• journal_title：Clays and Clay Minerals
• Contributor：Ling Shi ; Dianqing Li ; Jianrong Wang ; Sufeng Li ; David G. Evans ; Xue Duan
• Publisher：Clay Minerals Society
• Date：2005-
• Format：text/html
• Language：en
• Identifier：10.1346/CCMN.2005.0530309
• journal_abbrev：Clays and Clay Minerals
• issn：0009-8604
• volume：53
• issue：3
• firstpage：294
• section：Articles

Reaction of a Mg-Al carbonate layered double hydroxide (LDH) with boric acid leads to a borate-pillared LDH with the stoichiometry [Mg_0.65Al_0.35(OH)₂][B₃O₅]_0.35·0.65H₂O and an interlayer spacing of 1.07 nm. Infrared and ¹¹B magic angle spinning nuclear magnetic resonance data are consistent with the presence of polymeric triborate anions of the type [B₃O₄(OH)₂]_nⁿ⁻ in the interlayer galleries so that the material can be formulated as [Mg_0.65Al_0.35(OH)₂][B₃O₄(OH)₂]_0.35·0.30H₂O. The flame-retardant properties of the borate-pillared material and the carbonate precursor in composites with ethylene vinyl acetate copolymer were compared. Introduction of the borate anion leads to a significant enhancement in smoke suppression during combustion without compromising the flammability of the material. This is related to the synergistic effect between the host layers of the LDH and the borate anions uniformly distributed in the interlayer region.