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Simplified multi-stage manufacturing of PET - Similar (trans)esterification/prepolymerisation followed by polycondensation applies to most polyester products manufacturing

Polyesters are a broad family of polymers formed by step-growth polycondensation between dicarboxylic acids (or their esters) and diols, with PET representing the largest-volume commercial example but not the only one. The diversity of the polyester family arises almost entirely from which diacid and diol are paired:

General polycondensation equation:

(n+1) HO—R—OH + n HOOC—R′—COOH
→ HO—[R—OOC—R′—COO]_n—R—OH + 2n H₂O

Two monomer routes converge on the same oligomeric intermediate chemistry:

• Direct esterification (acid + diol → ester + water) 
• Transesterification (dialkyl ester + diol → ester + alcohol, used historically with DMT, releasing methanol).

Industrial polyester production universally proceeds through two macro-stages, with absolute conditions varying by polymer and by licensor configuration:

• Stage 1 — Esterification/transesterification (prepolymerization)
• Stage 2 — Melt-phase polycondensation
• Stage 3 (optional) — Solid-state polymerization (SSP)

The technology landscape has undergone material ownership changes since the technologies were first developed and newer technologies were developed, in particular by Chinese companies. 

China now dominates global polyester supply, holding roughly 60–65 percent of global capacity (approximately 85–90 million tonnes/year of a ~135–140 million tonne global total in 2026), up from 59 million tonnes/year in 2019, and accounting for nearly half of global polyester exports.

Read the comprehensive review on polyester formation via polycondensation here.

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