Thermal Analysis on Isothermal Crystallization Phenomena from Melt of Nylon 6

Abstract

The phenomena of isothermal crystallization from melt of nylon 6 fractions having the numberaverage molecular weight Ṁn from 830 to 43200 were systematically investigated in the temperature range from 191 to 207° C by means of differential scanning calorimetry. The exponent n in Avrami's equation; θ=exp (-ktn) (θ=uncrystallized weight fraction, k=rate constant, t=crystallization time) decreases drastically from 6 to unity as the crystallization proceeds. This is not due to the fractional crystallization, but to the change in crystallization mechanism during crystallization. n increases at higher crystallization temperature Tc and for higher Ṁn. The crystallization rate, defined by half time t1/2, decreases as Ṁn increases. The DSC curve for the crystals grown at θ=0 often exhibits triple-peaks, i.e., Tm2(1)