Celanese UHMW-PE 4222-5 is an ultra-high-molecular-weight polyethylene powder grade supplied as a free-flowing powder with molecular weight controlled through solution viscosity rather than melt flow rate. Because the polymer remains in the solid state during processing, melt flow rate values under ISO 1133-1:2022 are not used for lot release; the grade is specified by a viscosity number of 2000–2300 mL/g measured in decalin at 135 °C under ISO 1628-3:2010. The published density range is 0.930–0.935 g/cm³ under ISO 1183-1:2019, and the powder bulk density is typically 0.40–0.45 g/cm³ under ISO 60:1977. The grade is intended for solid-state processing by ram extrusion and compression moulding of wear components, guide rails, chain guides, filtration plates, and pump parts. Dynamic coefficient of friction against polished steel ranges from 0.20–0.30 when tested under ASTM D1894, and water absorption after 24 h at 23 °C is below 0.01% under ISO 62.

The powder particle size distribution is controlled to support uniform feeding. Median particle size is typically in the 120–180 µm range, measured by laser diffraction under ISO 13320:2020. The fines fraction below 63 µm is limited to prevent dusting and irregular compaction in ram extrusion feed throats. Batch-to-batch variation in particle size distribution should be monitored by sieving under ASTM D1921; deviations above ±10% in the fraction retained on a 125 µm sieve can shift compaction density and produce variation in extruded part dimensions.

The material is not melt-processable. Unlike high-molecular-weight high-density polyethylene grades that can be run on blown-film or sheet lines, 4222-5 has no practical melt-flow value under ISO 1133-1:2022 because the molecular chains remain entangled below the degradation temperature. Attempting to process it through a single-screw or twin-screw extruder results in high torque, poor output, and oxidative damage before a pumpable melt is formed. This distinction is the primary difference from standard HDPE and high-molecular-weight HDPE products; 4222-5 must be consolidated by pressure-assisted sintering rather than melt pumping.

How does 4222-5 differ from lower-viscosity UHMW-PE grades?

The grade sits between GUR 2122 and GUR 4120 in the Celanese UHMW-PE series. The higher viscosity number of 4222-5 relative to GUR 2122 produces improved abrasion performance in sand-slurry testing under ASTM G75, but increases ram extrusion pressures by approximately 10–15% on the same die. Compared with standard high-density polyethylene, 4222-5 shows a lower tensile modulus of 700–900 MPa under ISO 527-2/1BA/50 and a notched Izod impact strength that is reported as no break at 23 °C under ISO 180/A. Lower-viscosity grades such as GUR 2122 are easier to consolidate at lower pressures but exhibit higher wear volume loss; higher-viscosity grades such as GUR 4150 and GUR 4170 provide further abrasion resistance at the cost of longer sintering cycles and higher die pressures. The selection of 4222-5 is therefore driven by the balance between wear life and processability in parts with wall thicknesses above 10 mm.

The following representative values are compiled from the manufacturer’s technical data sheet and adjacent grade literature for 4222-5. Lot-specific certification data should be requested for applications requiring traceable values.

No melt flow rate value is assigned because the material does not flow under conventional melt-flow testing.

Ram extrusion and compression moulding boundary conditions

Ram extrusion of 4222-5 requires a heated die with a temperature profile of 190–220 °C at the die inlet and a heated mandrel maintained at 120–180 °C to prevent premature solidification. Extrusion pressures at the ram face typically reach 25–40 MPa, with die land lengths of 30–50 mm and compression ratios between 2.5:1 and 4:1. The polymer does not form a homogeneous melt; therefore, single-screw and twin-screw extruders are not recommended regardless of screw L/D ratio. In compression moulding, platen temperatures of 200–230 °C, applied pressures of 5–10 MPa, and dwell times of 10–15 min per 10 mm of thickness are typical. Cooling under pressure at 10–20 K/min is required for wall thicknesses above 20 mm to control shrinkage and void formation. If the powder has been stored at relative humidity above 60%, hot-air drying at 80 °C for 4 h is advised before processing.

The consolidation mechanism is sintering rather than melt fusion. At die temperatures below 190 °C, particle boundary healing is incomplete, and tensile strength can fall by 30–50% relative to the datasheet value. Above 220 °C, oxidative chain scission increases the carbonyl index and reduces notched Izod impact from no break to 20–40 kJ/m², a property cliff-edge that is not visible in standard density measurements. Therefore, the acceptable processing window is approximately ±15 K around 205 °C for long residence times.

The thermal conductivity of 4222-5 is approximately 0.40–0.50 W/(m·K), which is lower than that of HDPE. This limits cooling rates in sections above 20 mm and makes internal residual stress more difficult to remove. Cooling rate after sintering controls final crystallinity and dimensional stability. Rapid cooling at 10–20 K/min suppresses secondary crystallite growth and produces lower crystallinity, which improves toughness but increases post-machining shrinkage. Slow cooling below 5 K/min increases crystallinity and hardness but can generate internal voids and dimensional variation exceeding ±1.5% in thick sections. Production lines commonly maintain pressure until the component core drops below 100 °C before demoulding.

When replacing GUR 2122 or GUR 4120 with 4222-5 in wear components

Substitution of GUR 2122 with 4222-5 increases sand-slurry abrasion resistance under ASTM G75, but the higher viscosity number raises the pressure required to fill a given ram extrusion die by approximately 10–15% and may require a 5–10 K increase in die temperature. Replacing GUR 4120 with 4222-5 normally reduces die pressure slightly and improves powder flow in free-flowing feeding systems, but the wear rate may increase in high-load applications. In both cases, the replacement is not a drop-in for injection moulding lines because the grade remains solid-state-processable only. For parts thicker than 30 mm, a post-forming annealing step at 100–120 °C for 2 h is often applied to reduce residual stress and improve dimensional stability after machining.

Sand-slurry abrasion testing under ASTM G75 for UHMW-PE grades typically uses a 1:1 sand-to-water mixture by volume and a total cycle count of 5000. Under these conditions, 4222-5 is reported to show lower volume loss than GUR 2122 and HDPE, with the difference becoming significant after the first 1000 cycles. The exact wear rate is dependent on slurry velocity, sand particle size distribution, and the hardness of the mating surface; published data for this specific configuration in high-velocity slurry transport is limited.

Compliance of 4222-5 must be verified against the supplier’s current regulatory certifications. The base olefin polymer may be evaluated under FDA 21 CFR 177.1520 for food-contact use when the grade is listed in the supplier’s certification, and under EU 10/2011 for plastics intended for food contact. For food-contact use in the European Union, overall migration must be below 10 mg/dm² for many applications under EU 10/2011, but final verification depends on surface-to-volume ratio and simulant conditions. Electrical and electronic applications require confirmation of RoHS Directive 2011/65/EU limits for lead, cadmium, mercury, hexavalent chromium, PBB, and PBDE. The grade is typically considered REACH compliant under Regulation (EC) No 1907/2006 as a polymer, but article-level SVHC obligations remain with the downstream user. For load-bearing implant components, the grade must be evaluated under ISO 10993-1 and ISO 5834-2 because polymer powder characteristics and stabilizer packages vary by lot.

Continuous service above 80 °C under load is not recommended for 4222-5 because creep and wear accelerate sharply near the Vicat softening temperature. The material is incompatible with strong oxidizing acids at temperatures above 60 °C and with high-aromatic hydrocarbon environments that can cause softening and dimensional change. The grade should not be exposed to ultraviolet radiation for extended outdoor service without a UV-stabilized formulation; otherwise surface cracking and molecular weight reduction occur. Sterilization by steam at 121 °C may be performed only for short cycles and with the understanding that repeated autoclave exposure can increase crystallinity and reduce toughness. Gamma irradiation above 25 kGy may cause oxidative degradation and increase the measurable carbonyl index; if irradiation is required, the component should be stored under nitrogen and tested for molecular weight retention.

After forming, 4222-5 is commonly machined with high-speed steel or tungsten carbide tooling at cutting speeds of 300–600 m/min. The low thermal conductivity of UHMW-PE means that local frictional heating can exceed 150 °C; water or air cooling is required to prevent dimensional distortion. Tool geometry should use positive rake angles and polished chip flutes to avoid smearing and built-up edge on the polyolefin surface.

Typical production-scale uses for 4222-5 include chain guides, wear strips, star wheels, filtration plates, and pump volutes produced by ram extrusion and subsequent machining. In these applications, the product is selected over lower-molecular-weight UHMW-PE grades when the part requires a measurable improvement in abrasion resistance without moving to the higher die pressures of GUR 4150 or GUR 4170. Published data for this specific configuration in high-velocity slurry transport is limited; pump users should conduct end-use testing under ASTM G75 or ISO 15527:2022 to confirm wear life.