Abstract: A polyolefin plaque is made by hot compaction of an assembly of fibers of the oriented polymer. It has been found to be beneficial to subject the fibers to a prior crosslinking process. Hot compaction is then less temperature-sensitive and produces plaques with excellent hot strength properties. Preferably the fibers have been subjected to prior stages of irradiation and annealing, both in a non-oxidising environment, for example acetylene.

Abstract: A polyolefin plaque is produced by hot compaction of an assembly of melt spun oriented fibers. It has been found that good compaction can be achieved at relatively low compaction pressures, less than 10 MPa. Compaction can be carried out in an autoclave, rather than in a hot compaction press, and the mechanical properties of plaques so produced range from good to excellent.

Abstract: A polyolefin plaque is made by hot compaction of an assembly of fibers of the oriented polymer. It has been found to be beneficial to subject the fibers to a prior crosslinking process. Hot compaction is then less temperature-sensitive and produces plaques with excellent hot strength properties. Preferably the fibers have been subjected to prior stages of irradiation and annealing, both in a non-oxidizing environment, for example acetylene.

Abstract: A polyolefin plaque is produced by hot compaction of an assembly of melt spun oriented fibres. It has been found that good compaction can be achieved at relatively low compaction pressures, less than 10 Pa. Compaction can be carried out in an autoclave, rather than in a hot compaction press, and the mechanical properties of plaques so produced range from good to excellent.

Abstract: Polymeric monoliths having high stiffness and strength can be produced by heating an assembly of polymer fibres under a contact pressure to a temperature at which a proportion of the fibre is selectively melted and then compressing the assembly. Preferably at least 5% of the polymer is melted so that on compression the molten materials fills the voids within the assembly. The use of polyolefin fibres especially melt spun polyethylene fibres is preferred. The products are useful e.g. as orthodontic brackets, bone prostheses and in body armour.

Abstract: Polymeric monoliths having high stiffness and strength can be produced by heating an assembly of polymer fibres under a contact pressure to a temperature at which a proportion of the fibre is selectively melted and then compressing the assembly. Preferably at least 5% of the polymer is melted so that on compression the molten materials fills the voids within the assembly. The use of polyolefin fibres especially melt spun polyethylene fibres is preferred. The products are useful e.g. as orthodontic brackets, bone prostheses and in body armour.