Fuente: Polymers Polymers, Vol. 18, Pages 164: The Effect of Humidity and UV Light Exposure on the Mechanical Properties of PA6 Matrix Reinforced with Short Carbon Fibers and Built by Additive Manufacturing
Polymers doi: 10.3390/polym18020164
Authors:
Bernardo Reyes-Flores
Jorge Guillermo Díaz-Rodríguez
Efrain Uribe-Beas
Edgar R. López-Mena
Alejandro Guajardo-Cuéllar

This work presents results of nylon-based composites used in additive manufacturing (AM) subjected to 24, 48, 96, 168, 336, and 504 h of continuous exposure to UV and 50% humidity. Sample coupons were built on a Markforged Two® printer. To mimic UV exposure, samples were exposed to 253 nm UV light (UV–C), whereas for humidity, samples were placed at 50% relative humidity and 22 °C in a bi-distilled water atmosphere. The effects of said exposure were measured in tensile, Charpy impact energy, mass absorption, and Shore hardness D tests. Nylon gained 5.6% ± 0.48 mass after 504 h. For Charpy, absorbed energy went down from 0.463 J/mm2 to 0.28 J/mm2 at 504 h of humidity exposure. For Shore D, the variation goes from 59.1 ± 0.82 for zero exposure to 66.8 ± 2.5 at 504 h of UV exposure. Conversely, UV exposure induced an increase in Young’s modulus and Shore hardness, while significantly reducing impact energy to 0.32 J/mm2, indicating embrittlement confirmed by SEM analysis. FTIR analysis revealed hydrolytic degradation under humidity and photo-oxidative degradation under UV, affecting N–H and C=O bonds. These findings allow a designer to project the residual mechanical properties of a component up to its last day of service.