The effect of crystallinity and crosslinking on the depression of the glass transition temperature in nylon 6 by water

Abstract

Abstract The influence of crystallinity and crosslinking on the depression of the glass transition temperature in nylon 6 by water has been investigated by dynamic mechanical methods. Radiation crosslinking by high‐energy electrons was effective in preventing morphological changes during the measurement of the incremental change in heat capacity (Δ C p ) at T g , which was performed by differential scanning calorimetry. The experimentally determined value of Δ C p , when normalized to account for the crystalline phase, was found to deviate from a linear two‐phase relation and was reduced further than would be expected based on this model. It is proposed that nylon 6 is best described by a three‐phase model which consists of a crystalline domain, a wholly amorphous domain, and an “intercrystalline” region. The importance of this in explaining the relatively large depression of T g by small quantities of water is illustrated by applying equations derived to account for the compositional dependence of T g in polymerdiluent mixtures, based on a classical thermodynamic interpretation of the glass transition phenomenon.