Desenvolvimento de polímero termoplástico de glicerina para aplicação na manufatura aditiva por extrusão de material

Abstract

Recent environmental issues provide growing interest in replacing diesel fossil with biodiesel. However, the production of the biofuel leads to an inherent surplus of the co-product glycerine resulting in several problems. This context drives researchers to search new forms of this co-product employment, mainly as a raw material in the development of new materials as polymers. Nevertheless, no investigations were found with the aim of developing a polymer based on glycerol and suitable for application to the material extrusion additive manufacturing (AM) technologies. This research proposes a polymer synthesis that besides being thermoplastic, it also fulfil some basic requirements for this specific application. The major challenge is to obtain a thermoplastic polymer from glycerine, defined as a poly functional monomer that generally originates thermosetting polymers. In order to achieve the proposed objectives, initially several preliminary syntheses were carried out in test tubes. After FTIR (Fourier transformed infrared) and TGA (thermo gravimetric analyses), only one experiment, containing glycerine (GL) and phthalic anhydride (FA), executed at 180 ° C and 48 hours reaction, resulted in a suitable polymer for the application. From these initial results, larger volumes of polymer were synthesized, also considering the use of mechanical agitation. These syntheses provided reaction time reduction from 48 to about 5 hours and originated two thermoplastic polymers. The former, containing only glycerine (GL) and phthalic anhydride (AF from the Portuguese anidrido ftálico) and named by GLAF, presented glass transition temperature (Tg) values near to 17 °C. The later, containing also stearic acid (AE from the Portuguese ácido esteárico) and denominated by GLAFAE, resulted in Tg values close to 49 °C. XRD (X-Ray diffraction) characterization indicated that the GLAFAE polymer has a total amorphous structure. Tensile analysis tests demonstrated better ultimate strength results for the GLAFAE polymer compared to the GLAF. However, the modulus of elasticity presented similar results to both. It should be noted, however, that such mechanical properties presented an order of magnitude lower than values found for commercial polymers used in the material extrusion AM technology. Previous application evaluations, using heated syringe, demonstrated the possibility of extrusion, deposition and adhesion between adjacent filaments. Previous evaluations using a heated syringe demonstrated the possibility of extrusion, deposition and adhesion between adjacent filaments. Final assessments, using a 3D printer specifically constructed for this research, allowed to obtain single-layer and multilayer specimens. However, specimens printed with the GLAFAE polymer showed better results. As conclusion, this research demonstrated the possibility of synthesizing a basilar thermoplastic polymer with glycerine suitable for application in the AM process based on material extrusion principle. Although, additional research are necessary to improve characteristics as Tg and ultimate strength as to approach these values to those found for the commercial polymer available.