ABSTRACT:The current investigation was aimed at assessing the effect of carboxylation of NBR phase in dynamically vulcanized NBR/low-melting polyamide thermoplastic elastomeric compositions. Improved strength and set properties were achieved because of better compatibilization with carboxylated NBRs. The dispersion of the rubber became homogeneous and finer with increase in the degree of carboxylation. Glass transition studies by DMA and DSC suggested the presence of a compatibilizing block copolymer generated in situ by the reaction between the OCOOH groups in the rubber and the ONH 2 groups in the polyamide during melt-mixing. The reaction was studied for a representative 60 : 40 rubber/plastic blend by DSC.

ABSTRACT:The effect of electron beam irradiation on ethylene-propylene terpolymer (EPDM) was investigated. A 50-part oil-extended EPDM with high termonomer (ENB) content (iodine number of base polymer) 19, was selected for this study. An increase in irradiation dose from 0 to 200 kGy resulted in increased crosslinking, measured by an increase in gel contents and better swelling resistance. The effect of the multifunctional monomer trimethylol propane trimethacrylate (TMPTMA) as a crosslink promoter was studied using IR spectroscopy. The IR studies revealed enhanced peak absorbances at 1725, 1257, and 1023 cm Ϫ1 as a result of the increased concentration of C ϭ O and C-O-C groups and reduced absorbance at 1630 cm Ϫ1 due decreased concentration of C ϭ C groups with TMPTMA level in the irradiated samples. The presence of TMPTMA increased the level of crosslinking at a given irradiation dose, which was manifested by improvement in tensile properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 968 -975, 2005

Polymer blends of carboxylated butadieneacrylonitrile copolymer (nitrile rubber) and polyamide 6 (PA6) were developed in twin screw extrusion. The rubber was cured with SP 1045 methylol phenolic resin during melt mixing in twin screw. Effect of degree of carboxylation in the rubber phase on blend properties has been assessed. Phase morphologies have been characterized using transmission electron microscopy. A compatibilizing NBR-g-Nylon 6 graft copolymer generated in situ during melt mixing via interfacial reaction between the À ÀCOOH groups in NBR and the À ÀNH 2 end groups in nylon 6 has been effective in generating a fine and stable dispersion of the rubber within the polyamide matrix. The graft copolymer has been characterized by DMTA.

ABSTRACT:The electron-beam-induced crosslinking of hydrogenated acrylonitrile-butadiene rubber (HNBR) was investigated. HNBR sheets were exposed to electron-beam irradiation in air at a room temperature of 25 Ϯ 2°C over a dose range of 0 -20 Mrad. An attempt was made to correlate the structure of the irradiated rubber with the properties. The ratio of chain scission to crosslinking and the gelation dose were determined by a method proposed elsewhere. The gel content and dynamic storage modulus increased with the radiation dose. Fourier transform infrared studies revealed the formation of double bonds and carbonyl and ether groups. These observations were further supported by a thermogravimetric analysis of the carbonaceous residue of irradiated HNBR.

Quantitative and qualitative analyses of chlorine-containing elastomer blends, like neoprene rubber/chlorosulfonated polyethylene and neoprene rubber/nitrile-polyvinyl chloride, with carbon black and other fillers, are complex and confusing because the blends contain the same carbonOchlorine moiety. Various interfering phenomena by fillers, co-curing by the common ingredients, and uncertainty in functional group analysis make the determination of the ratio of component elastomers in chlorine-containing elastomer blends very difficult or sometimes almost impossible by Fourier transform infrared and thermogravimetric analysis techniques. However, differential scanning calorimetry (DSC) and supportive differential thermogravimetry (DTG) are very useful techniques to assess such complex materials. Enough flexibility associated with specific heat (from DSC) and response zone (from DTG) can avoid the interfering effects. The DSC-DTG technique thus can be an effective tool to determine the ratio of component polymers in chlorine-containing elastomer blends.