Stability Of Latex Research Articles

Optimization Study of a High-Efficiency Preservative for Ammonia-Free Concentrated Natural Rubber Latex

Ammonia is commonly used as a preservative in the production of concentrated natural rubber latex (CNRL) and latex products; however, it poses a serious risk to human health and the environment. In this study, we investigated a thioacetamide derivative (TD) as a preservative of ammonia-free CNRL and the optimization of a stabilization system comprising potassium hydroxide (KOH), lauric acid (LA), and sodium dodecyl sulfate (SDS) to enhance its preservation effect. The results revealed that an optimal amount of TD (0.03%) can effectively maintain the stability of CNRL, inhibit the increase in volatile fatty acid number (VFA number), maintain stable viscosity values, and improve the mechanical stability time (MST). However, increasing the TD dosage results in an increase in both the viscosity and VFA number and a decrease in MST. KOH was used to regulate the pH value of CNRL. It was also found that it can enhance considerably the mechanical properties of CNRL dry films and accelerates the vulcanization of vulcanized film; however, an excessive amount causes latex thickening. LA proved essential for improving the MST and reducing latex viscosity, thereby substantially enhancing the stability and processability of pre-vulcanized latex, but an excessive amount is detrimental to the curing speed and final mechanical strength. SDS can rapidly improve the MST and reduce the viscosity, but it negatively affects the surface molding of dry rubber films. In conclusion, KOH, LA, and SDS at appropriate dosages play a balancing and complementary role in the preparation of ammonia-free CNRL. Upon analyzing diverse performance metrics of CNRL, it has been determined that the optimal TD dosage ranges from 0.02 to 0.03% for maximum efficacy. The KOH dosage should be maintained within 0.1–0.15% to achieve the most favorable outcome, while the LA dosage is advisable to be kept between 0.06 and 0.1%.

Colloidal stability of styrene-acrylic latexes using anionic and nonionic polymerizable surfactants by seeded emulsion polymerization for waterborne paints

Colloidal stability of styrene-acrylic latexes using anionic and nonionic polymerizable surfactants by seeded emulsion polymerization for waterborne paints

Comparative Study of Interfacial and Conventional Techniques for Nanosilica Incorporation in Natural Rubber Latex-Based Composites with Varied TEOS Content

This study investigates the preparation of natural rubber latex (NRL) composites with varying nanosilica contents of 5, 15, 30, and 45 phr, using both interfacial and conventional mixing techniques. Analysis focused on viscosity, plasticity, morphology, and FTIR spectra to evaluate the impact of these methods on composite properties. The interfacial techniquemaintained lower viscosity values, indicating better latex stability, and achieved higher silica yields and conversion rates (94 - 99%) at elevated TEOS contents. Plasticity analysis revealed that the interfacial method produced more uniform and stable plasticity values, suggesting improved resistance to oxidation and enhanced mechanical properties. SEM and FTIR analyses confirmed superior dispersion with the interfacial technique, especially at higher silica contents. These findings highlight the efficacy of the interfacial technique in optimizing the properties of NRL composites, making it a promising approach for advanced material applications. HIGHLIGHTS Analysis of interfacial and conventional mixing techniques reveals their impact on NRL composite properties, demonstrating the interfacial method's superior stability, silica dispersion, and enhanced mechanical properties. The interfacial method maintains lower, stable viscosity, prevents latex destabilization, achieves higher silica yields, and ensures economic and sustainable production of high-quality composites. SEM and FTIR analyses confirm better silica dispersion and morphology with the interfacial method, enhancing composite performance, durability, and informing industrial applications and future research directions. GRAPHICAL ABSTRACT

Preparation and properties of fluorinated VAc-VeoVa10 latex emulsified with allyl nonyl phenoxy propyl alcohol polyoxyethylene ether ammonium sulphate

Purpose The traditional VeoVa10-VAc copolymer latex, which prepared via the emulsion polymerization of the mixed monomers of VAc and VeoVa10, has the poor water resistance and thermal stability because of the migration of the conventional emulsifier molecules and the low bond energy of C-C bond. The purpose of this work is that the fluorinated monomer is used to modify the latex. The film of the resultant latex has the C-F bond with high bond energy and low surface energy, which can effectively improve the heat resistance and water resistance of the resultant film. In addition, the reactive emulsifier is used to replace the conventional emulsifier. The drawbacks of the conventional emulsifier molecules migrate and desorb can be avoided when the polymer latex is stored, thereby also improving the water resistance. Design/methodology/approach The modified VAc-VeoVa10 latex has been successfully synthesized via the semi-continuous seeded emulsion polymerization, which VAc and VeoVa10 is used as the main monomers and HFMA was used as the functional monomer. KPS and reactive surfactants of SE-10 were used as the initiator and emulsifier, respectively. The structure of resultant latex film was characterized by Fourier transform infrared spectroscopy (FTIR). The latex films were tested by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA). The particle size and its distribution of the latex were measured by the nano particle size analyzer. Findings The factors that had an influence on the properties of the latex and the film were investigated in detail. The stability of the resultant latex is good. The average particles of the latex and its distribution are small and uniform, respectively. In comparison with the conventional latex film, the thermal stability and hydrophobicity of the resultant latex film are improved obviously. Practical implications The resultant latex can be used in both the waterborne interior and exterior wall coatings, pickering stabilized waterborne polymer dispersions, polymer powders, environmentally friendly polymer-modified waterproof mortar and other fields, which can be satisfied with the high demand of thermal stability and hydrophobicity. Originality/value The modification of poly (VAc-VeoVa10) by reactive surfactant and fluorinated monomer is seldom reported. In this study, the fluorinated poly (VAC-VeoVa) latex is prepared via the reactive surfactants, which VAc and VeoVa10 is used as the main monomers and hexafluorobutyl methacrylate is used as the functional monomer. Potassium persulfate (KPS) and allyl nonyl phenoxy propyl alcohol polyoxyethylene ether ammonium sulfate are used as the initiator and emulsifier, respectively.

Preparation and Characterization of Chloroprene Latexes Modified with Vinyl-POSS.

Water-based chloroprene latex is a solvent-free, environmentally friendly adhesive. Currently, its market demand is growing rapidly. However, there are problems such as a lack of heat resistance and poor mechanical properties, which limit its application. The introduction of vinyl-POSS (OVS) into the resin structure can effectively improve the thermal stability of chloroprene adhesives. In this paper, modified waterborne chloroprene latex was prepared by copolymerization of methyl methacrylate and OVS with chloroprene latex. The results showed that vinyl-POSS was successfully grafted onto the main chain of the waterborne chloroprene latex, and the modified waterborne chloroprene latex had good storage stability. With the increase in vinyl-POSS, the tensile strength of the chloroprene latex firstly increased and then decreased, the tensile property (peel strength of 20.2 kgf) was maintained well at a high temperature (100 °C), and the thermal stability of the chloroprene latex was improved. When the addition amount was 4%, the comprehensive mechanical properties were their best. This study provides a new idea for the construction of a new and efficient waterborne chloroprene latex system and provides more fields for the practical application of waterborne chloroprene latex. This newly developed vinyl-POSS modified chloroprene latex has great application potential for use in home furniture, bags, and seat cushions.

Improving the performance of polyacrylate latex binders for water-based inks through the application of reactive emulsifiers and nanosized zinc oxide

The poor redissolution and low ethanol resistance stability of room temperature self-cross-linking polyacrylate latexes (RTSPLs) made from conventional emulsifiers are the main obstacles for their industrial application in water-based inks. To address these issues, in this study, anionic SR-10 (allyloxy polyoxyethylene ammonium sulfate) /nonionic ER-10 (allyloxy fatty alcohol polyoxyethylene ether) dual-reactive composite emulsifier is developed to replace the conventional 2A1 (sodium dodecyl diphenyl ether disulfonate) /TX-30 (alkyl phenol polyoxyethylene ether) non-reactive composite emulsifier for the synthesis of polyacrylate latexes, and a certain mass of nanosized zinc oxide (ZnO) was added into as-prepared latexes as an ionic cross-linking agent to partially replace the cross-linking monomer of diacetone acrylamide (DAAM). Properties of the latexes and the latex films, with emphasis on redissolution, stability against ethanol, and adhesion on biaxially oriented polypropylene (BOPP) and polyethylene (PE) substrates, were evaluated to study the effect of the reactive emulsifiers and the nanosized ZnO. The application of the reactive composite emulsifier eliminates the disadvantages associated with the desorption from the latex particles and migration during film formation of the non-reactive emulsifier, thus improving the ethanol resistance stability of latexes and adhesion of their inks on BOPP substrate. The introduction of a certain amount of nanosized ZnO to replace DAAM in equimass amounts improves the redissolution but reduces the cross-linking density and water resistance of the latex film. Surprisingly, the addition of nanosized ZnO substantially improves the ethanol stability of latexes. When ZnO replaces DAAM, accounting for approximately 1 wt% of the total monomers, not only the prepared latex exhibits excellent alcohol dilution stability, but also the latex film has a relatively high cross-linking density, good redissolution, and good comprehensive properties. These findings provide an effective, yet simple way to balance the redissolution and high cross-linking degree of latex films while ensuring that the latexes have good ethanol resistance stability.

The Interplay of Protein Hydrolysis and Ammonia in the Stability of Hevea Rubber Latex during Storage.

Natural rubber (NR) latex derived from Hevea brasiliensis is a complex colloid comprising mainly rubber hydrocarbons (latex particles) and a multitude of minor non-rubber constituents such as non-rubber particles, proteins, lipids, carbohydrates, and soluble organic and inorganic substances. NR latex is susceptible to enzymatic attack after it leaves the trees. It is usually preserved with ammonia and, to a lesser extent, with other preservatives to enhance its colloidal stability during storage. Despite numerous studies in the literature on the influence of rubber proteins on NR latex stability, issues regarding the effect of protein hydrolysis in the presence of ammonia on latex stability during storage are still far from resolved. The present work aims to elucidate the interplay between protein hydrolysis and ammoniation in NR latex stability. Both high- and low-ammonia (with a secondary preservative) NR latexes were used to monitor the changes in their protein compositions during storage. High-ammonia (FNR-A) latex preserved with 0.6% (v/v) ammonia, a low 0.1% ammonia/TMTD/ZnO (FNR-TZ) latex, and a deproteinized NR (PDNR) latex were labeled with fluorescence agents and observed using confocal laser scanning microscopy to determine their protein composition. Protein hydrolysis was confirmed via sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results revealed that protein hydrolysis increased with the storage duration. The change in protein composition accompanying hydrolysis also allows the spatial distribution of allergenic proteins to be estimated in the latex. Concurrently, the latex stability increased with the storage duration, as measured by the latex's mechanical stability time (MST) and the zeta potential of the latex particles. As monitored by AFM, the surface roughness of the NR latex film increased markedly during extended storage compared with that of the DPNR latex, which remained smooth. These results underscore the pivotal role of ammonia in bolstering NR latex stability brought on by protein hydrolysis, which greatly impacts latex film's formation behavior. NR latex stability underpins the quality of latex-dipped goods during manufacturing, particularly those for medical gloves.

Colloids with reversible stability switched by tris[2‐(dimethylamino)ethyl]amine

AbstractThe addition of salt can irreversibly disrupt the stability of both emulsions and polymer latex. The reversible conversion of amines into organic ammonium salts can be induced by CO2 stimulation, thereby enabling the switching of colloids. The switchable amine, tris[2‐(dimethylamino)ethyl]amine (Me6TRAN), was selected for the study. The electrical conductivity of an aqueous solution of Me6TRAN is modulated by the introduction and removal of CO2. The critical micelle concentration of sodium dodecyl benzene sulfonate (SDBS) was observed to decrease from 1.0 × 10−3 to 5.0 × 10−4 M upon the introduction of Me6TRAN, as confirmed by surface tension measurements conducted under CO2. The emulsion of crude oil, which comprised of SDBS and Me6TRAN, underwent reversible destruction and restoration upon exposure to CO2 and N2. The PMMA latex exhibited a clear phase separation subsequent to CO2 sparging, but attained homogeneity upon N2 sparging. This study is anticipated to introduce a novel avenue for emulsion or polymer latex that can undergo demulsification and emulsification through CO2 stimulation.

Synthesis and properties study of alkali soluble resin fortified polyacrylate latex

AbstractLatex films with high heat resistance tend to have higher Tg and the emulsion minimum film formation temperature (MFFT) is higher. Higher MFFT latexes do not produce continuous coherent films at low temperatures during application. Consequently, in order to solve the paradoxical problem of obtaining latex films with high Tg at low emulsion MFFT, a series of alkali soluble resin (ASR) stabilized latexes were synthesized in this study using a semi‐continuous pre‐emulsification polymerization process. The microstructure of latex particles, polymerization stability, composition and properties of latex films were characterized and tested by ATR‐FTIR, TEM, ZETA potential analyzer, DSC, orthomorphic metallographic microscope, and gloss tester. The results show that the addition of ASR reduces the content of coagulum during polymerization and significantly increases the number of latex particles. The high Tg ASR also induces the formation of a microphase separation structure with a dual glass transition in the latex film, which improves heat resistance. Additionally, hydroplasticized ASR reduces emulsion MFFT, improves latex film flatness, and enhances its glossiness. The introduction of ASR acts as a dual role of synergy with conventional ionic surfactants during synthesis to increase the stability of composite latexes and with polyacrylate (PA) in application to enhance its properties.

Deproteinization of Natural Rubber Latex and Its Pale-Colored Thin Films

The non-rubber components present in natural rubber latex can contribute to the dark color of dried films and may cause allergic reactions. This project aimed to develop light-color rubber films with minimal protein contamination. Various additives were incorporated, and a leaching procedure was implemented to address this issue. The evaluation focused on protein content, color changes, and swelling properties of thin natural rubber films. Texapon N70 proved effective as both a latex stabilizer and leaching agent, while Uniphen P-23 served as a preservative. The combined use of these additives facilitated the removal of soluble serum through appropriate incubation, leaching, and centrifugation processes. The introduction of additional centrifugation cycles improved deproteinization and color reduction; however, it led to a loss of rubber mass and an increase in manufacturing costs. Increasing the amount of Texapon N70 and introducing alkali potassium hydroxide (KOH) further enhanced the efficiency of deproteinization and color reduction. The optimal conditions determined in this investigation were as follows: 0.5% w/w Texapon N70, 0.5% w/w KOH, 1% w/w Uniphen P-23, a 60-min incubation period, and a single leaching cycle with distilled water. These conditions resulted in a 90.57 ± 1.20% decrease in protein contamination and a color change (ΔE) of 433.69 ± 20.23. This successful condition can be replicated and scaled up for further applications.

Correction to: Effect of lipids on the stability of natural rubber latex and tensile properties of its films

Correction to: Effect of lipids on the stability of natural rubber latex and tensile properties of its films

Environmentally safe preservation and stabilization of natural rubber latex in an acidic environment

AbstractNatural rubber is an indispensable raw material that supplies about half of the world's rubber consumption. The latex that is extracted from the trees is composed of polyisoprene rubber, proteins, sugars, amino acids, lipids, and minerals. When the liquid latex emanates from the trees, it comes into contact with bacteria that cause it to decompose and coagulate. To hinder the decomposition and destabilization process, ammonia and other environmental and health hazard chemicals are added to the latex. The addition of these chemicals affects the health of plantation and rubber industry workers and results in residues that are contaminated with these chemicals, which require that processing facility effluents undergo costly treatment processes. Here, we present two novel liquid latex preservation and stabilization methods in an acid medium free of ammonia or other dangerous chemicals. The first method uses dodecyl benzene sulfonic acid to both stabilise and preserve the liquid latex, and the second uses ethoxylated tridecyl alcohol to stabilise and hydrofluoric acid to preserve the colloidal suspension. Both formulations result in rubber with superior mechanical properties, that is safe for the rubber plantation and industry workers, and with residues that no longer adversely affect the environment.

The Stability and Properties of Polystyrene/Kaolinite Nanocomposites during Synthesis via Emulsion Polymerization.

The aim of this work was to study the stability and morphological properties of polystyrene latex containing kaolinite as a filler during the process of synthesis of nanocomposites viaemulsion polymerization. Nanocomposites with 1, 3, and 5 wt% of kaolinite were prepared. Latexes with 1 to 3 wt% of kaolinite were stable during the polymerization reaction. Hydrodynamic diameters of 93.68 and 82.11 nm were found for latexes with 1 and 3 wt% of kaolinite, respectively. The quantities of 1 to 3 wt% of kaolinite added during the reaction did not influence the reaction conversion curves or the number of particles. X-ray diffraction (XRD) and unconventional techniques of scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) showed the presence of exfoliated and intercalated structures of the kaolinite.

Monitoring of Emulsion Polymerization in the Presence of Ionic Liquids Using NIR Spectroscopy

AbstractMuch effort has been done toward the development of new emulsifiers able to improve the latex stability. In this sense, ionic liquids based on imidazolium constitute a new category of stabilizer in study. Moreover, the near infrared (NIR) spectroscopy has been extensively investigated as a tool to follow the properties of polymerization reactions. In this study different ionic liquids are investigated as emulsifiers during the emulsion homopolymerization of the styrene and methyl methacrylate. A quantitative analysis method is developed to determine the properties of latex based on the joint use of the NIR spectra and partial least squares regression (PLS). Kinetic results indicate that the latex properties are greatly influenced by the type of ionic liquid. The current work shows that the NIR spectrophotometer can be successfully used for monitoring of the latex properties, enabling to track the polymerization dynamics even in the presence of ionic liquids.

Effects of latex and thickener polarities on rheology and phase stability of latex–HEUR mixtures

Effects of latex and thickener polarities on rheology and phase stability of latex–HEUR mixtures

Visible label-free detection of bacterial DNA using flocculation of sterically stabilised cationic latexes.

The current gold standard diagnostic for bacterial infections is the use of culture, which can be time consuming and can take up to five days for results to be reported. There is therefore an unmet clinical need for a rapid and label free alternative. This paper demonstrates a method of detecting the presence of amplified DNA from bacterial samples using a sterically-stabilised, cationic polymer latex and widely available equipment, providing an accessible alternative DNA detection technique. If DNA is present in a sample, successful amplification by polymerase chain-reaction (PCR) results in the amplified DNA inducing flocculation of the polymer latex followed by rapid sedimentation. This results in a visible and obvious change from a milky-white dispersion to a precipitated latex with a colourless and transparent supernatant, thus giving a clear visual indication of the presence or absence of amplified DNA. Specifically, the response of four polymer latexes with different morphologies to the addition of amplified bacterial DNA was investigated. Cationic latexes flocculated rapidly whereas non-ionic and anionic latexes did not, as judged by eye, disc centrifuge photosedimentometry (DCP), and UV-visible spectrophotometry. The stability of several cationic latexes with different morphologies in typical PCR reagents was investigated. It was found that unwanted flocculation occurred for a latex with a non-ionic core and a cationic corona (poly[2-vinyl pyridine-b-benzyl methacrylate], prepared by polymerisation-induced self-assembly) whereas a ∼700 nm PEGMA-stabilised P2VP latex (non-ionic stabiliser, cationic core), prepared by emulsion polymerisation remained stable. The sensitivity and rate of sedimentation of the PEGMA-stabilised P2VP latex was demonstrated by varying the sequence length and concentration of amplified DNA from Pseudomonas aeruginosa using universal bacterial primers. DNA concentrations as low as 0.78 ng μl-1 could readily be detected within 30 minutes from the addition of amplified DNA to the latex. Furthermore, the specificity of this method was demonstrated by showing a negative result occurs (no flocculation of the latex) when PCR product from a fungal (Candida albicans) sample using bacterial primers was added to the latex.

PROPERTIES OF AMMONIA-FREE CONCENTRATED NR LATEX PRESERVED WITH N,N′-METHYLENEBISMORPHOLINE

ABSTRACT The NR latex (NRL) industry contributes to ammonia pollution, a problem that is difficult to solve. To address this issue, N,N-methylenebismorpholine (MBM) was used to prepare ammonia-free concentrated NRL (CNRL). The effect of MBM on the preservation and properties of CNRL was studied through comparison with high-ammonia (HA) CNRL. Results showed that MBM had an excellent preservation effect on ammonia-free CNRL. When the MBM dosage exceeded 0.35%, the volatile fatty acid value of CNRL was relatively stable and was consistently less than 0.06 over 180 days of storage. The prepared ammonia-free CNRL had lower viscosity and pH, and its mechanical stability test (MST) was moderate. The control results of the stabilization system showed that sodium dodecyl sulfate can significantly reduce the viscosity and improve the MST of the ammonia-free CNRL. KOH can significantly improve the pH and thermal stability of latex, but has little effect on improving MST. The ammonia-free CNRL had a lower pH after prevulcanization, but higher MST than the HA latex. The viscosity of the ammonia-free prevulcanized latex increased rapidly. The physico-mechanical properties of the vulcanizate films were slightly different from those of the HA latex samples. In addition, the infrared spectrum of the ammonia-free CNRL dry film was basically consistent with that of HA latex dry film. The thermal degradation curve and characteristic temperature of the ammonia-free CNRL dry film were basically the same as those of the HA-preserved film. Biosafety tests showed that the cytotoxicity of the MBM-preserved, ammonia-free CNRL dry film was slightly higher than that of the HA latex film. However, both films did not irritate the skin. All of these results illustrate that MBM has an excellent preservation effect on CNRL and the prepared ammonia-free CNRL has good processability, environmental protection, and safety.

3-D flower-like templated LDH-rGO as coating additive for flame retardant products

Construction of multi-component heterostructures as a flame retardant reinforcer within a polymer is a favorable option to realize the synergistic effects between different types of reinforcers. However, it is difficult to improve polymer flame retardance as the poor compatibility of retardants with polymer matrix can lead to low dispersion. Herein, 3-D flower-like templated layered double hydroxides (LDH) and graphene (rGO) were prepared on the surface of a caprolactam-modified casein micelle template for integration with casein latex based on a blending-casting method. Temp@LDH-rGO hardly affected the stability of the casein-based latex, as its casein-based composite latex was used as a leather surface coating. The limiting oxygen index of finished leather increased up to 27.4% when casein-based 4% Temp@LDH-rGO composite latex was applied for leather finishing. In contrast, its heat release rate and smoke production rate were lowered to 55.686 kW/m2 and 2.239 m−2 s−1, respectively. According to the combustion analysis, the leather samples finished by casein-based Temp@LDH-rGO latex exhibited significant improvement in flame retardant and smoke suppression performance. The casein-based Temp@LDH-rGO composite latex has thus been demonstrated as a highly effective option for functional coatings in diverse fields (e.g., automobile interior decoration, furniture manufacturing, and firefighting equipment).

Effect of calcium nitrate and a hydrophobically modified polymeric surfactant on the stability of natural rubber latex

Effect of calcium nitrate and a hydrophobically modified polymeric surfactant on the stability of natural rubber latex

Influence of Metal Oxide Nanoparticles as Antimicrobial Additives Embedded in Waterborne Coating Binders Based on Self-Crosslinking Acrylic Latex

This article deals with the simple preparation of environmentally friendly acrylic latex binders, which are functionalized with nanoparticles of metal oxides, namely MgO, ZnO, La2O3 and combinations of MgO and ZnO, serving as functional components to achieve antimicrobial properties, but also to improve physical–mechanical properties and chemical resilience. The incorporation of uncoated powder nanoparticles was performed during the synthesis, using the two-stage semi-continuous emulsion radical polymerization technique, to obtain latexes containing 0.5%–1.3% nanoparticles relative to the polymer content. Changes in latex performance due to nanoparticles were compared from the point of view of the type and concentration of metal oxide nanoparticles in latex. The results of the tests showed that all types of nanoparticles showed very promising properties, while with increasing concentration of nanoparticles there was an improvement in properties. The nanoparticles in latex provided interfacially crosslinked transparent smooth coating films with high gloss and good physical–mechanical properties. Latexes containing the highest concentration of nanoparticles provided coatings with significant antimicrobial activity against all tested bacterial and fungal strains, but also in-can preservative stability of liquid latex. Furthermore, the coatings were resistant to solvents, and in addition, latexes with MgO nanoparticles showed a significant decrease in the minimum film-forming temperature, and latex with a concentration of about 1.3% MgO did not show any flash corrosion under the coating film cast on a steel substrate. The latexes containing MgO and La2O3 nanoparticles provided coatings that were very resistant to water bleaching.