Epoxy–lignin polyblends: Correlation between polymer interaction and curing temperature

Abstract

A bisphenol A-polyamine hardener based epoxy adhesive ( E P ) was modified by polyblending with Kraft lignin ( L ) . EP-L polyblends with an L content up to 40% by weight were cured at room temperature or above their glass transition temperature ( T,) . Previous data have shown that the thermal and viscoelastic properties, as well as adhesive performance of the EP-L polyblends, are influenced by the curing temperature and by the L content in thermally cured polyblends. A reasonable explanation for the different behavior of EP-L polyblends as function of the curing temperature and their L content could be the enhanced degree of bonding between L and the E P network taking place at elevated temperature. This bonding was specifically considered to take place between L and possible unreacted amine groups of the hardener. Characterization of the EP-L polyblends was performed to search for evidence of irreversible chemical bonding between L and the E P network in thermally cured EP-L polyblends. FTIR studies, L extractibility from the crosslinked polyblends, and quantitative data concerning the reactivity of L toward the polyamine hardener are discussed.

Epoxy-lignin polyblends: effects of various components on adhesive properties

“…simply blending the liquid EP prepolymer, hardener, and lignin powder at room temperature. Previous data [5,6] have shown an increased adhesive performance of a bisphenol A-polyamine EP adhesive modified by polyblending with kraft lignin. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and nuclear magnetic resonance (NMR) techniques showed that thermally cured blends with up to 20% lignin are miscible systems.…”

“…The working procedure has been described in previous work [5]. The molecular weight distributions of the unfractionated TO and its three fractions were obtained by GPC (Fig.…”

“…The FTIR spectra clearly indicate the chemical reaction between lignin and the epoxy-polyamine network under thermal curing conditions of EP-L blends through their carbonyl groups in lignin and amine groups in the hardener [5].…”

Chemistry of lignin-based materials

“…Because of the less complex chemistry, simple direct polymer blend with lignin, epoxy group-containing chemicals and curing agents, for example, amine containing reagents -were commonly studied. [161][162][163][164][165][166][167][168] Lignin-based epoxy resin mostly investigated its thermal properties, mechanical properties and morphological characters with scanning electron microscopy (SEM).…”

Biocomposites and Nanocomposites Containing Lignin

“…Functionalization of lignin by hydroxyalkylation or phenolation, followed by reaction with epichlorohydrin, allowed epoxy-functional lignins to be obtained, which may be cured with diamines or anhydrides [95,115,116].…”