Natural Rubber Sheet Research Articles

The Benefits of Using Rubber Material in Two Variances: The Rubberized Concrete and the Natural Rubber Sheet, to Strengthen Concrete Barriers for Crash Energy Absorption

The Benefits of Using Rubber Material in Two Variances: The Rubberized Concrete and the Natural Rubber Sheet, to Strengthen Concrete Barriers for Crash Energy Absorption

Mathematical Models of Natural Rubber Sheets Drying: Difference Acid Coagulation Cases

The mathematical model for drying process is a useful tool in process optimization and drying chamber design. The research purposes of this study were to investigate the influence of drying temperature on drying time and the modelling the drying kinetics of the natural rubber (NR) sheets. The NR sheets which produce from commercial formic acid, commercial acetic acids, and ammonia plus commercial formic acid were studied at drying temperature of 40, 50, and 60oC and air speed of 0.5 m/s. The results indicated that the drying time was substantially reduced with an increase in temperature. The moisture content ratio of rubber sheets produce from commercial formic acid coagulation was similar to the sheets produce from commercial acetic acids coagulation. However, the drying time of them were longer than the drying time of the sheets produce from ammonia plus commercial formic acid coagulation. Finally, the logarithmic model was the best model which suitable to predict the moisture content ratio of the sheets drying with all experimental condition.

Innovative design: Flexible conductive natural rubber electrode sheets with triboelectric generator activated by wheel rotation

Efficient consumption and clean energy management play a vital role in green energy. To be a part of this effort. Among the materials explored, flexible conductive electrodes utilizing triboelectric phenomena and unique properties of natural rubber composites have demonstrated a great potential for mechanical-to-electrical energy conversion. Fabrication process involves modifying natural rubber latex by incorporating conductive fillers such as carbon black, Ketjen black, and multiwall carbon nanotubes. The modified flexible conductive natural rubber sheets (CNRs) are then characterized for their structural and electrical properties. This structural arrangement significantly reduces the electrical resistance of the NR sheets. The incorporation of the MWCNT fillers leads to an increase in dielectric constant of CNRs. These properties are optimized via a proper design of the conductive natural rubber sheet triboelectric nanogenerator (CNRS-TENG). To enhance charge accumulation, polytetrafluoroethylene (PTFE) film is applied to the bottom surface of the CNRs. The CNRS-TENG are integrated into a wheel rotation generator setup. The output performance of the wheel rotation generator is influenced by the rotational speed as well as the arrangement of phases and segments. This work demonstrates that CNRs can be integrated with flexible electronic and other energy harvesting devices, opening possibilities for multifunctional clean energy solutions.

Natural rubber composites with high strength, modulus, water-resistance, and thermal stability, prepared with cellulose nanofibrils and sodium methacrylate

Natural rubber (NR) composite sheets consisting of TEMPO-oxidized cellulose nanofibrils (TEMPO–CNFs) and sodium methacrylate (mAANa) were prepared. An aqueous mixture of NR latex, TEMPO–CNFs, and mAANa was oven-dried; the dried material was kneaded to prepare cross-linked composite sheets. The NR/TEMPO–CNF/mAANa (100/20/11.2 by mass) sheets exhibited high tensile strengths of ∼23 MPa, whereas the tensile strengths of the neat NR sheets were ∼5 MPa. Scanning electron microscopy observations indicate that the TEMPO–CNFs formed fewer aggregates in the composite sheet containing mAANa than in the mAANa-free sheets. Thermomechanical tests indicate that the NR/TEMPO–CNF/mAANa sheets had higher storage moduli over the entire range from −100°C to 200°C than the neat NR sheet. The NR/TEMPO–CNF/mAANa composite sheets exhibited hysteresis loss and permanent deformation behaviors, similar to or better than those of NR/carbon black composite sheets. Thus, the NR/TEMPO–CNF/mAANa composite sheets can be used in a similar manner as those consisting of all-carbon neutral components.

Multi-Layered Composites of Natural Rubber (NR) and Bismuth Oxide (Bi2O3) with Enhanced X-ray Shielding and Mechanical Properties.

Due to rapid increases in the utilization of radiation and nuclear technologies, effective and suitable radiation-shielding materials have become one of the most sought-after options to protect users and the public from excessive exposure to the radiation. However, most radiation-shielding materials have greatly reduced mechanical properties after the addition of fillers, resulting in their limited useability and shortened lifetime. Therefore, this work aimed to alleviate such drawbacks/limitations by exploring a possible method to simultaneously enhance both the X-ray shielding and mechanical properties of bismuth oxide (Bi2O3)/natural rubber (NR) composites through multi-layered structures, with varying (1-5) layers and a total combined thickness of 10 mm. To correctly determine the effects of the multi-layered structures on the properties of NR composites, the formulation and layer configuration for all multi-layered samples were tailored such that their theoretical X-ray shielding properties were equal to those of a single-layered sample that contained 200 phr Bi2O3. The results indicated that the multi-layered Bi2O3/NR composites with neat NR sheets on both outer layers (sample-D, sample-F, sample-H, and sample-I) had noticeably higher tensile strength and elongation at break than those of the other designs. Furthermore, all multi-layered samples (sample-B to sample-I), regardless of the layer structure, had enhanced X-ray shielding properties compared to those with a single layer (sample-A), as shown by their higher values of the linear attenuation coefficient (µ) and lead equivalence (Pbeq) and the lower value of the half-value layer (HVL) in the former. This work also determined the effects of thermal aging on relevant properties for all samples, with the results revealing that all the thermal-aged composites had higher values for the tensile modulus but lower values for the swelling percentage, tensile strength, and elongation at break, compared with the non-aged composites. Hence, based on the overall outcomes from this work, it could be concluded that the worrisome decreases in mechanical properties of the common single-layered NR composites after the addition of Bi2O3 could be prevented/reduced by introducing appropriate multi-layered structures, which would not only widen potential applications but also prolong the lifetime of the composites.

Fabrication and properties of natural rubber/rice starch/activated carbon biocomposite-based packing foam sheets and their application to shelf life extension of ‘Hom Thong’ banana

Natural rubber (NR) and rice starch (RS) biocomposite-based packing foam sheets were successfully prepared by the Dunlop method, with activated carbon (AC) as a filler to enhance mechanical properties (and to absorb ethylene gas released by packaged bananas). The primary objective of this study was to examine the influences of activated carbon contents from 0 to 20 phr on physical, morphological, mechanical, and thermal properties of the biocomposite foams. With increasing AC content, the foam cell size, density, hardness, compression force deflection (CFD), compression set, tensile strength, elongation at break, tear strength and glass transition temperature (Tg) increased, while the number density of foam cells and rebound resilience decreased. However, the content of activated carbon did not affect the thermal stability. Furthermore, the developed biocomposite foam with 15 phr AC, which had the highest ethylene removal, was used to evaluate the ethylene absorption capacity and the quality of 'Hom Thong' bananas during 12 days of storage in terms of weight loss, pulp firmness, total soluble solids (TSS), physical appearance, and peel color, with comparison to a commercial foam and control. The biocomposite foam with 15 phr AC lowered the ambient ethylene levels considerably, hence delaying fruit ripening and decreasing chlorophyll degradation, TSS, and pulp firmness at 6 days of ambient storage. The proposed biocomposite foam shows potential for enhancing the postharvest storage stability of bananas and has great potential as packaging for other fresh fruit products.

Deterioration of Vulcanized Natural Rubber Sheets is Associated with Removal of Calcium Carbonate Filler by Wood-Decay Fungi Trichaptum Abietinum and Trichaptum Biforme

Deterioration of Vulcanized Natural Rubber Sheets is Associated with Removal of Calcium Carbonate Filler by Wood-Decay Fungi Trichaptum Abietinum and Trichaptum Biforme

Study of Aquilaria crassna Wood as an Antifungal Additive to Improve the Properties of Natural Rubber as Air-Dried Sheets.

Fungal growth on rubber sheets confers inferior properties and an unpleasant odor to raw natural rubber (NR) and products made from it, and it causes environmental concerns. The purpose of the present work was to investigate the effects of Aquilaria crassna wood (ACW) on the antifungal, physical and mechanical properties of NR as air-dried sheets (ADS) and ADS filled with ACW. The results show that the ACW-filled ADS had an increased Mooney viscosity, initial plasticity (PO), and high thermo-oxidation plasticity (i.e., high plasticity retention index PRI). Additionally, superior green strength was observed for the ACW-filled ADS over the ADS without additive because of chemical interactions between lignin and proteins in NR molecules eliciting greater gel formation. A significant inhibition of fungal growth on the NR products during storage over a long period (5 months) was observed for ACW-filled ADS. Thus, it can be concluded that ACW could be applied as an antifungal additive that reduces fungal growth. This is a practically important aspect for the rubber industry, as fungal growth tends to spoil and cause the loss of NR sheets during storage. Moreover, the ACW is active as an incense agent, reducing negative impacts from odors that fungi, on rubber surfaces, release. Therefore, these filled intermediate NR products provide added value through, an environmentally friendly approach, this is pleasant to customers.

Effect of Wood Vinegar Substitutes on Acetic Acid for Coagulating Natural Para Rubber Sheets during the Drying Process

The coagulating properties of wood vinegar from para rubber wood, bamboo, and coconut shell used as a substitute for acetic acid in the production process of natural rubber (NR) sheets were investigated and considered. For the dirt and volatile content, the tensile strength at break, the percentage of elongation at break, and the 300% modulus, the results showed that the types of wood vinegar coagulants were not significantly different from acetic acid. However, the Mooney viscosity and plasticity retention index (PRI) properties were significantly different from those of acetic acid. The NR sheet temperature increased rapidly during the first hour after the drying process started due to heat transfer from the hot air. Afterward, the temperature of the NR sheet samples began to stabilize. When the drying process started, the drying temperature was increased, so the trend was reducing the drying time. For the yellowness index (YI) value, the increase in the YI value was related to the type of coagulating material, the increase in the airspeed, and the drying temperature. The dried sheet samples using para rubber wood vinegar as the coagulating material had a color value at the same level as acetic acid and the referent. However, the bamboo and coconut shell wood vinegars were at a lower level. In comparing the YI value data between the experimental results and prediction values, the second-degree model had a better fit in prediction than the zero-degree and first-degree models. This result was confirmed by the higher mean of the coefficient of determination. The dried sheet product coagulated by using wood vinegar had fungus growth prior to supplying it to the customer.

Comparative study on ballistic impact response of neat fabric, compliant, hybrid compliant and stiff composite

The present study deals with the experimental approach of finding the ballistic limit of neat jute fabric along with its compliant composite, compliant hybrid composite with and without interleaved natural rubber (NR) sheets and stiff jute epoxy (JE) composite. Mechanism governing the damage in the proposed targets are studied. Ballistic impact tests were carried out by firing a conical projectile using a gas gun apparatus at lower range of ballistic impact regime. The ballistic impact response of the neat jute fabrics along with proposed compliant composites are assessed based on energy absorption and damage mechanism. Results revealed that the complaint hybrid composites exhibit enhanced ballistic response compared to neat jute fabrics, compliant and stiff composites. Inclusion of NR aids affects the ballistic performance of the composite significantly by keeping the composite flexibility. Rubber does not restrict the yarns through which the whole fabric resists against projectile energy. This behavior is contrary to the epoxy matrix, in which only a few yarns in impact zone resist. This difference significantly changes the ballistic performance of stiff composite and compliant hybrid composite. The damage study reveals the various mechanisms responsible for failure in neat fabrics, compliant composites, compliant hybrid composites and stiff composites. Compliant hybrid composites fail due to matrix tearing as opposed to matrix cracking in stiff JE composites indicating that the proposed complaint composites are free from catastrophic failure. Thus, the proposed compliant hybrid composites are best suited for ballistic applications.

Three body abrasive wear assessment of novel jute/natural rubber flexible green composite

Determining the resistance to abrasion of the flexible cladding for armours and automobile structural components with the aid of lab scale tests has become increasingly important. In the present study, three body wear behaviour of flexible green composites comprising of jute in woven fabric form with interleaved natural rubber sheets bonded through rubberized B stage cured Pre pegs have been studied. Flexible composites are fabricated in three different configurations having different layers of jute and rubber. The present study makes use of silica sand as the abrasive medium. The specific wear rate along with loss in mass and volume of the composite due to wear is determined and it was found that specific wear rate is dependant of the sliding distance. Comparing the specific wear rate of all the three stacking sequences, it was found that JRJ stacking sequence provides better wear resistance. Compliant and tough nature of the rubber makes it hard to wear it out through tearing action and also the wear resistance of flexible composites is enhanced with inclusion of rubber. Mechanism of wear in each of the constituent used is studied. The present study serves as a benchmark work for the future research in this area.

Optimization of a protein extraction method from natural rubber sheets made of Hevea brasiliensis latex

A method to extract proteins from natural rubber (NR) samples has been developed to characterize the protein composition of NR by SDS-PAGE electrophoresis. While the incubation of NR pieces in aqueous buffers did not provide satisfactory results (no protein bands detected by SDS-PAGE), the solubilization of NR pieces in an organic solvent, prior to centrifugation and protein extraction from the obtained pellet, was found efficient to highlight protein bands by SDS-PAGE. Pure cyclohexane was used to solubilize NR pieces and resulted in a low share of nitrogen in the pellet (29%). The addition of 10% (v/v) ethanol to cyclohexane allowed to significantly increase this share to 73% and to detect 13 protein bands by SDS-PAGE. The molecular weights of the four most intense bands suggest the presence in NR of the following proteins: rubber elongation factor, small rubber particle protein, hevamine, and β-1-3 glucanase.

Parametric study on impact behaviour of sisal and cenosphere reinforced natural rubber-based hybrid composites: FE approach

This paper aims to study the impact analysis of sisal fiber and cenosphere filler reinforced natural rubber composite using commercially available finite element software. The proposed green composite is studied for impact behaviour by varying the weight percentage of the cenosphere filler particles in a natural rubber sheet. Composite is modelled with stacking sequence sisal-rubber-sisal using finite element software and impacted by three different rigid impactors (Conical, Hemi-spherical and Flat) at the velocity of 8 m/s. Modelling and simulation of this proposed composite laminate are solved using the explicit dynamic solver of Abaqus Computer-Aided Engineering Finite Element Modelling. The results of the low-velocity impact of the proposed green composite with sisal-rubber-sisal stacking sequence exhibit better energy absorption by varying the weight percentage of the Cenosphere. Also, the energy absorbed by laminate was more for the Conical impactor than the Hemi-spherical and Flat impactors and the extent of damage is more when impacted by the Flat impactor due to its larger contact area.

Drying kinetics of natural rubber sheets under two solar thermal drying systems

This work describes the thermal behavior and evaluation of kinetics drying of natural rubber sheets using two solar drying technologies: direct and indirect. The solar drying tests were carried out simultaneously in order to compare the behavior under same weather conditions. The moisture content of the rubber sheets was reduced from 45.8 to 0.59% and from 49.7 to 0.33% on a dry basis (d.b.) for direct solar drying and indirect solar drying, respectively. The direct drying mode was carried out for 12 days with average temperature and relative humidity inside the greenhouse, during sunny hours, of 37.04 °C and 14.1%, respectively. Meanwhile, the indirect drying operation was carried out in 9 days (61.62 h intermittently) with 61 °C and 4.77%, respectively. The average global energy efficiency of the field of SAH was 33.77%. Thirteen thin layer models were used to evaluate the drying behavior of which the Modified Henderson and Pabis model was the best to describe the solar drying of rubber sheets for the direct and indirect system. As a conclusion, the direct greenhouse-type solar dryer is recommended for small producers and the indirect tunnel-type solar dryer for companies with high and continuous production.

Development and performance analysis of a mixed mode solar thermal dryer for drying of natural rubber sheets in the north-eastern part of India

In the north-eastern geographical setting of India, lies Tripura, the second largest state of India in terms of natural rubber cultivation. Often, the unpredictable weather and lack of appropriate drying methodology deteriorates the quality of the dried natural rubber fetching less income to the unorganized small scale farmers. Installation of modular solar thermal dryers in this region can resolve this problem. In this study, a 6 kg/batch mixed-mode solar thermal dryer was developed and installed at Agartala for performance investigation. Moisture content of the natural rubber sheets dried in the solar thermal dryer was reduced from 40% to 4% vis-à-vis 11% in open sun drying condition in 3 days’ time on wet basis. Six drying models were studied and validated against the experimental data. The average energy and exergy efficiencies of the system for natural rubber sheet drying were 9.09% and 2.48% respectively. Quality of the solar dryer dried sheets were found to be superior to the open sun dried ones. Techno-economic analysis showed a payback period of 2.2 y. Innovative features of the developed solar thermal dryer include (a) recirculation of spent dehumidified air to minimize thermal energy loss (b) 90% UV cutoff in the drying chamber leading to better colour retention of the product (c) solar photovoltaic operated dehumidifier for use during night to prevent reabsorption of moisture. The higher throughput, better quality and ease of operation can make this mode of natural rubber sheet drying an attractive option among akin communities.

An experimental study on adhesion, flexibility, interlaminar shear strength, and damage mechanism of jute/rubber-based flexible “green” composite

Determining the interlaminar shear strength (ILSS) of the composite laminates is vital for deciding their usage in any engineering applications. The matrix used and its curing characteristics are vital in deciding the ILSS of the composite. Present work deals with an experimental study on adhesive behavior, degree of flexibility, ILSS, and damage mechanism of the novel jute/rubber-based flexible “green” composite. The proposed flexible composites were prepared in three different stacking sequences, namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ), and jute/rubber/jute/rubber/jute (JRJRJ), using compression molding technique. After determining the optimal curing characteristics of the proposed rubber-based matrix, the constituents are tested for their adhesive strength with the matrix which showed that rubber matrix system is compatible with jute fabric and natural rubber sheet. Composites are prepared and degree of flexibility for each stacking sequence is found out. Results pertaining to ILSS show that JRJRJ has better ILSS compared to JRJ and JRRJ. Fractographic analysis using scanning electron microscope reveals the mode of failure of the composites and the mechanism governing their failure. Fourier transform infrared spectroscopic study reveals the bonding between the constituents is good enough to be used in composites with flexibility.

Base isolation fibre-reinforced composite bearings using recycled rubber

In the past few years, there have been a number of previous researches on the rubber isolators for resisting earthquakes. A typical bearing consists of natural rubber sheets and bonded to steel plates. For an application of using rubber bearings, numerous isolated buildings have been constructed to resist an earthquake across the countries which experience earthquakes over decades. Another application might be used in the bridge structures of railways and highways, in order to suppress vibrations and dynamic actions. The key idea is to use rubber isolators attached beneath the superstructures for attenuating the damage potential of seismic responses. This means that the rubber provides the isolators flexible in the horizontal direction and the steel makes them strong in the vertical direction. Anyways, most bearings are made of natural rubber or synthetic compound. These materials are costly and cannot be durable over time. This paper aims to develop a new design of bearing using recycled materials and fibre reinforcement. The concept is to design two models using the finite element method (FEM) as a square and circular shape for the investigation into the static and dynamic behaviour. Through, the finite element method will be conducted to evaluate structural response and effectiveness of the novel low-cost bearing. Bearing models from the analytical method based on the theory are verified by the FEM. The overall results show that the fibre square model is less effective than the fibre circular model due to the different shape factors, S. The outcome of this project will help to enable more eco-friendly bearing materials for structural, highway and railway engineers. However, a further study of designing recycled rubber bearings with the fibre-reinforced polymer should be carried out by experimental tests. The study should be also compared with the performance between the fibre and steel bearing model, in order to verify the models created by FEA more effectively.

Selection of stabilizer and coagulant for natural rubber latex colloidal system during diimide catalytic hydrogenation at semi pilot scale reaction

Hydrogénation of natural rubber latex improves its thermal properties such as thermal oxidative resistance. Hydrogenation converts unsaturated C double bond into saturated C single bond on natural rubber molecular chains without being followed by chain scissioning. The hydrogenated natural rubber is considered can substitute synthetic rubber such as chloroprene rubber, EPDM, and butyl rubber in the manufacture of outdoor rubber based product. The optimized hydrogenation require natural rubber latex colloidal system remains in the liquid phase during the reaction, however it should be easily coagulated at the end of hydrogenation to reach high yield of reaction. The aim of the research was to study the effect of latex colloidal stabilizer system and coagulant to the natural rubber hydrogenation efficiency. Insitu catalytic hydrogenation of natural rubber latex by diimide compound was run at semi pilot scale at capacity 2.5 kg latex concentrated/batch. The diimide was generated from oxidation of hydrazine hydrate with hydrogen peroxide. The hydrogenation used strong base and surfactant stabilizer type. While, organic acid and inorganic salt were selected as coagulant. The best of stabilizer and coagulant were determined based on qualitative analysis such as FTIR spectra, stability of natural rubber latex colloidal system during the reaction and visual characteristic of hydrogenated natural rubber. The result showed that anionic surfactant could ensure the colloidal natural rubber latex remains in liquid phase during hydrogenation which was indicated by the absence of latex coagulation and decrease possibility of side reaction. Further, organic acid was selected as the best coagulant for hydrogenated natural rubber latex. It was characterized by clear-coloured serum, and hard-non sticky hydrogenated natural rubber sheet.

Influence of shrinkage during natural rubber sheet drying: Numerical modeling of heat and mass transfer

We developed a theoretical model for the transport phenomena affected by shrinkage in rubber sheet drying. The conjugate approach involving the simultaneous transfer of momentum, heat and mass in the drying chamber and rubber sheet was investigated by computational fluid dynamics. An isotropic, linear elastic model was assumed, and the shrinkage was correlated with the moisture content evolution in the rubber sheet. The Arbitrary Lagrangian-Eulerian (ALE) method was used to solve the two-dimensional problem accounting for shrinkage. The shrinkage across the rubber sheet thickness was estimated at 9.1% and the moisture content was reduced from 0.4 to 0.05 kg-water/kg-dried sheet at an average holding relative humidity of 60% within 46 h. Simulations and experiments showed good agreement (R2 values for moisture content and shrinkage were 0.9809 and 0.9991, while RMSE were 0.0196 and 0.0091). The derived model can be used as a quality index evaluation for rubber sheet and for drying process optimization. Water activity can also identify regions that may be prone to microbial spoilage. The drying time was lower than for traditional sun drying of air dried sheets (as high as 152 h) or drying in a natural flow chamber (72 h).

Albemarle Corporation, Sinopec Catalyst Company and Sinopec Fushun Research Institute of Petroleum and Petrochemicals sign heads of agreement in field of hydrocracking

In the north-eastern geographical setting of India, lies Tripura, the second largest state of India in terms of natural rubber cultivation. Often, the unpredictable weather and lack of appropriate drying methodology deteriorates the quality of the dried natural rubber fetching less income to the unorganized small scale farmers. Installation of modular solar thermal dryers in this region can resolve this problem. In this study, a 6 kg/batch mixed-mode solar thermal dryer was developed and installed at Agartala for performance investigation. Moisture content of the natural rubber sheets dried in the solar thermal dryer was reduced from 40% to 4% vis-à-vis 11% in open sun drying condition in 3 days’ time on wet basis. Six drying models were studied and validated against the experimental data. The average energy and exergy efficiencies of the system for natural rubber sheet drying were 9.09% and 2.48% respectively. Quality of the solar dryer dried sheets were found to be superior to the open sun dried ones. Techno-economic analysis showed a payback period of 2.2 y. Innovative features of the developed solar thermal dryer include (a) recirculation of spent dehumidified air to minimize thermal energy loss (b) 90% UV cutoff in the drying chamber leading to better colour retention of the product (c) solar photovoltaic operated dehumidifier for use during night to prevent reabsorption of moisture. The higher throughput, better quality and ease of operation can make this mode of natural rubber sheet drying an attractive option among akin communities.