Abstract: Auxetic fibrous structures and composites with negative Poisson’s ratio (NPR) have huge potential for application in ballistic protection due to their high energy absorption and excellent impact resistance. In the present research, re-entrant lozenge auxetic fibrous structures were produced through weft knitting technology using high performance polyamide and para-aramid fibres. Fabric structural parameters (e.g. loop length) and machine parameters (e.g. take down load) were varied in order to investigate their influence on the auxetic behaviours of the produced structures. These auxetic structures were then impregnated with two types of polymeric resins (epoxy and polyester) to produce composite materials, which were subsequently characterized for the auxetic behaviour. It was observed that the knitted fabrics produced using the polyamide yarns exhibited NPR over a wide deformation range, which was strongly dependant on the loop length and take down load. The polymeric composites produced from the auxetic fabrics also showed good auxetic property, which was superior in case of the polyester matrix. The experimental results suggested that these composites made from the auxetic fibrous structures can be properly designed to find potential use in the body amours for personal protection applications.
Abstract: Strong anion exchange resins with QN+OH-, have the
potential to be developed and employed as heterogeneous catalyst for
transesterification, as they are chemically stable to leaching of the
functional group. Nine different SIERs (SIER1-9) with QN+OH-were
prepared by suspension polymerization of vinylbenzyl chloridedivinylbenzene
(VBC-DVB) copolymers in the presence of n-heptane
(pore-forming agent). The amine group was successfully grafted into
the polymeric resin beads through functionalization with
trimethylamine. These SIERs are then used as a catalyst for the
transesterification of triacetin with methanol. A set of differential
equations that represents the Langmuir-Hinshelwood-Hougen-
Watson (LHHW) and Eley-Rideal (ER) models for the
transesterification reaction were developed. These kinetic models of
LHHW and ER were fitted to the experimental data. Overall, the
synthesized ion exchange resin-catalyzed reaction were welldescribed
by the Eley-Rideal model compared to LHHW models,
with sum of square error (SSE) of 0.742 and 0.996, respectively.
Abstract: Polystyrene (PS) was extracted from Styrofoam (expanded polystyrene foam) waste, so called white pollutant. The PS was functionalized with N,N- Bis(2-aminobenzylidene)benzene-1,2-diamine (ABA) ligand through an azo spacer. The resin was characterized by FT-IR spectroscopy and elemental analysis. The PS-N=N-ABA resin was used for the enrichment and speciation of Cr(III)/Cr(VI) ions and total Cr determination in aqueous samples by flame atomic absorption spectrometry (FAAS). The separation of Cr(III)/Cr(VI) ions was achieved at pH 2. The recovery of Cr(VI) ions was achieved ≥ 95.0% at optimum parameters: pH 2; resin amount 300mg; flow rates 2.0mL min-1 of solution and 2.0mL min-1 of eluent (2.0mol L-1 HNO3). Total Cr was determined by oxidation of Cr(III) to Cr(VI) ions using H2O2. The limit of detection (LOD) and quantification (LOQ) of Cr(VI) were found to be 0.40 and 1.20μg L-1, respectively with preconcentration factor of 250. Total saturation and breakthrough capacitates of the resin for Cr(IV) ions were found to be 0.181 and 0.531mmol g-1, respectively. The proposed method was successfully applied for the preconcentration/speciation of Cr(III)/Cr(VI) ions and determination of total Cr in industrial effluents.