Structure and properties research on montmorillonite modified by flame-retardant dendrimer

• Mt was modified by THPC, and a novel type of OMt was obtained.
• Three generations of dendrimer modified OMt were successfully prepared.
• A dendrimer type of FR-DOMt was prepared by DOMt and boric acid.
• FR-DOMt had better thermal stability and larger d-value.

A novel approach to highly branched polymer chains for making advanced flame-retardant organoclays (OC) was presented. In this effort, a series of dendrimer based montmorillonite (Mt) were synthesized by tetrahydroxymethyl phosphonium chloride (THPC), N, N-dihydroxyl-3-aminomethyl propionate, and boric acid.Mt was first modified by THPC, and organic Mt (OMt) was obtained. Three generations of dendrimer modified organic clay minerals, DOMt-1, DOMt-2, and DOMt-3, were successfully prepared by OMt and the monomer prepared. Their chemical structures were characterized by FTIR, 1H NMR, elemental analysis, XRD, and TGA. These DOMts had expanded interlayer space and possessed good thermal stabilities. With an increase of generations, the thermal stability was not further enhanced for highly branched polymers due to the increasing content of CH bonds. These DOMts were terminated by boric acid, and a flame-retardant and dendrimer modified OMt (FR-DOMt) was successfully prepared. Experiments demonstrated that this FR-DOMt had better thermal stability and larger d-value due to steric hindering and thermal stability of the surfactant. The chemical structure and properties of FR-DOMt were valuable for its further applications.