Surface Modification of Poly (m-phenylene isophthalamide) Fibers and Its Effect on the Mechanical Properties of Aramid Sheets

In order to improve the bonding properties between poly (m-phenylene isophthalamide) (PMIA) fibers and PMIA-pulp and to improve the mechanical strength of aramid sheets, PMIA fibers have been treated with various chemical modifying agents. The surface morphology of the treated fibers has been analyzed and the mechanical properties of aramid sheets made from the treated PMIA fibers and PMIA-pulp have been investigated. The results show that silane coupling agent modification, phosphoric acid modification and nitrification/reduction modification of PMIA fibers are all helpful for improving the tensile strength and tear strength of aramid sheets, however, they have different effect on the mechanical strength of aramid sheets, and the concentration of chemical modifying agents also has considerable influence on the surface properties of aramid fibers and the mechanical properites of aramid sheets. Aramid handsheets made from PMIA fibers treated with 20% phosphoric acid have the highest mechanical strength, and the tensile strength and tear strength of them are 23.4% and 31.6% higher than that of aramid handsheets made from untreated fibers, respectively, because the treated fiber surface has more oxygenous functional groups and is more rough than the untreated fiber surface.