Pillow filling

PET spun into crimped fibres gives a polyester-filled pillow its loft.

Pillow filling, illustrative image

Material

Polyester fibre filling: PET

Material selection rationale

Fine flexible fibres
A mass of bent fibres traps air and feels soft.
Crimped shape
Wavy fibres help the filling keep volume instead of lying flat.
Loft from fibre shape
Crimp and fibre arrangement hold spaces of air. PET chemistry alone does not explain how high or supportive a pillow feels.

How it becomes a product

  1. Spin and crimp: PET is melt-spun, drawn and crimped into staple fibres. Fibres are drawn, given the selected crimp or finish and opened before filling a separately made casing.
  2. Open and fill: The fibres are separated into a loose filling and enclosed in a sewn cover.

Preparation routes

Terephthalic acid route

Esterification, then polycondensation. The acid and diol first form ester-linked intermediates, releasing water. Further reaction builds longer PET chains while small molecules are removed. Both feedstocks have two reacting ends, enabling repeated links rather than just one small ester. Balanced functional groups and extensive conversion are needed for long chains.

Industrial catalysts and controlled heating assist the reaction; they are not alternative monomers. Removing small-molecule products drives the reversible stages towards chain formation.

  1. Polyesters: manufacture and usesChemical Industry Education Centre, University of York

Dimethyl terephthalate route

Ester exchange, then polycondensation. The ester reacts with ethylene glycol, releasing methanol in the first stage. Further reaction builds PET chains. This complete input pair is an alternative to the acid route. Methanol identifies the initial ester-exchange route; the terephthalate and ethylene-glycol fragments retained in PET match those from the acid route.

Catalysts and heat support ester exchange and chain growth; excess glycol and other small molecules are removed as the process proceeds. Feedstock substitution changes the reaction sequence and by-products, not the required two-ended glycol.

  1. Polyesters: manufacture and usesChemical Industry Education Centre, University of York

From p-xylene to terephthalic acid

  1. p-Xylene + Oxygen from air → Terephthalic acid

    Catalytic air oxidation changes both methyl groups into carboxylic acid groups while retaining their opposite positions on the benzene ring. Acetic acid is the process solvent, not an extra carbon fragment in terephthalic acid. Recovery, purification and crystallisation produce the purified diacid used in polyester manufacture.

  1. Purified terephthalic acid: products and manufacturing, annual report 2023, page 94INEOS Quattro

From ethene through ethylene oxide to ethylene glycol

  1. Ethene + Oxygen + Water → Ethylene glycol

    First, catalytic partial oxidation converts ethene to ethylene oxide, a three-membered epoxide. In the selected thermal route, water then opens the oxide ring to form ethylene glycol. Heavier glycols also form and are separated. The two-carbon unit reaches PET through a diol, unlike the direct addition polymerisation of ethene into polyethylene.

  1. Ethylene oxide and ethylene glycol process technologyShell

Sources

  1. Polyester fibres for pillows and beddingADVANSA
  2. Polyesters: manufacture and usesChemical Industry Education Centre, University of York