Polyurethanes
Polyurethanes
(PU) are one of the most versatile of all polymer
families. The plastics products derived
from them appear everywhere from soft flexible
foams through fibres, fabrics and rubbers to hard
durable coatings.
PU is often based on addition reactions of
polyisocyanates and polyols, although other co-reactants
can be used. Selection of functionality of
reactants and processing conditions enables
precise formation of this huge range of products.
Otto Bayer patented PU adhesives and elastomer
types in 1937 whereby improved tyre cord bonding
could be achieved. Improved cast elastomers,
fibre and plastic applications followed, e.g. I.
G. Farben Industrie 1941 and Bayer 1947.
The demand for domestic and industrial
applications in the 1960s led to huge production
of flexible foams in furniture, rigid foams for
insulation and sandwich panel construction.
‘Wet-look’ apparel provided fashion
emphasis also.
Further detailed developments in formulation
and applications in later years provided superior
spray foam, self-skinned foam, powder and stove
finishing coatings, etc. Of particular note
were reaction injection moulding RIM) and ability
to produce controlled reinforced structures RRIM)
for engineering applications. Also
significant was the ability to produce controlled
block copolymer thermoplastic elastomers of which
Lycra (Du Pont) is notable in athletic clothing.
PU in its great variety has benefit in
everyday life ranging from soft foams to rollers,
footwear and tyre treads, and to durable ceramic
like coatings in the aerospace, marine and
chemical industries.
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