Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler-Part II: Mechanical, Thermal and Ageing (Chemical) Properties

Natural rubber composites were reinforced by the co-fillers 'hydrochar' (HC), obtained by hydrothermal carbonization of hardwood sawdust and commercial carbon black (CB). The content of the combined fillers was kept constant while their ratio was varied. The aim was to test the suitability of HC as a partial filler in natural rubber. Due to its larger particle size and hence smaller specific surface area, large amounts of HC reduced the crosslinking density in the composites. On the other hand, due to its unsaturated organic character, HC was found to display interesting chemical effects: if it was used as the exclusive filler component, it displayed a very strong anti-oxidizing effect, which greatly stabilized the rubber composite against oxidative crosslinking (and hence embrittlement). HC also affected the vulcanization kinetics in different ways, depending on the HC/CB ratio. Composites with HC/CB ratios 20/30 and 10/40 displayed interesting chemical stabilization in combination with fairly good mechanical properties. The performed analyses included vulcanization kinetics, tensile properties, determination of density of permanent and reversible crosslinking in dry and swollen states, chemical stability tests including TGA, thermo-oxidative aging tests in air at 180 °C, simulated weathering in real use conditions ('Florida test'), and thermo-mechanical analyses of degraded samples. Generally, the results indicate that HC could be a promising filler material due to its specific reactivity.

ESBR Nanocomposites Filled with Monodisperse Silica Modified with Si747: The Effects of Amount and pH on Performance

To prepare silica/rubber composites for low roll resistance tires, a novel strategy was proposed in this study, in which autonomous monodisperse silica (AS) was prepared and modified using 3-mercaptopropyloxy-methoxyl-bis(nonane-pentaethoxy) siloxane (Si747), after which silica/emulsion styrene butadiene rubber (ESBR) master batches were produced using the latex compounding technique. Meanwhile, the commercial precipitated silica (PS) was introduced as a control. In this study, the effects of amount of Si747 and pH value on the properties of the silica/ESBR composites were systematically analyzed. Thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) results indicated that Si747 reduced the silanol group by chemical grafting and physical shielding, and the optimum amounts of Si747 for AS and PS modification were confirmed to be 15% and 20%, respectively. Under a pH of 9, ESBR/modified AS (MAS) composites with 15% Si747 presented better silica dispersion and a weaker Payne effect, compared with ESBR/modified PS (MPS) composites with 20% Si747. Meanwhile, in terms of dynamic properties, the ESBR/MAS composites exhibited a better balance of lower rolling resistance and higher wet skid resistance than the ESBR/MPS composites.

Investigation on in situ silica dispersed in natural rubber latex matrix combined with spray sputtering technology

In this study, different processes are performed for the preparation of natural rubber latex (NRL)/silica composites. A novel approach is to use spray sputtering technology combined with in situ method to improve the dispersion of silica in rubber latex matrix and further improve the properties of vulcanizates. Results show that in situ silica in rubber matrix prepared from NH4Cl and Na2SiO3 has better Payen effect than other processes. Meanwhile, when the in situ silica reached 10 phr in the rubber matrix, the dosage can suitably match the dispersion capacity of the spray sputtering process with superior comprehensive mechanical properties. Compared with the traditional precipitation method, the tensile strength and tear strength of the silica/NR composites prepared by spray sputtering technology combined with in situ method were increased by 34.7% and 19.7%.

EMERGING ADVANCES IN RUBBER TECHNOLOGY BY THE SUITABLE APPLICATION OF SOL-GEL SCIENCE AND TECHNOLOGY

In recent years, the application of sol-gel science to industrial polymer research has offered advancements in rubber technology. The use of sol-gel–synthesized materials for the development of highly reinforced rubber composites is the most commonly adopted and popular method exercised by rubber scientists. This article comprehensively reviews the recent progress regarding preparation and properties of sol-gel–synthesized nanoparticles-based rubber composites. The pragmatic consequences of sol-gel–synthesized nanoparticles in rubber compounds are systematically described through rheological, mechanical, and thermal properties. Emphatic focus is given to understanding the reinforcement mechanism of rubber composites by the use of sol-gel–derived alkoxide silica as filler. The properties of rubber nanocomposites are usually dependent on the dispersion of sol-gel–synthesized nanoparticles into the rubber matrix. The results reviewed from prolific studies suggested that sol-gel science has tremendous potential to develop high performance rubber nanocomposites for future industrial application.

Unveiling the hybrid interface in polymer nanocomposites enclosing silsesquioxanes with tunable molecular structure: Spectroscopic, thermal and mechanical properties

Organic-inorganic nanobuilding blocks (NBBs) based on silsesquioxanes (SSQs) have potential applications as nanofillers, thermal stabilizers, and rheological modifiers, which can improve thermomechanical properties of polymer hosts. The possibility to tune both siloxane structure and pendant groups can promote compatibilization and peculiar interactions with a plethora of polymers. However, the control on SSQs molecular architecture and functionalities is usually delicate and requires careful synthetic details. Moreover, investigating the influence of NBBs loading and structure on the hybrid interface and, in turn, on the polymer chains mobility and mechanical properties, may be challenging, especially for low-loaded materials. Herein, we describe the preparation and characterization of polybutadiene (PB) nanocomposites using as innovative fillers thiol-functionalized SSQs nanobuilding blocks (SH-NBBs), with both tailorable functionality and structure. Swelling experiments and, more clearly, solid-state NMR, enlightened a remarkable effect of SH-NBBs on the molecular structure and mobility of the polymeric chains, envisaging the occurrence of chemical interactions at the hybrid interface. Finally, thermal and DMTA analyses revealed that nanocomposites, even containing very low filler loadings (i.e. 1, 3 wt%), exhibited enhanced thermomechanical properties, which seem to be connected not only to the loading, but also to the peculiar cage or ladder-like architecture of SH-NBBs.

Improved mechanical properties and thermal degradation of low-temperature hydrogenated acrylonitrile butadiene rubber composites with poly(sodium methacrylate) nanowires

Complex phase structures including a lot of poly(sodium methacrylate) nanowires improved the mechanical properties and thermal stability of LTG-HNBR composites.

Improved understanding on the reinforcement of low-temperature hydrogenated nitrile butadiene rubber composites by in situ polymerization of unsaturated metal methacrylate: influences of salt cation

The morphology and chemical structure of poly(UMM) and the solubility of UMM induced by its cations have a remarkable impact on reinforcement of rubber matrices.

The filler-rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties

Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber.

Hybrid organic-inorganic colloidal composite 'sponges' via internal crosslinking

An effective method for the generation of hybrid organic-inorganic nanocomposite microparticles featuring controlled size and high structural stability is presented. In this process, an oil-in-water Pickering emulsion is formed using hydrophilic amine-functionalized silica nanoparticles. Covalent modification using a hydrophobic maleic anhydride copolymer then alters nanoparticle wettability during crosslinking, causing a core-shell to nanocomposite structural reorganization of the assemblies. The resulting porous nanocomposites maintain discrete microparticle structures and retain payloads in their oil phase even when incubated in competitive solvents such as ethanol.

Constitutive modeling of the viscoelastic mechanical response of foam rubber-like materials

The viscoelastic mechanical behavior of foam rubber-like materials under large deformation is studied using thermodynamic methods.

Controlled growth of in situ silica in a NR/CR blend by a solution sol–gel method and the studies of its composite properties

Controlled loading of in situ silica in NR/CR blend by solution sol–gel method for enhancing the reinforcement.

A novel non-aqueous sol-gel route for the in situ synthesis of high loaded silica-rubber nanocomposites

Silica-natural rubber nanocomposites were obtained through a novel non-aqueous in situ sol-gel synthesis, producing the amount of water necessary to induce the hydrolysis and condensation of a tetraethoxysilane precursor by esterification of formic acid with ethanol. The method allows the synthesis of low hydrophilic silica nanoparticles with ethoxy groups linked to the silica surface which enable the filler to be more dispersible in the hydrophobic rubber. Thus, high loaded silica composites (75 phr, parts per hundred rubber) were obtained without using any coupling agent. Transmission Electron Microscopy (TEM) showed that the silica nanoparticles are surrounded by rubber layers, which lower the direct interparticle contact in the filler-filler interaction. At the lowest silica loading (up to 30 phr) silica particles are isolated in rubber and only at a large amount of filler (>60 phr) the interparticle distances decrease and a continuous percolative network, connected by thin polymer films, forms throughout the matrix. The dynamic-mechanical properties confirm that the strong reinforcement of the rubber composites is related to the network formation at high loading. Both the improvement of the particle dispersion and the enhancement of the silica loading are peculiar to the non-aqueous synthesis approach, making the method potentially interesting for the production of high-loaded silica-polymer nanocomposites.

Reinforcing efficiency and compatibilizing effect of sol–gel derived in situ silica for natural rubber/chloroprene rubber blends

The strong CR/in situ silica interaction causes filler accumulation at the interphase and enhances the compatibility and reinforcement in the NR/CR blend.

Amorphous silicon-carbon nanospheres synthesized by chemical vapor deposition using cheap methyltrichlorosilane as improved anode materials for Li-ion batteries

We report the preparation and characterization of amorphous silicon-carbon (Si-C) nanospheres as anode materials in Li-ion batteries. These nanospheres were synthesized by a chemical vapor deposition at 900 °C using methyltrichlorosilane (CH3SiCl3) as both the Si and C precursor, which is a cheap byproduct in the organosilane industry. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption, thermal gravimetric analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that the synthesized Si-C nanospheres composed of amorphous C (about 60 wt%) and Si (about 40 wt%) had a diameter of 400-600 nm and a surface area of 43.8 m(2) g(-1). Their charge capacities were 483.6, 331.7, 298.6, 180.6, and 344.2 mA h g(-1) at 50, 200, 500, 1000, and 50 mA g(-1) after 50 cycles, higher than that of the commercial graphite anode. The Si-C amorphous structure could absorb a large volume change of Si during Li insertion and extraction reactions and hinder the cracking or crumbling of the electrode, thus resulting in the improved reversible capacity and cycling stability. The work opens a new way to fabricate low cost Si-C anode materials for Li-ion batteries.