Simulation of the compressible flow with mass transfer of semi-continuous mixtures
using the direct quadrature method of moments
[article: Computers & Chemical Engineering, vol. 64, pg 153-166, 05/2014] [ link ]
We developed a method for the solution of the compressible flow with mass transfer of semi-continuous mixtures and it is based on the Quadrature Method of Moments (QMoM) for continuous thermodynamics. The method extends the adaptive characterization of the continuous mixture to field problems and solves the mass transport equation for the continuous component. The method is referred as Direct QMoM, or DQMoM, for continuous thermodynamics. It was implemented in the OpenFOAM® as a compressible ideal gas flow solver. The DQMoM was applied to the mixing flow of two gas streams with different compositions of a mixture with 57 hydrocarbons diluted in nitrogen. We showed that 4 adaptive components reproduced the mixture properties within 3% accuracy. Furthermore, the DQMoM CFD solution was approximately two times faster than the solution using 58 discrete components.
Oligobetapinene as barrier improver to CO2 of HDPE in thin films of binary blends
[article: Polímeros: Ciência e Tecnologia, vol. 14, iss 4, pg.261-264, 2004] [ download ]
Quenched thin films (about 100 microns thick) of high-density polyethylene (HDPE) / oligobetapinene (OBP) blends were prepared by melt mixing with the amount of OBP varying from 0 to 40%. The results of CO2 permeation, thermal behavior and morphology are reported. From -130 to -100 °C we observed two peaks in DSC measurements, the lower one being ascribed to g-transition of HDPE. The upper one attributed to Tg which was shift at high contents of OBP. The OPB molecules also displayed another transition at higher temperatures. The normalized degree of crystallinity of HDPE remained constant while the overall crystallinity of the blends was reduced in all blends. We have hypothesized that three distinct phases coexist, viz. a HDPE-amorphous phase with some amount of OBP molecules, OBP-amorphous phase with polyolefin and HDPE-crystalline phases. The permeation test revealed a decrease in permeability to CO2 independent of the amount of OBP in the blends. The reduction of gas permeation could be explained mainly by the rigidity of the OBP rich phase that has counterbalanced the decrease of overall crystallinity of the film blends.
Effect of addition of oligobetapinene on morphology, thermal and gas permeation properties in blends with HDPE
[article: Journal of Applied Polymer Science, vol 91, iss 1, pg 315–320, 01/2004] [ link ]
Binary blends of high density polyethylene (HDPE) and oligobetapinene (OBP) were prepared by melt mixing. The morphology, thermal and permeability properties of compression molded and slow cooled films are reported. Applying the first-derivative procedure on differential scanning calorimetry (DSC) traces, we have detected the temperature of glass transition (Tg) of HDPE as a large peak centered from −125 to −100°C. In the blends, we observed that the OBP molecules were able to resolve the transition into two components. The lower one was ascribed to the γ-transition of HDPE, and the upper one was attributed to its Tg. The OBP molecules also formed another transition at a higher temperature. The blends were composed at least of three distinct phases, likely composed of amorphous HDPE with some amount of OBP molecules, amorphous OBP with some polyolefin and crystalline HDPE. The scanning electron microscopy (SEM) investigations revealed segregation of the components. The permeation to CO2 of plain HDPE and 90/10 blends was similar, but at higher concentrations of oligomer, the value was slightly higher than that of neat HDPE. The decrease of overall crystallinity was counterbalanced by the presence of an OBP rich phase in the blend and could explain the slight increase in permeability of the film blends.