Slide 1

BindersMolecule type Intermolecular interactions Tempera (egg yolk)Protein, fat/oil, lecithin Gum arabicpolysaccharide Drying oils Acrylics Lipids (oils) polymers Mixed (H-bonding, dipole interactions, hydrophobic interactions) H-bonding hydrophobic

Slide 2

A polysaccharide: poly sugar These OH groups bond with water Gum Arabic: A polysaccharide: poly sugar Gum on acacia tree Gums: soluble in water; form viscous (mucilinous) "solutions"; of C, H and O only. Are typically organic carboyhydrate acids as Ca, Mg or K salts.

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Drying oils: lipids 5 Views of Linoleic Acid = C 18 H 32 O 2 2 unsaturated bonds (2 double bonds) Carbons only Carbons and Hydrogens Note bend: due to Double bond

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Other drying oils: Linoleic Acid = C 18 H 32 O 2 : 2 unsaturated bonds (2 double bonds) Oleic = C 18 H 34 O 2 Linolenic = C 18 H 30 O 2 1 unsaturated bonds (1 double bonds) 3 unsaturated bonds (3 double bonds)

Slide 5

The drying reaction: Drying is not just evaporation of solvent (like fresco drying wasn't). Is a chemical reaction: oxidation (here, addition of O 2 ); Double bonds are reactive (unstable) and that is where O 2 adds Oxidation by O 2 can be catalyzed by Co, Mn other metals (siccants)

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Acrylics: are polymers monomer unit = Acrylic Acid: CH 2 =CHOOH picture of polymer Methyl Methacrylate: monomer unit CH 2 =C(CH 3 )COOCH 3

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Tempera (egg yolk): Protein, fat/oil, lecithin Oil / fat

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Tempera (egg yolk): Protein, fat/oil, lecithin lecithin Fatty acid

Slide 9

Tempera (egg yolk): Protein, fat/oil, lecithin lecithin Fatty acid Example of protein

Slide 10

So whats the bottom line regarding binders? Theyre all BIG molecules Theyre all organic molecules Theyre most often bio molecules They bind using Intermolecular Forces