The unit was set in motion in the presence of Managing Director of National Petrochemical Company (NPC) Marziyeh Shahdaei on Monday.
The product is used in textile industry and is considered a strategic feedstock in the sector.
The unit supplies 110 tons of POY threat on a daily basis.
Nearly 90% of the plant's output is sold on the domestic market.
Located at the heart of Mahshahr Petrochemical Zone in southwestern Iran, Tondgouyan Petrochemical Plant is the biggest supplier of pure terephthalic acid and polyethylene terephthalate in Iran.