Polyamides thermostability

The production of P. Y. 187 has recently been discontinued. It was a special-purpose pigment for polyamide. Thermostable up to 320°C in this plastic material, the pigment furnishes greenish yellow shades. 1/1 SD samples score only as high as step 4 on the Blue Scale for lightfastness. 

Lin, /. and Sherrington, D. C Recent Developments in the Synthesis, Thermostability and liquid Crystal Properties of Aromatic Polyamides. Vol. Ill, pp. 177-220. 

It has often been proclaimed that 5-hydroxymethylfurfural (HMF, Fig. 8.35) could be an ideal cross-over compound between carbohydrates and petrochemistry [184], as it is a bifunctional heteroaromatic compound that is accessible from fructose in one step. It was expected that HMF could be developed into a valuable synthetic building block and that its derivatives, such as furan-2,5-dicarb-oxylic acid (FDA), would be able to compete with fossil-derived monomers for use in thermostable polyesters and polyamides. 

Hai, T., Oppermann-Sanio, F.B., and Steinbiichel, A. (2002) Molecular characterization of a thermostable cyanophycin synthetase from the thermophylic cyanobacterium Synechococcus sp. MA19 and in vitro synthesis of cyanophycin and related polyamides. Appl. Environ. Microbiol., 68, 93-101. 

Recent Developments in the Synthesis, Thermostability and Liquid Crystal Properties of Aromatic Polyamides... 

In the literature, efforts directed towards achieving more soluble, highly thermostable polyamides have been oriented in thrre main directions a) the introduction of substituents of varying chemical nature onto the benzene ring of monomers b) the use of monomers containing several benzene rings linked together by flexible chains and c) the use of heterocyclic monomers. 

The introduction of alkyl groups onto the benzene rings of aromatic polyamides has proved to impart higher solubility to the polymers. The thermostability of these however is reduced because of insufficient resistance of the alkyl substituents towards oxidation. Some studies have therefore been carried out using aromatic substituted monomers, for instance, phenyl [27], phenoxy and thio-phenoxy [28] substituted diamines, and phenyl [27, 29, 70] and phenoxy [30] substituted diacids. These have been used to prepare polyamides 15. In Table 4... 

Chaudhuri et al. [22a] in their study of the thermostability of wholly aromatic polyamides have introduced various polar groups onto the polymer, e.g. NO2, COOH, OH, SO3H, etc. Compared to methylated or chlorinated polymers, the stability of polyamides 16 is lower, and decreases in the following order NO2 > COOH, OH > SO3H... 

In case of the oxybenzoyl group, these two effects seem balanced. When an iminobenzoyl group is introduced, the second effect is more important. It is interesting to notice that the introduction of a benzamide group onto a different part of the polyamide has an opposite effect on the Tg. As far as the thermostability is concerned, polyamides 17,18 substituted with an amide group have higher stability than the oxybenzoyl substituted sj des. 

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