Untitled in english

Author(s)

José Carlos Moreira

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 1999-11-17

Examining board members

Nicole Raymonde Demarquette; Yoshio Kawano; Denise Freitas Siqueira Petri

• Advisor: Nicole Raymonde Demarquette

Abstract

The knowledge of the surface tension of molten polymer is very importante in the plastics, inks, films, textiles, and adhesions technology. However, few experimental data of surface tension of molten polymer have been publish due to experimental difficulties encountered to determine this parameter. In this work, the influence of temperature, molecular weight(Mn) and molecular weight dispersity (MWD) the surface tension of polystyrene (OS) was evaluated using the pendant drop method. The experimental results compared to the predictions of the discrete interface cell model (DICM). This model uses Flory, Orwoll, and Vrj (FOV) equation of state theory to predict surface tension () of the molten polymers from pressure-volume-temperature (PVT) data. It was shown that surface tension of OS decreases with increasing temperature for all the polymers studied here. The surface tension of OS increased when the molecular weight of polystyrene was varied from 3,000 to 40,000. When the molecular weight of OS was further increased the surface tension was shown to level off. The surface tension was shwon to decrease with increasing molecular weight distribution. It was shown that DICM theory predicts the influence of temperature, and molecular weight on surface tension of OS, PP, and PE. However, the absolute values of surface tension did not corroborate. Therefore, one of the parameters inherent to the theory, which is related to the thickness of the interface layer was modified. The experimental and theoretical results were then in good agreement. (AU)