Rubber Particle Size Research Articles

Notched impact behaviour of polymer blends: Part 2: Dependence of critical particle size on rubber particle volume fraction

The stress-field model introduced in Part 1 is used to analyse the effects of rubber particle size D and volume fraction ϕ on impact behaviour. The model is refined by including energy released from the matrix during rubber particle cavitation, and interactions between cavitated rubber particles, porous shear bands, and crazes, in the later stages of energy absorption. The analysis shows that with increasing ϕ, critical stresses for rubber particle cavitation increase slightly, while yield stresses and craze formation stresses fall substantially, and craze stability increases. Particle morphology and particle–matrix adhesion also affect the locations of the brittle-ductile (BD) transition, which is caused by cavitation resistance in very small particles, and the ductile-brittle (DB) transition, which is due essentially to failure of crazes initiated from larger particles. Comparisons of model predictions with Izod data provide further insight into the ways in which large porous plastic zones develop ahead of notch tips.

Laboratory evaluation on the high temperature rheological properties of rubber asphalt: a preliminary study

Crumb rubber is the recycled rubber particle obtained from mechanical shearing or grinding scrap tires into small particle sizes less than 6.3 mm (or approximately 1/4”). The rheological properties of asphalt binder have an important effect on the field performance of asphalt mixtures and the long-term serviceability of asphalt pavement. The objective of this research is to evaluate the high temperature rheological performance of rubber asphalt binder based on the complex shear modulus (|G*|) and the phase angle (δ) values using the dynamic shear rheometer. Five rubber asphalt dosages at 0, 10, 15, 20, and 25% by weight of asphalt (Superpave PG 64-22), respectively, were used to modify asphalt binder; and three rubber particle meshes, 20#, 30#, and 40#, were utilized in this research. The |G*| at various temperatures and frequencies were tested on each sample, including original and short-term aging binder using the rolling thin-film over. The master curves of |G*|/sin(δ) for each type of rubber asphalt was generated to investigate its rheological properties over a broad range of temperatures and frequencies. Based on the testing results, it was found that the addition of crumb rubber significantly increases the |G*| of asphalt binder, which is desirable to potentially improve the anti-rutting performance of asphalt mixtures. It was also found that the addition of 10% mesh crumb rubbers bumps up the high temperature grade of asphalt, from PG64 to PG76 in this case. The master curve using the |G*|/sin(δ) of rubber asphalt shows a substantial improvement in rutting resistant at each testing temperature and loading frequency. However, it was noteworthy that the rutting resistance enhancement of crumb rubber was affected by the percentage of rubber used, the rubber particle size and its aging condition.

Vibration Induced by Rail Traffic: Evaluation of Attenuation Properties in a Bituminous Sub-ballast Layer

The attenuation properties of a Hot-Mix Asphalt track bed containing crumb rubber (particle size 2-5mm) are evaluated. A large number of vibration measurements have been carried out in a test section of a railway interconnection (Turin-Milan HS Railway) where two solutions of 12cm of sub-ballast layer have been realized (with and without rubber). The vibrations were measured using a set of piezoelectric accelerometers positioned at various distances from the track to measure their generation and propagation. The results show that the new hot mix asphalt layer can influence the train vibration transmission.

Factors affecting creaming efficiency of bio-based polymers, vulcanization and mechanical properties of creamed skim rubber

Recovery of skim rubber from skim natural rubber (SNR) latex was studied by using three bio-based polymers, N,O-carboxymethyl chitosan (CMCh), sodium alginate (SA) and carboxymethylcellulose (CMC), as creaming agents. It was observed that creaming efficiency of the bio-based polymers was governed by concentration, viscosity and types of bio-based polymers used but independent of ammonia concentration and dry rubber content of SNR latex. CMCh, SA, and CMC having viscosity in a range of 10 mPa s – 25 mPa s were found to be the excellent creaming agents for SNR latex. Average sizes of rubber particles in the cream phase were not quite different from those of the original SNR latex. The skim rubber in the cream phase could be coagulated by using only a small amount of H2SO4. The obtained skim rubber contained lower protein than the skim rubber recovered by the traditional method using conc. H2SO4 which markedly affected the vulcanization characteristics of the skim rubber. In addition, physical and mechanical properties such as initial Wallace plasticity, modulus at 100% strain, tensile strength and elongation at break of recovered skim rubber were influenced by the use of creaming agents.

Dependence of the Average Size of Particles Formed during Steady Mixing on their Concentration in Immiscible Polymer Blends

A linear increase in the size of ethylene-propylene rubber particles with its content in polypropylene matrix at steady mixing in a batch mixer was observed. This type of the dependence is predicted by the theory of dynamic equilibrium between the droplet breakup and coalescence. However, theoretical calculation of droplet radius extrapolated to zero concentration of EPR and slope of the dependence of droplet radius versus concentration, based on the effective shear rate (related to mixing conditions), are in strong disagreement with the experimental results. Reasons for these discrepancies between theories and experimental results are thoroughly elucidated.

Influence of rubber particle size on properties of recycled thermoplastics containing rubber tyre waste

Recycling represents a valid alternative to the disposal of post-consumer plastics in common landfills only when it is possible to obtain new materials with good final properties through practical applications and above all using inexpensive methods. Considering the problem of the great amount of rubber tyre waste produced worldwide, the objectives of this study are to incorporate particles of tyre rubber (TR) waste scrap into a thermoplastic matrix, post-consumer polypropylene (PP) and high impact polystyrene (HIPS) and to evaluate the rheological, physical and mechanical properties. The thermoplastic materials used were ground, washed, dried and ground again into flake form. The particle sizes of the TR used were <500 and 500–1000 μm, separated using a system of sieves of the Tyler mesh series. The PP/TR and HIPS/TR composites, both with weight ratios of 90∶10 and 70∶30, were processed by injection moulding. Results for the rheological behaviour showed that the incorporation of TR particles into the recycled HIPS and PP matrix led to opposite behaviours and that the extent of the effect was dependent on the nature of the polymer and the filler type and particle size. In addition, the presence and concentration of TR led to a reduction in the mechanical properties when compared with the unfilled matrix (post-consumer PP and HIPS), as confirmed by SEM images and the physical properties.

Toughening of polyvinylchloride by methyl methacrylate–butadiene–styrene core–shell rubber particles: Influence of rubber particle size

AbstractAn analysis was made on the effects of rubber particle size on the mechanical properties and deformation mechanisms of transparent polyvinyl chloride (PVC) blends containing core–shell methyl methacrylate–butadiene–styrene (MBS) impact modifiers. The critical interparticle distance was found not to be the criterion for the brittle‐ductile transition in the blends. In tensile tests, the blends with larger (100–280 nm) rubber particles exhibited intense stress‐whitening, while one blend with small (83 nm) rubber particles showed only slight stress‐whitening. These differences were due to an increase in resistance to cavitation with decreasing rubber particle size. Transmission electron microscopy studies on blends with a bimodal distribution of particle sizes showed that in the whitened zone of Izod specimens the larger rubber particles cavitated and expanded on yielding, while the smaller particles remained intact. However, Izod test results showed that small MBS rubber particles can toughen the PVC matrix very effectively, especially at low temperatures and at low rubber concentrations. The deformation mechanisms responsible for these effects were discussed. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Study of Mechanical Properties and Physical Properties of Rubberized Portland Cement Concrete

This test summers up the research situation of rubber powder modifier. According to tests of density, flexural strength, compressive strength and cleavage strength, this test analyzes the basic mechanical properties and the variation of rubberized portland cement concrete which is mixing the silica fume modifier. The results show that the flexural strength, compressive strength and cleavage strength of concrete may increase when silica fume concrete admixture modifiers is mixed in cement concrete. The workability, density, flexural strength, compressive strength, ratio of compressive strength and cleavage strength of rubberized portland cement concrete gradually reduced with the increase in dosage of rubber. The rubber particles mixed with concrete which can when the rubber particle size is not more than 30% of the dosage of coarse aggregate, the fine pavement of rubberized portland cement concrete can be got.

Applicability of Wu's criterion for brittle–ductile transition of ethylene/1‐octene copolymer toughened polyamide 6

AbstractThe brittle–ductile transition of ethylene/1‐octene copolymer (POE) toughened polyamide 6 (PA6) was studied at various temperatures. The experimental results show that the critical interparticle distance (IDc) is independent of the POE content, and the POE particle size at lower temperatures, that is, the temperature is much lower than the brittle–ductile transition temperature (T) of PA6. At higher temperatures, however, especially temperatures close to the T, the IDc depends on the POE particle size. This indicates that Wu's criterion for rubber toughening, specifically that “the IDc is a material property of the matrix, independent of rubber volume fraction and particle size,” is inapplicable at higher temperatures for the brittle–ductile transition of the POE toughened PA6. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Attaining high electrical conductivity and toughness in PA6 by combined addition of MWCNT and rubber

Tough polyamide 6 (PA6)/multi-walled carbon nanotube (MWCNT) nanocomposites modified by a maleated styrene/ethylene–butylene/styrene (mSEBS) were obtained in the melt state. The resistance calculations showed that both the conductivity values and the percolation threshold was not consequence of the physical contact among the nanotubes, and a double percolation phenomenon was observed after rubber addition. The addition of rubber did not affect the dispersion of the nanotubes, but the presence of MWCNT decreased the rubber particle size due to an increase in viscosity. Besides a high electrical conductivity and an elastic modulus similar to that of the PA6, the joint presence of 5% in weight (wt.%) MWCNT and 20wt.% mSEBS was able to provide both a large impact strength and clear ductile behaviour. The matrix yielding of the carbon nanotube-based nanocomposites was less extensive than in nanoclay-based composites. However, they were efficient enough to lead to a clear multi-functionality.

Health risk assessment of lead ingestion exposure by particle sizes in crumb rubber on artificial turf considering bioavailability.

ObjectivesThe purpose of this study was to assess the risk of ingestion exposure of lead by particle sizes of crumb rubber in artificial turf filling material with consideration of bioavailability.MethodsThis study estimated the ingestion exposure by particle sizes (more than 250 um or less than 250 um) focusing on recyclable ethylene propylene diene monomer crumb rubber being used as artificial turf filling. Analysis on crumb rubber was conducted using body ingestion exposure estimate method in which total content test method, acid extraction method and digestion extraction method are reflected. Bioavailability which is a calibrating factor was reflected in ingestion exposure estimate method and applied in exposure assessment and risk assessment. Two methods using acid extraction and digestion extraction concentration were compared and evaluated.ResultsAs a result of the ingestion exposure of crumb rubber material, the average lead exposure amount to the digestion extraction result among crumb rubber was calculated to be 1.56×10-4 mg/kg-day for low grade elementary school students and 4.87×10-5 mg/kg-day for middle and high school students in 250 um or less particle size, and that to the acid extraction result was higher than the digestion extraction result. Results of digestion extraction and acid extraction showed that the hazard quotient was estimated by about over 2 times more in particle size of lower than 250 um than in higher than 250 um. There was a case of an elementary school student in which the hazard quotient exceeded 0.1.ConclusionsResults of this study confirm that the exposure of lead ingestion and risk level increases as the particle size of crumb rubber gets smaller.

Effects of Particle Size on the Rubber Mixing Process and Mechanical Properties of Compound

In order to improve the dispersion degree of carbon black and other additives, reduce consumption of energy and the temperature of discharging rubber compound, our research has been focused on preparation of rubber compound with different rubber particle size at filling coefficient of 0.6 and 0.7 in the mixer. The power consumption, the temperature of discharging rubber compound and the dispersion of carbon black were characterized in this study. The mechanical properties of the rubber compound have also been tested. The results indicate that reducing the particle size of rubber can reduce the consumption of energy and the temperature of discharging rubber compound and improve the mechanical properties, which is very important in rubber industry

Incorporação de resíduos de borracha em compósitos de matriz polimérica termorrígida

A dificuldade de degradação e armazenamento de rejeitos de pneus vem a cada ano intensificando os problemas ambientais, além da proliferação de insetos e roedores, tornando um resíduo danoso à saúde pública. Este trabalho tem como objetivo estudar o efeito da incorporação de resíduos de borracha de pneus nas propriedades físicas e mecânicas de compósitos de matriz polimérica termorrígida, visando à reutilização do resíduo industrial e a obtenção de produtos que atendam aos padrões e normas técnicas da indústria Brasileira. Um planejamento fatorial completo de experimentos do tipo 2²3¹ foi utilizado na análise dos resultados. Os fatores experimentais investigados neste trabalho foram: granulometria (30/50 e 100/200 US-Tyler), fração volumétrica (10, 25 e 50%) das partículas de borracha e adição de anidrido maléico (1,5%) como agente compatibilizante. As variáveis respostas investigadas neste experimento foram: densidade volumétrica, porosidade aparente e resistência à compressão. As partículas 100/00 US-Tyler promoveram maior densidade, aumentando a resistência mecânica dos compósitos. O aumento da fração de borracha reduz a densidade e a resistência mecânica, entretanto, o percentual de 25% exibe propriedades aceitáveis em aplicações de engenharia. O anidrido maléico afetou as propriedades dos compósitos principalmente quando partículas de 30/50 US-Tyler e fração de 10 a 25% de borracha foram adicionadas.

Mechanical and Thermal Properties of Chemically Modified Epoxy Resin

Diglycidyl ether of bisphenol-A (DGEBA), having number average molecular weight (Mn) 375, was modified by incorporating the hydroxyl terminated polybutadiene (HTPB) based prepolymer using isophorone diisocyanate as a coupling agent. To increase the compatibility between the epoxy resin and HTPB part, polar groups were introduced in the later to achieve physical and chemical interactions between the two phases. The finally modified DGEBA system was cured with amine based hardener. FTIR and 1H-NMR were used to monitor the whole modification procedure. The rubber particles size and distribution was monitored as a function of HTPB contents in the resin system using scanning electron microscopy (SEM). The mechanical, thermal and thermo-mechanical properties have shown that the tensile strength, toughness, ductility and impact strength of the modified cured system have been successfully increased at some optimum HTPB contents without affecting the inherent thermal and thermo-mechanical stability associated with DGEBA resin system. Some of the mechanical properties like flexural modulus, tensile modulus and compressive strength decreased with increasing rubber contents.

Preparation of dynamically vulcanized thermoplastic elastomer nanocomposites based on LLDPE/reclaimed rubber

AbstractDynamically vulcanized thermoplastic elastomers nanocomposites (TPV nanocomposites) based on linear low density polyethylene (LLDPE)/reclaimed rubber/organoclay were prepared via one‐step melt blending process. Maleic anhydride grafted polyethylene (PE‐g‐MA) was used as a compatibilizing agent. The effects of reclaimed rubber content (10, 30, and 50 wt %), nanoclay content (3, 5, and 7 wt %), and PE‐g‐MA on the microstructure, thermal behavior, mechanical properties, and rheological behavior of the nanocomposites were studied. The TPV nanocomposites were characterized by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy (SEM), differential scanning calorimeter, mechanical properties, and rheometry in small amplitude oscillatory shear. SEM photomicrographs of the etched samples showed that the elastomer particles were dispersed homogeneously throughout the polyethylene matrix and the size of rubber particles was reduced with introduction of the organoclay particles and compatibilizer. The effects of different nanoclay contents, different rubber contents, and compatibilizer on mechanical properties were investigated. Increasing the amount of nanoclay content and adding the compatibilizer result in an improvement of the tensile modulus of the TPV nanocomposite samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Amorphous polyamide/maleated styrene–ethylene–co-butylene–styrene nanocomposites: effects of clay loading and compatibilizer content on morphology and mechanical properties

The effect of the organoclay content on the toughness of a rubbery modified amorphous polyamide (aPA)/organoclay-based nanocomposite was studied by changing the modifier (maleic anhydride) content. The dispersed rubber particle size decreased markedly with the addition of the modifier, indicating compatibilization of the nanocomposite. However, the particle size of the dispersed phase increased slightly with the organoclay content due to the interactions between the dissolved surfactant and the compatibilizer. Furthermore, we observed that the organoclay resided in the aPA matrix, and that its dispersion remained constant upon rubber addition. This resulted in materials with high stiffness and extremely large toughness values, as measured by both the standard impact strength and the essential work of the fracture method. Because the rubber content was kept constant, the inorganic part of the clay was proposed to be the main parameter that controls toughness. The impact strength of an amorphous polyamide/organoclay nanocomposite has been increased by means of a rubber modified with maleic anhydride (MAH). The organoclay resided in the polyamide matrix and maintained dispersed rubber particle size upon rubber addition. The changes of the dispersed rubber particle size with modifier and nanoclay addition indicated compatibilization of the nanocomposites and interactions between the dissolved surfactant and the rubber modifier. The obtained nanocomposites had a high stiffness and extremely large toughness values, as determined both by impact strength measurements and by the essential work of fracture method.

Utilization of phase change materials and rubber particles to improve thermal and mechanical properties of mortar

Phase change materials (PCMs) and rubber particles from recycled tires were used in portland cement mortar with a potential application as insulation mortar. Series of tests were designed and conducted including compressive strength, flexural strength, thermal conductivity, drying shrinkage, and bond strength tests at 7 days and 28 days of age. Different types of additives were also used in the mix designs. The experimental results showed that mechanical properties of rubberized-mortar can be improved by adjusting the size of rubber particles and the amount of additives. With the same volume fraction of PCM and rubbers, the mechanical properties of PCM-modified mortar are either the same or better than that of rubberized-mortar. In terms of thermal properties, the rubber particles can reduce thermal conductivity of the mortar significantly, while the PCM can improve heat capacity of the mortar.

Small-Strain Shear Modulus and Damping Ratio of Sand-Rubber and Gravel-Rubber Mixtures

This study examines the small-strain dynamic properties of mixtures composed of sandy and gravelly soils with granulated tire rubber in terms of shear modulus (GO), and damping ratio in shear (Dmin). Torsional resonant column tests are performed on dry, dense specimens of soil-rubber mixtures in a range of soil to rubber particles size 5:1–1:10 and rubber content from 0 to 35% by mixture weight. The experimental results indicate that the response of the mixtures is significantly affected by the content of rubber and the relative size of rubber to soil particles. Concering the small-strain shear modulus, an equivalent void ratio is introduced that considers the volume of rubber particles as part of the total volume of voids. Based on a comprehensive set of test results a series of equations were developed that can be used to evaluate the shear modulus and damping ratio at small shear strain levels if the confining pressure, the content of rubber by mixture weight, the grain size of soil and rubber particles, and the dynamic and physical properties of the intact soil are known.

Effect of Crumb Rubber Particle Size and Content on Properties of Crumb Rubber Modified (&lt;i&gt;CRM&lt;/i&gt;) Asphalt

Effects of crumb rubber of different particle sizes (20mesh, 40mesh, 60mesh, 80mesh and120mesh) and contents (10%, 15% and 20% by weight of the total of CRM asphalt) on the properties of CRM asphalt and change rule of performance of CRM asphalt with reaction temperature and time were studied in laboratory. The results indicate that CRM asphalt has the best performance when the particle size of crumb rubber used is 80 mesh and the content is 15%. The performance of CRM asphalt is strongly depended on reaction temperature and time. When reaction temperature is higher than 200°C and time more than 60 minutes, the viscosity of CRM asphalt significantly decline with reaction temperature rising and time delaying. The performance of CRM asphalt starts aging when reaction time more than 4 hours at high temperature. Based on test results, some suggestions for production and application of CRM asphalt are put forward.

Laboratory evaluation on high temperature viscosity and low temperature stiffness of asphalt binder with high percent scrap tire rubber

The objective of this research is to utilize crumb rubber from scrap tires as an environmental friendly and sustainable additive for enhancing the high temperature and low temperature rheological properties of asphalt binders for asphalt pavements. Two different crumb rubber sources with different gradations – fine and coarse – were used in this project. The crumb rubber-modified (CRM) binder was produced by adding 10, 15, 20 and 25% crumb rubber particles by weight of a Superpave PG 64-22 asphalt binder. The CRM binders with and without Rolling Thin Film Oven (RTFO) aging were characterized by the AASHTO rotational viscosity test at 135, 140, 150, 160, 170, 177, and 190 °C (AASHTO T316). Furthermore, the low temperature cracking resistance of the binders was evaluated using the AASHTO Bending Beam Rheometer (BBR) test procedure at −12 and −18 °C (AASHTO T313). The statistical analysis of variance (ANOVA) was applied to quantify the effect of the influencing factors such as temperature, rubber particle size, and rubber concentration on the CRM binders’ performance. From the laboratory tests and ANOVA results in this study, it is evident that the addition of crumb rubber into asphalt binder can both significantly improve the viscosity of binder at high temperature and lower the creep stiffness at low temperature, which is beneficial to better both high temperature stability and low temperature cracking resistance of asphalt pavements. After RTFO aging, the viscosity decreases with increasing rubber concentration. Finer crumb rubber attains higher viscosity at high temperature and lower creep stiffness at low temperature. Considering the viscosity–temperature relationship, RTFO aging effects, creep stiffness decreasing percentage, and economical factors, 15% to 20% rubber asphalt ratio is proposed for the production of CRM binder.