Epoxyorganosilane Finishing Compositions for Fibrous Fillers of Thermosetting and Thermoplastic Binders

The development of universal finishing compositions for fibers of various natures is an urgent task for polymer composite materials science. The developed finishes can be used for the fiber reinforcement of polymer matrices with a wide range of surface free energy characteristics. Epoxy systems modified with diaminesilane in a wide concentration range were examined by optical interferometry, FTIR spectroscopy, DSC and the sessile drop technique. It was shown that the partial curing of epoxy resin by diaminesilane at room temperature under an inert atmosphere, followed by contact with air, leads to a significant increase of the surface free energy of the system. Varying the concentration of diaminesilane allows us to effectively regulate the surface free energy of the composition. This makes it possible to use fibers finished with epoxyaminosilane compositions in composite materials based on a various thermosetting and thermoplastic binders with a surface tension of up to 75 mJ/m2.

Studies on the Modification of Commercial Bisphenol-A-Based Epoxy Resin Using Different Multifunctional Epoxy Systems

The tensile fracture mechanics and thermo-mechanical properties of mixtures composed of two kinds of epoxy resins of different chemical structures and functional groups were studied. The base resin was a bi-functional epoxy resin based on diglycidyl ether of bisphenol-A (DGEBA) and the other resins were (a) distilled triglycidylether of meta-amino phenol (b) 1, 6–naphthalene di epoxy and (c) fluorene di epoxy. This research shows that a small number of multifunctional epoxy systems, both di- and tri-functional, can significantly increase tensile strength (14%) over neat DGEBA while having no negative impact on other mechanical properties including glass transition temperature and elastic modulus. In fact, when compared to unmodified DGEBA, the tri-functional epoxy shows a slight increase (5%) in glass transition temperature at 10 wt.% concentration. The enhanced crosslinking of DGEBA (90 wt.%)/distilled triglycidylether of meta-amino phenol (10 wt.%) blends may be the possible reason for the improved glass transition. Finally, the influence of strain rate, temperature and moisture were investigated for both the neat DGEBA and the best performing modified system. The neat DGEBA was steadily outperformed by its modified counterpart in every condition.

Reinforcement of Epoxy Resin by Lignin

Diglycidyl ether of bisphenol A (DGEBA) epoxy resin with cycloaliphatic polyamine curing agent was modified with lignin to improve thermal and mechanical properties of of polymer composite. A systematic study of lignin loading, between 5 and 20 phr (per hundred parts resin) as compared to neat epoxy, was conducted for the reinforcement effect of epoxy resin composites. With the as-received lignin having spherical particles of 80 to 100 microns in diameter, the Tg of the epoxy-filler composites increased with a small addition of lignin up to 10 phr. Likewise, the yield stress and stiffness (Young’s modulus) of the epoxy resin-lignin composites significantly increased to a maximum value of 49.32 MPa and 2.75 GPa, respectively, with 10 phr lignin, due to the higher modulus of the filler compared to the bulk epoxy resin. Correspondingly, the storage moduli of the lignin-containing composites also increased upon filler addition up to 10 phr due to the impact of lignin. Conversely, however, the tanδ decreased in intensity with increasing lignin filler content, which reflects the dampening effect due to restricted chain mobility in thepresence of lignin particlesin epoxy systems.