Recycling high-performance glass fibers from waste wind turbine blades via an acetic acid/nitric acid system.

The three-dimensional crosslinking network and irreversible curing characteristics of thermosetting epoxy resins pose significant challenges to the efficient recycling of waste wind turbine blades (WWTBs) under mild conditions. In this paper, a mild chemical method using an acetic acid/nitric acid system is proposed for the recycle of high-performance glass fibers from the WWTBs. Specifically, the WWTBs are first subjected to the swelling pretreatment in acetic acid at 80 ℃ to induce the volume expansion and delamination of their dense structures. Then, using nitric acid as the degradation agent, a depolymerization reaction of 2 h is carried out on the swollen WWTBs at 160 ℃. The results demonstrate that the glass fibers are successfully separated from the WWTBs, and the degradation ratio of the epoxy resin reaches 91.7 %. During the degradation process, the C-N bonds with lower bond energies in the epoxy resin are selectively cleaved while the benzene rings and other carbon skeleton structures remain intact. The surface of the recycled glass fibers is clean and smooth, and the content of the O and Si elements are comparable to those of the virgin glass fibers. Moreover, the tensile strength of the recycled glass fibers decreases by 6.5 % compared with the virgin glass fibers, which indicates that their mechanical properties are well retained. This study provides a feasible strategy for recycling high-performance glass fibers from the WWTBs under mild conditions.