Surface Functionalization Of Attapulgite And Halloysite, And Properties Of Their Composites

Attapulgite (ATP) with fibrous crystal structure and halloysite (HNT) with hollow tubular structure, which belong to one-dimension nano-materials, are natural hydrosilicate clay minerals. They have been intensively used as perfect carriers, template, adsorbents, reinforcements and so forth due to their abundance, low cost, unique structures and particular properties. Firstly, the surface functionalization of attapulgite, and attapulgite-based polymeric composites and their potential applications are investigated according to the crystal structure of attapulgite. Secondly, the composite nanotubes and hollow sodalite nanosphere are presented respectively. The main content was concluded as follows:1. The porosity of attapulgite and its special one-dimension characteristic were utilized to improve effectively the whole application performance of urea-formaldehyde resin. The influences of attapulgite before and after modified using y-ureidopropyltriethoxysilane on the free formaldehyde content of the shear strength of urea-formaldehyde resin composites were discussed. The addition amount of modified attapulgite was determined. The results showed that the modifier was grafted onto the surface of attapulgite by chemical bonding. The free formaldehyde content of the composites was less than 1% and the shear strength was double of that of the pure urea-formaldehyde resins when the optimum dosage of modified attapulgite was 9% of net formaldehyde and urea (in total mass). In addition, the thermal property and the crosslinking degree of the composites were improved.2. The core-shell structure attapulgite/polythiophene composites were prepared by chemical oxidative polymerization of attapulgite nuclear body with thiophene. The obtained composites were doped in iodine vapor to create the porous attapulgite-polythiophene conductive composites. The results suggested that the iodine ion (I3-) entered the polythiophene molecular chains so as to largely improve the conductivity of the composites (volume resistivity:from 4.89×106 to 2.44×102Ω·cm). The doping of iodine not only transform the attapulgite/polythiophene composites into the porous attapulgite-polythiophene composites but also change the crystal structure of attapulgite. The BET surface area, BJH average pore size and BJH cumulative pore volume were improved.3. The changes of hydroxyl amount on the surface of attapulgite under the acidification and the influences of hydroxyl amount on morphology of attapulgite/polypyrrole composites were examined respectively. The results revealed that the surface property (concentration of active groups) of attapulgite had important impacts on the modulated morphology of attapulgite/polypyrrole composites. The pristine attapulgite is prone to form the rod-sphere composites while the modified acid-attapulgite is beneficial to generate the rod-film composites with core-shell structure. The rod-film attapulgite/polypyrrole composites have preferable electrical conductivity compared with the attapulgite/polyaniline and attapulgite/polythiophene composites. The attapulgite/polypyrrole composites can from consecutive space network in acrylic coatings and improve mechanical property. The amount of attapulgite/polypyrrole composites is far smaller than that of the sphere-like polypyrrole to form the same surface resistivity.4. The halloysite-polyaniline-polypyrrole composites were fabricated using halloysite as hard-template by self-assembly method, and then the polyaniline-polypyrrole binary nanotubes were gained by the removal of template as well as the secondary doping for the halloysite-polyaniline-polypyrrole composites. The results showed that the secondary doped polyaniline-polypyrrole binary nanotubes had lower internal resistance and specific capacitance compared with the halloysite-polyaniline-polypyrrole composites.5. Sodalite nanospheres with hollow mesopores (sodalite-HMNS) were facilely fabricated by one-pot template-free hydrothermal method using natural halloysite as silicon-aluminum source. The phase transition of the products and their drug release behavior was further investigated. The results showed that hollow mesopore sodalite nano-spheres with the inner pore diameter of ca.18 nm are prepared Sodalite-HMNS gradually transform to micro-nepheline with long time reaction. Hollow mesopore sodalite nano-spheres have good sustained drug release performance.