Advances in chain extender technology for polyesters
May 10-15, 2015
Polyesters are an important class of polymers useful for many applications such as bottles, fibers, bags, strapping, foams and films. During compounding at elevated temperatures in combination with high shear stress and the presence of traces of moisture, however, polyesters may undergo degradation reactions by various mechanisms including hydrolysis of the ester bonds. As a result the Intrinsic Viscosity (IV), mechanical properties and melt strength can decrease and limit the final useful applications possible. Chain extenders are commonly added during processing to “re-build” the molecule weight of the polyester by reacting with the end groups and connecting chains back together. In this work, we report on the development of multifunctional epoxy and oxazoline chain extenders for PET and PLA polymers. The reactivity of the chain extenders were measured by DSC and found to be dependent on the polymer structure. In addition, torque measurement in a conical twin screw micro compounder was conducted to show performance as a function of functionality and molecular weight for both PET and PLA. A critical parameter which influences the commercial success of the chain extender is the thermal stability of the material which influences the final free monomer content in the final compounded article. Our work shows that this is heavily dependent on the polymer composition and process conditions and with proper selection of both, chain extenders with high thermal stability leading to low free monomer content articles can be developed.
Tim Klots, Jon Debling, and Simone Schillo, "Advances in chain extender technology for polyesters" in "Polymer Reaction Engineering IX", E. Vivaldo-Lima, UNAM; J. Debling, BASF; F. Zaldo-Garcia, CP-COMEX; J. Tsavalas, Univ. of New Hampshire Eds, ECI Symposium Series, (2015). http://dc.engconfintl.org/polymer_rx_eng_IX/13