Mechanical, morphological, and dimensional properties of heat-treated fused deposition modeling printed polymeric matrix of polyethylene terephthalate glycol

Abstract

This study investigates the impact of heat treatment on the mechanical, morphological, and dimensional properties of polyethylene terephthalate glycol (PETG), a commonly used thermoplastic in 3D printing. Taguchi L25 orthogonal array (OA) was employed to optimize 3D printing parameters, considering factors such as infill percentage (ranging from 20% to 100%), layer height (0.12 mm to 0.28 mm), layer width (0.32 mm to 0.62 mm), and infill pattern. Following ASTM D638 type IV standards, mechanical testing revealed that the optimal printing conditions included a 100% infill percentage, a layer height of 0.16 mm, a layer width of 0.32 mm, and an infill pattern of 5. Specimen 22, produced under these conditions, exhibited a notable stress-bearing capacity of 46.43 ± 1.394 MPa. These results are consistent with previous studies that underscored the significance of high infill percentages and finer layer dimensions in enhancing tensile properties. Subsequently, these optimized specimens were exposed to various heat treatment conditions. It was discovered that heat treatment at 85°C for 15 min yielded the most significant improvements, increasing the stress-bearing capacity to 53.462 ± 1.604 MPa, representing an impressive ∼16% enhancement compared to non-heat-treated specimens. However, this treatment also led to increased brittleness. Morphological analysis using Scanning Electron Microscopy (SEM) further substantiated the findings. Specimens subjected to heat treatment at 85°C exhibited fewer voids and porosities than those printed with lower infill percentages and larger layer dimensions. These observations underscored the importance of adequate infill density and finer printing details for optimizing strength. Regarding dimensional stability, dimensional changes were meticulously measured after heat treatment. Notably, specimens subjected to heat treatment at or near the glass transition temperature (Tg) of PETG experienced the most significant shrinkage. Specimen 6, treated at 85°C, displayed the highest shrinkage, with length and width reductions of 133.30 ± 3.85 mm and 25.90 ± 0.87 mm, respectively.