Surface Of Rubber Particles Research Articles

Effect of proteins as constituents of island-nanomatrix structure on vulcanization of natural rubber

Effect of proteins, constituents of the island-nanomatrix structure, on dispersion of zinc to natural rubber was investigated by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) and focused ion beam-scanning electron microscopy-energy dispersive X-ray spectroscopy (FIB-SEM-EDX). Films of natural rubber and deproteinized natural rubber (DPNR) prepared with urea were embedded in a mixture of ZnO, vulcanization accelerator and sulfur, and they were heated at 150 °C for 5 h. Migration of Zn from surface to inside of the films was observed by FIB-SEM-EDX. The Zn migrated from the surface to 14 μm for natural rubber, but not for DPNR. The optimum vulcanization time for natural rubber was short, i.e., about 4 min, whereas it was long for DPNR, i.e., about 15 min. To confirm the effect of the proteins, a latex-mixed rubber compound was prepared by mixing the latex with sulfur, ZnO and vulcanization accelerator followed by drying with a hotplate at 150 °C for 45 s since the proteins are segregated on the surface of natural rubber particles in the latex stage. Vulcanization was accelerated for the latex-mixed natural rubber compared with mechanically mixed natural rubber compound that was prepared by mixing natural rubber with ZnO, vulcanization accelerator and sulfur with a two-roll mill. The resulting latex-mixed natural rubber vulcanizate was superior in mechanical properties to the mechanically mixed natural rubber vulcanizate. It was found by rubber-state NMR spectroscopy that the difference in mechanical properties was attributed to the difference in the cis-1,4-average sequence length of the vulcanizates, which came from the difference in the dispersion of Zn.

Microbially Mediated Rubber Recycling to Facilitate the Valorization of Scrap Tires.

The recycling of scrap tire rubber requires high levels of energy, which poses challenges to its proper valorization. The application of rubber in construction requires significant mechanical and/or chemical treatment of scrap rubber to compatiblize it with the surrounding matrix. These methods are energy-consuming and costly and may lead to environmental concerns associated with chemical leachates. Furthermore, recent methods usually call for single-size rubber particles or a narrow rubber particle size distribution; this, in turn, adds to the pre-processing cost. Here, we used microbial etching (e.g., microbial metabolism) to modify the surface of rubber particles of varying sizes. Specifically, we subjected rubber particles with diameters of 1.18 mm and 0.6 mm to incubation in flask bioreactors containing a mineral medium with thiosulfate and acetate and inoculated them with a microbial culture from waste-activated sludge. The near-stoichiometric oxidation of thiosulfate to sulfate was observed in the bioreactors. Most notably, two of the most potent rubber-degrading bacteria (Gordonia and Nocardia) were found to be significantly enriched in the medium. In the absence of added thiosulfate in the medium, sulfate production, likely from the desulfurization of the rubber, was also observed. Microbial etching increased the surface polarity of rubber particles, enhancing their interactions with bitumen. This was evidenced by an 82% reduction in rubber-bitumen separation when 1.18 mm microbially etched rubber was used. The study outcomes provide supporting evidence for a rubber recycling method that is environmentally friendly and has a low cost, promoting pavement sustainability and resource conservation.

A comprehensive review on polystyrene/waste rubber blends: Effective parameters on mechanical properties

AbstractPolystyrene (PS), as a commercial thermoplastic polymer, suffers from brittleness at low temperatures. Blending with elastomers can resolve this defect. In this regard, waste rubbers from tires, shoes, and other sources are promising candidates for some applications. This approach of waste rubber recycling is an environmental‐friendly and economical method to produce value‐added products. This work aims to comprehensively review all reported cases regarding PS (or high‐impact polystyrene, HIPS, and expanded polystyrene, EPS)/waste rubber blends. The influences of different parameters on the mechanical properties were carefully summarized, including mixing conditions (temperature, mixing time, rotor speed, and mixing sequence), rubber content, rubber particle size, compatibilizer addition, rubber devulcanization, and surface treatment of rubber. Some parameters had a negligible effect on the mechanical properties, such as the rotor speed in the mixing process, while significant influences were observed for some parameters, such as rubber content. The effect of some parameters was remarkable only at low or high rubber loading, such as particle size and solvent‐inducing surface treatment of rubber, respectively. Finally, the effects of aforementioned parameters on tensile and impact strengths were compared and recommendations for future research in this field were suggested.Highlights All reported research regarding PS/waste rubber blends was comprehensively reviewed. All different factors influencing mechanical properties were carefully summarized. The effects of different factors on tensile and impact strengths were compared.

Influence of different protein contents from several clonal varieties of Hevea brasiliensis latex on the properties of cured natural rubber film using glutaraldehyde (GA) as a curing agent

Natural rubber films were prepared from four different Hevea brasiliensis clones, namely RRIM600, RRIT251, PB235, and BPM24, using the creamed concentrated latex method. The creamed latexes were characterized by their protein content and particle sizes. The rubber particle surface characteristics were monitored using transmission electron microscopy (TEM). It was observed that the particle sizes of all clones varied in the range of 1.0–2.5 µm. Moreover, the RRIT251 clone exhibited higher protein content than the other clones. The influence of protein content on the properties of cured natural rubber (NR) was investigated using glutaraldehyde as a cross-linking agent. Mechanical properties, crosslink density, relaxation behavior, and heat resistance indicated by T90 (temperature scanning stress relaxation, TSSR) were considered. The crosslink density of cured NR increased with higher protein content. This phenomenon can be attributed to the strong formation of rubber chains with GA cross-links through the amino groups of proteins present in rubber molecules. Consequently, Hevea brasiliensis clones with higher protein content facilitate improved crosslink formation within the GA system, resulting in enhanced mechanical and thermo-oxidative degradation properties (T90 from TSSR test).

Waste Silicone Rubber in Three-Dimensional Conductive Networks as a Temperature and Movement Sensor.

Constructing a three-dimensional (3D) conductive network in a polymer matrix is a common method for preparing flexible sensors. However, the previously reported methods for constructing a 3D conductive network generally have shortcomings such as uncontrollable processes and insufficient network continuity, which limit the practical application of this method. In this work, we report a method for constructing a dual 3D conductive network. The carbon nanotube/graphene oxide co-continuous network (primary network) was introduced on the surface of the waste silicone rubber particles (WSRPs) through the adhesion of polydopamine (PDA), and then WSRPs were bonded into a porous skeleton using nanocellulose. The carbon fiber/carbon ball interconnection network (secondary network) was constructed in liquid silicone rubber (LSR) through the interaction of host-guest dendrimers and was filled into the WSRP skeleton. The dual 3D conductive network structure endowed the sensor with high electrical and thermal conductivity, outstanding stability, and excellent durability. In addition, the sensor showed high strain sensitivity and excellent stability when detecting human body temperature and motion behavior, and the pressure distribution can be spatially mapped through the sensor matrix. These demonstrations give our sensor high potential in the fields of smart devices, body monitoring, and human-machine interfaces.

In vitro studies on the degradation of common rubber waste material with the latex clearing protein (Lcp1VH2) of Gordonia polyisoprenivorans VH2.

The enzymatic degradation of the rubber polymer poly(cis-1,4-isoprene), e.g. by the latex clearing protein Lcp1VH2 of Gordonia polyisoprenivorans VH2 has been demonstrated with latex milk or pure isoprene-rubber particles, recently. Unfortunately, carbon black filled vulcanized rubber (CFVR) making the biggest part of worldwide rubber wastes, contains several harmful additives making microbial and enzymatic rubber degradation challenging. However, this study demonstrates the successful enzymatic cleavage of industrially produced CFVR. The formation of the cleavage products, oligo(cis-1,4-isoprenoids), from incubating CFVR particles with Lcp1VH2 was detected by HPLC-MS. Various organic solvents were tested to remove harmful or inhibiting additives like antioxidants to enhance product formation. The pretreatment of CFVR particles, especially with chloroform or cyclohexane, significantly improved the degradation. It was also demonstrated that reducing the particles size and thus increasing the enzymatically accessible surface area of the particles led to a strong acceleration of the degradation process. Furthermore, ATR-IR analyses showed that Lcp1VH2 led to the functionalization of the rubber particle surface with carbonyl groups by cleaving isoprene chains, still linked to the particle. Both, the oligo(cis-1,4-isoprenoids) as well as the functionalized rubber particles, are potentially important products, which can be reused as fine chemicals or as additives in rubber production. The present study, showing the enzymatic degradation of common CFVR for the first time, takes an important step towards a new way of rubber waste disposal and indicates the economic feasibility of an efficient and environmentally friendly recycling process by using the rubber oxygenase Lcp1VH2.

The Impact of Ground Tire Rubber Oxidation with H2O2 and KMnO4 on the Structure and Performance of Flexible Polyurethane/Ground Tire Rubber Composite Foams.

The use of waste tires is a very critical issue, considering their environmental and economic implications. One of the simplest and the least harmful methods is conversion of tires into ground tire rubber (GTR), which can be introduced into different polymer matrices as a filler. However, these applications often require proper modifications to provide compatibility with the polymer matrix. In this study, we examined the impact of GTR oxidation with hydrogen peroxide and potassium permanganate on the processing and properties of flexible polyurethane/GTR composite foams. Applied treatments caused oxidation and introduction of hydroxyl groups onto the surface of rubber particles, expressed by the broad range of their hydroxyl numbers. It resulted in noticeable differences in the processing of the polyurethane system and affected the structure of flexible composite foams. Treatment with H2O2 resulted in a 31% rise of apparent density, while the catalytic activity of potassium ions enhanced foaming of system decreased density by 25% and increased the open cell content. Better mechanical performance was noted for H2O2 modifications (even by 100% higher normalized compressive strength), because of the voids in cell walls and incompletely developed structure during polymerization, accelerated by KMnO4 treatment. This paper shows that modification of ground tire rubber is a very promising approach, and when properly performed may be applied to engineer the structure and performance of polyurethane composite foams.

Grafting waste rubber powder and its application in asphalt

Herein, rubber asphalt was modified to improve its comprehensive performance and the mechanism of its modification was investigated. Unmodified rubber powder was first treated with hydrogen peroxide, and then, grafted with prepolymer. The mechanism of modification of rubber powder and its effect on the structure and properties of rubber powder/asphalts were tested and characterized. Fourier transform infrared spectroscopy analysis proved that prepolymer was successfully grafted onto the surface of rubber particles. X-ray photoelectron spectrometer test revealed that graft modified rubber powder possessed high oxygen content along with the presence of nitrogen. These results indicated that rubber powder was successfully modified. The graft modified rubber powder was then applied to prepare rubber asphalt, significantly improving the low-temperature resistance to cracking and the stability performance, while it reduced high-temperature construction viscosity of rubber asphalt. The modification of rubber powder enhanced the dispersion of rubber powder in asphalt. The graft modified rubber powder/asphalt exhibited the highest weight fraction of restricted molecular layers, demonstrating the enhanced interfacial interaction between the graft modified rubber powder and asphalt matrix, which could be attributed to the simultaneous effect of physical entanglement and chemical bonding effect.

Entropic and Energetic Elasticities of Natural Rubber with a Nanomatrix Structure.

The entropic and energetic elasticities of natural rubber with a nanomatrix structure are investigated by measuring the viscoelastic properties of deproteinized natural rubber (DPNR)-graft-polystyrene (PS). A nanomatrix structure is formed by graft copolymerization of styrene onto the surface of natural rubber particles, followed by coagulation. The morphology of the nanomatrix structure is observed with transmission electron microscopy. Natural rubber particles with about 1 μm diameter are well dispersed in a nanomatrix of PS. The horizontal shift factor (aT) and vertical shift factor (bT) are determined by superposition to create a master curve according to the time-temperature superposition principle. The positive slope of DPNR appears in the plot of bT versus temperature, suggesting that entropic elasticity occurs. In contrast, the slopes of DPNR-graft-PS are negative at lower temperatures but positive at higher temperatures. The negative slope, which suggests entropic elasticity, may be attributed to the formation of a nanomatrix structure. Natural rubber with a nanomatrix structure realizes both energetic elasticity and entropic elasticity.

Surface modification of ground tire rubber particles by cold plasma to improve compatibility in rubberised asphalt

ABSTRACT The inert surface of Ground Tire Rubber (GTR) particles results in its weak compatibility with asphalt matrix and thus causes serious phase separation in rubberised asphalt. Meanwhile, plasma treatment is able to modify the polymer surface effectively. This study applied cold plasma to modify the surface of GTR particles for compatibility improvement in rubberised asphalt. The surface characteristics of plasma-treated GTR particles with varying treatment power and time were investigated, by means of water contact angle metre, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope (SEM), respectively. The results reported the enhanced surface hydrophilicity, lipophilicity, and roughness as well as the incorporation of oxygen-containing functional groups of GTR particles after plasma treatment. The optimal processing parameters were determined as the discharge power of 250 W and the processing time of 8 min. The GTR-asphalt compability after the most effective plasma treatment was evaluated by measuring the storage stability and rotational viscosity of rubberised binder. Regardless of base asphalt source, GTR particle size and dosage, cold plasma treatment truly enhanced the compatibility. Furthermore, the increased dosage from 10% to 20% and the decreased size from 30 to 80 mesh generally had a growing positive effect on compatibility.

Mechanical properties and durability of rubberized and SBR latex modified rubberized concrete

This paper analyses how rubber waste, used as replacement of fine aggregate in concrete mixes, affects mechanical properties and durability of concrete: freeze-thaw resistance, water absorption by immersion, and sulphate resistance. Concrete was modified by carboxylated styrene butadiene rubber (SBR) latex to get better bonding properties between rubber and hardened cement paste. Control specimens were made of concrete mix without crumb rubber. Scrap tyre rubber powder (crumb rubber – CR) of fraction 0/1mm and 1/2mm was used as fine aggregate. CR was used to replace a portion of fine aggregate at 5% of the total aggregate content. CR of fraction 0/1mm was found to improve freeze-thaw resistance: freeze-thaw resistance test results were similar to those of concrete with traditional air entrainment systems. On the contrary, coarser rubber particles of fraction 1/2mm had a negative effect on freeze-thaw resistance of concrete. These findings can be explained by the smoother texture and a more regular shape of coarse rubber particles up to 2 mm in size and the rougher texture and irregular shape of fine particles up to 1 mm in size. A complex profile of rubber particle surface results in higher volume of air voids, higher closed porosity and higher freeze-thaw resistance of concrete modified with crumb rubber. The test results confirmed that concrete modified with crumb rubber of smaller fraction had higher closed porosity and higher freeze-thaw durability factor Kf. The results also confirmed that Kf values calculated from concrete porosity parameters can be conveniently used to predict freeze-thaw resistance and durability of concrete. The tests have shown that the modification of concrete with rubber waste has no positive effect on sulphate resistance, compressive strength and modulus of elasticity.

Rheological and chemical characterization of plasma-treated rubberized asphalt using customized extraction method

The storage instability issue of rubberized asphalt caused by the inherent incompatibility significantly affects its engineering performances. In this study, cold plasma was utilized to activate the inert surface of Crumb Rubber (CR) particles to further improve the compatibility in rubberized binder. Using a customized extraction method and a developed model, the mechanism of Cold Plasma Effect (CPE) was investigated by rheological and chemical methods, respectively. In terms of the rheological characterization by Dynamic Shear Rheometer (DSR) testing, the CPE on rheology was identified as the primary Particle Effect (PE) and the secondary Interaction Effect (IE). In addition, CPE together with its PE and IE portion constantly increased with an increase in CR content, while no significant tendency was found with the varying size. With respect to the chemical characterization by Gel Permeation Chromatography (GPC) testing, the results indicated the cold plasma treatment significantly resulted in an increase in the Large Molecular Size (LMS) fraction of binder, and this effect was more evident as the CR content increased and the size reduced. However, the Fourier Transform Infrared Spectroscopy (FTIR) testing failed to characterize the effect of cold plasma treatment. Furthermore, the statistical analyses reported a strong correlation between the above corresponding changes in rheology and chemistry. Above all, the mechanism of CPE on binder properties could thus primarily be seen as the promotion in diffusion of lighter fractions of asphalt binder into the plasma-treated CR particles.

The Potential of Enzyme in Reducing the Maturation Time and the Use of Ammonia in Concentrated Natural Rubber Latex

One of the most important parameters for indicating colloidal stability of concentrated natural rubber latex (CNRL) is the mechanical stability time (MST). The MST of CNRL after centrifugation is always low and slowly increases with storage time due to gradual hydrolysis of phospholipid on the surface of rubber particles into fatty acid soap. In this work, enzymatic approach was investigated to increase the colloidal stability of CNRL by using different grades and amounts of enzymes. The enzymes were tested with 2 grades of CNRL, which are the high-ammonia latex (HA latex) and low-ammonia latex (LA latex). We found that the MST of LA latex treated with 0.004% and 0.04% of Lipex reach the acceptable value (at least 600 sec.) within 14 and 10 days, respectively. In case of HA latex, the MST reached the acceptable value faster than that of LA latex (within 10 and 3 days at amount 0.004% and 0.04% of Lipex, respectively) while, the MST of commercial laurate-treated latex only increased slightly and could not pass the acceptable value after 31 days. In addition, the use of enzyme instead of laurate soap could reduce the use of ammonia in CNRL production.

Deformation mechanisms of sub-micrometer thermoplastic vulcanizates obtained by reaction-induced phase separation of miscible poly(ε-caprolactone)/dimethacrylate systems.

The micromechanical deformation mechanisms of sub-μm thermoplastic vulcanizates (TPVs) based on poly(ε-caprolactone) (PCL) and cross-linked methacrylate rubbers were studied by time-resolved small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) measurements in order to better understand the underlying deformation mechanisms responsible for the high elongation at break and good elastic recovery of sub-μm TPVs. It is demonstrated that, in contrast to neat PCL, the interlamellar void formation in the PCL matrix and subsequent coalescence of voids is suppressed by the presence of the rubber (nano)particles in these TPVs. The deformation of the TPVs under tensile conditions is dominated by yielding of the PCL matrix, which is initially localized at the equatorial regions of the rubber particles and progresses towards the polar regions at higher strains. Re-ordering of the crystal structures is both time and stress dependent, and stress relaxation of the TPV under tension is primarily governed by the break-up of the crystal lamellae at the equatorial regions of the rubber particles. This study demonstrates that the rubber particle size as well as chemical grafting of thermoplastic polymer chains onto the surface of cross-linked rubber particles are important parameters to control the mechanical deformation behavior of TPVs.

Identification and subcellular localization analysis of two rubber elongation factor isoforms on Hevea brasiliensis rubber particles

Rubber elongation factor (REF) is the most abundant protein found on the rubber particles or latex from Hevea brasiliensis (the Para rubber tree) and is considered to play important roles in natural rubber (cis-polyisoprene) biosynthesis. 16 BAC (benzyldimethyl-n-hexadecylammonium chloride)/SDS-PAGE separations and mass spectrometric identification had revealed that two REF isoforms shared similar amino acid sequences and common C-terminal sequences. In this study, the gene sequences encoding these two REF isoforms (one is 23.6 kDa in size with 222 amino acid residues and the other is 27.3 kDa in size with 258 amino acid residues) were obtained. Their proteins were relatively enriched by sequential extraction of the rubber particle proteins and separated by 16 BAC/SDS-PAGE. The localization of these isoforms on the surfaces of rubber particles was further verified by western blotting and immunogold electron microscopy, which demonstrated that these two REF isoforms are mainly located on the surfaces of larger rubber particles and that they bind more tightly to rubber particles than the most abundant REF and SRPP (small rubber particle protein).

The rubber tree genome reveals new insights into rubber production and species adaptation.

The Para rubber tree (Hevea brasiliensis) is an economically important tropical tree species that produces natural rubber, an essential industrial raw material. Here we present a high-quality genome assembly of this species (1.37 Gb, scaffold N50 = 1.28 Mb) that covers 93.8% of the genome (1.47 Gb) and harbours 43,792 predicted protein-coding genes. A striking expansion of the REF/SRPP (rubber elongation factor/small rubber particle protein) gene family and its divergence into several laticifer-specific isoforms seem crucial for rubber biosynthesis. The REF/SRPP family has isoforms with sizes similar to or larger than SRPP1 (204 amino acids) in 17 other plants examined, but no isoforms with similar sizes to REF1 (138 amino acids), the predominant molecular variant. A pivotal point in Hevea evolution was the emergence of REF1, which is located on the surface of large rubber particles that account for 93% of rubber in the latex (despite constituting only 6% of total rubber particles, large and small). The stringent control of ethylene synthesis under active ethylene signalling and response in laticifers resolves a longstanding mystery of ethylene stimulation in rubber production. Our study, which includes the re-sequencing of five other Hevea cultivars and extensive RNA-seq data, provides a valuable resource for functional genomics and tools for breeding elite Hevea cultivars.

Micromorphological characterization and label-free quantitation of small rubber particle protein in natural rubber latex

Commercial natural rubber is traditionally supplied by Hevea brasiliensis, but now there is a big energy problem because of the limited resource and increasing demand. Intensive study of key rubber-related substances is urgently needed for further research of in vitro biosynthesis of natural rubber. Natural rubber is biosynthesized on the surface of rubber particles. A membrane protein called small rubber particle protein (SRPP) is a key protein associated closely with rubber biosynthesis; however, SRPP in different plants has been only qualitatively studied, and there are no quantitative reports so far. In this work, H. brasiliensis was chosen as a model plant. The microscopic distribution of SRPP on the rubber particles during the washing process was investigated by transmission electron microscopy–immunogold labeling. A label-free surface plasmon resonance (SPR) immunosensor was developed to quantify SRPP in H. brasiliensis for the first time. The immunosensor was then used to rapidly detect and analyze SRPP in dandelions and prickly lettuce latex samples. The label-free SPR immunosensor can be a desirable tool for rapid quantitation of the membrane protein SRPP, with excellent assay efficiency, high sensitivity, and high specificity. The method lays the foundation for further study of the functional relationship between SRPP and natural rubber content.

A rubber transferase activator is necessary for natural rubber biosynthesis in dandelion

High-molecular-mass natural rubber is a valuable plant-derived poly(cis-1,4-isoprene) with many industrial and medical applications. It is synthesized by a rubber cis-prenyltransferase (CPT) complex on the surface of rubber particles in specialized latex-producing cells known as laticifers. Here we show that Taraxacum brevicorniculatum rubber transferase activator (TbRTA), a dandelion homologue of the human Nogo-B receptor, is an essential component of the rubber transferase complex which interacts with rubber CPTs on the surface of rubber particles. The knockdown of TbRTA by RNA interference eliminated rubber biosynthesis, without affecting dolichol accumulation or protein glycosylation in the latex. We also found that TbRTA is localized on the endoplasmic reticulum membrane, supporting the current favoured model of rubber particle biogenesis. We therefore propose that TbRTA acts as a rubber CPT-binding protein that is necessary for the formation of an active rubber transferase complex. Natural rubber is composed of extremely long polymers of isoprene. In dandelion, a potential alternative source of latex for industry, a rubber transferase activator, homologous to the human Nogo-B receptor, is necessary for this synthesis.

Identification of a Taraxacum brevicorniculatum rubber elongation factor protein that is localized on rubber particles and promotes rubber biosynthesis.

Two protein families required for rubber biosynthesis in Taraxacum brevicorniculatum have recently been characterized, namely the cis-prenyltransferases (TbCPTs) and the small rubber particle proteins (TbSRPPs). The latter were shown to be the most abundant proteins on rubber particles, where rubber biosynthesis takes place. Here we identified a protein designated T.brevicorniculatum rubber elongation factor (TbREF) by using mass spectrometry to analyze rubber particle proteins. TbREF is homologous to the TbSRPPs but has a molecular mass that is atypical for the family. The promoter was shown to be active in laticifers, and the protein itself was localized on the rubber particle surface. In TbREF-silenced plants generated by RNA interference, the rubber content was significantly reduced, correlating with lower TbCPT protein levels and less TbCPT activity in the latex. However, the molecular mass of the rubber was not affected by TbREF silencing. The colloidal stability of rubber particles isolated from TbREF-silenced plants was also unchanged. This was not surprising because TbREF depletion did not affect the abundance of TbSRPPs, which are required for rubber particle stability. Our findings suggest that TbREF is an important component of the rubber biosynthesis machinery in T.brevicorniculatum, and may play a role in rubber particle biogenesis and influence rubber production.

Structural Characterization of Natural Rubber Recent Research Advancements

The micro-structure of the surface of Hevea brasiliensis latex particles has been found by the means of atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cryogenic transmission electron microscopy (cryo-TEM), and electrokinetics over a broad range of KNO3electrolyte concentrations (4-300 mM) and pH values (1-8). Based on the atomic force microscopy analysis of the fresh natural rubber latex, it could be estimated that the protein-lipid layer is covered with the rubber particles. The molecules in the particle were labeled with fluorescent Rhodamine (RB), and were monitored by CLSM. SEM and TEM were used to observe the surface of fresh natural rubber particles and were dyed by osmium tetroxide. Fourier Transform Infrared Spectroscopy (FTIR) has been used to characterize the nitrogenous groups in natural rubber and deproteinized natural rubber (DPNR). The FTIR and1H-NMR analysis of phosphatase-treated DPNR confirmed that the presence of mono- and diphosphate terminations without phospholipids was also unlikely owing to the presence of a methylene proton signal of an isoprene unit linked to mono- and diphosphate groups. The , [η] and Higgins’ k’ of DPNR decreased after being treated with lipase.