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Optical Brightener[2]

Updated: 2026-09-16

Overview

Optical brighteners, also known as fluorescent whitening agents (FWAs), are synthetic organic compounds that enhance the appearance of materials by converting UV light into visible blue light. This optical effect counteracts yellowing and increases perceived whiteness. Developed in the mid-20th century, they are now indispensable in industries where visual appeal is critical. These compounds are chemically diverse, with common types including stilbene, coumarin, and pyrazoline derivatives. Their performance depends on molecular structure, with variations tailored for specific substrates like polyester (water-insoluble types) or cotton (water-soluble variants).

Physical and Chemical Properties

Optical brighteners exhibit strong fluorescence under UV light (360–400 nm), emitting blue-violet light (420–470 nm). Their effectiveness depends on quantum yield and photostability. Most commercial products are powders with fine particle sizes (<50 µm) for uniform dispersion. Chemically, they are designed to resist degradation during processing (e.g., high-temperature dyeing or extrusion). Key parameters include pH stability (typically 2–11), thermal resistance (up to 200°C for plastics applications), and compatibility with other additives like surfactants or pigments.

Main Applications

In textiles, brighteners are applied during fabric finishing (0.1–0.5% weight) to compensate for natural fiber yellowness. Paper industries use them in coating formulations (0.05–0.3%) to achieve high-brightness grades. Liquid detergents incorporate water-soluble types (0.01–0.1%) to counteract fabric graying. Plastics applications include PET bottles and PVC films, where heat-stable brighteners prevent yellowing during molding. Niche uses include cosmetics (e.g., shampoo for "cool tone" effects) and currency security features due to their UV-responsive properties.

Safety and Storage

Most optical brighteners are classified as low-toxicity (LD50 >2,000 mg/kg). However, powder forms require dust control measures to prevent respiratory irritation. EU regulations restrict certain FWAs (e.g., DSBP) in food-contact materials under Regulation (EC) No 10/2011. Storage requires airtight containers to prevent moisture absorption, which can cause caking. Shelf life is typically 2–3 years when stored below 30°C. Incompatible with strong oxidizers—separate from peroxides or hypochlorites.

B2B Procurement Guide

Industrial buyers should specify: (1) Substrate type (e.g., cellulose vs. synthetic fibers), (2) Processing conditions (temperature, pH), (3) Desired whiteness index (CIE or Berger scale), and (4) Regulatory compliance (e.g., OEKO-TEX® for textiles). Bulk pricing tiers typically start at 500 kg quantities. Sample testing is recommended to verify compatibility, as performance varies with material batch and processing methods. Leading manufacturers include BASF, Huntsman, and Archroma for textile applications; Keystone and RPM for paper grades.

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