Commercial Rubber Research Articles

Shape‐Memory Semicrystalline Polymeric Materials Based on Various Rubbers

AbstractA simple strategy is presented for the fabrication of shape‐memory materials containing commercial rubbers including natural rubber, cis‐polybutadiene, and styrene‐butadiene rubber. Dissolution of the rubbers in n‐octadecyl acrylate (C18A) monomer followed by UV polymerization at 30 °C leads to the formation of interconnected interpenetrating polymer networks (c‐IPNs) possessing crystalline domains. They exhibit melting (Tm) and crystallization temperatures (Tcry) between 45–50 and 35–40 °C, respectively, that can be tuned by the amount and the type of the rubbers. All c‐IPNs exhibit a significant temperature sensitivity in their viscoelastic and mechanical properties when the temperature is changed between below and above Tm and Tcry. The morphology of c‐IPNs consists of amorphous nanoparticles of around 64 nm diameter composed of interconnected noncrystalline poly(C18A) (PC18A) and rubber networks, surrounded by crystalline PC18A segments. c‐IPNs exhibit tunable mechanical properties, for example, their Young's modulus and toughness can be varied between 8.3–73 MPa, and 1.9–23 MJ·m−3, respectively, by changing the amount and type of the rubber. Because of the coexistence of chemical cross‐links and crystalline domains acting as the netpoints and switching segments, respectively, c‐IPNs exhibit an efficient shape‐memory function as demonstrated by their potential application as a robotic gripper.

Processing, Performance Properties, and Storage Stability of Ground Tire Rubber Modified by Dicumyl Peroxide and Ethylene-Vinyl Acetate Copolymers.

In this paper, ground tire rubber was modified with dicumyl peroxide and a variable content (in the range of 0–15 phr) of ethylene-vinyl acetate copolymers characterized by different vinyl acetate contents (in the range of 18–39 wt.%). Modification of ground tire rubber was performed via an auto-thermal extrusion process in which heat was generated during internal shearing of the material inside the extruder barrel. The processing, performance properties, and storage stability of modified reclaimed ground tire rubber were evaluated based on specific mechanical energy, infrared camera images, an oscillating disc rheometer, tensile tests, equilibrium swelling, gas chromatography combined with a flame ionization detector, and gas chromatography with mass spectrometry. It was found that the developed formulas of modified GTR allowed the preparation of materials characterized by tensile strengths in the range of 2.6–9.3 MPa and elongation at break in the range of 78–225%. Moreover, the prepared materials showed good storage stability for at least three months and satisfied processability with commercial rubbers (natural rubber, styrene-butadiene rubber).

Exposure to leachates from post-consumer plastic and recycled rubber causes stress responses and mortality in a copepod Limnocalanus macrurus

Effects of household post-consumer plastics and tyre rubber on a Baltic Sea copepod Limnocalanus macrurus were assessed. Fragments of commercial recycled low-density polyethylene vegetable bags and rubber originating from recycled car tyres were incubated in seawater, and the copepods were exposed to the filtrate of the water. L. macrurus experienced erratic swimming behaviour and increased mortality in the filtrate of unwashed vegetable bags, containing elevated concentrations of alcohols, organic acids and copper. Responses of the antioxidant defence system (ADS) were recorded in copepods exposed to rubber treatments containing high concentrations of zinc. Significant responses in the ADS enzymes indicate that reactive oxygen species (ROS) formation was exceeding the detoxification capacity of the ADS which may further lead to prolonged state of oxidative stress. Observed effects of exposure on the biochemical level coincide with impaired swimming activity of the copepods, indicating possible irreversible cellular responses leading to behavioural changes and mortality.

Bioinspired ultra-low fouling coatings on medical devices to prevent device-associated infections and thrombosis

Addressing thrombosis and biofouling of indwelling medical devices within healthcare institutions is an ongoing problem. In this work, two types of ultra-low fouling surfaces (i.e., superhydrophobic and lubricant-infused slippery surfaces) were fabricated to enhance the biocompatibility of commercial medical grade silicone rubber (SR) tubes that are widely used in clinical care. The superhydrophobic (SH) coatings on the tubing substrates were successfully created by dip-coating in superhydrophobic paints consisting of polydimethylsiloxane (PDMS), perfluorosilane-coated hydrophobic zinc oxide (ZnO) and copper (Cu) nanoparticles (NPs) in tetrahydrofuran (THF). The SH surfaces were converted to lubricant-infused slippery (LIS) surfaces through the infusion of silicone oil. The anti-biofouling properties of the coatings were investigated by adsorption of platelets, whole blood coagulation, and biofilm formation in vitro. The results revealed that the LIS tubes possess superior resistance to clot formation and platelet adhesion than uncoated and SH tubes. In addition, bacterial adhesion was investigated over 7 days in a drip-flow bioreactor, where the SH-ZnO-Cu tube and its slippery counterpart significantly reduced bacterial adhesion and biofilm formation of Escherichia coli relative to control tubes (>5 log10 and >3 log10 reduction, respectively). The coatings also demonstrated good compatibility with fibroblast cells. Therefore, the proposed coatings may find potential applications in high-efficiency on-demand prevention of biofilm and thrombosis formation on medical devices to improve their biocompatibility and reduce the risk of complications from medical devices.

Optimal design of a commercial rubber isolator based on creep and creep-resistance analyses

Creep is a common important physical phenomenon in rubber material, which induces the instability of geometrical dimension and deteriorates the mechanical performances. The present work develops an optimal design approach of a commercial rubber isolator based on creep analysis. First and foremost, a nonlinear creep constitutive model of rubber material is established, which can capture the hyper-elastic and time-dependent creep behaviors. Complete mechanical and creep tests of rubber materials are conducted, and material parameters are identified according to the experimental data. Then, the parametric finite element model of a rubber isolator is established, with which the time-dependent creep analysis based on the proposed creep constitutive model is conducted. The accuracy of the numerical creep analysis is validated at material level and structural component level. For engineering application, a sensitivity analysis and optimization design for creep-resistance of the rubber isolator is developed by combing finite element simulation and optimization method. The results show that creep-resistance characteristics of the optimal rubber isolator is largely improved, which provides a long-term stable behavior in vibration attenuation. The proposed method may provide an efficient tool for predicting the creep performance and optimal analysis of other commercial rubber-base products.

Homemade non-Lahton catheter

A catheter can be made from an ordinary drainage tube. A cylinder with a height of 3-4 mm is cut out of rubber (for this, commercial pencil rubber bands or rubber plugs are good). and a diameter equal to the diameter of the inner lumen of the selected tube. Such a cylinder can be cut with a sharp scalpel; it is very convenient to cut it with a trocar tube of the corresponding lumen. This cylinder is immersed in rubber glue and left to dry.

Modeling the spatial characteristics of extrusion flow instabilities for styrene-butadiene rubbers: Investigating the influence of molecular weight distribution, molecular architecture, and temperature

The extrusion flow instabilities of three commercial styrene-butadiene rubbers (SBR) are investigated as a function of molecular weight distribution (MWD); molecular architecture (linear, branched); and temperature. The samples have multimodal MWD, with the main component being SBR and a low amount, less than 10 wt. %, of low-molecular weight hydrocarbons. Deviation from the Cox–Merz rule at high angular frequencies/shear rates becomes intense as the amount of medium-molecular weight component increases. Optical analysis is used to identify and quantify spatial surface distortions, specifically wavelength (λ) and height (h), of the different types of extrusion flow instabilities. Qualitative constitutive models are reviewed and used to fit the experimental data for the spatial characteristics of extrusion flow instability. The fitting parameters as obtained by the models are correlated with molecular properties of the materials. It is found that the characteristic spatial wavelength (λ) increases as the extrusion temperature decreases. Hence, the influence of temperature on the spatial characteristic wavelength is investigated and an Arrhenius behavior is observed.

Cost-Effective Marine Fender Design Using an Elastoplastic Support Element: An Investigation

Abstract This manuscript investigates the potential cost savings of installing a steel elastoplastic element in series, structurally, with a commercial rubber marine fender. Along with cost savings...

Can Rubber Crop Systems Recover Termite Diversity in Previously Degraded Pastures in the Colombian Amazon Region?

Livestock production extension in Amazon has caused deforestation and soil degradation, with negative consequences on diversity and environmental services. Recently, rubber crops have been established in deteriorated soils of the Colombian Amazon as an option to restore hectares of unproductive degraded pastures. Bioindicator insects, such as termites, have been used to assess soil quality and fertility restoration. This study evaluated differences in termite abundance, species richness, and community composition in three different rubber crop systems as an indirect way of evaluating soil diversity restoring. Three rubber crop systems were sampled: clonal fields (rubber monocultures with different rubber clones), traditional commercial rubber plantations (rubber monocultures with just one rubber clone), and mixed plantations (rubber fields intercropped with copoazú fruit trees). Additionally, pastures in use for livestock production and natural forest relicts were compared to rubber crop systems, to serve as reference habitats. Termites were sampled using a 105-m transect method. Alpha diversity and beta diversity were estimated and compared between rubber crops and reference habitats. A total of 80 termite species belonging to two families were collected. Mixed plantations and pastures presented the lowest diversity rates. Species richness in rubber crop systems was 39% higher than that in pastures and included 72% of the termite species found in natural forests. Indicator species analysis associated soil-feeding termites with less diverse habitats and wood-feeding termites with high diverse habitats. Our results demonstrate that termite recovery will depend on the farming system selected and the agricultural practices implemented in the field, with some rubber crop systems, like commercial rubber plantations and clonal fields, recovering termite diversity better than others, such as mixed plantations.

Analysis model of restoring force of a rubber air spring

Not only has the dynamic stiffness of a rubber air spring been inherited by effects of the compressed air, but it has also been affected by hysteresis behaviors caused by the friction, viscoelasticity of bellow material. Hence, this paper will analyze comprehensively the stiffness model of a commercial rubber air spring. One of the first works is to predict the structure parameters including effective area, volume and their change rate. Then, the restoring force generated by compressed air will be analyzed and built through the theory of thermodynamics. The hysteresis model of the rubber bellow will be obtained based on the Berg’s frictional model connecting in parallel with fractional Kelvin-Voigt model. Next, an experimental apparatus is set up to identify the parameters of this model as well as evaluate the proposed restoring force model of the rubber air spring. The study results show that the analysis model of the rubber air spring matches well the measured data. This work will offer a helpful insight in the design of the vibration isolation system using rubber air springs as elastic elements.

Evaluation of grasp capability of a gripper driven by optimal spherical mechanism

This paper evaluates grasp capability of a new three-fingered gripper driven by optimal spherical four-link mechanism design. The optimal mechanism provided a trajectory that is approximately a grate circle arc. Therefore, independently driven three fingers of prototype either surround or compress an object with only one degree of freedom for each finger. Thus, the gripper provided both force-closure and form-closure grasp. The force variation of fingertip along the trajectory was presented comparative to calculations for 32 static cases of grasped cylindrical objects. Regression analysis between calculated values and measured data showed %99 reliability. The mechanism provided contact force between 155-215 N along the trajectory. The lifting load capability of the gripper without slip on ceramic surface with low friction was measured by using a commercial single side rubber band on the fingertips. 9 ± 0.05 kg lift capability for cylindrical objects without slip was observed. The prototype was tested for 11 grasp operations and 8 objects with various geometry. Each of the test showed success in the first grasp trial.

Recyclable crosslinked elastomer based on dynamic dithioacetals

Recent progress in introducing elegant dynamic covalent bonds into covalently crosslinked networks enabled the trade-offs between chemical crosslinking and recycling. Thus far, continuous efforts are made to exploit new dynamic chemistries to address the constrains of intricate preparation procedures and need of catalyst additives in creating dynamic covalent networks. In this work, we report an industrially feasible process to prepare catalyst-free malleable elastomers by engineering dithioacetals as the dynamic motifs into a commercial diene rubber. Specifically, a dithioacetal-containing diacid (BTA) is synthesized and used as a novel crosslinker for epoxidized natural rubber (ENR), by which dynamic dithioacetals are introduced into the elastomeric networks. Small molecule model study shows that dithioacetal exchange can be conducted at elevated temperature without catalyst. In the BTA crosslinked ENR, the thermoactivated dithioacetal exchange reactions can alter its network topologies in an associative pathway and confer it with remarkable reprocessability. The mechanical properties and relaxation rate of the networks can be readily manipulated by varying the dithioacetal concentration.

Giant barocaloric effect in commercial polyurethane

Barocaloric effect in polymers is barely recognized and limited to a few reports in the literature. This effect consists of a thermal response of the material when a hydrostatic pressure is applied, allowing its application in the field of solid-state cooling. In this study, the barocaloric effect was investigated for a commercial polyurethane rubber (PU) subjected to three heat treatment temperatures (60, 100, and 115 °C) for 16 h to assess the limiting condition for this application. PU presents giant barocaloric effect, reaching adiabatic temperature change between 13 and 15 °C at a maximum pressure variation of 218 MPa, obtained under direct measurement, reaching a normalized refrigerant capacity of 11.07 kJ kg−1 GPa−1 (ΔTh-c = 25 °C, Δp = 174 MPa). Using the obtained data, it was possible to propose a quadratic model to predict the value of the adiabatic temperature variation as a function of the temperature and pressure applied in the PU. The PU characterization included differential scanning calorimetry and mechanical properties. The results obtained indicate a promising research field for the barocaloric effect in rubber polyurethanes.

Experimental study of adhesively bonded natural fibre composite – steel hybrid laminates

Natural fibre composites (NFC), such as flax fibre reinforced plastics are green material with good specific properties. Significant research is currently in progress to improve the mechanical properties and durability of these composites and to make them competitive to traditional synthetic composites. A multi-material design approach is proposed in this study to develop a novel hybrid structure with a thin metal layer adhesively bonded to NFC. Two adhesives; a commercial epoxy adhesive and natural rubber were used for the adhesion between a stainless steel layer and flax composite with thermoset and thermoplastic matrix. The performance of the hybrid joint was investigated using a single lap joint (SLJ) test supported by full-field displacement measurement methods. The manufacturing of the composite specimen and the bonding of the NFC – metal joint with rubber adhesive was demonstrated. The force displacement curves from the SLJ test showed that the bonded joint with epoxy adhesive was stronger in comparison to the bonding with natural rubber. It is supported by the adherend failure observed in the joint with epoxy adhesive, while the rubber joint showed adhesive failure. The key outcome of the research is that the viability of adhesively bonded NFC - metal hybrid is established.

An Investigation on the Thermally Induced Compatibilization of SBR and α-Methylstyrene/Styrene Resin.

The miscibility between two polymers such as rubbers and performance resins is crucial to achieve given targeted properties in terms of tire performances. To this aim, α-methylstyrene/styrene resin (poly(αMSt-co-St)) are used to modify the viscoelastic behavior of rubbers and to fulfill the requirements of the final applications. The initial aim of this work was to understand the influence of poly(αMSt-co-St) resins blended at different concentrations in a commercial styrene-butadiene rubber (SBR). Interestingly, while studying the viscoelastic properties of SBR blends with poly(αMSt-co-St), crosslinking of the rubber was observed under conditions where it was not expected to happen. Surprisingly, after the crosslinking reactions, the poly(αMSt-co-St) resin was irreversibly miscible with SBR at concentrations far above its immiscibility threshold. A detailed investigation involving characterization technics including solid state nuclear magnetic resonance led to the conclusion that poly(αMSt-co-St) is depolymerizing under heating and can graft onto the chains of SBR. It results in an irreversible compatibilization mechanism between the rubber and the resin.

Design of polymeric binders to improve the properties of magnesium phosphate cement

In the context of reducing the environmental impact of cement manufacturing, magnesium phosphate cements raise interest as alternative binders in construction, for immobilization of wastes, and recycling purposes. Their use in applications is somehow limited by short setting time, brittleness and low water resistance; this calls for the use of additives. Two polymer additives were designed adopting emulsion polymerization, an environmentally friendly solution to make available polymers as water-based latex dispersions. The composites containing 5 wt% of polymer, exhibited better elastic behaviour, with up to twice the toughness of the reference sample and of a sample produced with commercial styrene-butadiene rubber latex. Moreover, the additives reduced the apparent porosity, promoted phosphate crystallization, modified the size and shape of crystals, and effectively retarded the reaction, extending working time. The acrylic emulsion developing keto-hydrazide self-crosslinking reaction imparted better properties to the composite, thanks to the synergistic effect with the MPC setting reaction.

Treasuring waste lignin as superior reinforcing filler in high cis-polybutadiene rubber: A direct comparative study with standard reinforcing silica and carbon black

There has been ever raising concern in last few decades about the utilization of biomass for different commercial applications such as filler materials in rubber composites. In this context, an interesting pathway has been proposed to develop such composites by introducing waste lignin as a reinforcing constituent in high cis-polybutadiene rubber (BR). With a judicious selection of rubber curing ingredients and, simultaneously, adopting suitable solid-state mixing protocols, particularly, a relatively high-temperature multi-steps melt-mixing process (above the glass transition temperature of lignin), rubber composites with an outstanding mechanical performance were prepared. The reinforced rubber composites with 50 (weight) parts lignin loading per hundred parts of rubber (phr) offer ∼10 MPa tensile strength (TS), ∼276% elongation at break (EB), and ∼3.51 MPa tensile stress at 100% elongation (so-called rubber modulus M100). These values are superior when compared with the composites comprised with standard reinforcing carbon black (∼8.5 TS, ∼224% EB, ∼2.79 M100) and even with a silica-silane system (∼7.34 TS, ∼229% EB, ∼2.44 M100) with same filler loading. The unique combination of the curing packages and four-stage mixing process allowed us to establish a homogeneous and fine dispersion of lignin. Furthermore, this is the first time that available models of rubber reinforcement are applied to the description of the reinforcement mechanisms of lignin in a soft elastomer involving various aspects like filler-filler interaction, rubber-filler interactions, critical strains for destroying the filler-filler network, effective filler volume fractions, shape factor, etc. The developed compounding methods for BR and their characterization and modeling can be easily applied to other commercial rubbers facilitating a real breakthrough in developing cheap and bio-based high-performance rubber composites.

Toughening, recyclable and healable nitrile rubber based on multi-coordination crosslink networks after “tetrazine click” reaction

The recycling and self-healing functions of commercial rubber are of great significance in the field of sustainable materials. So far, manufacturing such rubber with excellent strength and toughness was still a huge challenge. Herein, the multi-coordination crosslink networks were designed to achieve this goal. First, the nitrile-butadiene rubber (NBR) was modified through 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (DPT) click reaction to introduce the second ligand group. Next, the blend of modified NBR and metal salt (including ZnCl2 and CoCl2) was hot-pressed to form the metal-nitrile and metal-pyridine (nitrogen-containing heterocyclic groups) coordination bonds. The designed composite had ultra-high mechanical strength and toughness at the same time. Compared with the NBR/ZnCl2 composite, the tensile strength of NBR-DPT4-Zn10 composite with multi- coordination bonds was improved by 7.5-fold (from 5.5 MPa to 46.82 MPa), and the corresponding fracture energy was improved by 142% (from 26.2 MJ m−3 to 63.5 MJ m−3). At the same time, the high recyclable and heat-healing efficiency were obtained. These achievements are expected to develop commercial rubber’s recyclability and high mechanical properties.

A conductive rubber with self‐healing ability enabled by metal‐ligand coordination

AbstractAt present, flexible conductive materials have been widely noticed. However, developing electronic materials with both good mechanical and electrical self‐healing abilities remains both a great challenge and an exciting goal. Herein, we prepared a commercial nitrile butadiene rubber (NBR) with electrical healing capability based on constructing Fe(III) coordination and CNT networks. With 3 phr (parts per hundreds of rubber) CNT, the tensile strength and the elongation at break of rubber composite reached 1.1 MPa and 300%, respectively. After healing at 80°C for 9 hours, the recovery efficiency of rubber composite achieved 90%. After adding 5 phr CNT, the conductivity can reach 0.077 S/m, and the electrical conductivity was 0.076 S/m after self‐healing. Such material can maintain resistance change within 5 times at high strain (100%), so it is applicable in the field of strain sensor.

Iron (III) cross-linked thermoplastic nitrile butadiene elastomer with temperature-adaptable self-healing property

Fe cross-linked thermoplastic carboxylated nitrile butadiene rubber (XNBR) materials using Fe-COOH coordination as dynamic cross-links are reported. The transparent and brown Fe cross-linked XNBR (Fe/XNBR) elastomer was prepared by drying of Fe/XNBR organogels, which were fabricated by simple mixing of Fe3+ ethanol solution and XNBR dioxane solution. Tensile tests showed that only a small amount of Fe3+ ions (e.g., COOH/Fe=1/0.086, mol/mol) made the Fe/XNBR had even better tensile strength and stretchability than 2 phr sulphur vulcanized XNBR. Dynamic mechanical analysis demonstrated that the Fe-COOH interaction not only increased the moduli at higher temperatures, but also made the glass transition temperature high-temperature-shifted. In-situ infrared spectra measurements suggested that higher temperatures (e.g, 100°C) generated more trifunctional Fe-COOH cross-links and made the Fe-COOH interaction highly dynamic. The dynamic nature of the Fe-COOH interaction and generation of more trifunctional cross-links at high temperatures endowed fast self-healing and re-molding properties to the Fe/XNBR elastomers. Our result as a proof-of-concept illustrated a simple and cost-efficient way to fabricate self-healable thermoplastic elastomers using metal-ligand coordination in commercial rubbers.