A polymer composition having improved processing properties, in particular improved crystallization behavior, comprising a semi-aromatic polyamide and a graphene material. The graphene material may be a nano-graphene platelet. The semi-aromatic polyamide may comprise recurring units obtainable by a polycondensation reaction between at least one aromatic diamine and at least one non-aromatic diacid or derivatives thereof and/or recurring units obtainable by a polycondensation reaction between at least one aromatic diacid or derivatives thereof and at least one non-aromatic diamine. The composition may further comprise a polyamide different than the semi-aromatic polyamide. The composition may further comprise a filler.