Optical brightener

Buyers must focus on the chemical structure (e.g., Stilbene, Coumarin, or Benzoxazole) as it determines the application. Key metrics include E1%1 value (extinction coefficient) which indicates whitening strength, purity levels (typically >99%), and particle size for uniform dispersion. For plastics, ensure the melting point aligns with your processing temperature to avoid degradation.

Selection depends on substrate compatibility. For polymers like PET or PC, use OB-1 due to its high heat stability (up to 350°C). For PVC or PE, OB is preferred for its excellent solubility. In detergents, look for CBS-X because of its high solubility in water and chlorine stability, while textile applications require agents with high affinity for specific fibers (e.g., polyester vs. cotton).

Ensure the supplier provides a valid SDS (Safety Data Sheet) compliant with GHS standards. For exports to the EU, REACH registration is mandatory. If the brightener is used in food packaging, it must meet FDA (21 CFR 178.3297) or EU Food Contact regulations. Always verify ISO 9001 certification to ensure batch-to-batch consistency.

Conduct a whiteness index (WI) test using a spectrophotometer to measure the CIE Whiteness. Perform a lightfastness test to see how quickly the whitening effect fades under UV exposure. Additionally, check for migration resistance in plastics to ensure the chemical does not 'bleed' to the surface over time.

The primary risks include quality inconsistency between samples and bulk orders, and logistical delays due to the classification of some chemicals as hazardous. To mitigate this, use third-party inspection services (like SGS or Intertek) to test the active ingredient content before the balance payment is made.

Focus on Tiered Pricing; chemical costs fluctuate with raw material prices, so request a price validity period. Negotiate for customized packaging (e.g., 25kg fiber drums vs. IBC tanks) to optimize shipping space. Ask for free samples (50g-100g) but offer to cover the express shipping cost to show serious intent.

Optical Brighteners are sensitive to light and moisture. Ensure the contract specifies UV-protected, moisture-proof packaging. During shipping, avoid co-loading with strong oxidizers. For logistics to specific regions, ensure the HS Code (usually 3204.20) is correctly declared to avoid customs seizures or incorrect duty applications.

Always conduct transactions through secured payment channels provided by professional platforms like Made-in-China.com. Utilize Trade Assurance programs to protect your capital. Before a large contract, verify the supplier's Business License and check if they have a Production License for Hazardous Chemicals if applicable in their jurisdiction.