Investigating the annealing effects on the mechanical, morphological and surface properties of 3D printed PETG/OMMT nanoclay composites

Fused Filament Fabrication (FFF) is a highly sought-after manufacturing method that builds parts layer by layer using thermoplastic and/or composite filaments. However, it is characterised by weak interlayer adhesion, resulting in low interlaminar strength in printed structures. Recent research suggests that post-processing heat treatments can address this issue by lowering internal thermal stresses and increasing interlayer bonding, thereby improving part properties. This study investigates the effect of annealing heat treatment on a composite consisting of glycol-modified polyethylene terephthalate (PETG) and organically modified montmorillonite nanoclay (OMMT-NC). The annealing temperature was set at 90°C, and the time duration was varied to 60, 120, and 180 minutes. The mechanical, morphological and surface properties of the OMMT-NC reinforced PETG composite were compared with those of pure PETG. Also, annealing effect on the glass transition temperatures was determined by differential scanning calorimetry (DSC). Atomic Force Microscopy (AFM) was used to investigate the change in surface roughness resulting from annealing. The experimental results show that PETG reinforced with 3 wt.% OMMT nanoclay improved the tensile, compression, flexural, and impact strength by 6.9%, 22.9%, 30.3%, and 87.5%, respectively, after annealing. The hardness also increased across all PETG composites by at least 5%, due to improved interlayer adhesion. Morphological studies were conducted to correlate the deformation behaviour and assess the impact of annealing. The findings of this work indicate that PETG/OMMT-NC composites are a potential candidate for structural applications.