Properties Of Natural Rubber Research Articles

Comparative analysis of latex transcriptomes reveals the potential\xa0mechanisms\xa0underlying\xa0rubber molecular weight variations\xa0between the Hevea brasiliensis clones RRIM600 and Reyan7-33\u201397

BackgroundThe processabilities and mechanical properties of natural rubber depend greatly on its molecular weight (MW) and molecular weight distribution (MWD). However, the mechanisms underlying the regulation of molecular weight during rubber biosynthesis remain unclear.ResultsIn the present study, we determined the MW and particle size of latex from 1-year-old virgin trees and 30-year-old regularly tapped trees of the Hevea clones Reyan7-33–97 and RRIM600. The results showed that both the MW and the particle size of latex varied between these two clones and increased with tree age. Latex from RRIM600 trees had a smaller average particle size than that from Reyan7-33–97 trees of the same age. In 1-year-old trees, the Reyan7-33–97 latex displayed a slightly higher MW than that of RRIM600, whereas in 30-year-old trees, the RRIM600 latex had a significantly higher MW than the Reyan7-33–97 latex. Comparative analysis of the transcriptome profiles indicated that the average rubber particle size is negatively correlated with the expression levels of rubber particle associated proteins, and that the high-MW traits of latex are closely correlated with the enhanced expression of isopentenyl pyrophosphate (IPP) monomer-generating pathway genes and downstream allylic diphosphate (APP) initiator-consuming non-rubber pathways. By bioinformatics analysis, we further identified a group of transcription factors that potentially regulate the biosynthesis of IPP.ConclusionsAltogether, our results revealed the potential regulatory mechanisms involving gene expression variations in IPP-generating pathways and the non-rubber isoprenoid pathways, which affect the ratios and contents of IPP and APP initiators, resulting in significant rubber MW variations among same-aged trees of the Hevea clones Reyan7-33–97 and RRIM600. Our findings provide a better understanding of rubber biosynthesis and lay the foundation for genetic improvement of rubber quality in H. brasiliensis.

Viscoelastic properties of natural rubber with fatigue damage

The interplay of fatigue damage and inelasticity of elastomers is an open problem. A viscoelasticity-based constitutive equation's parameters were used to trace the evolution of elastomer inelasticity with fatigue damage. Contrary to the Continuum-damage-mechanics based hypothesis, the decay of stiffness of the equilibrium network was non-monotonic with fatigue life. The variation of the inelastic network parameters suggests interplay between damage and inelasticity. However, a trend suggestive of the effect of damage on viscoelasticity was not found. High-temperature fatigue demonstrated no permanent effect on stress–strain response. The results indicate that the degradation of stiffness is not an indicator of fatigue-induced damage.

Influence of l-quebrachitol on the properties of centrifuged natural rubber

Abstract Nonrubber components (NRCs) play an important role in the outstanding mechanical property of natural rubber (NR). The main inositol component of NRCs in natural rubber latex (NRL) is l-quebrachitol. In this study, the influence of l-quebrachitol on the properties of centrifuged natural rubber (CNR) was investigated. The NRL was centrifuged twice to remove most of the NRCs. After that, l-quebrachitol was added in the latex with per hundreds of rubber (phr) vary from 0% to 0.8%, and the vulcanized CNR were prepared. It is shown that the properties of vulcanized CNR were greatly changed, with T 90 reduced from 19 to 15 min, the tensile strength increased from 5 to 9 MPa, T g reduced by about 2°C, and the ability for strain-induced crystallization was enhanced. It was proved by FTIR results that l-quebrachitol was linked to the CNR crosslinking network with ester bond.

Enhancement of electromechanical properties of natural rubber by adding barium titanate filler: An electro‐mechanical study

AbstractNatural rubber is one of the most potential electro‐active polymers for sensors, actuators, and energy harvesting applications. Enhancing the characteristic properties of polymers by reinforcing with fillers that possess multifunctional attributes have attracted considerable attention. In the present study, barium titanate reinforced natural rubber composite is prepared by using two‐roll mill mixing. Afterwards, mechanical, electrical, and electromechanical properties of the composites are extensively analyzed by reinforcing different amounts of barium titanate into the matrix of natural rubber. The fabricated dielectric composite shows excellent properties such as high dielectric constant, low dielectric losses, high dielectric breakdown strength, and extreme stretchability. It is observed that as the filler loading reaches the value of 11 parts per hundred rubber (phr), maximum agglomeration of the particles occurs. Maximum stretchability and highest ratio of dielectric constant to elastic modulus are obtained at 8 phr of barium titanate fillers and at the loading, a maximum actuation strain of 11.24% is achieved. This study provides a simple, economical, and effective method for preparing enhanced mechanical, electrical, and electromechanical properties of natural rubber composites, facilitating the wide applications of dielectric materials as actuators and generators.

Effects of carbon nanotubes and graphene on the structure and properties of natural rubber

Natural rubber (NR) is an important strategic material for national defense industry. It is also used in the food industry and medicine. However, due to the unsaturated double bond, its aging resistance, mechanical properties and solvent resistance are very poor. In order to improve these properties, carbon nanotubes (CNTs) and reduced graphene oxide (rGO) were used, added at 1 : 1 ratio. TheNR/CNTs/rGO nanocomposites were obtained by mechanical mixing after adding 1, 2, 3 and 4 phr offiller. The influence of the filler content on the structure (TEM), vulcanization properties, abrasion and solvent resistance, mechanical properties, dynamic mechanical properties (DMA) and thermal properties (TGA) of nanocomposites was investigated. Increasing the content of CNTs/rGO increased the crosslinking density of the composites. TEM studies showed that CNTs and graphene sheets were evenly dispersed throughout the NR matrix. They also had good compatibility with the rubber matrix. The addition of CNTs and graphene increased the abrasion and solvent resistance as well as improved the mechanical properties. TGA analysis showed that the nanocomposites had excellent thermal stability. The best properties were obtained with the CNTs/rGO content of 2 phr.

Structure and Temperature Induced Crystallization of Natural Rubber with Different Milling Times

Crystallization, a characteristic property of natural rubber, has great effect on the storage and application in industrial. Based on different milling times, natural rubber samples were prepared. Moreover, structure of natural rubber with different milling times, i.e. molecular weight, group transform, cross-link density (entanglement), and rheology were analyzed by gel permeation chromatograph (GPC), Fourier transform infrared spectrum (FTIR), and rubber processing analyzer (RPA), respectively. Furthermore, temperature induced crystallization parameters were mounted on differential scanning calorimeter (DSC). The results demonstrated that temperature induced crystallization rate decreased with the increment of milling times, whereas the average molecular weight measured by GPC decreased with milling times increasing. However, the average cross-link molecular weight increased which was compatible to the temperature induced crystallization rate. It was concluded that temperature induced crystallization rate was related to the average cross-link molecular weight, but not average molecular weight.

Incorporation and optimization of RGO and GO in SSBR/NR composites expands their applicability

Natural rubber (NR) has poor mechanical properties, which limits its practical application. Filler blending is a simple method that improves the inherent properties of natural rubber and expand its applicability. Using the mechanical mixing process, the effects of graphene oxide (GO) and redox graphene (rGO) on the physical properties, electrical conductivity, thermal conductivity, and air permeability of styrene-butadiene rubber (SSBR)/NR composites were studied. The results show that rGO exhibits efficient filler properties in various aspects, for example, the optimal filling amount of rGO and GO was 1.5 phr. In addition, rGO filled SSBR/NR composites showed satisfactory filler dispersibility. Notably, the better dispersibility of rGO was because of fewer hydrophilic functional groups on the surface which were difficult to agglomerate. The increase of rGO and GO content increased the maximum torque (MH) and minimum torque (ML) of the composite material, and decreases tc90 and tc10. The Payne effect of GO/SSBR/NR composites is more obvious than that of rGO/SSBR/NR composites. In addition, we found that the content of rGO (GO) reached saturation at 2phr. Notably, rGO and GO improved the properties of rGO filled SSBR/NR composites such as the tensile strength of rGO/SSBR/NR composites to 23.9 MPa. This shows the potential application of SSBR/NR composites in wearable electronic devices.

Improvement of Mechanical and Flame Retardant Properties of Natural Rubber by Eco-friendly Watermelon Peel and Crumb Rubber

This work aimed to investigate the suitability of using watermelon peels powder (WPP) and crumb rubber (CR) as alternatives to fillers flame retardant chemicals to reduce cost. The new composites of natural rubber (NR) and watermelon peels powder (0, 5, 10 phr) were produced by mixing them in the presence of crumb rubber powder loaded (0, 5, 10 phr). The structure of the composites was characterized by X-ray diffraction (XRD). Both scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to investigate the morphology of the NR composites. The mechanical properties, such as tensile strength (TS) and elongation (E%) were measured. The contact angles of deionized water (DIW) and glycerol (GL) drops on the NR composite surface were measured. The combustion analysis of the NR composites was tested using differential thermal analysis (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI), and flame chamber (UL-94) according to standards. The results indicated the effect of the WPP in mechanical properties and combustion analysis for the NR composites when blended with different weight % of CR.

Influence of Carbon Black on Aging Properties of Natural Rubber

The influence of carbon black on the aging properties of NR was studied by adding different grades and contents of carbon black. The results show that the hardness, tensile strength and tear strength of NR increased with the increase of carbon black level and content, while the elongation at break and Akron abrasion decreased. After hot air accelerated aging and ultraviolet aging, the tensile strength, elongation at break and Akron abrasion of NR decreased, the tear strength first decreased and then increased, and the shore hardness gradually increased. With the increase of carbon black grade and quantity, the change rate of natural rubber aging properties, such as shore hardness, tensile strength, elongation at break, tear strength and Akron abrasion, became smaller and smaller.

Production of Bacterial Cellulose from Food Industrial Waste and its Application on Natural Rubber

Bacterial cellulose (BC) is high purity and several current potential uses in industries. Liquid byproduct of sweet corn canning process (SC) contains fermentable sugars which could be utilized to get higher economic benefits. Therefore, this research aimed to produce BC from SC by Gluconacetobacter xylinus under static condition and use it to improve mechanical properties of natural rubber. The ratio of SC to coconut juice for cellulose production was studied. The result revealed that production yield, water holding capacity and tensile strength of BC produced from the medium containing coconut juice to SC at a ratio of 75:25 (w/w) supplemented with 1% acetic acid, 1% ammonium sulfate and 5% sucrose (w/w) was not significant different from BC obtained from a coconut juice medium. The FTIR spectra of BC showed the characteristics of cellulose. The morphology of BC exhibited high fibril network. BC is showed reinforcement in natural rubber composites due to enhance the stress value, whereas reduce the strain value.

Effect of Pre-Blending and Phase-Mixing Methods on Properties of Natural Rubber and Acrylonitrile Butadiene Rubber Blends Filled with Nano Silica Extracted from Rice Husk Ash

Properties of natural rubber (NR) and acrylonitrile butadiene rubber (NBR) blends are varied due to blending method. The literature is evident that the pre-blending and phase-mixing methods affect the properties of blends while opposite arguments are also available. Hence, that fact was interested to study using NR/NBR blends filled with rice husk ash nano silica (RHANS) having an average particle size of 50 nm - 100 nm with some micro-scale agglomerates. The structure of RHANS was proved using X-ray diffraction and Fourier transform infrared spectrophotometric analyses. Blends were prepared following both blending methods by varying NR to NBR ratio as 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 while filling 25 parts per hundred parts of rubber of RHANS. The control was the ASTM formulation for oil seals. Vulcanization properties of blends showed acceptable levels with extended scorch and cure times and high torque properties. Blends indicated less tensile and tear strength compared to the control while showing acceptable hardness, compression set, and swelling properties. Overall, there is a possibility to use RHANS in NR/NBR blends and it was found that the blending method does not affect the properties of the NR/NBR blends.

Expandable graphite microencapsulated with polyurea shell flame retardant natural rubber

The expandable graphite (EG) was microencapsulated by polyurea, and CuO was doped into the shell of the expandable graphite microcapsule (EG@PO) in order to improve the thermal conductivity of the shell. The microcapsules were characterized by SEM, thermogravimetric analysis and Fourier transform infrared spectroscopy. The effect of EG@PO and ammonium polyphosphate (APP) on the flame retardant properties of natural rubber (NR) was also investigated by limited oxygen index test, vertical burning test, thermogravimetric analysis, cone calorimeter test and thermal conductivity measurement. The results show that when mass of EG@PO is 6 g, the limited oxygen index of EG@PO/NR composite is 28.3%, and the vertical burning of composite reaches to V-0. The residual mass is 27.5% at 600℃. Furthermore, the heat release rate and total heat release of EG@PO/NR composites decrease dramatically to 467.7 kW/m2 and 48.4 MJ/m2, respectively, which is 49.8% and 25.7% lower than that of the pure NR. At the same time, the thermal conductivity of EG@PO/NR composites increases to 0.266 W/(m·K), because the CuO doped into the shell is beneficial to the heat transfer between the NR matrix and EG.

Comparative Studies on Solubility and Thermo Dynamics Properties of Natural Rubber Filled with CB/CPKS and CB/APKS Fillers

In this research, the comparative studies on solubility and thermodynamics properties of natural rubber vulcanizates filled with blends of activated palm kernel shell and carbonized palm kernel shell has been investigated. Palm Kernel Shell (PKS) was locally sourced. washed and sun dried to remove accompanying and moisture. The PKS was then pulverized to particle size, carbonized at 600°C for one hour (1hr) using Carbolite furnaces and chemically activated using 0.1M H₃PO₄ and 0.1M KOH solutions. The NR-filler loading concentrations of CB/APKS and CB/CPKS were compounded using two-roll mill. The solubility was done using three different solvents of water, kerosene and petrol respectively. The solubility results obtained for CB/APKS and CB/CPKS has no significance difference as the temperature varies when immersed in water. The solubility values observed for CB/APKS and CB/CPKS ranges from 1.06g to 1.19g and 1.03g to 1.19g across the samples respectively. This shows that since the filler is an organic substance, it has little or no affinity for water. In the case of kerosene and petrol, both are organics and the filler is an organic substance which follows the statement ‘like-dissolves-like’ as the temperature increases, the absorption of kerosene is lower than that of petrol. The results recorded for kerosene across the samples of CB/APKS and CB/CPKS ranges from 1.18g to 4.37g and 2.02g to 4.79g while the results for petrol ranges from 2.25g to 4.92g and 2.51g to 4.88g respectively. This may be due to the fact that petrol is volatile and flammable compared to kerosene. The results of the activation energy were a reflection of the solvent’s permeability except for water which showed contrary results. The results of the activation energy obtained for the three solvents across CB/APKS and CB/CPKS were 5.55 KJ/mol for water, kerosene with 9.48 KJ/mol and petrol with 13.61 KJ/mol respectively. The results observed for water might be due to its nature as the universal solvent being entirely different from other solvents in terms of reactivity and anomalous property. This means polar solvents dissolve polar molecules while nonpolar solvents dissolve nonpolar molecules. This research shows that both CB/APKS and CB/CPKS possess great potential in rubber system.

Optimization of mechanical properties of CNT-rubber nanocomposites

Rubber nanocomposites were prepared by adding required amount of Multiwall carbon nanotubes (MWCNT) in varying proportions (0.5, 1, 1.5, 2 and 2.5 wt%) as nano reinforcement and carbon black in varying proportion (0, 10, 20, 30 and 40 phr) as filler. The chemicals were added in the following order (Natural Rubber, Antioxidant: 1 phr, Oil: 5 phr, Zinc Oxide: 4 phr, Stearic Acid: 2 phr, Accelerator: 1 phr, Sulfur: 2phr) in double roll mill to process rubber nanocomposites. The result revealed that the incorporation of Multiwall carbon nanotube (MWCNT) has significantly improved the mechanical properties of natural rubber. In this work an attempt has been used to find rubber nanocomposite system which posses best combined mechanical by TOPSIS Method.

Effects of protein contents in different natural rubber latex forms on the properties of natural rubber vulcanized with glutaraldehyde

Effects of protein contents in different natural rubber latex forms on the properties of natural rubber vulcanized with glutaraldehyde

Influence of plantation climate and storage time on thermal and viscoelastic properties of natural rubber

The Sociedad de Caucho Colombo Argentina (SOCCA) collected natural rubber (NR) from Yarima, Colombia, for seven months spanning two years. The unvulcanized NR was used to conduct a preliminary study, part of a long-term study, to uncover some underlying mechanisms in charge of imparting variation between NR batches, such as the collection site's rainfall conditions and storage period by using calorimetry, rheometry, and a dynamic mechanical analyzer. The ultrasound study found that an increase in monthly rainfall increased the material's elastic constant at 10 MHz, and the crystallization study uncovered that the amount of crystallization decreased with increased rain while remaining relatively constant if rainfall was within the recommended rainfall amount for the tree. Additionally, stress relaxation measurements revealed that an increase in rainfall suggested an increase in the material's temperature sensitivity. The temperature sensitivity relates to the material's processability in which an increase in temperature with high sensitivity will have a more drastic decrease in stress during a relaxation test compared to a material with low sensitivity.

Enhanced Fatigue and Durability Properties of Natural Rubber Composites Reinforced with Carbon Nanotubes and Graphene Oxide.

Fibrous carbon nanotubes (CNTs) and lamellar graphene oxide (GO) exhibit significant advantages for improving the fatigue properties of rubber composites. In this work, the synergistic effect of CNTs and GO on the modification of the microstructure and fatigue properties of natural rubber (NR) was comprehensively investigated. Results showed that CNTs and GO were interspersed, and they formed a strong filler network in the NR matrix. Compared with those of CNT/NR and GO/NR composites, the CNT-GO/NR composites showed the smallest crack precursor sizes, the lowest crack growth rates, more branching and deflections, and the longest fatigue life.

The Impact of Nano CaCO3 Modified in situ with Methacrylic Acid on the Structure and Properties of Natural Rubber

The Impact of Nano CaCO3 Modified in situ with Methacrylic Acid on the Structure and Properties of Natural Rubber

Proper Blends of Biodegradable Polycaprolactone and Natural Rubber for 3D Printing.

Flexible thermoplastic elastomers (TPE) were prepared for fused deposition modeling (FDM) or 3D printing. These materials can be used for medical purposes such as disposable soft splints and other flexible devices. Blends of 50% epoxidized natural rubber (ENR-50) and block rubber (Standard Thai Rubber 5L (STR5L)) with polycaprolactone (PCL) were produced and compared. The purpose of this study was to investigate the properties of natural rubber (NR) and PCL in simple blends with PCL contents of 40%, 50%, and 60% by weight (except at 75% for morphology study) in the base mixture (NR/PCL). The significant flow factors for FDM materials, such as melting temperature (Tm) and melt flow rate (MFR), were observed by differential scanning calorimetry (DSC) and via the melt flow index (MFI). In addition, the following mechanical properties were also determined: tensile strength, compression set, and hardness. The results from DSC showed that the melting temperature changed slightly (1–2 °C) with amount of PCL used, and there was a suspicious point in the 50/50 blends with both types of rubber. The lowest melting enthalpy of both blends was found at the 50/50 blended composition. The MFI results showed that PCL significantly affected the melt flow rate of both blends. The ENR-50/PCL blend flowed better than the STR5L/PCL blend. The conclusion was that this was due to the morphology of its phase structure having better uniformity than that of the STR5L/PCL blend. In compression set testing or measuring shape recovery, rubber directly influenced the recovery in all blends. The ENR-50/PCL blend had less recovery than the STR5L/PCL blend, probably due to the functional effects of epoxide groups and polarity mismatch. The hard phase PCL significantly affected the hardness of samples but improved shape recovery of the material. The ENR-50/PCL blend had better tensile properties than the STR5L/PCL blend. The elongation at break of both blends improved with a high rubber content. Hence, the ENR-50/PCL blend was superior to STR5L/PCL for printing purposes due to its better miscibility, uniformity, and flow, which are the keys to success for optimizing the fused deposition modeling conditions as well as the overall mechanical properties of products. Most blends in this study were only slightly different, but the 50/50 blend of ENR-50/PCL seemed to be near optimal for 3D printing.

Synergistically improving the anti-reversion property of natural rubber by zinc glycerolate and zinc laurate as environmentally friendly activators

Sulfur-vulcanized nature rubber (NR) usually accompanies with reversion, which is of great challenge to the application of the NR products. In this work, zinc glycerolate in combination with zinc laurate was incorporated into sulfur-vulcanized NR, for the purpose of effectively substituting the traditional activator zinc oxide. Curing characteristics, physical and mechanical properties and dynamic viscoelastic behavior of the sulfur-vulcanized NR were investigated. Compared with solo addition of zinc glycerolate, zinc glycerolate/zinc laurate significantly improved the anti-reversion property of the sulfur-vulcanized NR. Incorporation of zinc laurate also enhanced the processing fluidity, filler dispersion, and rolling resistance of the sulfur-vulcanized NR. Moreover, the mole fraction of zinc was reduced by 51% with using zinc glycerolate/zinc laurate, compared with the traditional vulcanizates activated by zinc oxide. Our work provides a green approach to fabricate sulfur-vulcanized NR with outstanding anti-reversion performance.