики на отрасли российской промышленности

This paper presents the econometric analysis of the heterogenous effects of monetary policy on industrial output and producer prices in manufacturing sector in Russia. The estimation of the differences in the impulce responses to the interest rate shock is conducted using structural VAR-models, the analysis of key industrial characteristics, explaining differences through monetary transmission channes, is based on principal components and correlations. Our findings reveal the strongest response to monetary policy in such industries as manufacture of rubber and plastic products, manufacture of non-metallic mineral products, manufacture of pulp and paper, manufacture of machinery nd equipment, manufacture of electrical, electronic and optical equipment and manufacture of motor vehicles and equipment. Besides, in these industries the response is usually deffered to 2–3 months after the shock. Our findings also show that the impact of monetary shocks on output is particulary strong in industries producing capital goods and supplies for construction but particularly weak in industries with high concentration and high profits. That means that differences in industrial responses to monetary policy can be described by two key channels of monetary transmission — interest rate channel (due to high demand sensitivity to interest rate changes) and bank lending channel (due to important role of bank loans in fi rms’ financing).

Industry Distribution Characteristics of Benzene-Exposed Workers with Cytopenia - Four Provinces, China, 2020.

Benzene is harmful to the hematopoietic system and can cause leukemia. However, benzene is still being used in various industries including furniture, rubber, plastic products, and metal product manufacturing. The white blood cell count of workers in general equipment, special equipment, chemical raw materials, and chemical products manufacturing decreased significantly. The enterprises in which benzene concentration exceeded the occupational exposure limit were small enterprises and private enterprises. Regular health examinations are necessary for benzene-exposed workers. In addition, the monitoring of benzene concentration in small enterprises and private enterprises should be strengthened.

Исследование сил при съеме тонких слоев строганием и фрезерованием

The problem of machining structural elements with removal of metal layers with thickness less than 0.01 mm by carbide tools, when the conditional radius of the blade rounding is less than or equal to the thickness of the cut layer, is considered. These cutting conditions can be considered constricted which requires research into cutting forces and chip shape. The problem of recording and measuring small cutting forces arising during blade machining of small grooves that serve for gas drainage in the manufacture of rubber products is solved. To measure forces, a lever fixed in a universal dynamometer, which has a supporting support with small friction, is used. Value of force moment measured with dynamometer can be used for optimization of cutting conditions, selection of tool geometry when processing small relief elements. Dependences of lever system cutting forces and displacements on the use of lubricant-cooling liquids, values of front angles during planing and milling with small-size tools are investigated. Experimental discrepancies between theoretical calculations of cutting forces according to classical and modern reference data and fixed results with the use of cutting liquids during cutting with small values of feed for carbide tools are found

Un modelo no-paramétrico y multidireccional en investigación cuantitativa

In this work, a non-parametric and deterministic approach based on multidirectional efficiency analysis (MEA) is presented. The proposed model involves MEA with other important mathematical techniques in data analysis, such as the calculation of the NC value for the analysis of groups with different levels of efficiency. This model allows us to examine the factors that influence the behavior of decision-making units in different contexts such as business efficiency, educational quality, energy efficiency, circular economy, among others. Particularly in this work, we show the results obtained in 1787 Portuguese companies in the materials manufacturing sector (manufacture of wood and paper; manufacture of rubber products, plastics and other non-metallic mineral products; manufacture of common metals and metallic products, except machinery and equipment) in an eight-year period (2006-2013) of study. The results allow, not only a characterization of the financial structure of the sector and a diagnosis through indices that identify the strategic positioning of companies in terms of efficiency scores; but also a characterization of the most efficient units and an analysis of the variables that must be addressed differently, to obtain better results, in terms of economic performance.

Emission Characteristics and Environment Impacts of VOCs from Typical Rubber Manufacture

The emission characteristics of VOCs from three typical rubber manufacture industries were studied by GC-MS/FID. Maximum incremental reactivity(MIR) and fractional aerosol coefficient(FAC) were employed to evaluate the ozone formation potential(OFP) and secondary organic aerosol(SOA) formation potential. The results show that the VOC types emitted from the manufacturing of rubber products mainly include alkanes, ketones, aldehydes, alcohols, and benzene series. For traditional rubber products manufactured through rubber mixing and vulcanization, the main pollutants are ketones and alcohols, whereas for production processes involving gluing and painting, the main pollutants belong to the benzene series. In terms of ozone impact, the traditional processes contribute to ozone formation mainly through oxygenated hydrocarbons. In industries that utilize adhesives and paints, the extensive use of these organic solvents lead to a significantly higher contribution of the benzene series than other VOC species to ozone formation; the benzene series account for 82.9% of the total contribution. In terms of SOA impact, the benzene series are the main contributor to SOA, whereas the contribution of VOCs from traditional processes is small; hence, SOA primarily originates from the gluing and painting processes. Therefore, in traditional production of rubber products through rubber mixing and vulcanization, the emission of oxygenated hydrocarbons should be preferentially controlled, whereas for rubber industries utilizing gluing and painting processes, the emission of benzene series should be preferentially controlled.

Influence of Chemically Modified Ultra-High Molecular Weight Polyethylene on the Properties of Butadiene Nitrile Rubber

For the manufacture of frost-resistant oil and petrol-resistant rubber products, one of the most widely used rubbers is nitrile-butadiene rubber (NBR) with a low acrylonitrile content of 17–20 %. However, the technical properties of its vulcanizates do not always meet all high performance requirements. Therefore, the study of the possibility of improving the technical characteristics of vulcanizates based on frost-resistant NBR is an urgent task. This paper presents the results of studying nitrile-butadiene rubber BNKS‑18AMN filled with ultra-high molecular weight polyethylene (UHMWPE). A feature of this work is the study of the possibility of increasing the technical properties of the obtained elastomeric composites by increasing the interaction between chemically inert UHMWPE and BNKS‑18AMN using the chemical modification of UHMWPE. The modification of UHMWPE was carried out by chemical etching in a solution of chromic acid for 3 and 20 hours. A complex of laboratory studies of the obtained samples was carried out. The influence of the duration of chemical etching of UHMWPE on the rheological and vulcanization properties has been studied on the analyzer of the processing of rubber. It is shown that the filling of UHMWPE into BNKS‑18AMN, in general, leads to an increase in the viscosity of the rubber compound. Chemical etching of UHMWPE leads to a decrease in the rate of vulcanization and the density of the three-dimensional spatial structure of the vulcanizate. The study of the physical and mechanical properties in tension, wear resistance during abrasion and swelling in standard hydrocarbon liquid for testing rubbers SZR‑3 showed that chemical etching of UHMWPE leads to a decrease in strength characteristics, but at the same time leads to an increase in resistance to abrasion and has no significant effect on swelling. The study of changes in the properties of samples after heat exposure showed that chemical etching of UHMWPE significantly reduces the resistance to thermal oxidative destruction in the presence of atmospheric oxygen, but does not affect the resistance to thermal aging in the SZR‑3 hydrocarbon environment

Incidence of acute myocardial infarction in the workforce: Findings from the Occupational Disease Surveillance System.

Increased risks of acute myocardial infarction (AMI) may be attributable to the workplace, however, associations are not well-established. Using the Occupational Disease Surveillance System (ODSS), we sought to estimate associations between occupation and industry of employment and AMI risk among workers in Ontario, Canada. The study population was derived by linking provincial accepted lost-time workers' compensation claims data, to inpatient hospitalization records. Workers aged 15-65 years with an accepted non-AMI compensation claim were followed for an AMI event between 2007 and 2016. Adjusted Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for each industry and occupation group, compared to all other workers in the cohort. Sex-stratified analyses were also performed. In all, 24,514 incident cases of AMI were identified among 1,502,072 Ontario workers. Increased incidence rates of AMI were found across forestry (HR 1.37, 95% CI 1.19-1.58) and wood processing (HR 1.50, 1.27-1.77) job-titles. Elevated rates were also detected within industries and occupations both broadly related to mining and quarrying (HR 1.52, 1.17-1.97), trucking (HR 1.32, 1.27-1.38), construction (HR 1.32, 1.14-1.54), and the manufacturing and processing of metal (HR 1.41, 1.19-1.68), textile (HR 1.41, 1.07-1.88), non-metallic mineral (HR 1.30, 0.82-2.07), and rubber and plastic (HR 1.42, 1.27-1.60) products. Female food service workers also had elevated AMI rates (HR 1.36, 1.23-1.51). This study found occupational variation in AMI incidence. Future studies should examine work-related hazards possibly contributing to such excess risks, like noise, vibration, occupational physical activity, shift work, and chemical and particulate exposures.

A Study on Operational Excellence: Sustainable Supply Chains of Manufacturing Industries during COVID-19 Pandemic

This paper presents an investigation on operational excellence (OpEx) models of sustainable supply chains (SSCs) in Sri Lankan manufacturing organizations during the COVID-19 pandemic. The investigation was executed with the assistance from multiple case studies (namely, 5 cases) in the following manufacturing industries: manufacture of clothing, manufacture of furniture, manufacture rubber and plastic products, manufacture of electrical equipment, and manufacture of paper and paper products. In accordance with an extensive literature review, an accumulation of SSCs, OpEx, and associated models in different viewpoints of manufacturing organizations were identified in various literature works. This research was conducted as an exploratory case study utilizing a multi-mode research choice in which data is collected through in-depth interviews, and company website/reports. By using a deductive approach, this research derived findings based on critical success factors of an existing hypothesized model known as ―sustainable OpEx model‖ in Sri Lankan context which was utilized by manufacturing organizations for the case studies. Thereby, the study shows which organization has the more sustainable approach in order to better manage the aforementioned sustainable OpEx model. The investigation is supported through the usage of Upper-Echelons theory, which gained an insight on the perspectives of top management during the prevailing period of COVID-19 pandemic. Accompanied by a thematic analysis, findings on critical success factors of OpEx models in SSCs of the case studies were displayed. The findings illustrate that those critical success factors affecting Sri Lankan manufacturing organizations‘ were sustainable to a certain extent. However, significant deviations were encountered despite the implementation of OpEx models in their SSCs, during the outbreak of COVID-19. These findings were considered non-generalizable beyond the presented case studies. A critical challenge that was faced in the duration of this research was dealing with a lack of literature work in relevance to COVID-19 pandemic.

Loading Silica for Supporting Carbon Black Filler to Prevent Degradation Natural Rubber Caused DME

DME (Dimethyl Ether) is the future environmental friendly fuel. Some parts of equipment for transporting the DME are using rubber as a hoses or seals. This research is about the using of natural rubber for those applications. The influential part in the manufacture of natural rubber products are fillers. The use of filler depends on what the product will be made. DME nature have high permeability and easy to absorb into a rubber and plastic. In such of that, the rubber or plastic could be damaged and not durable. In order to determine the type of degradation, the number of samples were immersed in liquid DME. The ratio of the loading of carbon black/silica filler in natural rubber was varied. DME causes two types of degradation, namely absorption and extraction. The addition of filler composition can reduce the absorption and extraction, which can cause a reduction in the percentage decrease in the value of the change in mass and a decrease in tensile strength. On the other hand, the addition of filler composition will increase the changes of hardness. The higher filler loading, will increase the crosslink density and lower scorch time. The presence of silica further is to enhance the crosslink density as well as to lower scorch time. Therefore, the presence of silica affect on the decreasing of the swelling level and shrinking. In general, the presence of silica filler in the mixture will be slightly lowering the tensile strength, but not affecting the elongation at break. The presence of silica before and after soaking with DME will increase hardness.

Study on sulfur vulcanized natural rubber formulated with nitrosamine safe diisopropyl xanthogen polysulfide/tertiary butyl benzothiazole sulphenamide binary accelerator system

An outstanding interest on elimination of nitrosamine generation in traditional sulfur vulcanization systems has led to introduce nitrosamine safe accelerator/s to produce safe natural rubber (NR) vulcanizates. It is an effective way to prevent formation of carcinogenic N-nitroso compounds during manufacture of rubber products. In the present study, behavior of nitrosamine safe binary accelerator system consisting of diisopropyl xanthogen polysulfide (DIXP) with commonly used non-regulated accelerator N-tert-butyl-2-benzothiazole sulfenamide (TBBS) was investigated in efficient sulfur vulcanization of NR. Cure characteristics, physico-mechanical properties and crosslink density of vulcanizates prepared with different combinations of the accelerator system were evaluated and compared with those of individual accelerators. The study reveals that moduli and strength properties of the vulcanizate prepared with DIXP accelerator are inferior to those of the vulcanizate prepared with TBBS accelerator. Nevertheless, optimum cure time of the DIXP compounds is lower in comparison to TBBS compounds. Moreover, progressive replacement of DIXP with TBBS in the accelerator system showed a synergistic effect in regard to cure characteristics and physico-mechanical properties.

Intrinsic room temperature self-healing natural rubber based on metal thiolate ionic network

An intrinsic self-healing natural rubber featuring reversible metal-thiolate ion networks was fabricated and the corresponding healing mechanism and mechanical properties were presented. The developed materials were able to repair themselves at room temperature upon damage without any external stimuli. Reversible metal-thiolate ion networks were proven to form within the rubber material. These networks dominated the cross-linking system and were identified by Differential Scanning Calorimetry (DSC) and Fourier-transform Infrared Spectroscopy (FTIR). Meanwhile, the quantitative amount of metal-thiolate ion networks and covalent crosslinks was determined by swelling testing. Scanning Electron Microscopy (SEM) results revealed that intermolecular diffusion had occurred at the fracture area of the self-healing samples. The results revealed that the mechanical properties could be 100% regenerated after the broken samples were brought into contact with each other. It was also found that self-healing increased by 60% of the material lifespan. This new material is expected to open up promising avenues for the manufacturing of sustainable rubber products.