A study on moisture absorption and swelling in bio-based jute-epoxy composites

Woven jute fibers, a class of affordable and biodegradable 'green' fibers, are being increasingly used as a substitute for the artificial glass and carbon fibers used in polymer composites. However, all natural fiber composites absorb water and swell in a moist environment. For the first time, the swelling and weight gain behavior of bio-based composites made from jute fibers and bio-based or ordinary epoxy is presented in this experimental characterization study. Several such composites specimens were made using a low-pressure resin injection process similar to resin transfer molding; the specimens were made according to ASTM D 570 consisted of three compositions: pure resin, pure resin with a single jute fabric layer, and pure resin with two jute fabric layers. The effects of number of layers on moisture absorption, thickness swelling, volume swelling, and density were measured as a function of immersion time. It is observed that the moisture diffusion rate into composites increases with an increase in the jute-fiber-to-epoxy ratio. The type of epoxy used as the matrix appeared to have an influence on the moisture absorption percentages of the composites - the study showed that both water absorption and swellings were higher in the bio-epoxy parts compared to the epoxy parts. The swelling of composites was correlated with an increase in diameters of jute fiber in water and possibilities for the appearance of micro-cracks around fibers in composites were discussed. The data on moisture absorption, thickness swelling, and volume swelling of bio-based composites made from woven jute fibers, and bio-based and ordinary epoxies presented in this article will lead to a better understanding of how these composites react in wet environmental conditions.