Mitsubishi Chemical Advanced Materials markets TIVAR ESD as a static dissipative formulation of ultra-high-molecular-weight polyethylene supplied in compression-moulded or ram-extruded semi-finished stock shapes. The grade is specified in semiconductor wafer handling, cleanroom fixtures, conveyor-wear strips, and diagnostic assembly cells where uncontrolled triboelectric charge on unfilled UHMW-PE creates discharge risk. Because the base polymer has a weight-average molecular weight above 3×10⁶ g/mol, the material cannot be processed by conventional injection moulding; sheet and rod are produced under high-pressure compression moulding or ram extrusion. The resulting stock shape retains the general chemical resistance and slip behaviour of UHMW-PE while adding surface resistivity in the static dissipative range. Surface resistivity is measured according to ASTM D257-14 at 500 V DC on conditioned specimens at 23 °C and 50 % RH; representative manufacturer data place the grade between 10⁶ Ω and 10⁹ Ω. These values distinguish TIVAR ESD from unfilled TIVAR 1000, which is generally reported above 10¹² Ω, and from conductive loaded polyethylene grades that can fall below 10⁴ Ω.

The exact additive package is proprietary, but the grade is a black UHMW-PE compound in which a dispersed conductive phase establishes bulk and surface conductivity. The filler loading is above the percolation threshold but below the level that produces metallic-level conductivity. This distinguishes TIVAR ESD from conductive UHMW-PE grades with surface resistivity below 10⁴ Ω, which are sometimes used for electromagnetic shielding or high-speed charge removal but can be less suitable for sensitive-device work surfaces.

The electrical modification carries design implications that are not captured by surface resistivity alone. The dissipative filler network is sensitive to orientation, skin effects, and machining. On a compression-moulded sheet, surface measurements made on the original mould skin may differ from readings taken after 1–2 mm of machining; lot-specific data should be requested when a component is used as a grounded work surface. The material is normally black, and the filler system reduces the transparency and food-contact presumptions that apply to unfilled UHMW-PE grades. TIVAR ESD should not be specified for direct food-contact use under FDA 21 CFR 177.1520 unless a written lot-specific compliance statement is available, because filled grades can fall outside the olefin polymer assumptions used for unfilled resins.

When surface resistivity is controlled between 10⁶ and 10⁹ Ω instead of bulk insulation

Unfilled UHMW-PE is a hydrocarbon electrical insulator. Surface resistivity values above 10¹² Ω allow charge generated by sliding contact to persist for minutes or hours. In automated handling systems, that retained charge can cause jamming, particle attraction, and discharge events. TIVAR ESD shifts the material into the static dissipative classification by forming a dispersed filler network at or above the percolation threshold. The typical surface resistivity range of 10⁶–10⁹ Ω is insufficient to create a rapid conductive discharge path but sufficient to bleed charge when a component is grounded through its mounting hardware. This is the principal difference from conductive carbon-filled grades where surface resistivity below 10⁴ Ω may produce discharge currents that are too fast for sensitive devices if the part is used as a work surface or handling fixture.

Field measurements on installed fixtures should follow IEC 61340-5-1:2016 or ANSI/ESD S20.20-2021 rather than raw material data alone. A machined TIVAR ESD plate may read differently at the surface, at a drilled hole, and at the mounting bolt. Because the standard test uses flat electrodes, curved or thin-wall parts can produce misleading results. For finished worksurfaces, resistance-to-ground testing is commonly performed according to ANSI/ESD STM4.1 or IEC 61340-2-3; material certificate data from ASTM D257 is not a substitute for installed-system verification. Measuring the same fixture after solvent wiping can produce temporarily lower or higher values depending on residue. Components should be conditioned until equilibrium under the relevant test atmosphere before acceptance testing; readings taken immediately after wiping with isopropanol or deionized water are frequently unstable.

Comparative stock-shape property matrix and filler trade-offs

The table below presents representative manufacturer datasheet values for grade comparison. They are not lot-certificate limits, and electrical values in particular can vary with sheet thickness, machining depth, and ambient humidity.

The tabulated values show that the ESD filler does not produce a large density shift, but it changes electrical behaviour and visual appearance. The reduction in surface insulation is accompanied by a possible change in weld seam consistency: hot-gas welding of TIVAR ESD can produce weld zones with higher surface resistivity than the parent sheet because the filler network is disrupted by remelting and flow. Published data for weld-seam resistivity in this specific grade is limited; if a welded fixture must remain dissipative, resistance-to-ground should be verified after welding and not assumed from sheet properties.

The primary difference between TIVAR ESD and unfilled TIVAR 1000 is electrical: TIVAR 1000 is insulating, TIVAR ESD is dissipative. The secondary differences are mechanical and aesthetic. The dissipative filler usually produces a black color and a slightly lower Shore D hardness. Under sliding wear, UHMW-PE is valued for its low coefficient of friction and high abrasion resistance, but filler addition can change wear mechanisms from adhesive transfer to abrasive ploughing at the microscopic scale. Published comparative wear data for TIVAR ESD versus unfilled TIVAR 1000 under ASTM G133 or ISO 7148-2 are limited; therefore a direct percentage loss should not be assumed. In continuous sliding against a metal counterface, wear-in of the filled surface may produce a black transfer film that can affect friction and surface resistivity differently from the parent sheet.

Machining behaviour differs measurably from filled acetal or PEEK. TIVAR ESD is softer and more thermally expansive than rigid thermoplastics. Shops machining TIVAR ESD typically use polished carbide or high-speed steel tools with high rake angles and sharp edges to avoid smearing. Because UHMW-PE does not have a true melting point in the same sense as lower-molecular-weight HDPE, it is machined without flood coolant in many operations; if coolant is used, water-soluble emulsions are generally acceptable. The material is not hygroscopic, and moisture absorption under ISO 62:2008 is generally below 0.01 %; predrying is not required for dimensional reasons. However, stock shapes stored below 10 °C may accumulate surface condensation, and that water film must be removed before surface resistivity verification to avoid false low-resistance readings.

On production-scale machining centers, TIVAR ESD is processed with tooling conditions that differ from filled acetal or PEEK. The material is soft enough to deflect under high clamping pressure. Vacuum fixturing with a porous plate or low-pressure mechanical clamps avoids localized deformation. Feed rates are limited by heat generation rather than tool wear. Because UHMW-PE has a thermal conductivity below 0.5 W/m·K, cutting heat is not dissipated through the chip. Deep cuts with high feed can raise the cut surface above the crystalline melting region and produce a smear or raised burr. A common starting point is 500–1000 m/min surface speed for carbide tools with 0.05–0.25 mm/rev feed, but optimization must be performed on the specific machine because published data for this specific configuration is limited. Flood coolant is not required, but if used, it must be non-aromatic and should be removed before electrical testing.

What cleanroom and semiconductor handling specifications require beyond material resistivity

Raw material surface resistivity does not guarantee that a finished component will meet an ESD protected area requirement. Standards such as IEC 61340-5-1:2016 and ANSI/ESD S20.20-2021 evaluate the installed component, including grounding path, contact pressure, surface contamination, and ambient humidity. TIVAR ESD is often selected for wafer combs, end effectors, guide rails, and cassette components because it combines static dissipation with low particle generation and resistance to aggressive cleaning chemistries. The material resists dilute acids, alkalis, and many polar solvents; it is not recommended for strong oxidizing acids or for continuous exposure to aromatic and chlorinated solvents at elevated temperature. The use of machined surfaces in cleanrooms should be qualified for particle shedding under ISO 14644-1:2015 class limits; material suppliers do not provide particle-count guarantees for machined surfaces because surface finish is controlled by the fabricator.

The static dissipative mechanism is not a surface coating. Surface-treating or abrasive cleaning does not remove a conductive layer. That is an advantage over coated ESD films or painted static-dissipative surfaces. However, because the filler is dispersed through the bulk, localized high-shear operations can orient the polymer matrix and change the electrical path. Fine abrasive finishes above Ra 0.4 μm may create a visible matte surface but do not typically remove the dissipative mechanism; the effect on resistivity is secondary to increased surface area and moisture adsorption. If a component is repeatedly exposed to isopropanol or other low-residue solvents, resistivity should be re-qualified after the cleaning interval, not only at incoming inspection.

Cleaning protocols in controlled environments can deposit ionic residues that reduce surface resistivity to temporarily lower values. The reverse is also possible: silicone oil or high-vacuum grease can insulate the surface and cause readings above 10⁹ Ω. TIVAR ESD components should be cleaned with a solvent that leaves no conductive or insulating residue, then conditioned until equilibrium at 23 °C and 50 % RH before acceptance testing. This measurement discipline follows the conditioning requirements described in ASTM D257-14 and is often omitted in incoming inspection.

Stress relief cycles prevent post-machining bow, but thermal expansion still governs clearances

Compression-moulded UHMW-PE stock contains residual stress. TIVAR ESD components machined asymmetrically can bow or change dimension after the first thermal cycle. Fabricators therefore rough machine, stress relieve, and finish machine. A common stress-relief cycle for UHMW-PE stock is 80–100 °C for 1 hour per 25 mm of thickness in an air oven, followed by slow cooling. This is not a grade-specific cure step; it is a dimensional stabilization procedure inherited from unfilled UHMW-PE practice. The high coefficient of linear thermal expansion, approximately 1.5×10^-4 K^-1 per ISO 11359-2:2021, means a 1000 mm rail increases by approximately 1.5 mm for each 10 °C rise. Machined clearances must allow for this displacement or the part may buckle against rigid metal supports.

Adhesive joining of UHMW-PE is generally difficult because of the low surface energy of polyethylene. TIVAR ESD is no exception. Standard adhesives do not wet the surface without plasma, corona, or flame treatment. However, these treatments modify surface chemistry and can temporarily alter measured surface resistivity. Mechanical fastening with slotted holes and shoulder washers is preferred for grounded static-dissipative fixtures, and resistance-to-ground should be measured through the final mounting stack. Welding by hot-gas or butt fusion is possible, but the filler network in TIVAR ESD may not rebuild across the weld interface in the same manner as the parent compression-moulded sheet; the weld zone can contain voids or filler-depleted regions that raise localized resistivity. Published data for this specific weld configuration is limited, so welded joints in static-dissipative UHMW-PE are best qualified by testing the finished assembly rather than by raw material properties.

For chemical processing applications, TIVAR ESD is generally resistant to 10 % sulfuric acid, 10 % sodium hydroxide, and many inorganic salt solutions at ambient temperature. This statement is derived from the general behaviour of UHMW-PE under ISO 175:2010, not from an exhaustive compatibility matrix for the filled grade. Strong oxidizing media such as concentrated nitric acid, fuming sulfuric acid, and chromium trioxide solutions attack polyethylene and should be avoided. Halogenated solvents and aromatic hydrocarbons cause swelling or softening at elevated temperature; the degree depends on exposure time, stress level, and filler loading. If the environment includes mixed cleaning agents, a coupon immersion test is preferable to a literature-based selection.

Compared with static dissipative acetal, PEEK, or PVC, TIVAR ESD has lower modulus and lower maximum service temperature, but higher impact resistance and lower moving friction against many metal surfaces. The trade-off is not universally favourable. If a fixture operates above the maximum continuous service temperature of UHMW-PE, a higher-temperature ESD resin such as static dissipative PEEK should be specified. If dimensional stiffness is dominant, a filled ESD acetal may be more suitable. TIVAR ESD should be selected when the application requires UHMW-PE-level abrasion resistance, chemical compatibility, and energy absorption, combined with dissipative electrical behaviour. The exact service boundary should be derived from the grade-specific continuous-service-temperature statement in the manufacturer’s documentation rather than from unfilled UHMW-PE literature.

Regulatory documentation for TIVAR ESD is lot-dependent. Under REACH Regulation (EC) No 1907/2006, a finished stock shape containing a carbon-based dissipative filler may require a candidate-list declaration only if an SVHC is intentionally added; this is not inherent to the grade. Under RoHS 2011/65/EU, UHMW-PE filled with carbon black normally does not contain the restricted heavy metals or brominated flame retardants above the maximum concentration values, but compliance must be confirmed against the specific lot because raw materials and masterbatch sources vary. The grade is not marketed as implantable or long-term repeated skin-contact material under ISO 10993, and no claim should be inferred from unfilled UHMW-PE biological test data. For any application requiring a grounded static-dissipative surface, the component specification should include resistance-to-ground limits, test voltage, conditioning time, and cleaning method. Without those parameters, surface resistivity alone is an insufficient quality gate.