Exploring the mechanical response of PLA/MWCNT and PLA/HNT composites obtained by additive manufacturing

Purpose: This paper aims to show the mechanical properties of neat polylactic acid (PLA) and PLA with two types of nanoparticles as reinforcement, multi-walled carbon nanotubes (MWCNT) and halloysite nanotubes (HNT) with and without maleinized linseed oil (MLO) as plasticizer, for applications in industrial models and the biomedical field, respectively. Design/methodology/approach: This research evaluates the mechanical response of PLA/MWCNT and PLA/HNT nanocomposites, at concentrations of 0.5 and 1Wt.%, with and without MLO plasticizer at a ratio of 5 phr, which were obtained by melting in a twin-screw extruder. The standardized specimens were manufactured on a Tumaker NX Pro 3D printer with pellets instead of filaments. The studies carried out were tensile and flexural tests, Charpy impact test, microhardness and field emission scanning electron microscope (FESEM). Findings: Tensile tests revealed that neat PLA has a tensile strength of 50.7 MPa, an elastic modulus of 1366.8 MPa and a stretch factor of 6.9%, while the values of MWCNT and HNT nanocomposites without plasticizer are 50% below these figures. The MWCNTs composites with plasticizer increase tensile strength by about 20% over neat PLA, indicating that the nanomaterials with MLO have better mechanical properties due to the plasticizing effect. Neat PLA showed a flexural strength of 93.83 MPa and a flexural modulus of 2657.51 MPa, respectively. The MWCNTs and HNTs composites without plasticizer reveal a 60% and 30% decrease compared to neat PLA, respectively. In comparison, the composites with plasticizer have no more than 10% variation concerning neat PLA. In Charpy impact tests, neat PLA absorbed 19.75 kJ/m² of the energy in the resilience test. At the same time, MWCNTs nanocomposites without plasticizer show a substantial reduction of about 80%, and those with plasticizer absorbed about 15% less energy. HNTs nanocomposites show similar results to those of neat PLA. FESEM shows different nanocomposite fracture types, distributions and miscibility of nanoloads and plasticizer in the polymer matrix. The 20% increase in tensile strength of MWCNTs composites with plasticizer suggests their potential use for applications requiring durability, such as biomedical devices and structural components. In addition, the improved mechanical properties of the nanomaterials, especially MLO, highlight their viability for the development of conductive polymers in flexible electronics and sensors. Originality/value: This study explores the mechanical response of PLA/HNTs and PLA/MWCNTs nanomaterials obtained by 3D printing. It suggests their potential use as biomaterials in the biomedical field, tissue engineering, and industrial polymeric materials.