Modification of fibrous silicates surfaces with organic derivatives: An infrared spectroscopic study

Abstract

This contribution explores the interaction of the fibrous silicates, palygorskite, sepiolite and chrysotile with a wide range of organic agents. Infrared spectroscopy (IR) methods are essential for the characterization of solid surfaces and for the investigation of the kind of bonds formed between the surface of these silicates and the organic moieties. Thus, when sepiolite or palygorskite are treated, e.g., with polyurethanes, alcohols, isocyanates, amines or pyridines, specific SiNHC or SiOC bonds are derived from the linkage of the differently located OH groups in these fibrous silicates with the organic moieties. On the other hand, more stable, covalent SiOSiC bondings are formed when the fibrous silicates, especially chrysotile, are reacted with heterofunctional silylating agents like chlorosilanes or ethoxysilanes carrying, alkyl, alkenyl or aryl groups. Such reactions may occur in the presence or absence of HCl. An absorption band at 960 cm(-1)--which we assigned to SiOH groups--is detected only in the presence of HCl. The evolution of this band is related to the degree of grafting of the organic radicals with the silanol groups of the silicates. HCl-generated silanol groups are the main bridges for the coupling of organosilyl groups on chrysotile and other silicates by covalent bonding, leading the way to the preparation of interesting new materials, including fibrous sheet polymers.

Tailoring surface properties and structure of layered double hydroxides using silanes with different number of functional groups

“…As shown by this study, silane modification can not only increase the pores volumes as in H-Si 1 and H-Si 2 , but also create new type of mesopores as in H-Si 3 and H-Si 4 (Fig. 6b).…”

“…Silylation, also known as silane grafting, has been proven to be an efficient method to modify inorganic materials [1][2][3][4]. Comparing with surfactant intercalation, silylation enables a durable immobilization of the organic moieties by forming covalent bonds between silane and substrates.…”

The increase of surface area of a Brazilian palygorskite clay activated with sulfuric acid solutions using a factorial design

“…Another study found that the band at 960cm -1 could be attributed to Si-O-H vibration, present in activated palygorskite 22 . The present study encountered this band between 970 cm -1 and 978 cm -1 .…”

Rod like attapulgite/poly(ethylene terephthalate) nanocomposites with chemical bonding between the polymer chain and the filler

“…Attapulgite (AT) is a crystalloid, hydrous magnesium-aluminum silicate mineral, which is received as a randomly oriented network of densely packed rods. A fibrillar single crystal is the structural unit, with 20-30 nm in diameter and 0.5-2.0 µm in length [14][15][16]. Owing to the low price, relatively high surface area, good mechanical strength and thermal stability, AT is attracting more and more attention in the preparation of polymer/clay composites [17][18][19][20].…”