POLYESTER FIBERS BASED ON TEREPHTHALIC ACID

PBT was examined in detail in the early 1950s both in Europe and the United States as a
textile fiber. It had many attractive properties compared to PET; it could be melt-spun at
lower temperatures and, owing to its polymer chemistry, it was inherently whiter than PET.
As a fiber, it was much more elastic and had excellent resilience and recovery from small
deformations. It dyed easily with disperse dyes at the boil, not needing to be dyed under
pressure like PET. PBT fiber resisted the common photo-oxidative yellowing and it seemed to
have a bright commercial future. However, the reason why PBT never achieved the success of
PET in textiles was because 1,4-butanediol is significantly more expensive than ethylene
glycol. Also, PBT did not have the pleat-retaining properties of PET in blends. However, it
succeeded as a polyester carpet fiber, where its resilience and ease of dyeing were assets,
although it had to compete against nylon.
Another of the pioneer polyesters was polytrimethylene terephthalate (PTT). This was
recognized very early on as a fiber with outstanding resilience. PTT has been known in many
ways as an ideal textile fiber for over 60 years. It remained on the shelf until, in the last
decade, it became a commercial product owing to two new routes to the crucial intermediate
1,3-propanediol. One route is petrochemically derived (hydroformylation of ethylene oxide),
while the other is a fermentation route using corn sugar to make 1,3-propanediol directly
using genetically modified bacteria [40].
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Eastman Kodak introduced a new polyester as a staple fiber called ‘‘Kodel’’ in 1958. A
new diol was introduced to derive a patent-free composition of matter; a mixture of cis- and
trans-1,4- cyclohexanedimethanol made by the exhaustive hydrogenation of dimethyl terephthalate.
This polyester had a higher Tg than PET and also a higher melting point, but it was
successful enough to find a market. In recent years, the polyester has found use in polyester
carpets [41,42].