Electrospun Nanofibrous Membranes of Polyacrylonitrile/Halloysite with Superior Water Filtration Ability

The necessity of benefiting a breakthrough in filtration technology has led to increasing attention in advanced functional nanosized materials such as nanofibers for filtering devices as a solution for providing water at lower energy costs. In this study, electrospun polyacrylonitrile (PAN) nanofibrous membranes were reinforced by 1, 2, and 3% w/w of halloysite nanotubes (HNTs) in order to improve their mechanical properties, thermal stability and water filtration performance for the possible application as water filtration membranes. Morphological analysis revealed the highly porous and nanofibrous structure of membranes which further confirmed by surface area analysis (BET). Incorporation of HNTs enhanced the mechanical properties of the membranes such as tensile strength and elongation at break (especially at 1% w/w HNTs) while resulted in significant improvement of their thermal properties. Moreover, PAN/HNTs membranes showed excellent oil/water separation performance, while incorporation of HNTs led to increase in water flux rate, which is considered as a key point in water filtration membranes. Additionally, heavy metal ion adsorption performance of the membranes showed a significant increase by incorporation of 3% w/w HNTs. These results signified the potential of electrospun PAN/HNTs nanofibrous membranes to be used for water filtration applications

Unveiling Carbon Fiber Reinforced Polyurea Composites Engineered through Vacuum Assisted Resin Transfer Molding: An In-depth Analysis of Mechanical, Thermal, and Degradation Performance

Carbon fiber reinforced polymer (CFRP) composites have attracted increasing attention in recent years as they exhibit excellent mechanical strength and are substituting metals in marine, automotive, aerospace, and construction industries. However, the brittleness of CFRP leads to low toughness, limiting its structural performance. In this work, for the first time, the utilization of super elastomeric polyurea as the matrix with carbon fiber via vacuum-assisted resin transfer molding is featured. This study revealed a direct correlation between the number of carbon fabric layers and the enhancement of the flexural load, stiffness, and resistance to mechanical indentation. The 8-layer laminate with a thickness of 2.5 mm showed flexural strength of 237 MPa at 5% flexural strain, flexural modulus of 93.4 GPa and hardness of 80 HD. Polyurea matrix demonstrated exceptional stress absorption and redistribution capabilities, preventing complete breakage up to 5% flexural strain, ultimately restoring the laminates’ position upon unloading. Field emission scanning electron microscopy analysis showed strong matrix-fiber interfacial adhesion that could be attributed to the interphase mechanical locking resulting in high storage modulus of 2441 MPa. An in-depth analysis of the laminates’ fracture morphology unveiled delamination predominantly within the compression zone, except for the 2-layer laminate, where fractures manifested simultaneously in both compression and tension zones due to the slender thickness. Furthermore, the degradation behavior of the polyurea composite laminates under exposure to 5% NaCl solution at a temperature of 60 °C highlighted an initial increase in flexural strength within the initial 28-day period, attributed to the plasticizing effect induced by moisture. However, at 63 days, a decline in flexural strength is observed, signaling the degradation and debonding of the matrix from the reinforcing fibers. This work opens the door for viscoelastic CFRP as an excellent absorbing composite material with high toughness that is suitable for marine environments

Effect of Morphology and Size of Halloysite Nanotubes on Functional Pectin Bionanocomposites for Food Packaging Applications

Pectin bionanocomposite films filled with various concentrations of two different types of halloysite nanotubes were prepared and characterized in this study as potential films for food packaging applications. The two types of halloysite nanotubes were long and thin (patch) (200-30 000 nm length) and short and stubby (Matauri Bay) (50-3000 nm length) with different morphological, physical, and dispersibility properties. Both matrix (pectin) and reinforcer (halloysite nanotubes) used in this study are considered as biocompatible, natural, and low-cost materials. Various characterization tests including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, release kinetics, contact angle, and dynamic mechanical analysis were performed to evaluate the performance of the pectin films. Exceptional thermal, tensile, and contact angle properties have been achieved for films reinforced by patch halloysite nanotubes due to the patchy and lengthy nature of these tubes, which form a bird nest structure in the pectin matrix. Matauri Bay halloysite nanotubes were dispersed uniformly and individually in the matrix in low and even high halloysite nanotube concentrations. Furthermore, salicylic acid as a biocidal agent was encapsulated in the halloysite nanotubes lumen to control its release kinetics. On this basis, halloysite nanotubes/salicylic acid hybrids were dispersed into the pectin matrix to develop functional biofilms with antimicrobial properties that can be extended over time. Results revealed that shorter nanotubes (Matauri Bay) had better ability for the encapsulation of salicylic acid into their lumen, while patchy structure and longer tubes of patch halloysite nanotubes made the encapsulation process more difficult, as they might need more time and energy to be fully loaded by salicylic acid. Moreover, antimicrobial activity of the films against four different strains of Gram-positive and Gram-negative bacteria indicated the effective antimicrobial properties of pectin/halloysite functionalized films and their potential to be used for food packaging applications. \ua9 2017 American Chemical Society