Synthetic polymer (epoxy)-lignin polyblends as structural adhesives.

摘要

Synthetic polymer (Epoxy) - Lignin polyblends as structural adhesives with significantly improved adhesive properties, durability and cost advantages have been developed by an effective and economical blending technique as an alternative approach to the current chemical synthetic methods. This research project is also of great significance in cultivating a market for lignin, a highly underutilized waste and byproduct of the pulp and paper industry which also affects the cleanness of the environment.;Some important factors (curing temperature, lignin content and others) which influence the adhesive joint shear strength of Epoxy-Lignin adhesives and the influence of different types of lignin (various sources), epoxy systems, fillers, third polymeric components and organofunctional silane coupling agents have been studied.;As a novel adhesive, its surface energy parameters (contact angle, surface free energy, interfacial free energy, speading coefficient, Girifalco-Good's interaction parameter and work of adhesion) have been experimentally determined. A direct correlation between the obtained surface thermodynamic parameters and the determined adhesive joint shear strength has been established.;Differential scanning calorimetry, Dynamic mechanical analysis and Nuclear magnetic resonance techniques were performed on EP-L polyblends; they clearly demonstrate that thermally cured Epoxy-Lignin polyblends with up to 20% lignin are miscible systems. Research techniques, including FTIR, titration, kinetics, extraction, and UV spectroscopy, demonstrate that lignin chemically reacted with the epoxy-polyamine network via unreacted amine groups of the hardener during the thermal cure of epoxy-lignin polyblends. These findings not only reveal the morphology feature and chemical interaction mechanism of these new EP-L polyblends, but also emphasize their value of application in various material fields such as adhesives, coatings, structural plastics, composites, mortars and injection resins.