Influence of Epoxy Functional Chain-Extenders on the Thermal and Rheological Properties of Bio-Based Polyamide 10.10

Abstract

Bio-based polyamide 10.10 (PA 10.10) has excellent properties compared to other biobased  polymers such as polylactic acid (PLA) or polyhydroxyalkanoates (PHAs) and is therefore used in more technical applications where higher strength is required. For foam and filament extrusion,a good balance between strength and stiffness of the  polymer is needed. Therefore, two commercial chain-extenders (Joncryl® ADR types) with different epoxy functionalities are used to modify the melt properties of PA 10.10. The chain-extenders are used in a concentration range up to 1.25 wt.%. The range of glass transition temperature widens with increasing Joncryl® content, and the apparent activation energy shows a maximum at a concentration of 0.5 wt.%. Furthermore, the melting temperatures are constant and the crystallinity decreases with increasing chain-extender content due to the formation of branches. During the second heating run, a bimodal melting peak appeared, consisting of 𝛼-triclinic and pseudo 𝛾-hexagonal crystals. The weight average molar masses (Mw) measured by gel permeation chromatography (GPC) increased linearly with increasing ADR 4400 content. In contrast, the compounds containing ADR 4468 show a maximum at 0.5 wt.% and it begins to decrease thereafter. The rheological data show an increase in viscosity with increasing chainextender content due to branch formation. ATR spectra of the compounds show a decrease at the wavelength of the primary (3301 cm−1) and secondary (1634 cm−1) (-NH stretching in PA 10.10) amine, indicating that chain-extension, e.g., branching, takes place during compounding.

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