Effects of various polyolefin copolymers on the interfacial interaction, microstructure and physical properties of cyclic olefin copolymer(COC)/graphite composites

In this study, effects of various types of functional polyolefin copolymers (FPOCs), poly(isobutylene-alt-maleic anhydride), poly(maleic anhydride-alt-1-octadecene) and poly(ethylene-graft-maleic anhydride), on the microstructure formation, interfacial interaction and physical properties of cyclic olefin copolymer (COC)/graphite composites were investigated. The COC/graphite composites were prepared in a lab. scale twin screw extruder. Microstructural features of samples were studied in a field emission scanning electron microscopy (FESEM). Viscoelastic properties of samples, obtained from the rheology tests in melt state and the dynamic mechanical analysis in solid state were used to quantify interfacial interactions between the COC and graphite depending on the types of FPOC. The average aspect ratio (A(f)) values of graphite flakes in the COC phase were determined about 40-65 by SEM observation and image analysis study on the samples prepared with different types of FPOC. Based on the gas permeability measurements, tortuous diffusion model suggested that the A(f) values of graphite flakes varied between 40 and 80 depending on the amount of graphite. It was shown that the poly(isobutylene-alt-maleic anhydride) copolymer provided relatively higher interfacial interaction between the COC and graphite flakes than the other FPOCs

Crosslinked polyDADMAC gels as highly selective and reusable arsenate binding materials

High porosity cationic hydrogels synthesized via crosslinking co-polymerization of diallyldimethylammonium chloride (DADMAC) with N,N'-tetraallylpiperaziniumdichloride (TAP) showed high affinity towards arsenate anions over a wide pH range within notably short periods. Batch tests indicated that poly(DADMAC) hydrogels removed 99% of the arsenate anions from aqueous solutions at pH 6-10 and exhibited a maximum arsenic removal capacity of 0.12 g arsenic per gram of hydrogel. DADMAC hydrogels performed well at various pH levels after a short contact time (i.e., 10 min). Evidence of the ion exchange mechanism was based on experiments with solutions containing competing chloride and sulfate ions. An "intra-particle diffusion model" was proposed for the kinetics of arsenic removal. This gel was determined to be a good candidate for use in practice due to its easy regeneration either by treating with a 8.24 g/L of NaCl solution or by reducing the pH of the medium to below 1.0