Natural Rubber Compounds Research Articles

Fatigue crack growth behavior and morphological analysis of natural rubber compounds with varying particle size and structure of carbon black

AbstractCarbon black (CB) is an essential ingredient of any rubber compound to achieve the desired strength, stiffness, wear, and fatigue resistance. Depending on the function of a tire component (tread, sidewall, apex, etc.), different types of CBs, varying in particle sizes and structures, are used. On prolonged exposure to cyclic loading, rubber compounds lose their strength due to mechanical fatigue. In this study, the fatigue crack growth (FCG) behavior of unfilled and CB‐filled natural rubber compounds is investigated with varying particle size and structure (N115, N134, N220, N234, N330, and N339). FCG properties have been measured using a Tear and Fatigue Analyzer under various strain levels and temperatures. Microscopic analysis revealed that compounds with lower particle size and high structure CB showed better distribution and dispersion of CB throughout the whole matrix. Lower particle size with higher surface area displayed superior FCG resistance compared to the higher particle size CB. FCG of above compounds has also been studied at three different temperatures such as room temperature (25°C), 70°C, and 100°C. Significant increase in FCG rate was observed with increase in temperature due to the thermo‐oxidative degradation and reduction of strain‐induced crystallization.

Effects of Natural Rubber Compound and Crumb Rubber on Mechanical and Morphological Properties of Biodegradable Poly(butylene succinate)

Natural rubber compound was melt-mixed with biodegradable poly(butylene succinate) (PBS) using an internal mixer. The effect of natural rubber compound (NRC) content on the mechanical properties of PBS was examined. The amount of NRC of 0, 5, 10 and 15 percentage by weight were used. Moreover, crumb rubber (CR) of 5 phr was added into the blend of PBS/NRC (85/15). After mixing, the samples were ground with a grinder and formed to specimen test by hot compression molding. The results of the mechanical tests showed that NRC enhanced the toughness of PBS matrix. As a result, the elongation and impact resistance values increased. However, maximum tensile strength and the modulus of elasticity decreased with an increase in the NRC content. The addition of CR in the PBS/NRC blend resulted in a reduction of all mechanical properties. The morphology of the fractured surface was investigated by scanning electron microscope. It could be seen that the NRC had a good dispersion in the PBS matrix while the CR did not show good interfacial adhesion with the PBS matrix.

The effect of silica filler quartz sand from tailing processing of mining material on mechanical properties, thermal aging and morphology rubber compound

Tailings as waste from mining material processing contain constituents that have the potential to be exploited economically. Tailings deposits derived from tin mines include quartz sand with a SiO2 content of 98.03%, which can function as a filler for rubber products. This research studied silica quartz sand as a mineral filler in natural rubber (NR) on rubber’s mechanical and thermal aging characteristics. The effect of reinforced filled in NR was observed by varying 0, 10, 20, 30, 40, and 50 phr of the filler. The thermal aging test is carried out at 70 °C and 100 °C for a storage period of 72 hours. SEM micrographs were used to examine morphology. The results showed that using silica quartz sand as a filler improved various properties, including tensile strength, tear strength, elongation at break, hardness, and abrasion resistance. The higher the grinding temperature, the higher the hardness and tensile strength, but the lower the elongation at break. Morphological analysis using SEM micrographs revealed the system’s strengths and weaknesses. The silica particles are homogeneously mixed with natural rubber, according to SEM analysis. According to the findings of this study, the silica of quartz sand from tin mining processing industrial waste can be used as a cost-effective alternative filler in NR compounding.

Influence of benzyl esters of vegetable oils on curing, mechanical and dynamic properties of silica filled natural rubber and styrene-butadiene rubber compounds

Influence of benzyl esters of vegetable oils on curing, mechanical and dynamic properties of silica filled natural rubber and styrene-butadiene rubber compounds

Characterization of Cambodian natural rubber/common clay composites for shock absorption applications: Primary results

Due to the excellent elastic properties and suitability for diverse applications, natural rubber (NR) has inspired several research studies. Some have showcased remarkable advancements in rubber performances by incorporating inorganic fillers such as clay. Nevertheless, very few studies have explored the origin of natural rubber from Cambodia. This work was conducted to understand the characteristics of the Cambodian natural rubber composites with common clay obtained from a local source. Five different natural rubber (TSR 10) compounds with different clay loadings of 0, 5, 10, 15, 20 parts per hundred rubber (phr) were prepared. The compounds were analyzed for cure characteristics prior to the vulcanization by compression molding at 150 °C. The preliminary tests of raw natural rubber were carried out according to ISO standards. The clay was analyzed for particle size distributions and its mineral compositions analysis using X-ray Fluorescence showed silica content of more than 50%. Overall, the incorporation of clay up to 20 phr showed insignificant effects on the hardness and elongation at break, and also reduced the tensile and tear strength remarkably. However, clay addition at high loading showed a significant improvement on the crosslink density and thermal resistance of the composites.

Evaluation of lignin as stabilizer in vulcanized natural rubber formulations

In this study we evaluated the use of eucalyptus lignin as a stabilizer in combination with other stabilizers in a vulcanized elastomeric based on natural rubber. The stabilizers tested were 6PPD (N-1,3-dimethyl-butyl-N'-phenyl-p-phenylenediamine), TMQ (oligomerized 2,2,4-trimethylquinoline), paraffin wax and eucalyptus lignin. At predetermined time intervals, samples were taken from aging conditions and the mechanical properties and additive content were determined. The sample with a combination of wax and lignin in the same formulation showed the greatest resistance to oxidative degradation. In samples with only one stabilizer, the migration test indicated greater diffusion of lignin to the surface. Samples exposed to thermo-oxidative aging showed greater loss in the mechanical properties of tear strength and 6PPD consumption. In the accelerated aging with ozone, all showed a behavior more resistant to aging. We concluded that lignin can be used as a substitute for synthetic stabilizers, without impairing the performance of natural rubber compounds.

Increasing Efficiency of Mortar Cement Paste Composited with Vulcanized Natural Rubber Compound

Increasing Efficiency of Mortar Cement Paste Composited with Vulcanized Natural Rubber Compound

The use of diisopropyl xanthogen polysulfide as a potential accelerator in efficient sulfur vulcanization of natural rubber compounds

AbstractWith the emerging concerns on the use of nitrosamine evolving accelerators, safer alternatives are desirable for the rubber industry. In the present study, cure characteristics, physicomechanical properties, crosslink density, aging, dynamic mechanical, and thermal properties of vulcanizates prepared with two nitrosamine safe binary accelerator systems containing diisopropyl xanthogen polysulfide (DIXP) and tetrabenzyl thiuram disulfide (TBzTD), and DIXP and dibenzyl dithiocarbamate (ZBeC) were investigated for efficient sulfur vulcanization of natural rubber (NR) compounds. Synergistic effect in both cure and physicomechanical properties was observed for all the combinations of the two accelerator systems. The composition containing DIXP with a lower loading (0.6 phr) of TBzTD, and ZBeC, demonstrated the highest technological performance. Retention of tensile properties on oxidative aging was highest for the vulcanizate prepared with DIXP/TBzTD (1.4/0.6). Dynamic mechanical and thermogravimetric analysis further confirmed the crosslink density and thermal stability of the network structure of the binary systems. In overall, DIXP shows the potential to be used as a safer accelerator in the manufacture of appropriate dry NR‐based rubber products.

Experimental and artificial neural network approach for prediction of the thermal degradation behavior of sugarcane-based vulcanization additives in natural rubber compounds

The use of natural additives in elastomeric compounds is gaining the special attention of researchers and industry due to their potential applications as environmentally friendly compounds and lower cost-related. Another important issue is the use of powerful mathematical tools to predict experimental results, which is crucial for saving cost and time. Artificial neural network (ANN) combined with other mathematical methods, such as surface response methodology (SRM), can guarantee reliability and faster response of the predicted data for similar materials or properties. The great advantage of the present method is the fast prediction of the analyzed property, in the present case, thermal degradation curves, at heating rates not experimentally tested. In this study, a modified activator from sugarcane bagasse was incorporated in different concentrations in natural rubber compounds, and the degradation behavior was simulated by ANN and SRM based on the experimental thermal degradation curves at different heating rates from the thermogravimetric analysis. The simulated results showed an outstanding agreement with the experimental ones, evidencing the importance of using ANN and SRM tools in the prediction of properties of elastomeric compounds.

Effects of Petroleum-Based Oils as Dispersing Aids on Physicochemical Characteristics of Magnetorheological Elastomers.

This paper investigated the effects of petroleum-based oils (PBOs) as a dispersing aid on the physicochemical characteristics of natural rubber (NR)-based magnetorheological elastomers (MREs). The addition of PBOs was expected to overcome the low performance of magnetorheological (MR) elastomers due to their inhomogeneous dispersion and the mobility of magnetic particles within the elastomer matrix. The NR-based MREs were firstly fabricated by mixing the NR compounds homogeneously with different ratios of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO), with weight percentage ratios of 100:0, 70:30, 50:50, and 30:70, respectively. From the obtained results, the ratios of NO mixed with low amounts of AO improved the material physicochemical characteristics, such as thermal properties. Meanwhile, LMO mixed the AO led to the best results for curing characteristics, microstructure observation, and magnetic properties of the MREs. We found that the LMO mixed with a high content of AO could provide good compatibility between the rubber molecular and magnetic particles due to similar chemical structures, which apparently enhance the physicochemical characteristics of MREs. In conclusion, the 30:70 ratio of LMO:AO is considered the preferable dispersing aid for MREs due to structural compounds present in the oil that enhance the physicochemical characteristics of the NR-based MREs.

Kajian uji gelar aspal modifikasi berbasis karet padat jenis crepe rubber pada skala pilot

The COVID-19 pandemic that hit Indonesia had a significant impact on the industrial sector. One of them is the natural rubber industry which has experienced a decline due to export restrictions from natural rubber export destination countries. This has a direct impact on rubber farmers who suffer financial losses. The formation of a new natural rubber downstream industry for natural rubber modified asphalt is a solution to increase national rubber consumption without relying on exports. Therefore, the purpose of carrying out the asphalt title test based on natural rubber type crepe rubber is to evaluate technical feasibility and educate the public about using natural rubber for domestic needs. This service method consists of several stages: observing the absorption potential of natural rubber, analyzing technical feasibility, and evaluating the degree test of natural rubber modified asphalt. The degree test was carried out on the 10-meter road around the Faculty of Engineering, Riau University. The results of the degree test show that the modified asphalt raw material is based on crepe rubber, the asphalt sample marshall test that was held, and the core drill test meets the 2018 Highways standard. The degree test that has been carried out can educate the community and rubber farmers through APKARKUSI regarding natural rubber processing technology and compound making. Crepe rubber and the technology of making modified asphalt and applying modified asphalt for roads.

Microalgal biomass as renewable biofiller in natural rubber compounds

Microalgal biomasses, consisting of micronized Spirulina Platensis and its low protein fraction, were investigated in this work as possible renewable biofillers in natural rubber compounds, with the aim of replacing the commonly used carbon black. Natural rubber, in some cases blended with 10% of epoxidized natural rubber to improve the matrix-filler affinity, was compounded with 25, 35, 50 and 75 phr of each biomass. Compounds with 25, 35 and 50 phr of carbon black N990 were also prepared as benchmarks. After compounding, vulcanization times were determined by dynamic mechanical analysis. Rubbers were vulcanized by compression moulding and characterized by means of morphological analysis (scanning electron microscopy), thermal analysis (thermogravimetric analysis, dynamic mechanical thermal analysis) and mechanical tests (tensile tests, strain induced crystallization detection by X-ray diffraction, pure shear fracture tests). Microalgal biomass turned out to be homogeneously dispersed in natural rubber matrix and the materials obtained required lower curing times compared to carbon black compounds. It was found that, up to 50 phr, Spirulina has the ability to increase rubber tensile strength and modulus, acting similarly to N990, while decreasing rubber thermal stability and fracture toughness.

The Influence of Cork and Manufacturing Parameters on the Properties of Cork–Rubber Composites for Vibration Isolation Applications

The addition of cork to a natural rubber compound and the vulcanization parameters were studied in terms of their influence on the properties of cork–rubber materials. The characterization of different compounds was carried out and included in the determination of mechanical properties related to the application of cork–rubber composites as vibration isolation pads, such as static and dynamic behavior under compressive loading. Statistical methods, such as ANOVA and regression analysis, were used in this study. The results showed that the introduction of cork as an additional filler in the studied rubber compound increased its hardness and static stiffness, while maintaining a similar dynamic behavior to the base rubber compound when subjected to compressive loading. In addition, it was found that increasing the amount and granulometry of cork and lower vulcanization temperatures resulted in stiffer vulcanizates. Materials with higher cork granule contents were found to be affected in their final properties by molding pressure. A study involving the use of linear regression models as a tool to predict or optimize properties related to vibration isolation applications was also developed.

Effect of plasma-polymerised acetylene-coated silica on the compound properties of natural rubber composites

Silica-filled natural rubber (NR) encounters incompatibility problems, owing to the strong particle-particle interaction arising from the hydrogen bonds of hydroxyl groups, which generally leads to the formation of agglomerates. The addition of coupling agents, especially silane coupling agents, reduces the agglomeration. However, this has some disadvantages, such as toxicity, a risk of pre-curing, and the generation of ethanol during mixing. This work aims to focus on the effect of filling the plasma-polymerisation of polyacetylene-coated silica into natural rubber compounds. The deposition of plasma-polymerised acetylene applied to silica particles was firstly carried out using a radio frequency (RF) with an input power of 20 kW for 60 min and further incorporated into NR compounds. On the surface of the coated silica analysis, the formation of a polyacetylene layer on the silica surface was obviously confirmed that it exhibited more stability in water. The following polyacetylene-coated silica (PA-coated silica)-filled NR compound properties were analysed: mixing energy and temperature, Payne effect, complex viscosity, and cure characteristics. The NR compounds mixed with PA-coated silica showed a lower mixing torque, dumping temperature, Payne effect, and viscosity, when compared to NR compounds with unmodified silica and ordinary silane systems. However, the differences were insignificantly noticed in the cure characteristics of the compounds. Polyacetylene-coated silica developed from plasma polymerisation can be used to improve the uniformity of dispersion, as well as the compatibility of silica in a natural-rubber matrix, without changing its cure characteristics, compared to the one with a silane coupling agent.

Elucidation of the accelerated sulfur vulcanization of bio oil‐extended natural rubber compounds

AbstractThe elucidation of the role of bio‐oils on the accelerated sulfur vulcanization of natural rubber (NR) compounds is discussed in this study. Two types of bio‐oil, palm oil and soybean oil, were studied in direct comparison with a distillate aromatic extract oil (DAE) as a reference. The scorch and cure times of the bio‐oil‐extended NR compounds were shorter than those containing DAE. The use of bio‐oils gave a higher cure reaction rate constant along with a lower activation energy than the use of DAE. The attenuated total reflectance‐Fourier transform infrared spectroscopy analysis revealed that the fatty acid segment of the bio‐oils can react with zinc oxide to give zinc carboxylate, which is then involved in and promotes the vulcanization reaction. The use of bio‐oils to increase the rate of vulcanization strongly influenced the crosslink density of the obtained NR vulcanizates, yielding NR vulcanizates with a lower crosslinking density. It is proposed here that the bio‐oils might consume the curing agent via the reaction between their own unsaturated fatty acid and sulfur. This was supported by the increased viscosity of the oils after exposure to sulfur at a high temperature. The tensile strength and elongation at break of the bio‐oil‐extended NR compounds were lower and higher, respectively, than the NR extended with DAE oil due to the lower crosslink density of the bio oil‐extended NR vulcanizates.

Mechanical and rheological properties of partial replacement of carbon black by treated ultrafine calcium carbonate in natural rubber compounds

Mechanical and rheological properties of partial replacement of carbon black by treated ultrafine calcium carbonate in natural rubber compounds

Pengaruh Oleamida Terhadap Karakteristik Pematangan Karet Alam Terisi Silika

The purpose of this study was as a feasibility study of the utilization of oleamide as a new additive for natural rubber (NR) filled with silica using the semi-efficient vulcanization system. Silica fillers used as much as 30 parts per hundred parts rubber (phr). Oleamide was obtained from the synthesis of oleic acid with urea. Oleamide was inserted into the silica filled NR compounds with the varied composition of 0.0 phr; 2.0 phr; 4.0 phr; 6.0 phr, and 8.0 phr. The influence of oleamide on the curing characteristic of the silica filled NR compounds was observed. It was obtained that the oleamide functions as a curative and also a plasticizer. The greater the levels of oleamide added, the shorter the scorch time and optimum curing time were. Oleamide also decreased the minimum torque with addition up to 8.0 phr. The greater the levels of oleamide was, the lower the minimum torque was. Oleamide also increased the maximum torque and torque difference of the silica-filled NR composites at the addition of 2.0 phr. The 2.0 phr was the optimum composition of the oleamide.

Effect of the Epoxide Contents of Liquid Isoprene Rubber as a Processing Aid on the Properties of Silica-Filled Natural Rubber Compounds.

In this study, we examined the feasibility of using epoxidized liquid isoprene rubber (E-LqIR) as a processing aid for truck and bus radial (TBR) tire treads and investigated the effects of the epoxide content on the wear resistance, fuel efficiency, and resistance to extraction of the E-LqIRs. The results confirmed that, compared to the treated distillate aromatic extract (TDAE) oil, the E-LqIRs could enhance the filler–rubber interactions and reduce the oil migration. However, the consumption of sulfur by the E-LqIRs resulted in a lower crosslink density compared to that of the TDAE oil, and the higher epoxide content decreased the wear resistance and fuel efficiency because of the increased glass-transition temperature (Tg). In contrast, the E-LqIR with a low epoxide content of 6 mol% had no significant effect on the Tg of the final compound and resulted in superior wear resistance and fuel efficiency, compared to those shown by TDAE oil, because of the higher filler–rubber interactions.

Preparation and application of modified organo-kaolinite by microwave-assisted irradiation

From the aspect of the modern approach, it is necessary to increase the intercalation efficiency for the objective of widespread market application of kaolinite. The submitted article deals with the microwave-assisted modification of kaolinite (Kaol). Using potassium acetate (KAc) solution and dimethyl sulphoxide (DMSO), Kaol was treated chemically by a microwave radiation at different time intervals at a set constant temperature. Different techniques, such as X-ray diffraction patterns analysis (XRD), Fourier transformed infrared spectroscopy (FT-IR) spectroscopy, thermogravimetry/ differential scanning calorimetry (TG/DSC), and scanning electron microscopy (SEM) were used to characterize Kaol and modified kaolinite samples. The modification was observed after microwave radiation was applied for a short time (30 min). Finally, for the supplementation of the results, the model rubber compounds, filled with Kaol, modified Kaol-KAc and Kaol-DMSO samples in the amount of 10 phr (parts per hundred rubber), were prepared. The effect of modified kaolinite on the curing characteristics and mechanical properties in sulphur-cured natural rubber (NR) compounds was investigated. Partial substitution of carbon black with Kaol-DMSO led to the lower minimum torque and the acceleration of the crosslinking reaction. Moreover, the NR vulcanizates containing Kaol-DMSO showed higher tensile strength and hardness along with high maximum torque that are indicators of the reinforcing effect of the modified kaolinite.

Evaluation of natural and epoxidized vegetable oil in elastomeric compositions for tread rubber

In the tire industry, the incorporation of natural origin oils in the development of elastomeric formulations has been one of the alternatives to reduce the use of petroleum derivatives, with a high content of toxic compounds. In this work, soybean vegetable oil was investigated as a lubricant and co-activator in sulfur-vulcanized natural rubber compounds. The soybean oil was used in its natural state and chemically modified by the epoxy ring’s introduction in its structure. In an internal mixer a standard formulation of natural rubber, five formulations replacing a conventional aromatic oil and stearic acid by vegetable oil, and a formulation without an activation system were prepared. The natural and epoxidized soybean oil was characterized chemically, and the elastomeric compositions were evaluated by mechanical and rheological analysis. The mechanical properties showed satisfactory results when vegetable soybean oil was used as a lubricant and could be a substitute for conventional aromatic oils, thus guaranteeing reduction of aromatic polycyclic content in the formulations. The crosslink degree and the rheological characteristics of the samples prepared with vegetable soybean oil were similar to the natural rubber standard sample. The formulations without the zinc oxide and stearic acid evidenced the need for activators in the vulcanization reaction, as they presented properties below standard. We verified that the epoxidized soybean oil, even when promoting better dispersion of the fillers, interfered in the crosslink formation, and consequently there was a decrease in the mechanical properties of these formulations. Finally, we indicated vegetable soybean oil as a substitute for aromatic oil and stearic acid, in the elastomeric compositions used to manufacture treads.