Examining the Quasi-Static Uniaxial Compressive Behaviour of Commercial High-Performance Epoxy Matrices

Four commercial high-performance aerospace aromatic epoxy matrices, CYCOM®890, CYCOM®977-2, PR520, and PRISM EP2400, were cured to a standardised 2 h, 180 °C cure cycle and evaluated in quasi-static uniaxial compression, as well as by dynamic scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoplastic toughened CYCOM®977-2 formulation displayed an overall increase in true axial stress values across the entire stress-strain curve relative to the baseline CYCOM®890 sample. The particle-toughened PR520 sample exhibited an overall decrease in true axial stress values past the yield point of the material. The PRISM EP2400 resin, with combined toughening agents, led to true axial stress values across the entire plastic region of the stress-strain curve, which were in line with the stress values observed with the CYCOM®890 material. Interestingly, for all formulations, the dilation angles (associated with the volume change during plastic deformation), recorded at 0.3 plastic strain, were close to 0°, with the variations reflecting the polymer structure. Compression data collected for this series of commercial epoxy resins are in broad agreement with a selection of model epoxy resins based on di- and tetra-functional monomers, cured with polyamines or dicarboxylic anhydrides. However, the fully formulated resins demonstrate a significantly higher compressive modulus than the model resins, albeit at the expense of yield stress.

The effect of pH on the functionalization of nylon fabric with carbon nanotubes

Single walled carbon nanotubes (SWCNTs) were dispersed in water and attached to nylon fabrics by a dip-drying procedure; scanning electron microscopy and Raman spectroscopy suggest the attachment of the SWCNTs. The electrical resistance of the functionalized fabrics is found to be pH-dependent, which is correlated with the quantity of SWCNTs dispersed in water at different values of pH. This can be further ascribed to the influence of the pK(a) of the acid (e.g., acetic acid in this study) used to tune pH. The acid may affect the dispersion of SWCNTs through two different mechanisms: (1) the free protons may protonate the amine and/or sulfonate group in the dye molecules, resulting in a variety of interactions among the dye molecules, SWCNTs and water molecules and (2) the resulting ions may increase the ionic strength of the solution, compressing the electric double layers of SWCNT colloids and thus impairing their stability. The former possibility is ruled out by data obtained using X-ray photoelectron spectroscopy, Raman spectroscopy, and ultraviolet-visible-near infrared spectroscopy; thus the latter is proposed to account for the experimental results. The colour strength of the functionalized fabrics increases with increasing pH, which is in agreement with their measured electrical properties.

Antimicrobial and anticancer efficacy of antineoplastic agent capped gold nanoparticles

Synthesis of thioguanine (TG)-capped Au nanoparticles (Au@TG) and their enhanced in vitro antimicrobial and anticancer efficacy against Micrococcus luteus, Staphylococcus aureus, Pseudomonas aeruginosa, E. coli, Aspergillus fumigatus, Aspergillus niger and Hep2 cancer cell (Human epidermiod cell) have been reported. The nature of binding between 6-TG and the gold nanoparticles via complexation is investigated using ultraviolet-visible spectrum, cyclic voltammetry, transmission electron microscopy, fluorescence and Fourier transform infrared (FT-IR) spectroscopy. The present experimental studies suggests that Au@TG are more potential than TG towards antimicrobial and anticancer activities. Hence, gold nanoparticles have the potential to be used as effective carriers for anticancer drug.

Development of quantitative structure property relationships for poly(arylene ether)s

The technique of quantitative structure-activity relationships (QSAR) is well accepted by the drug design community. The analogous technique of quantitative structure-property relationships (QSPR) has applications in the field of polymer chemistry. A variety of molecular modeling and molecular orbital techniques was used to find molecular descriptors that could be used to derive an empirical equation to describe the glass transition temperature of two related classes of poly(arylene ether)s. The derived equation was then used to predict the thermal characteristics of another polymer of the same type.