Thermoplastic polyester composite molecular weight

Soft blocks are composed of linear, dihydroxy poly ethers or polyesters with molecular weights between 600 and 3000. In a typical polymerization of a thermoplastic polyurethane elastomer, the macroglycol is end capped with the full amount of aromatic diisocyanate required in the final composition. Subsequently, the end-capped prepolymer and excess diisocyanate mixture reacts further with the required stoichiometric amount of monomeric diol to complete the reaction. The diol links the prepolymer segments together while excess diol and diisocyanate form short hard-block sements, leading to the (AB)n structure illustrated in Figure 1. Block lengths in (AB)n polymers are frequently much shorter than those in anionically synthesized ABA block copolymers. 

The combination of processability and performance provided by these polymers makes them natural candidates for applications such as microelectronics laminates as well as structural and dielectric composites (2). The versatility provided by the use of phenolic feedstocks has allowed the extension of this chemistry into polyesters (i), classical photoresist chemistry (4), and thermally crosslinkable thermoplastics (5). It has also provided a method for thermally processing low molecular weight imide-containing oligomers into high molecular weight polyetherimides (d) In addition, oligomers which are useful as fluorinated lubricant fluids have been prepared (7). 

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