Article
Version 1
Preserved in Portico This version is not peer-reviewed
Hygroscopicity in Epoxy Powder Composites
Version 1
: Received: 31 December 2023 / Approved: 18 January 2024 / Online: 23 January 2024 (01:50:20 CET)
A peer-reviewed article of this Preprint also exists.
Maguire, J.M.; Wang, J.-Y.; Ó Brádaigh, C.M. Hygroscopicity in Epoxy Powder Composites. Powders 2024, 3, 168-189. Maguire, J.M.; Wang, J.-Y.; Ó Brádaigh, C.M. Hygroscopicity in Epoxy Powder Composites. Powders 2024, 3, 168-189.
Abstract
Epoxy powders offer a low-cost means of manufacturing thick section composite parts, such as those found in wind and tidal turbines. Currently, their processing cycle includes a lengthy drying stage (≥ 15 h) to remove ambient moisture. This prevents void defect formation and, thereby, a reduction in mechanical properties, however, it constitutes up to 60% of the processing time. Little research has been published on the study of this process or its optimisation. Experimental and simulated analyses are used to investigate the effects of hygroscopicity in epoxy powder composites. In particular, focus is given to the drying process, which is used to prevent void defect formation and, thereby, a reduction in mechanical properties. As such, tests are performed to quantify the void content of dried and undried laminates, and to measure its impact on transverse flexural strength. Dynamic vapour sorption analysis is used to study the sorption behaviour of the epoxy powder. Sorption data is fitted to a modified linear driving force model, and then implemented in existing process simulations tools. The drying of a thick epoxy powder composite section is simulated to investigate the influence of powder sintering on the duration required for drying. It is shown that the epoxy powder is slightly hygroscopic (1.36 wt%) and exhibits sorption behaviour that is characteristic of glassy polymers. This results in up to 4.8% voids (by volume) if processed in an undried state, leading to a 43% reduction in transverse flexural strength. Process simulations reveal that a standard drying cycle prematurely sinters the powder; inhibiting moisture release. By maintaining a powder state, simulations show that the drying cycle can be reduced to 5 h.
Keywords
hygroscopicity; epoxy powder; polymer composites; drying; sintering
Subject
Engineering, Mechanical Engineering
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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