for Compression Molding a Cross-linked Preform The invention carried out at
our end has helped us to deliver improved bearings for use in orthopedic
implant prosthesis. This include particularly in methods for making high
molecular weight polyethylene or UHMWPE bearings by molding a cross- linked
preform through application of sufficient heat and pressure.
These UHMWPE resins are commonly used for:
- Bearings in hip, knee, shoulder and elbow prostheses
Here, the stock or molded bearings are irradiated and is subsequently
heat treated/heat annealed. The irradiation helps in generating molecular
cross-links and free radicals where the free radicals are subsequently
eliminated by heat treating processes.
The invention is also directed to method for molding bearing from preform
that has previously been cross-linked by obtaining a preform and placing it
in press mold defining:
- Desired bearing shape
- Near net shape
This is done by applying heat and pressure in mold to form bearing.
Here, the preform may be produced from irradiated polymer resin for forming
cross-links and free radicals followed by molding process. Further, in some
embodiments, irradiated UHMWPE preforms may already be heat treated for
quenching free radicals.
The present invention is:
- Designed to reduce amount of wear debris generated from UHMWPE
- Such wear debris is associated with bone and soft tissue
deterioration leading to implant loosening that may necessitate even
- Present invention improves wear resistance of UHMWPE bearings