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ABSTRACT:The dependency of the density of poly( 1-caprolactone) -polycarbonate (PCL-PC) blends on composition has been studied. PCL/PC blends are typical of miscible blends containing crystallizable components, and miscibility is therefore considered with respect to the amorphous phase. In literature, a single glass transition temperature is reported for the PCL-PC system; however, the exact dependency on amorphous phase composition is not clear. For quenched amorphous blends, we found the Fox equation to be appropriate in order to describe the glass transition temperature as a function of composition. For amorphous samples containing low amounts of PCL (ß40 wt %), an increase in the density of the blend over that of a linear average of the densities of amorphous PC and PCL was observed experimentally. This is indicative of significant interactions in the blend. For samples containing ® 50 wt % PCL, crystallization of PCL has to be accounted for in the analysis of the density. It is shown that the experimental density data can only be described satisfactorily by assuming that secondary crystallization of PCL does not lead to an increase of the overall blend density. This is attributed to the rigid and volume filling primary crystalline structure at room temperature, i.e., below the melting point of PCL. Excess density is present in the amorphous phase of the PCL/PC blend over the whole range of composition; therefore, specific interactions exist in the amorphous phase of the blend over the whole range of composition.

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Abstract--The mathematical formulation of mass transfer in drying processes is often based on the diffusion equation. In principle the diffusion coefficient as a function of moisture content has to be determined experimentally. The most direct approach is to derive the diffusion coefficient from experimental moisture concentration profiles in the material during drying. In this work, the diffusion coefficient determined in this way is called the actual diffusion coefficient. Very often, however, an indirect method is used based on drying curves (average moisture content of a sample vs time). Since the diffusion coefficient is determined indirectly from the macroscopic behaviour of the sample, this coefficient will be called the apparent diffusion coefficient. A comparison of diffusion coefficients as a function of moisture content using both methods shows that for porous materials such as clays, the apparent diffusion coefficient depends on experimental conditions. This can be explained by the fact that the apparent diffusion coefficient is in agreement with the actual diffusion coefficient over a limited range of moisture content only. For materials such as clays, drying curves are not suited to derive diffusion coefficients as a function of moisture content in a satisfactory and consistent way.

-, T~ukuba, T~u k u b~~. ,Ibaraki 305-8565, JapanSurface treatments using glow discharge plasmas from 0, and Ar were applied to blend sheets of poly(E-capro1actone)-polycarbonate (PCL/PC), which had been produced by extrusion from melts of the mixture at various blend ratios. As to the reactivity of these two plasmas, 0,-plasma forms the oxidative species to be reactive in general, while Ar-plasma is non-oxidative. Weight loss by the oxidative 0,-plasma etching increased with the content of PCL in the polymer blends. The surface became hydrophilic by plasma treatment, and the changes were affected also by the blend ratio. PC and the PC-rich blend sheets became more hydrophilic than the PCGrich blends after plasma treatments. The 0,-plasma treatments were more effective than non-oxidative Ar-plasma treatment in increasing the hydrophilicity. Hydrophilic change was related to the increase in the polar contribution of surface energy. Plasma TreatmentsPlasma for surface treatments was generated by inductively coupled discharge at 13.56 M H z using an RF generator (HFS 005, Nihon Koshuha Co. Ltd., Japan). Polymer blend sheets were treated by plasmas from 0, and Ar in a reactor made of Pyrex glass tubing (4.4 cm diameter, 26 cm length) (14). Gas supply for glow discharge was regulated by the opening of the v&e (=-4BMG, Nupro CO., USA), and the system presswe 270, B-tron Co., USA).

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