Synthesis of High-Value Bio-Based Polyamide 12,36 Microcellular Foams with Excellent Dimensional Stability and Shape Recovery Properties

Abstract

The search for alternatives to petroleum-based thermoplastic polyamide elastomers (TPAEs) has recently drawn great interest. In this study, a bio-massed TPAE, PA12,36, was synthesized using 1,12-dodecanediamine (DDA) and fatty dimer acid (FDA, PripolTM1009) precursors via catalyst and solvent-free melt polycondensation. The molecular structure and molecular weight of the PA12,36 were characterized by 1H NMR, FTIR, and GPC. PA12,36 displayed a low melting temperature of 85.8 °C, an initial degradation temperature of 425 °C, and a glass-transition temperature of 30.4 °C, whereas it sustained satisfactory tensile strength (10.0 MPa) and superior strain at break (1378%). Furthermore, PA12,36 was foamed by supercritical CO2, and the cell size, cell density, and porosity were determined. The entangled long-chained FDA component generated a physically crosslinked network, which promoted the melt viscosity of PA12,36 against elongations of foam cell growth and increased foamability significantly. As a result, uniform structured cellular foams with a cell diameter of 15–24 µm and high cell density (1011 cells/cm3–1012 cells/cm3) were successfully achieved. The foaming window was widened from 76 to 81 °C, and the expansion ratio was increased from 4.8 to 9.6. Additionally, PA12,36 foam with a physically crosslinked structure presented a better creep shape recovery percentage (92–97.9%) and sturdier dimensional stability. This bio-based PA12,36 foam is a promising candidate to replace petroleum-based thermoplastic elastomer foams for engineering applications, particularly shoe soles.

Efficient Use of Secondary Raw Material from the Production of Polyamide Construction Products

“…Polyamides are thermoplastic materials that melt in the range of 220-250 °C and are most often processed using injection molding and extrusion [40]. The chemical structure of polyamides is composed mainly of amide groups that participate in hydrogen bonds, resulting in reduced interchain mobility, causing high melting points and strength [41]. Due to the wide range of products manufactured for the construction and automotive industries, using polyamide from recycling and post-production waste management brings significant environmental benefits.…”