Variability of the surface properties of sepiolite

Preparation and characterization of fibrous sepiolite modified silane coupling agent/fluororubber nanocomposite

“…According to this figure, compared to pure FKM compound, the whole curing velocities of Sep/FKM compounds are both increased via the addition of different fibrous sepiolites, with the increase of these max torques, the apparent crosslinking densities are both raised; meanwhile, contrast to aSep/FKM compounds, the CRI of oSep/FKM compounds are lower, while their max torques are upper. It is analyzed that there are many different tunnels in sepiolite crystals, among the crystals and among the bundles [17,18], they can absorb FKM chain segments by physical method, thereby the curing velocities are raised by the addition of Sep; while the interaction among the bundles partially disappears by organic modification, the tunnels in the aggregations reduce. During the whole curing history, physical coupling action happens between the matrix and oSep, meanwhile the chemical reaction may occur between rubber macromolecule and other terminal groups of the coupling agents on the surface of the bundle, two actions further promote the curing reaction, so the apparent crosslinking densities of oSep/FKM composites are increased.…”

“…The sepiolite is the needle-like fiber of layered silicate, there are parallel pore channels in its crystal, bundle, and aggregation [16]. After the exfoliation, nature sepiolte presents fibrous bundle and aggregate, which have particular surface structure and oriented pore channels [17], these structures could improve adhesion between filler and polymeric matrix [18]. Meanwhile, the surface treatment of sepiolite could enhance its compatibility with polymers [19][20][21].…”

“…1, it is shown that the calcite has been absolutely decomposed, fibrous aggregations of sepiolite have been exfoliated from the mixture of minerals, these apparent diameter and length are respectively 100-200 nm and 1-5 lm from Fig. 2b, and the crystal morphology is well, so these aggregations may be combined of four to eight bundles, and there are some tunnels between the bundles [18]. It is illustrated that mineral particle of sepiolite is the combination of calcite and sepiolite.…”

Effect of the irradiation dose on the luminescence emission of a Mg-rich phyllosilicate

“…Supergenic sepiolite is found as a secondary mineral associated with serpentine and sedimentary sepiolite and appears linked to opal and palygorskite, e.g., in the Tagus river basin in which we collected samples (Batallones hill, Madrid). The sepiolite structure is formed by (i) tetrahedral silicon sheets, with an apical oxygen inverted, bound to octahedral magnesium sheets (typical T-O-T structure of phyllosilicates) [11,12], (ii) tunnels in the inner of the particle and (iii) channels (open tunnels in the external surface) [13,14]. This clay can be formed by hydrothermal processes or by sedimentation [15], although the most accepted mechanism for its formation is by the direct precipitation from solutions containing silica and magnesium [16].…”

Asbestiform sepiolite coated by aliphatic hydrocarbons from Perletoa, Aosta Valley Region (Western Alps, Italy): characterization, genesis and possible hazards

“…Almost all commercially sold specimens have fibres < 5 m long -the threshold of non-carcinogenicity accepted by the International Agency for Research on Cancer, World Health Organization (1997) -sometimes as the result of preliminary grinding. However, sepiolite occurrences from all over the world show high variability in cristallinity, fibre length and texture (Suárez and García-Romero, 2012;García-Romero and Suárez, 2013); samples with unusually long fibres (> 10 m) were seldom identified and signalled for their carcinogenic potential (Pott et al, 1990;Pott et al, 1991;Bellman et al, 1997).…”