Long- and short-term creep of polyoxymethylene/polyurethane/alumina ternary composites by comparison

Ternary composites consisting of polyoxymethylene, polyurethane (PU), and boehmite alumina were produced by melt blending with and with out latex precompounding. The latex precompounding served to predisperse the alumina particles. The related advanced masterbatch (MBa) was produced by mixing the PU latex with the water-dispersible boehmite alumina. The dispersion of alumina and rubber particles was studied by using the scanning electron micros copy. The creep properties of the composites were determined from results of long- and short-term creep tests (per formed at various temperatures). The composites produced by the MBa technique out performed those made by direct melt compounding with respect to most of creep characteristics. The Findley power law was found to be fairly applicable to the experimental results obtained. Master curves (strain vs. time) were also constructed by employing the time-temperature super position principle.     

Rheological and dynamic thermomechanical propert ies of epoxy composites reinforced with single- and multiwalled carbon nanotubes

An epoxy resin (Epon 828) was filled with single- and multiwalled carbon nanotubes (SWCNT and MWCNT) in two steps by using the high shear mixing and ultrasonication techniques. The melt flow of the composites was characterized in a plate/plate rheometer. The thermomechanical properties of the composites were determined in dynamic mechanical analysis tests performed at various frequencies and temperatures. It was found that the incorporation of SWCNT or MWCNT increased the viscosity and stiffness of epoxy above its glass-transition temperature. The time-temperature superposition principle was employed to estimate the storage modulus of the composites as a function of frequency (f = 10^–33–10³ Hz) in the form of master curves.     

Development and analysis of biodegradable poly(propylene carbonate)/tamarind nut powder composite films

Using biodegradable polypropylene carbonate as the matrix and the tamarind nut powder (TNP) in 5–25?wt% as the filler, the biocomposites were prepared. The biocomposites were characterized by Fourier transform infrared, X-ray diffraction, and thermogravimetric analysis techniques. The distribution of the TNP in the biocomposites was examined by polarized optical microscope. The tensile strength of the biocomposite films was higher than that of the matrix and increased with filler content whereas a reverse trend was observed in % elongation at break. These films with increased tensile strength can be considered for packaging applications.     

Ultraviolet nanosecond laser ablation behavior of silver nanoparticle and melamine–formaldehyde resin-coated short sisal fiber-modified PLA composites

Nd:YAG laser (355 nm) induced surface modifications in polylactic acid (PLA), and its composites with silver nanoparticles (AgNPs, size range between 120 and 150 nm) with and without additional melamine–formaldehyde-coated short sisal fibers were studied as a function of laser pulse numbers. The AgNP content was varied (100, 300 and 500 ppm), whereas the sisal content kept as constant (9 mass%). The PLA-based systems with a fully amorphous matrix were irradiated with 1–256 laser pulses at a constant fluence of 0.32 µJ µm^?2. Changes in the irradiated surfaces were assessed and quantified by light and scanning electron microscopic pictures. Protrusion with bubbling, bubbled protrusion with cratering and crater formation with more or less bubbled ridges were found as characteristic ablation features. Bubbling was traced to entrapped gaseous products of PLA degradation, while the onset of ridges was ascribed to the melt flow of the PLA matrix caused by laser shock waves. The laser irradiation caused damage and ablation highly depended on the actual composition, which influenced the UV absorption at 355 nm, which was measured as well.     

Characterization of novel natural cellulosic fibers from purple bauhinia for potential reinforcement in polymer composites

Cellulose - The aim of the present work was to extract novel natural cellulosic fibers from the leaves of purple bauhinia trees. To the best of our knowledge, this is the first time that, the...     

Modification of natural fibers from Thespesia lampas plant by in situ generation of silver nanoparticles in single-step hydrothermal method

Ligno-cellulosic fibers have a great market and propose higher value addition and options to develop various products but they do not have inherent antimicrobial properties. In this study, a simple hydrothermal method was applied to build up antimicrobial properties to natural fibers by in situ-generating silver nanoparticles (AgNPs) in them. Herein, the ligno-cellulosic Thespesia lampas natural fibers were selected to develop antimicrobial activity using silver nitrate (AgNO₃) solution by hydrothermal method. The modified fibers were characterized by SEM, FTIR, XRD, TGA, and antibacterial activity tests. The modified fibers had spherical AgNPs with an average size of 95?nm. The thermal stability of the modified fibers was higher than that of the unmodified fibers. The modified fibers exhibited good antibacterial activity against both the Gram negative and Gram positive bacteria. These modified fibers can be considered as fillers in polymer matrices to make antibacterial composites.