Rubber Chemistry and Technology最新文献

Styrene–butadiene–styrene (SBS) rubbers are one of the most frequently used thermoplastic elastomers globally. The upper operating temperature of SBS is limited by the glass transition temperature (T_g) of poly(styrene) (PS), circa 100 °C. This study demonstrates a noteworthy enhancement in the properties of SBSs by introducing a diblock copolymer consisting of styrene and α-methylene-γ-butyrolactone (α-MBL). Polymers derived from α-MBL exhibit exceptional thermal stability, attributable to a T_g of 195 °C. Notably, α-MBL, also recognized as Tulipalin A, is a biorenewable compound naturally found in tulips. This investigation encompasses both crosslinked and noncrosslinked blends of poly(styrene)-block-poly(α-methylene-γ-butyrolactone) diblock copolymer (PS-b-PMBL) and poly(styrene)-block-poly(butadiene)-block-poly(styrene) triblock copolymer, within the 0–20 wt% PS-b-PMBL range. Thorough examination using thermal analysis and linear shear rheology reveals that all blends surpass the properties of their pure SBS counterparts. Specifically, blending at 200 °C induces crosslinking between the polymers, yielding heightened Young’s modulus and complex viscosity, thereby resulting in a robust and rigid material compared with noncrosslinked blends. For noncrosslinked blends, an increase in strength is observed while maintaining commendable rubbery properties. Notably, the noncrosslinked blends permit the recycling of components (SBS and PS-b-PMBL) through the redissolving of rubber in tetrahydrofuran. These findings present a promising avenue for the enhancement of rubbers through the incorporation of biorenewable compounds.

The recycling of waste rubber is very important for environmental protection, but the compatibility problem restricts the recycling and application of waste rubber powder (WRP). Devulcanization of WRP has been proven to be an effective method to improve the solubilization effect. The use of environmentally friendly nontoxic solvents can not only improve the devulcanization effect but also avoid secondary pollution. Thus, in this article, an environmentally friendly deep eutectic solvent (DES) is first prepared and then applied to the devulcanization treatment of WRP. The results show that the prepared DES has a positive devulcanization effect, and the devulcanization rate can reach 50%. The devulcanization mechanism can be divided into two aspects: (1) adsorption and removal of sulfur-containing low-molecular compounds and (2) destruction of the crosslinking structure and improvement of fluidity. Observation of the microstructure showed that the rougher the surface of the desulfurized rubber powder, the more conducive to the crosslinking reaction with the matrix material to form a uniform whole. The devulcanization mechanism of DES is divided into destroying the sulfur-containing cross-linked structure and adsorbing the sulfur-containing low-molecular compounds. The surface of WRP after DES treatment is rougher and more porous, which is beneficial to the crosslinking reaction with the matrix material. Finally, the optimum process conditions for the de-crosslinking effect are determined by orthogonal test as follows: liquid-solid ratio 15∶1, temperature 120°C, time 0.5 h.

Rubbers and elastomers have a rich history that spans many eras of human civilization dating back to 1600 AD. Upon their introduction into Europe, they became common materials in shoes and fabrics. With the invention of vulcanization by Charles Goodyear in 1839, rubbers became widely used in many new applications, ranging from tires to industrial machine parts. Today, rubbers and elastomers are essential in the development of innovative, emerging technologies. This review exemplifies how rubbers and elastomers have been used to advance the emerging fields of soft robotics through soft grippers and dielectric elastomer actuators, stretchable and wearable devices through conductive elastomers and smart elastomers used in thermal camouflage and sensors, biomedical applications through tissue scaffolding and stretch-triggered drug delivery, and energy harvesting through piezoelectric elastomers and wave harvesting triboelectric nanogenerators. This review also briefly summarizes other developments in these fields as well as glimpses into other emerging fields that are advancing through the incorporation of rubbers and elastomers.

Rubber-based polymers with high carbon black content can be three-dimensionally (3D) printed using the additive manufacturing of elastomers process. However, high-viscosity materials limit printing resolution, making it difficult to produce fine structures and high-precision parts, especially two-component (2K) parts. The viscosity of a rubber compound used for rod seal applications was reduced and adjusted using Nipol® 1312 liquid rubber and the alkyl sulfonic phenyl ester Mesamoll® II as plasticizers to lower the torque level during extrusion when a reduced nozzle diameter of 0.4 mm is used in 3D printing. In addition, the flowability of the compound was enhanced prior to vulcanization of the part, which could increase the layer–layer bond and thus reduce the mechanical anisotropy typically induced by fused filament fabrication. Using a viscosity-optimized rubber compound, a 2K rod seal consisting of a thermoplastic polyurethane with elastomeric properties and an acrylonitrile rubber-based O-ring was produced and dynamically tested for leakage.

This work addresses the critical technological challenge of producing butadiene-based synthetic rubbers with the required skid resistance through anionic polymerizations at positive temperatures. The effects of adding different polar modifiers—bis[2-(N,N-dimethylamino)ethyl] ether (BDMAE), ditetrahydrofurylpropane, tetramethylethylenediamine, sodium stearate, sodium palmitate, and sodium tert-amilate—into the monomer feed in anionic solution polymerizations of 1,3-butadiene are investigated. Different feed concentrations and combinations of polar modifiers were tested to achieve high yields and vinyl contents with initial temperature of 40 °C. The reactions were evaluated according to the obtained temperature and pressure profiles and physico-chemical characterizations of the obtained polymer, with the aid of statistical analyses. The results clearly showed the positive effects of using polar modifiers in the feed. Particularly, the combination of BDMAE and sodium salts provided products with high vinyl contents (>50 mol%) with high yields (>80 wt%), leading to high temperature peaks (>90 °C), as desired to enhance skid resistance. Moreover, the performed statistical analyses and proposed mathematical modeling revealed the existence of multivariate and complex correlations among the analyzed process variables. The findings from this investigation can be pivotal for advancing industrial applications in the production of skid-resistant synthetic rubber.

Rubber engineering design analysis requires a fundamental understanding of the mechanical behavior of polymers, especially in their unvulcanized state. It necessitates the establishment of a three-dimensional constitutive material to account for the observed mechanical behavior. This law is required to produce realistic descriptions of the viscoelastic performance in a mathematically simple form that is easy to implement in engineering applications. This article describes the theory of the Tschoegl–Chang–Bloch time-dependent nonlinear viscoelastic constitutive law. The experimental verification of this law is provided under different deformation fields and multiple load steps. Laboratory test procedures to obtain the parameters required to describe the material under consideration are provided in detail. A recursive form of the constitutive law, suitable for finite element application, is derived and coded in the finite element commercial code Abaqus via the user subroutine UMAT. Comparisons between the experimental observations, the theoretical results, and the numerical data are drawn for simple test models examined under creep or shear relaxation conditions. The excellent agreements observed indicate the suitability of the governing law in analyzing viscoelastic problems of unvulcanized carbon black–filled rubbers.

The sulfide polymers of variable and controlled sulfur content, obtained by anionic copolymerization of elemental sulfur and thiiranes (styrene sulfide and cyclohexene sulfide), were applied as curatives (sulfur donors) in the vulcanization process of styrene–butadiene rubber. The activity of polysulfides as curatives was investigated based on rheometric measurements of the vulcanization process and calculations of curing parameters using kinetic data. The crosslink density and structure related to the mechanical properties of the vulcanizates under static and dynamic conditions were studied. The overall suitability of polysulfides as crosslinking agents for diene rubbers was investigated.

Decades of elastomeric fracture phenomenology resulting from the work of Thomas and Smith demonstrated the remarkable fact that rubbers are stronger and tougher at lower temperatures. The prevailing explanation relates the fracture behavior to polymer viscoelasticity. Given the recent insight and evidence that toughness is influenced by material strength, we examine elastomeric fracture with a different perspective and conclude that chain scission dictates fracture characteristics, including its temperature dependence. Working within selected temperature ranges, stretching is shown to be entirely elastic at a stretching rate less than 0.17 s⁻¹. We demonstrate that the same temperature and rate dependencies of strength and toughness, observed by Thomas and Smith, also occur in our crosslinked polybutadiene and styrene–butadiene rubber. The temperature effects on rate dependence of strength and toughness are found to be much stronger than that prescribed by the Williams–Landel–Ferry shift factor a_T. Moreover, crack propagates, upon either stepwise stretching or during creep, at a much lower speed at lower temperature that cannot be rationalized with polymer relaxation dynamics. Our new interpretation is that a carbon–carbon bond is stronger at a lower temperature. Because backbone bonds are more stable, a higher degree of network stretching occurs before rupture at lower temperatures.