All‐aramid composites by partial fiber dissolution in mixed solvents

A new self‐reinforced polymer composite based on high‐performance aramid fibers was successfully prepared by applying an elaborately designed surface‐dissolution method to fuse poly(p‐phenylene terephthalamide) (PPTA) fibers and consolidate them into “all‐aramid” composites. A mixture of phosphoric acid (H₃PO₄) and sulfuric acid (H₂SO₄) was selected as a milder alternative to highly concentrated sulfuric acid which was used in our previous study. This milder solvent requires longer immersion times to partially dissolve PPTA fiber surfaces, therefore a more controllable consolidation process to create all‐aramid composites. After selection of the optimal H₃PO₄/H₂SO₄ concentration, PPTA fibers were immersed in the mixed solvent for selected periods of time to partially dissolve PPTA fiber surfaces and convert them into the matrix phase which is needed to fuse the remaining PPTA fiber cores together. Following extraction of the mixed solvent and drying, a consolidated all‐aramid composite was formed. The structure, mechanical‐, and thermal properties of these all‐aramid composites were investigated and reported. Based on high temperature performance of aramid fiber, these all‐aramid composites are promising candidates for high temperature applications. POLYM. COMPOS., 39:3013–3021, 2018. © 2017 Society of Plastics Engineers