Terylene crystallinity

As a result of these investigations it is generally agreed that naturally-occurring cellulosic fibres contain of the order of 60 to 70 per cent of molecules orientated in crystalline structure. The regenerated celluloses contain 30 to 40 per cent, Terylene 50 per cent, and nylon between 50 and 60 per cent. 

Terylene, like nylon, is thermoplastic and can have permanent pleats or shapes imposed by the action of heat with or without steam. It breaks under loads of 4-2 to 4-8 g per denier and the continuous filament has an extension of 22 to 30 per cent at the breaking point. The fibre has marked crystallinity as shown by the X-ray diffraction diagram illustrated in Fig. 2.7, and by the low moisture regain of 0-4 per cent. The closely packed and highly-orientated molecules make Terylene markedly hydrophobic and difficult to dye. Modified polyester fibres are produced with an affinity for both disperse and cationic dyes. 

Terylene is highly crystalline and markedly hydrophobic. It is not, there-, easily penetrated by dyes with large molecules. It also has no chemic-active groups and cannot combine with dye anions or cations. In ractice, polyester fibres are dyed with disperse dyes, a few azoic combinations, and with those disperse dyes which can be diazotized and coupled in situ. 

Condensation polymers are governed by the same rules. Chains are usually less regular, but more polar. At least two polymers show such high crystallinity that they have been used for new fibres Nylon (polyamide) and Terylene (polyester). 

Step growth polymers are governed by the same rules. In many of these polymers, chains are less regular, but more polar. Two polymer structures which lead to such high crystallinity that the polymers have been used for fibres are the polyamide structure of Nylon , and the polyester structure of Terylene . The latter is a polymer derived from /erephthalic acid and Qi iylene glycol from which the name derives. Bulk nylon is a waxy solid of such toughness that a major use is in gear wheels in small machinery. 

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