Modification of poly(lactic acid) filament with expandable graphite for additive manufacturing using fused filament fabrication (FFF): effect on thermal and mechanical properties

João Miguel Ayres Melillo,Fernando Gabriel Da Silva Araujo,Artur Caron Mottin,Iaci Miranda Pereira

doi:10.1590/0104-1428.20210013

Abstract

Abstract Fused Filament Fabrication, better known as Fused Deposition Modeling®, is currently the most widespread 3D Printing Technology. There has been a significant demand for developing flame-retardant filaments. Thereby enabling them, for example, in electronics and automotive applications. In this study, commercial PLA filament was modified by the addition of 1, 3 and 5% (%wt.) of expandable graphite. The composites were reprocessed, via extrusion, into filaments for Fused Filament Fabrication. Thermal properties of the filament composites were evaluated by thermogravimetric analysis and differential scanning calorimetry. Mechanical properties of thermo-pressed specimens indicated that no strong adhesion was promoted between the filler and matrix. This is a challenge with expandable graphite reported by many authors. All composites with expandable graphite achieved the V-2 rating of UL-94 flammability test. In spite of this, the results indicated that flammability of the PLA was reduced. All composite filaments were printable and prototypes were successfully 3D printed.

Highlights

Additive manufacturing (AM) alludes to adding raw materials during manufacturing, and includes several assembly and rapid prototyping processes[1]
When expandable graphite (EG) is exposed to high temperature, it expands due to releasing of gaseous products
Composite filaments based on poly(lactic acid) (PLA) and 1, 3 and 5 wt.% of EG were developed for using in fused filament fabrication (FFF)-type 3D printing

Summary

Introduction

Additive manufacturing (AM) alludes to adding raw materials during manufacturing, and includes several assembly and rapid prototyping processes[1]. The most used thermoplastic polymers in FFF-type 3D printing are acrylonitrile butadiene styrene (ABS), poly(lactic acid) (PLA), high impact polystyrene (HIPS), thermoplastic polyurethane (TPU) and aliphatic polyamides (nylon)[5]. PLA is a biobased polymer, that is, PLA is obtained from natural and sustainable raw material, such as cornstarch. It degrades in soil by microorganisms under certain conditions of temperature and humidity[6]. In addition to these ecological benefits, PLA offers reasonable performance in technical applications related to its mechanical properties[6]. Xue et al [9] developed a flame retardant poly(lactic acid) (PLA) composite with the addition of only 2 wt% of ammonium polyphosphate (APP)

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Results

Conclusion