Nanofiller dispersion, morphology, mechanical behavior, and electrical properties of nanostructured styrene-butadiene-based triblock copolymer/CNT composites

A nanostructured linear triblock copolymer based on styrene and butadiene with lamellar morphology is filled with multiwalled carbon nanotubes (MWCNTs) of up to 1 wt% by melt compounding. This study deals with the dispersability of the MWCNTs within the nanostructured matrix and its consequent impact on block copolymer (BCP) morphology, deformation behavior, and the electrical conductivity of composites. By adjusting the processing parameters during melt mixing, the dispersion of the MWCNTs within the BCP matrix are optimized. In this study, the morphology and glass transition temperatures (Tg) of the hard and soft phase are not significantly influenced by the incorporation of MWCNTs. However, processing-induced orientation effects of the BCP structure are reduced by the addition of MWCNT accompanied by a decrease in lamella size. The stress-strain behavior of the triblock copolymer/MWCNT composites indicate higher Young’s modulus and pronounced yield point while retaining high ductility (strain at break ~ 400%). At a MWCNT content of 1 wt%, the nanocomposites are electrically conductive, exhibiting a volume resistivity below 3 × 103 Ω·cm. Accordingly, the study offers approaches for the development of mechanically flexible functional materials while maintaining a remarkable structural property profile

Wear Performance Forecasting of Chopped Fiber–Reinforced Polymer Composites: A New Approach Using Dimensional Analysis

<p>Solid particle erosion of polymer matrix composites is a complex process in which wear occurs from the target surface by impingement of rigid sand particles in an air medium. The rate of material removal (RMR), also referred to as the erosion rate, mainly depends on target material parameters and the erosion conditions such as impact angle, impact velocity, and erodent size. A new semi-empirical model for prediction of the erosion rate of polymer matrix composites has been developed using a dimensional analysis technique based on Buckingham's π theorem. The predictive model analytically rests upon parameters related to chopped glass fiber composites, erodent (target material properties), and operating variables that mainly affect the erosion process of chopped glass fiber–vinyl ester resin composites. The forecasting ability of the predictive model has been assessed and verified by experimental investigations for chopped glass fiber–reinforced vinyl ester resin (VGF) composites. Validation of the theoretical erosion rates obtained from the predictive model showed that they were in good agreement with the experimentally determined erosion rates, where the average error range was estimated to be ∼10 to ∼20%.</p

A combinatorial approach to the elastic response of electrospun mats: Architectural framework and single fiber properties

Electrospun is a unique class of porous and heterogeneous materials with multi-length-scales constituents that offer a rich variety of surface functionalities to serve a host of applications. Upscaling the electrospun materials from the laboratory to the industry is often limited by the lack of understanding of their mechanical properties. Herein, we developed a theoretical framework to predict the elastic constants of the electrospun mats that hinges on the concept of elastic properties of constituent fibers, three-dimensional (3D) alignment of fibers, and local fiber curvature. Enabled by continuum-based micromechanical approaches, this framework successfully pre-dicted the elastic moduli regardless of bead-string morphology and local architectural heterogeneities present within the electrospun mats. The 3D fiber orientation distribution obtained using X-ray nano-computed tomography (nanoCT) analysis served as a key input for the validation of the analytical model. In general, the predicted elastic moduli are in reasonably good agreement with the experimental data of randomly oriented and preferentially aligned polylactic acid (PLA)-based electrospun mats. To demonstrate our analytical model's versatility and reliability, another set of PA6(3)-based electrospun mats has been chosen from the literature for validation purposes. The parametric analysis has been performed to provide a roadmap to improve the elastic moduli of electrospun mats and justify the assumed values of some of the key attributes

COVID‐19 vaccines and their underbelly: Are we going the right way?

Abstract Background Historically, a critical aetiological agent of health concern stays till eternity after its discovery, so shall it be with the COVID‐19 outbreak. It has transformed human life to a ‘new normal’ with huge tolls on the social, psychological, intellectual and financial spheres. Aim This perspective aimed to collate numerous reported COVID‐19 vaccine‐associated adverse events and the predisposing factors. It focussed on the efficacy of mix‐n‐match (cocktail) vaccines to effectively counter COVID‐19 infection to facilitate future research and possible interventions. Material and Methods Databases like Scopus, Pubmed and the Web‐of‐science were searched for published literature on ‘adverse events associated with COVID‐19 vaccine’. The reports and updates from health agencies like the WHO and CDC were also considered for the purpose. The details with respect to the adverse events associated with COVID‐19 vaccination and the predisposing factors were compiled to obtain insights and suggest possible future directions in vaccine research. Results India stood strong to manage its health resources in time and turned into a dominant global vaccine supplier at a time when healthcare infrastructure of many countries was still significantly challenged. Developing indigenous vaccines and the vaccination drive in India were its major achievements during the second and the subsequent COVID‐19 waves. The fully indigenous Covaxin vaccine, primarily as an emergency intervention, was successfully rapidly launched. Similar such vaccines for emergency use were developed elsewhere as well. However, all of these reached the marketplace with a ‘emergency use only’ tag, without formal clinical trials and other associated formalities to validate and verify them as these would require much longer incubation time before they are available for human use. Discussion Many adverse events associated with either the first or the second/booster vaccination doses were reported. Evidently, these associated adverse events were considered as ‘usually rare’ or were often underreported. Without the additional financial or ethical burden on the vaccine companies, fortunately, the Phase IV (human) clinical trials of their manufactured vaccines are occurring by default as the human population receives these under the tag ‘emergency use’. Thus, focused and collaborative strategies to unveil the molecular mechanisms in vaccine‐related adverse events in a time‐bound manner are suggested. Conclusion Reliable data particularly on the safety of children is lacking as majority of the current over‐the‐counter COVID‐19 vaccines were for emergency use. Many of these were still in their Phase III and Phase IV trials. The need for a mutant‐proof, next‐gen COVID‐19 vaccine in the face of vaccine‐associated adverse events is opined