In Situ WAXD and SAXS during Tensile Deformation Of Moulded and Sintered Polyamide 12.

Fabio Paolucci,Gerrit Peters,Leon Govaert

doi:10.3390/polym11061001

Fabio Paolucci, Gerrit Peters + Show 1 more

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https://doi.org/10.3390/polym11061001

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Abstract

To provide knowledge to improve the mechanical performance of Polyamide 12 (PA12) sintered products, we have studied experimentally the mechanical response and structure development under constant strain rate of compression moulded and laser sintered PA12 by means of in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) experiments. It is found that at low temperatures, i.e., below the glass transition temperature, the brittle failure of laser sintered samples is determined by the fast formation of voids that originate at the beginning of the macroscopic plastic deformation. This effect appears to be faster at temperatures below room temperature and it is less effective at higher temperatures. When tested at 120 C, sintered PA12 shows a better mechanical response in terms of yield stress and a comparable strain at break with respect to moulded PA12. This can be explained by considering that sintered samples have slightly thicker crystals that can sustain higher stress at high temperature. However, this also leads to the formation of a larger number of voids at low testing temperatures. This work does not attempt to quantify the micromechanics behind crystals deformation and disruption, but it provides a deeper insight in the difference between the mechanical response of moulded and sintered PA12.

Highlights

Thanks to their low density and high specific strength, polymers are used in every field of application these days
In our previous work [19], we have demonstrated that yield kinetics of moulded and sintered Polyamide 12 (PA12) is comparable at temperatures above the glass transition temperature (Tg) where intra-lamellar deformation processes are predominant
As we have already demonstrated in our previous work [19], the difference in the yield kinetics becomes larger at low temperature and high strain rates where inter-lamellar deformations are known to contribute more to the yield stress

Summary

Introduction

Thanks to their low density and high specific strength, polymers are used in every field of application these days. In many cases, they are subjected to very demanding conditions such as high applied stress, constant and/or dynamic, and environmental conditions such as high temperature and humidity. In order to prevent premature failure, understanding the mechanism behind failure is of the utmost importance. We focus on the failure mechanism of laser sintered Polyamide 12 (PA12). Subjected to a constant strain rate and the results are compared to those obtained from compression moulded PA12. PA12 has been widely used as starting material for Selective Laser

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