Latex Research Articles

Effect of silica particle size and coating by natural latex on properties of styrene‐butadiene rubber/carbon black/silica composites

AbstractSilica is a renewable resource that has become the primary filler for the rubber used in eco‐friendly tires. However, silica tends to agglomerate in the rubber matrix, particularly, micro‐ and nano‐scale silica, which limits its application. When ordinary‐particle‐size silica with low cost and high stacking density is modified using appropriate methods, high dispersion in rubber and good performance can be achieved with common processing equipment, which has significant engineering application value. In this study, silica particles with different sizes (nano‐scale, 19 and 45 μm) were treated with a 3‐mercaptopropyltriethoxysilane coupling agent (KH580). Subsequently, the silica with the ordinary particle size of 300 mesh (45 μm) was coated with natural latex (NL), and the mechanical properties of the modified silica‐filled styrene‐butadiene rubber (SBR)/carbon black (CB) compounds were investigated. The results revealed that the mechanical properties of the NL‐coated 45 μm silica‐filled composite improved significantly, particularly, in the area of tear strength and elongation at break, the composite properties were improved by 17.1% and 118.2%, respectively. Excellent performance over composites filled with coupling agent‐treated micron‐ and nanoscale silica. Enhancing the surface modification of silica through latex coating provides a means to improve the efficiency of industrial production and reduce costs.Highlights The low‐fine silica treated with KH580 has good dispersibility. Improved mechanical compatibility of NL‐coated silica with rubber. Improvement in strain performance of composites after NL coated with silica. The effect of silica dispersion on composite properties is greater than the effect of particle size. Industrial silica can be successfully addressed, paving the way for extensive utilization.

Development of a large diameter invitro flow loop thrombogenicity test system.

To accommodate a wider range of medical device sizes, a larger invitro flow loop thrombogenicity test system using 9.5 -mm inner diameter (ID) tubing was developed and evaluated based on our previously established 6.4 -mm ID tubing system. Four cardiopulmonary bypass roller pumps were used concurrently to drive four flow loops during testing. To ensure that each pump produced a consistent thrombogenic response for the same material under the same test conditions, a novel dynamic roller occlusion setting method was applied. Five materials with varying thrombogenic potentials were tested: polytetrafluoroethylene (PTFE), silicone, 3D-printed nylon, latex, and nitrile rubber (BUNA). Day-old bovine blood was heparinized to a donor-specific concentration and recirculated through the flow loops containing test materials at 20 rpm for 1 h at room temperature. Material thrombogenicity was characterized by measuring the thrombus surface coverage, thrombus weight, and platelet (PLT) count reduction. The larger tubing system can differentiate thrombogenic materials (latex, BUNA) from the thromboresistant PTFE material. Additionally, silicone and the 3D-printed nylon exhibited an intermediate thrombogenic response with significantly less thrombus surface coverage and PLT count reduction than latex and BUNA but more thrombus surface coverage than PTFE (p < 0.05). The 9.5 -mm ID test system can effectively differentiate materials of varying thrombogenic potentials when appropriate pump occlusion settings and donor-specific anticoagulation are used. This system is being assessed in an interlaboratory study to develop standardized best practices for performing invitro dynamic thrombogenicity testing of medical devices and materials.

Properties of vulcanised concentrated skim natural rubber latex dipped film

Properties of vulcanised concentrated skim natural rubber latex dipped film

Flame Retardancy and Properties of Thermoplastic Vulcanizates from Dibutyl Phosphate-Bound Natural Rubber/Ethylene Vinyl Acetate Blends

ABSTRACT Dibutyl phosphate-bound epoxidized natural rubber (DBNR) was synthesized from natural rubber latex via epoxidation using a 20 mol% intermediate. Successful formation of epoxidized natural rubber (ENR-20) and DBNR was confirmed by FTIR analysis. Thermoplastic vulcanizates (TPVs) were prepared by dynamically vulcanizing blends of DBNR and ethylene-vinyl acetate copolymer (EVA). The 50/50 DBNR/EVA TPV exhibited higher mixing torque during vulcanization, indicative of increased shear stress, shear rate, and tensile strength. This was attributed to finer dispersion of vulcanized rubber domains in the EVA matrix, leading to enhanced interfacial adhesion. Elongation at break decreased with increasing EVA content, while hardness and tension set increased, suggesting reduced elasticity at higher EVA proportions. Under heat aging, TPVs experienced degradation of mechanical properties and increased tension set, indicating loss of elastomeric behavior. Significantly, DBNR exhibited a low burning rate of 0.2 mm/s, imparting inherent flame retardancy. The burning rate of DBNR/EVA TPVs decreased with increasing DBNR content, demonstrating improved flame retardancy. Overall, DBNR/EVA TPVs exhibited favorable mechanical properties and flame retardancy, making them suitable for applications requiring flame-retardant elastomeric materials.

Automated system for determining particle size by moisture weight loss

An alternative method to determine the average particle size of suspensions, from the loss of moisture as function of the time is presented. Consequently, the novelty of the method consists of determining the particle size through weight loss. According to this definition, these bulk variations are collected, by controlling at the same time, parameters as the relative dampness of the chambers and the temperature of the samples under analysis. Additionally, the data are processed in the time domain and Fourier-analyzed to obtain the average particle size. Statistically, the method was calibrated through the comparison with samples previously characterized by transmission electron microscopy, by using polymer latex dispersed in water with an average particle size of 24, 44, 74 and 105 µm.

Natural aging behavior and lifetime prediction of rubber latex foam with various natural-to-synthetic ratios

Rubber latex foam (RLF) is a low-density, three-dimensional porous material that is susceptible to aging factors such as oxygen, heat, and light, leading to a loss of its excellent performance. This study conducted natural aging tests of the RLF with various proportions. The experimental conditions were divided into two categories: with and without fabric covering to better simulate the actual usage conditions. Subsequently, the performance of the RLF were conducted before and after aging, investigating the natural aging patterns of the RLF, and the influence of fabric covering conditions on aging. The results indicated that RLF with low N/R ratios has better aging resistance, and during natural aging, the N/R ratio did not show a significant relationship with the aging rate of the samples. From a microscopic perspective, samples covered with fabric maintain a more intact porous structure compared to those without fabric covering. In the process of thermo-oxidative aging, all samples underwent oxidation reactions. Finally, using the yellowness index as an evaluation criterion, the storage life of RLF was predicted by the variable activation energy method, and the quality and safety in actual production were further determined.

Starch-based films: Tuning physical properties driven by nanocellulose-natural rubber latex composites

The excessive use of petroleum-based plastic packaging has raised concerns about its environmental impacts, leading to research on sustainable and economically viable biopolymer-based nanocomposites. However, there are still challenges related to the intrinsic characteristics of some biopolymers that differ substantially from conventional polymers, in terms of mechanical properties and water affinity. To address these issues, natural rubber (NR) latex coated with cellulose nanocrystals (CNCs) composites were explored as an effective alternative to tuning up physical properties of biopolymers. The deposition of CNCs on NR surface was innovatively devised through the utilization of the freeze-drying method, employing a green approach that eliminates the need for organic solvents. The NR coated with CNCs was incorporated into the starch matrix, varying the nanofiller mass percentage in the biopolymer (2, 5, and 10 wt%), the NR content in the nanofiller (0, 1, and 5 wt%), and the nanofiller preparation method (liquid nitrogen – N and gradual freezing – F). All starch-based films demonstrated notable transparency to visible light, and the incorporation of CNC/NR from N led to a reduction of 28 % in water vapor transmission rate compared to starch with glycerol, aligning with the filler percentage in the matrix. The addition of CNC/NR contributed to an increase of 76 % in the tensile strength and 53 % in the Young’s modulus of the bionanocomposites compared to starch with glycerol. Notably, the freeze-drying method allowed for the compatibilization of NR with a hydrophilic matrix without compromising the mechanical properties of starch-based bionanocomposites. Furthermore, films containing the CNC/NR nanofillers assisted in delaying the ripening of fresh-cut bananas, in addition to accelerating the biodeterioration of starch-based films. These findings indicate a promising avenue for the development of a new generation of green nanofillers that can be conveniently hydrophobically tailored to suit carbohydrate polymeric matrices.

Neutron and X-ray Scattering Characterization of Silica Nanoparticle-Stabilized Polymer Hybrid Latex Particles.

A robust route to produce poly(methyl methacrylate) (pMMA) hybrid latex particles (radius ∼250 nm) that are selectively "armored" with silica nanoparticles (radius 12.5 nm) through addition of vinyltriethoxysilane was previously shown ( J. Colloid Interface Sci. 2018, 528, 289-300).Depending on synthesis conditions, the extent of nanoparticle attachment could be varied; however, the mechanism behind this attachment during latex growth remained unclear. The dual population of particles present (silica + polymer) means that particle sizing by dynamic light scattering is ambiguous. Furthermore, the low glass transition temperature (Tg) of polymers such as poly(butyl acrylate) (pBA) typically used in film-forming applications for decorative coatings (i.e., paints) means that the hybrid latex particles are too "soft" for robust analysis through atomic force microscopy (AFM) and scanning electron microscopy (SEM). Here, we show that small- and ultrasmall-angle neutron scattering (SANS and USANS), along with complementary data from small-angle X-ray scattering (SAXS), reveals that these armored hybrid latex particles adopt a raspberry-type configuration, supporting their core-shell structure. The number of nanoparticles present on the surface of the hybrid latex can be adjusted by addition of one of a diverse range of alkyl- or perfluoroalkyl-silanes to alter silica nanoparticle hydrophobicity, and quantified through analysis of scattering data. The approach therefore provides a novel, nonperturbative, and in situ method of quantifying nanoparticle attachment to polymer latex particles.

Unraveling the Complexities of Silica Nanoparticle Adsorption onto Polymer Latexes in Pickering Emulsion Polymerization.

Incorporating unmodified silica nanoparticles onto polymer latexes to fabricate aqueous polymer dispersions without relying on electrostatic attraction during the Pickering emulsion polymerization process still faces challenges. For negatively charged silica nanoparticles to successfully adsorb onto polymer latexes, particularly in an anionic initiator emulsion polymerization system, they have remained elusive without the use of auxiliary monomers and cationic initiators. This study investigates various experimental parameters, such as emulsion polymerization temperature, monomer solubility, salt concentration, and cation type, to elucidate the factors influencing the adsorption of unmodified silica nanoparticles in Pickering emulsion polymerization. While poly(methyl methacrylate) (PMMA)/SiO2 hybrid latexes can be obtained under pH conditions of 5-6 and at temperatures of 65 °C or below, the loading rate of silica nanoparticles decreases as the reaction temperature increases, resulting in bare PMMA latexes without silica nanoparticle adsorption at temperatures exceeding 70 °C. Introducing styrene (St) into the monomer mixture with methyl methacrylate in a ratio of up to 10 wt % leads to a gradual decrease in silica nanoparticle loading rate, from 27.3 to 8.2 wt %, attributed to the low solubility of St in water. Furthermore, the presence of sodium ions (Na+) is found to be crucial for silica nanoparticle adsorption onto PMMA latexes, as the sodium ions have a stabilizing effect on both the silica nanoparticles and the silica nanoparticle-armored latexes. These findings highlight the complex nature of Pickering emulsion polymerization in the presence of unmodified silica nanoparticles, demonstrating that the loading rate of silica nanoparticles onto polymer latexes is influenced by various factors. These insights pave the way for developing aqueous polymer dispersions with high silica nanoparticle loading rates onto polymer latexes, which is a desirable trait in the coating industry.

Highly Stable Flexible Organic Electrochemical Transistors with Natural Rubber Latex Additives.

Organic electrochemical transistors (OECTs) have attracted considerable interest in the context of wearable and implantable biosensors due to their remarkable signal amplification combined with seamless integration into biological systems. These properties underlie OECTs' potential utility across a range of bioelectronic applications. One of the main challenges to their practical applications is the mechanical limitation of PEDOT:PSS, the most typical conductive polymer used as a channel layer, when the OECTs are applied to implantable and stretchable bioelectronics. In this work, we address this critical issue by employing natural rubber latex (NRL) as an additive in PEDOT:PSS to improve flexibility and stretchability of the OECT channels. Although the inclusion of NRL leads to a decrease in transconductance, mainly due to a reduced carrier mobility from 0.3 to 0.1 cm2/V·s, the OECTs maintain satisfactory transconductance, exceeding 5 mS. Furthermore, it is demonstrated that the OECTs exhibit excellent mechanical stability while maintaining their performance even after 100 repetitive bending cycles. This work, therefore, suggests that the NRL/PEDOT:PSS composite film can be deployed for wearable/implantable applications, where high mechanical stability is needed. This finding opens up new avenues for practical use of OECTs in more robust and versatile wearable and implantable biosensors.

Facile preparation and characterization of biodegradable and biocompatible UV shielding transdermal patches based on natural rubber latex- dextrin blends

The physico-chemical and biological properties of natural rubber latex (NRL), entailing its biodegradability and biocompatibility, render it a promising material for various biomedical applications. This research explores the facile blending of NRL with dextrin in different compositions to investigate its potential as a prospective UV shielding transdermal patch for biomedical applications. The superior compatibility between the polymers after blending and the improved thermal stability have been established through FTIR, DSC, and TGA examinations, respectively. Optimization of blended polymers for compatibility, wettability, crystallinity, and static mechanical properties has been performed. Morphology characterization conducted via SEM and AFM techniques suggests a uniform morphology for the optimized blend system. The UV shielding ability of the blend has been confirmed by the evaluation of in-vitro UV shielding performance, UV protection factor (UPF), and the superior protection of the optimized system on living cells upon UV irradiation. The observed cell viability, swelling, erosion, porosity, hemocompatibility, and soil degradation properties suggest the NRL-DXT combination for the possible development of high-quality transdermal patches.

Synergistic effects of chitosan and gamma irradiation on enhanced fungal growth inhibition and biodegradability of natural rubber latex film

Developing novel formulations and processes to improve the fungal growth inhibition and biodegradability of NR products has become a major challenge for the scientific community, given the health risks associated with fungi in natural rubber (NR) products and the environmental concerns regarding NR waste. Consequently, this study comprehensively investigated the synergistic effects of chitosan and gamma irradiation on enhancing fungal growth inhibition and biodegradability in natural rubber latex (NRL) films. The research involved incorporating varying chitosan contents (0, 3, 6, or 9 phr) into NRL composites and exposing them to different gamma doses (0, 5, 10, or 15 kGy). The results showed that increasing the chitosan content and the gamma dose improved the ability of the NRL samples to inhibit fungal growth on their surfaces. This was evidenced by the absence of fungal colonies after 7 days of incubation on potato dextrose agar (PDA) plates for NRL samples irradiated at 5–15 kGy with 9 phr of chitosan. This determination was based on isolating fungi from the film surfaces, followed by serial dilution and a viable plate count. The biodegradability tests also revealed that the NRL films irradiated at 15 kGy with 9 phr of chitosan had the highest weight loss, reaching as high as 10.42 ± 0.62 % after soil burial for 8 weeks. However, the results indicated that gamma irradiation on the pristine NRL and chitosan/NRL films did not substantially alter the thermal stabilities, density, morphology, and functional groups of the samples. Lastly, by comparing the tensile properties of all the NRL films to the ASTM D3578-01a standard for examination gloves, the optimum conditions for the NRL films were 5 kGy of gamma irradiation with 9 phr of chitosan. This combination resulted in gloves with sufficient tensile strength and complete fungal growth inhibition.

PEDOT:PSS/XNBR films for low-temperature stretchable electromagnetic interference shielding

Electromagnetic interference shielding materials being sufficiently stretchable at low temperatures have a wider range of applications. Herein, stretchable electromagnetic shielding films for low temperatures applications with segregated conductive networks were produced by a simple method of evaporating carboxylated nitrile butadiene rubber (XNBR) latex containing lithium bis(pentafluoroethylsulfonyl)imide (Li–PFSI) doped poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS). It is proved that the mechanical and electrical properties can be improved by changing the crystallization of PEDOT by doping. For the composite film with 4 wt% PEDOT:PSS and 1.4 mm thickness, electromagnetic interference shielding efficiency can maintain at about 60 dB at 100 % strain and 48 dB at 150 % strain, being the highest among stretchable EMI shields reported. At −10 °C and 100 % strain, shielding efficiency of the composite film with 8 wt% PEDOT:PSS is about 32 dB, indicating that the stretchable film is promising in applications in wearable devices, flexible devices, etc. for EMI shielding at low temperatures.

Vat photopolymerization of silica reinforced styrene-butadiene rubber elastomeric nanocomposites

Compared to their unfilled counterparts, elastomeric nanocomposites offer tailorable combinations of properties, including improved mechanical properties, increased durability, and enhanced thermal and electrical conductivity. However, the high viscosity caused by the presence of both the high molecular weight elastomer and the inclusion of fillers complicates additive manufacturing (AM) of elastomeric nanocomposites. This is especially challenging in vat photopolymerization (VP) AM, which requires resins that possess low viscosity (< 10 Pa·s) and exhibit sufficient storage modulus (∼ 104 Pa) when photocured. To address this process limitation, the authors have previously demonstrated decoupling the relationship between viscosity and molecular weight via VP of a photocurable composite latex resin. In this approach, a photocurable matrix is photocured as a scaffold around the latex particles, which provides sufficient modulus for the printed "green" part. Following a dehydration post-processing step, the latex particles coalesce to provide the final elastomeric mechanical properties without compromising feature resolution.In this work, the authors explore the effects of the addition of silica nanoparticles (10, 15, and 20 wt.%) on (i) the printability of photocurable styrene-butadiene rubber (SBR) latex resin and (ii) the mechanical properties of the resultant printed composites. The printable photocurable silica-SBR colloidal resin is realized by balancing the viscosity of the resin, the modulus of the cured green body, the silica nanoparticles content for reinforcement, and the high SBR content for elastomeric behavior. Specifically, the photocurable colloidal resin's viscosity is controlled by formulation design, while high silica nanoparticle content in the final part is achieved through evaporation of unreactive diluent. Characterization of the printed SBR nanocomposites with 20 wt.% silica reinforcement elucidated significant enhancements in the tensile strength (53 % increase), Young's modulus (671 % increase), and Shore A hardness (108 % increase) compared to printed SBR without filler reinforcement. To the authors' knowledge, this is the first report of 3D printing rubber nanocomposite using VP.

Radiative and mechanical energies in galaxies

Context. Atomic and molecular lines emitted from galaxies are fundamental tracers of the medium responsible for the emission and contain valuable information regarding the energy budget and the strength of the different feedback mechanisms. Aims. The goal of this work is to provide a new framework for the interpretation of atomic and molecular lines originating from extragalactic sources and a robust method to deduce the mechanical and radiative energy budget from a set of observations. Methods. Atomic and molecular lines detected in a given object are assumed to result from the combination of distributions of shocks and photo-dissociation regions (PDRs) within the observational beam. The emission of individual structures is computed using the Paris-Durham shock code and the Meudon PDR code over a wide range of parameters. The total emission is then calculated assuming probability distribution functions for shocks and PDRs. A distance between the observational dataset and the model is finally defined based on the ratios of the observed to the predicted intensities. Results. As a test case scenario, we consider the radio galaxy 3C 326 N. The dataset is composed of 12 rotational and ro-vibrational lines of H2 and the fine structure lines of C+ and O. Our interpretative framework shows that both shocks and PDRs are required to explain the line fluxes. Surprisingly, viable solutions are obtained at low density only (nH &lt; 100 cm−3), indicating that most of the emission originates from diffuse interstellar matter. The optimal solution, obtained for nH = 10 cm−3, corresponds to a distribution of low-velocity shocks (between 5 and 20 km s−1) propagating in PDR environments illuminated by a UV radiation field ten times larger than that in the solar neighborhood. This solution implies that at least 4% of the total mass carried by the PDRs is shocked. The H2 0-0 S(0) 28 μm, [CII] 158 μm, and [OI] 63 μm lines originate from the PDR components, while all the other H2 lines are mostly emitted by shocks. The total solid angles sustained by PDRs and shocks imply that the radiative and mechanical energies reprocessed by these structures are LUV = 6.3 × 109 L⊙ and LK = 3.9 × 108 L⊙, respectively, in remarkable agreement with the values of the IR luminosity deduced from the fit of the spectral energy distribution (SED) of 3C 326 N, and consistent with a small fraction of the active galactic nuclei (AGN) jet kinetic power dissipated in the interstellar medium (≈1%). Conclusions. This work shows that the radiative and mechanical energy budget of galaxies can be derived from the sole observations of atomic and molecular lines. It reveals the unexpected importance of the diffuse medium for 3C 326 N, in contrast to previous studies. A last-minute comparison of the model to new JWST data obtained in 3C 326 N shows a striking agreement and demonstrates the ability of the model to make accurate predictions. This framework opens new prospects for the prediction and interpretation of extragalactic observations, in particular in the context of JWST observations.

Natural Rubber Latex-Modified Concrete with Bottom Ash for Sustainable Rigid Pavements

This article investigates the viability of using natural rubber latex (NRL)-modified concrete with bottom ash (BA) as a partial replacement for river sand in sustainable rigid pavements. Concrete mixes with 10% and 20% BA replacement ratios and varying NRL dosages (0%, 1.0%, 1.5%, and 2.0% by weight of cement) were prepared and evaluated for their mechanical and microstructural characteristics. Results showed that BA substitution decreased the compressive strength of concrete. However, the addition of NRL at an optimal dosage of 1.0% significantly improved both the compressive and flexural strengths. The 10%BA+1.0%NRL and 20%BA+1.0%NRL mixes exhibited mechanical properties surpassing the control mix and meeting the minimum requirements for rigid pavement materials. However, excessive NRL content (1.5% and 2.0%) led to a reduction in mechanical strength. Scanning electron microscopy analysis exhibited a denser and more compact matrix in NRL-modified BA concrete, with NRL films enhancing the interfacial bonding and crack-bridging mechanism. Nonetheless, excessive NRL content resulted in the formation of abundant and thicker NRL films, which disrupted the continuity of the cement matrix and created weak zones. X-ray diffraction analysis confirmed the existence of crucial crystalline phases and their optimal balance in the 20%BA+1.0%NRL mix, contributing to its superior performance. Mixes with excessive NRL contents exhibited lower intensities of quartz, calcite, and portlandite peaks, indicating a disturbance in the proper formation and growth of essential crystalline phases. The findings demonstrated the potential of NRL-modified BA concrete as an eco-friendly and high-performance alternative for sustainable rigid pavements when using an optimal NRL dosage, promoting the employment of waste resources and reducing the environmental impact of the construction industry. Doi: 10.28991/CEJ-2024-010-08-05 Full Text: PDF

Maleated epoxidized natural rubber grafted cassava starch/silver composite coating for cloth glove: Preparation and physical properties

The green composite was obtained from maleated epoxidized natural rubber (MENR) latex grafted cassava starch (CS) (MNS) and silver nanoparticles (AgNPs) by using a green route process. The immersion of AgNPs in the MNS matrix was checked with UV–visible spectrometer. The SEM was applied to study the morphology of AgNPs particle. The thermal stability of the MNSAg composite increased with increasing AgNPs. The AgNPs well distributed in the MNS matrix. The silver was used to facilitate the facile and fast preparation and to improve the mechanical strength and thermal stability at 420–450 °C of the MNSAg composites. The MNSAg composite containing AgNPs exhibited excellent antibacterial activities against both Escherichia coli and Staphylococcus aureus. Moreover, it showed the high UV absorption. It was used to coat with cloth gloves. The degree of biodegradation of this sample was about 80–90 % after being buried in soil.

Dispersion polymerization of AM-AMPS-DAM-DOH and its sand control property

Sand production in oil wells is a common challenge during the oil extraction process. Water-soluble polymers have attracted attention due to their low toxicity, cost-effectiveness, ease of direct injection, and excellent thermal stability. However, the dry polymer injection process commonly used in offshore oil fields is complex. Therefore, this paper employs acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), a dihydroxy monomer (DOH), and a functional monomer (DAM) containing ketone groups and self-crosslinking properties as monomers. A polymer latex type sand control agent was prepared through dispersion polymerization for direct application on offshore platforms. This paper utilizes flocculation time and maximum sand free flow rate as inspection indicators and utilizes both the one-factor-at-a-time method and the surface response method to optimize the synthesis conditions of the sand control agent. The optimal synthesis conditions are obtained: total monomer concentration of 9.15 wt%, DOH concentration at 10 wt% of the total monomer concentration, ammonium sulfate (AS) concentration of 27.02 wt%, dispersant concentration of 2.13 wt%, initiator concentration at 0.25 wt% of the total monomer concentration, reaction time of 12 h, and reaction temperature of 40 °C. Under the conditions of concentration ≥2000 mg/L and curing time ≥4 h, the sand control agent is suitable for sand stabilization under formation conditions of temperatures between 50 and 80 °C, pH levels ranging from 3 to 9, salinity <30000 mg/L, and sand particle size of ≥100 μm. The research results of this paper can serve as a valuable reference for the control of oilfield sand production.

Effects of Gamma-Synthesized Chitosan on Morphological, Thermal, Mechanical, and Heavy-Metal Removal Properties in Natural Rubber Foam as Sustainable and Eco-Friendly Heavy Metal Sorbents

The properties of natural rubber foam (NRF) containing gamma-synthesized chitosan (CS) powder were investigated to address the growing demand for efficient methods to treat industrial wastewater contaminated with heavy metals. The CS powder was prepared by irradiating chitin (CT) powder with varying doses of gamma rays (0–100 kGy), followed by deacetylation using 40% sodium hydroxide (NaOH) at 100 °C for 1 h. The resulting CS powders were then mixed with natural rubber latex (NRL) at different contents (0, 3, 6, and 9 parts per hundred parts of rubber by weight; phr) and processed using Dunlop techniques to prepare the foam samples. The experimental findings indicated that the degree of deacetylation (%DD) of the CS powder increased initially with gamma doses up to 60 kGy but then decreased at 80 and 100 kGy. In addition, when the CS powder was incorporated into the NRF samples, there were increases in total surface area, density, compression set, and hardness (shore OO), with increasing gamma doses and CS contents. Furthermore, the determination of heavy metal adsorption properties for Cu, Pb, Zn, and Cd showed that the developed NRF sample exhibited high adsorption capacities. For instance, their removal efficiencies reached 94.9%, 82.5%, 91.4%, and 97.0%, respectively, in NRF containing 9 phr of 60 kGy CS. Notably, all adsorption measurements were determined using 3 cm × 3 cm × 2.5 cm specimens submerged in respective metal solutions, with an initial concentration of 25 mg/L. However, the removal capacity per unit mass of the sample (mg/g) showed less dependencies on CS contents, probably due to the higher density of CS/NRF composites in comparison to pristine NRF, resulting in a smaller volume of the former being submerged in the solution, subsequently suppressing the effects from CS in the adsorption. Lastly, tests on the reusability of the developed NRF indicated that the samples could be reused for up to three cycles, with the Cu removal capacity remaining relatively high (83%) in the sample containing 9 phr of 60 kGy CS. The overall outcomes implied that the developed NRF with the addition of gamma-synthesized CS not only offered effective and eco-friendly heavy metal adsorption capacity to improve public health safety and the environment from industrial wastewater but also promoted greener and safer procedures for the synthesis/modification of similar substances through radiation technologies.

Investigation of the Biosafety of Commercially Available Natural Rubber Latex and Synthetic Polyurethane Condom Materials

To investigate the biological safety of commercially available natural rubber latex and synthetic polyurethane condoms. Natural rubber latex condom brands of A1 and A2 and polyurethane condom brands of B1 and B2 were purchased from large chain pharmacies in Chengdu, with three packages randomly selected for each brand. The study assessed the toxic effects of condom extracts on L-929 mouse fibroblasts according to GB/T standards. Gross observation and histopathological evaluation were conducted to assess the irritation reactions of condoms on the vagina and penis of rabbits (3 rabbits were used for each brand), as well as their sensitization effects on guinea pig skin. Additionally, the impact of continuous perfusion of condom extracts of the vaginas of SD rats for 30 days on their reproductive systems was evaluated, following GB/T standards (5 rats were used for each brand). Extracts from natural rubber latex condom brands A1 and A2, at concentrations of 100% and 50%, exhibited significant cytotoxicity, with optical density (OD) values being significantly lower than those of the blank control group and the polyurethane condom brands B1 and B2 (P<0.01). There was no significant difference in cell morphology and OD values between the extracts of B1 and B2 and the blank control group (P>0.05). Vaginal congestion was found in 3 rabbits from A1 group and 1 rabbit from the A2 group, while no obvious congestion was noted in rabbits from the B1 and the B2 groups. Histopathological examination showed scattered inflammatory cell infiltration in the vaginal tissue of 3 rabbits from the A1 group and 2 rabbits from the A2 group, and slight congestion in the blood vessels of the lamina propria. No obvious pathological changes were observed in the vaginal tissue of polyurethane brand rabbits. Two rabbits from the A1 group and 1 rabbit from the A2 group showed transient and mild erythema on the penis during the experiment. Histopathological examination showed that 1 rabbit from A1 group had small foci of pericapillary lymphocytes in the dermis of the penis, while no significant pathological changes were observed in the penile tissue of A2, B1, and B2 groups. After 30 days of continuous vaginal perfusion with condom extract, 3 rats in A1 group and 2 rats in the A2 group had uterine congestion, with the degree of congestion being lower in the A2 group. No significant congestion or pathological changes were observed in the vaginal and penile tissues of rabbits, or in the uterine tissues of rats from the polyurethane groups. None of the 4 groups of guinea pigs showed significant skin allergic reactions to the condom extracts. Significant differences in biosafety exist among condoms of various materials and brands. To ensure product safety, it is crucial to strengthen quality control and regulatory oversight after condoms become commercially available.