Flame retarded lignin-based epoxy resin with excellent antibacterial and anti-corrosion properties modified by coordinated phospho-nitrogen flame retardant

Abstract

In this paper, epoxidized lignin (HL) and sebacic acid (HSA) were used as the hard and soft segments, respectively, and a kind of reactive coordinated phosphorous-nitrogen flame retardants (DTZ) was designed and synthesized via Zn2+ coordination to fabricate a multifunctional non-bisphenol A lignin based epoxy (EP) composite. The swelling behavior and morphological analysis demonstrated that the crosslinking density of EP increased significantly after adding HL and DTZ. The existence of coordination sacrificial bond of DTZ dissipated more energy when it was subjected to external forces, thereby making 80HSA/14HL/6DTZ maintained a high tensile strength (10.65 MPa) while having little damage to the elongation at break (30.74 %). The limiting oxygen index (LOI) of 80HSA/14HL/6DTZ was significantly higher than that of 100HSA (22.3 %), reaching 36.6 %, and the vertical combustion test (UL-94) reached V-0 level. The morphology of carbon layer and residual carbon analysis showed that HL and DTZ had synergistic effect, and the flame retardancy mechanism of gas phase and condensed phase existed in the combustion process. Simultaneously, the addition of HL and DTZ also endowed the EP composite with excellent corrosion resistance and antibacterial properties.