Thermal and flammability study of polystyrene composites containing magnesium–aluminum layered double hydroxide (MgAl–C16 LDH), and an organophosphate
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The flame retardancy and thermal stability of polystyrene compounded with Bis(2,4-dicumylphenyl)pentaerythritol diphosphate (DPP) and or a palmitate containing magnesium aluminum LDH (MgAl–C16 LDH) were investigated via thermogravimetric analysis, cone calorimetry, and pyrolysis combustion flow calorimetry. Cone calorimetry and thermogravimetry measurements revealed that the addition of 5 and 10 mass% of MgAl–C16 LDH to PS resulted in substantial reduction in peak heat release rate (PHRR) (47 and 61 %, respectively) of the polymer and minimal improvements in thermal stability (5 and 2 °C, respectively, for the temperature at which 50 % mass loss occurs, ΔT 50). On the other hand, there was insignificant reduction in PHRR for composites containing DPP at loadings of 5 mass%, while loadings of 10 mass% resulted in a relatively low reduction of 22 %. This difference was attributed to the more compact residue formed by the LDH systems during cone calorimetry analysis. There was substantial improvements in the thermal stability of PS compounded with 10 mass% of DPP with ΔT 50 being 21 °C. The combination of DPP and LDH resulted in a negative effect on the flammability performance of the LDH; thus, we did not observe any synergism between the LDH and DPP. Results from micro-scale combustion calorimetry did not correlate with results from cone calorimetry.
KeywordsBis(2,4-dicumylphenyl)pentaerythritol diphosphate Polymer composites PS Thermal stability Flammability Cone calorimetry
The Author would like to thank Professor C. A. Wilkie of Marquette University, USA, for the use of the cone calorimeter and SDT 2960 simultaneous DTA–TGA instrument. I would also like to thank Lumbidzani Moyo of Council for Scientific and Industrial Research, South Africa, for the MgAl–CO3 TG spectrum.
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