關於顏料原料嘅問題?????

Paint consists of three parts: resin, pigment and light blocker.

Resin is the liquid part of paint. It looks like paste or glue. Resin iss a kind of prepolymer. The most common constitution of polymer is condensation of adipic acid (hexanedioic acid and butane-1,4-diol. The resin is called prepolymer since the polymerization is not completed. You can imagine that if they exist in monomer form, it flow freely as water. If polymerization compleyed it is a piece of plastic block. The polymerization completes after painting on a surface so exposure to oxygen.

Pigment gives colour to paint. The chemical composition varies depends on colour. Due to identification of some toxic and carcinogenic pigment, formula of the same colour pigment changes from time to time.

If there is only resin and pigment, the paint will become transparent. Light blocker make paints not transparent so it can cover stains and old paints. Titanium dioxide (TiO2), alumina (aluminium oxide, Al2O3) and silica (silicon dioxide, SiO2) are common powder added into paint as light blocker. In the past, lead sulphate was used and it is banned since it is harmful to central nerve system (especially children).