Shengpei Su

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 properties.

Novel polymerically-modified clays permit the preparation of intercalated and exfoliated nanocomposites of styrene and its copolymers by melt blending

Abstract 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.

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.

Additional XPS studies on the degradation of poly(methyl methacrylate) 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.

Effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with α-cyclodextrin

The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with α-cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and formed inclusion complexes (ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of α-CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with α-CD was also studied. The ICs were prepared with α-CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the α-CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to α-CD of the resulted ICs increases with increasing of temperature.

Thermal degradation of polymer–carbon nanotube composites

Abstract: This chapter discusses the thermal degradation of polymer–carbon nanotube (CNT) composites which plays a crucial role in determining their processing and applications. The chapter first reviews the mechanisms of thermal degradation/stability improvement by carbon nanotubes, which is affected by the barrier effect, thermal conductivity of CNT, physical or chemical adsorption, radical scavenging action, and polymer–nanotube interaction. It then describes the thermal degradation/stability of polymer–CNT composites and their development trends. It is necessary and meaningful to further investigate the thermal degradation of polymer–CNTs.

pH-responsive pseudorotaxane between comblike PEO-grafted triblock polymer and α-cyclodextrin

The pH-responsive inclusion complexation of comblike triblock polymer, P2VP-b-PPEOMA-b-P2VP, with α-cyclodextrin (α-CD) was studied. The triblock polymer was prepared by reversible addition–fragmentation chain transfer polymerization (RAFT) and formed inclusion complexes (ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of α-CD units. For comparison, PPEOMA homopolymer was prepared, and the inclusion complexation with α-CD was also studied. The formed ICs were characterized by XRD and 1H NMR. The results revealed that P2VP-b-PPEOMA-b-P2VP can form ICs with α-CD even when forming micelles, and the introduction of P2VP had a great influence on the solution property and the stoichiometry of EO to CD of the inclusion complexes depending on the concentration and the pH of the solution.

Improved morphology and mechanical properties of UPA6/TPEE blends by reactive compatibilization:

In this study, series of blends were prepared by blending unextracted polyamide-6 (PA6) and thermoplastic ester elastomer (TPEE) in certain ratios. The morphologies, thermal behaviors, and mechanical properties of blends have been investigated. Scanning electron microscope results revealed that the morphology of blends was improved significantly when the content of TPEE is less than 50 wt%. Tensile fracture surface images confirmed reactive compatibilization and stress-induced crystallization in blends. The effect of unextracted PA6 content on the elasticity and tensile strength of blends was also studied, and higher elongation rate at break and breaking strength could be achieved when the content of TPEE is ≥50 wt%. The most interesting finding in this study is that the glass transition temperature for rubber phase of blends shifts to lower temperature and decreases with the increase of unextracted PA6 content at certain ratios range.