Abstract
Deoxyribonucleic Acid (DNA) has been recently found to be an efficient renewable and environmentally-friendly flame retardant. In this work, for the first time, we have used waste DNA from fishing industry to modify clay structure in order to increase the clay interactions with epoxy resin and take benefit of its additional thermal property effect on thermo-physical properties of epoxy-clay nanocomposites. Intercalation of DNA within the clay layers was accomplished in a one-step approach confirmed by FT-IR, XPS, TGA, and XRD analyses, indicating that d-space of clay layers was expanded from ~1.2 nm for pristine clay to ~1.9 nm for clay modified with DNA (d-clay). Compared to epoxy nanocomposite containing 2.5%wt of Nanomer I.28E organoclay (m-clay), it was found that at 2.5%wt d-clay loading, significant enhancements of ~14%, ~6% and ~26% in tensile strength, tensile modulus, and fracture toughness of epoxy nanocomposite can be achieved, respectively. Effect of DNA as clay modifier on thermal performance of epoxy nanocomposite containing 2.5%wt d-clay was evaluated using TGA and cone calorimetry analysis, revealing significant decreases of ~4000 kJ/m2 and ~78 kW/m2 in total heat release and peak of heat release rate, respectively, in comparison to that containing 2.5%wt of m-clay.
Highlights
Modifications improve the dispersion of clay into polymer matrices, the interface of the modified clay layers with polymer matrices are not usually taken into account and the interactions at interface remain as weak as van der Waals interactions[15,16] which could be accompanied with adverse plasticisation effects at clay-matrix interface[17]
Cationic amine groups of polydopamine were exchanged with clay cations, and the hydroxyl groups of polydopamine were tasked to enhance the interfacial interactions through forming hydrogen bondings with an epoxy polymer
The sodium phosphates groups can potentially act as a nucleophile intermediate in organic reactions e.g., reaction with epoxide rings. Inspired by these features of DNA, we hypothesized that if DNA can be intercalated within clay layers, interfacial interactions as well as thermal performance of epoxy/clay system may significantly be improved in comparison to those commercially modified
Summary
Modifications improve the dispersion of clay into polymer matrices, the interface of the modified clay layers with polymer matrices are not usually taken into account and the interactions at interface remain as weak as van der Waals interactions[15,16] which could be accompanied with adverse plasticisation effects at clay-matrix interface[17]. The amount of graftable hydroxyl groups on clay surface and edges are extremely limited and amount of silane grafted is low, in comparison to organic modifiers using cations exchange[24] To overcome these challenges, modification based on cations exchange which appears to be more efficient in terms of its quantity, has to be formulated to create strong interactions between clay layers and polymer matrices, obtaning the desirable properties. The sodium phosphates groups can potentially act as a nucleophile intermediate in organic reactions e.g., reaction with epoxide rings Inspired by these features of DNA, we hypothesized that if DNA can be intercalated within clay layers, interfacial interactions as well as thermal performance of epoxy/clay system may significantly be improved in comparison to those commercially modified. Structure, morphology, mechanical, thermal, and flammability performance of these newly developed nanocomposites, have been comprehensively investigated while focusing on the role of interfacial interactions between modified clay and polymer matrix
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