This invention relates to a composite material which is a copolymer of at least (i) a functionalised carbon nanoparticle, (ii) a polyol, (iii) a compound comprising at least two isocyanate groups, wherein the functionalised carbon nanoparticle and the polyol are covalently bonded by a urethane and optionally a urea and/or an amide linkage, and a process for producing the same. Such composite materials are suitable for use in moulded articles for implantation within a mammal.
