Preparation of high molecular weight thermoplastic bio-based phenolic resin and fiber based on lignin liquefaction

Abstract

In order to improve the application range of lignin phenolic resin, lignin thermoplastic phenolic resin was prepared by controlling the molar ratio (formaldehyde: phenol) with liquefied lignin, phenol and formaldehyde as raw materials, and thermoplastic phenolic fiber was obtained by melt spinning. The effects of different curing bath acid proportion (40%, 50%, 60%) on the mechanical property, thermal property and morphology of the fiber were investigated, and the curing behavior of lignin phenolic fiber was studied. The structure and properties of the resin and fiber were characterized by FT-IR, NMR, GPC, TG, DSC, XRD, SEM and fiber strength testing. The results showed that when the molar ratio was 0.7:1, the resin had the best performance, the O/P value was 1.75, Mw was 8298, and PDI was 2.92. After curing, the fiber continued cross-linking reaction, and the diameter of the cured fiber was thicker than that of the original fiber. The most suitable curing process for the original fiber was that formaldehyde and hydrochloric acid were prepared into curing bath according to the mass ratio of 1:1, the heating rate was 20 ℃ h−1, the curing termination temperature was 170 ℃. The tensile strength of the fibers reached 176.64 MPa and the elongation at break was 1.48%, and finally the carbon yield at 800 ℃ was 37.2%.