Adhesion enhancement of electrospun nanofiber mats to polypropylene nonwoven fabric by low-temperature oxygen plasma treatment

In this work, adhesion of different nanofiber mats to a polypropylene nonwoven was studied. In particular, low-temperature oxygen plasma treatment was investigated as a potential interface engineering tool to use for enhancing adhesion between polypropylene nonwoven and nanofibers. Poly(ethylene oxide) (PEO) and polyamide-6 (PA6) nanofibrous mats were deposited onto a polypropylene nonwoven, both untreated and plasma-treated, by single-jet solution electrospinning, using the same process parameters (with the exception of flow rate) identified to be effective for coating the substrate with almost defect-free nanofiber mats. Electrospun PA6 nanofibers were finer (diameters lower than 300 nm) than PEO ones (mean diameter about 450 nm); consequently, webs in which nanofibers got closer to each other and formed smaller pores were produced with PA6, this implies that the final air permeability of the multilayered material formed by the nonwoven and the nanofibrous mat was lower when using PA6 than when using PEO (about 50 lm-2 s-1 for PA6 nanofiber-coated substrate and about 120 lm-2 s-1 for PEO nanofiber-coated one). The coated area of the nonwoven substrate by nanofiber coating was larger when PA6 was used (about 100 cm2), while smaller coatings were obtained using PEO (coated area about 50 cm2). All these properties were not influenced by the plasma treatment. On the contrary, the adhesion of nanofibermats to polypropylene nonwoven, characterized by means of a customized 180° peeling test,was drastically enhanced by oxygen plasma treatment. In particular, PEO nanofibrousmatswere proved to adhere to treated polypropylene substrate better than PA6 ones.Mean adhesion energy between untreated polypropylene nonwoven and nanofiber mat was 0.58 and 0.39 J/m2 for PEO and PA6 nanofibers, respectively. After the plasma treatment of the substrate, the values significantly increased to 4.80 J/m2 for PEO nanofibers, and to 0.89 J/m2 for PA6 ones.