Water Plasticizes Only a Small Part of the Amorphous Phase in Nylon‐6

Abstract

It is known that Polyamide 6 absorbs water in its amorphous phase. The exact composition of the amorphous phase will determine the uptake process. The heterogeneity in the amorphous phase with respect to plasticization by water uptake is quantified in this paper using NMR relaxometry. It is shown that water occupies and plasticizes only a small part (∼6%) of the nylon matrix. This part is located in between the crystalline domains where polymer chain mobility is higher. At low moisture content (<4%) water molecules are tightly bound to the polymer and have the same dynamics. A highly mobile pool of guest-hydrogen nuclei is detected starting at a moisture content of 4%. Here, water is absorbed in clusters and the interaction between the polymer chains and water molecules decreases, leading to decoupling of the dynamics of water and polymer.

Structure–Property Relations in New Cyclic Galactaric Acid Derived Monomers and Polymers Therefrom: Possibilities and Challenges

“…By means of the introduction of various acetals the hydrophilicity of the polymer can be tuned, e.g., by the incorporation of bulky cycloaliphatic fragments the polymer might be more hydrophobic than typically observed for aliphatic polyamides. The absorbed water has a major influence on the properties of polyamides since it acts as a plasticizer, lowering glass transition temperatures. Moreover, water is known to stimulate water induced crystallization …”

Water diffusivity in PA66: Experimental characterization and modeling based on free volume theory

“…Water absorption is considered here at the scale of the films i.e. 100 micrometers and therefore the distribution of water in the amorphous phase is considered homogeneous, even if some recent studies have shown that some heterogeneities could occur at a macromolecular scale [29] [30].…”

The effect of annealing of linear and branched polyamide 46 on the phase composition, molecular mobility and water absorption as studied by DSC, 1H and 2H solid-state NMR

“…Annealing causes thermodynamically more favoured closer coupling of amide groups of adjacent chain segments in the amorphous phase resulting in a significant increase in the amount of rigid fraction of the amorphous phase (Figure 3), which is hardly accessible for absorption of small molecules. 34,77 This reduces the number of sites for water absorption. After annealing the level of water absorption by the amorphous phase corresponds to those of PA6 and PA66, taking into account the crystallinity and the amount of amide groups (Table 3).…”