Process for producing a new class of ultra-high-molecular-weight polyethylene orthopaedic prostheses with enhanced mechanical properties

Claim 1

A method for producing an UHMWPE product with enhanced planar mechanical properties comprising: solid-state deforming an initial UHMWPE semicrystalline morphologoy under compression in a mold comprising a mold cavity and a perimeter zone including: orienting a polymer preform having a volume greater than said mold cavity, thereby providing an excess amount of the polymer and extending it in more than one direction in the mold cavity and the perimeter zone to an extent which is limited by the material properties of the polymer under the employed processing conditions, which include the temperature of the initial UHMWPE semicrystalline morphology, the mold temperature, the compression load and the geometrical configuration of the mold cavity and the perimeter zone, deforming the excess amount of polymer past the boundaries of the mold cavity into a perimeter zone surrounding the mold cavity for the purpose of controlling the deformation of the polymer product in the mold cavity, cooling the oriented and extended UHMWPE under compression to ambient temperature for maintaining the maximum orientation and extension attained during the said solid-state deformation process, separating the polymer product in the mold cavity from the product in the perimeter zone of the mold cavity, said solid-state deformation process taking plass at a mold temperature and compression conditions to obtain an UHMWPE product having a markedly transformed morphology, as compared with the said initial UHMWPE morphology, said product comprising oriented and extended molecular chains in more than one direction and exhibiting mechanical properties in more than one direction, that are higher than those of the initial UHMWPE morphology prior to its deformation, the magnitude depending on the extend of deformation.

Claim 2

A method for producing an UHMWPE product with enhanced planar mechanical properties comprising: solid-state deforming an initial UHMWPE semicrystalline morphologoy under compression in a mold comprising a mold cavity and a perimeter zone including: orienting a polymer preform having a volume greater than said mold cavity, thereby providing an excess amount of the polymer and extending it in more than one direction in the mold cavity and the perimeter zone to an extent which is limited by the material properties of the polymer under the employed processing conditions, which include the temperature of the initial UHMWPE semicrystalline morphology, the mold temperature, the compression load and the geometrical configuration of the mold cavity and the perimeter zone, deforming the excess amount of polymer past the boundaries of the mold cavity into a perimeter zone surrounding the mold cavity for the purpose of controlling the deformation of the polymer product in the mold cavity, cooling the oriented and extended UHMWPE under compression to ambient temperature for maintaining the maximum orientation and extension attained during the said solid-state deformation process, separating the polymer product in the mold cavity from the product in the perimeter zone of the mold cavity, said solid-state deformation process taking plass at a mold temperature and compression conditions to obtain an UHMWPE product having a markedly transformed morphology, as compared with the said initial UHMWPE morphology, said product comprising oriented and extended molecular chains in more than one direction and exhibiting mechanical properties in more than one direction, that are higher than those of the initial UHMWPE morphology prior to its deformation, the magnitude depending on the extend of deformation.