Functional silane‐modified calcium carbonate

Abstract

SynopsisIn the course of graft polymerization of styrene on a calcium carbonate powder surface treated with a silane coupling agent such as y-methacryloxypropyltrimethoxysilane, gelation of the reaction mixture was observed just as on silane-modified clay. Infrared spectroscopic and gel-permeation chromatographic studies have revealed that the extracts of styrene monomer from the powder surfaces contained polymeric silane coupling agent, having crosslinking ability, besides monomeric silane coupling agent. The catalytic effect on the condensation of the silane coupling agent on the powder surface was found to be increased in following order: CaC03 < P-CaC03 < clay, where P-CaC03 is a calcium carbonate modified with phosphoric acid. The order was parallel to the gelation tendency and to the acidity order (Ho 2 6.8) on the surfaces. Direct evidence for bonding between the silane coupling agent and the phosphate moiety on calcium carbonate was not available; however, the silane-modified P-CaC03 filler exhibited more reinforcing effects in peroxide-cured ethylene-propylene-diene rubber (EPDM) and in sulfur-cured styrene-butadiene rubber (SBR) than the silane-modified calcium carbonate. These reinforcing effects are also discussed in relation to the molecular weight distribution of the silane coupling agent extracted.

Investigation of the modification process of natural sedimentary calcite by organosilicon compounds

“…Similar problems arise with the use of stearic acid with mediumpolar filmforming agents for paint and varnish materials. Similar results are obtained when surface treatment with silane modifier in the presence of phosphoric acid [7].…”

Silane pre-treatment of calcium carbonate nanofillers for polyurethane composites

“…Structure and properties of the silane interface depend on the conditions during the modification process (concentration of the solution, solvent, pH of the aqueous slurry of the filler), the specific surface area of the filler, and alkoxy-and organo-functionality of the silane [9,[14][15][16][17][18]. In general terms it is believed that the silane layer consists of a mixture of chemisorbed and physisorbed material.…”

“…The chemisorbed material can be further subdivided into (i) a surface monolayer: its structure depends critically on the surface of the substrate and on the nature of the organofunctional groups, i.e., its ability to interact with the surface. Above this there is (ii) a layer of tightly bound material and further out (iii) more loosely bound structures [9,[14][15][16][17][18]. Additionally, silane on the filler surface can form an open high-molecular ladder-type polysiloxane network or low-molecular-weight polycyclic structures depending mostly on the organofunctionality of the silane [14][15][16][17][18][19].…”

“…Modifications of silica, silicates, oxides and hydroxides with trialkoxysilanes were successfully applied [9]. Calcium carbonate filler does not contain surface hydroxyl groups and silanes are generally not found to be effective on surfaces of this filler [9,[16][17][18]. According to Ishida [16] the surface acid/base properties (pH of aqueous slurry) influence on the structure of the adsorbed silane.…”

“…The chemisorbed layer on neutral substrates was identified as highly condensed poly(methacryloyloxypropylsilsesquioxane)s exhibiting extensive Si-O-Si networks, which makes their removal and dissolution extremely difficult. Nakatsuoka et al [18] have investigated the surface treatment of calcium carbonate filler with γ-methacryloyloxypropyltrimethoxysilane. The physisorbed layer on the calcium carbonate surface consisted of mostly monomeric silane.…”