Polyamides glass-clear

These materials are also often referred to as glass-clear nylons, which is different from the normal usage of the term nylon for fibre-forming polyamides and their immediate chemical derivatives. 

The irregular structure of the polymer indicates that it will be amorphous and glass-like. The presence of the p-phenylene group in the main chain and the lone methyl group leads to a high Tg of about 150°C. There is, somewhat surprisingly, a further transition in the range 220-228°C, the nature of which is not really understood. The polymer is more soluble than the crystalline aliphatic nylons. For example it will dissolve in 80/20 chloroform/methanol mixtures. 

Compared with aliphatic nylons it also shows greater rigidity and hardness, lower water absorption, low temperature coefficient of expansion, good resistance to heat and moisture, better electrical insulation properties, particularly under hot and damp condition, and of course transparency. 

Applications include flow meter parts, transparent housing for electrical equipment, sight glasses. X-ray apparatus windows, gear wheels, racks, counters and containers for solvents. 

Property Test method Units Grilamid TR-55 Trogamid T 

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Copolymers of high Tg but which are amorphous and thus glassy (the glass-clear polyamides ). 

Where transparency is required, a range of polymers is available. Polystyrene is the least expensive but polymethylmethacrylate has an outstanding high light transmission combined with excellent weathering properties. Also to be considered are the polycarbonates, glass-clear polyamides, SAN, butadiene-styrene block copolymers, MBS polymers, plasticised PVC, ionomers and cellulose esters such as cellulose acetate. 

The polycondensation of terephthalic acid with hexamethylene diamine produces a high melting temperature polyamide which can only be spun from concentrated sulfuric acid because of the high melting temperature of 370 C. If, however, terephthalic acid is polycondensed with a 1 1 mixture of 2,2,4-and 2,4,4-trimethyl hexamethylene diamine, I and II, an easily processed glass-clear amorphous polyamide is obtained. Glass-clear polyamides are also produced by the polycondensation of terephthalic acid with a mixture of the... 

A transparent polyamide with good properties is also obtained from iso-phthalic acid in combination with the diamine, V, and lauryl lactam. Ail these glass-clear polyamides compete with polycarbonate, but unlike the latter, are not susceptible to stress corrosion crazing. 

Another glass-clear polyamide was announced in the mid-1970s by Hoechst a polynorbomamide, it was marketed as Hostamid. The basic patent suggests that this material is a copolyamide of a mixture of isomeric bisamino-methylnorbomanes (Figure 18.26 (I) and (II)) with aliphatic or cycloaliphatic dicarboxylic acids with 2-20 carbon atoms or aromatic dicarboxylic acids with 7-20 carbon atoms as well as diamines, amino acids of lactams. The properties of this polymer are similar in many respects to those of Trogamid T, with a of... 

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