Calcite resin

Calcium carbonate is the most commonly used extender. It is widely available and low in cost, and it provides for improvements in certain performance properties. The material is a mineral that is mined throughout the world. Common forms of calcium carbonate include limestone, marble, calcite, chalk, and dolomite. It is manufactured by precipitation processes and is commercially available from a number of sources. Calcium carbonate is available in many different particle sizes and in various grades. To improve dispersion in certain resins, the filler is often coated with calcium stearate or stearic acid. 

It is well known that organosilicon compounds do not become equally well attached to all mineral substrates. While silicates always readily lend themselves to coating with silane and polysiloxane [19-21], the same cannot always be said of calcium carbonate [19, 20]. Calcium carbonate (calcite), a widely used filler, is generally considered difficult to cover with silanes. Given the proven, good attachment of silicone resin to calcium carbonate fillers in silicone resin emulsion paints [2, 22], the question arises as to whether only higher polymeric siloxanes are able to form hydrophobic protective coatings on calcium carbonate. 

The silicone resin network (polymethylsilicic acid) coats the surfaces of both large calcite grains and small titanium dioxide particles with an ultra-thin veil-like film. Clear evidence of an existing network coating is the apparent rounding and void filling just a few nanometers thick (Figs. 3b,d) between the mineral phases (white arrows). 

To compare the bonding behavior of silicone resins bearing either methyl or wo-octy 1 side-chains to quartz and calcite crystal surfaces, the investigations were performed on small cyclic Sig-siloxane molecules, Sig-cage-type silsesquioxanes, and ladder-type siloxanes [75]. 

Methyl silicone resin networks have been shown to cover all substrates equally well. However, the way in which the network is attached is fundamentally different in each case, which could have repercussions on the durability. As is known from the literature on quartz and calcite surfaces, reactive hydroxyl groups exist that will react with siloxanes. This means that for a high-molecular resin with a reasonable degree of conformational freedom a sufficient number of reactive hydroxy groups at suitable distances can be found on the mineral surfaces. In contrast, the quality of binding is different in quartz (covalent Si-O-Si bridge) and calcite (Ca-O-Si interaction), which will influence long-term stability. 

Thin sections were prepared /or 28 samples following impregnation with blue-dye epoxy resin, and stained for calcite and K-feldspar using alizarin red S and potassium ferrocyanide, respectively. The thin sections were systematically scanned by the senior author to determine rock composition, porosity and textural relationships. 

Maceration was used principally for skin creams and perfumes owers, herbs, spices, or resins were chopped up and immersed in hot oils. The oil was strained and poured into alabaster (calcite) containers and sealed with wax. These scented fatty extracts were also massaged onto the skin (Manniche, 1999). 

Figure 15 FT-Raman spectra of fake ivory specimens (a) carved X ctorian bangle, (b) large bangle, (c) small bangle, (d) cal. The absence of the characteristic proteinaceous features in true ivory near 1650 and 1450 cm and the strong phosphate mode near 960 cm" should be noted. Also, the presence of the aromatic ring bands at 3060, 1600, and 1000 cm" in (b) and (d) indicate a polystyrene resin content, whereas the carbonyl stretching band at 1725 cm" in all fake specimens indicates the presence of poly(methyl methacrylate). In the cat specimen, the band at 1086 cm uniquely identifies a calcite additive in the specimens of imitation ivory studied. (Reproduced with permission from HGM Edwards, DW Farwell. Ivory and simulated ivory artifacts Fourier-transform Raman diagnostic study. Spectrochimica Acta, Part A, 51 2073-2081. 1995, Elsevier Science B.V.)...

Figure 3 Ivory cat, which was identified spectroscopically as a modern limitation composed of poly(methyl methacrylate) and polystyrene resins with added calcite to give the texture and density of ivory. Reproduced with permission from Edwards HGM and Farwell DW, Ivory and simulated ivory arte cts Fou-rier-transform Raman diagnostic study, Spectrochimica Acta, Part A, 51 2073-2081 1995, Elsevier Science B. V. (See Colour Plate 3).

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