Fire Behavior of Polyamide 12/Rubber Formulations Made by Laser Sintering.

Marcos Batistella,Monica Francesca Pucci,Arnaud Regazzi,Ouassila Kadri,David Bordeaux,José-Marie Lopez-Cuesta,Florence Ayme

doi:10.3390/ma15051773

Marcos Batistella, Monica Francesca Pucci + Show 5 more

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https://doi.org/10.3390/ma15051773

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Abstract

In the present work, the processability and fire behavior of parts made by the laser sintering (LS) of polyamide 12/rubber powder blends is studied. In order to evaluate some of the interactions that could take place during LS, three acrylonitrile butadiene rubbers (NBRs) were used, which included two that had different acrylonitrile (AN) contents, and one that had carboxylated rubber. The results show that the flowability of the powders is strongly dependent on the rubber used. For the carboxylated rubber, a good flowability of the blend was observed, whereas the use of rubbers with different AN contents led to significant changes in the powder flowability, with a heterogeneous powder bed, and differences in the porosity as a function of the AN content. Furthermore, the addition of rubbers to polyamide 12 (PA12) entails an increase in the sintering window and, in particular, a change in the melting temperature of PA12 is noticed. Even though some changes in the crystallization and melting temperatures are observed, formulations containing 10 and 20 wt.% of rubbers could be processed using the same process parameters as PA12. Furthermore, the formulations containing carboxylated rubber show improved fire behavior, which is measured by a cone calorimeter, with reductions of about 45 and 65% in the peak of the heat release rate, compared to the PA12. Moreover, almost all of the samples evaluated in this study are classed as “Good” by the Flame Retardancy Index. This result can be partially explained by the formation of an amide linkage between the polyamide and NBR during processing, which could result in increases in the melt viscosities of these samples.

Highlights

Additive manufacturing (AM) is attracting attention in various industrial applications because of its freedom in terms of the part geometry, as well as the rapidity in the production of prototypes
Powder bed fusion (PBF) technologies are increasing its range of applications because of its greater freedom of part geometry, and the new materials that are currently available or under development [1]
The addition of these materials aims to improve the final properties of polyamide 12 (PA12), which is needed for most applications, such as in the aerospace industry

Summary

Introduction

Additive manufacturing (AM) is attracting attention in various industrial applications because of its freedom in terms of the part geometry, as well as the rapidity in the production of prototypes. The use of additives could have a negative effect on the processability of these blends because of the poorer flowability and, in some cases, the alteration of the laser/polymer interaction, which can strongly limit the sintering of the parts. Another way to improve the material properties is to use polymer blends. The addition of PC led to a decrease in the porosity as a function of the PC content These few results show that polymers should be selected carefully in order to obtain fully dense parts in LS that could be suitable for technical applications. The use of some polymer blends may be interesting because of the chemical interactions that can occur between polymers during LS, which leads to some improvements in the part properties without previous processing, such as the extrusion in [8]

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