It is worth noting that same optical brightener gain different whitening effect in rigid PVC (RPVC) and flexible PVC (FPVC). Bisbenzoxazole or phenyl coumarin group are often used in PVC. When PVC powder, heat stabilizer, fluorescent brightener agent dry mixed together, optical brighteners were evenly dispensed. For flexible PVC, OBAs were dissolved or dispersed into plasticizer. It is better to add FWAs in masterbatch form. For transport PVC, optical brightener plus plasticizer masterbatch or OBAs plus PVC masterbatch were used.

Dosage:

normally,50mg to 100 mg per kg is enough. To meet the requirement of extreme white with filler inside, 500mg/kg optical brightener agent is added. In rutile titanium dioxide PVC system,1000mg/kg OBAs is suggested. in most cases, the plasticizer in PVC had little effect on OBAs, the process temperature is normally 100 to 200 degree which means optical brightener heat stability shall meet. We shall pay attention to solubility and immigration which is important to flexible PVC.