Adriana Martinelli Catelli de Souza

Influence of coalescence and interfacial tension on the morphology of PP/HDPE compatibilized blends

Abstract In this paper, the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: ethylene–propylene–diene copolymer (EPDM), ethylene–vinylacetate copolymer (EVA) and styrene–ethylene/butylene–styrene triblock copolymer (SEBS). The morphology of the blends was studied by scanning electron microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the compatibilizer concentration added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA or SEBS. The relative role of interfacial tension reduction and coalescence reduction to particle size reduction was also addressed. It was observed that the role of coalescence reduction is small, mainly for PP/HDPE (90/10) blends compatibilized by EPDM, EVA or SEBS. The results indicated that the role of coalescence reduction to particle size reduction is lower for blends for which interfacial tension between its components is low at compatibilizer saturation.

Efeito do abacate (Persea americana Mill) variedade hass na lipidemia de ratos hipercolesterolêmicos

Phytonutrients can be found in fruits, and the avocado contains four times more beta-sitosterol (phytosterol) and it is one of the best glutathione sources. The phytosterol is a vegetable substance whose structure is very similar to the cholesterol one and its action mechanism involves the intestinal inhibition of cholesterol absorption and the synthesis of hepatic cholesterol. The effect has an influence on the values of total plasmatic cholesterol and LDL without affecting the levels of HDL and triglycerides. The present work had the objective to analyze the influence of the consumption of the Hass avocado on the levels of total cholesterol, HDL, LDL, triglycerides, and hepatic and excreted cholesterol. These parameters were investigated in hipercholesterolemic Wistar rats during 30 and 60 days of experiment. At the end of 30 days, the 15% avocado diet reduced the levels of total cholesterol and LDL in comparison to the control. It was observed that for the excreted cholesterol, the best diet was the 25% of avocado since the cholesterol excretion increased with the increase of the avocado concentration. The 15% avocado diet also influenced the levels of hepatic cholesterol.

Comportamento Viscoelástico Linear e Morfologia de Blendas PP/HDPE

In this paper the influence of composition and temperature on the linear viscoelastic behavior and morphology of PP/HDPE blends was studied. The interfacial tension between PP and HDPE was evaluated using the relaxation spectra of PP/HDPE blends, following Gramespacher and Meissner analysis (1) . The results seemed to indicate that there is a range of compositions for which it is possible to use Gramespacher and Meissner analysis in order to calculate interfacial tension between polymers using small amplitude oscillatory shear measurements. The compatibilization of PP/HDPE blend was also studied through morphological analysis and interfacial tension between its components. Three types of compatibilizers were tested: EPDM, EVA and SEBS. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the concentration of compatibilizer added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA or SEBS.