Polymer compositions comprising poly-glycolic acid (PGA) or a functional derivative thereof with a tensile strength of at least 1200 MPa are disclosed. Processes suitable for manufacturing said compositions are also described, comprising rendering PGA into an amorphous state then drawing to form a highly orientated polymer structure. The polymer compositions can be used to make artefacts, for example sutures, or used in combination with other polymers or non-polymeric substances to produce other artefacts, for example medical devices suitable for implantation into the human body. Processes for the production of said artefacts are also described.