Binding Materials for Pastes Life Cycle and Sustainability of Abrasive Tools

Binders for pastes include the following [MARI04, p. 442 f., BORK92, p. 24]:

• Stearin—stearic acid, CH3(CH2)16COOH, white, solid, crystalline substance, melting point of 140 °C; Stearin is a good binder and brings cohesion and hardness to the paste.

• Oleic acid—olein, unsaturated fatty acid, melting point of 15 °C; Oleic acid accelerates the polishing process by dissolving metal oxides.

• Paraffin—waxy, crystalline mixture of fatty hydrocarbons, melting point of 44 ° C; Paraffin does not likely convert into a resin or carbonize. It brings cohesion, elasticity, hardness, and adhesion to polishing pastes.

• Fats—Organic, fusible glycerides of saturated fats and unsaturated oils; Fats are often used instead of stearin.

• Wax—Solid, unctuous or liquid fatty acid esters with higher fatty alcohols; Examples are carnauba plant wax (melting point 353-359 K), beeswax (melting point 333-340 K), and montan wax (melting point 351-353 K). Waxes provide hardness and cohesion to a paste.

• Petroleum jelly—petrolatum, obtained from asphalt less paraffin-base crude oils; This substance reduces the hardness of a paste.

Surface-active substances and emulsifiers are sometimes added to polishing pastes. Their tasks are to intensify the machining operation and to increase

durability of the abrasive compound. Thixotropic substances (including aluminum soaps, aluminum alcoholates, complex bentonite, and fine talc powder below 1 ^) are added to fluid pastes to increase viscosity [MARI04, p. 443]. For example, in glass polishing the fluid has a large effect on the tribological effects and material removal process [HAMB01, p. 127].

Polishing with pitch is used to finish high value optical components. Pitch is a viscoelastic material and primarily derived from either pine tree resins or petroleum-based resins [MULL08].

4.4.1 Counterparts

A large variety of counterparts or polishing pads is available with a lack of application based models [DAMB05, p. 30]. Three main types for counterbodies can be distinguished [KHAL79, DAMB05, p. 30]:

• Deformable polishing pads, such as pitch or cast polyurethane,

• Soft polishing pads, such as cloths and synthetic felt with porous structure,

• Hard polishing pads, such as hard felt, filled or not filled polyurethane foam, impregnated cloths, fine laminates.

The choice of the pad affects the material removal rate. Hambuecker [HAMB01, p. 126], for example, showed that polyurethane foam is superior to pitch pads in automated glass polishing.

Binding Materials for Pastes
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