Solvent Red 135 / Solvent Dyes

CAS No.:  20749-68-2 / 71902-17-5

Molecular formula:   C18H6Cl4N2O

Features: Good heat resistance and light fastness, good migration resistance and high tinting strength with wide application.

Application : Used for PS PET PA PC ABS (polyolefin,polyester,polycabonate,polyamide,plastic) .

Products description: 

Solvent Red 135 is a yellowish transparent red oil solvent dye.

It has good heat resistance and light fastness, good migration resistance and high tinting strength with wide application.

Solvent Red 135 is recommended for PS PET PA PC ABS .

Identification Information:

Chemical Family                        Naphthalene ring acetone Series

Color Index: Solvent Red 135

Molecular formula:   C18H6Cl4N2O

CAS No.:  20749-68-2 / 71902-17-5

Product specification

Appearance Red powder

Tinting Strength 100±3%

Shade Color Similar to the standard,

Ash ≤ 1.0%

Moisture ≤ 1.0%

Color Differential ValueΔE ≤ 0.8

Bulk density (g /cm³):                                                  1.74

Melting point (°C):                                                       318

Physical Properties: 

Product Overview

Solvent Red 135 (CAS 20749-68-2 / 71902-17-5) is a naphthalene-ring acetone series solvent dye delivering a yellowish transparent red with outstanding thermal durability. Its melting point of 318 °C — among the highest in the Solvent Red family — enables processing in high-temperature engineering plastics such as polycarbonate (340 °C) and PET (320 °C), well beyond the limits of conventional solvent dyes. The dye demonstrates light fastness ratings of 7-8 (transparent, PS) and consistent color retention across PS, ABS, PC, and PET substrates, making it a versatile workhorse for injection molding, extrusion, and fiber spinning. Unlike the blue-shade Solvent Red 195, SR135 provides a warmer, golden-tinged red ideal for automotive tail light lenses, PET bottle preforms, and polyamide monofilaments where a rich amber-red aesthetic is required. Its tetrachloro-substituted naphthalene core provides inherent migration resistance without the need for polymeric stabilizers in most application matrices.

Application Profile 

Note: ● = Recommended   ○ = Potential use   – = Not recommended

Recommended Dosage

Transparent: 0.05% | Non-transparent: 0.08%

Packaging: Regular packaging in 25 kg paper drums, cartons or bags. 450 kg per pallet.

Technical Parameter Interpretation

• Appearance (Red Powder): Consistent particle morphology ensures uniform dosing and predictable dispersion behavior across automatic feeding systems.
• Tinting Strength (100±3%): Precision-controlled color intensity — ensures that 0.05% dosage consistently delivers the target shade, eliminating costly reformulation between production campaigns.
• Ash Content (≤1.0%): Low mineral residue preserves optical clarity in transparent PET and PC applications, preventing haze formation during injection stretch blow molding.
• Moisture (≤1.0%): Strict moisture control prevents hydrolysis at PET processing temperatures (280-320 °C), where residual water can cause polymer degradation and bubble defects.
• Color Differential ΔE ≤0.8: Industry-leading batch consistency — this tight specification minimizes visual variation in multi-cavity molds and across production shifts.
• Bulk Density (1.74 g/cm³): Higher bulk density compared to many solvent dyes (typical 0.3-0.8 g/cm³) — reduces dusting during handling, improves dosing accuracy, and minimizes airborne particulate in the production environment.
• Melting Point (318 °C): Exceptionally high melting point allows processing in polycarbonate (typical processing 280-320 °C) and PET (260-300 °C) without dye decomposition, expanding the application range beyond that of lower-melting solvent reds.
• Light Fastness SD 1/3 Opaque (6-7 PS, 6 PC/PET): Adequate for indoor applications and short-term outdoor exposure; for long-term outdoor use, consider UV-stabilized formulations or pigment alternatives like PR254.
• Light Fastness SD 1/25 Transparent (7-8 PS, 7 PC/PET): Excellent transparency fastness — at low concentrations in PS, the dye maintains color integrity comparable to high-performance pigments under standard indoor lighting conditions.
• Heat Resistance SD 1/3 Opaque (300 °C PS, 290 °C ABS, 340 °C PC, 320 °C PET): Exceptional thermal stability across the four most common engineering plastics — PC at 340 °C is a standout performance that few solvent dyes can match.

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📩 Need more details? Request TDS, SDS, or a free sample for testing.

Frequently Asked Questions — Solvent Red 135

What makes Solvent Red 135 suitable for polycarbonate (PC) applications?

Solvent Red 135 achieves heat resistance up to 340 °C in polycarbonate at 1/3 SD opaque loading, which is critical because PC typically processes at 280-320 °C. The dye’s naphthalene-ring acetone molecular structure provides thermal stability that prevents color shift, outgassing, or decomposition during high-temperature injection molding. Additionally, its light fastness rating of 7 in transparent PC ensures that LED-lit applications like automotive interior switches and electronic device indicators maintain consistent color throughout the product lifecycle. The combination of high-temperature tolerance and good transparency makes SR135 a preferred choice for tinted PC lenses, light pipes, and optical diffusers.

How does Solvent Red 135 compare to Solvent Red 195 for ABS coloring?

Key differences: SR135 delivers a yellowish-red tone with heat resistance of 290 °C (ABS, 1/3 SD), while SR195 provides a blue-shade red with 250 °C heat resistance (ABS). For ABS applications: SR135 offers better thermal headroom (290 °C vs. 250 °C) and lower cost per kilogram of colored resin due to higher tinting strength per unit mass. However, SR195 provides superior light fastness (8 vs. 5-6 opaque) and a cooler red tone preferred for consumer electronics. Choose SR135 when processing at the upper end of ABS temperature range (240-280 °C) and when a warm red is desired; choose SR195 for maximum UV stability and blue-toned reds.

Can Solvent Red 135 be used in PET bottle preform coloring?

Yes, SR135 is well-suited for PET applications with heat resistance up to 320 °C. At the recommended transparent dosage of 0.05%, it produces a consistent amber-red tint in PET preforms without affecting intrinsic viscosity or causing acetaldehyde generation — two critical quality parameters in bottle-grade PET. The dye’s migration resistance prevents color bleed into beverage contents during hot-fill processes (85-95 °C). However, for carbonated soft drink bottles requiring extended UV protection, consider combining SR135 with a UV absorber, as its light fastness (6-7 opaque) may be insufficient for prolonged direct sunlight exposure on retail shelves.

What is the chemical family of Solvent Red 135 and why does it matter?

Solvent Red 135 belongs to the naphthalene-ring acetone chemical series — a class of anthraquinone-related solvent dyes characterized by a tetrachloro-substituted naphthalene core condensed with an acetone bridge. This molecular architecture provides three key performance advantages: (1) the rigid fused-ring system delivers the 318 °C melting point — among the highest for solvent reds; (2) the four chlorine substituents enhance migration resistance by increasing molecular weight and reducing polymer chain mobility; (3) the acetone-derived bridge contributes to good solubility in moderately polar solvents like dichloromethane. Understanding this chemistry helps formulators predict compatibility with specific polymer-solvent systems and anticipate potential interactions with other package components like slip agents and antistats.

Disclaimer: Specifications are for reference only. Always verify with our team and review TDS/SDS before product use. Full legal disclaimer.