A comparative investigation on different silane coupling agents modified sericite mica/polyimide composites prepared by in situ polymerization

Construction of Durable, Colored, Superhydrophobic Wood-Based Surface Coatings Using the Sand-In Method

Highly durable color superhydrophobic coatings have attracted much attention in indoor and outdoor decorative applications. In this paper, colorful superhydrophobic coatings with excellent durability were prepared using silane coupling agent-modified iron oxide as the pigment and polydimethylsiloxane-compounded epoxy resin as the base material by the three-step method of "spraying-sanding-spraying". The method is low cost, has a simple preparation process, enables large-area preparation, and has a restorative function. The use of red, yellow, blue, and green four kinds of modified iron oxides through the single color or multicolor into the sand can be obtained by a variety of color coatings, and silica mixed with a variety of colors can be obtained from light to dark coatings. The coating has excellent superhydrophobicity and self-cleaning ability to withstand sandpaper abrasion, water impact, sand impact, UV exposure, and environmental testing. The coating is suitable for interior and exterior decoration and for protection of wooden buildings.

Chemical and Mechanical Characterization of Unprecedented Transparent Epoxy–Nanomica Composites—New Model Insights for Mechanical Properties

Two nanomicas of similar composition, containing muscovite and quartz, but with different particle size distributions, have been used to prepare transparent epoxy nanocomposites. Their homogeneous dispersion, due to the nano-size, was achieved even without being organically modified, and no aggregation of the nanoparticles was observed, thus maximizing the specific interface between matrix and nanofiller. No exfoliation or intercalation has been observed by XRD, despite the significant dispersion of the filler in the matrix which produced nanocomposites with a loss in transparency in the visible domain of less than 10% in the presence of 1% wt and 3% wt of mica fillers. The presence of micas does not affect the thermal behavior of the nanocomposites, which remains similar to that of the neat epoxy resin. The mechanical characterization of the epoxy resin composites revealed an increased Young’s modulus, whereas tensile strength was reduced. A peridynamics-based representative volume element approach has been implemented to estimate the effective Young’s modulus of the nanomodified materials. The results obtained through this homogenization procedure have been used as input for the analysis of the nanocomposite fracture toughness, which has been carried out by a classical continuum mechanics–peridynamics coupling approach. Comparison with the experimental data confirms the capability of the peridynamics-based strategies to properly model the effective Young’s modulus and fracture toughness of epoxy-resin nanocomposites. Finally, the new mica-based composites exhibit high values of volume resistivity, thus being excellent candidates as insulating materials.

Application of Dual Silane Coupling Agent-Assisted Surface-Modified Quartz Powder in Epoxy Matrix for Performance Enhancement

Quartz powder (QP) is an inorganic filler that is expected to significantly enhance the dielectric and mechanical properties of epoxy (EP)-based composites applied in copper clad laminates and epoxy molding compounds for 5G applications. As is well-known, the performance of the QP–EP composites is directly correlated with the dispersion effect and the compatibility of QP with an EP matrix. Herein, we propose the surface modification method of QP by mixing SCAs of different alkyl chain lengths that contain amino and carbonyl groups. Different characterization methods (FTIR, TGA, XPS, SEM, contact angle measurement, viscosity, and mechanical properties) and molecular dynamics simulation were adopted to study its effect and mechanism. Through dual SCA modification, the viscosity of QP–EP composites was reduced by 11.70%, and the flexural and tensile strengths increased by 16.89% and 30.01%, respectively. In addition, it was revealed that the superiority of dual SCAs originated from the synergistic effect between APTES and SPIS, it was the electrostatic repulsion force between the amino groups of the two SCAs that caused a steric hindrance that activated the steric stabilization effect of SPIS, thus resulting in better dispersion and excellent compatibility. Meanwhile, the amino and carbonyl groups of the SCA interacted with the EP matrix via chemical bonds and hydrogen bonds, thus strengthening the interfacial adhesion between the QP and EP matrix and improving the mechanical performance of QP–EP composites. These results are evidence of the potential of the proposed approach, which is based on the synergistic compounding of SCA with different molecular structures, in powder industrial applications.

Double-Layer Nacre-Inspired Polyimide-Mica Nanocomposite Films with Excellent Mechanical Stability for LEO Environmental Conditions

Owing to their outstanding comprehensive performance, polyimide (PI) composite films are widely used on the external surfaces of spacecraft to protect them from the adverse conditions of low Earth orbit (LEO). However, current PI composite films have inadequate mechanical properties and atomic oxygen (AO) resistance. Herein, this work fabricates a new PI-based nanocomposite film with greatly enhanced mechanical properties and AO resistance by integrating mica nanosheets with PI into a unique double-layer nacre-inspired structure with a much higher density of mica nanosheets in the top layer. In addition, the unique microstructure and the intrinsic properties of mica also impart the nanocomposite film with favorable ultraviolet and high-temperature resistance. The comprehensive performance of this material is superior to those of pure PI, single-layer PI-mica, and previously reported PI-based composite films. Thus, the double-layer nanocomposite film displays great potential as an aerospace material for use in LEO.