SYNOPSISPeroxide initiated graft copolymerization of vinyl trimethoxy silane ( VTMO ) and vinyl triethoxy silane (VTEO) onto polyethylene ( P E ) and ethylene propylene copolymer ( E P R ) was studied. The kinetics of grafting, studied by differential scanning calorimetry, are the same for all the systems and the activation energy for VTMO is 170 ? 4 KJ/mol. Activation energy for VTEO is 185 ? 5 KJ/mol. The VTMO and VTEO graft copolymers of PE and EPR were prepared by reactive processing in a Brabender extruder in the temperature range of 150-200°C. Moisture catalyzed crosslinking of the silane grafted copolymer was also studied. The influence of the structure of the catalyst, its concentration, moisture concentration, temperature, and time on degree and rate of crosslinking has been evaluated. Crosslinking reactions follow first order kinetics with respect to both catalyst and moisture concentration. Activation energy ( E , ) of the crosslinking reaction has been determined as 65 K J mol-' . The mechanism of grafting and crosslinking is discussed.

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Raman studies of nanocomposite SiCN thin film by sputtering showed that with increase of substrate temperature from room temperature to 500

Si-C-N/Si based MEMs are advantageous to conventional MEMS because of their ease of fabrication and high temperature sustainability. The failure mechanism of such systems has to be known for their efficient performance. Nanoindentation and scratch behavior were performed on Si-C-N coatings deposited on silicon substrates by RF magnetron sputtering. Crack growth and propagation were studied using optical and SEM views of the deformed region. Different failure mechanisms were observed and analyzed. The crack deflection was due to nanocrystalline phases in the Si-C-N nanocomposite film, as no such deflection was observed in the amorphous CNx film. A different failure mechanism in the form of tensile and conformal cracking was observed. The films' failure mechanism changes from cohesive failure at lower loads to adhesive failure at higher loads during nanoscratching.

Functionalization of polyethylene (PE) and ethylene propylene diene terpolymer (EPDM) in the bulk through dicumyl peroxide (DCP) initiated grafting of dibutyl maleate (DBM) has been studied in the temperature range from 140 to 200°C. The degree of grafting has been determined by infrared spectrophotometry and DSC. The concentration of DBM and DCP has been optimized. 0.5 wt.-% and 0.2 wt.-% DCP for PE and EPDM, respectively, and 10% DBM for both have been found to be the optimum. The kinetics of the grafting reaction is comparable for PE and EPDM. The activation energy of grafting is ca. 145 kJ/mol for PE and ca. 130 kJ/mol for EPDM. The influence of structure of polyolefins on the degree of grafting has also been studied. A higher degree of grafting is obtained for PE than for EPDM. For PE/EPDM blends, the degree of grafting increases with increasing PE content in the blends. A thorough discussion and proposed mechanism for grafting and other competitive secondary reactions has been provided. ZUSAMMENFASSUNG: PE und EPDM-Kautschuk wurden durch Aufpfropfen von Dibutylmaleat (DBM) mit Dicumylperoxid (DCP) als Initiator in Substanz im Temperaturbereich von 140-220 "C funktionalisiert. Der Pfropfungsgrad wurde IR-spektroskopisch und durch DSC-Messungen ermittelt. Die fur die Pfropfung optimalen DBM-und DCP-Konzentrationen betragen 0,5 bzw. 0,2 Gew.-To. Die Kinetik der Pfropfreaktion ist fur PE und EPDM vergleichbar; die Aktivierungsenergien betragen ca. 145 bzw. 130 kJ/mol. Die Pfropfungsgrade sind fur PE htiher als fur EPDM; bei PE/EPDM-Blends