One-pot complexation of phytic acid and polyethyleneimine on cellulosic microfibers towards insulative and flame-resistant foam.

Flame resistance is required for the deployment of bio-based materials, especially those forming cellular structures that endow thermal insulation. This study proposes a one-pot strategy to prepare cellular lignocellulosic composites with excellent flame resistance. Lignocellulosic microfibers were used as the substrate onto which a flame-retardant complex consisting of P-containing phytic acid (PA) and N-containing polyethyleneimine (PEI) was formed. Following the prediction of ab initio molecular dynamics simulation, PA and PEI are integrated onto MF-CTMP following a single-step complexation assembly triggered by pH effects. The PA-PEI modified MF-CTMP can be readily transformed into a composite solid foam by dewatering a wet foam followed by oven drying. At the expense of a slightly reduced thermal insulation (thermal conductivity increase from 33.6 ± 0.6 to 40.0 ± 0.6 mW/(m·K)) the presence of PA-PEI complexes significantly improved the mechanical performance of the foam and uniquely endows it with flame resistance. Compared to unmodified MF-CTMP foams, the composite foams showed significant improvement in the Young's, specific compression, and flexural moduli (increased by 13.5, 5.5, and 7.3 folds, respectively), a high oxygen index (up to 40.8 %) and self-extinguishing effects. The results suggest the suitability of the introduced lignocellulosic foam as an alternative to traditional synthetic polymer-based counterparts as well as inorganic matter for insulation, particularly relevant to the building sector.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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