Melt-Spun Poly(D,L-lactic acid) Monofilaments Containing N,N-Diethyl-3-methylbenzamide as Mosquito Repellent

Malaria is still a major tropical disease, with Africa particularly burdened. It has been proposed that outdoor protection could aid substantially in reducing the malaria incidence rate in rural African communities. Recently, melt-spun polyolefin fibers containing mosquito repellents have been shown to be promising materials to this end. In this study, the incorporation of N,N‑Diethyl‑3‑methylbenzamide (DEET)—a popular and widely available mosquito repellent—in commercially available, amorphous poly(D,L-lactic acid) (PDLLA) is investigated with the aim of producing biodegradable mosquito-repelling filaments with a reduced environmental impact. It is shown to be possible to produce macroscopically stable PDLLA-DEET compounds containing up to 20 wt.-% DEET that can be melt-spun to produce filaments, albeit at relatively low take-up speeds. A critical DEET content allows for stress-induced crystallization during the spinning of the otherwise amorphous PDLLA, resulting in the formation of α-crystals. Although the mechanical integrity of the filaments is notably impacted by the incorporation of DEET, these filaments show potential as materials that can be used for Malaria vector control.