Reactive compatibilization of poly trimethylene terephthalate (PTT) and polylactic acid (PLA) using terpolymer: Factorial design optimization of mechanical properties

A reactive extrusion route was employed to compatibilize blends of PTT and PLA by the addition of a random ter polymer of ethylene, methyl acrylate, and glycidyl methacrylate (EMAGMA) and multifunctional epoxy chain extender. Mixed level full factorial design was used to investigate the strength properties of the resulting blends. Using analysis of variance, main and interaction effects of terpolymer, chain extender and screw speed on mechanical properties of the blends were investigated. Multiple linear regression models were fitted and their adequacy was verified by checking residual plots. Most influencing factor for tensile strength was the terpolymer, while the impact strength was significantly affected by all three factors and one of the interaction effects. Phase morphology indicated a two-phase structure in which PLA-EMAGMA phase was dispersed as domains in the continuous PTT matrix. Domain size was found to decrease with the increasing concentration of the terpolymer at higher shear rates. Reduced particle size and interparticle distance was believed to be the main reason behind impact toughening in the blends. PTT70-PLA30/terpolymer (85/15) blends with 0.5 phr chain extender processed at 200 rpm with impact strength of 122 J/m and tensile strength of 44 MPa has been selected as the optimum blend formulation. (C) 2016 Elsevier Ltd. All rights reserved.