Phase Equilibrium Study Of PLA Polymer Blends

This paper took blending PM into PLA to improve PLA's brittleness as a research background, described molecular thermodynamics model research of polymer solution and blends, and detailed introduced the theory models such as Flory-Huggins and Flory equation of state in common used in industrial applications and scientific research. Binodal curve, spinodal curve and critical point of multi-phase equilibrium were dirived in the Flory-Huggins theory. A software predicting liquid-lquid phase equilibrium of polymer hybrid system has been developed by development tool delphi, and proved right by comparision between the calculated value and literature data. Additionally, the software provided different interaction parameters models to adapt to different systems of calculation of phase equilibrium.The software predicted the liquid-liquid phase equilibrium of PLA/PM binary blends showing that thay were completely immiscible at room temperature which consistent with the result of the experiment, measuring the thin film by microscope. Furthermore, it was predicted the phase equilibrium of solvent/PLA and solvent/PM solution systems to choose glyceryl triacetate and acetyl triethyl citrate which could solute PLA and PM by comparing the miscibility of the various solvents and the two polymers. Then it was predicted that the selected solvents/PLA/PM ternary hybrid systems would be miscible while PM was vary little by the predicting software, and as the temperature increased, a slight increase in solubility region. This calculated result could provide theoritical guidance for further study.In order to better apply to the pratical application of the systems, this paper, based on the Flory-Huggins theory, also developed a software associated with liquid-liquid phase equilibrium data for binary polymer blends. It also proposed a new algorithm besides the common algorithm "Tie-line method" and " Non tie-line method". The new algorithm could be associated with the non-line liquid-liquid equilibrium data, and the requirement of initial parameters was lower. Using the associating software, selecting different interaction parameter models, it associated with the experiment data of liquid-liquid equilibrium for PM/tributyl citrate and PM/glyceryl triacetate. By comparision, the result correlated by the Flory-Huggins model, whose interaction parameters related to composition, was satisfied.The two softwares developed by this paper could applied to industrial applications and scientifical research such as new material development and molecular thermodynamic theories and had practical value and theoretical significance.