In orthopaedic bearing manufacture, compression moulding of Celanese GUR 2105-1 virgin powder requires a low-shear consolidation protocol because the polymer has a weight-average molar mass above 1.5 × 10⁶ g/mol and does not produce a measurable melt flow rate under ISO 1133-1. The powder is conditioned at 23 °C and 50 % RH to moisture uptake below 0.01 wt% before charging, and the cavity is filled with slow, low-turbulence motion to minimise electrostatic particle bridging. Consolidation takes place at 180–220 °C under 10–20 MPa, with hold time scaled at 1 min/mm of maximum section thickness. The preform is cooled under pressure below 60 °C before demoulding, then machined into bearing preforms, acetabular liners, or tibial inserts. Density of the consolidated stock is checked in the 0.930–0.940 g/cm³ range, and tensile properties are measured under ASTM D638-14. For implantable components, powder and consolidated forms are specified under ISO 5834-1:2019, ISO 5834-2:2019, and ASTM F648. If terminal sterilisation is performed by gamma irradiation at 25–40 kGy, free radicals generated in the crystalline regions require post-irradiation annealing or remelting because residual oxidation can raise the carbonyl index above 0.1 after accelerated aging per ASTM F2003. Wear testing is conducted on pin-on-disc or hip simulator equipment under ASTM F732, with counterface roughness and lubricant composition recorded as test variables because they affect gravimetric wear rate. The main failure mode in compression moulding is incomplete void elimination, observed as sub-surface porosity in ultrasonic inspection when initial compaction pressure is insufficient or the breathing sequence is shortened. Mould release agents are avoided in implant production because residual surface chemistry can interfere with sterilisation and wear behaviour.

What Limits Continuous Ram Extrusion of GUR 2105-1 Wear Profiles?

The continuous ram extrusion process applied to GUR 2105-1 requires a vertical or horizontal ram extruder with a heated barrel, a forced-fill feed throat, and a long shaping die, because screw extrusion cannot develop stable forward flow in a polymer whose zero-shear viscosity approaches 10⁸ Pa·s at 190 °C. Barrel temperatures are held at 200–240 °C while the die is controlled at 180–220 °C to balance consolidation at the powder plug and shape stability at the profile surface. Die entry pressure normally lies between 15 MPa and 40 MPa, but the practical ceiling is set by frictional heat generated at the powder plug boundary rather than by hydraulic capacity. For profiles thicker than 50 mm, ram speed is kept below 0.3 m/h to avoid a central unconsolidated core and thermal runaway. The extrudate is cooled through a multi-zone water bath at 60–90 °C, then post-annealed at 120 °C for 2 h before machining into chain guides, wear strips, scraper blades, and conveyor liners. Incoming powder lots are checked for bulk density, particle-size distribution, and moisture because batch-to-batch drift shifts consolidation onset and can alter die pressure by 5–10 %. Dimensional compliance for rod and profile stock is evaluated under ISO 11542-2 and ASTM D4020, with tensile elongation measured by ISO 527-2. The main operational boundary is oxidative degradation when barrel dead zones exceed 240 °C; discolouration and loss of notched impact resistance appear before tensile strength decreases. Ram extrusion is unsuitable for thin-wall profiles below 5 mm because melt fracture and surface roughness cannot be controlled at the low shear rates available.

Sintered porous structures made from GUR 2105-1 powder are produced by depositing a controlled powder layer into a metal mould, then applying low contact pressure of 1–5 MPa while heating to 140–170 °C for a controlled dwell. Under these conditions the particle boundaries fuse without complete densification, leaving interconnected voids whose size distribution is influenced by powder fraction, particle morphology, and packing density. After cooling, the sintered billet is machined into vent plugs, silencer elements, aeration discs, and filter support cores for chemical-processing equipment. The porous volume is commonly specified between 20 % and 40 %, and pore-size distribution is measured by mercury intrusion porosimetry under ISO 15901-1. The main process limitation is the narrow temperature window between particle fusion and pore collapse; above 175 °C the void fraction drops rapidly and the part begins to densify into a non-porous sheet. For solvent-contact service, the sintered component is subjected to immersion tests in the relevant process fluids, with a dimensional change below 1 % in outer diameter used as the acceptance criterion. Porous parts are not recommended for applications requiring tensile strength above 10 MPa because the voids act as stress concentrators, and fatigue resistance under cyclic pressure is lower than that of fully consolidated UHMWPE.

Gel Spinning and Hot Drawing Parameters for UHMWPE Fibre from GUR 2105-1

Solution processing of GUR 2105-1 into high-modulus fibre involves dispersing the powder in decalin or paraffin oil at a concentration of 5–10 wt%, heating the slurry under nitrogen to 120–180 °C, and extruding through a spinneret into a water or solvent extraction bath. The as-spun gel fibre is drawn in a first-stage wet draw at 5:1–10:1 and 90–120 °C, extracted to remove the solvent, and then subjected to a second-stage hot draw at 130–150 °C. A third solid-state draw can raise the accumulated ratio above 40:1, yielding a single-filament tensile modulus above 50 GPa and a tensile strength above 1.5 GPa when tested under ISO 2062 or ASTM D3379. The process window is constrained by entanglement density remaining after dissolution; insufficient mixing leaves undissolved gels that block the spinneret, while over-shearing in a twin-screw mixer with an L/D ratio of 40:1 reduces the maximum attainable draw ratio and final modulus. Batch-to-batch variation in molecular weight distribution of the powder is monitored by solution viscosity because higher plateau viscosity shifts the dissolution temperature upward and narrows the draw window. After drying, the fibre is wound under controlled tension to maintain a denier coefficient of variation below 2 %, which is a typical acceptance limit for cut-resistant glove and ballistic panel yarn. At total draw ratios below 10:1, residual solvent content can exceed 0.1 wt% and compromise downstream weaving quality, so the route is not used for products requiring high elongational toughness without full drawing.

Microporous separator substrate based on GUR 2105-1 is prepared by blending the virgin powder with a liquid plasticizer, typically mineral oil or decalin, at a polymer-to-plasticizer weight ratio between 70:30 and 85:15, then compacting and extruding the paste through a slit die at 190–230 °C. The cast sheet is cooled to induce phase separation and stretched biaxially at 3:1–7:1 in both machine and transverse directions. The plasticizer is then removed with a volatile solvent such as n-hexane, leaving a sub-micron pore network with a Gurley number between 200 s/100 mL and 600 s/100 mL determined under ASTM D726. The resulting membrane is used as a substrate for lithium-ion battery separators or as a chemical filtration layer. For battery separator applications, shutdown temperature and puncture resistance are the controlling properties; published data for GUR 2105-1 in this specific membrane configuration is limited, but related UHMWPE gel films show a shutdown response near 135 °C and a puncture strength above 0.4 N/µm when tested by a standard needle probe method. The main process constraint is solvent recovery cost and the need to maintain a controlled evaporation profile to prevent surface skin formation; a surface skin layer below 1 µm can increase Gurley number by more than 20 % and reduce separator ionic conductivity.

When GUR 2105-1 Is Used as a Dry-Sliding Bearing Insert in Food-Processing Machinery

Dry-sliding bearing inserts machined from compression-moulded GUR 2105-1 sheet are installed in bottling lines, packaging machinery, and food-processing conveyors where external lubrication is not permitted. The sliding velocity is normally limited to 0.5 m/s and the contact pressure to 3 MPa because the polymer's thermal conductivity is approximately 0.40 W/m·K, restricting frictional heat dissipation. The dynamic coefficient of friction against a stainless-steel counterface is typically 0.10–0.15 under ASTM D1894, and wear factors are measured on a block-on-ring apparatus under ASTM G176. Compliance for direct food contact is evaluated under FDA 21 CFR 177.1520 and EU 10/2011, with migration testing performed according to the relevant food-simulant exposure conditions. The insert is not recommended for continuous service above 80 °C or in contact with strong oxidising acids; dimensional change from water absorption is below 0.01 % when tested under ASTM D570. The absence of external lubricant means that wear debris accumulation in the machine environment must be monitored; for high-speed lines above 0.5 m/s, a water rinse or external cooling lowers the surface temperature and reduces the risk of localised melting at the bearing edge.