Physicochemical and mechanical degradation of polyamide 11 induced by hydrolysis and thermal aging

Abstract

This article deals with the effect of both temperature and water activity on polyamide 11 physicochemical and mechanical properties. The purpose of this work is to describe the ductile-brittle transition of polyamides during aging in a wet environment using a mechanical behavior model. For that it is necessary to make physicochemical analyzes (DSC, FTIR, GPC, viscosity) and mechanical tests (uniaxial tensile test and dynamic mechanical thermal analysis). All of these tests were performed on unaged samples and on aged samples for until 60 days. Two types of aging conditions were performed: In water in an acidic medium at temperature, and in purely thermal conditions in a neutral environment. Changes in mechanical properties with aging were observed in the polymer and were correlated to morphological changes deduced from the physicochemical characterizations. An increase of the second yield stress related to the recrystallization and a decrease of the strain at break due to the decrease of the molecular weight were observed during aging.

Comparative Characterization of Hot-Pressed Polyamide 11 and 12: Mechanical, Thermal and Durability Properties

“…Points 1 and 2 are the first and second yield stress, which correspond to the plasticization and breakage of crystals, respectively [ 61 ]. Moreover, point 3 is the beginning of necking, and the whitening phenomenon is significant at this point for thermoplastics [ 62 ]. The mentioned behavior of specimens under tensile load are compared in Figure 6 .…”

Modelling pure polyamide 6 hydrolysis: Influence of water content in the amorphous phase

“…The hydrolysis of polyamide has been extensively studied in the literature [8,[10][11][12][13][14][15][16][17][18][19][20]. The degradation process is described as a chemical reaction between amide and water leading to the formation of acid and amine due to a chain scission process in the polymer.…”

Dynamic Fracture of a Semi-Crystalline Bio-Based Polymer Pipe: Effect of Temperature

“…When the strain rate increases and/or the test temperature decreases the amorphous phase and thus the material becomes more brittle. This is also the case when the material is aged [13]. These different conditions can generate abrupt fractures and more precisely rapid crack mechanisms.…”

“…The material failure is generated by the coalescence of these microcracks when they reach a critical size [5] [10] [11]. The loading conditions (strain rate in particular), the environment (temperature [12] and humidity [13]) and the degree of crystallinity [14] [15] significantly affect the fracture behaviour of the material. When the strain rate increases and/or the test temperature decreases the amorphous phase and thus the material becomes more brittle.…”