Thermal stability and fire retardancy of PMMA (nano)composites with layered metal hydroxides containing dodecyl sulfate anions

摘要

Layered double hydroxides (LDHs) with Mg/Al, Zn/Al, Ca/Al metal hydroxide layers, and a Zn/Ni hydroxy double salt (HDS) were prepared with a common anion, dodecyl sulfate [CH_3(CH_2)_(10)COO~-, DS]. The LDH and HDS additives were melt blended with poly(methyl methacrylate) (PMMA). The dispersion and morphology were characterized via X-ray diffraction (XRD) and transmission electron microscopy. Mg/Al-DS and Zn/Al-DS LDHs were found to form nano-composites with PMMA, exhibiting good dispersion and some degree of exfoliated morphology for the Zn/Al-DS/ PMMA combination and mixed intercalation and exfoliation behavior for Mg/Al-DS in PMMA. The Ca/Al-DS LDH and Zn/Ni-DS HDS formed microcomposites with PMMA. Thermal stability was investigated via thermogravimetric analysis; each of the additives increased the thermal stability of PMMA. Cone calorimetry was used to measure the fire properties; the microcomposite of Zn/Ni-DS HDS at 10% loading provided the best improvement in peak heat release rate, with a 40% reduction over the pure polymer. The residue composition after burning the composites was investigated.