The permeation behaviors of permeants were investigated in the pervaporation of a homologous series of alcohol aqueous mixtures through a hydrophilic poly(vinyl alcohol) (PVA). The PVA membrane was crosslinked with glutaraldehyde. A homologous series of alcohols used in this study were methanol, ethanol, 1‐propanol, and 1‐butanol. The pervaporation experiments were carried out with feed having 70–97 wt % of alcohol contents and at various feed temperatures. In a high alcohol content above 92 wt %, the permeation rate was increased in the order of the interaction strength between alcohol and water in the feed. However, in a low alcohol content below 90 wt %, the tendency of the permeation rate was found to be the opposite, indicating that the interactions between permeant constituents play an important role in determining the permeation and separation of the mixtures. These observations were discussed in terms of changes in the interaction between the permeant/permeant or the permeant/membrane in varying feed compositions and feed temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 703–713, 2001

ABSTRACT:Chitosan microcapsules containing the water-soluble herbicide 3-hydroxy-5-methylisoxazole were fabricated at different fabrication conditions by a new microencapsulation process established in the previous work. Selecting chitosan as a capsule wall could be justified because chitosan not only has a biodegradable characteristic but also enhances the fertility of soil after degradation in the ground. The microcapsules prepared at an agitation speed of higher than 12,000 rpm were smaller than 5 m in diameter, and the release of the active material from the capsules into pure water was sustained for 80 -160 h, depending on the agitation speed used in microencapsulation. The effects of fabrication variables were discussed on the capsule size and release properties of the fabricated microcapsules.

ABSTRACT:The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant . The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 ϫ 10 Ϫ3 and 32.48 ϫ 10 Ϫ3 mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions.

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant . The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 ϫ 10 Ϫ3 and 32.48 ϫ 10 Ϫ3 mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions.

The permeation behaviors of permeants were investigated in the pervaporation of a homologous series of alcohol aqueous mixtures through a hydrophilic poly(vinyl alcohol) (PVA). The PVA membrane was crosslinked with glutaraldehyde. A homologous series of alcohols used in this study were methanol, ethanol, 1-propanol, and 1-butanol. The pervaporation experiments were carried out with feed having 70 -97 wt % of alcohol contents and at various feed temperatures. In a high alcohol content above 92 wt %, the permeation rate was increased in the order of the interaction strength between alcohol and water in the feed. However, in a low alcohol content below 90 wt %, the tendency of the permeation rate was found to be the opposite, indicating that the interactions between permeant constituents play an important role in determining the permeation and separation of the mixtures. These observations were discussed in terms of changes in the interaction between the permeant/permeant or the permeant/membrane in varying feed compositions and feed temperatures.