(640g) Welding Immiscible Polymer with Co2

Polymer adhesion between two immiscible polymers is usually poor because there is little interpenetration of one polymer into the other at the interface. Thus, increasing the width of the interfacial zone can enhance adhesion and mechanical properties. In principle, this can be accomplished by exposing the solid polymer materials to high pressure CO2. The CO2 acts as a common solvent and promote interpenetration. It also increases the mobility at the interface which helps to promote the ?welding? of the two polymers. The welding process could be carried out at elevated temperatures to facilitate interpenetration kinetics. After exposing and swelling the polymers with CO2 and increasing the interfacial zone, the system would be quickly depressurized and allowed to return to room temperature. The key here is that the system will not have enough time to return to its equilibrium condition. The new, thicker, and better adhering interface will be retained. This condition (kinetically stable interface) will remain for as long as the polymer use temperature is well below the glass temperature of either polymer.

A combination of the gradient theory of inhomogeneous systems and the Sanchez-Lacombe Equation of State was used to investigate this phenomenon. We can calculate the interfacial density profile, and the interfacial thickness between the two polymers. By comparing the interfacial thickness with and without CO2, we can discuss the feasibility of CO2 in assisting polymer welding.