The use of synthetic and natural fibers in epoxy coatings: A comparative mechanical and economic analysis

This article describes the comparative analysis of the results of the pull-off strength and ultrasonic tests of two coatings modified with synthetic (polypropylene) fibers and natural (coconut) fibers reported previously in details in the authors previous works. The analyzed substrates were made of cement paste and cement mortar. The analyzed ratio of fibers ranged from 0.5% to 2% in relation to the weight of the epoxy resin. A results of pull-off strength and ultrasonic testing obtained for coating modified with fibers and reference coatings without the addition of fibers were analyzed. The performed comparative analysis shows that the highest pull-off strength values in the case of the cement paste substrate model composite systems were equal to 3.30 ± 0.38 MPa for synthetic fibers and 2.84 ± 0.59 MPa for natural fibers. Both results were observed when adding 1% of the fibers to the epoxy resin. In turn, the pull-off strength of the reference coating was observed to be equal to 1.40 ± 0.35 MPa. On the substrate made of cement mortar, the analyzed values pull-off strengths were higher, and equal to 3.93 ± 0.58 MPa in the case of adding 1% of synthetic fibers, and 3.48 ± 0.43 MPa when adding 0.5% of natural fibers. The reference coating of the substrate made of cement mortar obtained a result of 3.33 ± 0.51 MPa. In both cases, the addition of fibers in amounts of more than 1% caused a significant reduction in pull-off strength. Finally, the economic analysis performed for the cement mortar substrates indicated that the use of fibers allows for the obtaining of an increased pull-off strength at almost the same coating costs. The increase in strength reaches 18% for synthetic fibers, and 5% for natural fibers (with a slight increase in costs by 1%).