Showing papers by "Wei-Ping Pan published in 2004"

Polyvinyl chloride/ montmorillonite nanocomposites

Abstract: Polyvinyl chloride (PVC)/organic-montmorillonite composites were prepared by melt intercalation. Their structures and properties were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC) and mechanical testing. The results showed that PVC chains could be intercalated into the gallery of organically modified montmorillonite to form exfoliated PVC/organic-montmorillonite nanocomposites, and the glass transition temperatures of PVC/organic-montmorillonite composites were lower than that of neat PVC. However, the tensile strength, and both the Izod type and Charpy notched impact strengths of PVC/organic-montmorillonite nanocomposites were fitted with the linear expressions: t=535.07-6.39Tg, sI=378.76-4.59Tg and sC=276.29-3.59Tg, respectively.

Synthesis and properties of polystyrene–montmorillonite nanocomposites by suspension polymerization

Abstract: Organophilic montmorillonite was prepared using ion-exchange method between sodium ions in clay layers and stearyltrimethyl ammonium chloride in the various solvents, including deionized water, ethanol, acetone, and toluene. The montmorillonite has the largest d001 spacing, as determined by X-ray diffraction in toluene, than the other solvents considered. Ethanol can completely wash out the overexchanged stearyltrimethyl ammonium chloride among layers of montmorillonite. However, deionized water is the preferred ion-exchange solvent. The thermal stability of organophilic montmorillonite was investigated by high-resolution thermogravimetric analysis (TGA). Polystyrene–montmorillonite nanocomposites were obtained by suspension free radical polymerization of styrene in the dispersed organophilic montmorillonite. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that montmorillonite had been exfoliated. 5.0 wt % of clay in the synthesized nanocomposite was found to be the optimum content that improved both thermal and mechanical properties over those of pure polystyrene under the experimental conditions applied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 101–109, 2004

PE/Org-MMT nanocomposites

Abstract: The non-isothermal crystallization kinetics of polyethylene (PE), PE/organic-montmorillonite (Org-MMT) composites were investigated by differential scanning calorimetry (DSC) with various cooling rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the non-isothermal crystallization process of these samples very well. The difference in the exponent n between PE and PE/Org-MMT nanocomposites, indicated that non-isothermal kinetic crystallization corresponded to tridimensional growth with heterogeneous nucleation. The values of half-time, Zc and F(T) showed that the crystallization rate increased with the increasing of cooling rates for PE and PE/Org-MMT composites, but the crystallization rate of PE/Org-MMT composite was faster than that of PE at a given cooling rate. The method developed by Ozawa did not describe the non-isothermal crystallization process of PE very well. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. The results showed that the activation energy of PE/Org-MMT was greatly larger than that of PE.

Cure behavior of epoxy resin/MMT/DETA nanocomposite

Abstract: The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict the gel time tg and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation time tgand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60°C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent activation energy of the cure reaction after gelation point. There is no special curing process required for the formation of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite.

Application of a Circulating Fluidized Bed Process for the Chemical Looping Combustion of Solid Fuels

Abstract: Introduction In recent years more concerns have arisen about CO2 emission due to global warming. Among available or proposed technologies, chemical looping combustion (CLC) is the most promising technology to combine fuel combustion and CO2 purification. It uses a solid oxygen carrier to transfer the oxygen from the air to fuel in a reducer and oxidizer. Thus, air is never mixed with the fuel, and the CO2 does not become diluted by the nitrogen of the flue gas. NOx formation can be largely eliminated. A number of metals have been discussed in the literature, such as oxides of Fe, Ni, Co, Cu, Mn. Solid fuels such as coal and biomass have been ignored in CLC process due to technical problems, including the separation of oxygen carrier from fuel and ash, the possible interaction between the fuel ash and oxygen carriers and the combustion of unburned carbon particles in the oxidizer due to the circulation of solid fuel particles. The adaptation of the CLC to the combustion of solid fuels presents many challenges. In this paper, an innovative concept – application of a CFB combined with a moving bed on the chemical looping combustion of solid fuels is introduced.

Coal-like Thermal Behavior of a Carbon-Based Environmentally Benign New Material: Woodceramics

Abstract: Woodceramics prepared from apple pomace, which were obtained by impregnating it with phenolic resin and sintering the material at different temperatures of 1073 K (sample AWC800) and 1473 K (sample AWC1200), were investigated mainly by X-ray diffraction (XRD) and simultaneous differential scanning calorimetry−thermogravimetry (DSC−TG). The as-prepared samples were amorphous; using XRD, broad peaks with d-spacings of ca. 0.57−0.52 and ca. 0.36−0.38 nm were observed. This result suggested the presence of at least two different phases: the former, which is attributed to a structure derived from aliphatic chains, and the latter, which is attributed to a structure derived from aromatic rings (graphene-like layers). By heating to 1273 K, the aromatic-ring stacking or graphene-like layers developed in three dimensions, whereas the aliphatic chains, which are more prone to oxidization, disappeared when heated in air. Therefore, it was suggested that combustible fragments with aliphatic chains develop via pyrolys...

The lab-scale sorbent injection testing on mercury capture with follow-up solid-gas mixture

Abstract: Introduction The DOE prefers the retrofitting of dry sorbent injection upstream of either an ESP or an fabric filter baghouse to further control mercury emission in coal-fired power plants. This promising technology has the widest potential application for controlling mercury emissions in plants that are not equipped with FGD scrubbers, which includes 75% of all U.S. plants. However, unlike the successful carbon injection for mercury control in waste incinerators, which produces one or two orders of magnitude lower mercury emissions, sorbent injection used in coal-fired utility boiler faces many challenges. Large quantities of PAC must be injected, leading to high costs if high removal efficiency is required. In this study, two new highly effective, low-cost mercury sorbents including IGCC char and woodceramic will be used to inject in the simulated duct in a lab-scale facility with a low pressure drop turbulence mixer to enhance the mass transfer of mercury capture process.