The present invention provides a plant based material with high tensile strength, with high E-modulus, which have low water absorption, which can be injection molded, and which can be melted and remolded. The materials of the invention may be composite materials prepared by extrusion of a mixture comprising a) surface modified plant parts consisting of finely divided plant parts O-linked to one or more groups of the structure (I); b) polymethyl methacrylate (PMMA); c) thermoplastic polymer.