New Reactive Formulations For Polypropylene Foams

Abstract This work focuses on reactive extrusion to design polypropylene (PP) chains with long and short branching to obtain non‐linear behavior for the synthesis of low‐density foams (<100 kg m −3 ) using a batch supercritical carbon dioxide (scCO 2 ) foaming process. From a maleic anhydride (MA) grafted PP (PP‐g‐MA), the long‐branched chains are performed using [MA]/ [OH] reaction (with Sorbitol alcohol). On the other hand, short branched chains are made from the hydrolysis/condensation of amino‐alkoxysilane (3‐Aminopropyl‐triethoxysilane, APTES) in situ grafted onto PP chains through the ([MA]/NH 2 ] reaction). The results show the need to combine both systems to reach the optimum of the rheological behavior (linear and non‐linear) to obtain a low‐density foam. On the other hand, the foaming behavior of polypropylene/polyamide 6 (PP/PA6) polymer blends at T = 180 °C is also investigated as another way to control the rheology and foamy behavior. At this temperature, T = 180 °C, the PA6 phase behaves as solid dispersed particles in a viscoelastic liquid PP matrix. Finally, this study shows the influence of PA6 concentration on the foaming and foam morphology correlated to a rheological study (shear and extensional) and mechanical compressive properties.