The effects of natural (MT) and organically modified (O-MT) montmorillonite clays on the properties of polydimethylsiloxane (PDMS) rubber were evaluated. Rubber composites with different clay contents were prepared by a compounding procedure in an open two-roll mill, which was followed by a compression-molding step in which the PDMS matrix was peroxide crosslinked. The clay rubber composites were characterized by swelling measurements in toluene, thermogravimetric analyses, X-ray diffraction, scanning electron microscopy, and tensile tests. The introduction of MT restricted the solvent swelling and increased the crosslinking density of the rubber, which indicated the formation of a covalent filler-matrix interface. The enhanced interaction between MT and PDMS reduced the aggregation size of MT particles in the MT composites and promoted an increase in the separation of the clay layers. When the rubber was filled with O-MT, a higher solvent amount was incorporated in the material, and this trend increased with the clay content. Moreover, the low interaction between O-MT and the PDMS chains resulted in larger clay aggregates in the O-MT composites compared to those with MT. Despite the different interface natures, both clays enhanced thermal stability and acted as reinforcing fillers in relation to Young's modulus and tensile strength.

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Os resíduos sólidos urbanos (RSUs) são atualmente um dos maiores problemas ambientais, por serem gerados em grande quantidade e ocuparem extensos espaços por um longo período, resultando na diminuição do tempo de vida útil dos aterros sanitários. Os polímeros constituem um grande percentual da composição do RSUs, sendo que as embalagens plásticas contribuem com maior volume e massa. Apesar da reciclagem de polímeros estarem se consolidando no Brasil, graças ao seu mercado ascendente e promissor, existem ainda restrições quanto a sua utilização em contato com alimentos devido aos eventuais processos de migração de contaminantes que podem ocorrer da resina reciclada para o alimento. Por outro lado, dados recentes do setor indicam que a maior parte do consumo de resina virgem é destinada, justamente, para o mercado de embalagens alimentícias. Assim, o desenvolvimento e o gerenciamento de tecnologias que possibilitem o retorno destes materiais a sua aplicação original é de grande importância para sociedade contemporânea. Em um panorama geral, este trabalho aborda as exigências e limitações do uso de polímeros reciclados para contato com alimentos.

The aim of this work is to investigate the degradation of low molar mass poly(ethylene terephthalate) (PET)/organically modified montmorillonite (OMMT) clay nanocomposites prepared by melt processing. The rheological behavior in combination with transmission electron microscopic images suggests an intercalation and therefore a percolating network. Furthermore, the results indicate that the increase of organoclay content caused a degradation of PET during processing of PET/OMMT nanocomposites, once it was observed the PET molar mass decreases. The effect mentioned could be attributed to an increase of Brønsted acidic sites on the platelet surface, which is produced by the Hofmann elimination reaction of ammonium, and also the presence of residual metal compounds on clay surface might possibly favored the polymer matrix degradation process.

Polypropylene nanocomposites were prepared with organic‐modified montmorillonite, by blending the polymer and the organoclay (direct addition), or by blending the polymer with an organoclay/silicone copolymer masterbatch. The effect of the organoclay/silicone copolymer masterbatch on the morphology and properties of polypropylene was compared with that nanocomposite obtained with the direct organoclay addition. The results showed that the morphology of both polypropylene nanocomposites is constituted by clay tactoids together with some few individual platelets and clay aggregates. Smaller tactoids were observed for the nanocomposite prepared with the masterbatch, in which the silicone copolymer remained intercalated in the clay or adjacent to tactoids. The introduction of the organoclay in the polymer matrix resulted only in an increase in the Young's modulus (28%), while yielding stress, elongation at break and Izod impact strength remained practically unchanged. On the other hand, the incorporation of organoclay by using the masterbatch resulted in a marked improvement (111%) in the elongation at break and in Izod impact strength (85%). The improvement in the elongation at break came with the reduction of the modulus and the yielding stress, by 25 and 15%, respectively. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers