Rubber Particle Size Research Articles

Effects of Rubber Size on the Cracking Resistance of Rubberized Mortars.

This study investigated the cracking resistance of rubberized cement-based mortars. Three rubber particle sizes were used: Rubber A (major particle size 2–4 mm), Rubber B (major particle size 1–3 mm), and Rubber C (major particle size 0–2 mm). Traditional restrained ring shrinkage test (RRST), new restrained squared eccentric ring shrinkage test (RSERST), mechanical test, and scanning electron microscopy test were conducted. Results showed that the cracking inhibitory effect of Rubber B was the highest among the three rubber particle sizes. SEM results revealed that the particle size of the rubber does not have much effect on the ITZ (interfacial transition zone) position of rubber and cement paste. For the strength differences of the three types of rubberized mortar, it is mainly because the specific surface area increased as the rubber size decreased, which lead to more ITZ positions and pore structures. Our study verified that RSERST can predict the cracking position and shorten the test period. Compared with RRST, RSERST can also increase the restriction degree. is defined as the intensification factor of RSERST restriction degree. The average intensification factor is .

Evaluation of microcracks in the interfacial transition zone of recycled rubber concrete

AbstractThis work focuses on the feasibility of recycling waste tire rubber aggregates into recycled concrete. The performance of interface transition zone (ITZ) is a key factor affecting the mechanical properties and durability of concrete. The influence of rubber particle size (5–10, 10–20, 20–50, and 50–90 mesh) and volume fraction of rubber aggregate (0, 10, and 20%) on the ITZ of common and rubber aggregate‐cement pastes was studied. Scanning electron microscopy was used to observe the microstructure of recycled rubber concrete cured at constant temperature and humidity for 28 days. Moreover, the size of microcracks in the ITZ area was evaluated. Results showed that the crack width of the ITZ between the rubber and cement paste (ITZ‐R) and between the ordinary aggregate and cement paste (ITZ‐S) showed similar variation patterns. The addition of 50–90 mesh rubber powder improved the ITZ micro‐crack structure of rubber concrete. Increasing the rubber content and particle size also increased the microcrack width of ITZ. The size of rubber aggregate was the key factor affecting the crack width in ITZ. Finally, the addition of rubber inhibited the hydration degree of cement, reduced the formation of hydration products in ITZ and substantially affected ITZ‐R.

Effect of Silicone Rubber of a Waste Composite Insulator on Cement Mortar Properties.

Due to the rapid growth of the electric power system, the silicone rubber composite insulator is so widely employed around the world. However, the aging damage and decommission of it inevitably generates plenty of waste silicone rubber. It takes up large amounts of land for non-degradation, which is becoming a serious environmental issue. In this paper, the effort has been made to reuse the silicone rubber of composite insulator by peeling, breaking and adding it into the cement mortar to partly replace river sand by 5%, 10%, 15%, 20% and 30% in volume. Moreover, the surface modification of silicone rubber particles with H2O2 and KOH is explored to improve hydrophilicity. The mechanical strength of silicone rubber mortar and modified silicone rubber mortar are measured in detail, and the effects of particle size, content and modification of silicone rubber on the properties of mortar are investigated. This study shows that at least a 5% addition of silicone rubber can reduce the strengths, while the 15% addition is obviously favorable for increasing the toughness. Furthermore, the mortar strength gets promoted due to the surface modification. Lastly, the superior thermal insulation and noise reduction of the mortar are obtained as the addition of silicone rubber particles, and an equation between dry apparent density and thermal conductivity of mortar has been developed.

An Experimental Study on Mechanical and Thermal Insulation Properties of Rubberized Concrete Including Its Microstructure

This study aimed to investigate the effects of the size and weight content of waste rubber particles on the relevant performances of rubberized concrete. First, the fine aggregates were partially replaced by rubber particles of different sizes to produce rubberized concrete. Secondly, the mechanical and thermal insulation properties of rubberized concrete were investigated. Finally, microstructural analyses of rubberized concrete including scanning electronic microscope (SEM) and energy distribution spectroscopy (EDS) were examined. Experimental results indicated that uniaxial compressive strength of rubberized concrete was reduced, while the peak strain was gradually increased and thermal insulation properties were improved with the increase of rubber content or decrease of rubber particle size. In addition, rubber particles affected the failure modes, endowing concrete with weak brittleness and strong cracking resistance. Additionally, it was observed that the interfacial adhesion between the matrix rubber and the aggregates was weak under SEM, which seemed to be a key factor that reduced the strength of rubberized concrete.

Physical and tribo-mechanical properties of waste rubber tyre/epoxy composites

Waste tyre rubber/epoxy composites were prepared with 15, 30 and 45 wt% of recycled waste tyre rubber (WTR) particles (size:100 μm, 200 μm, and 300 μm) as fillers in the epoxy matrix by open moulding method followed by post-curing at elevated temperature. The physical, mechanical and sliding wear behaviour of the composites were investigated. Due to the addition of WRT filler in epoxy enhanced its sliding wear resistance and reduced the modulus of the composites. it is found that both the quantity and particle size of WTR influenced on wear rate. Addition of 15 wt% WRT filler enhanced the tensile strength of the epoxy composite, further addition WRT filler deteriorates the tensile strength. Also, investigated the structure-property correlation and observed no correlation between mechanical properties and specific wear rate of WRT/epoxy composites. The morphological study was performed on tensile fractured and on the worn-out surfaces. The investigation revealed that the recycled WTR particles could be used as fillers for epoxy composites and it has potential applications like flooring and anti-corrosion coating, as well as an electrical insulating.

Synthesis of high impact polystyrene: the eff ect of butadiene rubber molecular parameters

The eff ect of butadiene rubber molecular parameters on conversion dependencies and viscosity characteristics of the process of graft copolymerization of styrene, microstructure and quality indicators of the synthesized samples of impact-resistant polystyrene was studied. It is testifi ed that an increase in the molecular mass of the elastomer does not aff ect the monomer conversion, however, it leads to a phase inversion shifting to the region of lower conversion degrees of styrene. In this case, an increase in the size of rubber particles and an increase in the content of the gel fraction are observed in the copolymer. The established changes in the microstructure correlate with the properties of high-impact polystyrene.

THERMOPLASTIC VULCANIZATES BASED ON DYNAMICALLY VULCANIZED POLYPROPYLENE/CARBOXYLATED NITRILE RUBBER BLENDS

ABSTRACT Thermoplastic vulcanizates (TPVs) based on polypropylene (PP) and carboxylated nitrile rubber (XNBR) with improved mechanical properties were prepared by dynamic vulcanization using dicumyl peroxide (DCP) in combination with N,N′-m-phenylene-bis-maleimide (BMI) as a cross-linking system. The effect of PP grafted with maleic anhydride (PP-g-MA) or with glycidyl methacrylate (PP-g-GMA) and triethylene-tetramine (TETA) as the compatibilizing systems on the mechanical, morphological, and dynamic mechanical properties of PP/XNBR blends was investigated. Experimental results revealed that PP-g-GMA has a better compatibilizing efficiency. Tensile strength and elongation at break presented a significant improvement with the addition of 2.5 to 7.5 phr of this functionalized PP. The improvement of the tensile properties was observed for all blend compositions studied. Also the tensile properties of the blends did not change considerably after three reprocessing cycles, confirming the efficiency of this system as a TPV. The presence of PP-g-GMA also resulted in an increase of the apparent melt viscosity of the corresponding TPVs, confirming the reactive compatibilization. A decrease in rubber particle size with the presence of PP-g-GMA was also observed by scanning electron microscopy.

Effects of inclusion of granulated rubber tires on the mechanical behaviour of a compressive sand

Drained triaxial shearing tests were performed on a well-graded compressive sand (completely decomposed granite, CDG) and its mixtures with granulated rubber tires to investigate the effects of rubber size and content on their mechanical behaviour. Three sizes of rubber particles, GR1, GR2, and GR3, were used with size ratios to CDG (D50,rubber : D50,CDG) of 0.9, 3.5, and 7.2, respectively, and the rubber content ranged from 0% to 30%. The results show that for CDG–GR1 mixtures, the strength decreases with increasing rubber content, while for CDG–GR2 and CDG–GR3 mixtures, the strength decreases only at 10% rubber content and then increases markedly with increasing rubber content. The increase of strength is mainly because the inclusion of large rubber particles widens the particle size distributions of the mixtures, resulting in denser packings. The denser packings also lead to a decrease in compressibility. At larger size ratio and higher rubber content, the CDG–rubber mixtures show higher shear strength and lower compressibility than pure CDG, which indicates the CDG–rubber mixtures are very suitable to be used as filling materials.

Crumb Rubber Modifier in Road Asphalt Pavements: State of the Art and Statistics

Tire rubber recycling for civil engineering applications and products is developing faster, achieving increasingly higher levels of maturation. The improvements in the material circle, where crumb rubber, generated as a by-product of the tire rubber making process, becomes the resource used for the construction of road asphalt pavement, is absolutely necessary for increasing the sustainability of the entire supply chain. The paper reports the results of an accurate data analysis derived from an extensive literature review of existing processes, technologies, and materials within construction of infrastructure. The current position, the direction, and rate of progress of the scientific efforts towards the reuse and recycling of tire rubber worldwide have been shown. Furthermore, an in-depth analysis of a set of important properties of Crumb Rubber Modified Asphalt has been carried out—fabrication parameters, standard properties, high and low-temperature performance, and rheological properties. Statistics over a sample of selected publications have been presented to understand the main processes adopted, rubber particle size, temperatures, and possible further modifications of crumb rubber modified binder.

Study of Devulcanised Crumb Rubber-Peat Bio-Based Composite for Environmental Applications

A proper recycling and secondary reuse of end-of-life car tires (ELTs) remain an important issue for many regions. Devulcanised crumb rubber as a product of ELT recycling could be used for very different applications, including site remediation by spilled oil products. In current paper a development of new bio-based composite material containing devulcanised crumb rubber and cenospheres is suggested. Designed bio-based composite can be used as a oil spill adsorbent, material for civil engineering, and as a raw material for further modification by introduction of ferromagnetic components. Homogenised peat with peat content 14.0 ± 1.5 wt%, particle size 0.01 – 0.5 mm used as a natural bio-based binder. Devulcanised crumb rubber particle size 1.0 – 4.0 mm was used as a porous substrate. Designed compositions contained 5, 10, 15, 20 wt% (before drying) of devulcanised crumb rubber. Cenospheres have duplex function for designed composite: lightweight additive that makes final product floatable, and at the same time minimises shrinkage of dried product. It was found that devulcanised crumb rubber reduces density of final composite and adding open porosity. Developed bio-based composites could be manufactured in granules by drum granulation technique for further environmental applications. Formability and apparent density of bio-based composite are studied.

Storage, fatigue and low temperature characteristics of plasma treated rubberized binders

Abstract Crumb rubber modified (CRM) asphalt has been increasingly used in highway and airfield pavements due to its great mechanical behavior. However, the poor storage stability limits its application. It has been proved that plasma technology can effectively improve the surface characteristics of polymer. Therefore, this study introduced low temperature plasma (LTP) to modify the surface of crumb rubber for improving its adhesion. In this study, a series of laboratory tests, including hot storage test, linear amplitude sweep (LAS) test and bending beam rheometer (BBR) test, were carried out. Then storage stability, fatigue resistance and low temperature rheological property of LTP treated and untreated CRM binders were explored to evaluate the impact of LTP treatment, rubber content, particle size and binder source. The results indicated that the LTP treated rubberized binders showed enhanced storage stability (except for 20% content) and fatigue property, while its low temperature performance had a slight change. Moreover, the increased rubber content from 10% to 20% had a positive effect on aforementioned properties after LTP treatment. Specially, the critical low temperature tended to increase linearly as CR content increased within the scope of 10–20%. In addition, the fatigue performance increased with a great rubber particle size while the storage stability was on the contrast. Furthermore, after a LTP treatment, the softer crumb rubberized binder showed improved low temperature performance and weakened fatigue resistance.

Study on Influence of Waste Tire Rubber Particles on Concrete Crack Resistance at Early Age

Two groups of variables, the amount of rubber particles and the size of rubber particles, were set up to evaluate the early crack resistance of rubber concrete after 24 hours of forming. Combined with the test results, the influence of the amount and particle size of rubber particles on the early crack resistance of concrete is analyzed. The experimental results show that the early crack resistance of concrete increases with the decrease of the size of rubber particles when the content of rubber particles is small, but decreases first and then increases when the content of rubber particles is large. When the size of rubber particles is large, the early crack resistance of concrete increases with the increase of the content of rubber particles, on the contrary, decreases first and then increases.

A Study of the Impact Resistance of Rubber Concrete at Low Temperatures (−30°C)

In the present study, the impact resistance of rubber concrete at low temperatures (−30°C) was examined. The initial and ultimate crack impact times and the ductility indexes were evaluated. This study’s specimens were prepared by adding two different sizes of rubber particles (20 mesh and 50 mesh) in different ratios (0%, 5%, 10%, 15%, and 20%) at both 25°C and −30°C. The concrete specimens were evaluated using a drop hammer weight test method. The results showed that the initial and ultimate crack impact times and ductility indexes of the rubber concrete specimens had decreased at −30°C. Also, the decrease amplitudes were determined to be lower than those of the reference concrete specimens. Consideration was given in this study to the large variations in the impact values, and a two‐parameter Weibull distribution method was adopted in order to analyze the obtained experimental data. The results had demonstrated that the impact times of the rubber concrete specimens could be described using the two‐parameter Weibull distribution method results.

Physical and Tribo-Mechanical Properties of Waste Rubber Tyre/Epoxy Composites

Waste tyre rubber/epoxy composites were prepared with 15, 30 and 45 Wt.% of recycled waste tyre rubber (WTR) particles (size:100 µm, 200 µm, and 300 µm) as fillers in the epoxy matrix by open moulding method followed by post-curing at elevated temperature. The physical, mechanical and sliding wear behaviour of the composites were investigated. Due to the addition of WRT filler in epoxy enhanced its sliding wear resistance and reduced the modulus of the composites. it is found that both the quantity and particle size of WTR influenced on wear rate. Addition of 15 Wt. % WRT filler enhanced the tensile strength of the epoxy composite, further addition WRT filler deteriorates the tensile strength. Also, investigated the structure-property correlation and observed no correlation between mechanical properties and specific wear rate of WRT/epoxy composites. The morphological study was performed on tensile fractured and on the worn-out surfaces. The investigation revealed that the recycled WTR particles could be used as fillers for epoxy composites and it has potential applications like flooring and anti-corrosion coating, as well as an electrical insulating.

The effect of polyester recycled tire fibers mixed with ground tire rubber on polyethylene composites. Part I

The effect of polyester recycled tire fibers (RTFs) mixed with ground tire rubber (GTR) in linear low-density polyethylene (LLDPE) with and without styrene–ethylene–butylene–styrene-grafted maleic anhydride was studied. In particular, different RTF contents (10, 25, and 50 wt%) and compounding screw speed (110, 180, and 250 r min−1), as well as temperature profiles (extrusion and injection molding) were used to optimize the processing conditions. In this first part, a complete physical and morphological analysis for the RTF fibers and GTR particles was performed. The results show that the compatibilized compounds have lower RTF length and GTR particle size but better distribution of rubber particles in the LLDPE matrix. Overall, lower processing temperatures used in both extrusion and injection molding showed better interfacial adhesion between the components due to higher shear and mechanical energy imparted on the different particles.

Effect of crumb rubber production technology on performance of modified bitumen

The quality of the bitumen modified with crumb rubber (CR) largely depends on the process parameters when blending CR with bitumen. The larger the specific surface of the CR particles, the better the final properties of the CR-modified bitumen. A novel high-pressure water jet (WJ) based technology has been shown to produce CR with a rougher and larger surface area compared to other traditional techniques such as mechanical shredding (ME) or cryogenic processing (CG). This, in turn, resulted in superior low temperature properties when used as modifier in bitumen. Specifically, the results showed a clear tendency of WJ technology to improve the strength in fracture toughness tests at −10 °C more so than CG and ME. The larger rubber particle size (<1000 µm) the higher the ductility of the material investigated showing improved performance under cold temperatures. From the rheological analysis, it can be concluded that addition of CR to bitumen increases the complex modulus at high temperatures and reduces stiffness at low temperatures. In comparison to SBS polymer modified bitumen there is a flattening of the complex modulus curve indicating less temperature susceptibility. This implies enhanced rutting resistance at high temperatures and enhanced low temperature cracking resistance at low temperatures for CR modified bitumen compared to neat and SBS modified bitumen.

Model construction of particle size in dynamic vulcanization of PVDF/SR blends—matching degree between crosslinking and shearing rates

Abstract Peroxide-induced dynamic vulcanization of poly (vinylidene fluoride)/silicone rubber (PVDF/SR) blends was studied in this paper. We controlled the size of rubber particles by changing the rotor speed, and discussed the influence of shearing on the particle diameter and the particle diameter polydispersity (dp). The size of SR particle was confirmed to be decreased with increasing the rotor speed. However, a good matching degree of shearing and crosslinking rate helped the SR phase to achieve a uniform crosslinking, as well as a narrow dp. In this particular PVDF/SR system, the suitable rotor speed was found to be 90 rpm, at which the dp reached a minimum of 1.1981 and 1.1614 for the P9S1 and the P7S3, respectively. At last, we discussed the influences of the macroscopic breaking energy (Edk) and the coalescence (P) on the number-average particle diameter (Dn) of the SR. This work is thus devoted to construct a model for predicting the particle size in dynamic vulcanization of PVDF/SR blends.

Mechanical Properties, Permeability, and Freeze–Thaw Resistance of Pervious Concrete Modified by Waste Crumb Rubbers

Due to the negative effects that derive from large impervious surfaces in urban areas, pervious concrete has been developed, and has become an environmentally friendly pavement material. As a porous and permeable material, pervious concrete presents an overwhelming advantage in solving urban problems, such as flooding, groundwater decline, urban heat island phenomena, etc. Waste crumb rubber has been verified as a feasible modifier for pavement material. The objective of this paper is to explore the effects of rubber particle size and incorporation level on the permeability, mechanical properties, and freeze–thaw resistance of pervious concrete. Two kinds of rubbers (fine and coarse) with four incorporation levels (2%, 4%, 6%, and 8%) are used in the experiment. Permeability, compressive strength, flexural strength, flexural strain, and freeze–thaw resistance are tested. The results indicate that the addition of rubber slightly decreases strength and permeability, but significantly enhances ductility and freeze-thaw resistance. Fine crumb rubber with a suitable incorporation level could remarkably improve the ductility and freeze–thaw resistance of pervious concrete without sacrificing excessively strength and permeability.

Impact of hybrid composites based on rubber tyres particles and sugarcane bagasse fibres

The paper describes the impact behaviour of hybrid composites made of sugarcane bagasse fibres and disposed rubber particles. The analysis was carried out using a full factorial design (25) on samples subjected to drop-tower testing. The effects of the bagasse fibre treatment, length and weight fraction were considered, as well as the rubber particles size and their amount. Higher weight fractions of coarse rubber particles led to an enhancement of the absorption. Sustained chemical treatments of the bagasse fibres provided an increase of the composites stiffness, reducing therefore the energy absorption. In contrast, higher energy absorption was obtained in composites made with untreated bagasse because of the enhanced fibre pull-out mechanism.

Effect of cement content and recycled rubber particle size on the performance of rubber-modified concrete

ABSTRACTAccording to the Rubber Manufacturer’s Association, the United States generated 3664 thousand metric tons of scrap tires in 2015. While most waste tires are repurposed, approximately 409.5 thousand metric tons were disposed in landfills. This study investigates an alternative use of the waste tires as a replacement of natural aggregates in concrete mixtures. This study investigated fresh concrete properties and compressive strength. Different coarse and fine aggregate rubber particle sizes were evaluated: 19-mm tire chips (TCs) and 30-mesh crumb rubber (CR). TCs were used to replace coarse aggregates, while CR was used to replace fine aggregate in the concrete mixtures in increments of 10% by volume. Concrete strength loss was reduced with a fine aggregate replacement with CR as opposed to greater losses of strength exhibited by a coarse aggregate replacement with TCs. Adequate strengths were achieved at replacement levels as high as 40% by volume with CR, whereas satisfactory strengths were achieved with only a 10% replacement of coarse aggregates with TCs. Acceptable strengths were obtained from mixtures utilizing a combination of the two rubber sizes. Cement content was observed to have greater influence on rubberized concrete compressive strength at lower rubber contents than higher levels.