Catalytic and networking effects of carbon black on the kinetics and conversion of sulfur vulcanization in styrene butadiene rubber

Effect of Butadiene Rubber Crystallization on Low-Temperature Properties of Butadiene/Silicone Rubber Blends with Potential for Mars Applications

This study explores the impact of butadiene rubber (BR) crystallization on the low-temperature properties of butadiene/silicone (VMQ) rubber blends (BR/VMQ) designed for Martian applications. Two types of BR, semi-crystalline high-cis Buna CB24 and amorphous Buna CB550, were blended with VMQ, and their mechanical and thermal properties were evaluated. Kinetics of vulcanization, static mechanical properties, dynamical mechanical analysis, thermal shrinkage, and differential scanning calorimetry were utilized. The research demonstrates that the semi-crystalline BR improves mechanical properties but induces greater shrinkage at low temperatures. Conversely, using amorphous BR provided more consistent mechanical properties across the Martian temperature range and reduced material shrink by 6.71% for samples with carbon black, by 8.36% for samples with silica, and by 11.63% for unfilled samples. Future research will be required to evaluate the impact of volume change on the sealing properties of the BR/VMQ blends.

Effect of Fillers Modification with ILs on Fillers Textural Properties: Thermal Properties of SBR Composites

In this work, we present the effect of graphene nanoplatelets (GnPs) modification with ionic liquids (ILs). The textural properties of graphene nanoplatelets (GnPs) used as styrene-butadiene rubber's filler and the thermal properties of the composites obtained with the use of the mentioned fillers were investigated. GnPs were modified with 1-butylpyridinium bromide (BPyBr) and 4-methyl-1-butylpyridinium bromide (BmPyBr) through two different ways. One strategy has been to deposit the filler modifier from the solution. The second one involved the modification of the filler with ionic liquids in bulk during the preparation of elastomer blends. Settlement of the proposed ionic liquids onto the GnPs' surface led to significant changes in the textural characteristics. BPyBr has restricted the filler's microporosity, whereas BmPyBr has caused the formation of a more opened filler structure without the increase in its average pore size. GnPs modified with ILs led to reducing the temperature of vulcanization of SBR compounds and affected the thermal stability of the composites.

Networking Skills: The Effect of Graphene on the Crosslinking of Natural Rubber Nanocomposites with Sulfur and Peroxide Systems

Tailored crosslinking in elastomers is crucial for their technical applications. The incorporation of nanoparticles with high surface-to-volume ratios not only leads to the formation of physical networks and influences the ultimate performance of nanocomposites, but it also affects the chemical crosslinking reactions. The influence of few-layer graphene (FLG) on the crosslinking behavior of natural rubber is investigated. Four different curing systems, two sulfur-based with different accelerator-to-sulfur ratios, and two peroxide-based with different peroxide concentrations, are combined with different FLG contents. Using differential scanning calorimetry (DSC), vulcametry (MDR) and swelling measurements, the results show an accelerating effect of FLG on the kinetics of the sulfur-based curing systems, with an exothermic reaction peak in DSC shifted to lower temperatures and lower scorch and curing times in the MDR. While a higher accelerator-to-sulfur ratio in combination with FLG leads to reduced crosslinking densities, the peroxide crosslinkers are hardly affected by the presence of FLG. The good agreement of crosslink densities obtained from the swelling behavior confirms the suitability of vulcameter measurements for monitoring the complex vulcanization process of such nanocomposite systems in a simple and efficient way. The reinforcing effect of FLG shows the highest relative improvements in weakly crosslinked nanocomposites.

The Process of Natural and Styrene–Butadiene Rubbers Biodegradation by Lactobacillus plantarum

The ability of Lactobacillus plantarum to degrade different mixtures of styrene–butadiene and natural rubbers was investigated. In experiments, 12 various compositions of rubber waste mixtures were investigated. Lactobacillus plantarum cultivation was carried out in a medium with the addition of individual mixtures at the temperature of 30 °C for 14 days. The presence of cellulose on the surface of bioreactors indicated the activity of bacteria. After cultivation, the rubber mixtures were tested again. Analyses of the elemental composition and mass balance of waste were carried out. The experiments showed that the culture media supplemented by various natural rubber mixtures allowed bacteria to produce bacterial cellulose. The mean thickness of bacterial cellulose was 3–6 mm after 14 days of culturing. In samples where the cellulose appeared, about 4% average mass loss was observed. The average carbon content in the rubber material used as the carbon source for bacteria, before the culture process, was about 89.07–95.40%. After 14 days of culturing, the carbon content was reduced from 31.15% to 56.45–65.7%.

Preparation and application of carbon black-filled rubber composite modified with a multi-functional silane coupling agent

Carbon black (CB)-filled rubber composites are widely used for tire tread and other rubber products due to their good abrasion resistance and reinforcement. Numerous studies have been focused on the filler-rubber interaction with the aim of obtaining optimum performances. In order to investigate the effect of modification on properties of diene rubber composites, a modified CB-filled isoprene rubber (IR) composite was prepared with a multi-functional silane coupling agent, 2-aminoethyl-2-(3-triethoxysilylpropyl)aminoethyl disulfide (ATD). This modification significantly enhanced the CB-IR interaction and improved CB dispersion. For the modified CB/IR vulcanizates, the tensile strength, stress at 300% elongation, temperature rise, and dynamic loss coefficient were significantly improved at low ATD dosage (1.5 phr). Such modification provides an effective route to prepare CB-reinforced diene rubber composites with low hysteresis and improved mechanical properties.

Upcycling Waste Polyethylene into Carbon Nanomaterial Via A Carbon-Grown-On-Carbon Strategy

Upcycling waste plastics (e.g., polyethylene (PE)) into value-added carbon products is regarded as a promising approach to address the increasingly serious waste plastic pollution and simultaneously achieve carbon neutrality. However, developing new carbonization technology routes to promote the oxidation of PE at low temperature and construct the stable crosslinking network remains challenging. Here, we propose a facile carbon-grown-on-carbon strategy using carbon black (CB) to convert waste PE into core/shell carbon nanoparticles (CN) in high yields at low temperature. The yield of CN remarkably rises when the heating temperature decreases or the dosage of CB grows. The obtained CN displays turbostratic structure and closely aggregated granular morphology with a size of ca. 80 nm. It is found, prior to the oxidation and carbonization of PE, CB forms a 3D network architecture in the PE matrix. More importantly, CB not only catalyzes the partial oxidation of PE to form PE macromolecular radicals and introduce oxygen-containing groups at low temperature in the early stage, but also favors for the construction of a stable crosslinking network in the latter stage. This work offers a facile sustainable strategy for chemical upcycling of PE into value-added carbon products without post-treatments or usage of metallic catalysts. This article is protected by copyright. All rights reserved.

Novel Approaches to In-Situ ATR-FTIR Spectroscopy and Spectroscopic Imaging for Real-Time Simultaneous Monitoring Curing Reaction and Diffusion of the Curing Agent at Rubber Nanocomposite Surface

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements.

Nature of Carbon Black Reinforcement of Rubber: Perspective on the Original Polymer Nanocomposite

Adding carbon black (CB) particles to elastomeric polymers is essential to the successful industrial use of rubber in many applications, and the mechanical reinforcing effect of CB in rubber has been studied for nearly 100 years. Despite these many decades of investigations, the origin of stiffness enhancement of elastomers from incorporating nanometer-scale CB particles is still debated. It is not universally accepted whether the interactions between polymer chains and CB surfaces are purely physical adsorption or whether some polymer-particle chemical bonds are also introduced in the process of mixing and curing the CB-filled rubber compounds. We review key experimental observations of rubber reinforced with CB, including the finding that heat treatment of CB can greatly reduce the filler reinforcement effect in rubber. The details of the particle morphology and surface chemistry are described to give insights into the nature of the CB-elastomer interfaces. This is followed by a discussion of rubber processing effects, the influence of CB on crosslinking, and various chemical modification approaches that have been employed to improve polymer-filler interactions and reinforcement. Finally, we contrast various models that have been proposed for rationalizing the CB reinforcement of elastomers.

Isostructural softening of vulcanized nanocomposites

Following previous work evidencing that short poly-propylene glycol (PPG) chains incorporated into crude SBR/silica nanocomposites act as filler-network softeners without changing their structure, we propose in the present report to examine more operative cross-linked materials. We first evidence that the adsorption of PPG onto silica deactivates progressively the particle's catalytic effect on vulcanization, without perturbing however the cross-link density distribution that we investigate through multiple-quantum NMR. In addition, electron microscopy confirms that the silica structure is conserved after vulcanization and that it does not depend on the PPG content either. Composites containing various amounts of PPG can thus be seen as structurally identical, both from a matrix and filler point of view - which is confirmed by small and medium amplitude oscillation shear rheology showing strikingly identical viscoelastic properties. The PPG signature only appears above 100% in tensile deformation where it is observed to soften dramatically the filler network. Our discovery makes it consequently possible to decorrelate the mechanical behavior of reinforced rubbers under normal conditions of use and urgent needs of energy dissipation.

Development of functionalized core-shell nanohybrid/synthetic rubber nanocomposites with enhanced performance

Regulating the interfacial interaction between fillers and matrices is crucial for fabricating high-performance polymer composites. In this research, a functionalized core-shell hybrid silica@graphene oxide was produced by the charge attraction method, and then added to a trans-1,4-polyisoprene matrix as a neoteric filler to obtain a brand-new silica@graphene oxide/trans-1,4-polyisoprene polymer nanocomposite. The hybrid incorporation simultaneously improved the fracture toughness, mechanical strength and heat resistance of the nanocomposites. We examined the thermal, mechanical and shape memory properties of the nanocomposites via methodical measurements from the microscale to the macroscale. The experimental results demonstrated that, compared with other samples, the nanocomposite sample with 1.0 wt% silica@graphene oxide exhibited the best mechanical and thermal performance, and the fabricated nanocomposites showed good shape memory properties. This new and feasible approach is likely to enable a new strategy for the design of interfaces for developing nanocomposites with high performance.