A method for preparing a rotomoulded article having asymmetrical layering, wherein the rotomoulded article is a car door wherein the outside part of the door is prepared from painted polyamide and the inside part of the door is prepared from a mixture of polyethylene, grafted polyethylene and ionomer, the method comprising the steps of: a) providing a mould for rotomoulding consisting of 2 or more portions insulated from one another; b) thermally insulating one or more portions of the mould, leaving the remaining portions not insulated; c) heating the non-insulated portions of the mould; d) injecting a first polymeric material in the heated mould, said polymeric material constituting the outer layer of the finished article for the part of the mould that is not thermally insulated, and said polymeric material being selected from a composition comprising from 40 to 100 wt%, based on the weight of the composition, of homopolymers or copolymers of polyamide, and from 0 to 60 wt% of a functionalised polyolefin or of a PO grafted to a non-polyolefin in the form of a block copolymer g-NPO) or of an ionomer or a combination thereof, and submitting the mould to rotation about two perpendicular axes; e) removing the thermal insulation; f) injecting a second polymeric material in the heated mould, different from the first polymeric material of step d), wherein said second polymeric material constitutes the outer layer of the finished article for the part of the mould that was thermally insulated during the injection of the first resin and said second polymeric material comprising from 70 to 99 wt%, based on the weight of said polymeric material, of a polyethylene resin or a combination thereof, preferably from 80 to 99 wt% and more preferably from 85 to 98 wt%, and from 1 to 30 wt%, preferably from 1 to 20 wt% and more preferably from 2 to 15 wt% of a combination of grafted polyethylene and ionomer, and submitting the mould to rotation about two perpendicular axes; g) optionally repeating steps b) through f) or step f) alone as many times as desired; h) retrieving a rotomoulded article having asymmetrical layering. a) providing a mould for rotomoulding consisting of 2 or more portions insulated from one another; b) thermally insulating one or more portions of the mould, leaving the remaining portions not insulated; c) heating the non-insulated portions of the mould; d) injecting a first polymeric material in the heated mould, said polymeric material constituting the outer layer of the finished article for the part of the mould that is not thermally insulated, and said polymeric material being selected from a composition comprising from 40 to 100 wt%, based on the weight of the composition, of homopolymers or copolymers of polyamide, and from 0 to 60 wt% of a functionalised polyolefin or of a PO grafted to a non-polyolefin in the form of a block copolymer g-NPO) or of an ionomer or a combination thereof, and submitting the mould to rotation about two perpendicular axes; e) removing the thermal insulation; f) injecting a second polymeric material in the heated mould, different from the first polymeric material of step d), wherein said second polymeric material constitutes the outer layer of the finished article for the part of the mould that was thermally insulated during the injection of the first resin and said second polymeric material comprising from 70 to 99 wt%, based on the weight of said polymeric material, of a polyethylene resin or a combination thereof, preferably from 80 to 99 wt% and more preferably from 85 to 98 wt%, and from 1 to 30 wt%, preferably from 1 to 20 wt% and more preferably from 2 to 15 wt% of a combination of grafted polyethylene and ionomer, and submitting the mould to rotation about two perpendicular axes; g) optionally repeating steps b) through f) or step f) alone as many times as desired; h) retrieving a rotomoulded article having asymmetrical layering.