Fully Biobased Surface-Functionalized Microcrystalline Cellulose via Green Self-Assembly toward Fire-Retardant, Strong, and Tough Epoxy Biocomposites

Abstract

The design of renewable and fully biobased flame retardants (FRs) with high efficiencies and mechanical reinforcement functions for epoxy resin (EP) can greatly advance their potentials to satisfy sustainability. Although some biobased fire retardants have been successfully developed so far, most of existing biobased FRs are often not fully biobased and their syntheses normally involve the use of a large volume of organic solvents in addition to complicated synthesis processes. Herein, we report a facile and green strategy to synthesize fully biobased FR (P-MCC@CS@PA-Na) by surface-functionalizing microcrystalline cellulose (MCC) with chitosan (CS) and sodium phytate (PA-Na) via layer-by-layer assembly in water. The results show that incorporating 15 wt % P-MCC@CS@PA-Na enables EP composite to pass a UL-94 V-1 rating with a limiting oxygen index of 26.2%. Meanwhile, the peak heat release rate, total heat release, peak smoke production release, total smoke production, the fire growth rate, and the fire retardancy index of the EP/15 wt % P-MCC@CS@PA-Na are greatly reduced, indicating a good fire retardance. Notably, the well-designed P-MCC@CS@PA-Na simultaneously strengthens and toughens the EP because of uniform dispersion and a favorable interfacial compatibility between P-MCC@CS@PA-Na and the EP matrix. This work provides a green strategy for the fabrication of highly efficient multifunctional fully biobased FRs for polymers.

Chitosan–Fe(III) Complexes via Green Preparation toward Flame Retardant and High-Mechanical-Strength Epoxy Composites

“…The tensile modulus of EP/9CS–Fe of 1883 MPa was comparable with that of EP of 1881 MPa, and the flexural modulus was greatly improved, from 2033 MPa in EP to 4372 MPa in EP/9CS–Fe, an increase of 115% (Figure b,e). Generally, strength and toughness (obtained by integration of stress–strain curves − ) of the mechanical properties of the material are usually mutually exclusive. Interestingly, there was no decrease in toughness even though the tensile and flexural toughness in EP/9CS–Fe increased to 2.54 and 4.32 MJ m –3 (Figure c,f), indicating increases of 25 and 119%, respectively.…”

The design of a metal–organic framework with flame-retardant performance and bionic hydrophobic surface inspired by the lotus leaf

“…The time to ignition (TTI) of pure PS is 37 s while the PS composite's TTI is 47 s, indicating that the addition of S-Fe-MOF delays ignition. 20 The peak heat release rate (PHRR) of pure PS is as high as 796 kW m À2 . With the loading of a The temperature at 5% mass loss is defined as T 5% .…”

Surface modification of cellulose nanocrystal and its applications in flame retardant epoxy resin

“…Lou et al reported a green self-assembly method to prepare fully bio-based surface functionalized microcrystalline cellulose with phytic acid and chitosan which was denoted as P-MCC@CS@PA-Na. 21 The addition of 15% P-MCC@CS@PA-Na could reduce PHRR from 1007 to 501 kW/m 2 without deteriorating mechanical property. The modification of cellulose in previous studies is mainly conducted by the covalent reaction between hydroxy groups and phosphoric acid to form phosphite groups or phosphoric acid groups, 22 which needs harsh reaction conditions such as high temperature and pressure.…”

“…The feasible combination of intumescent flame retardants into one compound helped to induce the formation of dense and continuous char residue. Lou et al reported a green self‐assembly method to prepare fully bio‐based surface functionalized microcrystalline cellulose with phytic acid and chitosan which was denoted as P‐MCC@CS@PA‐Na 21 . The addition of 15% P‐MCC@CS@PA‐Na could reduce PHRR from 1007 to 501 kW/m 2 without deteriorating mechanical property.…”