Experimental Investigation on the Effect of Thermal Ageing on Mechanical Characteristics of Polyamide12 Processed Using Selective Laser Sintering

This study investigates the variation in mechanical characteristics of Polyamide-12 (PA-12) specimens on account of thermal ageing. PA-12 has high tensile strength, long life, high chemical resistance, and excellent electrical insulation elements for use in various industrial application including in automotive, aerospace and electronics etc. Test specimens of 150 numbers are fabricated using Selective Laser Sintering (SLS) and exposed to different temperatures and humidity levels. Pre and post structural examinations have been conducted to observe the variation in tensile, compressive, and flexural strength of the material due to thermal ageing. In addition, microstructural studies are done to understand the metallurgical changes in the materials which caused the property changes. Early ageing (1–3 weeks) caused the tensile strength to drop (23.10 to 11.40 MPa) due to chain scission and thermal degradation. Later (4–8 weeks), strength and modulus increased (up to 29.20 MPa and 387 MPa) due to post-crystallization and molecular rearrangement, indicating recovery and stabilization. Flexural strength and modulus increased significantly (32.35 MPa and 647.5 MPa after 8 weeks). Compression strength decreased initially from 68.46 MPa to 45.97 MPa, then recovered up to 67.65 MPa after 8 weeks. Compression modulus increased significantly from 288.25 MPa to 768.65 MPa, reflecting improved modulus with ageing. The effects are dependent on the time of thermal ageing (Environmental effects) and point towards thermal degradation of mechanical properties is observed in fabricated PA-12 upon thermal ageing. Therefore, environmental issues cannot be ignored when contemplating the design of parts produced by Selective Laser Sintering (SLS) printer.