Abstract:A boron-containing layered hydroxy salt (LHS), ZHTMDBB, was prepared and compounded with a highly flammable synthetic polymer, poly (methyl methacrylate) {PMMA}, via melt blending: the composite structure was intercalated with poor dispersion. The effect of this LHS on the NOT THE PUBLISHED VERSION; this is the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation at the bottom of the page.Polymer Degradation and Stability, Vol. 95, No. 9 (September 2010): pg. 1593-1604. DOI. This article is © Elsevier and permission has been granted for this version to appear in e-Publications@Marquette. Elsevier does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from Elsevier. 2 flammability, thermal stability and degradation kinetics of PMMA was investigated via cone calorimetry and thermogravimetric analysis. The addition of 3-10% by mass of ZHTMDBB to PMMA resulted in significant reduction of peak heat release rate (22-48%) of the polymer and improvements in thermal stability were observed in both air and nitrogen. Effective activation energies for the degradation process were evaluated using Flynn-Wall-Ozawa, Friedman, and Kissinger methods. All three methods indicated that the additive increased the activation energies of the first step of the degradation process in both air and nitrogen. Activation energies of the second step were lowered in nitrogen but were not significantly affected in air.

Anion exchange reactions of nanodimensional layered metal hydroxide compounds are utilized to create materials with targeted physical and chemical properties and also as a means for controlled release of intercalated anions. The kinetics of this important class of reaction are generally characterized by model-based approaches. In this work, a different approach based on isothermal, isoconversional analysis was utilized to determine effective activation energies with respect to extent of reaction. Two different layered metal hydroxide materials were chosen for reaction with chloride anions, using a temperature range of 30−60 °C. The concentrations of anions released into solution and the changes in polycrystalline solid phases were evaluated using model-based (Avrami-Erofe'ev nucleation−growth model) and model-free (integral isoconversional) methods. The results demonstrate the utility of the isoconversional approach for identifying when fitting to a single model is not appropriate, particularly for characterizing the temperature dependence of the reaction kinetics.

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Organically-modified montmorillonite (MMT) clays have been prepared using ammonium salts containing quinoline, pyridine, benzene, and styrenic groups. The nanocomposites were prepared by melt blending and the formation of nanocomposites was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and flammability were evaluated by thermogravimetric analysis (TGA) and cone calorimetry measurements, respectively. The presence ofmodified MMT at 5% loading resulted in significant improvement in thermal stability compared to the virgin polymer. Effective activation energies for mass loss were determined via a model-free isoconversional approach from TGA data obtained under N2 and under air. The additives served to raise the activation energy, with a more significant impact observed under pyrolysis conditions. The onset temperature of degradation and temperature of maximum decomposition rate are increased, while the peak heat release rate and mass loss rates are significantly reduced in the presence of three of the modified clays. No reduction in the total heat released is observed.

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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, DT 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 DT 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.

Organically-modified montmorillonite (MMT) clays have been prepared using ammonium salts containing quinoline, pyridine, benzene, and styrenic groups. The nanocomposites were prepared by melt blending and the formation of nanocomposites was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and flammability were evaluated by thermogravimetric analysis (TGA) and cone calorimetry measurements, respectively. The presence of modified MMT at 5% loading resulted in significant improvement in thermal stability compared to the virgin polymer. Effective activation energies for mass loss were determined via a model-free isoconversional approach from TGA data obtained under N 2 and under air. The additives served to raise the activation energy, with a more significant impact observed under pyrolysis conditions. The onset temperature of degradation and temperature of maximum decomposition rate are increased, while the peak heat release rate and mass loss rates are significantly reduced in the presence of three of the modified clays. No reduction in the total heat released is observed.

Use of medicinal plants and herbs in the treatment and management of diseases, including diabetes mellitus and its complications remains an integral part of African tradition. In Zimbabwe, nearly one million people are living with diabetes mellitus. The prevalence of diabetes mellitus in Zimbabwe is increasing every year due to lifestyle changes, and has accelerated the use of traditional medicines for its treatment and management in urban areas. In addition, the high cost of modern medicine has led many people in rural parts of Zimbabwe to rely on herbal plant medicine for the treatment of diabetes mellitus and its complications. This review highlights a number of studies carried out to evaluate the antidiabetic properties of indigenous plants found in Zimbabwe with the goal of treating diabetes mellitus. Further, we discuss the mechanism of action of various plant extracts in the treatment and management of diabetes mellitus. Together, this review article can open pathways leading to discovery of new plant derived medicines and regularization of use of crude plant remedies to treat diabetes mellitus by the Zimbabwean government and others across Africa.