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Montmorillonite with dimethyl di(hydrogenatedtalloyl) ammonium as the compensating cation was added to a silica based elastomeric composite and the hybrid filler system led to reduction of filler networking phenomenon, better stability of elastic modulus with temperature, enhancement of stresses at all elongations, improvement of ultimate properties. This composite was based on a blend of natural rubber, poly(1,4-cis-isoprene) and poly(styrene-co-butadiene) from anionic polymerization and contained 70 parts per hundred rubber (phr) of silica. The organically modified clay (OC) was below the threshold required to establish an hybrid OC-silica filler network. Such threshold (about 7 phr) was estimated by preparing silica based nanocomposites containing various amounts of OC and determining shear storage and loss moduli as a function of strain amplitude. This work demonstrates that exfoliated OC favour lower dissipation of energy of silica based elastomeric composites under dynamic mechanical stresses and paves the way for further large scale applications. (C) 2016 Published by Elsevier B.V.

Layered double hydroxides (LDHs) containing Mg2 + and Al3 + as divalent and trivalent cations, respectively, have been synthesized by a procedure based on hydrolysis of a mixture of metal alcoholates, and have been characterized mainly by Wide Angle X-ray diffraction (WAXD) and Fourier Transform Infrared (FTIR) measurements. The used procedure is suitable to prepare LDHs with Al molar fractions, xAl = Al/(Al + Mg), as low as 0.1. The same LDH preparation procedure, for xAl

Montmorillonite (Mt) and Mt organically modified (OMt) with dimethyl ditalloyl ammonium cations were delaminated through ball milling. X-ray diffraction (XRD) analysis allowed the observation a more efficient delamination for OMt than for Mt. In fact, 90% delamination was obtained for OMt, without appreciable variations of the in-plane Mt order. About 60% delamination was obtained for pristine Mt, in the presence of a substantial reduction (up to 40%) of crystalline order in the structural planes. A reflection due to the rotator order of talloyl chains was found both in pristine and in extensively delaminated OMt samples. Polymer nanocomposites based on poly(1,4-cis-isoprene) were prepared with two types of OMt: OMt, unmilled, with the ammonium cation intercalated in the interlayer space (I-OMt) and 90% delaminated OMt (D-OMt). XRD analysis of clay polymer nanocomposites (CPNs) revealed the unaltered crystalline order of I-OMt and a nearly complete maintenance of the delaminated structure of D-OMt. Dynamic-mechanical characterization of CPN gave counterintuitive results. I-OMt revealed a higher tendency to give rise to the filler networking phenomenon, in samples crosslinked with a sulfur based system. Moreover, I-OMt gave rise to a more pronounced extension of the rubbery plateau at low frequencies, in uncrosslinked masterbatches. This behavior is attributed to the higher volume fraction of I-OMt, as the intercalated alkylammoniums contribute to the I-OMt volume, whereas they essentially act as compatibilizers in D-OMt. Delamination of OMt is thus presented as a powerful tool to reduce the dissipation of energy in dynamic-mechanical applications of polymer melts and elastomers.

An innovative organoclay containing polybutadiene chains was prepared in order to make rubber nanocomposites based on natural rubber or styrene–butadiene copolymer. It was obtained by reacting a maleinised polybutadiene oligomer with the CH 2 CH 2 OH moieties present in the ammonium cation of a commercially available organoclay (Cloisite 30B). Elastomeric nanocomposites were also prepared with a reference organoclay, formed by intercalation during mixing with dialkyl dimethylammonium chloride. Sulphur cured nanocomposites were characterised in terms of curing kinetics, morphology, tensile and dynamic-mechanical properties; chemical interactions between the modifier of the new organoclay and the matrices can be inferred by experimental evidences.