Kevlar® is among the most prominent high-strength polymers for a use in me-chanically demanding applications, such as personal safety, sport equipment and aircrafts. In many of these applications Kevlar is exposed to UV radiation and/or moisture, which seriously affect its mechanical properties. Thus, strengthening or protection of Kevlar is of great interest. So far, the most efficient approaches resulted in heavy and rigid composite materials consisting of Kevlar fibers em-bedded in a resin –.
Kevlar´s outstanding strength arises from the highly ordered crystalline struc-ture formed during the extrusion of the polymer. Astonishingly, little attention has been paid to the possibility of enhancing the mechanical properties and sta-bility via chemical post-processing of the polymer. In our previous work , we demonstrated that the thermal and UV sensitivity of Kevlar can be suppressed by infiltration of ZnO through Multiple Pulsed Infiltration (MPI). However, still only 90% of the modulus of toughness was retained in this way.
In this work, we present an extraordinary improvement of the properties of the fibers after applying a combined ALD/MPI process. Kevlar fibers have been infil-trated with ZnO and coated with Al2O3 in the same process. In this way, not only the loss of the modulus of toughness was suppressed, but the fibers even gained 10% of toughness. Simultaneously its sensitivity to UV-induced degradation was completely eliminated. This new processing strategy is a breakthrough in the improvement of Kevlar and promises further optimization with refinement of the processing conditions and precursors.