Rubber Polymer Research Articles

Computer-Aided Silicone Rubber Polymer Design Based on Connectivity Index and Molecular Dynamics Methods

Computer-Aided Silicone Rubber Polymer Design Based on Connectivity Index and Molecular Dynamics Methods

Electrostatic energy-driven contact electrification mechanism from the ReaxFF molecular dynamics perspective.

Understanding the underlying principles of contact electrification is critical for more efficient triboelectric nanogenerator (TENG) development. Herein, we use ReaxFF molecular dynamics simulations in conjunction with a charge equilibration method to investigate the contact electrification mechanism in polyisoprene (PI), a natural rubber polymer, when it comes into contact with copper (Cu) and polytetrafluoroethylene (PTFE). The simulations reveal that the charge transfer directions in the PI/Cu and PI/PTFE contact models are opposite, and the amount of charge transfer in the former is substantially less than that in the latter, which are consistent with our TENG measurements. Contact electrification is revealed to be a spontaneous process that occurs to lower electrostatic energy, and the electrostatic energy released during contact electrification of PI/PTFE is greater than that of PI/Cu, which can be correlated with the relative strength of triboelectric charging observed for the two systems. A compression simulation of the PI/Cu contact model reveals that the quantity of charge transfer grows exponentially as compressive strain increases. Despite increasing the total energy of the system due to densification and distortion of the polymer structure, the applied deformation results in an energetically more stable electrostatic arrangement. We also find that the incorporation of a carbonaceous material into a polyisoprene matrix causes a faster increase in the amount of charge transfer with compressive strain, which is governed by a steeper electrostatic energy profile. This study provides an alternative perspective on the contact electrification mechanism, which could be beneficial for the development of energy harvesting devices.

RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS THE INNER PART OF ROD SEALS

ABSTRACT The viscoelastic properties of rubber polymer–based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion and the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and the acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications were varied to demonstrate the different degree of contraction resulting from three-dimensional printing. An ACN content of 34% and an average molar mass of 2.47·105 g·mol−1 with a dispersity index of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as the inner part of rod seals.

Biotechnology Application in Starch/Natural Rubber Polymer Degradation: Panacea for Rubber Waste Disposal and Utilization

Biotechnology Application in Starch/Natural Rubber Polymer Degradation: Panacea for Rubber Waste Disposal and Utilization

Investigating the synergistic anti-aging effects of Sasobit and recycled engine oil in styrene-butadiene rubber modified asphalt

During the preparation of asphalt mixtures, styrene-butadiene rubber (SBR) polymers are susceptible to thermal decomposition, which can significantly impair the binder’s low-temperature performance. This study explores the potential of combining warming agents with waste materials to enhance the low-temperature properties and aging resistance of the binder. Specifically, it examines the synergistic impact of Sasobit/recycled engine oil (Sasobit/REO) composites on the rheological and physical attributes of styrene-butadiene rubber asphalt binder (SBRAB). Utilizing fluorescence microscopy (FM), bending beam rheometer (BBR), and dynamic shear rheometer (DSR), the study assesses the aging resistance and modification mechanisms of Sasobit/REO on SBRAB. The findings indicate that the incorporation of Sasobit/REO composites more effectively reduces the mix preparation temperature than either component alone. The preparation of Sasobit/REO warm mix asphalt mixtures is feasible at temperatures 20°C lower than those required for traditional hot mixtures. These composites also enhance the performance of SBRAB at both high and low temperatures, counteracting the adverse effects associated with the individual use of Sasobit or REO. This reduced short-term aging temperature is beneficial in lessening the negative impact of high temperatures on SBRAB’s performance. Moreover, the addition of Sasobit/REO composites significantly improves the thermal cracking resistance of SBRAB mixtures. The study also demonstrates that Sasobit/REO enhances the short-term and long-term aging resistance of SBRAB, paving the way for the broader application of this novel warm mix additive in the asphalt industry.

Multi-criteria optimization of SBR-modified mortar incorporating polyethylene terephthalate waste

Thermosetting post-consumer plastics like polyethylene terephthalate (PET) raise serious recycling challenges, leading frequently to disposal through incineration or landfilling. This study assesses the feasibility of cementitious materials containing PET additions including the influence of cement content, water-to-cement ratio (w/c), styrene-butadiene rubber (SBR) polymer additions, and PET volume on the fresh and hardened properties. The mixture proportioning followed the Taguchi methodology, which entailed the utilization of four factors, each possessing three different levels to create an L9 orthogonal matrix. The assessment included diverse performance indicators such as flow, compressive strength, flexural strength, bond strength, water absorption, and resistance to carbonation. Test results revealed that the incorporation of SBR and PET degraded the compressive strength, albeit this can be restored by increasing the cement content and/or reducing w/c. The addition of SBR significantly improved the flexural and bond strengths yet curtailed the water absorption and resistance to carbonation due to increased closed porosity that facilitated the transport properties. The multi-criteria optimization approach (TOPSIS) indicated that superior performance can be achieved using a cement content of 525 kg/m3, w/c of 0.55, SBR of 3.5 %, and PET incorporation of 4.5 %. These parameters were subsequently employed in the development of multivariate regression models, allowing for the prediction of fresh and hardened properties in SBR-PET mortar.

The Time-Temperature Superposition of Polymeric Rubber Gels Treated by Means of the Mode-Coupling Theory.

Viscoelastic relaxation measurements on styrene-butadiene rubbers (SBRs) doped with carbon nanotube (CNT) at different concentrations around the sol-gel transition show the time-temperature superposition (TTS). This process is described in terms of the mode coupling theory (MCT) approach to viscoelasticity by considering the frequency behavior of the loss modulus E″(ω) and showing that the corresponding TTS is linked to ω1/2 decay. From the analysis of the obtained data, we observe that the interaction between SBRs and CNT determines different levels of decay according to their concentration. Systems with the lowest CNT concentration are only characterized in the studied T-range by their fragile glass-forming behavior. However, at a specific temperature TL, those with the highest CNT concentration show a crossover towards pure Arrhenius that, according to the MCT, indicates the presence of kinetic glass transition (KGT), where system response functions are characterized by scaling behaviors.

Performance Enhancement of Silicone Rubber Using Superhydrophobic Silica Aerogel with Robust Nanonetwork Structure and Outstanding Interfacial Effect.

The application of high-performance rubber nanocomposites has attracted wide attention, but its development is limited by the imbalance of interface and network effects caused by fillers. Herein, an ultrastrong polymer nanocomposite is successfully designed by introducing a superhydrophobic and mesoporous silica aerogel (HSA) as the filler to poly(methyl vinyl phenyl) siloxane (PVMQ), which increased the PVMQ elongation at break (∼690.1%) by ∼9.3 times and the strength at break (∼6.6 MPa) by ∼24.3 times. Furthermore, HSA/PVMQ with a high dynamic storage modulus (G'0) of ∼12.2 MPa and high Payne effect (ΔG') of ∼9.4 MPa is simultaneously achieved, which is equivalent to 2-3 times that of commercial fumed silica reinforced PVMQ. The superior performance is attributed to the filler-rubber interfacial interaction and the robust filler-rubber entanglement network which is observed by scanning electron microscopy. When the HSA-PVMQ entanglement network is subjected to external stress, both the HSA and bound-PVMQ chains are synergistically involved in resisting structural evolution, resulting in the maximized energy dissipation and deformation resistance through the desorption of the polymer chain and the slip/interpenetrating of the exchange hydrogen bond pairs. Hence, highly aggregated nanoporous silica aerogels may soon be widely used in the application of reinforced silicone rubber or other polymers shortly.

Chromolaena odorata layered-nitrile rubber polymer transdermal patch enhanced wound healing in vivo.

The objective is to investigate the healing efficacy of a Chromolaena odorata layered-nitrile rubber transdermal patch on excision wound healing in rats. Wounds were induced in Sprague-Dawley rats and were later treated as follows: wound A, the negative control, received no treatment (NC); wound B, the negative control with an empty nitrile rubber patch (NC-ERP); wound C, treated with a C. odorata layered-nitrile rubber patch (CO-NRP); and wound D, the positive control with Solcoseryl gel with a nitrile rubber patch (PC-SG-NRP). After 1, 3, 6, 10, and 14 days, the rats were sacrificed and analyzed for wound contraction, protein content, hexosamine, and uronic acid levels. Macroscopic observation showed enhanced wound healing in wounds treated with CO-NRP with a wound contraction percentage significantly higher (p<0.05) on days 6 and 10 compared to those treated with NC-ERP. Similarly, protein, hexosamine, and uronic acid contents were also significantly higher (p<0.05) in CO-NRP-treated wounds when compared with wounds treated with NC-ERP. Histological findings showed denser collagen deposition and faster granulation tissue formation in wounds treated with CO-NRP. From the results obtained, it is concluded that the C. odorata layered-nitrile rubber transdermal patch was effective in healing skin wounds.

Comparison of Two Methods for Measuring the Temperature Dependence of H2 Permeation Parameters in Nitrile Butadiene Rubber Polymer Composites Blended with Fillers: The Volumetric Analysis Method and the Differential Pressure Method.

Hydrogen uptake/diffusivity in nitrile butadiene rubber (NBR) blended with carbon black (CB) and silica fillers was measured with a volumetric analysis method in the 258-323 K temperature range. The temperature-dependent H2 diffusivity was obtained by assuming constant solubility with temperature variations. The logarithmic diffusivity decreased linearly with increasing reciprocal temperature. The diffusion activation energies were calculated with the Arrhenius equation. The activation energies for NBR blended with high-abrasion furnace CB and silica fillers increased linearly with increasing filler content. For NBR blended with medium thermal CB filler, the activation energy decreased with increasing filler content. The activation energy filler dependency is similar to the glass transition temperature filler dependency, as determined with dynamic mechanical analysis. Additionally, the activation energy was compared with that obtained by the differential pressure method through permeability temperature dependence. The same activation energy between diffusion and permeation in the range of 33-39 kJ/mol was obtained, supporting the temperature-independent H2 solubility and H2 physisorption in polymer composites.

Self-adhesion of uncrosslinked poly(butadiene-co-acrylonitrile), i.e. nitrile rubber, an inhomogeneous and associative polymer.

Nitrile rubber (i.e., NBR) is a crosslinked copolymer of butadiene and acrylonitrile that finds widespread use in the automotive and aerospace industry as it sustains large, reversible deformations while resisting swelling by petrochemical fuels. We recently demonstrated that this material has a drift in composition due to the difference in reactivity between acrylonitrile and butadiene monomers during emulsion copolymerisation. Thus, although NBR is often thought of as a random copolymer, it does experience thermodynamic driving forces for self-assembly and kinetic barriers for processing like those of block copolymers.1 Here, we illustrate how such drift in composition hinders interdiffusion and prevents self-adhesion. The key result is that contacting uncrosslinked NBR (i) in the melt, (ii) in the presence of tackifiers, or (iii) in the presence of organic solvents promotes interdiffusion and enables self-adhesion. However, the contact times required for self-adhering, tc ∼ O(100 h), are orders of magnitude above those needed for non-polar synthetic rubbers like styrene-butadiene rubber (i.e., SBR) of comparable molecular weights and glass transition temperatures, tc ∼ O(100 s), unveiling the dramatic effect of compositional inhomogeneities and physical associations on polymer interdiffusion and large-strain mechanical properties. For example, when welded with organic solvents, the self-adhesion energy of NBR continues to increase after the solvent has evaporated because of polymer nanostructuring.

Construction of a laparoscopic appendectomy model.

Appendectomy is the standard treatment for appendicitis, with the laparoscopic technique offering benefits like lower infection rates and quicker recovery. However, residents often have their first practical experience with the procedure on real patients, increasing surgical risks. In this context, medical simulation emerges as a crucial methodology, allowing professionals to experience a variety of scenarios while preventing harm to patients. The objective of this study is to describe the production of an "ex-vivo" simulation model for laparoscopic appendectomy. Cold ceramic structures were used to manually shape the anatomical model of the appendix, ensuring its rigidity. On this model, we poured materials to create a flexible mold using acetic silicone. Once the mold was made, we filled it with thermo-moldable styrene polymer rubber, along with dye, and fused it at a specific temperature. This process resulted in the manufacture of a piece that simulates the appendix, being tear-resistant and suturable, faithfully replicating the structure and characteristics of a human organ. The low weight of the materials facilitates transport, allowing them to be reproduced and used in various situations, from training in hospital settings to universities. The model is applicable in didactic simulations with medical students, residents, and surgeons. Its ease of production and low cost contribute to the practices being repeatable, ensuring a better development of surgical skills. This work not only contributes to the advancement of medical simulation but also highlights the importance of innovative and collaborative solutions in improving medical education and promoting patient safety.

Reactive Extrusion of Waste Plastics with Compatibilizer and Lightly Pyrolyzed Crumb Rubber for Asphalt Modification

Modifying asphalt is a potentially high-value application for reusing waste plastics because of the high-volume usage of asphalt in highway construction. However, simply blending hot plastics and asphalt encounters difficulties related to the poor solubility of polymers, which limits the formation of a swollen network with asphalt molecules. The polymer phases also tend to coalesce and separate from asphalt during high-temperature storage in static conditions. The present study developed an innovative process to stabilize waste plastics in asphalt and improve binder storage stability by using lightly pyrolyzed crumb rubber together with a chemical compatibilizer. Both polymers were extruded to produce a thermoplastic elastomer (TPE) for asphalt modification. The mechanical performance and chemical reactions of TPEs were characterized via tension test and Fourier transform infrared spectroscopy. The storage stability and rheological properties of modified binder blends were evaluated through laboratory asphalt stability test and dynamic shear rheometer test. Polymer phases and network structures were characterized through optical microscopy. It was found that the pyrolyzed and reactive extrusion process improved the rubber solubility and polymer interaction, and therefore the storage stability of modified binder blends. The co-existence of rigid plastic and soft rubbery regimes in an entangled network provided a promising pathway to improve the mechanical performance of asphalt binders in both high- and low-temperature domains.

Production of micro-lignocellulosic fibril rubber composites and their application in coated layers of building materials

Novel composite materials were made by combining micro-lignocellulosic fibrils and natural rubber applied as spray coated layers for building materials. The micro-lignocellulosic fibrils were produced based on the mechanical pulping process with jute bast as the raw material. The obtained micro-lignocellulosic fibrils had a good content of water-suspended materials with fibril widths of about 0.1 to 1.0 µm and fibril length of about 100 to 150 µm. The composites were produced using natural rubber mixed with the micro-lignocellulosic fibrils at 0, 5, and 10 parts per hundred of rubber, vulcanizing sulfur, and activated zinc oxide. The fibril-rubber suspension was formed in the composite sheets with a thickness of 0.5 to 1.5 mm using a spray coating technique and was oven-dried at 100 °C. The rubber composite had a homogenous fibril distribution in the rubber composite matrix, with good bonding between the fibrils and the rubber polymers. The fibrils contributed to the strength reinforcement of the rubber composite layers. The application of the micro-lignocellulosic fibril rubber composites coated onto industrial fiber cement boards enhanced the thermal insulation properties, which had a lower degree of thermal conductivity and heat diffusivity and enhanced the toughness and waterproofing of the fiber cement boards.

Engineered Methylococcus capsulatus Bath for efficient methane conversion to isoprene

Isoprene has numerous industrial applications, including rubber polymer and potential biofuel. Microbial methane-based isoprene production could be a cost-effective and environmentally benign process, owing to a reduced carbon footprint and economical utilization of methane. In this study, Methylococcus capsulatus Bath was engineered to produce isoprene from methane by introducing the exogenous mevalonate (MVA) pathway. Overexpression of MVA pathway enzymes and isoprene synthase from Populus trichocarpa under the control of a phenol-inducible promoter substantially improved isoprene production. M. capsulatus Bath was further engineered using a CRISPR-base editor to disrupt the expression of soluble methane monooxygenase (sMMO), which oxidizes isoprene to cause toxicity. Additionally, optimization of the metabolic flux in the MVA pathway and culture conditions increased isoprene production to 228.1 mg/L, the highest known titer for methanotroph-based isoprene production. The developed methanotroph could facilitate the efficient conversion of methane to isoprene, resulting in the sustainable production of value-added chemicals.

Effect of Sasobit/Waste Cooking Oil Composite on the Physical, Rheological, and Aging Properties of Styrene–Butadiene Rubber (SBR)-Modified Bitumen Binders

The modifying effects of polymer on bitumen low-temperature performance are substantially compromised by the thermal breakdown of styrene–butadiene rubber (SBR) polymer during bitumen mixture production operations. The efficacy of the utilization of Sasobit/waste cooking oil (Sasobit/WCO) as a warm-mix additive has been demonstrated in mitigating the adverse consequences of thermal aging on SBR-modified bitumen binder (SB) while preserving the binder’s original performance characteristics. However, few studies have been conducted to further investigate the rheological properties and aging resistance of SB modified with Sasobit/WCO compounds. In this work, three additives—Sasobit, WCO, and Sasobit/WCO composite—were selected, and their effects on the physical and rheological characteristics of SB as well as the temperatures at which the mixtures were prepared were assessed. In addition, by using dynamic shear rheometers (DSR) and bending beam rheometers (BBR), the effects of this innovative warm-mix addition on the performance grade (PG) and aging resistances of SB were evaluated. According to the results, Sasobit/WCO composites outperform Sasobit and WCO in lowering the mixture preparation temperature. Sasobit/WCO also improves both the high- and low-temperature performance of SB simultaneously. Compared to hot-mix asphalt mixtures, the addition of Sasobit/WCO reduces the preparation temperature of the bitumen mixtures by 19 °C, which in turn helps to minimize the negative effects of temperature aging on the functioning of the SB. Additionally, the Sasobit/WCO composite addition can improve the SB mixture’s resistance to thermal cracking. After the introduction of Sasobit/WCO, the high-temperature PG of SB was raised by two levels, regardless of whether the warm-mix impact was taken into account. With the addition of Sasobit/WCO, SB’s resilience to short-term aging was enhanced.

Rate-dependent fractional constitutive model for nonlinear behaviors of rubber polymers

In this study, a fractional constitutive model with continuous power-law variable order is proposed to characterize the whole deformation of rubber polymers. The criterion between strain rate and relaxation time is subsequently established and incorporated into the proposed fractional model to demonstrate the rate-dependent behaviors. The elastic modulus is found to exhibit a power-law relation with respect to ln(c/cref), which can degenerate into a linear one at low strain rates and corresponds well with the classical theory. Simulations of experimental results varying in a wide strain-rate range validate the applicability of the rate-dependent fractional model. A comparison with classical viscoelastic model illustrates that the proposed model possesses fewer parameters and presents higher accuracy.

Effect Of Graphene Oxide on Poly (Methyl Methacrylate)-Grafted Natural Rubber Polymer Electrolytes

Polymer electrolytes (PE) are presently the subject of the majority of research due to their capacity to replace liquid electrolyte that suffer from high flammability and electrolyte leakage and also as a new forms of electrical power production and storage systems. Solid polymer electrolytes (SPE) typically have low ionic conductivity at room temperature because of the high crystallinity of the polymers. Methyl-grafted natural rubber has been studied extensively by a number of researchers due to its advantageous properties such as high flexibility, and ability to solvate inorganic salts to form a polymer-salt complex. Graphene oxide (GO) was used as a nanofiller, ammonium triflate (NH4CF3SO3) served as a dopant salt, and 30 % polymethyl methacrylate grafted natural rubber (MG30) served as the polymer host in the preparation of the nanocomposite polymer electrolyte (CPE) using the solution casting-method. Electrochemical impedance spectroscopy (EIS) was used to analyse the ionic conductivity of the samples, and Fourier-transform infrared spectroscopy (FTIR) was used to analyse the complexation between salt, polymer host and filler while Optical microscope was used to study the surface morphology of the prepared CPE samples. The decrease in peak strength for C=O in the FTIR spectra indicates the interaction between the polymer host and salt The sample containing 15 weight percent NH4CF3SO3 had the highest conductivity, which was 2.05×10-5 S cm-1. This substance has the potential to be used in energy storage devices like batteries and supercapacitors as an alternative to commercial liquid electrolyte.

Stiffness Constitutive Characteristics of Elastic Disordered Microporous Metal Rubber Considering Temperature Effects

Elastic disordered microcellular metal rubber (EDMMR) is a lightweight metal material widely employed for damping or support in high‐temperature environments, addressing the limitations of traditional polymer rubbers. Herein, three sets of solid finite element models of EDMMR with different relative densities are developed using virtual manufacturing technology (VMT). Thermal–mechanical coupled finite element simulations explore the dynamic evolution of two typical spatial topological structures in the material's microstructure: unit contact characteristics and angle distribution under temperature variations. Results indicate that the mechanical performance of the material under high‐temperature loads exhibits distinct spatial topological structures compared to those at room temperature. At 100, 200, and 300 °C, the material experiences internal stress distributions of up to 0.5, 1.2, and 1.8 MPa, respectively, due to expansion. Additionally, during the initial loading stage, stress differentials of approximately 0.4 MPa are observed between different temperatures due to boundary effects. Furthermore, the study investigates the probability density distribution of typical microstructural combinations of EDMMR along the forming direction based on VMT, enhancing the generality of the constitutive model. Finally, three groups of EDMMR samples with different relative densities are prepared using standardized processes, and the model is validated through high‐temperature quasistatic compression experiments.

Microplastic in long-term soil monitoring: first spatial and temporal data on plastics in agricultural topsoils

PurposeWithin the emerging field of soil related microplastic (MP) research, little is known about spatio-temporal variations of MP concentrations in soils. To overcome this current knowledge gap, we suggest the exploitation of long-term soil monitoring programmes (LTSM) and its archived soil samples, to gain first data on spatio-temporal variations within soil MP contamination.MethodsWe analysed 32 archived topsoil samples of 13 cropland and 3 control sites, including grassland and forest sites, which are part of the LTSM programme of the German federal state of Hesse. Analysed samples cover a time span of 10–16 years. MP (>300 µm) have been extracted via sodium chloride (NaCl, 1.2 g cm−3) density separation, Nile Red staining and fluorescent optical identification followed by ATR-FTIR analysis of individual MP.ResultsWe found MP contamination (mean 34.66 ± 24.08 p kg−1) from mainly PE and synthetic rubber polymers. Furthermore, we were able to detect spatial MP contamination hotspots, with unexpected high MP concentrations in control grassland and forest LTSM sites. In case of temporal trends, we cannot conclude a general increase of MP concentrations over time. However, as we found MP in older and newer samples, MP contamination is likely to be ubiquitous in topsoils and has already been present in the environment for several decades.ConclusionOur findings underline the role of cropland topsoils as MP reservoirs, but raise questions on the MP storage in grassland and forest soils. Applying MP analytical tools to archived LTSM samples enables first insights within non-targeted spatial source analysis and temporal trends of soils MP pollution. If enhanced analytical methods will be applied to LTSM samples, it will be possible to gain more detailed insights within spatio-temporal MP dynamics in soils.