Properties Of Natural Rubber Latex Research Articles

The influence of MoS2/carbon dots hybrid particles on mechanical properties of natural rubber latex

The influence of MoS2/carbon dots hybrid particles on mechanical properties of natural rubber latex

Optimized titanium dioxide loading for properties of natural rubber latex and acrylic emulsion blends

Blends of prevulcanized natural rubber (PVNR) and acrylic emulsion (AC) were prepared at the fixed PVNR/AC ratio of 30/70. Effects of titanium dioxide (TiO2) addition were optimized across the contents 0, 10, 20 and 30 parts per hundred parts of polymer (php) with respect to various properties. Morphological analysis revealed a two-phase system in which the PVNR particles were dispersed in the AC matrix. Incorporation of TiO2 induced a finer blend morphology in which a part of the TiO2 was located at the interfaces of blend components. The tensile strength increased with initial TiO2 loading and reached its maximum at 10 php loading, with an improvement by about 127% over the blend without filler. However, further increase in filler loading reduced the tensile strength, and the filler tended to agglomerate at those higher loadings. Thermal stability and storage modulus in rubbery region of the blends containing TiO2 were also improved over the unfilled blend, due to the improved morphology and the hydrogen bonds between TiO2 filler and polymer matrix. TiO2 improved water wettability and adhesion of the blend. The maximum peel strengths on wood and metal substrates were about 120% and 26% larger than for the reference unfilled blend. Such drastic improvements suggest that the filled blends may find applications as coating materials.

A study on preservatives on the structure and properties of natural rubber latex

A study on preservatives on the structure and properties of natural rubber latex

The mechanical and heat aging properties of natural rubber latex modified by carbon nanodots

AbstractDue to their unique structure and tuneable physical, optical, and electronic properties, carbon nanodots (CDs) become one of the perfect nano‐materials in many fields such as biomarkers, optical sensing, and catalysis. The application of CDs in modifying polymers has also attracted much interest. In this work, a simple process was employed for introducing CDs to modify natural rubber (NR) latex. Glucose was applied as the precursor to prepare CDs by hydrothermal method, subsequently, the crude CDs were directly added to NR latex at a very lower concentration to prepare NR/CDs films. The results of mechanical properties demonstrate that the 500% modulus, tensile and tear strength of NR composites are significantly improved by the introduction of CDs. When the theoretical loading of CDs is 2 phr, the tensile strength and tear strength of NR/CDs film reach to 33.1 MPa and 56.4 N/mm, and improve 17.8% and 29.4% than NR without CDs respectively. It is particularly noteworthy that when the amount of CDs is higher than 1.5 phr, the heat‐aging resistance of NR has been enhanced. It has been confirmed by crosslink density, dynamic mechanical analysis, and Fourier Transform Infrared Spectrometer analysis that CDs have a certain confinement effect on the mobility of rubber molecular segments through physical adsorption and chemical crosslinking. The Tube model theory was employed to calculate parameters of the network structure of NR/CDs films (based on the stress–strain curves), the results indicate that CDs give NR film more chemical crosslinking points and less entanglement network.Highlights The crude carbon nanodots are used to modify NR latex at a lower concentration The mechanical properties of NR films are obliviously improved The heat‐aging resistance of NR has been enhanced by adding carbon nanodots higher than 1.5 phr The Tube model theory are employed to analysis the crosslink network CDs give NR film more chemical crosslinking points and less entanglement network

The impact of non-deproteinization on physicochemical and biological properties of natural rubber latex for biomedical applications

Latex is a colloidal suspension derived from the Hevea brasiliensis tree, derived from natural rubber, poly(isoprene), and assorted constituents including proteins and phospholipids. These constituents are inherent to both natural rubber and latex serum. This investigation was undertaken to examine the impact of the deproteinization process on chemical and biological dynamics of natural rubber latex. Natural Rubber (NR) extracted from the pure latex (LNCP) was obtained through centrifugation, followed by six rounds of solvent purification (LP6). The structure was characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), swelling test, surface zeta potential (ζ), scanning electron microscopy (SEM) and in vitro assay. The results revealed that the LP6 group presented decreased swelling kinetics, reduced cell adhesion and proliferation, and a smoother surface with decreased negative surface charge. Conversely, the LNCP group shown accelerated swelling, heightened adhesion and cellular growth, and a more negatively charged and rougher surface. As such, the attributes of latex serum and proteins have potential usage across numerous biomedical applications.

Electron beam irradiation for enhancing the properties of natural rubber latex

Raw rubber must be vulcanized to produce a useful rubber product. Vulcanization is a chemical process that creates crosslinking points between rubber molecules, transforming it into a thermosetting material. This study aimed to prepare vulcanized natural rubber latex containing a sulfur curing package by irradiating it with electron beams at doses of 1–30 kGy. The crosslink density increased with increasing electron doses. Additionally, electron beam irradiation increased the entanglement of rubber molecules, resulting in superior mechanical properties such as modulus, tensile strength, elongation at break, and tear strength in the natural rubber latex. However, when high electron doses (>10 kGy) were applied, the crosslink density reduced owing to polymer degradation or chain scission, leading to inferior mechanical properties. To evaluate the potential of using irradiation as a replacement for conventional vulcanization processes, the properties of natural rubber latex containing a sulfur curing package vulcanized by electron beam irradiation were compared with those vulcanized by heat (conventional process). The mechanical properties of the natural rubber latex vulcanized by electron beam irradiation were superior to those of the rubber vulcanized by heat, with a 40% increase in modulus, 80% increase in tensile strength, 14% increase in elongation at break, and 36% increase in tear strength. According to these findings, electron beam irradiation, which offers high productivity and shorter processing time, is a suitable vulcanization process for natural rubber latex containing a sulfur curing package, with electron doses of 5 and 10 kGy providing superior overall balanced properties.

The Influence of Azidated Glycerol as a New Low Temperature Stabilizer on the Colloidal Properties of Natural Rubber Latex: For Latex Marine Transportation.

Natural rubber latex (NRL) is normally transported to a destination in colloid/liquid form. It requires large storage containers such as drums and the probability of latex leakage during transportation is high. This is prevalent especially when transporting latex by sea. To prevent latex spillage, the liquid form of NRL is transformed into solid/frozen latex by freezing. However, the coagulation/destabilization of NRL by freezing has been acknowledged as a problem for years. Therefore, this study proposed a new low temperature stabilizer named azidated glycerol (AG) to be incorporated in NRL liquid before the freezing process. AG was prepared by a chemical reaction of pure glycerol with sodium azide. NRL containing AG was then frozen at a temperature of -4 °C. After 24 h of freezing, the frozen latex was thawed at ambient temperature for 1 h followed by heating in a water bath at 40 °C for another 1 h. The regenerated latex was then allowed to stand at room temperature before testing. The effect of AG on the colloid properties before and after the freeze-thaw processes was studied. The production of AG was confirmed by the appearance of a peak in the range of 2160-2120 cm-1, corresponding to N=N=N stretching, confirming the introduction of an azide group into the glycerol molecule. Modifying NRL with AG did not significantly influence the TSC of latex. Increasing the AG content up to 0.4 phr resulted in an increase in MST from 699 s to 828 s. An AG content of 0.2 phr resulted in the highest anionically stabilized latex as indicated by zeta potential values of -59.63 mV (before freezing) and -56.27 mV (after thawing). It is concluded that the AG produced in this study can be used as an anti-freeze stabilizer for NRL and is suitable for latex marine transportation.

A Comparative Study on X-ray Shielding and Mechanical Properties of Natural Rubber Latex Nanocomposites Containing Bi2O3 or BaSO4: Experimental and Numerical Determination.

This work experimentally determined the X-ray shielding and morphological, density, and tensile properties of sulfur-vulcanized natural rubber latex (SVNRL) nanocomposites containing varying content of nano-Bi2O3 or nano-BaSO4 from 0 to 200 phr in 100 phr increments, with modified procedures in sample preparation to overcome the insufficient strength of the samples found in other reports. The experimental X-ray shielding results, which were numerically verified using a web-based software package (XCOM), indicated that the overall X-ray attenuation abilities of the SVNRL nanocomposites generally increased with increasing filler content, with the 0.25-mm-thick SVNRL films containing 200 phr of the filler providing the highest overall X-ray shielding properties, as evidenced by the highest values of lead equivalence (Pbeq) of 0.0371 mmPb and 0.0326 mmPb in Bi2O3/SVNRL nanocomposites, and 0.0326 mmPb and 0.0257 mmPb in BaSO4/SVNRL nanocomposites, for 60 kV and 100 kV X-rays, respectively. The results also revealed that the addition of either filler increased the tensile modulus at 300% elongation (M300) and density but decreased the tensile strength and the elongation at break of the Bi2O3/SVNRL and BaSO4/SVNRL nanocomposites. In addition, the modified procedures introduced in this work enabled the developed nanocomposites to acquire sufficient mechanical and X-ray shielding properties for potential use as medical X-ray protective gloves, with the recommended content of Bi2O3 and BaSO4 being in the range of 95–140 phr and 105–120 phr, respectively (in accordance with the requirements outlined in ASTM D3578-19 and the value of Pbeq being greater than 0.02 mmPb). Consequently, based on the overall outcomes of this work, the developed Bi2O3/SVNRL and BaSO4/SVNRL nanocomposites show great potential for effective application in medical X-ray protective gloves, while the modified procedures could possibly be adopted for large-scale production.

Investigation of Field Performance and Film Properties of Natural Rubber Latex Preserved with a Novel Chemical

The traditional long-term preservative system of latex has an impact on environmental air pollution by ammonia and leads to the production of carcinogenic nitrosamine substances by tetramethyl thiuram disulfide (TMTD). In this research, ammonia and a novel preservative with a polysulfidic link were compounded and tested as a novel traditional long-term latex preservative system, to overcome the drawbacks of traditional preservative systems. Control samples were prepared with ammonia as the standard preservative. In addition, ammonia and the novel chemical mixed samples were also prepared for investigating the combined effect. After the preservation treatment, the stable nature of field NR latex was evaluated via the Volatile Fatty Acid (VFA) test based on ASTM D 1076 standard. The Dry Rubber Content (DRC) test and Total Solid Content (TSC) test were carried out for VFA calculation purposes based on ISO126:2005 and ASTM D 1076 standards, respectively. The alkalinity test was carried out to maintain the required ammonia content in latex. In the first trial, traditional dispersion preparation of novel chemical dispersion failed due to the large particle size of the novel chemical. Therefore, two different novel chemical dispersions were prepared in the second trial, where dispersions 1 and 2 were prepared with wetting agents and without using a wetting agent, respectively. It was found that 0.020%v/v and 0.025% v/v concentrations of the novel chemical from dispersion 1 allowed the preservation of field NR latex for 8 days. A low concentration (0.015% v/v) of the novel chemical was able to keep latex with good stability for 5 days. The novel chemical dispersion without a wetting agent exhibited a marvelous preservative system to NR latex than with a wetting agent, because the wetting agent creates a barrier between particles of novel chemical and latex particles. The novel preservative acts as a good preservative while reducing the fumes of ammonia being emitted and eliminating the carcinogenic nitrosamine emission from TMTD.

Various coagulation techniques and their impacts towards the properties of natural rubber latex from Hevea brasiliensis — a comprehensive review related to tyre application

Coagulation is the first crucial step in the processing of natural rubber (NR) that happens naturally or is induced by various techniques. The mechanism of Hevea latex coagulation involves the destabilization and aggregation of latex particles that are influenced by different factors. By understanding the basics of coagulation process, the use of different coagulation techniques and their efficiency are illustrated in this paper. The corresponding impact on the technological properties of unvulcanized NR is connected to the choice of coagulation technique. For instance, the microstructure of natural coagulated NR relies on the precedence of microbial activities which further decides the mesostructure and macrostructure properties. As NR is widely used in the rubber manufacturing industry notably tyres, the subsequent impacts of coagulated NR using different techniques are described from the aspect of processing, vulcanization characteristics, mechanical properties, and ageing retention properties of NR vulcanizate. By providing such an overview, the connection of coagulation technique of Hevea latex to the rubber industries is established to have a more comprehensive understanding when selecting the best option for the respective application.

Colloidal and rheological properties of natural rubber latex concentrated with hydroxyethyl cellulose and sodium dodecyl sulphate

AbstractNatural rubber latex (NRL) is a complex colloidal system composed of rubber particles surrounded by a layer of phospholipids and proteins maintaining its colloidal stability. NRL creaming is a nonrobust concentration method, and its colloidal and rheological properties can be altered due to the presence of creaming agents and surfactants. Both properties must remain stable over time after creaming to ensure conditions for subsequent manufacturing processes. These properties have been evaluated for synthetic latex, but not for NRL in which the clone variety and phenological factors make the system being always different. In this research, hydroxyethyl cellulose (HEC) and sodium dodecyl sulphate (SDS) are used to concentrate NRL and response surface methodology was selected to optimize the colloidal and rheological properties of creamed NRL. Flocculation and stabilization by depletion are involved on NRL concentration depending on HEC and SDS concentration. Those agents modify NRL zeta potential in a range of −78 and −63 mV, and viscosity increases more than 10 times the raw NRL value. SDS plays a key role on enhancement of the creaming process and in electrostatic stability because its anionic nature. Physicochemical interactions between NRL, HEC, and SDS are proposed.

Electromagnetic wave absorbing properties of carbon black-filled natural rubber latex

This article investigated the electromagnetic wave absorbing properties of natural rubber latex (NRL) foam filled with carbon black. The influence of different grades (N330, N660 and conductive grade) of carbon black and content on the foam morphology and electromagnetic wave absorption were of interest. The experimental results revealed that the addition of carbon black can improve the ability of electromagnetic wave absorption NRL over a wide frequency range. The NRL foam filled with the conductive carbon black exhibited more electromagnetic wave susceptibility in comparison to the those filled with classical carbon black. The addition of carbon black results in a decrease in cell size and increase in the number of foam cells. The proposed NRL foams are expected to be used as electromagnetic absorber in lightweight and flexible electromagnetic shielding materials.

Reinforcing natural rubber by amphiphilic graphene oxide for high-performance catheters

Graphene oxide (GO) has been considered as a promising nanofiller to reinforce water-borne polymer due to its exceptional mechanical properties and good dispersibility in an aqueous solution. However, the re-aggregation of hydrophilic GO sheets in a hydrophobic polymer matrix with the evaporation of water, resulting from remarkable discrepancy of the interfacial energy, remains a significant challenge to achieve the high-performance GO-based polymer nanocomposites. Herein, the amphiphilic graphene oxide (AGO) rather than the conventional GO is applied to enhance the mechanical properties of natural rubber latex (NRL) through simple solution blending. Our results show that the AGO demonstrates not only good dispersibility in the NRL aqueous solution but also strong hydrophobic interaction with the NRL particles. Benefiting from this amphiphilic character, the good dispersibility of AGO in the NRL matrix is realized after the oven-drying process, leading to a simultaneous enhancement in tensile strength (up to 35 MPa) and elongation at break (up to 1100%). In particular, it is found that the NRL tube, a kind of catheter, demonstrates a remarkable improvement in both blasting pressure, blasting volume with just a small amount addition of AGO (as less as 0.1%). This work provides a simple, green, and efficient route to fabricate high-performance polymer latex/graphene nanocomposites.

Enhanced X-ray shielding properties of NRL gloves with nano-Bi2O3 and their mechanical properties under aging conditions

This work investigated X-ray shielding and the mechanical, morphological, and physical properties of natural rubber latex (NRL) gloves vulcanized using either a sulfur or gamma curing system, with the addition of varying nano-Bi2O3 contents from 50 to 200 parts per hundred parts of rubber by weight (phr) for potential use in the fabrication of lead-free X-ray-protective latex gloves. The results showed that the addition of nano-Bi2O3 fillers enhanced the X-ray shielding ability and density of the composites. The results also revealed that nano-Bi2O3 slightly increased the tensile modulus but decreased the tensile strength and elongation at break in both curing systems. Furthermore, 90–170 phr of nano-Bi2O3 provided the optimum contents that produced gamma-vulcanized natural rubber latex (GVNRL) gloves having both X-ray shielding and mechanical properties greater than the minimum requirements for commercial X-ray protective gloves and examination gloves (ASTM D3578-19). In addition, it was found that gamma and thermal aging affected the mechanical properties, with sulfur-vulcanized natural rubber latex (SVNRL) gloves having increased overall mechanical properties, while GVNRL gloves exhibiting lower properties. The overall results suggested that the developed GVNRL gloves had great potential for use as effective X-ray protective gloves with nano-Bi2O3 acting as a suitable X-ray protective filler.

Genetic diversity associated with natural rubber quality in elite genotypes of the rubber tree

The objective of this study was to evaluate the genetic variability of natural rubber latex traits among 44 elite genotypes of the rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Müell. Arg.]. Multivariate analysis and machine learning techniques were used, targeting the selection of parents that demonstrate superior characters. We analyzed traits related to technological or physicochemical properties of natural rubber latex, such as Wallace plasticity (P0), the plasticity retention index [PRI (%)], Mooney viscosity (VR), ash percentage (Ash), acetone extract percentage (AE), and nitrogen percentage (N), to study genetic diversity. Multivariate [unweighted pair group method with arithmetic means (UPGMA) and Tocher)] and machine learning techniques [K-means and Kohonen’s self-organizing maps (SOMs)] were employed. The genotypes showed high genetic variability for some of the evaluated traits. The traits PRI, Ash, and PO contributed the most to genetic diversity. The genotypes were classified into six clusters by the UPGMA method, and the results were consistent with the Tocher, K-means and SOM results. PRI can be used to improve the industrial potential of clones. The clones IAC 418 and PB 326 were the most divergent, followed by IAC 404 and IAC 56. These genotypes and others from the IAC 500 and 400 series could be used to start a breeding program. These combinations offer greater heterotic potential than the others, which can be used to improve components of rubber latex quality. Thus, it is important to consider the quality of rubber latex in the early stage of breeding programs.

Effects of post-gamma irradiation on swelling and mechanical properties of gamma vulcanized natural rubber latex (GVNRL) films

Gamma vulcanized natural rubber latex (GVNRL) films have shown promising properties for various applications that require less hazardous chemicals used or released during manufacturing and/or utilization. Examples of potential applications include the uses as chemical-free latex gloves in medical or food-related facilities and as stretchable latex covers for food and agricultural products. However, due to possible degradation on swelling and mechanical properties of these films from post-gamma irradiation used for sterilization, thorough investigations are required in order to fully understand their possible changes and/or degradations in properties of interest. As a result, this work investigated on effects of post-gamma irradiation on swelling and mechanical properties of natural rubber latex (NRL) films, which were pre-vulcanized using 12-kGy and 24-kGy gamma irradiation. The properties of interest in this work included tensile modulus at 300% elongation, tensile strength, and elongation at break, as well as other related physical properties such as swelling ratios and crosslink densities. The results showed that, for samples before post-gamma irradiation, the GVNRL films with 24-kGy vulcanizing dose had higher tensile modulus, tensile strength, and crosslink density, but lower elongation at break and swelling ratio, than the films with 12-kGy vulcanizing dose. However, after post-gamma irradiation at the accumulated dose of 24 kGy, the films with 12-kGy vulcanizing dose showed significant improvements in the values of tensile modulus, tensile strength, and crosslink density, whereas the films with 24-kGy vulcanizing dose showed noticeably degradation in these properties. Hence, the overall results suggested that, while higher gamma vulcanizing doses could initially produce NRL films with higher mechanical strength, they were more negatively affected by post-gamma irradiation such that mechanical degradation could be observed.

Contrastive Study on Properties of Acid and Microorganisms Coagulated Natural Rubber during Accelerated Storage

The properties of natural rubber latex coagulated by acid and microorganisms during accelerated storage were contrasted, respectively. The molecular weight, gel content, Mooney viscosity, Wallace initial plasticity and the plasticity retention index of natural rubber latex during the accelerated storage period were analysed. The results indicate that prolonged storage time leads to a gradual increase in the molecular weight, gel content, crosslink density and Wallace initial plasticity, whereas plasticity retention index reduces. Wallace initial plasticity exhibits significant correlation, while plasticity retention index indicates a negative correlation with both molecular weight and gel content, respectively. The molecular structure and properties of natural rubber latex coagulated by microorganisms are significantly different from those of natural rubber coagulated by acid. The molecular weight, gel content and Wallace initial plasticity of natural rubber latex coagulated by microorganisms are higher than those of natural rubber latex coagulated by acid, while plasticity retention index and protein content of natural rubber latex coagulated by microorganisms is lower than that of natural rubber latex coagulated by acid.

Synthesis and Characterization of Epoxidized Natural Rubber Latex with Different Epoxide Content

To improve properties of natural rubber latex as water-barrier paperboard coatings, epoxidized natural rubbers (ENRs) were synthesized via in situ epoxidation from high ammonia concentrated natural rubber latex with formic acid and hydrogen peroxide. The reaction was performed at 45°C and 20°C. The obtained products were ENR20, ENR50, ENR70, and ENR85 according to the mole percentage of epoxide groups in ENR. ENRs were characterized by NMR Spectroscopy, DSC, DMTA and water vapor transmission rate determination. Epoxidization rate is faster at high temperature, but stable epoxide latex with high epoxide level can be obtained only at low temperature. The epoxidation reaction homogeneously takes place in latex and the Tg of ENRs increases almost linearly with epoxide content. Although hydrophility of polar epoxide chain results in high water vapor transition rate, ENR50 is the potential barrier coating material compared with other ENR samples.

The rubber tree genome shows expansion of gene family associated with rubber biosynthesis

Hevea brasiliensis Muell. Arg, a member of the family Euphorbiaceae, is the sole natural resource exploited for commercial production of high-quality natural rubber. The properties of natural rubber latex are almost irreplaceable by synthetic counterparts for many industrial applications. A paucity of knowledge on the molecular mechanisms of rubber biosynthesis in high yield traits still persists. Here we report the comprehensive genome-wide analysis of the widely planted H. brasiliensis clone, RRIM 600. The genome was assembled based on ~155-fold combined coverage with Illumina and PacBio sequence data and has a total length of 1.55 Gb with 72.5% comprising repetitive DNA sequences. A total of 84,440 high-confidence protein-coding genes were predicted. Comparative genomic analysis revealed strong synteny between H. brasiliensis and other Euphorbiaceae genomes. Our data suggest that H. brasiliensis’s capacity to produce high levels of latex can be attributed to the expansion of rubber biosynthesis-related genes in its genome and the high expression of these genes in latex. Using cap analysis gene expression data, we illustrate the tissue-specific transcription profiles of rubber biosynthesis-related genes, revealing alternative means of transcriptional regulation. Our study adds to the understanding of H. brasiliensis biology and provides valuable genomic resources for future agronomic-related improvement of the rubber tree.

Morphology and mechanical properties of natural rubber latex films modified by exfoliated Na‐montmorillonite/polyethyleneimine‐g‐poly (methyl methacrylate) nanocomposites

ABSTRACTNa‐montmorillonite/polyethyleneimine‐g‐poly(methyl methacrylate) (Na‐MMT/PEI‐g‐PMMA) nanocomposite latexes were prepared by soap‐free emulsion polymerization in the aqueous suspension of Na‐MMT. The exfoliated morphology of the nanocomposites was confirmed by XRD and TEM. With the aim of improving morphology and mechanical properties of natural rubber latex (NRL) films, the synthesized Na‐MMT/PEI‐g‐PMMA nanocomposites were mixed with NRL by latex compounding technology. The results of SEM and AFM analysis showed that the surface of NRL/Na‐MMT/PEI‐g‐PMMA film was smoother and denser than that of pristine NRL film while Na‐MMT was dispersed uniformly on the fracture surface of the modified films, which suggested the good compatibility between NRL and Na‐MMT/PEI‐g‐PMMA. The tensile strength of NRL/Na‐MMT/PEI‐g‐PMMA films was increased greatly by 85% with 10 phr Na‐MMT/PEI‐g‐PMMA when Na‐MMT content was 3 wt % and the elongation at break also increased from 930% to 1073% at the same time. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43961.