Burgundy TRR is a synthetic micronized iron oxide pigment classified under Colour Index Pigment Red 101 with a hematite α-Fe₂O₃ crystal structure. The grade is manufactured by controlled calcination of iron sulfate precursor followed by wet milling and air classification. The deep burgundy mass tone is produced by a median primary particle size of 0.35–0.65 µm and a narrow particle-size distribution. Bulk density is 1.0–1.3 kg/L, specific gravity is 4.9–5.2, and pH is 5.0–8.0 per DIN EN ISO 787-9. In a standard long-oil alkyd binder, colour coordinates under D65/10° are approximately L* 38–41, a* 24–28, and b* 9–13. The product is used where high alkali resistance, heat stability to 800°C, and low water-soluble salt content are required. The designation TRR denotes the manufacturer’s toll-refined red sequence; it is not a solvent dye or organic red formulation. Tint strength is controlled at 98–102% against the manufacturer master standard. The product is supplied in 25 kg multiwall paper bags with a shelf life of 24 months when stored below 40°C and below 60% relative humidity.

What Distinguishes Burgundy TRR From Bright Red and Brown Iron Oxide Grades?

Bright red iron oxide grades typically exhibit a* values above 30 and mass tones closer to orange-red, whereas brown grades show b* values above 18 and reduced chroma. Burgundy TRR occupies intermediate colour space at a* 24–28 and b* 9–13, producing a blue-shifted red without carbon black adjustment. The oil absorption of 18–24 g/100 g per DIN EN ISO 787-5 is lower than many precipitated red pigments, which may reach 40–60 g/100 g. This permits higher pigment loading without exceeding target high-shear viscosity in solventborne coatings. In concrete, the water-soluble salt content below 0.5% per ASTM C979-16 reduces efflorescence potential relative to grades containing sodium sulfate residues above 1.0%. Solventborne mill-base preparation in a long-oil alkyd at 35% pigment by weight with a Cowles high-speed disperser at 18–25 m/s tip speed yields a Hegman gauge reading of 7+ after 20 min. The oil absorption of 18–24 g/100 g is low enough to permit direct dispersive grinding without bead milling for primers, while tinting strength is retained. In systems requiring full gloss, a horizontal bead mill charged with 2.5 mm zirconia beads at 85% bead fill reduces agglomerates below 10 µm within 15 min residence time. This behaviour differs from high-oil-absorption organic reds that frequently demand triple-roll milling or extended bead-mill passes.

Dry-cast concrete paver production provides a demanding dispersion environment for pigments. On a planetary counter-current mixer with 750 kg batch weight and a water-to-cement ratio of 0.35, Burgundy TRR is added at 2.5–4.0% by cement mass. Addition after coarse aggregate and cement but before water reduced dry pigment loss from 0.8% to 0.2% in a monitored production campaign across 12 consecutive batches. Colour variability measured as CIELAB ΔE against a reference paver remained below 1.5. The product’s 45 µm sieve residue below 0.02% per DIN EN ISO 787-7 prevents visible specking at production throughputs up to 12 cycles/h. Alkali resistance in cured portland cement is reported as no significant colour shift after 28-day water immersion per ASTM C979-16 pigmentability testing. The inorganic pigment does not contribute to pH-dependent colour drift in the cementitious matrix, and the low salt content limits surface efflorescence in exterior paving applications.

Rigid PVC Capstock Extrusion Processing Limits

Rigid PVC capstock extrusion with Burgundy TRR is performed on a counter-rotating twin-screw extruder with 36:1 L/D and a barrel temperature profile from 130–160°C. The pigment is added at 0.8–2.0 phr; at the upper limit, colour saturation reaches practical opacity without a measurable change in fusion time. During 8 h continuous runs, die-lip plate-out mass was below 0.10 g per run. The calcium-free surface treatment avoids secondary zinc interaction with stabilizer packages. Residual moisture after 24 h at 105°C remains below 0.5%, eliminating pre-drying in central conveying systems below 60% RH. For dark burgundy capstock, the product replaces carbon black additions of 0.1–0.4 phr, reducing variability arising from carbon black dispersion. The pigment does not alter PVC heat stabilizer consumption, and no plate-out-related press instability was recorded when the stabilizer package was maintained at 4.0–5.0 phr tin mercaptide. The grade differs from carbon black and organic reds by maintaining colour consistency at elevated processing temperatures without generating conductive or static charge build-up in the extruder.

Powder coating operations based on hybrid polyester-epoxy binders utilize Burgundy TRR as a pre-dispersed binder concentrate at 40 wt% pigment loading, let down to 8–12 wt% in the final formulation. The concentrate is compounded on a twin-screw extruder with 37 mm screw diameter and 900 rpm screw speed, maintaining melt temperature at 100–110°C to avoid pre-gelation. A median primary particle size of 0.5 µm permits film thickness of 60 µm without visible particles at 50× magnification. Gloss measured with ISO 2813 and cross-cut adhesion with ISO 2409 show no statistically significant change relative to unfilled control films at 10 wt% loading. The inorganic pigment does not migrate in cured coatings, as tested by contact migration for 72 h at 80°C. Compared with alumina-treated red iron oxides, Burgundy TRR maintains lower thixotropy in the extruder melt, allowing higher throughput before torque overload.

When UV-Stable Inorganic Pigmentation Must Replace Organic Red Formulations

Red organic pigments such as Pigment Red 170 and Pigment Red 254 provide higher chroma and tint strength at loadings below 2 wt%, but their lightfastness and weather resistance in exterior architectural coatings may be insufficient beyond 2000 h accelerated weathering. Burgundy TRR is selected when the formulation must maintain ΔE below 2.0 after 3000 h QUV-A exposure. Published data for this specific grade in exterior wood coatings is limited; comparative data for calcined iron oxide pigments in similar binder systems indicate ΔE values below 1.5 under the same test conditions. The inorganic pigment does not plasticize or cause migration in polyolefin matrices, whereas low-molecular-weight organic reds can exude under contact with PVC gaskets or plasticized films. Lightfastness of the inorganic grade is evaluated by ISO 105-B02 and typically remains stable beyond blue wool scale 7. The trade-off is lower chroma per unit loading compared with diketo-pyrrolo-pyrrole and naphthol reds; formulations requiring high-gamut decorative reds may need blending with organic pigments, which then requires separate weather-resistance validation.

Polyolefin masterbatch dilution studies on a 44:1 L/D co-rotating twin-screw extruder with 70% torque and 180–220°C barrel temperatures show that a 50 wt% Burgundy TRR in LDPE carrier is let down at 2–6% in HDPE injection moulded plaques. Melt flow index of the masterbatch is 15–25 g/10 min at 190°C/2.16 kg per ISO 1133-1:2022. Colour development is assessed by ASTM D2244; ΔE between the masterbatch moulded at 200°C and 240°C remains below 1.0, indicating stable thermal history response. The pigment does not increase the base resin yellowness index beyond 0.5 units at 4% letdown. In comparison with competitive burgundy-shade concentrates based on organic reds, the inorganic product shows lower colour strength per unit loading but eliminates migration-related staining of adjacent thermoplastic parts.

Thermal Degradation Pathways and Handling Boundaries

Thermogravimetric analysis of Burgundy TRR at 10°C/min under air shows mass loss below 0.5% up to 800°C. The product is insoluble in water, dilute acids, and alkalis; however, prolonged exposure to pH below 3.0 can leach surface iron and shift shade toward yellow. This restricts use in acid-catalysed coatings unless acid scavengers are added. The product should not be dry-blended with amine-functional silanes in concentrate form because adsorbed moisture can initiate premature hydrolysis. If stored above 60% relative humidity, pre-drying at 120°C for 2 h is required before powder coating. The material is not currently approved for direct food-contact applications under 21 CFR 178.3297 unless the final article meets extractives limits; users are responsible for compliance verification. Dust control follows standard inorganic pigment hygiene practices with a recommended respirable dust limit of 5 mg/m³ in production areas. Unlike organic red pigments, Burgundy TRR does not support combustion and does not release aromatic decomposition products during polymer processing or waste incineration.