One of the most usual applications is their incorporation into organic materials. Nonetheless, natural clays are hydrophobic being incompatible with organic medium. Clay organophilization can be reached by several methods such as by exchange of the interlayer sodium cations by organic cations, and by silanization of the clay layers. In this study the bentonite clay was organophilized by the addition of the methoxymethyltriphenylphosphonium chloride (CTFF). Further, the organoclay was silanized with (3-glycidyloxypropyl) trimethoxysilane (GPTMS). X-ray fluorescence results, infrared and XPS spectroscopy showed the presence of phosphorus in the organophilic clay. The interlayer space, obtained by X-ray diffraction, increased in 55% after the CTFF addition showing the cationic exchange in the clay lamellar region. After the silanization of the organoclay the interlayer space was slightly reduced from 1,78 nm to 1,72 nm, indicating that the silane molecules were preferential bound in the clay edges.Keywords: organoclay; bentonite; silane; quaternary phosponium salt. INTRODUÇÃOA argila é definida como um material terroso, de granulação fina, apresenta alta plasticidade em água 1-3 e é formada pelo empacotamento de lamelas cristalinas.1,3-5 A bentonita uma das argilas de maior interesse tecnológico, 3,6,7 apresenta em sua configuração cátions interlamelares, que podem ser trocados por cátions orgânicos ou inorgânicos quando presentes em solução aquosa, influenciando suas propriedades físico-químicas e alterando seu espaçamento basal, essa propriedade é chamada de capacidade de troca catiônica (CTC). [2][3][4]8,9 O termo bentonita é comumente usado para designar argilas constituídas principalmente por argilomineral ou argilominerais esmectíticos, sendo o argilomineral mais frequentemente encontrado a montmorilonita. Essa classe de argilas é constituída principalmente por silicatos de alumínio e magnésio do tipo 2:1, no qual uma folha octaédrica está entre duas folhas tetraédricas. Esse silicato possui deficiência de cargas positivas em sua estrutura cristalina, resultando em excesso de cargas negativas, que é contrabalanceado por cátions interlamelares alcalinos, Na+ ou K+. A montmorilonita é caracterizada pela sua capacidade de troca catiô-nica, que permite que os cátions inorgânicos sejam substituídos por cátions orgânicos, aumentando seu caráter apolar, e possibilitando sua incorporação em meios orgânicos.3 Após a troca catiônica as argilas são denominadas argilas organofílicas ou organofilizadas, e a partir dessas é possível se obter complexos argila-compostos orgânicos.2,10 As argilas organofilizadas são mais facilmente incorporadas em sistemas orgânicos, como em cosméticos, tintas à base de solventes orgânicos, polímeros apolares e lubrificantes. A substituição de cátions de sódio por cátions orgânicos, em geral, causa um aumento da distância basal da argila, o que pode ser observado pela técnica de difração de raios-X (XRD) e, usualmente, quanto maior a cadeia orgânica do sal maior será a distância interlamelar ...

Epoxy nanocomposites are promising for adhesive applications due to their high performance. In this work, an organoclay (PO), prepared by cationic exchanging using a quaternary phosphonium salt or a silylated PO (SPO) was added to an epoxy‐amine resin‐based adhesive to reduce its dripping. PO and SPO were dispersed in the epoxy network on a nanometric scale, mainly in an intercalated structure. A liquid‐to‐gel transition occurs at 4–6 wt% PO due to forming a continuous organoclay network throughout the epoxy volume, eliminating its dripping. The PO addition accelerates the curing reaction initially, and cured nanocomposites with over 3 wt% PO show a drastic reduction in the glass transition temperature (Tg). Moreover, a broadening of the secondary relaxation observed by DMA indicates an interaction between the epoxide‐amine oligomers with the silicate surface. This interaction, associated with forming a continuous organoclay network at 4–6 wt% PO, reduces the epoxy‐amine oligomers diffusion, resulting in their partial curing and consequent Tg decreasing. EPOXY_SPO nanocomposites show Tg values similar to or higher than that observed for the epoxy‐amine network attributed to the forming of covalent bonds between the glycidyloxypropyl end groups in the SPO surface and the hardener amine.

Natural rubber (NR) is vulcanized with three different systems, using sulfur, peroxide and a mixed system consisting of peroxide and sulfur. The viscoelastic behavior of rubbers is evaluated by Dynamic Mechanical Analysis (DMA), using constant or multiple frequencies. From both DMA analysis methods, it is possible to verify that the rubbers vulcanized with sulfur or with the mixed system presented superior storage modulus in the rubbery region, and higher Tg values compared to the rubber vulcanized with dicumyl peroxide. These results indicate a higher degree of crosslinking for the NR containing sulfur in its vulcanization system. The master curves show that the rubber vulcanized with sulfur presented relaxation at a lower frequency due to the higher hardness, which is a consequence of the higher degree of crosslinking.

No abstract