Recycling of thermoplastic elastomers based on poly (phenylene ether) (PPE) was studied in detail. The quaternary blend comprising of styrene-ethylene-butylene-styrene (SEBS)/ethylene vinyl acetate (EVA)/PPE-PS (polystyrene) showed improvement in mechanical properties upon recycling, which was correlated with the formation of crosslinked network in the system. Presence of crosslinked network was confirmed by the gel content analysis. The blend components involved in the crosslinking were evaluated by gel morphology analysis. Fourier transform infrared spectroscopy revealed the chemical composition of the crosslinked gel. Crosslinking mechanism was established based on the reactivity of allylic EVA radical during recycling. Rheological study supported the notion of crosslinking upon recycling that resulted in higher storage modulus (G(I)) as a manifestation of restrained flow by network formation. On the basis of the earlier data, a reaction mechanism for crosslinking was proposed. Finally, structure-property correlation was developed through morphological, chemical, and rheological analysis to understand the anomalous enhancement in mechanical properties upon recycling.

A series of novel thermoplastic elastomers (TPEs) based on poly (phenylene ether)(PPE), which is an engineering thermoplastic with a glass transition temperature >200 degrees C, has been developed. The resulting blend based on PPE, Polystyrene (PS), Ethylene Vinyl Acetate (EVA) and a tri-block copolymer, Styrene-Ethylene-Butylene-Styrene (SEBS), met all the key performance criteria for thermoplastic elastomers in terms of melt processability, tensile elongation, tension set and recyclability. Depending on Flory's interaction parameter and critical surface tension value, the elastomeric components of the blends were selected. Morphological analysis of the blend using Transmission Electron Microscopy indicated a unique microstructure, wherein EVA domains were dispersed in a mainly co-continuous matrix comprising of the blend of PPE-PS/SEBS. Differential Scanning Calorimeter and Dynamic Mechanical Analysis were done to evaluate the thermal transitions of the blend and to throw light on the interactions between the various components of the blend. Thermogravimetric analysis indicated that PPE played a critical role by increasing the temperature of the onset of degradation of the blend. A comprehensive study of the structure-property correlations of this unique blend has been undertaken.

Detailed statistical trend analysis of thermoplastic elastomers based on poly (phenylene ether) (PPE), polystyrene (PS), ethylene vinyl acetate (EVA) and styrene-ethylene-butylene-styrene (SEBS) was done through Design Expert software by Stat-Ease. D optimal crossed design was followed to capture the interaction with the parameters. Effect of blend ratio, vinyl acetate (VA) content of EVA, molecular weight (MW) of SEBS and intrinsic viscosity (IV) of PPE on the blend performance (response) was studied in detail. Design of Experiment (DOE) analysis showed the "optimized formulation" of the blend. Increase in PPE-polystyrene (PS) content increased tensile strength and modulus of the blend, followed by a decrease in strain at break. However, EVA had a reverse effect on tensile strength and modulus. Strain at break increased significantly with increasing SEBS content in the blend. Graphical and numerical optimization showed that superior mechanical properties (tensile strength, strain at break and modulus) could be achieved at VA content - 50% at a particular loading of EVA. Low MW SEBS was found to be more compatible with the other components of the blend. Mechanical properties of the quaternary blend were marginally affected with change in IV of PPE in the range of 0.33 to 0.46

The direct catalytic decomposition of NO on Rh/Al2O3, Rh/C, Pd/Al2O3, and Pd/C catalysts was investigated at 673K by in situ infrared (IR) coupled with mass spectroscopy (MS). NO decomposition on these catalysts initially produced N2 and adsorbed oxygen. Different catalysts exhibit different capabilities for manipulating adsorbed oxygen. Rh/Al2O3 shows little activity for oxygen desorption, resulting in loss of catalyst activity; Rh/C shows the ability for promoting the adsorbed oxygen–carbon reaction, removing oxygen in the form of CO2; Pd/Al2O3 shows some activity for O2 desorption. Use of carbon as a support for Pd promotes O2 desorption, resulting in improvement of NO decomposition activity. The in situ IR results provide evidence to support the behavior of adsorbed oxygen on carbon-supported Rh and Pd catalysts.

Ag-Rh/SiO2 catalysts which exhibit activity and selectivity for oxygenate and hydrocarbon synthesis have been characterized by X-ray diffraction (XRD). XRD patterns show that the catalysts prepared using Rh chloride precursor contain Rh, Ag, AgCl, and AgClO2 crystallites. The size of these crystallites varied with the amount of Ag in the catalyst. The variation in crystallite size of Rh, Ag, AgCl, and AgClO2 with Ag/Rh ratio has an impact on the activity and selectivity for synthesis of oxygenates and hydrocarbons during CO hydrogenation and ethylene hydroformylation reactions. The selectivity towards oxygenates is decreased on the Ag-Rh catalysts due to the presence of AgCl and AgClO2 crystallites on the catalyst surface. Ag-Rh catalyst with Ag/Rh ratio of 0.5 gives a higher activity and selectivity for ethanol and propanol during CO hydrogenation and ethylene hydroformylation than the other Ag-Rh catalysts. Ag-Rh catalysts prepared from Rh chloride and Ag nitrate precursors are less active and selective for oxygenate synthesis than those prepared from nitrate precursors. Ag-Rh catalysts for oxygenate synthesis should be prepared using nitrate precursors.

The transient nature of adsorbates for the reaction of NO with CO over a 4 wt % Rh/SiO2 catalyst has been studied by in situ infrared spectroscopy combined with pulse transient techniques. Dynamic behavior of infrared-observable Rh-NO-, Rh-NO+, Rh+(CO)(2), and linear and bridged CO reveals that dissociation of Rh-NO- oxidizes Rh-0 to Rh+; Rh+ chemisorbs CO and NO as Rh+(CO)(2) and Rh-NO+, respectively; and Rh+(CO)(2) can either undergo reductive agglomeration or react with adsorbed oxygen to produce CO2 at 473-523 K. At 573 K, Rh is in the reduced state where linear CO and bridged CO react with the oxygen produced from dissociation of Rh-NO- to produce CO2. The catalyst in the reduced surface state is more active for the formation of N2O and CO2 products, and the response of N2O formation leads that of CO2 formation at temperatures below the light-off temperature. The rapid CO2 response during the pulse reaction studies indicates that the reaction can quickly reach steady state at temperatures above 473 K when the reaction conditions are altered.

The reactivity of adsorbed CO on supported rhodium catalysts for the insertion of CO during ethylene hydroformylation and for CO2 formation during interactions of CO and NO has been studied by in situ infrared spectroscopy. Adsorption of CO on 0.5 wt.% Rh/SiO2 produced Rh carbonyl species which are highly selective for CO insertion (i.e. ethylene hydroformylation) at 323 K. Adsorption of CO on highly dispersed Rh sites of 0.2 wt.% Rh/Al2O3 produced linear CO and gem-dicarbonyl which are inactive for the CO insertion in contrast to linear CO on large Rh crystallites and gem-dicarbonyl on thermally decomposed Rh6(CO)16/SiO2 catalysts. The reactivity and the mode of adsorbed CO on 4 wt.% Rh/SiO2 strongly depends on the partial pressure of gaseous CO and NO. Linear and bridged CO on reduced Rh sites and gem-dicarbonyl on Rh+ sites do not show any reactivity toward gaseous NO/CO for the formation of CO2 at 373 K. Prolonged exposure of rhodium catalysts to NO/CO flow results in modification of catalyst surface, creating the active site for catalyzing CO2 formation at 373 K. Strong dependence of the reactivity and mode of adsorbates on the partial pressure of reactants and temperature suggests that the nature of adsorbates should be studied under reaction conditions where both reactants and products are present.

Interaction and reaction of adsorbed NO and CO on Rh and Ce-Rh catalysts have been studied by combined in situ infrared spectroscopy and temperature-programmed reaction at 298-673 K. At 298 K, adsorption of NO as NO- causes the desorption of preadsorbed linear and bridged CO from reduced Rh sites. NO adsorption competes over CO adsorption on the reduced Rh while NO does not adsorb on oxidized Rh catalyst which chemisorbs CO as gem-dicarbonyl. Temperature-programmed reaction study reveals that the type of adsorbate and the surface state of the catalyst change with temperature. At 453 - 543 K, NO adsorbs as low wavenumber NO- at 1689-1696 cm-1 which may be involved in NO dissociation and CO adsorbs as gem-dicarbonyl which may be a spectator species for this reaction.

The temperature-programmed reaction (TPR) technique coupled with infrared (IR) spectroscopy has been employed to study the reactivity of adsorbed CO towards hydrogen. The combination of the two techniques provides information on the structure and reactivity of adsorbates, activation energy and kinetic data for the CO hydrogenation reaction. CO adsorption on RhSiO2 at 298 K produced mainly linear and bridged CO on the surface. Linear CO appears to be more reactive than bridged CO in the formation of methane during TPR over RhSiO2. The addition of silver to RhSiO2 promotes the formation of gem-dicarbonyl CO and suppresses the formation of bridged CO during CO adsorption at 298 K. The disproportionation of gem-dicarbonyl CO and the reduction of Rh+ by oxidation of the CO ligand of Rh+(CO)2 produce CO, CO2, and surface carbon on the AgRhSiO2 catalyst at temperatures above 310 K. Hydrogenation of surface carbon begins at 390 K leading to methane formation. The methane peak temperature was observed at 442 K on the AgRhSiO2 and at 420 K on RhSiO2. The higher hydrogenation temperature of adsorbed CO and surface carbon over AgRhSiO2 as compared to RhSiO2 is attributed to the suppression of hydrogenation by Ag.

A pulse (CO)-C-13 transient incorporated with in situ infrared technique has been used to study CO hydrogenation over Rh/SiO2 catalysts. Increasing reaction temperature decreases tau(CH4) (residence time of intermediates leading to methane); however, increasing reaction pressure increases tau(CH4). High tau(CH4) at high pressure allows the insertion of CO into CHX to occur leading to the formation of acetaldehyde.