Performance of form-stable myristic acid/polymethyl methacrylate composite phase-change material coated with nitrile butadiene rubber/polyacrylic acid layered coatings

The aim of this work is to determine the effect of coating and blending composition of myristic acid (MA) with polymethyl methacrylate (PMMA) on the latent heat and thermal stability of phase change material (PCM). Form-stable PCM (FSPCM) was prepared by blending MA with PMMA and then coating with nitrile butadiene rubber (NBR) and polyacrylic acid (PA) layers. This is the first attempt to coat the PCM with elastomeric latex. Leakage test results showed that addition of 20 wt% PMMA to the MA and NBR-PA coating layers could eliminate leakage in sample PCM8O. Tensile test results showed that NBR-PA coating material provide sufficient strength and elasticity to hold the PCM during the phase change process. Latent heat of melting and freezing of the form stable PCM80 is 107.56 J/g and 102.26 J/g, which is comparable with other results in the literature. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48642.     

Feasibility of using digital filters to interconnect p.c.m. and f.d.m. transmission systems

A time-division multiplex (t.d.m.) and a frequency-division multiple (f.d.m.) system may be interconnected by means of gates and lowpass filters. The use of digital filters (d.f.s) for this purpose appears attractive when the t.d.m. system uses pulse-code modulation (p.c.m.), because digital-analogue and analogue-digital conversion are unnecessary at the interface between the d.f. and the p.c.m. system. The problems involved in applying d.f.s in this application are discussed. It is concluded that the interconnection of p.c.m. systems with f.d.m. systems using quite low carrier frequencies requires the development of digital circuits operating at several hundred megahertz.     

Metal coordination and selectivity with oxine ligands bound to silica polyamine composites

A series of oxine ligands, 5‐X, 8? OH? C₉H₆N (X = H, Cl, SO₃H) have been covalently bound to a silica gel polyamine composite made from a silanized amorphous silica xerogel and poly(allylamine) (BP‐1) by the Mannich reaction. The resulting modified composites WP‐4(X = H), CB‐1(X = Cl), and SB‐1(X = SO₃H) were characterized by elemental analysis, FTIR, and solid state CPMAS‐¹³C‐NMR. Using the analytical data before and after the ligand modification, the ligand loading could be estimated and in combination with metal ion capacities a metal to ligand ratio could be obtained. The composites WP‐4 and CB‐1 both showed ratios of approximately 1 : 1 while the sulfonate modified composite, SB‐1, showed a metal to ligand ratio of 1 : 2. This is tentatively interpreted in terms of a zwitterionic oxine as the dominant species at pH = 2 where the sulfonic acid group is ionized, the quinoline nitrogen is protonated and where two sulfonate groups on adjacent oxines bind a trivalent or divalent ion. All the modified composites show a clear selectivity for trivalent over divalent ions and a good selectivity for gallium over aluminum. The substituent groups on the oxine ligand have only a minor influence on these selectivity trends but SB‐1 shows slightly better capture kinetics. The selectivity for gallium over aluminum is applied to the separation of gallium from aluminum, ferrous, and zinc in an acid ore leach of solid tailings obtained from a zinc mine using WP‐4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Performance evaluation of polyamide nanofiltration membranes for phosphorus removal process and their stability against strong acid/alkali solution

In this study,a quantitative performance of three commercial polyamide nanofiltration(NF) membranes(i.e.,NF,NF90,and NF270) for phosphorus removal under different feed conditions was investigated.The experiments were conducted at different feed phosphorus concentrations(2.5,5,10,and 15 mg·L~(-1)) and elevated pHs(pH 1.5,5,10,and 13.5) at a constant feed pressure of 1 MPa using a dead-end filtration cell.Membrane rejection against total phosphorus generally increased with increasing phosphorus concentration regardless of membrane type.In contrast,the permeate flux for all the membranes only decreased slightly with increasing phosphorus concentration.The results also showed that the phosphorus rejections improved while water flux remained almost unchanged with increasing feed solution pH.When the three membranes were exposed to strong pHs(pH 1.5 and 13.5) for a longer duration(up to 6 weeks)it was found that the rejection capability and water flux of the membranes remained very similar throughout the duration,except for NF membrane with marginal decrement in phosphorus rejection.Adsorption study also revealed that more phosphorus was adsorbed onto the membrane structure at alkaline conditions(pH 10 and 13.5) compared to the same membranes tested at lower pHs(pH 1.5 and 5).In eonelusion,NF270 membrane outperformed Nf and NF90 membranes owing to its desirable performance of water flux and phosphorus rejection particularly under strong alkali solution.The NF270 membrane achieved 14.0 L·m~(-2)·h~(-1) and 96.5% rejection against 10 mg·L~(-1) phosphorus solution with a pH value of 13.5 at the applied pressure of 1 MPa.