The Thermal Degradation of Nanocomposites That Contain an Oligomeric Ammonium Cation on the Clay

The thermal degradation of polystyrene, high-impact polystyrene, ABS terpolymer, poly(methyl methacrylate), polypropylene and polyethylene nanocomposites has been studied using thermogravimetric analysis coupled to Fourier transform infrared spectroscopy, TGA/FT-IR. The nanocomposites that have been studied include immiscible, intercalated and exfoliated systems and the evolved gases do not depend upon the type of nanocomposite and are qualitatively similar to those of the virgin polymer. In the case of the styrenics, the presence of clay promotes the production of oligomer, rather than monomer. It is suggested that this change in evolved products may offer an explanation for why some polymers give large reduction in peak heat release rates while others give much smaller reductions. According to this notion, any polymer that undergoes degradation to produce both oligomer and monomer should give a large reduction in peak heat release rate

The Effect of Boron-Containing Layered Hydroxy Salt (LHS) on the Thermal Stability and Degradation Kinetics of Poly (Methyl Methacrylate)

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 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

Poly(Methyl Methacrylate), Polypropylene and Polyethylene Nanocomposite Formation by Melt Blending using Novel Polymerically-Modified Clays

Two new organically-modified clays that contain an oligomeric styrene or methacrylate have been prepared and used to produce nanocomposites of poly(methyl methacryate), polypropylene and polyethylene. Intercalated nanocomposites and, in some cases, exfoliated or mixed intercalated/exfoliated nanocomposites of all of these polymers have been produced by melt blending in a Brabender mixer. The use of the styrene-containing clay permits the direct blending of the clay with polypropylene, without the usual need for maleation, to produce the nanocomposites. The systems have all been characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, cone calorimetry and the measurement of mechanical properties. These novel new clays open new opportunities for melt blending of polymers with clays to obtain nanocomposites with important propertie

Novel Polymerically-Modified Clays Permit the Preparation of Intercalated and Exfoliated Nanocomposites of Styrene and its Copolymers by Melt Blending

Two new organically-modified clays have been made and used to produce nanocomposites of polystyrene, high impact polystyrene and acrylonitrile–butadiene–styrene terploymer. At a minimum, intercalated nanocomposites of all of these polymers have been produced by melt blending in a Brabender mixer and, in some cases, exfoliated nanocomposites have been obtained. The systems have all been characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, cone calorimetry and the measurement of mechanical properties. These novel new clays open new opportunities for melt blending of polymers with clays to obtain nanocomposites with important properties

Polybutadiene modified clay and its nanocomposites

A butadiene-modified clay was prepared by ionic exchange between sodium montmorillonite and a butadiene surfactant; the butadiene surfactant was obtained from the reaction of vinylbenzyl chloride grafted polybutadiene with a tertiary amine. Nanocomposites of polystyrene, high impact polystyrene, acrylonitrile–butadiene–styrene terpolymer, poly(methyl methacrylate), polypropylene and polyethylene were prepared by melt blending this modified clay with the virgin polymers. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, cone calorimetry and the evaluation of mechanical properties. A morphological study of PBD-modified clay–polymer nanocomposites shows that all the composites are immiscible micro-composites. The consistency of the result from XRD and TEM with that of cone calorimetry indicates that the cone calorimeter must also be considered as another method to examine the bulk sample and infer if good dispersion of the clay in the polymer has been achieved. The mechanical properties of the nanocomposites prepared from different methods show that the mechanical properties are, in general, predictable based on the type of dispersion

Study on the thermal stability of Polystyryl surfactants and its modified clay nanocomposites

Five oligomeric styrene surfactants, N,N,N-trimethylpolystyrylammonium, N,N-dimethyl-N-benzylpolystyrylammonium, N,N-dimethyl-N-hexadecylpolystyrylammonium, 1,2-dimethyl-3-polystyrylimidazolium, and triphenylpolystyrylphosphonium chlorides were synthesized and used to prepare organically modified clays. Both styrene and methyl methacrylate nanocomposites were prepared by melt blending and the type of nanocomposite was evaluated by X-ray diffraction and transmission electron microscopy. The thermal stability of the organically modified clays and the nanocomposites were studied by thermogravimetric analysis; these systems do give clays which have good thermal stability and may be useful for melt blending with polymers that must be processed at higher temperatures

Additional XPS Studies on the Degradation of Poly(Methyl Methacryalte) and Polystyrene Nanocomposites

XPS studies have been undertaken on exfoliated nanocomposites of polystyrene and poly(methyl methacrylate). One can clearly see that carbon is lost and that oxygen, silicon and aluminum accumulate at the surface of the degrading polymer. The concentration of aluminum at the surface is very low at the beginning of the experiment but makes a large jump at the same temperature at which carbon is lost and oxygen begins to accumulate at the surface. It appears that the ratio of silicon to aluminum changes as the polymer is lost. A brief discussion is given to explain the origin of oxygen at the surface

The Effects of Intralayer Metal Composition of Layered Double Hydroxides on Glass Transition, Dispersion, Thermal and Fire Properties of Their PMMA Nanocomposites

A series of aluminum-containing layered double hydroxides (LDHs), containing Mg, Ca, Co, Ni, Cu and Zn as the divalent metals, have been prepared by the co-precipitation method and used to prepare nanocomposites of PMMA by in situ bulk polymerization. The additives were characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy (XRD) and thermogravimetric analysis while the polymer composites were characterized by XRD, transmission electron microscopy, differential scanning calorimetry and cone calorimetry. Polymerization of methyl methacrylate in the presence of these undecenoate LDHs results in composites with enhanced thermal stability. The glass transition temperatures of the composites and the pristine polymers are found to be around 110 °C; this suggests that the presence of these additives has little effect on the polymer. It is found that the additive composition and the dispersion state of LDHs agglomerates in the polymer matrix influence the fire properties of composites as measured by cone calorimetry