1,2-Propanediol properties/recovery

Poly(trimethylene terephthalate) (PTT) is a polymer with very useful properties. As a textile fibre it has excellent softness, stretch and recovery. As a resin it has excellent barrier properties. Developed over 60 years ago, PTT has not been very widely used compared to poly(ethylene terephthalate) (PET) as one of the key monomers 1,3-propanediol (PDO) has been expensive. 

The superior properties of polypropylene terephthalate) (PPT) polymer and fibers over the chemically analogous poly(ethylene terephthalate) (PET, used for soda bottles) and poly(butylene terephthalate) (PBT) have been well known for several decades PPT fibers are much more elastic and less brittle than PET and offer better recovery from stretching than PBT they are also easier to dye than either PET or PBT. Compared to the intermediate for PET, ethylene glycol, which is available inexpensively from ethylene oxide, and to that for PBT, butanediol, likewise available inexpensively from butene or butadiene, the intermediate for PPT, 1,3 propanediol (1,3-PPD or PDO), was not - and on a large scale is still not - available. Three processes, two chemical ones and one biotechnological, compete to change this situation (Figure 20.10). 

Together with purified terephthalic acid, 1,3-propanediol is used to produce polytrimethylene terephthalate (PTT), a polymer with remarkable "stretch-recovery" properties. The desirable attributes of PTT have been known since the 1940s, but high production costs prevented its entrance into the polymer market (29). In the 1990s, a new fossil-based route to 1,3-propanediol was developed enabling the production of PTT for higher-value applications, and PTT polymers were introduced into the market by DuPont and Shell Chemicals (29,30). 

Abstract Poly(trimethylene terephthalate) (PTT) fibers, as a new type of polyester, are characterized by much better resilience and stress/recovery properties than poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). PPT chains are much more angularly structured than PET and PBT chains and such chains can be stretched by up to 15% with a reversible recovery (Ward et al. 1976). These properties make PTT highly suitable for uses in fiber, carpet, textile, film, and engineering thermoplastics applications. 1,3-Propanediol (PDO), as one of the polyester raw materials for PTT, has also attracted interest. 

Poly(propylene terephthalate) (PPT), the first and most studied polyester of 1,3-propanediol, is available in the market [2]. The polymer is suitable for industrial fiber production. PPT fibers are characterized by much better resilience and stress/recovery properties than PET and PBT. These properties are due to the crystal structure of PPT. PPT chains are much more angular structured than PET and PBT chains due to the odd number of methylene groups of the diol segment. Therefore these chains can be stretched up to 15% with a reversible recovery [3]. PPT is anticipated to gain a significant share in the thermoplastic polyesters market in the next years. However, like the other terephthalate polyesters, PPT is not susceptible to degradation in the environment. 

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