An in-depth understanding of surface modification of silica is critical for the development of high-performance green tires. In this work, silica was modified either with the silane coupling agent bis-(3-triethoxysilylpropyl)-tetrasulfide (TESPT) alone, or with a synergistic combination of TESPT/n-octyltriethoxysilane (OTES) and TESPT/hexamethyldisilazane (HMDS). TESPT-modified silica samples with varying degrees of surface modification were prepared, and the dual modification system achieved a higher degree of hydrophobicity than TESPT alone. Results indicated that surface grafting of silica significantly reduced curative adsorption, with N,N '-diphenylguanidine (DPG) exhibiting higher adsorption than N-cyclohexyl-2-benzothiazolesulfenamide (CBS); TESPT in combination with modifier led to a decrease in DPG adsorption. The effects of such silica surface grafting on the cure characteristics of solution styrene-butadiene rubber (SSBR) compounds and the mechanical properties of the resulting vulcanizates were systematically investigated. Enhanced surface modification led to increased total and chemical crosslink density, attributed to suppressed curative adsorption along with improved filler dispersion. Based on these findings, the effects of filler surface modification on the physical properties of the vulcanizates were further discussed and compared. Overall, the cure behavior and mechanical properties of silica-filled rubber compounds are strongly influenced by the surface chemistry of silica.
This work investigates the thermo-oxidative aging of three anonymized industrial natural-rubber-based tyre mixes subjected to circulating air at 75 degrees C for up to 21 days. Uniaxial tensile testing, dynamic mechanical analysis (DMA), oxygen elemental analysis using a CHNSO elemental analyzer and through-thickness nanoindentation were combined within a common aging protocol to compare bulk mechanical, viscoelastic, chemical, and spatially resolved aging signatures. Tensile testing showed that aging reduced rupture strain much more strongly than rupture stress, identifying loss of extensibility as the more sensitive tensile aging signature. DMA revealed formulation-dependent changes in stiffness, dissipation and frequency sensitivity, while CHNSO analysis showed progressive bulk oxygen uptake. Nanoindentation showed substantial aging-induced stiffening together with the development of surface-to-core mechanical heterogeneity. Importantly, within the present experimental dataset, the different aging descriptors did not provide identical formulation rankings. Mix C showed the greatest increase in average indentation reduced modulus, whereas Mix A developed the largest absolute surface-to-core modulus contrast. Bulk oxygen uptake and spatial stiffness heterogeneity therefore provide complementary rather than interchangeable information about thermo-oxidative aging. Overall, the results show that a single bulk property can obscure important differences in aging response and support a multimodal assessment based on extensibility, viscoelastic drift, oxygen uptake, and spatial stiffness heterogeneity.
Microcapsules are widely used in self-healing coatings, yet the mechanical contribution of the microcapsule shell to coating performance remains insufficiently understood. In this article, tung oil-loaded polyurethane/silica hybrid microcapsules (TO@PU/SiO2) were prepared by Pickering emulsion templating and compared with polyurethane microcapsules (TO@PU) to investigate the effect of capsule apparent stiffness on the mechanical and functional properties of epoxy coatings. The incorporation of surface-modified SiO2 nanoparticles into the polyurethane shell produced organic-inorganic hybrid microcapsules with enhanced resistance to localized deformation. The apparent Young's modulus of intact liquid-filled TO@PU/SiO2 microcapsules reached 1.23 +/- 0.16 GPa, approximately 4.4 times higher than that of TO@PU microcapsules (0.28 +/- 0.02 GPa). At an optimized loading of 5 wt.%, the TO@PU/SiO2(5)-EP coating exhibited an increased tensile strength of 3.18 +/- 0.11 MPa while maintaining favorable adhesion and Shore D hardness. Furthermore, its low-frequency impedance modulus remained above 10(7) Omega & centerdot;cm(2) after 21 days of immersion in 3.5 wt.% NaCl solution. After scratching, tung oil released from the ruptured microcapsules progressively sealed the damaged region, achieving a self-healing efficiency of 39.73% within 24 h. These results demonstrate that enhancing microcapsule apparent stiffness through SiO2 reinforcement contributes to improved coating mechanical integrity while maintaining effective corrosion protection and damage-triggered self-healing capability. This work highlights the dual function of stiffness-enhanced microcapsules as mechanical reinforcing components and healing-agent reservoirs, providing a strategy for designing mechanically robust self-healing anticorrosion coatings.
In order to reduce the polymerization temperature of conventional benzoxazines, three single-functional benzoxazines (TF-EBA, TF-FBA, and TF-PBA) containing trifluoroacetylamino groups were synthesized. The molecular structures of TF-EBA, TF-FBA and TF-PBAwereconfirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and protonNuclearMagnetic Resonance (1H NMR). The curing kinetics of the TF-BA resins were analyzed by Kissinger and Ozawa methods. The activation energies for the polymerization of TF-EBA were 80.80 and 84.70 kJ/mol, respectively, which were determined by the Kissinger and the Ozawa methods. The curing behavior was analyzed by Differential Scanning Calorimetry (DSC) and FTIR. After 170 degrees C/1 h + 200 degrees C/3 h heat treatment, the TF-BA resins were cured completely. Meanwhile, the thermal stability of TF-BA benzoxazine polymers was evaluated by Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA). The glass transition temperatures (T g) of the three TF-BA resins all exceed 200 degrees C. Among them, the T g of TF-EBA is 276 degrees C, and the T g of TF-FBA is 282 degrees C. Under N2 atmosphere, the char yield (Y c) of all TF-BA resins at 800 degrees C is more than 40%. In summary, this study conducted a detailed discussion on the curing kinetics and thermal stability of monofunctional benzoxazines containing trifluoroacetyl amino groups, and it has certain reference value for related work.
While photocatalytic membranes have attracted significant attention for wastewater treatment, conventional electrospun membranes often display limited durability under continuous water flow. Although composite membrane structures can enhance mechanical stability, their fabrication generally involves complex, multi-step procedures and additional bonding treatments. To overcome these challenges, a single-step electrospinning strategy was employed to fabricate a mechanically robust, photocatalytic poly(vinylidene fluoride) (PVDF)/Fe2O3 composite membrane directly integrated with cellulose filter paper (CFP). Incorporation of cellulose acetate (CA) markedly improved interfacial compatibility between the electrospun layer and the cellulose substrate, resulting in a mechanically interlocked structure without the need for secondary adhesives. The optimized composite (PFC15@CFP) exhibited superior interfacial adhesion strength and delamination resistance in T-peel tests. Furthermore, the addition of Fe2O3 nanoparticles was systematically investigated to adjust the physicochemical and photocatalytic properties of the PVDF matrix. Energy-dispersive X-ray spectroscopy (EDS) confirmed a homogeneous distribution of Fe2O3 within the electrospun fibers. Increasing Fe2O3 content reduced fiber diameter and enhanced membrane wettability, decreasing the water contact angle from 112 degrees to 93 degrees. Among the fabricated samples, the PF8 membrane, characterized by uniform fibrous morphology and the smallest average fiber diameter (1.72 mu m), achieved the highest methylene blue degradation efficiency. These findings present a straightforward and effective method for developing mechanically stable, high-performance photocatalytic composite membranes for practical water-treatment applications.
