Viscoelastic models in green composites from PLA and hazelnut shell fillers with a natural plasticizer from epoxidized linseed oil

Abstract

In a same way to polymeric materials, some composite materials as it is the case of green composites, are characterized by a viscoelastic behaviour which plays a key role in their mechanical properties with time. The use of some engineering materials could be restricted as their mechanical properties could be highly affected by temperature or time. For this reason, this work is focused on the modeling of the viscoelastic behaviour of this biomaterial composite with a biobased polymer matrix from poly(lactic acid) and a lignocellulosic reinforcement/filler coming from hazelnut shell with different plasticizer content. In particular, a biobased plasticizer, namely epoxidized linseed oil (ELO) has been employed. A first approach to the viscoelastic behaviour of these composites is summarized in this work. The Maxwell model considers a series combination of the elastic reponse (represented by a spring) and the viscous contribution (represented by a dashpot). The Kelvin-Voigt model considers the same physical elements (spring and dashpot) but coupled in parallel. As these two basic visceolastic models show important restrictions regarding the real viscoelastic behaviour, this work also considers a series combination of the Maxwell model and the Kelvin-Voigt model, known as Burgers model. This works focuses on determining the different parameters of the Burgers model to fit experimental data from PLA-hazelnut shell flour biocomposites with varying plasticizer (ELO) content.