Epoxy Modified Bio-based Hyper branched Polyurethane/Clay Nanocomposites: Rheology and Biodegradability

Abstract

The rheological study of nanocomposite has significant contribution not only in processing but also reveals the dispersion state of the nano reinforcing agent in the matrix. This study divulges the rheological behavior of epoxy cured Mesua ferrea L. seed oil modified hyper branched polyurethane/clay nanocomposites. The influence of different preparative techniques viz. in situ and ex situ on the rheological properties was also investigated. The nanocomposites prepared by in situ technique showed higher viscosity, storage modulus (2.8 x 103 Pa), and loss modulus (3.3 x 102 Pa) than the nanocomposites prepared by ex situ technique (storage modulus of 2.1 x 103 Pa; loss modulus of 2.3 x 102 Pa). However, the viscosity of all the nanocomposites was found to be higher than the pristine polyurethane system.  All the nanocomposites showed shear thinning behaviors both in steady and oscillation mode. The rheological characteristics of the nanocomposites were found to be strongly dependent on the loading of the clay. The effects of the frequency and temperature on storage modulus, loss modulus and complex viscosity have also been investigated. Another fascinating property exhibited by the nanocomposites was the dramatic increment of the biodegradability compared to pristine polyurethane.

Keywords:  Hyperbranched polyurethane, nanocomposites, rheology, shear thinning behavior, biodegradation