Accelerated Aging Effect on Mechanical Properties of Common 3D-Printing Polymers

Abstract

In outdoor environments, the action of the Sun through its ultraviolet radiation has a degrading effect on most materials, with polymers being among those affected. In the past few years, 3D printing has seen an increased usage in fabricating parts for functional applications, including parts destined for outdoor use. This paper analyzes the effect of accelerated aging through prolonged exposure to UV-B on the mechanical properties of parts 3D printed from the commonly used polymers polylactic acid (PLA) and polyethylene terephthalate–glycol (PETG). Samples 3D printed from these materials went through a dry 24 h UV-B exposure aging treatment and were then tested against a control group for changes in mechanical properties. Both the tensile and compressive strengths were determined, as well as changes in material creep characteristics. After irradiation, PLA and PETG parts saw significant decreases in both tensile strength (PLA: −5.3%; PETG: −36%) and compression strength (PLA: −6.3%; PETG: −38.3%). Part stiffness did not change significantly following the UV-B exposure and creep behavior was closely connected to the decrease in mechanical properties. A scanning electron microscopy (SEM) fractographic analysis was carried out to better understand the failure mechanism and material structural changes in tensile loaded, accelerated aged parts.

From Virtual Reconstruction to Additive Manufacturing: Application of Advanced Technologies for the Integration of a 17th-Century Wooden Ciborium

“…However, due to certain disadvantages of PLA, such as its high sensitivity to temperature, easy degradability (3–6 months depending on the environmental conditions, size and filling of the object) and hygroscopicity [ 21 , 30 ], a thermoplastic polymer derived from the polyethylene terephthalate family such as polyethylene terephthalate glycol (PETG) is often used. It is well known that exposure to specific conditions of temperature, humidity, ultraviolet radiation and chemicals causes ageing of polymers, resulting in chemical degradation and/or photodegradation [ 4 , 9 , 32 , 33 ]. The scientific literature includes many studies on the ageing of PLA and PETG under different atmospheric and chemical conditions [ 9 , 33 , 34 , 35 ], whereas studies of accelerated ageing and degradation of 3D printed parts in the same polymeric materials are more limited [ 33 , 35 ].…”

“…The scientific literature includes many studies on the ageing of PLA and PETG under different atmospheric and chemical conditions [ 9 , 33 , 34 , 35 ], whereas studies of accelerated ageing and degradation of 3D printed parts in the same polymeric materials are more limited [ 33 , 35 ]. Furthermore, it must also be considered that printed samples do not always behave like the original raw materials, but more like new systems, with porosity and anisotropic properties [ 32 , 35 ]. For example, Moraczewski et al (2019) [ 34 ] analyzed the effect of accelerated ageing of PLA blends (720, 1440 or 2160 h, 45 °C, 70% relative humidity, in the presence of continuous UV radiation and comparing the results obtained with a commercially available anti-ageing compound), and showed a significant reduction in mechanical properties (e.g., a worse decrease of 17 MPa in tensile strength compared to the unaged sample) [ 34 ].…”

Colorimetric evaluation of 3D printing polymers exposed to accelerated aging for Cultural Heritage applications

“…Because of this, accelerated aging is one of the main techniques to assess the changes produced in a specific material when exposed to different ambient conditions. 37,38 This way, color and glossiness are optical properties that may determine the selection of a certain material for cultural heritage, as these alterations indicate other chemical degradation taking place in the material. Likewise, from a durability point of view, a material with low color modification may be more suitable for restoration or artistic creation purposes.…”

Mechanical properties of 3D printed parts: Effect of ultraviolet PLA filaments ageing and water absorption

“…Some researchers studied the ageing to UV of parts 3D printed. [23][24][25][26] The degradation of filaments decreases the molecular weight and the compatibility with wood; moreover, they increase the water absorption of the filament. The work doesn't consider the effect of the alteration of the chemical and thermal properties of the PLA filament on printing parameters.…”