Nanostructures Technology, Research, and Applications

Contains reports on twenty research projects and a list of publications.Joint Services Electronics Program Contract DAAL03-92-C-0001Semiconductor Research Corporation Contract 94-MJ-550U.S. Army Research Office Grant DAAL03-92-G-0291Advanced Research Projects Agency/Naval Air Systems Command Contract N00019-92-K-0021National Science Foundation Grant ECS 90-16437National Science Foundation Grant ECS 90-16737IBM Corporation Contract 1622U.S. Air Force - Office of Scientific Research Grant F-49-62-92-J-0064National Science Foundation Grant DMR 87-19217National Science Foundation Grant DMR 90-22933National Aeronautics and Space Administration Contract NAS8-3674

Studies on the interaction of water with ethylcellulose: Effect of polymer particle size

The purpose of this research was to investigate the interaction of water with ethylcellulose samples and assess the effect of particle size on the interaction. The distribution of water within coarse particle ethylcellulose (CPEC; average particle size 310 μm) and fine particle ethylcellulose (FPEC; average particle size 9.7 μm) of 7 cps viscosity grade was assessed by differential scanning calorimetry (DSC) and dynamic vapor sorption analysis. The amounts of nonfreezing and freezing water in hydrated samples were determined from melting endotherms obtained by DSC. An increase in water content resulted in an increase in the enthalpy of fusion of water for the two particle size fractions of EC. The amount of nonfreezable water was not affected by the change in particle size at low water contents. Exposure of ethylcellulose to water for 30 minutes is sufficient to achieve equilibration within the hydrated polymer at 47% wt/wt water content. The moisture sorption profiles were analyzed according to the Guggenheim-Anderson-de Boer (GAB) and Young and Nelson equations, which can help to distinguish moisture distribution in different physical forms. The amount of externally adsorbed moisture was greater in the case of FPEC. Internally absorbed moisture was evident only with the CPEC. In light of these results, and explanation is offered for the success of FPEC in wet-granulation methods where CPEC was not successful