Mechanically Strong and Tailorable Polyimide Aerogels Prepared with Novel Silicone Polymer Crosslinkers

Polyimide (PI) aerogels were prepared using self-designed silicone polymer cross-linkers with multi-amino from low-cost silane coupling agents to replace conventional small-molecule cross-linkers. The long-chain structure of silicone polymers provides more crosslinking points than small-molecule cross-linkers, thus improving the mechanical properties of polyimide. To investigate the effects of amino content and degree of polymerization on the properties of silicone polymers, the different silicone polymers and their cross-linked PI aerogels were prepared. The obtained PI aerogels exhibit densities as low as 0.106 g/cm3 and specific surface areas as high as 314 m2/g, and the maximum Young’s modulus of aerogel is up to 20.9 MPa when using (T-20) as cross-linkers. The cross-linkers were an alternative to expensive small molecule cross-linkers, which can improve the mechanical properties and reduce the cost of PI aerogels.

Where ppm Quantities of Silsesquioxanes Make a Difference—Silanes and Cage Siloxanes as TiO2 Dispersants and Stabilizers for Pigmented Epoxy Resins

In this work, silsesquioxane and spherosilicate compounds were assessed as novel organosilicon coupling agents for surface modification of TiO2 in a green process, and compared with their conventional silane counterparts. The surface-treated TiO2 particles were then applied in preparation of epoxy (EP) composites and the aspects of pigment dispersion, suspension stability, hiding power, as well as the composite mechanical and thermal properties were discussed. The studied compounds loading was between 0.005–0.015% (50–150 ppm) in respect to the bulk composite mass and resulted in increase of suspension stability and hiding power by over an order of magnitude. It was found that these compounds may be an effective alternative for silane coupling agents, yet due to their low cost and simplicity of production and manipulation, silanes and siloxanes are still the most straight-forward options available. Nonetheless, the obtained findings might encourage tuning of silsesquioxane compounds structure and probably process itself if implementation of these novel organosilicon compounds as surface treatment agents is sought for special applications, e.g., high performance coating systems.

Synthesis of Substrate-bound Seaweed-like Au Nanowires with Amino Silane Coupling Agents

Seaweed-like Au nanowires were synthesized without any nanoparticle seeds. The amino silcane coupling agent 3-aminopropyltriethoxysilane was used to form the active surface on Au substrate to facilitate one dimensional growth....

Dye-sensitised Photocatalyst for Photocatalytic Whole Water Splitting to Produce Hydrogen in a Twin Photoreactor

Organic dye-sensitised SrTiO3:Rh and WO3 were served as H2 catalysts and O2 catalysts in a Z-scheme system to conduct photocatalytic pure water splitting. To enhance the light absorption capacity, the composites of organic dye (N3, N719, Z907, black dye, C101, and K19) and SrTiO3:Rh were synthesised via physical adsorption and then verified by the performance of photocatalytic hydrogen evolution. Among these dyes, N3-SrTiO3:Rh revealed visible light absorption and exhibited the best photocatalytic activity. Therefore, N3 dye was adopted, and silane coupling agents were used to form chemical bonding with SrTiO3:Rh. Furthermore, the photocatalytic pure water splitting of N3-SrTiO3:Rh was investigated in a single reactor, and a twin photoreactor with Fe2+ and Fe3+ ions served as the electron mediators, respectively. The highest quantum efficiency can reach 0.0259% in a twin reactor when compared with the single reactor (0.0052%) because of the improvement in the light absorption from N3 and inhibition of the backward reaction of water splitting. Consequently, organic dye-sensitised photocatalysts are highly effective and eco-friendly in conducting photocatalytic pure water splitting.

Preparation and characteristics of sepiolite-waterborne polyurethane composites

A kind of organic/inorganic composite material composed of waterborne polyurethane and sepiolite was prepared in this work. Sepiolite was organically modified by three kinds of silane coupling agents, and then compounded with waterborne polyurethane through layer-by-layer method in order to prepare composite materials. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) show the crystal and chemistry structure of sepiolite samples, and confirmed the preparation of organic sepiolite. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) showed the surface microstructure and elemental content of sepiolite and organic sepiolite, and was consistent with the XRD results. Transmission electron microscope (TEM) examination of waterborne polyurethane composites surfaces showed that sepiolite particles were regularly dispersed in the waterborne polyurethane matrix. Thermal resistance of waterborne polyurethane composites was determined by thermogravimetry analyzer (TG) and derivative thermogravimetry analyzer (DTG), differential scanning calorimetry (DSC), gas chromatography (GC), and mass chromatography (MS). Mechanical behavior was examined by tensile strength tester, showed higher break strength than that of the control waterborne polyurethane. Therefore, organically modified sepiolite was considered to be a kind of wonderful inorganic material that could be used to improve the thermal stability and mechanical property of polymer.

The influence of silane on the physico-mechanical properties of vulcanizates using bentonite fillers

Layered phyllosilicate fillers have received attention in the polymer industry due to their unique nanoscale sheet-like structure. Adding a small amount of bentonite nanofiller gives rise to improved mechanical, thermal, and gas barrier properties of rubber mixtures. Depending on the application, natural bentonite is often modified by physical processes or by chemical processes (intercalation, cation exchange process, functionalization, pillaring, etc.). Chemical modification increases the size of the interlayer spaces and provides a hydrophobic environment. Functionalization (e.g., silanization), which encompasses the chemical grafting of thermally stable silane coupling agents onto the clay platelets, make inorganic bentonite and the organic polymer matrix compatible. In the introduced study, commercial bentonite P130 from Lieskovec deposit was modified by silane (3-aminopropyl trietoxysilane) treatment. Different techniques such as infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize modified and raw bentonite sample. Silanized P130s and raw product P130 were added to the natural rubber matrix to examine the influence of chemically functionalized bentonite on curing characteristic (M H, M L, t s2, t 90, ΔM) and mechanical properties (TSb, Eb, hardness) of rubber vulcanizates. Organo-bentonite was mixed into a rubber blend in particular ratio of 5, 10, 15, 20 phr in various combination with silane (3-aminopropyl triethoxysilane), Perkasil and carbon black. The highest maximum torque values were obtained with the sample using 20 phr of silanized P130s. The tensile strength (TSb) values decreased with increasing P130 content, as well as non-silanized and silanized P130. However, when 20 phr P130s was used, value of TSb was higher. The most enhanced properties of rubber blends were found with the addition of 20 phr of silanized bentonite P130s.

Effects of silane coupling agent modifications of hollow glass microspheres on syntactic foams with epoxy matrix

A syntactic foam was prepared from an epoxy resin matrix and modified hollow glass microsphere fillers. Modification by silane coupling agents with different molecular structures was analyzed, and the optimal content of the silane coupling agent was determined. The results demonstrated that all silane coupling agents enhanced the adhesion between the hollow glass microspheres and epoxy resin matrix, resulting in enhanced water absorption, compressive performance, tensile performance, and bending performance compared to those prepared using unmodified hollow glass microspheres. Among silane coupling agents with different end groups, the one with a sulfhydryl end group exhibited optimal modification for hollow glass microspheres. Among the silane coupling agents with different backbone structures, the one with silanol groups exhibited the optimal modification of hollow glass microspheres. Additionally, the performance of the syntactic foams was optimal when 6% of the silanol-containing coupling agent was used. The results demonstrated that syntactic foams prepared with hollow glass microspheres modified by silane coupling agents exhibited improvements in water absorption, compressive performance, tensile performance, and bending performance, compared with those prepared using unmodified hollow glass microspheres. Among silane coupling agents with different end structures, the one with a sulfhydryl group as end group showed the best modification effect on hollow glass microspheres. The water absorption was 0.35%, the compressive strength was 62.15 MPa, the tensile strength was 40.15 MPa, and the bending strength was 53.17 MPa. Among silane coupling agents with different backbone structures, the one with silanol groupsbonds showed the best results. Its compressive strength was up to 64.15 MPa, the tensile strength was 35.47 MPa, and the bending strength was 53.99 MPa.

The improvement of physicomechanical, flame retardant, and thermal properties of lignocellulosic material filled polymer composites

In this study, the effects of alkali and silane coupling agents and coir fiber (CF) loading on the fundamental properties of the CF-filled polypropylene (PP) composites were investigated. Mechanical properties of the PP/CF composites, such as tensile strength, tensile modulus, impact strength, and water absorption were increased by the increase of the CF loading. The inclusion of 3-aminopropyl trimethoxy silane (ATS) and tetramethoxy orthosilicate (TOS) after the alkali pretreatment for the CF increased all the mechanical properties and water desorption of the resulting composites. This trend was more evident with the increase in CF loading. The best results were obtained for PP/TOS composites as compared to other composites. SEM images of fractured samples show improved adhesion between CF and PP matrix after treatment with ATS and TOS. The horizontal rate of combustion is significantly reduced with the inclusion of Mg(OH)2 in PP/ATS and PP/TOS composites. DSC results show improved crystallization temperature, melting temperature, and melting enthalpy as compared with virgin PP. The addition of ATS and TOS after the alkali pretreatment improved the thermal stability of the resultant composites. TOS-modified CF composites showed better resistance than ATS-modified CF composites in water medium.