The effect of lignin dispersion on abrasion resistance in polybutadiene rubber (BR)

In this research work, ethylene-propylene-diene monomer (EPDM)/styrene butadiene rubber (SBR) hybrid composites reinforced with nanoclay (NC) and nanosilica (NS) were prepared and investigated. The synergistic effect of NC and NS on the mechanical properties of the EPDM/SBR hybrid composites was examined. Three different crosslinking systems were used, namely: sulphur, dicumyl peroxide and the mixed system consisting of sulphur and peroxide in this research work. The tensile strength, elongation at break, 100% modulus, tear strength, hardness, rebound resilience, abrasion resistance, compression set, swelling resistance and microstructure of the EPDM/SBR hybrid composites were evaluated. The concentration nanosilica along with nanoclay plays a most vital role in the micro-structural, mechanical and other properties of the nanocomposites. From the study, it was clear that the nanocomposites containing 7.5 parts per hundred rubber (phr) of nanoclay and 4 phr of nanosilica shows a maximum mechanical properties along with its abrasion and swelling resistance characteristics. In particular, the sulphur cured EPDM/SBR hybrid composites containing nanoclay and nanosilica results in best mechanical properties and abrasion resistance.

The main objective of the current research work is to explore the effect of nanosilica particles on the compound EPDM/SBR-SiO2 (ethylene-propylene-diene monomer/styrene-butadiene rubber-nanosilica). The composite EPDM/SBR with and without silane coupling agent was processed using an open mill mixer. The nanosilica particles are prepared in the laboratory and were used as the reinforcing material in EPDM/SBR rubber composites. The cure characteristics, mechanical properties, hardness, rebound resilience, swelling resistance, abrasion resistance and compression set of the composites are completely analyzed and studied. Nanosilica particles are produced in the laboratory and used as reinforcement material in EPDM/SBR rubber compounds. Fully analyzed and examined are the cure characteristics, mechanical properties, hardness, rebound resilience, swelling resistance, abrasion resistance and compression collection of the composites. It was also evident from the result that with the inclusion of nanosilica particles in the EPDM/SBR rubber composites, the mechanical properties, swelling resistance, hardness, abrasion resistance and compression set properties improved.

Preparation of hexamethyl disilazane-surface functionalized nano-silica by controlling surface chemistry and its “agglomeration-collapse” behavior in solution polymerized styrene butadiene rubber/butadiene rubber composites

The purpose of this study was to investigate the effects of acetyl tributyl citrate (ATBC) on the mechanical properties, abrasion resistance, and cytotoxicity of a polyurethane-based 3D printing resin for mouthguard applications. The synthesized polycarbonate-based polyurethane acrylate was formulated into digital light processing printing resins with 40 wt% triethylene glycol dimethacrylate, and different percentage of ATBC were added for further characterizations. The mechanical properties and abrasion resistance, ATBC migration, and the cytotoxicity of the resins were evaluated. The addition of ATBC in polyurethane-based resins enhanced the flexibility of printed resins. ATBC of 5-10% increased the toughness of printed resins, and the elongation at break. The printed resins with ATBC show higher hardness, comparing to conventional mouthguard materials, and have flexibility at meantime. All resins with ATBC showed no cytotoxicity and extremely low plasticizer migration, suggesting that ATBC have potential in long-term applicability. This is one of the few studies that shows the potential of adding ATBC into light-cure 3D printing resins. This study indicates that adding ATBC not only can tune the mechanical properties of 3D printing resins, but it can also showed low migration and did not increase the cytotoxicity in 3D printing resins.

Hydrophobic polymers such as polyethylene and polypropylene are very difficult to use for preparing nanocomposites without a compatibilizer. However, in this study, polybutadiene rubber (BR; a hydrophobic polymer) nanocomposites were produced successfully without a compatibilizer with a melt‐compounding method. Transmission electron microscopy showed an intercalated and exfoliated clay morphology in the polymer matrix, which led to increased mechanical properties. The tensile and tear strengths of the BR/Cloisite 20A hybrids were 4.4 times and 2 times larger than that of BR, respectively. The rebound resilience, compression set, and abrasion resistance were also improved by the addition of organoclay. The abrasion resistance of BR/Cloisite 20A was approximately 2 times larger than that of BR. The cure time (t90), scorch time (t2), and their difference (t90 − t2) of the BR/organoclay hybrids were much reduced than those of BR. Thus, organoclays behaved as good fillers and effective accelerant agents for BR vulcanization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2062–2066, 2006

Copper matrix composites reinforced by aligned carbon nanotubes: Mechanical and tribological properties

Two-stage concrete (TSC), also known as prepacked aggregate concrete (PAC), differs from traditional concrete in terms of site application and manufacturing process. Although this type of concrete is not a replacement for conventional concrete applications, it is an ideal option for unusual and difficult placing conditions, especially for repairing existing concrete structures. In other words, this type of concrete is a newly developed concrete and made by placing and packing coarse aggregates and fibres in a designed formwork, then injecting a cement grout mixture into the free spaces between the aggregate particles using gravity or a pump device. For the mentioned system and others, concrete components used as floors or pavements must have an adequate degree of roughness during service life when exposed to skid and abrasion. Thus, this research work introduced a new concrete method (prepacked aggregates fibre-reinforced concrete—PAFRC) with high abrasion and skid resistance reinforced with waste polypropylene (PP) fibres from the carpet industry. The effects of PP fibres at 0–1% dosages on the mechanical properties, abrasion resistance, and skid resistance of PAFRC mixes were studied. The results revealed that the addition of PP fibres reduces the compressive strength of concrete mixtures. Nonetheless, the presence of PP fibres results in PAFRC mixes having higher tensile strength, abrasion resistance, and skid resistance than plain concrete. It was detected that in both grouting methods (gravity and pump), with the addition of PP fibre up to a specific dosage, the resistance against abrasion and skid was increased by about 26% compared to plain PAC mix. Additionally, the outcomes indicated that PAFRC is a promising material for applications such as pavements with high abrasion and skid resistance.

Abrasion resistance and cracking resistance are two important properties determining the normal operation and reliability of hydropower projects that are subjected to erosion and abrasive action. In this study, polyvinyl alcohol (abbreviated as PVA) fiber and magnesium oxide expansive agents (abbreviated as MgO) were used together to solve the problems of cracking and abrasive damage. The effects of PVA fiber and MgO on the mechanical property, abrasion and cracking resistance, pore structures and fractal features of high-strength hydraulic concrete were investigated. The main results are: (1) The incorporation of 4–8% Type I MgO reduced the compressive strength, splitting tensile strength and the abrasion resistance by about 5–12% at 3, 28 and 180 days. Adding 1.2–2.4 kg/m3 PVA fibers raised the splitting tensile strength of concrete by about 8.5–15.7% and slightly enhanced the compressive strength and abrasion resistance of concrete. (2) The incorporation of 4–8% Type I MgO prolongs the initial cracking time of concrete rings under drying by about 6.5–11.4 h, increased the cracking tensile stress by about 6–11% and lowered the cracking temperature by 2.3–4.5 °C during the cooling down stage. Adding 1.2–2.4 kg/m3 PVA fibers was more efficient than adding 4–8% MgO in enhancing the cracking resistance to drying and temperature decline. (3) Although adding 4% MgO and 1.2–2.4 kg/m3 PVA fibers together could not enhance the compressive strength and abrasion resistance, it could clearly prolong the cracking time, noticeably increase the tensile stress and greatly lower the racking temperature; that is, it efficiently improved the cracking resistance to drying and thermal shrinkage compared with the addition of MgO or PVA fiber alone. The utilization of a high dosage of Type I MgO of less than 8% and PVA fiber of no more than 2.4 kg/m3 together is a practical technique to enhance the cracking resistance of hydraulic mass concretes, which are easy to crack. (4) The inclusion of MgO refined the pores, whereas the PVA fiber incorporation marginally coarsened the pores. The compressive strength and the abrasion resistance of hydraulic concretes incorporated with MgO and/or PVA fiber are not correlated with the pore structure parameters and the pore surface fractal dimensions.

Dam concrete suffers from serious abrasion damages in southwestern China, the abrasion resistance of concrete is therefore one of the most important factors determining the reliability even the safety of the dams. In the present work, the effects of fly and/or silica fume on the mechanical properties, drying shrinkage, as well the cracking and abrasion resistance of concrete were investigated, then the pore structures of concrete added with fly ash and silica fume and the pore surface fractal dimensions ([Formula: see text]) were determined by the mercury intrusion porosimetry (MIP) method and a fractal model, respectively. Finally, the relationships between the abrasion resistance of concrete and the porosity as well as the [Formula: see text] were revealed and discussed. The results indicate that silica fume significantly increases the drying shrinkage especially at early age, while the incorporation of fly ash and silica fume together can decrease the early plastic shrinkage-induced cracking risk and the final shrinkage to some degrees. Besides, the utilization of 5[Formula: see text]wt.% silica fume and 20[Formula: see text]wt.% fly ash together increases the abrasion resistance and mechanical property by about 4–9% at various ages. In addition, the compressive strength and the abrasion resistance of concrete are linearly correlated with the concrete porosity and the [Formula: see text]. Both the fly ash and silica fume could decrease the porosity of concrete and increase the [Formula: see text], therefore the concrete containing fly ash and silica fume have desired mechanical property and abrasion resistance. Moreover, [Formula: see text] has a more profound effect on the abrasion resistance of concrete than the concrete porosity. The addition of 5[Formula: see text]wt.% silica fume and 20[Formula: see text]wt.% fly ash together is suitable for the concretes used for wearing surfaces in terms of mechanical property, cracking and abrasion resistance.

The vulnerability of non-biodegradable wastes and their exploiting to reduce contamination of environment has been abundantly attracted the engineers’ attention. In addition, the abrasion resistance of concrete pavement is one of the prominent factors of durability causing non-affordable maintenance and rehabilitation costs. Thus, utilizing plastic wastes either as aggregate replacement or fiber is considered as an eco-friendly idea. Recently, numerous studies have been carried out to investigate the effects of PET (with different shapes and sizes) on mechanical properties and durability characteristics of concrete. In the present research, 5%, 10%, 15%, 20%, 25% and 30% by volume fraction of natural river sand in concrete mixes were replaced with recycled PET and specifications of fresh and hardened concrete so as to evaluate mechanical properties and abrasion resistance of concrete specimens. The obtained results revealed that replacing recycled PET aggregates with natural sand decreases slump and fresh density of concrete. Nevertheless, the mechanical properties were degraded as PET content increased. Furthermore, the results that replacing up to 30 percent of PET resulted in reducing compressive, splitting tensile and flexural strength, respectively, 36, 42 and 22 percent compared to control sample. In addition, replacing fine recycled PET improved the abrasion resistance of concrete. According to criteria implied by standards, the experimental results admitted that replacing 20% of fine recycled PET resulted in the most possible mechanical behavior and abrasion resistance.

Given the advantages of the latex compounding method, clay was nanodispersed into a styrene butadiene rubber (SBR) matrix, and butadiene–styrene–vinyl pyridine rubber (VPR) latex was introduced to in situ‐modified clay to support strong interfacial interaction between clay layers and SBR matrix. The strong interfacial interaction was investigated through Fourier‐transform infrared spectra, X‐ray photoelectron spectroscopy, and dynamic mechanical properties. The structure and properties of SBR/VPR/clay nanocomposites were studied through X‐ray diffraction, high‐resolution transmission electron microscope, and mechanical and abrasion testing. The aspect ratio of clay layers was calculated using Halpin–Tsai model. The largely improved mechanical properties and abrasion resistance was adequate evidence that the exfoliated structures with large aspect ratios and strong interfacial interaction play critical roles in nano‐reinforcement. POLYM. COMPOS., 39:2783–2790, 2018. © 2017 Society of Plastics Engineers

This study involves an investigation of the chain transfer reaction of butadiene (Bd) polymerization, under the neodymium tris[bis(2-ethylhexyl)phosphate] (Nd)/diisobutyl aluminum hydride (Al)/ethylaluminum sesquichloride (Cl)/Bd catalytic system. The results show that the chain transfer reaction itself is reversible. Only chain propagation and chain exchange reactions occurred during the later period of polymerization, and there was a linear relationship between the molecular weight and the conversion rate. All polymer chains showed sufficient reactivity to propagate by reacting with the monomer. The degree of the chain transfer reaction can be determined by the amount of Al, and the molecular weight in the synthetic polybutadiene can be accurately designed by the formula Mn=54·Bd/Nd/(0.67Al/Nd-7.17). The catalyst-polymerized butadiene afforded products featuring a relatively narrow molecular weight distribution and a high cis-1,4 stereospecificity. One of these products, polybutadiene rubber, showed narrow distribution in the sample, and exhibited good physical and mechanical properties, low abrasion, and low rolling resistance.

The direct incorporation of ground tire rubber (GTR) as a waste rubber into a virgin polymer matrix causes a remarkable reduction in its mechanical and performance properties. In this work, maleic anhydride-grafted natural rubber (MA-g-NR) was employed as a compatibilizer to improve the interaction between a natural rubber (NR) matrix and GTR. The effect of MA-g-NR on curing characteristics, rheological behavior, morphology, and performance properties of the NR-GTR blend was studied using an oscillating disk rheometer, rheomechanical spectroscopy (RMS), scanning electron microcopy (SEM), and tensile and abrasion testing. The obtained results by RMS and SEM tests revealed better adhesion between NR and GTR in the presence of MA-g-NR. Using up to 8 parts of MA-g-NR caused an increase in the curing rate index, and a remarkable increase in mechanical properties and abrasion resistance was observed, which was comparable to or even better than the virgin vulcanizate.

Carbon nanofibers and PVA fiber hybrid concrete: Abrasion and impact resistance

Plasticized starch/clay composite films were prepared by casting aqueous solutions containing oxidized corn starch, different concentrations of glycerol as a plasticizer and 5% clay (sodium montmorillonite, Na+‐MMT) on the basis of dry starch. The water‐binding properties of the composite films were evaluated by water vapor sorption isotherms at room temperature and various relative humidities (RHs). Mechanical properties and abrasion resistance were also analyzed for the films with varying glycerol contents at 68% RH and room temperature. Changes in water sorption isotherms suggested that glycerol interacted with both water and starch in a complicated way. A saturation phenomenon of glycerol, depending on RH, was observed based on the isotherms. Above this saturation content, phase separation of the system occurred with the appearance of free glycerol. According to mechanical performance and abrasion resistance, as well as water vapor sorption of the starch blend films, the three‐stage transition was presented to be related to the state of glycerol in the blend system, i.e. adsorption of glycerol onto H‐bonding sites of starch, supersaturation of glycerol as plasticizer and further supersaturation of glycerol. Only above the supersaturation content can glycerol play a plasticizer role in starch‐based composites.