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.

Dispersion characteristics of clayey soils containing waste rubber particles

The rubber-containing waste materials have been widely used to improve the engineering properties of soils in recent years.Among others,granular rubbers are utilized in various ways to increase the bearing capacity and shear strength and to reduce the settlement and liquefaction potential of soils.The granular rubbers have many advantages such as temperature resistance,flexibility,tear-resistance,non-slip,and thermal and electrical insulation.This study presents the distribution characteristics of five different types of clayey soils with different engineering properties containing waste rubber particles(WRPs).On the other hand,determining and controlling the dispersion characteristics of clayey soils is two significant engineering problems.The study aims to solve these two remarkable and problematic issues in an eco-friendly and safe way.The role of WRP treatment in the investigation of soil dispersion behavior,which can cause dangerous problems such as piping,erosion,and dispersion,reflects the original and different perspectives of this study.Within this scope,geotechnical parameters of the clayey soils were determined.Subsequently,pinhole test,crumb test,double hydrometer test,and scanning electron microscopy(SEM)analysis were performed on the Na-activated bentonite,refined ball clay,Ukrainian kaolin,Avanos kaolin,and Afyon clay samples with different percentages of WRPs(0%,5%,10%,and 15%).Consequently,Avanos and Ukrainian kaolin clays gave the most limited response to the dispersion behavior with the addition of WRP.Also,WRP treatment on the ball clay and bentonite samples showed limited efficiency.Afyon clay,which was defined as dispersive by the three tests that determined its dispersion potential,showed 3 level changes in the pinhole tests and 2 level changes in the crumb tests,and gave the most effective results in terms of WRP efficiency.

STUDY ON NYLON 6/SUPERFINE RUBBER PARTICLES COMPOSITES VIA IN SITU POLYMERIZATION

Two highly cross-linked superfine styrene-butadiene rubber particles, one with 1 wt% of carboxyl groups and theother without such groups having particle sizes of 130-150 nm and 80-100 nm respectively, were used to prepare nylon6/rubber composites via in situ polymerization. It was found that carboxylic styrene-butadiene dispersed uniformly in nylonmatrix and there was strong interfacial interaction because of the graft polymer formed by the reaction of nylon with carboxylgroup of the rubber, resulting in considerably improved impact strength with almost unchanged tensile strength. However,the addition of styrene-butadiene without carboxyl groups showed intensive agglomeration of the rubber particles and weakinterfacial interactions, and the toughness of the materials was improved slightly. The crystallization and rheological behavior of the composites were also discussed.

SPECIAL EFFECT OF ULTRA-FINE RUBBER PARTICLES ON PLASTIC TOUGHENING

According to the present theories of plastic toughening, it is impossible to enhance the toughness, stiffness and/orheat resistance of plastics simultaneously by using rubber. A series of novel nano-rubber particles (UFPR) were introduced,which were prepared through irradiating common rubber lattices and spray drying them. Epoxies toughened with UFPRshowed a much better toughening effect than those with CTBN, and the heat resistance of epoxy was unexpectedly elevated.For polypropylene toughening, UFPR can improve the toughness, stiffness and heat resistance of PP simultaneously. Thesespecial toughening effects overcome the deficiencies in rubber toughening technology and are worth further investigating.

DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. 'the second plateau', appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

Improvement of Cracking-resistance and Flexural Behavior of Cement-based Materials by Addition of Rubber Particles

By ring test and bend test, the improvement of waste tire rubber particles on the crack- resistance and flexural behaviors of cement-based materials were investigated. Test results show that the cracking time of the ring specimens can be retarded by the incorporation of rubber particles in the cement paste and mortar. The improvement in the crack-resistance depended on the rubber fraction. When the rubber fraction was 20% in volume, the cracking time was retarded about 15 h for the paste and 24 d for the mortar respectively. Flexural properties were evaluated based on the bend test results for both mortar and concrete containing different amount of rubber particles. Test results show that rubberized mortar and concrete specimens exhibit ductile failure and significant deformation before fracture. The ultimate deformations of both mortar and concrete specimen increase more than 2-4 times than control specimens.

Effect of Rubber Particles on Cement Stabilized Gravel System

The primary objective of this paper was to study the mechanical properties and durability of the cement stabilized gravel by different compact method. The influence of rubber particle content on mechanical properties of samples was studied by compaction tests and freezing thawing recycle tests. Pore structure and fractal characteristic of mixture were analyzed quantitatively using mercury intrusion porosimetry （MIP）. X-ray diffraction （XRD） was adopted to identify the composition phases. The morphology analysis in micro scale and elemental analysis of samples were carried out by scanning electron microscope （SEM）. The optimum compressive strengths of rubber cement stabilized gravel （RCSG） with static compaction method and with vibratory compaction method were obtained by controlling compaction degree and vibration time, respectively. From the compaction tests, the vibratory compaction method is preferred compared with the static compaction method as better compressive strength can be improved by about 340%-360%. Besides, test results also reveal that compressive strength of samples with vibratory compaction method or static compaction method will decrease with the rubber particle bulk content increasing. The freezing thawing recycle tests indicate that freezing thawing resistance has been improved （frozen stability coefficient K has been increased from 0.89 to 0.97） by the addition of rubber particles. MIP tests show that the mean pore diameter and porosity of mixture have been increased from 70 to 250 nm and 9% to 24% respectively, with the rubber particles content increasing. Component analysis shows that the calcium silicate hydrate （CSH） is the predominant hydrate product with or without the addition of rubber particles.

Effect of Rubber Particle Modifi cation on Properties of Rubberized Concrete

To improve the combination of cement matrix and waste tire rubber particles in concrete, the rubber particles were treated with acrylic acid（ACA） and polyethylene glycol（PEG） for grafting hydrophilic groups on their surfaces. The X-Ray photoelectron spectroscopy（XPS） and surface contact angle were used to characterize the hydrophilicity and surface functional group of rubber particles. The effect of rubber particle modifi cation on fresh/hardened properties of rubberized concrete was studied. The experimental results show that the contact angle between rubber particle surface and water decreases when rubber particle is modifi ed. Compared with the unmodifi ed rubberized concrete（RC）, the unit weight of modifi ed rubberized concrete（MRC） changes slightly. However, the slump, air-entrainment, compressive strength, flexural strength, and impact performance of MRC are obviously improved. Under good condition of slump, the water-cement ratio of the MRC can be reduced from 0.4 to 0.38. And the compressive strength and fl exural strength of the MRC（10% rubber particle content） can be increased by 25.9% and 26.4%, respectively.

Waste Tire Rubber Particles using to Improve the Properties of Local Asphalt Concrete

The research considered urgent ecological reasons linked to environment such as worn tires, the waste tire rubber＇s powder was collected from the tire cars repair shops （passed from the sieve No 18 μm）, and used to improve the asphalt concrete properties. Raw materials used were prepared and tested. Varies of asphalt concrete mixtures were prepared with different ratios of bitumen （5, 5.5, 6, 6.5, 7% % of concrete weight）. The Marshall mix design method was used to determine optimum conditions for bitumen in asphalt concrete with specific weight, stability and flow Test, the optimum amount of bitumen was 6.1% of whole asphalt concrete. The different percentages of waste tire rubber powder （0.0, 0.05, 0.10, 0.15% of bitumen weight） were added in optimum bitumen of asphalt concretes, then specific weight and Marshall test were evaluated. These asphalt-rubber mixtures were found to act quite differently from traditional, unmodified asphalt mixtures. However, these results indicate that improved pavement performance can be achieved with asphalt-rubber binder.

COORDINATION CROSSLINKING OF NITRILE RUBBER FILLED WITH COPPER SULFATE PARTICLES

By incorporating copper sulfate （CuSO4） particles into acrylonitrile butadiene rubber （NBR） followed by heat pressing, a novel vulcanization method is developed in rubber through the formation of coordination crosslinking. This method totally differs from traditional covalent or non-covalent vulcanization approaches of rubber. No other vulcanizing agent or additional additive is involved in this process. By analyzing the results of DMA, XPS and FT-IR, it is found that the crosslinking of CuSO4 particles filled NBR was induced by in situ coordination between nitrogen atoms of nitrile groups （-CN） and copper ions （Cu^2＋） from CuSO4. SEM and EDX results revealed the generation of a core （CuSO4 solid particle）- shell （adherent NBR） structure, which leads to a result that the crosslinked rubber has excellent mechanical properties. Moreover, poly（vinyl chloride） （PVC） and liquid acrylonitrile-butadiene rubber （LNBR） were used as mobilizer to improve the coordination crosslinking of CuSO4/NBR. The addition of PVC or LNBR could lead to higher crosslink density and better mechanical properties of coordination vulcanization. In addition, crystal water in CuSO4 played a positive role to coordination crosslinking of rubber because it decreased the metal point of CuSO4 and promoted the metal ionization.

RuRh Bimetallic Nanoparticles Stabilized by 15-membered Macrocycles-terminated Poly(propylene imine) Dendrimer:Preparation and Catalytic Hydrogenation of Nitrile–Butadiene Rubber

A new fourth-generation poly(propylene imine) dendrimer(G4-M) containing 32 triolefinic 15-membered macrocycles on the surfaces has been synthesized. The bimetallic Ru Rh dendrimer-stabilized nanoparticles(DSNs) were first prepared within G4-M by a co-complexation route. The new G4-M dendrimer has been characterized by 1H nuclear magnetic resonance, infrared radiation, and elemental analysis.The dendrimer-stabilized bimetallic ions and reduction courses were analyzed by UV-vis spectroscopy. Highresolution transmission electron microscopy and energy dispersive spectrometer were used to characterize the bimetallic nanoparticle size, size distribution, and particle morphology. The Ru Rh bimetallic DSNs showed high catalytic activity for the hydrogenation of nitrile-butadiene rubber.

Detailed Mechanism and Engineering Applicability of Electrolytic Polymerization Aided by a Magnetic Field in Natural Rubber by Mechanical Approach for Sensing (Part 2): Other and Intrinsic Effects on MCF Rubber Property

The same ordinary electrolytic polymerization of plastic-type polymer solution is applicable to natural rubber, with its C=C bonds, if a magnetic field and a filler are added. With the application of a magnetic field and the magnetic responsive fluid known as magnetic compound fluid (MCF), we have clarified the enhancement of the electrolytic polymerization of NR-latex and the growth of the thickness of vulcanized MCF rubber that results from the addition of a magnetic field. The present new method of MCF rubber vulcanization is effective for use in haptic sensors, which are used widely in various engineering applications. In the previous report, part 1 of this study, we investigated many experimental conditions under mechanical approach for sensing: magnetic field strength;applied voltage;electrodes gap;mass concentration, and the ingredients of the MCF. In the present sequential report, part 2, we investigate many other effects on electrolytic polymerization by the same mechanical approach for sensing as in part 1: the Mullins effect;the Piezo effect;vibration;kind of electrode;atmospheric gas. In particular, we clarify that the voltage generates spontaneously in the MCF rubber and that the MCF rubber becomes a Piezo element. These effects on the electrolytic polymerization as well as the effects of the experimental conditions will be useful in engineering applications. By taking the above-mentioned parameters and effects into account, MCF rubber that is electrolytically polymerized with the aid of a magnetic field, the use of MCF as a filler, and doping, can be useful in haptic sensor applications. In particular, the effectiveness of the Piezo element can be shown.

Detailed Mechanism and Engineering Applicability of Electrolytic Polymerization Aided by a Magnetic Field in Natural Rubber by Mechanical Approach for Sensing (Part 1): The Effect of Experimental Conditions on Electrolytic Polymerization

Ordinary electrolytic polymerization has involved plastic-type polymer solutions. Rubber, especially natural rubber, is one such polymer solution. Rubber has not been focused on until recently due to the fact that electrolytic polymerization has only a very small effect on rubber. However, when we focus on the C=C bonds of natural rubber, the same electrolytic polymerization is applicable to be enlarged on the natural rubber if a magnetic field and a filler are added. With the application of a magnetic field and a magnetic responsive fluid such as magnetic compound fluid (MCF), the effect of electrolytic polymerization on NR-latex such as plastic-type polymer solutions is enhanced, and the thickness of the vulcanized MCF rubber grows in a short time. The present new method of vulcanization of MCF rubber is effective enough that it is widely used in haptic sensors in various engineering applications. In the present report, as mechanical approach for the sensing, by measuring the temperature under electrolytic polymerization, by investigating the electric and dynamic characteristics, and by observing the magnified appearance of the MCF rubber, we clarified the extrinsic effects of many experimental conditions, including magnetic field strength, applied voltage, the electrodes gap, mass concentration, and the ingredients of the MCF. This report is Part 1, to be followed by another sequential report, Part 2, in which other intrinsic effects on the characteristics are dealt with. The experimental conditions used and the results obtained in the present report provide valuable data that will be useful in the making of MCF rubber.

Magnetic,thermal stability and dynamic mechanical properties of beta isotactic polypropylene/natural rubber blends reinforced by NiZn ferrite nanoparticles

The dispersion of magnetic nanoparticles in matrix is crucial to ensure optimum performance of the composite.The difficulty level of achieving good dispersion is further increase when a multi-phases of matrix is present.A pre-coating technique of magnetic nanoparticles with polypropylene using ball-mill prior to melt-blending process was employed to prepare a multi-phases thermoplastic natural rubber composite.The effect of filler loading(2 wt%-10 wt%) on morphology,structure,magnetic properties,thermal stability and dynamic mechanical properties of the composites were investigated.It was found that the NiZn ferrite nanoparticles act as nucleating agent to form beta isostatic polypropylene thermoplastic composites.The composites’ magnetic properties are directly dependent on the filler concentration.The dispersion of magnetic fillers in polymer matrix plays role in affecting the magnetic properties and thermal stability.The preference of filler to locate at amorphous phase has distorted the chain orientation of natural rubber and polypropylene.Hence,the polymorphism and crystallinity of the matrix varied as the filler loading increased,affecting the dynamic mechanical properties.It was found that 8 wt% NiZn nanocomposite exhibits highest E’ and tanδ,indicating the dynamic mechanical properties of NiZn nanocomposite are affected by β-phase degree.

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.

Characterization of FeCo Nanoparticles Reinforced Natural Rubber using Nanomechanical Mapping

The morphology, nanomechanical properties and interfacial regions of natural rubber（NR） and FeCo nanoparticles composite were determined by AFM nanomechanical mapping. The results showed that the size of FeCo particles was mostly from 40 to 100 nm and the FeCo nanoparticles were homogeneously dispersed in the NR bulk. The strength of NR composite increased with the FeCo nanoparticles loading. Young＇s modulus of NR region, FeCo region and interfacial region was measured by AFM nanomechanical tapping as 1.6 ± 0.6, 16.7 ±4.2 and 5.8 ± 1.5 MPa, respectively. The width of the interface for NR5, NR10 and NR15 was determined to be 15±8.1, 26±14.3 and 32±16.4 nm, respectively.

The Relative Viscosity of Concentrated Rubber Suspensions and Viscoelastic Modulus of 3D Сross-Linked Elastomers Filled with Solid Particles

For the first time, this paper describes the concentration dependence of the relative dynamic viscosity coefficient of rubber suspensions and the initial viscoelastic modulus of 3D cross-linked elastomers on the maximum volume filling with solid polydisperse particles. It allows to predict the rheological and mechanical properties of the polymer compositions being developed now. In this paper, we present the first experimental study of the pole of the concurrent lines of the concentration dependence in the coordinates of the linear form. The pole validates the invariant value of the constant of the developed equation and allows the experimental determination of the maximum volume filling of polymer binders filled with separate fractions or polydisperse mixtures. The results of the study are recommended for use in developing new polymer composite materials.

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.

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.

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.