Beijing Evergrow Resources supplies UHF-R3200 as an ultra-high-molecular-weight polyethylene (UHMWPE) grade for compression-moulded semifinished stock, ram-extruded profiles, and machined wear components. The grade designation is associated with a nominal viscosity-average molecular mass of 3.2×10⁶ g/mol; the polymer is an unfilled linear homopolymer and is typically handled as a free-flowing powder with an apparent density of 0.45–0.55 g/cm³ when tested according to ISO 60. Moulded stock made from UHF-R3200 exhibits a density of 0.930–0.945 g/cm³ under ISO 1183-1 and falls within the ultra-high-molecular-weight classification of ASTM D4020-18. Because the extensive chain-entanglement network suppresses melt flow, the material is not considered injection-mouldable; it is converted by powder compaction, compression moulding, or ram extrusion. Typical finished components include chain guides for conveyor systems, bottling-line wear strips, star wheels, scraper blades, guide rails, chute liners, and bearing pads in bulk solids handling and food-processing equipment. Table 1 lists representative property values derived from certificates of analysis and supplier technical documentation. These values are not design substitutes for lot-specific data because small variations in molecular mass and bulk density alter consolidation behaviour and abrasion resistance.

What Differentiates UHF-R3200 from Conventional HDPE in Sliding Wear Service?

When UHF-R3200 is substituted for a standard high-density polyethylene homopolymer, the functional difference is not chemical identity but the density of load-bearing entanglement junctions. The nominal molecular mass of 3.2×10⁶ g/mol is 30–60 times greater than that of ordinary HDPE extrusion grades, which generally lie between 50,000 g/mol and 200,000 g/mol. Under dry-sand rubber-wheel abrasion in ASTM G65 Procedure A, unfilled UHMWPE of this class typically loses mass at a rate 5–10 times slower than HDPE; however, published data for this specific product configuration is limited, and design-level wear rates require lot-specific testing. Under low-speed pin-on-disc sliding against 316 stainless steel, the dynamic coefficient of friction for UHMWPE is commonly measured in the range 0.10–0.20, whereas HDPE often increases above 0.30 once the transfer film is removed or the surface temperature exceeds 60°C.

In chain guides and wear strips, the switch from HDPE to UHF-R3200 changes the dominant failure mode from abrasive loss and edge fracture to long-term creep. The notched Izod impact resistance of UHF-R3200 is generally reported as no break under ISO 180/A at 23°C, while unfilled HDPE may yield 10–25 kJ/m². Edge chipping during jam events and low-temperature cracking in cold stores are therefore reduced. The reduced stiffness, however, is a measurable limitation: tensile modulus of UHMWPE is typically 800–1000 MPa under ISO 527-2, whereas high-molecular-weight HDPE can exceed 1200 MPa. A load-bearing component with the same cross-section will deflect more; designers usually increase thickness or use a steel-backed liner instead of assuming direct shape replacement.

Friction performance is also more sensitive to break-in than HDPE. During the first 50–100 h of dry sliding, a transfer film of UHMWPE must build on the metallic counterface to stabilize the coefficient of friction. Abrasion or chemical cleaning of the metal surface destroys this film and temporarily raises friction and wear until the film reforms. This behaviour is observed on bottling-line guide rails and should be included in startup procedures rather than evaluated only from steady-state wear rates.

Ram Extruding and Compression Moulding a 3.2×10⁶ g/mol Polyethylene Grade

For ram extrusion of UHF-R3200 on production machines with die diameters from 50 mm to 120 mm, the powder is compacted in the cold zone and then sintered through the die at 200–240°C. Compaction pressure is normally held between 25 MPa and 40 MPa. A pressure below 20 MPa commonly produces incomplete powder consolidation and visible axial porosity in the extruded rod. Because heat transfer through the compacted powder controls line speed, a 50 mm diameter profile may require 15–40 min residence time in the heated die, depending on die length and wall temperature uniformity. Die temperature excursions above 250°C initiate thermo-oxidative chain scission; the surface becomes yellow to brown, and the notched impact strength falls before the dimensional change becomes apparent.

Compression moulding of thick sections follows a similar thermal path. Pre-compacted powder is heated to 200–220°C under platen pressure of 10–20 MPa, held for 30–60 min per 25 mm of finished thickness, and then cooled under pressure at 2–5°C/min. Faster cooling from 220°C to 80°C reduces crystallinity and hardness, but increases residual stress and post-machining warpage. The cooling stage must therefore be treated as part of the dimensional-control strategy for close-tolerance parts.

Powder feed consistency is the main batch-to-batch variable on ram extruders. Apparent density outside the 0.45–0.55 g/cm³ range shifts the compaction ratio and alters back-pressure. UHMWPE powder absorbs less than 0.03% moisture by mass at 50% relative humidity, so pre-drying is generally not required. However, condensation on cold powder stored in humid warehouses above 80% relative humidity can introduce enough surface moisture to cause steam porosity during sintering. A fluidized-bed dryer at 80°C for 30 min is used before extrusion when storage conditions are uncontrolled.

Screw plastication is not a viable conversion route for UHF-R3200. On a co-rotating twin-screw extruder with an L/D ratio of 40:1, the powder compacts into an unmelted plug and the drive torque can exceed the machine limit before the first kneading block. The same limitation applies to injection moulding: without a fluid melt phase, the material cannot fill a closed mould at pressures available on conventional injection presses. This is why the product is supplied as powder, ram-extruded stock, or machined shapes rather than as pelletized feedstock for high-speed screw plastication.

Compliance under FDA 21 CFR 177.1520 and EU Regulation 10/2011 is documented for unfilled polyethylene homopolymers used in food-contact parts, provided the finished component meets overall migration limits and end-use testing. Supplier statements for UHF-R3200 may reference these regulations when the fabricating plant controls source monomers and additives under the applicable positive list. The grade is outside current RoHS restrictions under 2011/65/EU because it does not require brominated flame retardants or heavy-metal stabilizers, and it can be reported under REACH 1907/2006 as an exempt polymer if the monomer content complies with Article 2(9). For chemical resistance, UHF-R3200 withstands dilute acids, alkalis, and aqueous salt solutions at ambient temperature. Concentrated oxidizing acids such as 98% sulfuric acid and 65% nitric acid embrittle the surface, and aliphatic or aromatic hydrocarbons swell the polymer at elevated temperature. Seal and coupling designs must allow for this dimensional change.

When UHF-R3200 Replaces PA6 or Filled PTFE in Dirty Bearing Environments

In wet or particulate-laden bearing seats, UHF-R3200 replaces polyamide 6 when moisture-induced dimensional growth and acid effluent contact are the controlling failure modes. Polyamide 6 absorbs 2.5–3.0% water at saturation under ISO 62, causing swelling and loss of bolt preload in bearing housings; UHF-R3200 absorbs ≤0.01% after 24 h and remains dimensionally stable in humid bottling lines and washdown areas. Against filled PTFE, UHF-R3200 has higher dry-sand abrasion resistance and lower creep sensitivity under ambient loads, but unfilled or filled PTFE retains a lower initial coefficient of friction and a far higher continuous service temperature of 260°C. The practical limit for unlubricated UHMWPE sliding against steel is often cited as a PV range of 0.2–0.3 MPa·m/s; above this threshold, frictional heating at the wear surface accelerates creep and eventual melting. In dirty environments containing sand, the softer UHMWPE surface can embed particles rather than scoring the metal shaft, which may reduce shaft damage but increases the composite wear rate if the particles are not flushed from the contact zone.

The substitution decision between UHF-R3200 and polyamide 6 depends on temperature and load. At 23°C and continuous compressive stress below 5 MPa, UHMWPE is usually selected for impact resistance and low water uptake. Above 60°C, glass-fibre-reinforced polyamide 6 may retain higher stiffness, but unfilled polyamide 6 loses toughness when dry and may hydrolyse in hot water above 70°C over long service. UHMWPE avoids hydrolysis but begins to creep rapidly near its Vicat softening point of 78–84°C; therefore both materials require support at elevated temperature.

High-Temperature Service Is Limited by Vicat Softening and Oxidative Chain Scission

Continuous service above 85°C is not recommended for load-bearing UHF-R3200 components because the Vicat softening point is 78–84°C under ISO 306/A120 and creep rate rises steeply across a narrow interval. In hoppers and chutes handling hot bulk solids above 80°C, the liner should be continuously supported by a metal backing to prevent sag and extrusion from fastener holes. Strong oxidizing solutions, chlorinated solvents, and prolonged ozone exposure embrittle the surface through free-radical chain degradation. If the application requires continuous exposure to >50% nitric acid or 90% sulfuric acid at temperatures above 40°C, UHF-R3200 is not appropriate. The thermal conductivity of UHMWPE is approximately 0.40–0.50 W/m·K, so frictional heating remains localized at the contact face. Dry sliding designs must therefore limit contact pressure and speed before increasing section thickness, because additional thickness does not remove heat from the interface.