In continuous ram extrusion lines processing Celanese GUR UHMWPE 4170, the governing process constraint is not a classical melting point but a transition from compacted powder to a viscous, entangled plug that retains melt memory and resists flow under ordinary screw-extrusion shear. Single-screw extruders are therefore replaced by a reciprocating ram system, in which a hydraulically driven piston compresses the powder inside a heated barrel before pushing it through a shaping die. Barrel set points are typically held between 200°C and 240°C, while the die body is controlled 10°C to 30°C lower to stabilize the extrudate skin and reduce die swelling. Internal melt-temperature excursions above 250°C lead to thermo-oxidative chain scission, detected on production floor checks as a measurable drop in the ISO 1628-3 viscosity number of surface material relative to the core. Powder bulk density variation creates feed-bridging over the hopper throat, particularly when ambient relative humidity exceeds 60%; hopper vibrators, desiccant dryers, and 0.5 mm to 1.0 mm sieved fractions are used to stabilize metering. Die design for profiles must avoid abrupt cross-section changes because the material enters the die as a compacted plug and any localized shear plane can develop into internal voids or transverse surface cracks. Finished solid profiles are tested under ASTM D4020 and ISO 11542-2 for density, tensile yield, elongation, and impact resistance. Typical downstream products include conveyor guide rails, chain wear strips, scraper blades, marine fender facings, and sliding pads for industrial machinery, where the key advantage is resistance to gouging abrasion without the need for lubricant-filled cavities.

A wet-process lithium-ion battery separator line using GUR 4170 does not process the resin as a solid profile. The powder is first dispersed in a paraffinic plasticizer at a weight ratio commonly between 15:85 and 30:70 resin-to-oil; this diluent lowers chain entanglement density sufficiently for sheet formation. The mixture is heated inside a co-rotating twin-screw extruder with barrel temperatures from 180°C to 220°C, then cast into a gel sheet. After cooling, the plasticizer is extracted with methylene chloride or n-hexane in a countercurrent vapour-extraction bath. The microporous sheet is then biaxially stretched at machine-direction and transverse-direction draw ratios of 5×5 to 7×7, a step that develops slit-like micropores and increases mechanical strength through orientation. Heat-setting at 110°C to 130°C stabilizes shrinkage and controls residual stress. The separator must pass air-permeability checks by TAPPI T460 for Gurley seconds and thickness measurement by ISO 4593; both tests are sensitive to extraction uniformity. Residual oil above 0.5 wt% depresses electrolyte wetting and raises the MacMullin number, while excessive draw ratios cause local fibrillation and a drop in transverse tensile strength. Published data for GUR 4170 in this specific configuration is limited to supplier technical guidance, but the processing window overlaps with known wet-process membrane and gel-spinning practices for ultra-high-molecular-weight polyethylene.

Compression Moulding Sheet Stock: What Determines Flatness Above 20 mm?

Compression moulding of GUR 4170 sheet follows a sintering-like cycle rather than a conventional melt-filling cycle because the resin retains high extensional viscosity even above its crystalline melting range. Powder is charged into a stainless steel mould cavity, closed under low pressure, and heated by platens maintained between 190°C and 210°C. Moulding pressure is normally restricted to 5 MPa to 10 MPa; pressures above this range can raise the moulded density beyond 0.945 g/cm³ and produce a measurable reduction in notched impact toughness. The mould is held at peak temperature for approximately 10 min to 15 min per 25 mm of thickness, then cooled at 10°C/h to 15°C/h under maintained load. Demoulding above 60°C commonly produces warpage and edge curl in slabs thicker than 20 mm, especially when the part has asymmetric wall sections. Finished sheet is tested under ISO 11542-2 and ASTM D4020; typical Shore D hardness falls between 62 and 68 when measured by ISO 868. Food-contact grades require compliance with FDA 21 CFR 177.1520 and EU Regulation 10/2011; migration testing is conducted under the specified food simulants and time-temperature conditions. The coefficient of linear thermal expansion is approximately 1.5 × 10⁻⁴ K⁻¹ to 2.0 × 10⁻⁴ K⁻¹, so fabricated sheet must be mounted with slotted holes or loose fasteners to accommodate thermal movement. Thick sheet is subsequently planed, saw-cut, or extrusion-welded into wear plates, guide rails, hopper liners, and sorting-table surfaces.

Sintered Porous Media, Pore Size Hysteresis, and Backflushing Limits

GUR 4170 powder can be sintered without complete densification into porous tubes, discs, and flat plates for filtration and air-diffusion duties. The powder is loaded into a mould and heated at 180°C to 210°C under low contact pressure, typically below 5 MPa, for 20 min to 40 min. Particle boundaries coalesce and form sintering necks, while interstitial voids remain interconnected. Mean pore diameter is controlled by powder sieve fractions, with common cuts of 100 µm, 250 µm, and 500 µm producing filter grades from approximately 5 µm to 100 µm. Pore structure is characterized by bubble-point and mean-flow pore-diameter testing under ASTM F316; hysteresis between wet and dry curves is used as an indirect measure of pore-throat irregularity. Porosity for sintered UHMWPE media normally falls in the 30% to 50% range. Continuous service above 80°C is not recommended because the material creeps under load and may lose sintered-neck integrity. Strong oxidizing acids and prolonged exposure to ultraviolet light also degrade the porous structure. These porous components are used in chemical filtration, pneumatic venting, fluidized-bed distribution plates, and water-treatment diffusers where a low-extractable, chemically resistant matrix is required. Backflushing pressure must be kept below the bubble-point collapse threshold of the pore network; otherwise the porous body can compact irreversibly and lose permeability.

When a Bulk Solids Liner Must Reduce Arching Without Introducing Cold Flow

Silo and hopper liners fabricated from GUR 4170 sheet lower wall friction and reduce the likelihood of cohesive arching, provided the liner is not loaded beyond the creep limit of the material. Wall friction angles measured with a Jenike shear tester under ASTM D6128 can fall between 10° and 20° against polished carbon steel, and dynamic coefficient of friction under ASTM D1894 is typically in the 0.10 to 0.20 range. For mass-flow hopper design, the liner must maintain this wall friction angle over the full range of anticipated consolidation stresses. Sustained bearing stress above 10 MPa should be avoided because compressive creep testing under ASTM D2990 shows time-dependent deformation that can exceed 2% within 1,000 h; this cold flow loosens mechanical fasteners and can create steps at liner joints. Sheets are normally installed in thicknesses from 8 mm to 20 mm, with slotted holes or welded studs to accommodate the high thermal expansion coefficient of UHMWPE. End products include chute liners, hopper liners, screw-conveyor trough liners, and impact plates in mining and mineral handling. For food and pharmaceutical solids handling, the liner must satisfy the same FDA 21 CFR 177.1520 and EU 10/2011 requirements used for sheet stock. The design boundary is set by the combination of low surface energy and high creep compliance: friction reduction is repeatable only when the liner remains below its long-term compressive strain threshold.

A downstream compounding line that feeds GUR 4170 into a polyolefin matrix faces a viscosity mismatch between the molten matrix and the high-entanglement UHMWPE domains. The powder is typically added at 2 wt% to 10 wt% into polypropylene or high-density polyethylene to improve abrasion resistance, but it must be introduced through a side feeder after the matrix is molten rather than through the main feed throat. A co-rotating twin-screw extruder with L/D 44 is commonly used, with barrel set points matched to the matrix polymer; the UHMWPE particles soften but do not fully homogenize at those temperatures. Screw speed and downstream pressure are adjusted until dispersed UHMWPE domains remain below 10 µm, because larger domains become crack-initiation sites. Abrasion resistance of the compound is assessed by ASTM D4060 Taber wear testing, while impact resistance is measured by ISO 179-1 or ASTM D6110. Published data for GUR 4170 in this compounding configuration is limited, so the dispersed-domain size distribution must be verified by scanning electron microscopy of microtomed sections on a batch-to-batch basis. End products include injection-moulded tote bins, conveyor rollers, and protective housings where a moderate increase in surface hardness is less important than resistance to sliding wear and gouging.