Beijing Evergrow Resources UHMWPE UHF-F200 is a virgin ultra-high-molecular-weight polyethylene homopolymer supplied as a white free-flowing powder. The grade is specified for compression moulding, ram extrusion, gel processing, and precision-machined wear components that require high abrasion resistance, low coefficient of friction, impact toughness, and dimensional stability in wet or chemically aggressive service. The manufacturer’s model designation UHF-F200 identifies a viscosity-average molecular weight class of 2.0 × 10⁶ g/mol when characterised by solution viscosity methods aligned with ISO 1628-3. Lot-specific certificate-of-analysis values normally include bulk density ≥0.40 g/cm³ by ISO 60, moisture content ≤0.05 % by ISO 15512, and ash content ≤0.05 % by ISO 3451-1. The product is not detectable by standard melt flow rate measurement under ISO 1133-1:2022 at 190 °C/21.6 kg; the absence of a measurable value is an inherent property of this molecular weight class and should not be interpreted as unfavourable melt behaviour.

In consolidated form, the grade typically exhibits density in the range 0.930–0.945 g/cm³ when measured by ISO 1183-1, tensile yield stress in the range 17–22 MPa and elongation at break ≥300 % when tested on ISO 527-2 type 1BA specimens, and Shore D hardness of 60–70 by ISO 868. These values are strongly process-dependent. Compression-moulded plaque produced at the lower end of the consolidation temperature window can retain visible particle boundaries at the fracture surface and develop lower elongation, while the same powder consolidated with an extended hold at 220 °C and controlled pressure will approach the upper elongation range. The relationship between processing history and final mechanical response is more pronounced for UHF-F200 than for lower-viscosity polyethylenes because the high entanglement density restricts particle interdiffusion, making interparticle wetting the critical control variable for lot-to-lot reproducibility.

How Does the Molecular Weight Distribution Influence Gel-Processing Uniformity?

In wet-process microporous membrane and gel-spun fibre manufacturing, UHF-F200 is first swollen in a high-boiling solvent such as paraffin oil, decalin, or mineral oil at solids loadings commonly between 5 wt% and 20 wt%. The swollen gel is then extruded through a slit or spinneret, quenched, stretched, and subjected to solvent extraction. Uniformity of the gel depends on molecular weight distribution, particle size distribution, and the absence of high-density gels that form when local polymer concentration becomes too high before the powder particles are fully disentangled. Because UHMWPE of this viscosity class exhibits intrinsic viscosities commonly reported in the range 2000–3500 mL/g in decalin at 135 °C, the solution processing line must provide sufficient residence time and gentle shear to avoid gel nucleation. A narrow molecular weight distribution reduces the occurrence of 20–50 µm gel specks in cast film; if the distribution is broad, the low-molecular-weight fraction plasticises the gel precursor while the high-molecular-weight fraction remains only partially swollen, producing pinholes during biaxial orientation. Published data for this specific configuration is limited outside the manufacturer’s application laboratory, and direct substitution into a continuous solvent-recovery line should be preceded by pilot-scale gel extrusion using a heated pressure filtration rig or a 25 mm twin-screw kneader equipped for solvent dilution.

For compression moulding, UHF-F200 requires a positive-pressure cooling cycle rather than the unpressurised free cooling used for standard injection-moulding polyethylenes. A production-oriented consolidation sequence typically employs a hydraulic press with platen temperature uniformity better than ±2 °C, heating from 120 °C to 200–220 °C at 3–5 °C/min, a hold pressure of 10–15 MPa for 15–30 min, and controlled cooling to below 60 °C before demoulding. If storage relative humidity exceeds 60 %, the powder should be dried to ≤0.05 % moisture before charging; residual moisture becomes steam during the hold phase and creates internal voids or localised discolouration. Processing above 240 °C accelerates thermo-oxidative chain scission and is not recommended for load-bearing parts because the degraded surface layer reduces impact resistance even when the core remains visually unaffected.

Storage of UHMWPE powder in unsealed bags at ambient relative humidity above 60 % is a common source of moulding defects. The powder should be stored in sealed, moisture-barrier packaging and allowed to reach workshop temperature before opening to prevent condensation. If a lot has been exposed to humid air, drying in a circulating air oven at 60–70 °C for 2–4 h is usually sufficient to reduce moisture below 0.05 %; higher drying temperatures are unnecessary because the powder is not hygroscopic and excessive heat may promote surface oxidation. Drying time must be extended when the powder is stored in bulk bags rather than small sacks because the centre of a large bag remains at the original moisture content long after the outer layer appears dry.

Ram Extrusion and Wear-Component Fabrication Parameters

UHF-F200 can be ram-extruded into round rod, tube, and profiles for food-process wear strips, chain guides, filter plates, and pump wear components. Ram extrusion equipment differs from screw extrusion in that the powder is compacted by a reciprocating ram and sintered through a heated die block with separately controlled heating zones. The powder must be precompressed to a density of at least 0.35 g/cm³ before entering the die; lower preform density produces axial density gradients and internal shrinkage voids. Die temperatures are typically maintained between 160 °C and 200 °C, with dwell time adjusted to the cross-sectional thickness. In production-scale machines with barrel diameters of 40–100 mm, the principal processing bottleneck is not barrel heating capacity but the low thermal conductivity of compacted UHMWPE powder. Raising die temperature beyond the set point does not correct insufficient radial heating; it only degrades the surface layer. For this reason, industrial ram extrusion of the grade is generally restricted to profiles below approximately 100 mm in wall thickness, and published data for thicker monolithic sections is limited.

In lithium-ion battery separator wet processing, UHF-F200 is mixed with paraffin oil, extruded through a slit die, biaxially stretched, solvent-extracted, and heat set. The final film is typically 7–20 µm thick, so hard agglomerates larger than 20 µm are a known cause of pinholes and electrical shorts. Powder destined for this use is screened through a 63 µm or finer sieve and inspected optically so that foreign-particle counts remain below the separator manufacturer’s incoming-material defect class. Batches with a D50 particle size outside the specified window may consolidate successfully in thick compression-moulded sections but can fail film tension and pore-uniformity tests because oversized particles survive the gel stage as visible gels. The separator film also requires a meltdown temperature above 150 °C; UHMWPE of the 2.0 × 10⁶ g/mol class normally meets this requirement, but final shut-down and melt-integrity values must be measured on the exact film line configuration because heat-setting temperature alters pore structure and thermal response simultaneously.

When Downstream Addition of Carbon Black or Glass Fibre Requires Solvent-Assisted Dispersion

The near-zero melt flow of UHF-F200 prevents conventional melt compounding in single-screw or co-rotating twin-screw extruders at standard polyolefin temperatures. Dry blending with carbon black, graphite, or chopped glass fibre before compression moulding or ram extrusion typically results in agglomerated filler clusters because the shear stress available in these low-melt-flow processes is insufficient to break up filler aggregates. Solvent-assisted paste blending with 0.5–2.0 wt% of a low-volatility carrier such as paraffin oil or mineral oil can improve dispersion, but the carrier must be removed or factored into the final void content. Conductive and antistatic compounds based on UHF-F200 are therefore usually prepared by solution gel processing or by incorporating a pre-dispersed conductive masterbatch in naphthenic oil rather than by direct powder mixing. The grade is not designed for direct compounding with amine-based flame retardants or excessive levels of hindered-amine stabilisers; published compatibility data for this specific combination is limited, and incompatibility may appear as migration, colour shift, or stabiliser decomposition at moulding temperatures above 220 °C.

For sliding wear applications, the coefficient of friction of compression-moulded UHF-F200 against polished steel in dry conditions is commonly reported in the range 0.10–0.15, but the measured value is sensitive to counterface roughness, normal load, and sliding speed. Comparative abrasive wear evaluation should use a rotating drum method under ISO 4649 or a sand-slurry test under ISO 15527; both provide numerical volume-loss values that can be used to compare lots and competitor products. UHMWPE in the 2.0 × 10⁶ g/mol class generally shows lower volume loss than 1.0 × 10⁶ g/mol UHMWPE in three-body abrasive wear, and the improvement over HDPE is typically reported at greater than 5:1 in sand-slurry tests. Above approximately 4.0 × 10⁶ g/mol, however, further molecular weight increase often yields only marginal tribological benefit while reducing processability and increasing the likelihood of internal voids; UHF-F200 is positioned below this practical ceiling.

In machined components, UHMWPE of this type exhibits a linear thermal expansion coefficient commonly reported in the range 1.5–2.0 × 10^-4 K^-1, which is high relative to metal. Machining tolerances must account for temperature fluctuations in service; a rise from 20 °C to 60 °C on a 500 mm UHMWPE wear strip can produce linear growth of approximately 3–4 mm. For this reason, slotted mounting holes and floating fasteners are used in long wear liners to allow thermal expansion without buckling. The grade is therefore differentiated from filled engineering polymers that have lower expansion coefficients, but its low coefficient of friction and abrasion resistance continue to justify its selection in wet sliding environments.

The Product Specification Table Is Organised by Test Standard Rather Than Marketing Category

The following table presents a typical acceptance matrix for the powder and for compression-moulded specimens. Values are representative of this viscosity class; the supplier’s certificate of analysis remains the controlling document for any production lot.

Because melt flow rate cannot be used as a lot-to-lot release criterion, processors should adopt solution viscosity, particle size distribution, and bulk density as their incoming quality checks. A production-site incoming inspection plan for UHF-F200 commonly includes a 45 µm or 63 µm sieve retention check, a powder bulk density measurement under ISO 60, and moisture analysis by Karl Fischer titration under ISO 15512. These three measurements detect most powder-related failure modes before moulding: oversize agglomerates that survive ram extrusion, variable mould loading caused by bulk density shifts, and moisture-related voids. The absolute molecular weight of the powder is of secondary importance for incoming inspection if the supplier maintains lot-to-lot solution viscosity control, because the viscosity parameter integrates both molecular weight and molecular weight distribution.

The Grade Occupies a Specific Viscosity Band Between Standard UHMWPE and HDPE

The distinction between UHF-F200 and other polyethylene grades is best understood through viscosity, melt flow, wear, and processing route. The following comparative matrix uses published typical ranges for HDPE sheet grades and a lower-viscosity UHMWPE class; the UHF-F200 column is aligned with the manufacturer’s stated molecular weight class and typical moulded properties.

Regulatory and safety documentation for UHF-F200 is generally issued against the supplier’s REACH registration and applicable Chinese standard for olefin polymers. For U.S. food-contact use, end users commonly verify compliance under 21 CFR 177.1520 for olefin polymers, subject to the food-type and temperature restrictions stated in the regulation. RoHS and REACH declarations should be requested for the specific production lot and should not be inferred from the grade name alone. The product contains no phthalate plasticisers or halogenated flame retardants by formulation; however, confirmation against the lot-specific SDS is required before use in medical device or food-contact components.

In papermaking suction box covers and filtration plates, UHF-F200 is machined from compression-moulded slab or ram-extruded profile. Water absorption is typically ≤0.01 % by ISO 62, preventing swelling in the wet section, while the low dynamic friction reduces forming-fabric drag. The wear edge of a suction box cover is normally machined with a radius because a sharp corner in UHMWPE can act as a stress concentrator and promote localised cracking under cyclic loading. In this application, lot-to-lot consistency of bulk density is more important than absolute average molecular weight alone; bulk density directly controls the weight loaded into the mould and the final slab density. UHF-F200 is differentiated from general-purpose UHMWPE by tighter control of particle size distribution, moisture content, and foreign-particle level, which are the powder properties most likely to create surface defects during compression moulding and ram extrusion.