The Influence of UV Radiation Aging on Degradation of Shear Thickening Fluids

Statistical approach on the inter-yarn friction behavior of the dual-phase STF/ρ-Aramid impregnated fabrics via factorial design and 3D-RSM

Shear thickening fluids (STFs) refer to non-Newtonian fluids of the dilatant variety, wherein their viscosity experiences a significant surge with an escalation in the shear rate. In this investigative work, the friction behavior between yarns (pull-out) and absorption of static and kinetic energy during the phenomenon of friction between yarns in STFs are performed by monophase (MP-STF) adding nano SiO2 and dual-phase (MP-STF) adding carbon nanotubes. The ρ-Aramid fabrics were reinforced via the "foulard process", and carried out on MP-STF, and DP-STF/ρ-Aramid-impregnated fabrics to evaluate and compare with the enhancement in interfacial friction properties between yarns. The results showed that DP-STF has more significant than MP-STF and MP-STF in ultimate load, kinetic shear stress, static shear stress, and friction energy level effects. The DP-STF exhibits various friction enhancement mechanisms at the yarn interface, leading to higher absorption of static and kinetic energy related to interfacial friction, as indicated by the results obtained. Furthermore, the DP-STF/ρ-Aramid impregnated fabrics exhibited ultimate load (22.23 ± 0.522 N), kinetic shear stress (35.73 ± 0.850 MPa*100), static shear stress (36.28 ± 0.900 MPa*100), and friction energy level (610.33 ± 0.250). Increased ultimate load (581.7% and 180.7%), kinetic shear stress (621.4% and 174.6%), static shear stress (550.5% and 159.1%), and friction energy level (680.2 and 186.7%) compared to WT-STF and MP-STF, respectively. The current discoveries hold immense potential for various applications in the fields of engineering and smart material technologies. These applications span a multiplicity of industries, including sports products, medical advancements, space technology, as well as protective and shielding products.

Effects of UV sensitivity and accelerated photo-aging on stab resistance of ρ-aramid fabrics impregnated with shear thickening fluids (STFs)

The use of Kevlar in the field of ballistic and stabbing protection has been studied by researchers in polymeric composites for this purpose. This study presents complementary knowledge on energy absorption and dissipation in ρ-aramid fabric impregnated with shear thickening fluids (STFs), especially aiming to obtain better protection against impacts that are deeply associated with STFs, as well as color change, accelerated aging (QUV), and penetration depth (drop tower test). In addition, Scanning Electron Microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) was performed. The research shows that there was a good distribution of STF particles on the ρ-Aramid fabric surface, promoting increased friction between the interfilament and the yarns, further increasing performance and, consequently, improving the energy absorption and dissipation mechanism and, also, the penetration effectiveness in relation to non-impregnated ρ-Aramid fabric. Regarding the protection efficiency against UV exposure (250-400 nm region), there was a significantly decreased compared to those non-impregnated Kevlar® woven with STFs. The FTIR analysis showed that the conditions of aging, after exposure to UV, did not produce new functional groups, that is, there was no chemical modification. Finally, Kevlar fabric impregnated with STFs improved penetration depth performance with the blades independent of the blade type with up to 81% increase in resistance. This result was improved due to interactions between the nanoparticles present in STFs, yarns, and even high-performance woven impregnated with shear-thickening fluids.

Obtaining and Characterizing New Advanced Materials

This editorial highlights the results presented in the second Special Issue dedicated to obtaining and characterizing new materials, wherein one review paper and 13 research articles have been published. The most important field covered is that of materials involved in civil engineering, focusing on geopolymers and insulating materials alongside developing new methods for enhancing the characteristics of different systems. Another important field is that of the materials used for environmental issues, and finally, those involved in human health.

Unexpected Method of High-Viscosity Shear Thickening Fluids Based on Polypropylene Glycols Development via Thermal Treatment

This study aimed to analyze the influence of the thermal treatment of shear thickening fluids, STFs, on their viscosity. For this purpose, shear thickening fluids based on polypropylene glycols PPG400 and PPG1000 and Aerosil®200 were developed. The shear thickening behavior of obtained fluids was confirmed by using a parallel-plate rheometer. Next, thermogravimetric (TG) analyses were used to characterized thermal stability and weight loss of the STFs at a constant temperature. Finally, the thermal treatment of the STFs obtained was provided using the apparatus developed for this purpose. The received STFs exhibited a very high maximum viscosity up to 15 kPa. The rheology of the STFs measured after thermal treatment indicated that the proposed method allowed the development of STFs with a very high maximum viscosity. The maximum viscosity of the STFs increased twofold when thermal treatment of the STFs at elevated temperature for 210 min was performed. TG confirmed the convergence of the weight loss in the apparatus. Our results show that controlling the thermal treatment of STFs allows STFs to be obtained with high viscosity and a dilatation jump of the STFs by degradation of the liquid matrix.