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

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 (ΔCp) at Tg, which was performed by differential scanning calorimetry. The experimentally determined value of ΔCp, 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 Tg by small quantities of water is illustrated by applying equations derived to account for the compositional dependence of Tg in polymerdiluent mixtures, based on a classical thermodynamic interpretation of the glass transition phenomenon.

Glass Transition of Extruded Wheat, Corn and Rice Starch

“…Crystallites, embedded in amorphous regions, reduce the mobility of polymers and increases the rigidity of the amorphous zones. Such a phenomenon is equivalent to the effect of physical cross-linking, which increases the T g of amorphous materials [16,17]. Results from Zeleznak and Hoseney [18] confirm that the T g of starch is affected by the presence of crystalline regions.…”

Enthalpy relaxation of gelatin in the glassy state

“…T g, c 1/2 p ) of the partially crystalline gelatin was slightly higher than that of the amorphous structure. This phenomenon is typical for many semi-crystalline synthetic polymers [33,34] and some biopolymers [28,35,36] and is discussed in more details in the following section. As expected both the glass transition and the melting endotherm shifted to lower temperatures as the water content increased reflecting the plasticisation of the polymer by water.…”

The Structure and Properties of Typical Melt-spun Fibres

“…The depression in glass-transition temperature in the presence of water was evaluated by Jin et al [85] with a proposed threephase model consisting of a crystalline domain, a wholly amorphous domain, and an inter-crystalline region.…”

“…The water-induced plasticization behaviour of nylon 6 at different crystallinities was studied by evaluating a predicted depression of glasstransition temperature of only those regions capable of activation at the transition (bulk amorphous regions) [275].…”