Polyester resin

Polyester resins are condensation products of dihydric or polyhydric alcohols (e.g., glycols or glycerol) and dicarboxylic acids. In contrast to the chemically related alkyd no long-chain fatty acids are used in the preparation. UP stands for unsaturated polyester resins, which are used for producing fiber-reinforced plastics, fillers or casting resins.

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Properties

Physical Properties

The cured resin is typically clear, but may also appear cloudy to opaque. The hardness depends on the composition and is therefore in a wide range (from very soft to hard ) variable. As can be achieved with the aromatic carboxylic acids and / or tri-or tetravalent alcohols hard products, aliphatic carboxylic acids and / or long-chain dihydric alcohols resulting soft polyester.

Chemical Properties

Polyester resins are substantially resistant to weak acids and bases, as well as fuel and oil. However, they dissolve in strong acids and alkalis as well as in esters, ketones and chlorinated hydrocarbons. In particular their use as paint binders, they are dissolved in organic solvents and are used as a carrier for the coloring pigments. Polyester resins form a long, straight-chain polymers, but which may also be crosslinked. For this purpose, so-called functional groups are incorporated in the molecule, which cross-link and cure, for example, with isocyanate. Unsaturated polyester resins contain double bonds, which are cured with styrene or other reactive with the aid of peroxides (e.g., dicumyl peroxide, dibenzoyl peroxide or methyl ethyl ketone ).

Brennprobe: Polyester resins burn with bright yellow, sooty flame, being char. Outside the ignition source they continue to burn. During combustion of unpleasant-smelling degradation products (Attention, harmful ).

Processing

  • Pressing and injection molding
  • Laminate, eg with glass fibers (see fiber -plastic composite, glass fiber reinforced plastic and gel coat )
  • In a mixing process with pigments and additives to paints for boat building or household use.

Application

The plastic they are used among other things for the production of heat-resistant and electro- insulated handles for pots and iron. In addition, using polyester resins for the manufacture of control cases and as an insulating material for coatings and for plastination. Some manufacturers of blades for wind turbines produce these glass fiber reinforced polyesters. Other applications: automotive parts, basement light wells, door panels ( in Europe uncommon ), drainage gutters, kitchen worktops, sinks, auto repair putty, pipes and much more.

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