Uso de extensor de cadeia visando a modificação da estrutura molecular do PET.

Abstract

This work is concerned with the effect of a multifunctional styrenicacrylic- epoxi oligomer (Joncryl - POLYAD PR 002) - marked as a chain extender for condensation polymers - on the molar mass of poly(ethylene terephthalate), in virgin (PET-V) and post-consumer recycled (PET-PC) forms. The purpose of incorporation of additive is to compensate the loss of molar mass of these polymers during processing due to degradation. The PET-V and PET-PC, neat and with the chain extender added, were compounded in a Haake Rheomix 3000 internal mixer, fitted with high intensity rotors. The effect of rotor speed, additive concentration, and reprocessing on the viscosity and molar mass of the polymers was estimated from torque measured during processing and from intrinsic viscosity measured after processing. The addition of chain extender resulted in the increase of viscosity and molar mass, the largest values obtained for resins processed at 60 rpm with 1.5% additive. Reprocessing PET-V with 1.5% additive resulted in a drop of torque and viscosity, but the molar mass of the reprocessed material was superior to the PET-V compounded without chain extender, suggesting that the additive did not generate byproducts that may degrade the polymer on further processing. Moreover, when 1.5% chain extender were added to the reprocessed material, viscosity and molar mass increased again, reaching values close to the ones obtained for the polymer reprocessed once with the additive. The result showed that the chain extender tested compensated the loss o molar mass, not only during processing, but on reprocessing too. The molar mass values estimated from the data processing were confirmed experimentally, indicating that the analysis of the torque-time curve in the internal mixer is a fast and accurate tool for evaluating the efficiency of chain extension of PET processed and reprocessed.