Rubber Particle Size Research Articles

The Effect of Pre-Crosslinked CTBN on the Mechanical Properties and Morphology of Epoxy Resin

A novel kind of rubber toughened epoxy was prepared by in situ pre-crosslinking carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN) in the epoxy matrix. The in situ pre-crosslinking of CTBN was initiated by BPO, followed by the curing reaction of epoxy to form the final pre-crosslinked CTBN/epoxy composites. Mechanical properties of epoxy are further improved by the incorporation of pre-crosslinked CTBN compared with its traditional CTBN/epoxy counterparts due to the improved interfacial strength between rubber and epoxy. SEM shows that the size of phase separated rubber particles of pre-crosslinked CTBN/epoxy decreases significantly.

Cementitious Composites with Rubber Particles from Recycled Tyres: Physical and Mechanical Properties

This work describes a statistical analysis of the mechanical properties of cementitious composites made with recycled rubber inclusions for sustainable structural applications. The rubber particles from recycled tyres were used as replacement of quartz inclusions in the mortars. A full factorial design (7122) was performed to investigate the effect provided by the rubber particles size and fraction on the physical and mechanical properties of the cementitious composites. The results show that the use of rubber particles reduces the overall density, compressive strength and modulus of elasticity, and increases the apparent porosity, water absorption and permeability. Large pores in the composites are present when large size particles are used. The low water/cement ratio adopted in this work did not allow a full hydration of the cementitious phase, which further reduced the overall mechanical performance. Some cementitious composite configurations have however shown acceptable mechanical properties for non-structural applications in civil engineering.

Optimized simulation of vortex jet mill in waste rubber grinding technology by LNG

Frozen rubber powder has excellent qualities and application value, and it can be achieved from waste rubber after being crushed at low temperature used liquefied natural gas (LNG) as cryogen. Vortex jet mill was the key equipment to further crush the rubber particles which the pressure-air was jet into in the basic LNG technological process. After confirming the structure and size of the jet nozzle, the Height (H) between the nozzle and the bottom of the mill, the incident angle α and the initial size of the rubber particles were changed then the continuous phase and the track of single particle were optimized in order to gain more excellent crushing effect. The results showed: the jetting gas were spiral rising in the mill and the speed of it was reduced, so the particle was graded by the gas. The impact and collision could reduce the particle diameter and crush them but the result was influenced by the initial size of the particle. The size of the original rubber particles must not be more than 110μm. The simulation was helpful and leading for the experiment.

Significance of Technological Parameters for Selected Mechanical Properties of Composite Material Based on Scrap Tires

The present work is to be considered as additional research to the authors' previous studies. It is dedicated to the specification of the significance and impact of certain selected technological parameters on mechanical properties of the composite material based on scrap tires. The special method what is known as the “Greece-Latin square” was applied to estimate significance of each technological parameter (input parameter) for selected properties (output parameters) of the material. Moulding pressure (P), formation time (x), polymer binder content (Cpol.) and the size of rubber particles (R) were selected as the input parameters. Compressive modulus of elasticity (Ec), compressive stress at 10% deformation (σ10%), permanent deformation after 10% deformation in compressive mode (ε) and apparent density (AD) were chosen as the output parameters. An analysis of the obtained dispersion diagrams confirms that composition of the composite material (polymer content) has a greater impact on selected mechanical properties of the material than any other technological input parameter, but apparent density of the composite material demonstrates higher sensitivity to the formation time and moulding pressure of the material than to other input parameters. The obtained results of the experiment enable further optimization of the composite material production technology and at the same time securing the predictable mechanical properties of the material.

Property enhancement of PP-EPDM thermoplastic vulcanizates via shear-induced break-up of nano-rubber aggregates and molecular orientation of the matrix

In this study, in order to investigate the influence of melt shearing on the phase morphology and mechanical performance of PP/EPDM thermoplastic vulcanizates (TPVs), the oscillatory melt shear was successively applied on the TPV melt in the mold cavity during the packing stage of injection molding by a modified facility, called dynamic-packing injection molding. For a clear comparison, conventional injection molding was also used. It is shown that conventional injection-molding results in large EPDM rubber aggregates with dimensions of ∼1.5 μm dispersed in the PP matrix. To our surprise, well-dispersed nanoscale EPDM particles with dimensions of ∼40 nm have been achieved for the first time when introducing oscillatory melt shearing, in additional to a largely enhanced molecular orientation for PP matrix. As a result, a simultaneous improvement of tensile strength and elongation has been achieved for dynamic packing injection molded samples. In addition, step cycle tests showed typical “Mullins effect” for both conventional injection-molded samples and dynamic packing injection molded samples but improved fatigue resistance for dynamic packing injection molded ones. To isolate the contribution of PP matrix orientation and nanoscale EPDM particle on the tensile behavior of PP/EPDM TPVs, thermal annealing of injection molded samples were carried out to eliminate the orientation of PP matrix. It was found that the tensile strength is decreased but the elongation at break is maintained after annealing of dynamic packing injection molded samples. By comparing the property change before and after annealing, it is concluded that the orientation of PP matrix is in great favor of Young's modulus and tensile strength while the enhanced elongation at break is directly corresponding to the decreased rubber size and improved dispersion in TPVs. Our work demonstrates the strong effect of melt shearing on the breakup of rubber particles and matrix orientation of TPVs as well. The isolation of the contribution of PP matrix orientation and rubber particle size on the tensile behavior of TPVs provides guidance for the preparation of new TPVs with high performance.

Rubber particle size and type effects on scratch behavior of styrenic-based copolymers

Effects of rubber particle size and type on scratch performance were investigated using two types of styrenic copolymers: acrylonitrile styrene acrylate (ASA) and acrylonitrile butadiene styrene (ABS). ASAs with rubber particle sizes of 100 nm and 1 μm, respectively, and ABS with rubber particle size of 100 nm were examined. Linearly increasing normal load scratch tests were performed according to the ASTM D7027/ISO 19252 standard. A noticeable drop in scratch resistance is found in ASA with 100 nm rubber particles when compared to ASA containing 1 μm rubber particles. ABS is observed to exhibit a higher scratch resistance when compared to ASA with comparable rubber particle size. Detailed deformation and damage mechanisms have been investigated to explain the observed differences in scratch performance of the model systems. Implication of the present findings for design of scratch resistant polymers is discussed.

Tough semiconductor polycarbonate/multiwalled carbon nanotubes nanocomposites by rubber modification

Tough polycarbonate (PC)/multiwalled carbon nanotube (MWCNT) nanocomposites (NCs) modified by a maleated styrene/ethylene–butylene/styrene (mSEBS) rubber were obtained in the melt state using a highly dispersed PC/MWCNT master-batch. An electrical percolation threshold (pc) occurred at only 0.5% MWCNT showing a power law critical exponent of 2.60, which is characteristic of a three-dimensional percolated structure. The presence of MWCNT decreased the rubber particle size due to an increase in matrix viscosity. In addition to high electrical conductivity, the elastic modulus of the NCs was similar to that of the PC, as a result of the combined presence of 0.5% MWCNT and 4% mSEBS; the mSEBS was also able to provide (i) considerable impact strength, (ii) clear ductile behavior and (iii) increased resistance against crack propagation.

Biomodification of Rubberized Asphalt and Its High Temperature Properties

Asphalt rubber has been commonly used in the United States for modifying asphalt binder. There have been several studies on improving the interaction and adhesion between rubber and asphalt matrix. The modification of asphalt binder with crumb rubber (CR) is mainly controlled by the exchange equilibrium between components of asphalt binder and CR. This phenomenon increases the size of rubber particles (swelling) up to three times their original size and leads to a significant increase in the viscosity of the resulting asphalt. Swelling and increased viscosity not only promote separation of the modified matrix into two distinguishable phases but also increase the difficulty of pumping and application of rubberized asphalt. This study investigated the effectiveness of treating rubber with an amide-enriched biomodifier to facilitate breakage of disulfide bonds in rubber polymer while promoting interactions between free radicals and amide groups of biomodifier. Promoting interactions between rubber polymer and asphalt aromatic compounds by adding a biomodifier could alleviate phase separation while enhancing overall matrix elasticity. This modification enhanced the rheological properties of rubberized asphalt, including high-temperature properties as well as its palpability. The rotational viscometer and dynamic shear rheometer were used to evaluate the effect of biomodifier on the rheological properties of asphalt rubber at high and intermediate temperatures. Fourier transform infrared spectroscopy was used to examine the presence of rubber polymer compounds inside the asphalt matrix. The results showed that introduction of biomodifier facilitated the application of higher CR percentages while improving the overall rheological properties of the asphalt rubber.

Properties of concrete prepared with waste tyre rubber particles of uniform and varying sizes

Investigations and research into the recent use of rubber particles in concrete has been well documented. However, information on the rubber particle sizes or their distributions within concrete which may also influence the concrete properties is still limited. In this study, three groups of singly-sized rubber particle samples (3 mm, 0.5 mm and 0.3 mm) and one sample of continuous size grading (prepared by blending the three singly-sized samples to form the same particle distribution curve of sand) were used to replace 20% of the natural fine aggregate by volume. The reference concrete containing 100% sand was also prepared to compare its properties with those of the samples in terms of workability, fresh density, compressive strength, tensile splitting strength, flexural strength and water permeability. The experimental results demonstrated that the rubber particle size affects the concrete's workability and water permeability to a greater extent than the fresh density and strength. Concrete with rubber particles of larger size tends to have a higher workability and fresh density than that with smaller particle sizes. However, the rubber aggregates with smaller or continuously graded particle sizes are shown to have higher strengths and lower water permeability.

Experimental Study on Carbonation Resistance of Waste Rubber Concrete

The experiment study on the effect on the waste rubber concrete carbonization resistance performance from using three different doses of rubber which is 5%, 10%, 15% and three different rubber particle size which is 2-4 mm, 30-40 mesh, 60-80 mesh .The conclusion is that the concrete adding rubber particles had an adverse effect on early carbonation resistance of concrete, but late can make concrete carbonation resistance ability raise; Different rubber particle size and different influence on concrete carbonation resistance ability, 10% rubber content effect is the best, and the smaller the particle size of rubber particle concrete carbonation resistance ability of the better the results.

Viscous properties, storage stability and their relationships with microstructure of tire scrap rubber modified asphalt

Recycled-polymer modified asphalt has been extensively used in road construction, especially the recycled tire scrap rubber-modified asphalt (TSRMA). However, the main problem during the application of TSRMA is poor storage stability which finally affects the service performance of the pavement. The objective of this work is to evaluate viscous properties, storage stability and morphology of TSRMA and to reveal the relationship of microstructure with rheological behavior and storage stability. With this aim, two different penetration grade asphalts were modified by rubber particles with various mean diameter in a four-paddle mixer at 170°C. Steady state flow measurements, frequency sweep tests in linear viscoelastic region, storage stability tests as well as fluorescence microscopy were carried out on mixes. Rheological evaluation reveals that the addition of tire scrap rubber to asphalt lead to a significant increase in viscosity at 60°C, improving rutting or permanent deformation resistance. Furthermore, the increase in particle size causes an enhancement in viscosity and the steady flow behavior tend to turn into non-Newtonian fluid with increasing particle size and temperature. Storage tests presented that the viscosity of samples obtained from the bottom section of a tube are always higher and the difference also becomes significant as the increase of rubber particles size, tending to poor stability. Fluorescence microscopy shows that dispersed particles in asphalt are the elongated features or strip-type and the aspect ratio (length/diameter) increases with particle size. In addition, smaller particle tend to be unobvious in matrix under microscopy view, indicating improved compatibility between rubber and asphalt.

Efeito do Compatibilizante SBS e da Granulometria nas Propriedades Mecânicas de Blendas de PS/Resíduo de Borracha (SBRr)

One way to modify the properties of polymer systems is to mixture one or more polymer and/or copolymers, i.e., to obtain polymer blends. The aim of this work was to produce polymer blends from a polystyrene matrix with rubber wastes, aiming to study the effect granulometry and compatibilizer on the mechanical properties and impact strength. The blends of polystyrene/rubber wastes were prepared in a corrotacional twin screw extruder and subsequently the extruded granules were injection molded. It was shown that 5 wt% of the SBS compatibilizer optimized the results of impact strength for ternary blends. The elastic modulus of the systems decreased in relation to modulus of the pure polystyrene matrix. The granulometry influenced significantly the property of impact resistance for the compatibilized blends, with a finer rubber particle size that have the best results. These results show a good alternative for toughening of polystyrene, as well as reduce costs using rubber wastes that would otherwise be discarded.

Abrasion and freezing–thawing resistance of pervious concretes containing waste rubbers

The study presented herein investigates the effects of particle size and volume content of waste tire rubber on the flexural strength, abrasion and freezing thawing resistances of pervious concretes. Two types of scrap tire rubber wastes, namely crumb rubber and tire chips, were used in the production of rubberized pervious concretes obtaining by partially replacing of single sized natural coarse aggregate with equivalent volume of rubber. The study was conducted at constant water-to-cement ratio of 0.27 with cement content of 450kg/m3. The rubberized pervious concretes were produced by replacing the tire chips, crumb rubber and fine crumb rubber, which was obtained by sieving the crumb rubber from 1-mm sieve, at two different contents of 10% and 20%. Also, tire chips–crumb rubber and tire chips–fine crumb rubber mixtures were utilized in the rubberized pervious concrete production at same contents. Pervious concrete samples with and without tire rubber were tested for flexural strength, abrasion and freezing–thawing resistances. The test results revealed that use of rubber significantly enhanced the abrasion and freezing–thawing resistance while it decreased the flexural strength of the pervious concretes.

Study on Tension and Compression Ratio and Discount Ratio of Rubber Modified Silica Fume Concrete

This paper conducted all kinds of performance testing of different rubber particle size and different dosage of silica fume rubber modified cement concrete under the condition of 10% the silicon ash content, such as: analysis research of compressive strength, splitting tensile strength, flexural strength, and pull off the pressure ratio and pressure ratio. Experimental results show that silica fume can improve rubber concrete compressive strength, splitting, bending strength, the folding ratio, adding silica fume concrete fracture pressure ratio and compression ratio are improved; the silica fume can effectively improve large brittleness and lack toughness of concrete, and improve the compactness of concrete.

Mechanical properties and constitutive equations of concrete containing a low volume of tire rubber particles

Uniaxial compressive tests were conducted for a low-volume tire rubber concrete (RC) with different rubber volume content levels and particle sizes (five of each). The influence of rubber content and particle size on the mechanical properties of RC was investigated, including axial compressive strength, elastic modulus, peak strain, ultimate strain, appearance of visible cracks and failure pattern of specimens. The mechanical analysis of test results was conducted based on uniaxial compressive stress–strain curves. Uniaxial compressive constitutive models of low-volume rubber concrete were established that included axial compressive strength, peak strain and constitutive parameters a and b. There was obvious regularity between constitutive parameters a and b, rubber content and rubber particle size. Moreover, the physical meanings of constitutive parameters a and b were given, and the established constitutive models were evaluated by tests. The test results demonstrate that the constitutive models have not only good predicting ability and high accuracy but also nice applicability within the limit of 50kg/m3 rubber content. The constitutive models were then improved by introducing the sand rate reduction factor k to reflect the influence of rubber additives. The improved constitutive models are able to predict the performance of concrete with low amounts of rubber.

Properties of Waste Tire Rubber Powder

Scrap tires are abundant and alarming waste. The aggregates resulting from the crushing of the waste tires are more and more used in the field of civil engineering (geotechnical, hydraulic works, light concretes, asphaltic concretes, etc.). Depending on the type of the used tires, dimensions and possible separations and treatment, the physical and mechanical characteristics of these aggregates might change. Some physical, chemical and direct shear tests were performed on three gradation classes of waste tire rubber powder. The tests results were combined with data from previous studies to generate empirical relationships between cohesion, friction angle and particle size of waste tire powder rubber. A cubic (third order) regression model seems to be more appropriate compared to linear and quadratic models.

Experimental Investigation on Modal Response of Woven Fabric Carbon Composite Plate Reinforced with Particles of Micro Rubber Blended Epoxy Matrix under Free Vibration Condition

Vibration damping is proving important for improved vibration control and dynamic stability in advanced engineering systems like aerospace systems, automobiles and in ship building industry. In the present investigation, vibration characteristics of woven fabric carbon composite plate reinforced with micro rubber particle blended into epoxy matrix is studied for enhancing the vibration damping performance. Test Specimens are fabricated in the form of hand layup method. CTBN rubber particle size of 5μm is selected and added to the epoxy matrix for fabricating carbon/epoxy composite plates. Rubber particles of 3% & 15 % by weight were considered as blended percentage in epoxy matrix and compared with 0% addition of rubber particles for understanding and analyzing the vibration characteristics and its difference in damping performance. Vibration damping and modal responses of various kinds of prepared plates were studied and compared. Among tested samples, carbon/epoxy composite plate with 15 wt % micro rubber particle by weight showed very good damping performance.

Effect of Rubber Particles on Properties of Pseudo-Ductile Cementitious Composites

Pseudo-ductile cementitious composites (PDCC) are a new type of special discontinuous random-fibers reinforced cementitious composites with high tensile ductility achieved by the uniform formation of multiple cracks along the length of the specimen. In the present study, rubber particle was introduced into the cementitious composites as the artificial flaw. The tensile properties, compressive strength, water permeability and shrinkage of PDCC with various volume contents and size of rubber particles were measured. The test results show that incorporation of rubber particle will reduce the compressive strength and first cracking strength of PDCC. With increased size and volume of rubber particles, the compressive strength is increased. To achieve maximum tensile ductility, optimum rubber content and size should be employed. Water permeability is found to be similar for various PDCC mixes with or without rubber addition. The content of rubber particle plays a significant role on the dry shrinkage of PDCC, while the particle size only has a slight effect.

Improvement in toughness of polylactide by melt blending with bio-based poly(ester)urethane

Polylactide (PLA) was successfully toughened by blending with bio-based poly(ester)urethane (TPU) elastomers which contained bio-based polyester soft segments synthesized from biomass diols and diacids. The miscibility, mechanical properties, phase morphology and toughening mechanism of the blend were investigated. Both DSC and DMTA results manifested that the addition of TPU elastomer not only accelerated the crystallization rate, but also increased the final degree of crystallinity, which proved that TPU has limited miscibility with PLA and has functioned as a plasticizer. All the blend samples showed distinct phase separation phenomenon with sea-island structure under SEM observation and the rubber particle size in the PLA matrix increased with the increased contents of TPU. The mechanical property variation of PLA/TPU blends could be quantitatively explained by Wu’s model. With the variation of TPU, a brittle-ductile transition has been observed for the TPU/PLA blends. When these blends were under tensile stress conditions, the TPU particles could be debonded from the PLA matrix and the blends showed a high ability to induce large area plastic deformation before break, which was important for the dissipation of the breaking energy. Such mechanism was demonstrated by tensile tests and scanning electron microcopy (SEM) observations.

Application of artificial intelligence to modelling asphalt–rubber viscosity

The viscosity of binder is of great importance during the handling, mixing, application and compaction of asphalt in highway surfacing. This paper presents experimental data and the application of artificial intelligence techniques (statistics, artificial neural networks (ANNs) and fuzzy logic) to modelling of apparent viscosity in asphalt–rubber binders. The binders were prepared in the laboratory by varying the rubber content (RC), rubber particle size, duration and temperature of mixture in conformity with a statistical design plan. Multi-factorial analysis of variance showed that the RC has a major influence on the viscosity observed for the considered interval of parameters variation. When only limited experimental data of design matrix are available for modelling, the fuzzy logic model is the best model to be used. In addition, the combined use of ANN and multiple regression analysis improved the characteristics of the neural network.