In solid-state ram extrusion plants running Celanese GUR 4018, the powder is fed into a heated die with a reciprocating ram operating at 20 MPa to 30 MPa compaction pressure. The die barrel is divided into three thermal zones: feed zone 150 °C to 160 °C, sintering zone 180 °C to 200 °C, and water-cooled calibration zone 60 °C to 80 °C. Because melt flow rate measured under ASTM D1238 at 190 °C/21.6 kg remains below 0.1 g/10 min, screw extrusion and injection moulding are not viable conversion routes; the material instead densifies through pressure-assisted interstitial bonding in the solid state. Processing line records from UHMWPE grades with nominal molecular weight above 9 × 10⁶ g/mol show that die wall slip, not bulk viscosity, governs output stability; die pressure fluctuations exceed ±0.4 MPa when the feed hopper bridges due to bulk density below 0.45 g/cm³. A dry premix of 100 parts GUR 4018 and 0.1 wt% to 0.3 wt% calcium stearate internal lubricant is typically metered through a hopper fitted with pneumatic vibrators and a 40 rpm auger. No plasticiser or solvent is permitted because residual volatiles generate voids larger than 500 µm during sintering. Finished chain guide rails, pallet wear strips, and bottle transfer guides are machined from ram-extruded sections with cemented carbide tools at surface speeds above 500 m/min. Abrasion resistance is verified using DIN 53516, with UHMWPE stock reporting mass loss below 10 mm³; tensile yield stress is measured per ISO 527-2:2012 at 50 mm/min and typically falls between 20 MPa and 25 MPa. Food-contact conveyor components comply with FDA 21 CFR 177.1520 and EU 10/2011 overall migration limits of 10 mg/dm², provided the lot is segregated from reprocessed non-food material. Thermo-oxidative degradation begins when die zone temperatures exceed 220 °C, producing yellowing and elongation at break below 50%; furnace-heated dies should therefore be PID-controlled with recovery time below 3 s.

What Occurs When GUR 4018 Powder Is Sintered Below 200 °C?

Below 200 °C, GUR 4018 powder particles retain discrete boundaries and form only partial inter-particle necks; this is intentional in binderless porous sintering. The powder is screened to a 63 µm to 160 µm fraction, filled into tool steel moulds, and compacted at 3 MPa to 6 MPa cold pressure before the mould enters a circulating-air oven at 180 °C to 195 °C for 15 min to 30 min depending on wall thickness. Pore size is controlled primarily by particle size distribution and compaction density, not by volatile additives; no binder or pore former is required, which avoids chlorinated residue concerns under REACH EC 1907/2006. Aeration diffuser discs for industrial wastewater basins are produced from 6 mm to 12 mm plates with interconnected porosity between 35% and 45%; bubble point pore diameter is tested according to ASTM F316-03, with typical values between 20 µm and 70 µm. Air permeability is measured using ISO 5636-5:2013 and usually falls between 200 L/m²·s and 600 L/m²·s at 100 Pa. Process boundary: exceeding 200 °C for more than 5 min collapses surface pores and forms a dense, glossy skin that reduces oxygen transfer efficiency by more than 30%. Sintered porous tubes used in acidic leaching circuits are qualified by immersion in 5 vol% hydrochloric acid at 60 °C for 72 h, with weight change below 0.05%. Published data for GUR 4018-specific sintering of pore size below 10 µm is limited; such geometries tend to require lower molecular weight UHMWPE or hot isostatic pressing to fill interstitial voids.

Compression moulding of solid GUR 4018 liners for hoppers, silos, and chute systems begins with filling a positive mould to 2% to 5% overfill ratio. Hydraulic press platens are heated to 180 °C and kept under 10 MPa to 30 MPa cavity pressure for 10 min per 10 mm of cross-section. Cooling must be conducted under the same pressure at 20 K/h to 40 K/h until core temperature reaches 40 °C; uncontrolled depressurisation before core solidification produces internal voids and warpage exceeding 2 mm/m. Final sheets are cut with diamond-tipped circular saw blades at 3 000 rpm; CO₂ laser cutting is not recommended because thermal stress at the kerf initiates micro-cracks along sintered powder boundaries. Bulk solids handling liners made from GUR 4018 are evaluated for sliding abrasion against sand and gravel using DIN 53516, reporting mass loss below 15 mm³; Charpy impact at -40 °C is tested per ISO 179-1:2010 method 1eU and generally exceeds 80 kJ/m² without break. Density measured via ISO 1183-1:2019 should remain between 0.925 g/cm³ and 0.945 g/cm³ to confirm full compaction. For grain handling and food-contact transfer chutes, compliance with FDA 21 CFR 177.1520 is required, and EU 10/2011 overall migration limits of 10 mg/dm² apply. Process incompatibility: the mould release agent must be silicone-free if the liner will be electrostatically adhered to steel; residual silicone concentration above 0.05 mg/m² reduces lap shear adhesion to epoxy structural adhesives below 1 MPa.

When GUR 4018 Replaces HDPE in a Wet-Process Microporous Membrane Line

In wet-process microporous membrane lines, the first processing conflict appears when GUR 4018 is compounded with liquid paraffin at 70 wt% to 80 wt% plasticiser loading against 20 wt% to 30 wt% polymer. A co-rotating twin-screw extruder with L/D ratio of 48:1 to 60:1 is required, operating at screw speeds of 150 rpm to 250 rpm and barrel settings from 170 °C to 220 °C. Because the zero-shear viscosity of UHMWPE in paraffin solution is substantially higher than that of HDPE at 180 °C, melt pressure at the gear pump can exceed 12 MPa when the polymer fraction is above 25 wt%. The gel film is cast at 800 µm to 1 200 µm thickness and rapidly quenched to 10 °C to fix phase separation. Sequential biaxial stretching at 90 °C to 120 °C with machine-direction ratio 4× to 6× and transverse-direction ratio 4× to 6× induces lamellar separation; paraffin is extracted with n-hexane or methylene chloride in a closed-loop system. Final separator thickness between 12 µm and 25 µm is measured under ISO 534:2011; tensile strength is tested per ASTM D882-18, with acceptable values for UHMWPE separators typically above 50 MPa in the machine direction. Air permeability is assessed by Gurley number under ISO 5636-5:2013, with values between 200 s/100 mL and 500 s/100 mL. Shutdown function is verified by differential scanning calorimetry at 135 °C onset melting. Operational boundary: residual paraffin above 0.05 wt% after extraction reduces electrolyte wettability and creates a barrier to lithium-ion transport; final washing lines therefore use 80 °C heptane rinses for 20 min. Published data for GUR 4018-specific separator formulations is limited compared to dedicated UHMWPE separator grades; plant trials on blends with HDPE indicate that GUR 4018 addition above 15 wt% of total polymer raises gelation uniformity issues in thin films below 15 µm.

Blending GUR 4018 into HDPE pipe grade PE100 at 5 wt% to 15 wt% produces a discontinuous UHMWPE domain structure that modifies slow crack growth resistance but imposes a narrow processing window on counter-rotating twin-screw extruders. The powder is dry-blended with HDPE pellets and stabiliser masterbatch containing 2.5 wt% carbon black; the mixture is fed through a grooved-barrel extruder with L/D ratio 30:1, barrel temperatures 180 °C to 210 °C, and water-cooled feed zone maintained at 40 °C to 50 °C. At 10 wt% GUR 4018 addition, die entrance pressure rises 20% to 35% compared to neat HDPE due to high melt elasticity and long relaxation time; this pressure rise is measured at shear rates below 50 s⁻¹ using capillary rheometry according to ISO 11443:2021. Product applications include extruded spiral-wound drainage pipes and fuel tank multilayer inner layers, where slow crack growth resistance is assessed using the Pennsylvania notch test ASTM F1473-20 at 80 °C and 2.4 MPa, with failure times extended beyond 1 000 h. Full pipe hydrostatic strength is tested per ISO 9080:2022 and EN 12201-2:2011; welded pipe networks require ISO 13479:2009 notched pipe test. Processing limitation: additions above 15 wt% induce unstable melt fracture on single-screw lines and should be discharged through a screen pack no finer than 40 mesh to avoid gel-like particle blockage. Do not combine GUR 4018 with peroxide-initiated silane crosslinking in PEX-a processes; residual free radicals preferentially attack the UHMWPE chain ends and generate micro-gels that appear as surface roughness above 0.5 mm.

Filter press plates and acidic electrolyte diaphragms

Filter press plate production from GUR 4018 uses high-tonnage compression moulding because the part thickness of 40 mm to 80 mm requires long thermal soak times and slow crystallisation. The mould cavity is filled with 100 wt% GUR 4018 powder and 0.2 wt% carbon black UV stabiliser; no glass fibre or mineral filler is used because hard inclusions reduce tensile elongation at break below 200% and initiate premature cracking along the recessed chamber edges. Hydraulic clamp force is set to deliver 10 MPa to 20 MPa on the projected area, with platen temperature 180 °C to 200 °C and hold time based on 8 min/mm average wall thickness. Cooling under pressure at 15 K/h to 20 K/h prevents warpage; plates larger than 1 000 mm diagonal are measured for flatness with a dial gauge and rejected if deviation exceeds 0.5 mm/m. Final filter press chamber components are tested for compressive yield strength per ISO 604:2002, with UHMWPE values reported between 18 MPa and 25 MPa; Shore D hardness per ASTM D2240-15 is between 62 and 66. Chemical resistance in acidic electrolyte service is determined by immersion in 20 wt% sulfuric acid at 80 °C for 14 days, with tensile retention above 90% and mass change below 0.1%. Compliance for mining dewatering plates falls under REACH EC 1907/2006 and RoHS Directive 2011/65/EU; no phthalate plasticiser or heavy-metal stabiliser is present.

Test standard	Property	Acceptance criterion
ISO 604:2002	Compressive yield strength	18 MPa to 25 MPa
ASTM D2240-15	Shore D hardness	62 to 66
ASTM D638-14	Tensile yield stress	20 MPa to 25 MPa
DIN 53516	Abrasion mass loss	below 10 mm³
ASTM D570-22	Water absorption 24 h	below 0.01%
REACH EC 1907/2006	SVHC screening	no detectable

Sintered porous vacuum chucks and wafer-handling fixtures made from GUR 4018 are converted by filling precision aluminium moulds with powder that has been air-classified to 63 µm to 125 µm. The powder is compacted at 4 MPa and sintered in a nitrogen oven at 180 °C to 190 °C with a 2 °C uniformity across the platen, then surface-ground with diamond abrasives to a flatness of 10 µm over 200 mm. Vacuum chucks used for glass edging require through-plane permeability between 5 × 10⁻¹⁴ m² and 2 × 10⁻¹³ m²; air permeability is measured using ISO 5636-5:2013. Pore throat diameter is characterised by mercury intrusion porosimetry according to ASTM D4404-18, with median values from 15 µm to 40 µm. Final components include particle-trapping porous mandrels for pharmaceutical tablet handling and vacuum fixtures for ceramic green machining; these must pass outgassing screening in a vacuum chamber at 10⁻³ Pa and 80 °C for 8 h, with mass loss below 0.01%. Process limitation: UHMWPE porous surfaces are not suitable for ISO 14644-1 Class 1 cleanrooms unless sealed or externally purged because the sintered network sheds particulates larger than 0.1 µm during flexure. When used in semiconductor vacuum chucks, metal inserts must be press-fitting only; adhesive bonding with cyanoacrylate causes stress cracking at insert interfaces after thermal cycling between 20 °C and 80 °C exceeding 50 cycles.