Intercalation Strategies of Synthesizing Clay/Polymer Hybrids and Clay/Phosphazene Nanocomposites for Fire-Retarding and the Synergistic Effect
Date Issued
2014
Date
2014
Author(s)
Chiou, Jau-Yu
Abstract
Layered silicate clays are natural crystallites and are well recognized for their organic intercalation for nanocomposite applications. In this study, a new mechanism is revealed by selection of hydrophobic polyetheramines with a poly(oxypropylene) (POP) backbone and a methyl terminus as the intercalation agent. Specifically, the monoamine with a molecular weight of 2000 g/mol widened the basal spacing of the layered sodium montmorillonite up to 74 A and further expansion to 84 A, 96 A, and 100 A by a second intercalation different from the ionic exchange reaction. Kinetic studies indicated that the first stage of intercalation occurred after a critical concentration of a monoamine, while the second stage had no critical concentration behavior. This two-step method shows the potentials for synthesizing suitable organoclay nanostructures for encapsulating phase change materials (PCM) and oil recovery from the spilt ocean. The exploration of the in-depth understanding of clay confinement chemistry leads the strategic design of new materials and oil recovery process.
We further synthesized the phosphazene-amine adduct of hexachlorocyclophosphazene (HCP) and poly(oxypropylene)-diamines of 400 g/mol molecular weight (D400) by amine/chloride substitution and triethylamine removal of HCl. Subsequently, the adduct HCP-D400 was physically mixed with exfoliated silicate platelets (SP) to prepare the HCP-D400/silicate hybrids (HCP-D400/SP). The HCP-D400/MMT (HCP-D400 intercalated Na+-MMT) and HCP-D400/Na+-MMT (HCP-D400 physically mixed with Na+-MMT) were also prepared for comparison with HCP-D400/SP. A more homogeneous silicate distribution HCP-D400/SP than the HCP-D400/MMT counterparts in epoxy nanocomposites was revealed by SEM-EDX, XRD, and TEM analyses. The epoxy nanocomposite with 10 wt% of HCP-D400/SP, HCP-D400/MMT, and HCP-D400 had a degradation temperature at 80 % weight loss (T80 wt%) of 757 oC, 712 oC, and 519 oC, respectively, in comparison with the 500 oC of the pristine epoxy system. Anti-flame test confirmed that the HCP-D400/SP epoxy nanocomposite had a higher limit oxygen index (LOI) of 27.0 % than the HCP-D400/MMT counterpart (24.0 %). The degree of exfoliating the layered clay into random silicate platelets is the predominant factor for the thermal stability enhancement. It is also demonstrated that the co-presence of phosphazene-amines and silicate platelets has a synergistic effect in improving the thermal behavior of the nanocomposites.
Subjects
黏土插層/脫層機制
階段式插層
奈米容器
奈米複合材
熱穩定性
Type
thesis
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