Résumé
First, natural fillers composed of cellulose, lignin and fillers with a varying lignin/cellulose ratio (flax, jute, curauà fibers and miscanthus stem fragments) were used to prepare composites with polypropylene using the same procedure, with or without a maleic anhydride–grafted polypropylene (MA-g-PP) coupling agent. A clear acceleration of the crystallization kinetics was observed in the presence of miscanthus stem fragments. A clear effect of the nature of the polymers present in the filler was observed. There is a direct relationship between the values of the Avrami kinetic constant k for the six fillers and their lignin content, the more effective to enhance crystallization kinetics being pure cellulose. Lignin has no effect onto the crystallization kinetics of polypropylene. A second study detailed the role of vegetal tissues which were separated from maize stems. Clear differences were seen depending on the type of tissue (pith, parenchyma cell, vascular vessels, epidermis, sclerenchyma parts).This study is enabling to identify key parameters in polypropylene transcrystallinity in the presence of plant tissues.