Surface modification of PLA nets intended for agricultural applications

Abstract

Exclusion nets create a physical barrier between pests and crops, serving as a practical tool to reduce pesticide use in a wide variety of crops, and their negative impacts on the environment. While the efficiency of this method has been recently assessed, protection from pests is incomplete, as microorganisms such as fungi are not hindered by netting. In order to avoid favorable conditions for microbial development (e.g. wet leaf surfaces), the present study discusses two hydrophobic surface treatment approaches, each applied to two PLA substrates that can be used as exclusion nets to reduce water ingress on protected fruit trees. Both a commercial exclusion net and a fused deposition modelled (or 3D printed) mesh were treated via solvent-free and solvent-induced modifications. Photo-initiated chemical vapor deposition (PICVD) allowed organic thin film growth on the substrate at near-ambient conditions. Dip-dip-dry (DDD) exploited solvent-induced topology modification to yield hydrophobic PLA samples, showing various microstructures (crazes or hierarchical topology) depending on the substrate properties. Both substrates were efficiently rendered hydrophobic after surface treatments, with water contact angles climbing from 73° to 101° (PICVD) or 143° (DDD) for printed PLA samples, and to 131° (PICVD) or 135° (DDD) for commercial exclusion nets. The hierarchical features present on DDD-treated printed PLA substrates showed potential for molecular adsorption, paving the way for a method to increase the phytosanitary effect of agricultural textiles by active ingredient incorporation (limonene is used here as a test case). Surface properties were characterized with SEM imaging, contact angle measurements, tensile tests and drop penetration assessments (rain simulation).