C.I. Pigment Red 31, sold under the Rubber Bordeaux BF designation, has the molecular formula C₂₆H₂₁ClN₄O₇ and CAS registration 6448-96-0. Supplier datasheets report density at 1.3–1.5 g/cm³ and oil absorption at 40–50 g/100 g. In vulcanized NR/SBR footwear unit soles, the pigment is charged at 1.0–2.5 phr to shift the base compound from grey-brown to Bordeaux without introducing heavy-metal shade components. The powder is added with the first filler addition in an internal mixer or on a two-roll mill with a friction ratio of 1.2:1, front roll temperature 50–60 °C; later addition after sulfur will deposit colour streaks and agglomerates on the sole surface. Dispersion is assessed under reflected light on a milled sheet and against ASTM D2663 procedures adapted for pigment agglomerate counting. In high-styrene resin-toughened soling compounds, the addition of 5–10 phr coumarone-indene resin improves pigment wetting and permits the lower end of the dosage interval. At loadings above 2.5 phr, unbound pigment can bloom to the surface after vulcanization, particularly when the compound contains more than 20 phr of low-viscosity naphthenic oil; surface rub fastness is checked with a dry cotton rub. For EU footwear exports, the azocolourant restriction in REACH Annex XVII entry 43 applies to textile and leather portions when tested by EN 14362-1:2017; all-rubber soles are not directly covered by that entry, but many buyer RSL programmes adopt the same 30 mg/kg released aromatic amine threshold as a screening limit. Finished children's footwear must additionally meet the element migration limits of EN 71-3:2019+A1:2021. Vulcanization for sole sheets is carried out in a multiplaten press at 150–160 °C for 6–8 min, followed by conditioning at 23 ± 2 °C and 50 ± 5 % RH for 24 h before physical testing. The terminal articles include vulcanized rubber unit soles, foxing tapes, heel lifts, and direct-moulded canvas shoe toe caps.

When Sulfur Donor Efficiency Drops in Thick-Walled Mouldings

Thick-walled NBR sealing elements cured with low-sulfur donor systems present a narrower processing window because the core temperature can lag the mould surface by 8–15 °C, depending on wall thickness and compound thermal diffusivity. Rubber Bordeaux BF is added at 0.8–1.5 phr in such formulations to provide identification colour without masking filler dispersion flaws. The pigment is predisposed in a DIDP or DOP paste at 1:1 by weight and introduced during the second mixing stage, after the NBR has masticated but before the addition of the cure package. This sequence protects the colorant from prolonged shear heat and prevents shade drift. Compression moulding is performed at 165 ± 3 °C with clamp force appropriate to the projected area; a 150 mm × 150 mm × 6 mm test gasket requires a 200-tonne hydraulic press, while large-diameter flange gaskets require proportionally higher tonnage. Cure time is determined from a moving-die rheometer curve according to ISO 6502:2016; the part is not demoulded until the core reaches a state of cure matching the surface. Undispersed pigment agglomerates act as stress raisers in the sealing lip and reduce compression set resistance. Surface migration and contact staining are evaluated by ASTM D925-14, with white rubber test sheets under load. Where potable water contact is specified, the complete formulation must be certified to NSF/ANSI/CAN 61; the organic colorant is included in the extraction panel, and published data for this specific pigment in cured NBR is limited, requiring formulation-specific extraction testing. The terminal parts include flange gaskets, manway seals, valve seat inserts, and oil-resistant access covers.

Does Neoprene Cable Sheathing Need Surface Bloom Control at 1.5 phr?

Polychloroprene (CR) cable jackets coloured with Rubber Bordeaux BF are formulated with magnesium oxide and zinc oxide as acid acceptors, and the pigment must survive both the alkaline metal oxide environment and the high-shear continuous vulcanization line. A dosage of 1.0–2.0 phr is common for industrial flexible cable sheathing, but surface bloom risk increases when the compound exceeds 2.0 phr or when the plasticizer is a low-molecular-weight chlorinated paraffin. The pigment is added in the internal mixer at the same time as the reinforcing carbon black, using a ram pressure of 0.5–0.6 MPa and a dump temperature not exceeding 110 °C. After forming, the sheath is extruded onto the cable core and cured in a continuous vulcanization tube with saturated steam at 1.2–1.6 MPa or in a dry heat line at 180–200 °C. Colour difference after heat ageing is measured on a spectrophotometer under D65 illumination with 10° observer geometry and reported as CIELAB ΔE according to ASTM D2244-23; a ΔE above 2.0 is generally visible to the eye in side-by-side inspection. Because polychloroprene formulations contain accelerators that can react with certain azo colorants, a pilot extrusion trial is required to check for shade shift and plate-out. The cured jacket must meet the relevant cable standard, such as EN 50525-1:2011, and material restrictions under RoHS 2011/65/EU Annex II when the cable is placed on the EU market. Terminal products include trailing flexible cables, mining cable sheaths, oil-resistant control cables, and heavy-duty industrial power cable jackets.

Continuous EPDM profiles for automotive weatherstripping are produced on vacuum-vented extruders with L/D ratios of 20:1 to 24:1, and the addition of Rubber Bordeaux BF at 0.5–1.2 phr is made in the upstream internal mixer rather than by dry-blend feeding. The compound typically contains 100 phr EPDM with high ethylene content, 80–120 phr carbon black, 40–70 phr paraffinic oil, and a sulfur or sulfur-donor cure system; the pigment must be dispersed before the carbon black reaches full agglomeration because the oil absorption of the pigment is approximately 40–50 g/100 g, and competitive absorption into the black surface produces lighter or duller streaks. Dense and sponge co-extruded profiles are vulcanized in a hot-air tunnel or a microwave-hot-air hybrid line at 230–250 °C for 3–5 min; published data for this specific pigment under those exact conditions is limited, so a thermal stability pre-screen at 230 °C for 5 min is mandatory before production. OEM specifications for automotive interior parts require fogging and VOC limits, commonly evaluated by VDA 278:2011 thermal desorption; low-molecular-weight organic impurities from the pigment can increase fogging and must be below the OEM reporting threshold. Lightfastness of the finished weatherstrip is tested with ISO 105-B02:2014 and compared against a sealed reference; exterior body seals are exposed to 2000 h xenon arc ageing as a durability proxy in some specifications. The terminal articles include door seals, trunk seals, window channel covers, and hood-bumper profiles.

Nitrile Latex Coagulant and Dipping Line Controls for Bordeaux-Toned Films

Nitrile latex compounds for Bordeaux-toned industrial gloves receive Rubber Bordeaux BF as an aqueous pigment dispersion prepared by ball milling with a non-ionic or anionic dispersing agent at a pigment-to-surfactant ratio of 1:0.2–0.4. The dispersion is added at 0.5–2.0 phr dry rubber after the latex has been stabilized with potassium hydroxide to a pH of 9.0–9.5. The coagulant dipping line uses a calcium nitrate coagulant at 10–20 % solids, and the residence time in the compounded latex is 20–40 s to achieve a film thickness of 0.10–0.15 mm. The pigment must remain colloidally stable in the high-pH latex and must not react with the carboxylated nitrile polymer or the sulfur dispersion. Flocculation or pigment settling changes the shade and causes visible pinholes after the film is leached at 40–50 °C for 5–10 min. Vulcanization is carried out in a hot-air tunnel at 110–120 °C for 20–30 min. The extracted latex film is tested for surface rub fastness with a dry cotton crock based on ISO 105-X12:2016, adapted for thin rubber films. For skin-contact compliance, the finished gloves must meet the chemical requirements of the EU PPE Regulation (EU) 2016/425; textile or leather portions of composite gloves are subject to the azo colorant restriction in REACH Annex XVII entry 43, tested by EN 14362-1:2017. All-rubber industrial gloves are not directly covered by that entry, but many buyer RSL programmes impose the same 30 mg/kg released aromatic amine screening threshold. Terminal articles are household and industrial gloves, textured grip palms, and chemical-resistant gauntlets.

Compression-moulded SBR/NR floor tiles and entrance mats use Rubber Bordeaux BF at 1.5–3.0 phr where high pigment loading is required to hide carbon black and recycled rubber granulate. The pigment is introduced in the first pass of an intermeshing mixer with the mineral filler; for a typical compound containing 100 phr SBR, 30–50 phr calcium carbonate, 5–10 phr zinc oxide, and 2–4 phr sulfur, the pigment addition is followed by a 60 s ram sweep and an additional 90 s mix at 40 rpm. Temperature in the mixing chamber is held below 100 °C because higher dump temperatures cause the pigment to soften and form colour streaks in the calendered sheet. After mixing, the compound is calendered at 70–80 °C into sheets of 2–6 mm thickness and vulcanized in a multi-daylight press at 150–160 °C for 8–12 min, depending on sheet thickness. Where CE marking is required, the floor covering must be assessed under EN 14041:2018; physical and colour requirements are specified by the relevant EN floor covering product standard. Pigment-related heavy metal release is checked by EN 71-3:2019+A1:2021 when the mats are marketed for use by children. The cured mat surface is subjected to abrasion testing per ISO 4649:2017; pigment dispersion influences abrasion resistance only through the uniformity of the matrix, and large undispersed particles produce surface defects that reduce the abrasion index. End-use articles include industrial entrance mats, gym flooring tiles, anti-fatigue mats, and stair treads.

Calendered EPDM roofing membranes coloured Bordeaux use Rubber Bordeaux BF as a trace colourant at 0.3–0.8 phr because full-depth earth tones are produced with iron oxide extenders; the organic red pigment shifts the hue without raising compound density. The masterbatch is mixed in a tangential internal mixer at 40–60 rpm and dump temperatures below 110 °C, then sheeted out on a two-roll calender with a roll gap of 1.0–2.5 mm. The uncured membrane is cured by autoclave or continuous roto-cure at 150–170 °C; prolonged exposure at the upper end of this range can cause shade drift, so production lots are retained for physical property and colour checks. Roofing membrane specifications require tensile and weathering tests according to EN 13956:2013; colour change after weathering is evaluated by ISO 4892-2:2013 xenon arc exposure and CIELAB ΔE per ASTM D2244-23. Factory-applied seam tapes and splice compounds contain the same pigment to maintain appearance; surface bloom of the organic pigment is checked by ASTM D925-14. Chemicals used in the membrane are subject to REACH registration, and systems in contact with drinking water require national approval such as KTW/BWGL or equivalent when installed as a potable water liner. Terminal articles are mechanically fastened or ballasted EPDM roofing membranes, pond liners, and reservoir covers.