Biaxial rotational molding is a low-pressure process that uses a polymer powder to produce large and/or complex-shaped hollow thermoplastic goods using low cost molds, being very suitable for prototype production. In the present work, liner prototypes (F 78 × 280 mm) made of linear low density (LLDPE) and high density polyethylene (HDPE) blends were produced aiming to later use them as compressed natural gas type IV cylinders. The LLDPE/HDPE blend composition and the process parameters (temperature/time cycle, and rotation speed) were varied to evaluate their effect on blend miscibility and liner final properties, such as density and crystallization behavior. Blend composition and process parameters were found vital for the production of a homogeneous wall and for the liner to reach adequate characteristics for the intended product.

A procedure to correlate self-diffusion coefficients in dense fluids by using the perturbation theory (WCA) coupled with the smooth-hard-sphere theory is presented and tested against molecular simulations and experimental data. This simple algebraic expression correlates well the self-diffusion coefficients of carbon dioxide, ethane, propane, ethylene, and sulfur hexafluoride. We have also performed canonical ensemble molecular dynamics simulations by using the Hoover-Nosé thermostat and the mean-square displacement formula to compute self-diffusion coefficients for the reference WCA intermolecular potential. The good agreement obtained from both methods, when compared with experimental data, suggests that the smooth-effective-sphere theory is a useful procedure to correlate diffusivity of pure substances.

Este trabalho objetiva a modelagem das curvas de extração características do processo de extração supercrítica do óleo essencial de alecrim (Rosmarinus officinallis l.), obtidas nas isotermas de 310,15 e 320,15 K nas pressões de 100, 120, 140 e 160 bar, e interpretar os parâmetros e a função objetivo com conceitos estatísticos. Utilizou-se na resolução das equações do modelo o método das diferenças finitas, na obtenção dos parâmetros utilizou-se o método da máxima verossimilhança. Os resultados simulados indicam que o modelo utilizado constitui-se numa ferramenta capaz de representar as curvas de extração do processo de extração supercrítica.

This work intend to model supercritical fluid extraction of Rosemary essential oil (Rosmarinus officinallis l.) obtained at 310.15 and 320.15 K at 100, 120, 140 and 160 bar and to analyze the parameters and the objective function with statistic tools. We have been used the finite differences method to solve the model, the parameters were estimated using the maximum-likelihood method. The results have shown that the model can reproduce the experimental data of supercritical fluid extraction.