Ji Whan Ahn

A strategy of precipitated calcium carbonate (CaCO3) fillers for enhancing the mechanical properties of polypropylene polymers

A wide variety of fillers are currently used in more than twenty types of polymer resins, although four of them alone (polypropylene, polyamides, thermoplastic polyesters, and polyvinyl chloride) account for 90% of the market of mineral fillers in plastics. Polypropylene (PP) and PVC dominate the market for calcium carbonate. PP is a versatile reinforcement material that can meet engineering and structural specifications and is widely used for automotive components, home appliances, and industrial applications. Talc, mica, clay, kaolin, wollastonite, calcium carbonates, feldspar, aluminum hydroxide, glass fibers, and natural fibers are commonly used in fillers. Among these, calcium carbonate (both natural and synthetic) is the most abundant and affords the possibility of improved surface finishing, control over the manufacture of products, and increased electric resistance and impact resistance. Meeting the global challenge to reduce the weight of vehicles by using plastics is a significant issue. The current the global plastic and automobile industry cannot survive without fillers, additives, and reinforcements. Polypropylene is a major component of the modern plastic industry, and currently is used in dashboards, wheel covers, and some engine parts in automobiles. This article reports that the use of calcium carbonate fillers with polypropylene is the best choice to enhance the mechanical properties of plastic parts used in automobiles.

Effects of modified LDPE on physico-mechanical properties of HDPE/CaCO3 composites

HDPE/CaCO3/LDPE-g-MA composites of high density polyethylene (HDPE) and calcium carbonate (CaCO3) with maleic anhydride grafted low density polyethylene (LDPE-g-MA) as a compatibilizer were prepared by melt mixing. LDPE-g-MA was prepared using a solution process. The maximum grafting degree was obtained at 6 wt% maleic anhydride (MA) and 0.2 wt% dicumyl peroxide (DCP) at 120 °C and 240 min. Functional groups not found in pure LDPE were observed with the formation of LDPE-g-MA. The successful dispersion of CaCO3 particles in the HDPE matrix using LDPE-g-MA was revealed. The crystallite size of the composites was a little higher than that of CaCO3. The mechanical properties of the HDPE/CaCO3/LDPE-g-MA composites increased with decreasing CaCO3 content. Thermogravimetric analysis (TGA) revealed a higher thermal stability for the HDPE/CaCO3/LDPE-g-MA composites than for pure HDPE. Differential scanning calorimetry (DSC) revealed that the crystallization conditions were not substantially different. However, melting enthalpy and crystallinity increased with decreasing CaCO3 content. The thermal stability was greatly improved compared to that previously reported for nano CaCO3.

Competing Ion Effect of Stabilization by Cr(III) & Cr(VI) in Ettringite Crystal Structure

In this study, the degree of the substitution of Cr3+ and Cr6+ into the ettringite structure has been investigated to extent the immobilization potential of ettringite in the field under specific conditions. Aqueous suspension containing calcium hydroxide, alumium sulfate, CrCl2(trivalent chromium) and CrO3(hexavalent chromium) was subjected to ultrasound irradiation under atmospheric pressure to investigate their effects on synthesis of Cr-ettringite. In the result, the substitution of Cr3+ into Al site takes place in ettringite structure in solution with Cr3+, and monosulfate/friedel’ salt phase is also formed by occurrence of extra Al ion in solution. However, in the case of Cr6+, owing to a higher affinity of sulfate anion to form ettringite than that of Cr6+,most of Cr6+ did not substituted into the crystal structure of ettringite.

Characteristic of Carbonation Reaction from Municipal Solid Waste Incinerator Bottom Ash as a Function of Water Content and their Effect on the Stabilization of Copper and Lead

Most carbonation processes utilizing municipal solid waste incineration bottom ash characteristically involve a high water content (over 100%). In this work, we developed an improved carbonation process, utilizing various water contents. In addition, we investigated the characteristics of a carbonation reaction using municipal solid waste incinerator bottom ash as a function of water content and their effects on the stabilization of copper and lead. As a result of such a carbonation reaction, the effect on the stabilization of heavy metals can be obtained. Due to this, the leaching concentrations of these were reduced. In a high water content, calcium aluminum compounds via carbonation reaction adsorbed Cu and Pb ions. Where a low water content (especially 30%) is present, particle surfaces are surrounded by calcium aluminum compounds of bottom ash as a result of the carbonation process. The leaching concentration of Cu and Pb were decreased through the carbonation process.

Aragonite Precipitated Calcium Carbonate: A New Versatile Functional Filler for Light Weight Plastic

This study was carried out to investigate the how aragonite precipitated calcium carbonate (PCC) with specific needle shape morphology prepared from natural limestone and how it is effectively worked as versatile functional filler to light weight plastic. Aragonite was synthesized from limestone by ecofriendly carbonation process under optimal experimental conditions. The synthesized needle like aragonite precipitated calcium carbonate (PCC) was influenced mechanical properties such as tensile strength, impact resistance, flexural modulus, young’s modulus and thermal properties of polypropylene composites. The effects of CaCO3 of varying particle sizes (0.1µm ~ 80 µm) content (0–40 wt%) on the crystallization and mechanical properties, and process ability of CaCO3-filled s-PP were investigated.

Roles of Additives on Crystal Growth Rate of Precipitated Calcium Carbonate

The characteristics of nucleation and the crystal growth of aragonite-precipitated calcium carbonate in Ca(OH)2 – MgCl2 – CO2 system by a carbonation process is investigated. MgCl2, in this study, was added in order to increase the formation yield of aragonite precipitated calcium carbonate. Optimum conditions of the concentration of the reactants, the temperature and the amount of additives were studied. The formation yield of calcite gradually decreased, and the formation yield of aragonite increased with the addition of MgCl2. A higher formation yield of above 98% for aragonite is obtained by the adding of the Mg2+ ion in a 0.2M Ca(OH)2 – 0.6M MgCl2 – CO2 system at 80. The nucleation rate increased as the temperature decreased and as the CO2 gas flow rate increased. The particle size and aspect ratio increased at a high temperature, a low flow rate of gas, and a high concentration of Ca(OH)2 slurry. Small-sized aragonite was obtained at a low temperature. The increase in crystal size with the decrease in the CO2 gas flow rate can be explained by the decrease in the nucleation rate, in addition to the increase in the crystal growth rate resulting from the decrease in the dissolution rate to CO3 2- ion.

The Effect of Initial Hydration Temperature on the Characteristics of Calcium Hydroxide and Aragonite Precipitated Calcium Carbonate

Precipitated Calcium Carbonate (PCC) is obtained through three processes; that of calcination, hydration, and carbonation. Thus, changes in each process condition determine the particle size or morphology of the mediums (calcium oxide and calcium hydroxide) as well as the product (PCC). To date, studies concerning precipitated calcium carbonate have mainly focused on the carbonation process, aimed at the manufacturing of PCC. Thus far, few studies on calcination or hydration have been conducted. Calcium hydroxide is regarded as the most important factor during the carbonation process. It is obtained through a hydration process. Therefore, in order to create the valuable PCC studies that center on the hydration process should be carried out. The present study seeks to investigate the effect of the hydration condition, particularly the temperature, on the synthesis characteristics of calcium hydroxide and aragonite PCC. The results show that the particle size of calcium hydroxide changes with variations in the initial hydration temperature. In particular, a higher initial temperature resulted in a larger particle size of the calcium hydroxide used in the synthesis. The particle size and yield of aragonite also increased when calcium hydroxide created at high temperatures was used. However, the water/solid ratio or total amount at the hydration time had no effect on the manufacturing process of aragonite.

Encapsulation of Municipal Solid Waste Incineration Bottom Ash to Immobilize Cu and Pb via Carbonation Reaction

Bottom ash generated from municipal solid waste incinerators in metropolitan areas contain calcium and aluminum compounds. As a result of a carbonation reaction, calcite and a calcium aluminum compound (Na6CaAl6Si6O24, Ca2Al2SiO7) as well as amorphous aluminum oxide can be found in bottom ash. Due to this, Cu and Pb leaching concentrations decrease via a carbonation process. Recently, the study of artificial carbonation reaction has been actively investigated, but most of these studies have been carried out utilizing an aqueous solution method with high water content. In this study, the carbonation reaction takes place in an aqueous environment, but does not occur on the surface of the particle. However, to cause the encapsulation of a particle with calcite, calcium aluminum compound and amorphous aluminum oxide, these must be formed on the surface of particle. Therefore in this study, a low water content encapsulation method of bottom ash from municipal solid waste incinerator was investigated with a view to immobilize Cu and Pb via a carbonation reaction. As seem in the results, the encapsulation effect appeared to be successful, with a water content of 20%.

Changing Morphology and Crystal Structure in Ettringite by Trivalent Chromium

Recently, solidification processing by cement material of waste that isn’t only increasing but also study is now in progress. Ettringite(Ca6[Al(OH)6]2(SO4)3•26H2O), which is a hydration product of calcium aluminate minerals is highly effective at immobilizing heavy metallic ions through a substitution mechanism. An aqueous solution containing calcium hydroxide, aluminum sulfate, and CrCl3(trivalent chromium) was subjected to irradiate by ultrasonic irradiation under atmospheric pressure to investigate its effect on the synthesis of Cr(III)-ettringite. The verified XRD (100) peak tended to shift to the left and changed morphology as CrCl3 input.

Effect of Magnetic Separation in Heavy Metals of Municipal Solid Waste Incineration Bottom Ash

Bottom ash contains many ferrous materials (e.g. ferrous metals, Fe3O4, Fe2O3, FeS). In addition, ferrous metals include the heavy metals, as Ni and Cr have a chemical attraction to iron, with Cu used to coat with Ni and Cr metals for polishing or to prevent corrosion. For ferrous metals, the formation of a Fe3O4-Fe2O3 double layer (similar to pure Fe) was found during air-annealing in an incinerator (1000C). A strong thermal shock, such as that which takes place during water-cooling of bottom ash, leads to the breakdown of this oxidation layer, facilitating the degradation of ferrous metals and the formation of corrosion products. Therefore, Fe-ion (heavy metal) oxides can be formed on ferrous metals, and magnetic separation can separate it from bottom ash. Thus, in this study the objection is to investigate the separation ratio of heavy metals by magnetic separation along with the mineralogical formation of Fe-ion (a heavy metal).