Low-temperature characteristicsof rubbers and performance testsof type 120 emergencyvalve diaphragms

Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.

Transient NOE driven signal enhancement of INADEQUATE solid-state NMR spectroscopy for the structural analysis of rubbers

INADEQUATE(Incredible Natural Abundance DoublE QUAntum Transfer Experiment)is one of the most important techniques in revealing the carbon skeleton of organic solids in solid-state NMR spectroscopy.Nevertheless,its use for structural analysis is quite limited due to the low natural abundance of^(13)C-^(13)C connectivity(~0.01%)and thus low sensitivity.Particularly,in semi-solids like rubbers,the sensitivity will be further significantly reduced by the inefficient cross polarization from 1H to^(13)C due to molecular motions induced averaging of^(1)H-^(13)C dipolar couplings.Herein,in this study,we demonstrate that transient nuclear Overhauser effect(NOE)can be used to efficiently enhance^(13)C signals,and thus enable rapid acquisition of two-dimensional(2D)^(13)C INADEQUATE spectra of rubbers.Using chlorobutyl rubber as the model system,it is found that an overall signalto-noise ratio(SNR)enhancement about 22%can be achieved,leading to significant timesaving by about 33%as compared to the direct polarization-based INADEQUATE experiment.Further experimental results on natural rubber and ethylene propylene diene monomer(EPDM)rubber are also shown to demonstrate the robust performance of transient NOE enhanced INADEQUATE experiment.

Preparation and application of carbon nanotubes/conductive carbon black/ethylene-propylene-diene rubber composite

Addition of conductive fillers such as conductive carbon black(CCB)and carbon nanotubes(CNTs)could significantly improve the electrical conductivity of rubber.However,that would result in the deterioration of processing properties for rubber compound and the rapid increase in hardness of vulcanizates,which affected seriously the preparation of conductive rubber composites and thus limits the application in the field of flexible conductive rubber materials.

TEST AND CHARACTERIZATION FOR THE INCOMPRESSIBLE HYPERELASTIC PROPERTIES OF CONDITIONED RUBBERS UNDER MODERATE FINITE DEFORMATION

In this paper, the automated grid method is applied to test for the mechanical properties of conditioned rubbers under the moderate ?nite deformation (not exceeding 100%). More accurate stress-strain curves of conditioned rubber specimens under di?erent conditioned strains are obtained. Test results show di?erences between these curves. Based on an analysis of the classical constitutive models, a new modi?ed eight-chain model is proposed, which takes account of both the locking stretch of chains and the interaction e?ect in the network. Fitting test data shows that the modi?ed model well characterizes the incompressible hyperelastic mechanical behavior of conditioned rubbers under the moderate ?nite deformation as well as under the large deformation.

Experimental evaluation of mechanically stabilized earth walls with recycled crumb rubbers

Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth （MSE） walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents （5 wt%, 10 wt%, 15 wt% and 20 wt%） of recycled crumb rubber （RCR） to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry （PIV） technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.

Degradation of Silicone Rubbers in Fenton's Reagents

Gaskets are applied in PEMFCs（proton exchange membrane fuel cells） to keep reactant gases and liquid within their respective regions, which are of great significance for the both sealing and electrochemical performance of fuel cells during the long-term operation. In this study, the degradation of silicone rubbers, often selected as seals in PEMFCs, in Fenton＇s reagents with different H_2O_2 concentrations was investigated. The changes in chemical properties, mechanical behavior and surface morphology of the samples were studied before and after exposure to the test environment over time. It is found that increasing H_2O_2 concentration will degrade the rubbers more severely. The experimental results elucidate the degradation mechanism of silicone rubbers in Fenton＇s reagents and the influence of H_2O_2 in the degradation process.

Deuterium NMR Studies on the Orientational Order Generated in Strained Rubbers

The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.

Investigation of the Potential of Using Liquid Rubbers in Rubber Industry

Along with the developing technology in the rubber industry, the use of natural and synthetic rubbers as well as liquid rubbers has increased significantly in recent years. The formulation of the tread compound, which directly affects the performance of a tire, is generally produced from natural and synthetic rubbers. Intensive scientific studies have been carried out on liquid rubbers because they reduce the consumption of process oils used in the tire production phase and increase dispersion. In this study, the rheological and physico-mechanical properties of rubbers developed using only liquid rubber (liquid isoprene and liquid SBR) with four different viscosities and without using process oil (Styrene Butadiene Rubber—SBR) were investigated. It has been observed that the rubber blends produced by adding four different liquid rubbers to the same recipe caused changes in rheological and physico-mechanical properties compared to the reference sample. It was observed that the minimum torque/viscosity (ML), maximum torque/viscosity (MH) and curing time (t90) in some of the formulas tested decreased significantly due to the use of liquid rubber.

Synthesis of Oligohydroxynapthylenes and Their Use in Making of Heat-Stable and Electro-Conducting Rubbers

By oxidative polycondensation of 1-naphthol and their copolycondensation with aniline or p-phenylenediamine the polyfucntional polyconjugated oligomers consisting of hydroxynaphthylene links have been prepared. These soluble and meltable oligomers showing thermostability, semiconducting and paramagnetic properties and also high reactivity at reactions characteristic for aromatic hydroxyl groups were used as active filler at preparation of rubbers from butyl and butadiene-nitrile rubbers. It has been shown that in partial or full substitution of carbon black by oligohydroxynaphthylenes or cooligohydroxynaphthylenephenylamines in composition of vulcanizate the prepared rubbers are characterized by noticeably high heat-physical, physical-mechanical and electrical properties （Pv = 10^8 - 10^6Om. cm ）.

Visualization Analysis of the Impact of Rubber Agroforestry Ecosystem on Soil Microbial Community

Rubber agroforestry systems positively impact soil microbial communities. This study employed a bibliometric approach to explore the research status, hotspots, and development trends related to these effects. Using CiteSpace software, we visually analyzed research literature from the Web of Science (WOS) core database, spanning 2004 to 2024. The focus was on the impact of rubber agroforestry ecosystems on soil microbial communities. The results indicate significant attention from Chinese researchers, who have published numerous influential papers in this field. Authors Liu Wenjie have contributed the most papers, although no stable core author group exists. The Chinese Academy of Sciences is the leading research institution in terms of publication volume. While there is close collaboration between different institutions and countries, the intensity of researcher cooperation is low. The most cited literature emphasizes soil nutrients and structure in rubber agroforestry, laying a foundation for soil microorganism studies. Most cited journals are from countries like Netherlands and the United Kingdom. Key research areas include the effects of rubber intercropping on soil microbial communities, agroforestry management, and soil health. Research development can be divided into three stages: the initial stage (2010-2015), the development stage (2015-2020), and the mature stage (2020-2024). Current studies show that rubber intercropping and rubber-based agroforestry systems enhance soil microbial communities, positively impacting soil health. This paper provides a theoretical basis for the sustainable development of rubber agroforestry systems and improved management plans. Future research could explore the effects of species composition on soil microbiological characteristics and develop methods for species interactions. An in-depth study of the soil microbial community’s structure and function, and its relationship with rubber trees, is crucial. Developing effective, rationally designed rubber agroforestry systems and underground soil microbiome technology will promote sustainability and improve plantation productivity.

Physical and Chemical Characterizations of Rubber Latex Cup Bottom Oil

Rubber latex is an important economic resource. However, the residues from its harvesting are thrown away, even though they contain lipids that can be recycled. This recovery of the residues from the bottom of the cup requires first and foremost their characterization. The aim of this study is therefore to determine the main physical and chemical characteristics of rubber latex cup bottom oil. Oil’s physical parameters determination shows that it has a density of 951 kg∙m−3, a kinematic viscosity of 48.57 cSt and a water content of 0.0845%. Chemical parameters, meanwhile, indicate that this cup bottom residue has a fat content of 95.96%, an acid number of 2.805 mg KOH/g and an iodine number of 92.42 g I2/100g. Therefore, rubber latex cup bottom oil can be used in the formulation of biofuels, biolubricants, paints, varnishes, alkyd resins, polishing oils, soaps, and insecticides.

Effect of modified aramid nanofiber on compatibilization of natural rubber/epoxidized natural rubber composites

The combination of natural rubber(NR)with epoxidized natural rubber(ENR)could improve the wet slid resistance,mechanical properties,abrasion resistance and thermo-oxidative aging resistance of NR,which showed important research significance.Aramid nanofiber,as a new nano filler for polymer developed in recent years,had the advantages of both macroscopic fibers and polymer nanomaterials.The NR/ENR composites were prepared by dry mixing with NR and the pre-composite prepared from ENR latex and the modified aramid nanofibers(t-ANF).

Effect of graphene oxide with different oxidation degrees on mechanical properties of styrene-butadiene rubber: Experiment and molecular simulation

Graphene oxide(GO)has proven to be an effective reinfor-cing filler for rubber[1].GO has superior mechanical properties,barrier properties,large specific surface area and abundant oxygen-containing functional groups[2].However,the change in the oxidation degree of GO has a great effect on its chemical properties,the interaction between GO and the matrix,and the dispersion uniformity in the rubber matrix,which has a great effect on the reinforcement of rubber[3].

Seismic evaluation of frequency influence and resonant behavior for lead rubber bearing isolated rigid rectangular liquid tanks

The seismic behavior of a partially filled rigid rectangular liquid tank is investigated under short-and longduration ground motions.A finite element model is developed to analyze the liquid domain by using four-noded quadrilateral elements.The competency of the model is verified with the available results.Parametric studies are conducted for the dynamic parameters of the base-isolated tank,using a lead rubber bearing to evaluate the optimum damping and time period of the isolator.The application of base isolation has reduced the total and impulsive hydrodynamic components of pressure by 80 to 90 percent,and base shear by 15 to 95 percent,depending upon the frequency content and duration of the considered earthquakes.The sloshing amplitude of the base-isolated tank is reduced by 18 to 94 percent for most of the short-duration earthquakes,while it is increased by 17 to 60 percent for the majority of the long-duration earthquakes.Furthermore,resonance studies are carried out through a long-duration harmonic excitation to obtain the dynamic behavior of non-isolated and isolated tanks,using a nonlinear sloshing model.The seismic responses of the base-isolated tank are obtained as higher when the excitation frequency matches the fundamental sloshing frequency rather than the isolator frequency.

Discussion on“Dispersion characteristics of clayey soils containing waste rubber particles”[J Rock Mech Geotech Eng 15(2023)3050-3058]

We read with great interest the recent article by Erenson(2023)entitled“Dispersion characteristics of clayey soils containing waste rubber particles”.The author has studied the dispersion characteristics of clayey soils containing different percentages of waste rubber particles(WRPs)by performing several tests(viz.consistency limit,linear shrinkage limit,double hydrometer,crumb test and pinhole test)and scanning electron microscopy(SEM)analysis on five clayey(viz.Na-activated bentonite,refined ball clay,Ukrainian kaolin,Avanos kaolin and Afyon clay)samples containing 0%,5%,10%and 15%WRPs.It should be noted that Erenson(2023)has presented some interesting observations,but there are some serious issues that we want to share through this discussion and request the author of the original paper to address them to avoid their persistence in the scientific literature.

Mechanical behavior of nanorubber reinforced epoxy over a wide strain rate loading

Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rate sensitivity and strain hardening index increase with increasing nanorubber content.Potential mechanisms are proposed based on numerical simulations using a unit cell model.An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain,generating a higher hydro-static pressure.Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s^(-1) when the strain exceeds 0.35.The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.

Hand Cooling Enhances the Proprioceptive Drift during Rubber Hand Illusion

Background: The neural representation of the body is easily altered by integrating multiple sensory signals in the brain. The “Rubber Hand Illusion” (RHI) is one of the most popular experimental paradigms to investigate this phenomenon. During this illusion, ownership of a rubber hand is temporarily induced. It was shown that external and continuous cooling of the palm enhanced the RHI, suggesting an association between altered the autonomic nervous system regulation and altered the sense of ownership of a specific limb. Purpose: To investigate whether artificially cooling the entire hand for a short period affects the magnitude of the illusion. Methods: Participants immersed their entire hand in cool, cold, or warm water for 1 min before the RHI procedure. Results: We found that cooling the entire hand enhanced the proprioceptive drift during the RHI but not the subjective feeling of ownership. In contrast, warming and intense cooling of the entire hand did not affect the RHI strength. Conclusion: Our results suggest that transient and moderate cooling of the entire hand was sufficient in enhancing the illusory disembodiment of one’s own hand.

Natural rubber latex as a potential additive for water-based drilling fluids

The environmental hazards and"carbon footprint"of oil and gas drilling can be significantly reduced by replacing traditional petroleum-based chemical additives with natural materials derived from plants and animals.This paper explored for the first time the interaction mechanism between natural rubber latex(NRL)and bentonite suspensions(BTs)through a series of characterization experiments,as well as the potential applications in water-based drilling fluids(WBDF).The gel viscoelasticity experiments showed that NRL could decrease the consistency coefficient(k)and flow index(n)of BTs,and enhance the shear thinning performance of BTs as pseudo-plastic fluids.In addition,0.5 w/v%NRL not only increased the critical yield stress and strengthened the structural strength between the bentonite particles,but also facilitated the compatibility of pressure loss and flow efficiency.The evaluation of colloidal stability and WBDF performance indicated that NRL particles could promote the hydration and charge stability on the surface of BTs particles,and optimize the particle size distribution and flow resistance of WBDF under the"intercalation-exfoliation-encapsulation"synergistic interaction.Moreover,NRL can improve the rheological properties of WBDF at high temperatures(<150.C),and form a dense blocking layer by bridging and sealing the pores and cracks of the filter cake,which ultimately reduces the permeability of the cake and the filtration loss of WBDF.

Comparison of nonlinear modeling methods for the composite rubber clamp

The cubic stiffness force model(CSFM)and Bouc-Wen model(BWM)are introduced and compared innovatively.The unknown coefficients of the nonlinear models are identified by the genetic algorithm combined with experiments.By fitting the identified nonlinear coefficients under different excitation amplitudes,the nonlinear vibration responses of the system are predicted.The results show that the accuracy of the BWM is higher than that of the CSFM,especially in the non-resonant region.However,the optimization time of the BWM is longer than that of the CSFM.

Solid-state NMR of vulcanized natural rubber/butadiene rubber blends:Local organization and cross-linking heterogeneities This article is part of the virtual special issue“Solid-state NMR studies on polymers and biological solids”

Elastomer blends,among which natural rubber(NR)and butadiene rubber(BR),are involved in many components of the automotive/tire industry.A comprehensive understanding of their mechanical behavior requires,among other features,a detailed description of the crosslink density in these mixtures.In the case of vulcanized immiscible blends,the distribution of the cross-link density within each of the NR-and BR-rich domains is key information,but difficult to determine using the conventional approaches used for one-component crosslinked elastomers.In this study,the vulcanization within NR/BR blends is investigated using a robust^(1)H double-quantum(DQ)MAS recoupling experiment,BaBa-xy16.Two kinds of cross-linked NR/BR blends were considered with two different microstructures for the BR component.The bulk organization of the resulting blends was first probed by analyzing the^(1)H spin-lattice relaxation behavior.In a second step,BaBa-xy16 was used to investigate,in a selective way,the cross-link heterogeneities within NR/BR blends.In particular,for immiscible NR/BR mixtures,the distribution of the cross-link density between both phases was compared and the observed differences were discussed.