HMC Polymers is a joint venture between international and leading local Thai companies and individuals established in 1983.

The joint venture parties included Montell Polyolefins (formerly known as Himont Incorporated, later in October 2000 it was known as Basell, currently known as LyondellBasell). Montell Polyolefins was formed in April 1995 by the merger of the majority of the polyolefin operations of the Royal Dutch/Shell Group of Companies and the Italian company, Montedison S.p.a.

The group of leading Thai companies and individuals included Bangkok Bank, a major Thai financial institution; Hua Kee – primarily active in paper manufacturing and distribution, real estate development, hotels and petrochemicals; and Metro Group, one of Thailand's large(ST/ER) trading firms with a long history of plastics marketing experience in Thailand.

With Thai Board of Investments promotional privileges, HMC Polymers commissioned its first production line in October 1989 in the newly formed Eastern Seaboard Mab Ta Phut Industrial Complex.

This first production line had a capacity of 100,000 tons per year of homopolymer (only propylene) and random copolymer (propylene and ethylene) of polypropylene resin. The capacity for this first production line was later increased to 160,000 tons per year. In December 1996, HMC Polymers commissioned a second polypropylene production line. This second production line was designed and installed with the latest technology developed by Montell. It provided HMC Polymers with the additional capability to produce impact copolymer (propylene and ethylene), terpolymer (propylene, ethylene and butene) and high crystalline polypropylene resin products.