Properties and Structure of Nylon

Various works on the properties and structure of aliphatic polyamide have been published. However, very little work has been completed on the aliphatic polyamides of nylon-3. 

The crystal structure of nylon-3 was determined by Masamoto et al.[18] using the X-ray diffraction pattern. The foure crystal structures of nylon-3 have the designated modifications I, II, III, and IV. 

The crystal structure of the drawn nylon-3 fibers (modification 1) was determined using X-ray diffraction. This structure is similar to the alpha-crystal of nylon-6 and nylon-4, and the unit cell is monoclinic. The unit cell is as follows  

In this structure, the b-axis was found to be normal to the basal plane. The theoretical density for nylon-3 with four monomeric units in a unit cell is 1.39 g/cm- and the density was determined in a density gradient column of toluene and carbon tetrachloride to be 1.33 g/cm at 25 C. 

It is interesting to note that nylon-3 has a monoclinic unit cell which is unlike other ordinary odd-numbered nylons such as nylon-7, -9 or -11, which display a triclinic or pseudohexagonal unit cell. The amide concentration in the polymer might be a deteremining factor in the formation of a monoclinic, triclinic, or pseudohexagonal structure. 

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