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

Mohsen Bahrami,Juana Abenojar,Miguel Angel Martínez

doi:10.3390/polym13203553

Abstract

Chemically speaking, polyamide 11 (PA11) and polyamide 12 (PA12) have a similar backbone, differing only in one carbon. From an origin point of view, PA11 is considered a bioplastic polyamide composed from renewable resources, compared to oil-based PA12. Each of them has a number of advantages over the other, which makes their selection a challenging issue. Depending on the target application, diverse assessments and comparisons are needed to fulfill this mission. The current study addresses this research gap to characterize and compare PA11 and PA12 manufactured by the hot press technique in terms of their mechanical, thermal and durability properties for the first time, demonstrating their potential for future works as matrices in composite materials. In this regard, different characterization techniques are applied to the hot-pressed polymer sheets, including X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The mechanical performance of the PA11 and PA12 sheets is compared based on tensile tests and shore hardness measurement. The durability behavior of these two polyamides is evaluated in water and relative humidity conditions at different aging times. The experimental results show the ductile behavior of PA12 with respect to the quasi-brittle PA11. Both have a relatively small water and moisture gain: 1.5 wt% and 0.8 wt%, respectively. The higher crystallinity of PA12 (2.1 times more than PA11) with γ-phase is one of the leading parameters to achieve better mechanical and durability properties. The FTIR spectra displayed slight acid hydrolysis. Accordingly, absorbed water or moisture does not cause plasticization; thus, neither hardness nor dimension changes.

Highlights

To compensate for this research gap, the present study investigated the tensile, hardness, thermal and durability properties of hot-pressed polyamide 11 (PA11) and polyamide 12 (PA12) simultaneously for the first time
PA11 showed quasi-brittle behavior; after the elastic deformation, the specimens underwent yielding followed by a plastic deformation region
differential scanning calorimetry (DSC) results revealed that the predominate crystal phases in PA11 and PA12 are the triclinic α-phase and pseudohexagonal γ-phase, respectively, resulting in 21% and 49%

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Nylon is a term representing certain types of thermoplastic polymers belonging to the family known as polyamides. The term nylon, derived from a combination of New York and London, was suggested by Wallace Carothers, an early researcher of these materials at Du Pont Chemical Co. of America in 1928, who found that a pound of nylon could be converted to a length equal to the distance between New York (NY) and London (LON) [1,2]. A wide range of polyamides have been manufactured and marketed under various trade names. Their names can be classified into two types, i.e., nylon

Methods

Results

Conclusion