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Polyurethane preparation and uses

Short answer

Polyurethane is prepared by step-growth addition polymerization of a diisocyanate (e.g., TDI) with a diol, forming urethane links. Uses: flexible foams (mattresses, cushions), rigid foams (insulation), coatings, adhesives, elastic fibres (spandex), and medical devices.

Mention preparation and uses of polyurethane.

Preparation

Polyurethane is formed by step-growth addition polymerisation of a diisocyanate with a diol (polyol). For example, toluene-2,4-diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI) reacts with ethylene glycol or a polyether polyol:

n OCN–R–NCO + n HO–R'–OH → [–CO–NH–R–NH–CO–O–R'–O–]ₙ
 (diisocyanate)   (diol)         polyurethane

The urethane link (–NH–CO–O–) joins the units. No small molecule is lost. Water added in the mixture reacts with –NCO to give CO₂, which blows the polymer into a foam. With a higher functionality polyol a cross-linked polymer is obtained.

Uses

  • Flexible foams for mattresses, cushions and car seats.
  • Rigid foams for thermal insulation of refrigerators and buildings.
  • Paints, varnishes and coatings, adhesives and sealants.
  • Elastic fibres (spandex/Lycra), shoe soles, rollers, wheels and synthetic leather.
  • Medical uses such as catheters and artificial heart parts.

✓ Answer checked by Claude Opus 5.5 (high effort)

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