Rubber Coagulation Research Articles

An environmentally friendly and efficient technology to prepare high‐performance natural rubber: Electrophoretic coagulation

AbstractNatural rubber is bio‐based rubber, which plays an important role in carbon neutralization to reduce carbon dioxide emissions. It is widely used in the national economy because of its strain‐induced crystallization properties. However, the preparation process for natural rubber is backward and in urgent need of reform. Electrophoretic coagulation, as a new natural rubber coagulation process, was proposed in this paper. We designed electrophoresis equipment and optimized it through finite element analysis. Compared with traditional coagulation methods electrophoretic coagulation has outstanding advantages: high efficiency, no wastewater, and low odor. Compared with commercial natural rubber, electrophoretic coagulated natural rubber has a stronger supramolecular structure, better mechanical performances, and dynamic compression heat buildup. We also revealed the relationship between the structure and properties of different natural rubber.

The Impact on Properties of Block Rubber of Using Adulterated Coagulants in Cup Lumps of Natural Rubber

Cup lumps are raw materials used in block rubber production and commonly contain adulterants among the chemicals used for rubber coagulation. This study aimed to identify the composition and concentration of components in commercial coagulants for producing cup lumps in the Northeastern and Northern regions of Thailand. A further goal was to study the impact of using these cup lumps to make block rubber. Detection of coagulant concentration by ion chromatography found that 25% of the samples were composed of formate ions and 50% of the samples were composed of sulfate ions ranging from 17.89 to 93.46% and 36.17 to 97.74% by weight, respectively. Among the adulterated coagulants, they were mixed with formate ions and chloride ions in 18.75% of the samples and sulfate ions mixed with chloride ions in 6.25% of the samples. Additionally, block rubber containing adulterants had Po, PRI, and Mooney viscosity values that meet the lower grade STR 20 standard. Block rubber made from cup lumps coagulated using formic acid showed physical properties that met the STR 5 standard.

Silver nanoparticle synthesis using the serum obtained after rubber coagulation of skim natural rubber latex with chitosan solution

Silver nanoparticle synthesis using the serum obtained after rubber coagulation of skim natural rubber latex with chitosan solution

Evaluation of key factors for residual rubber coagulation in natural rubber processing wastewater

Key factors for residual rubber coagulation in natural rubber (NR) processing wastewater were evaluated via a laboratory-scale system comprising an anaerobic baffled reactor (ABR) and a downflow hanging sponge (DHS) reactor (ABR–DHS system). Hydraulic retention time (HRT), seeding of the core rubber, and existence of air are selected as key factors for rubber coagulation. In the ABR, longer HRT and seeding of the core rubber was not affected for rubber coagulation. Only biodegradable substances were consumed in the ABR. On the other hand, the DHS reactor achieved high removal efficiency of residual rubber by both coagulation and biological degradation. In addition, seeding of the core rubber to the DHS reactor enhanced rubber coagulation. The genera Gordonia, known as a rubber-degrading bacteria, were detected from the retained sludge in the DHS reactor. Therefore, the wastewater–air and wastewater–core rubber contacts are considered as key factors for residual rubber coagulation in the NR wastewater treatment. Furthermore, biodegraded residual rubber was considered as carbon source for denitrification in the DHS reactor.

L-Quebrachitol from acidic serum obtained after rubber coagulation of skim natural rubber latex

A scheme for retrieving l-quebrachitol, which is a starting material for drugs to treat diabetes and cancer, from the acidic serum obtained after acid coagulation of rubber particles in skim natural rubber latex was proposed in this work. The serum was firstly treated with Ba(OH)2, cationic and anionic exchangers and then with activated carbon. The mixture was finally crystallized with ethanol 3 times consecutively. After evaporating the remaining liquid, the white solid was obtained and characterized with FTIR and HPLC-ELSD techniques. The results of mass, pH, electrical conductivity and % Brix values were reported for each stream in the process so that the experiment could be repeated. It was found that the FTIR spectra had characteristic peaks similar to those of the commercial l-quebrachitol and the HPLC results showed that the solid contained a large fraction of l-quebrachitol with small fractions of other impurities. The proposed process could be annexed in the concentrated rubber industry without any modification of the conventional operation.

Differentiation of Rubber Cup Coagulum Through Machine Learning

Abstract A support vector machine classification algorithm was formulated to differentiate rubber cup coagulum according to the type of acid coagulant used. Two classification models were established, a binary classification algorithm and a model that can identify if formic, acetic, sulfuric acid, or no acid was used to induce coagulation. The models were based on the properties of the rubber cup coagulum that are easy to measure, such as tensile strength, water contact angle, and density. The binary classification model, which differentiates the industry-accepted formic acid-coagulated rubber cup coagulum from those which are not, exhibited satisfactory reliability, as evidenced by a 92% overall prediction accuracy and 71.4% cross-validation accuracy. Moreover, it was also determined that the rubber properties density, and water contact angle were important contributors for the classification. Acid-induced rubber coagulation is an important post-harvest process that influences the resulting rubber quality. Thus, the accurate differentiation of the rubber samples is useful for quality assurance purposes, as well as in policy enforcement.

Rapid and complete removal of guayule (Parthenium argentatum) leaves by cryodefoliation, and freeze and thaw induction of rubber particle coagulation

Production of natural rubber (NR), a vital natural resource for modern economies, currently is completely dependent upon tropical cultivation of the Para rubber tree (Hevea brasiliensis, Müll. Arg). One promising source of alternative rubber is guayule (Parthenium argentatum, Gray), which is currently being developed as an alternative source of NR. Guayule rubber accumulates as rubber particles in bark parenchyma and can be extracted in the form of latex by homogenizing the bark and then separating the latex from the non-latex components by centrifugation. Latex separation and purification processes are significantly hindered by fine solids from the co-homogenized leaves. Therefore, complete removal of leaves before homogenization is highly desired. However, guayule leaves do not naturally abscise and chemical defoliants cannot be utilized since these dehydrate the shrub and coagulate the latex, and physical leaf removal processes are tedious or inefficient. We demonstrate that liquid nitrogen can be used to embrittle the leaves without freezing the bark parenchyma, completely removing the leaves with a single physical blow, and then the defoliated branches can be homogenized with no loss of latex-containing bark and no leaf contamination. Under longer freezing times, rubber coagulation occurred in partially frozen tissue and during slow thawing. Furthermore, we demonstrate that the rubber coagulation, which occurs when guayule branches are frozen through and thawed before homogenization, can be avoided by rapid homogenization of the flash frozen branches in ambient temperature aqueous extraction buffer.

Pemanfaatan Sari Pati Umbi Gadung (Dioscorea hispida Dennst) Untuk Koagulasi Lateks Karet Alam (Hevea brasiliensis)

This research aims to know the utilization of gadung ( Dioscorea hispida Dennst) tuber concentrate on natural latex ( Hevea brasiliensis ) rubber coagulation. The design used in this study was completely randomized design (RAL) with 6 treatments and 4 replications consisting of control and treatment group with concentration of 20 ml, 40 ml, 60 ml, 80 ml and 100 ml. The parameters observed were latex coagulation by administering some concentrations of gadung tuber. One way Anava test with 0.05% significance level showed significant result that is F count = 53 and F table = 2,77. This shows that gadung tuber concentrate gives a very real effect on latex coagulation. Thus it can be concluded that there is the effect of gadung tuber concentrate to natural rubber latex coagulation.

LIPID CONTENT IN SMALL AND LARGE NATURAL RUBBER PARTICLES

ABSTRACT Knowledge of the surface composition of natural rubber (NR) latex is essential to manufacturers of latex goods. Films made from only small rubber particles (SRPs) and a mix of SRPs and large rubber particles (LRPs) differ in mechanical properties. The reason for this difference, which is still under debate, is hypothesized to be linked with biomolecules (proteins and lipids) present in the NR particle surface. In this study, we characterize the surface chemistry, particularly lipid content of the SRP and LRP, by performing investigations directly on these particles in aqueous conditions. Fluorescent probes were used to display protein and lipid affinity and analyze them in situ with steady-state fluorescence spectroscopy, fluorescence correlation spectroscopy, and fluorescence lifetime measurements. Results are atypical in showing that lipids are more abundant in LRPs than in SRPs, suggesting thicker and/or denser membranes in LRPs. The degree of membrane compacity affects rigidity, influences biomolecular interactions, and might impact natural rubber coagulation. These results provide additional insights into colloidal behavior of NR for more efficient industrial applications.

Anaerobic treatment of concentrated latex processing wastewater in two-stage upflow anaerobic sludge blanket

This study aims to investigate treatment performance of the two-stage upflow anaerobic sludge blanket (UASB) applied to concentrated latex processing wastewater in Thailand. First, optimal conditions including the hydraulic retention time (HRT) in the acid tank and the UASB tank, pH, and temperature (mesophilic and thermophilic) were determined. It was found that the HRT at 24 h and 48 h were the optimal HRT for the acid tank and the UASB tank, respectively. The pH of the system should be controlled at 7 to prevent rubber coagulation and to achieve high treatment performance, and the mesophilic condition (35°C) was found to be the optimal temperature. Second, the two-stage UASB was applied with the optimal conditions mentioned earlier with real wastewater at a latex mill. It was found that methane production was about 0·116 L CH4/g COD removed (16·3 – 22·8 m3CH4/d), and average chemical oxygen demand (COD) and suspended solids (SS) removal efficiency were about 82% and 92%, respectively. In case of SS removal, the results revealed that the two-stage UASB was capable of overcoming the limitations of the single-stage UASB in treating concentrated latex effluent. The results indicated that application of the two-stage UASB to concentrated latex processing wastewater is feasible. Nevertheless, combination with other treatment systems (e.g., oxidation pond, aerated lagoon) is necessary to meet Thailand's industrial effluent standards (in the case of COD).

Anaerobic treatment of concentrated latex processing wastewater in two-stage upflow anaerobic sludge blanketA paper submitted to the Journal of Environmental Engineering and Science.

This study aims to investigate treatment performance of the two-stage upflow anaerobic sludge blanket (UASB) applied to concentrated latex processing wastewater in Thailand. First, optimal conditions including the hydraulic retention time (HRT) in the acid tank and the UASB tank, pH, and temperature (mesophilic and thermophilic) were determined. It was found that the HRT at 24 h and 48 h were the optimal HRT for the acid tank and the UASB tank, respectively. The pH of the system should be controlled at 7 to prevent rubber coagulation and to achieve high treatment performance, and the mesophilic condition (35°C) was found to be the optimal temperature. Second, the two-stage UASB was applied with the optimal conditions mentioned earlier with real wastewater at a latex mill. It was found that methane production was about 0.116 L CH4/g COD removed (16.3–22.8 m3CH4/d), and average chemical oxygen demand (COD) and suspended solids (SS) removal efficiency were about 82% and 92%, respectively. In case of SS removal, the results revealed that the two-stage UASB was capable of overcoming the limitations of the single-stage UASB in treating concentrated latex effluent. The results indicated that application of the two-stage UASB to concentrated latex processing wastewater is feasible. Nevertheless, combination with other treatment systems (e.g., oxidation pond, aerated lagoon) is necessary to meet Thailand's industrial effluent standards (in the case of COD).

Effect of Polycaprolactam Fiber on Coagulation of Rubbers and on Properties of Rubbers, Rubber Stocks, and Vulcanizates

The effect of polycaprolactam fiber on the coagulation of butaidene-styrene rubber from the latex was studied.

The histology of Hevea brasiliensis phloem necrosis

AbstractPhloem necrosis of rubber tree(hevea brasiliensis)is characterized by cel wall degradation, alteration of the middle lamella, the vesiculation of endomembranes, the formation of tylosoids and the internal coagulation of rubber.

Improvement of Plant Material for Revegetation of Arid and Semi-Arid Regions

is to grow guayule in nurseries and transplant to the field after four months or more in the nursery beds. Field culture is similar to that of other agricultural crops, but with a lower water requirement and with emphasis on moisture control. Insects have not been a great hazard, but guayule is subject to many common diseases, especially on waterlogged soils. The rubber is contained in individual cells and hence the plant must be harvested to obtain the rubber. About three fourths of the rubber is in the stems and onefourth in the roots. The plants are therefore cut at a soil depth of about seven inches and the whole plant delivered to the extraction mill, where the leaves are first removed because they contain no rubber, and the rubber extracted by a process involving coagulation of rubber and breaking down the cell walls. The rubber is floated out in tanks, treated with acetone to remove resins, and finally dried prior to shipping. The application to conditions of the Sahel depends on the availability of suitable soil, climatic conditions, possible irrigation and adjustments to local, social and economic situations.

The Degradation of Rubber Solutions

Abstract From the beginning of our experiments we have called attention to the fact that the character of the degradation varies nit only with the prevailing temperature but also with the solvent used. In particular, if one compares the solutions obtained by the degradation of a given rubber (pale crepe) at a concentration of 0.02 in aromatic hydrocarbons, it is found that the color of the solution changes in the following way: In benzene at 80° the degraded solution remains colorless. In toluene at 93° the degraded solution becomes golden yellow. In xylene at 138–140° the degraded solution becomes dark brown. In cumene at 150–155° the degraded solution becomes brown-yellow. The temperature takes part in these changes through a pyrogenic action which in the case of xylene, can easily be detected by the odor, but this is not the only cause since cumene, used like xylene at the boiling temperature, gives a much lighter solution than would have been expected, and there is no pyrogenation or only a very slight one. Moreover, it is observed that when the degradation has reached a sufficiently high point, coagulation of rubber by the addition of alcohol or of acetone becomes impossible, and sometimes a very stable emulsion is formed, but the part emulsified does not represent anywhere nearly the total quantity of rubber, since the latter has been converted to a great extent into a form soluble in acetone. If the solution is evaporated by a method which makes possible a determination of the rubber it contained when it was not degraded, the quantity found after evaporation is very much less than that which should be present, and furthermore the product obtained is in a pasty state, almost liquid and gluey, as rubber would be if it had turned to a fatty condition.