MELTING POINT DEPRESSION OF NYLON 6 BY METHOXYMETHYLATION (II)

Melting point depression phenomena of nylon 6 by methoxymethylation are divided into two main classes. In the first stage, the increase in the substitution ratio 1-XA of methoxymethyl residue causes a melting temperature depression according to modified Flory's equation with a=2, where, Tm is the melting temperature of a copolymer, Tm° the melting temperature of major component polymer, hu the heat of fusion per structural unit, XA the mole fraction of major component structural unit, a the constant (_??_1) and k the Boltzmann's constant. However, (1) for the highly amorphous samples, over 1-XA≈0.25, the melting peak disappears and (2) for samples with high crystallinity, over 1-XA≈0.10, the melting point depression becomes sluggish and/or the melting peak temperature is almost unaltered. In the latter case, it may be supposed that the methoxymethyl residues substituted on the crystalline surfaces play an important part in the suppression of recrystallization and in keeping the cohesive states of crystalline regions before the DSC measurements.