Yumin Wu

Controlling the morphology of calcium sulfate hemihydrate using aluminum chloride as a habit modifier

The morphology and aspect ratio of calcium sulfate hemihydrate (HH) are successfully controlled using AlCl3 as a morphology modifier in the hydrothermal synthesis process. As the concentration of AlCl3 is increased from 0 to 7.5 × 10−2 mol L−1, the crystal length decreases from 130 μm to 0.1–0.3 μm and the corresponding aspect ratio declined dramatically from 150–240 to 1–2, and the crystal morphology gradually changes from whiskers to rods, and even irregular nanogranules. The preferential adsorption of Al3+ on the side facets of HH would lower the surface energy and inhibit the elongation along these facets. The doping of Al3+ in the HH would destroy the main chain of HH and inhibit the elongation along the [001] direction. The two facts contribute to the morphology control. This work exhibits an efficient method to control the morphology of HH over a large range of size by simply adjusting the concentration of AlCl3.

Calcium sulfate hemihydrate whisker reinforced polyvinyl alcohol with improved shape memory effect

A new shape memory polymer is synthesized by introducing calcium sulfate hemihydrate whiskers (HHW) to reinforce polyvinyl alcohol (PVA). The tensile strength of the composite is increased by 57%, and the storage modulus reaches 22.24 GPa.

Swelling properties of particles in amphoteric polyacrylamide dispersion

Swelling properties of amphoteric polyacrylamide (AmPAM) dispersions were investigated by measurements of apparent viscosity and particle morphology. AmPAM dispersion was prepared by dispersion polymerization in aqueous solution of ammonium sulphate. Changes of particles during dispersion polymerisation of AmPAM were simulated and compared with anionic and cationic polyacrylamide (APAM and CPAM, respectively). Sample viscosity and particle morphology were obtained using a rotational viscometer and optical microscope. It was found that small molecules or ions enter and swell particles in the AmPAM dispersion when (NH4)2SO4 concentration decreases. Similarly, monomers, including acrylamide, acrylic acid, and methacrylatoethyl trimethyl ammonium chloride, have the same effects on the AmPAM dispersion but the effect degree is different. Swelling properties of the AmPAM dispersion were different from those of the APAM and CPAM dispersions due to their different ionic nature, type of stabiliser, media, etc. Particles in the APAM or CPAM dispersions were swelled less than those in the AmPAM dispersion.

A type of thiophene-bridged silica aerogel with a high adsorption capacity for organic solvents and oil pollutants

A type of thiophene-bridged silica aerogel was prepared from tetraethyl orthosilicate (TEOS) and 2,5-divinyltrimethoxysilanethiophene (DVTHP) through a facile sol–gel reaction and ambient pressure drying process. DVTHP was synthesized from vinyl trimethoxysilane and 2,5-dibromothiophene through the Heck reaction. FTIR and solid-state 1H CP/MAS NMR indicated that the thiophene units had been successfully introduced into the silica aerogel network. SEM showed a co-continuous porous structure and the Brunauer–Emmett–Teller (BET) measurements showed a mesoporous structure that had a high surface area of 834 m2 g−1, an average pore size of 17.84 nm and a large pore volume of 3.72 cm3 g−1. This thiophene-bridged silica aerogel had superhydrophobicity with a water contact angle (CA) exceeding 174° and a sliding angle of less than 3°. The silica aerogel had better selectivities for less polar or non-polar solvents than for polar solvents. The introduction of the thiophene unit could improve the adsorption properties. The adsorption capacities for n-hexane and gutter oil were calculated as 17 g g−1 and 16 g g−1, respectively. Moreover, the samples exhibited good recyclability for organic solvents even after recycling 10 times in adsorption/desorption tests and the adsorption capacities were nearly unchanged from the maximum uptake capacities. The results indicated that these materials could be flexibly utilized as adsorbent materials to selectively adsorb organic solvents for wastewater treatment.

Synthesis and characterization of waterborne polyurethane emulsions based on poly(butylene itaconate) ester

Abstract Waterborne polyurethane (WPU) prepolymer was synthesised by the reaction of poly(butylene itaconate) ester (PBI, Mn = 1109 g/mol), 1,6-hexanediol, dimethylol propionic acid (DMPA), 2,4-toluene diisocynate (TDI), hydroxyethyl acrylate (HEA), and absolute ethanol as blocking agent, triethylamine as neutralizer. Cross-linked WPU was synthesized by trimethylolpropane (TMP) as crosslinker. The influences of PBI, DMPA, and TMP content on WPU emulsions and films were investigated. The structure of WPU was determined by Fourier transform infrared (FTIR) spectra, thermal properties and glass transition temperature of WPU films were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively, and morphology of the emulsion particles was observed by transmission electron microscopy (TEM). Through TGA, the heat resistance of the cross-linked WPU film was better than WPU film. By DSC analysis, glass transition temperature of cross-linked WPU film (21 °C) was higher than WPU film (10 °C).