Dehydrochlorination of Poly(vinyl chloride) by Wet Treatment

Abstract

As a part of a series of studies on disposal and utilization of waste plastic, poly(vinyI chloride)(PVC)was dehyrochlorinated by wet treatment. The treating conditions and the chemical and physical structures of the resulting product were investigated.
The wet treatment was carried out in autoclave by heating PVC with an aqueous solution of such as NaOH, KOH or Ca(OH)20r with suspension of Fe powder as an acceptor of hydrochloric acid PVC was completely dehydrochlorinated at 250-270C and the dehydrochlorination product was powdery or granular Iike the starting PVC and colored yellow, yellowish brown, reddish brown and black Infrared, ultraviolet and visble spectral studies indicated that the dehydrochlorination product formed in the presence of NaOH has a chemical structure which is mainly composed of conjugatedl polyene containing up to 6-8 polyenes, ether cross link: ages and conjugatedketone resulting from oxidation of conjugated polyen. e. The tone of yellow color is due to the so-called bleaching effect by oxygen. In the presence of Fe, aromatic condensed ring containing up to 3-5 rings resulting from conjugated polyene, seems li: kely to be the origin of its chemical structures a: nd black color. It was inferred that Na ions relate to the protection of the conjugated polyene chain and Fe2 ions to the formation of aromatic ring
The phyical structure was examined by the measurements, f the pore vlume and the pore distribution. Diffusio: n of the additive through PVC particles was found to affect the physicaI structures.