Reaction kinetics and curing behavior of epoxies for use in a combined selective laser beam melting process of polymers

Abstract

ABSTRACTSelective laser beam melting also known as selective laser sintering (SLS) of polymers is an additive manufacturing process, which enables the production of functional components. Additive manufacturing has its strength in areas where conventional manufacturing methods, such as injection molding, reach their limitations. Unfortunately, the SLS process is restricted regarding the materials that can be processed. This work clears the ground for multimaterial SLS parts, locally reinforced with thermosets. To introduce thermoset resins into the SLS process, the time–temperature curing of the resins have to be understood in order to assess the process behavior. The time–temperature behavior of the used resins is of main importance because of high temperature in the building chamber during laser sintering and long build time up to hours. For Polyamide 12, a standard material in SLS, the building chamber temperature is approximately 170 °C. Therefore, the used resin has to show a specific curing behavior at the building chamber temperature in SLS. Two epoxies, Araldite GY 764 and Araldite GY 793, are analyzed using isothermal and nonisothermal differential scanning calorimetry (DSC) in order to determine whether these resins can be used in SLS or not. Different approaches to model the curing behavior are applied, including the Kissinger method, the Ozawa–Flynn–Wall analysis, and the DiBenedetto equation. The curing behavior of the analyzed resins were finally compared to temperature profiles during SLS to estimate the curing behavior of these systems in SLS. At a medium building chamber temperature of 160 °C, both thermosets show a suitable curing behavior, because of a degree of cure that ranges between 0.15 and approximately 0.6 for 2 up to 10 min. Thus, the curing reaction starts after applying the resin on the powder bed surface and reaches a higher level after approximately 10 layers, assuming a layer time of 1 min. © 2018 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46850.