Weathering epoxy resin

Bauer, R. S., Formulating Weatherable Epoxy Resin for Maximum Performance, Waterborne and Higher Solids Coating Symposium, New Orleans, 1982. 

Another commercially important aromatic glycidyl amine resin is trigly-cidyl isocyanurate (TGIC), which is discussed in the Weatherable Epoxy Resins section. 

The cycloaliphatic epoxy resins are characterized by the saturated ring in their chemical structure. They are almost water-white, very low-viscosity liquids. They provide excellent electrical properties such as low dissipation factor and good arc-track resistance, good weathering, and high heat distortion temperature. They are also free of hydrolyzable chlorine, sometimes present in DGEBA resins, which adversely affects certain electronic applications. 

Cycloaliphatic and heterocyclic epoxy have better weather resistance and less tendency to yellow and chalk than do aromatic epoxy resins. These resins possess excellent electrical properties and are often used in electrical and electronic applications. They are generally formulated into casting and filament winding compounds. 

Polysulfide resins combine with epoxy resins to provide adhesives and sealants with excellent flexibility and chemical resistance. These adhesives bond well to many different substrates. Tensile shear strength and elevated-temperature properties are low. However, resistance to peel forces and low temperatures is very good. Epoxy polysulfides have good adhesive properties down to -100°C, and they stay flexible to -65°C. The maximum service temperature is about 50 to 85°C depending on the epoxy concentration in the formulation. Temperature resistance increases with the epoxy content of the system. Resistance to solvents, oil and grease, and exterior weathering and aging is superior to that of most thermoplastic elastomers. 

The binders used in these ambient-cured formulations are generally low molecular weight reactive epoxy resins. These are cured with either amine or amine adducts to give the best chemical resistance, or with polyamide to give better water resistance, weathering and recoating properties (Dow Chemical Company, undated a). 

In the case of acrylic molding sheets and semi-fmished products, Wacker have elaborated a product concept based on silicone core-shell technology, which enables the manufacture of highly transparent particle-modified materials with improved RT and low-temperature (-40 C) impact resistance and high weatherability [4]. Other transparent plications (e.g., epoxy resins, polycarbonates) are showing encouraging results, too. 

Epoxy resins based on glycidylation of bisphenols, cresol and phenol novolacs, polycarboxylic acids, polyols, amines, and aminophenols have been long known. Epoxidized linear and cyclic olefins have also been used as specialty epoxy resins. More recently, glycidylated heterocycles have been introduced, initially as specialty resins promising improved resistance to weathering. One heterocycle in particular, the hydantoin ring, has become of particular interest as an epoxy substrate (J ). 

Desoto Corp. [124] patented a composition of an epoxy resin, specific polyol, and onium salt The composition, upon photocuring, gives a balance of hardness and modulus. Increased epoxy resin curing speeds by addition of a sensitizer to a sulfonium salt containing system was disclosed anonymously in 1986 [125]. Also in 1986, a photocurable composition having excellent thermal, electrical, and weathering properties, which consists of an epoxy resin and onium salt, was described by Daicel Chemical Industries [126],... 

In the photoageing of polycarbonates, photo-oxidation has been shown to be a more important process than the photo-Fries reaction. The photo-oxidation of epoxy-resins has been found to depend on the type of hardener and its concentration. A correlation has been observed between the changes in chemical structure and thermally stimulated current of poly(vinyl alcohol) during photo-oxidation. Other studies of interest include the weathering of polymers outdoors,effect of ozonation on polymers, effect of drawing, effect of biodegradation, and changes in mechanical properties of thermoplastics. ... 

Luwipal . [BASF AO] Melamine form-alddiyde resins combined with alkyd, polya late, and epoxy resins to give It.-resisL and weather-resist, baking finishes. 

The most widely used epoxy systems are those which are based on pure epoxy resins, hardened with a curing agent. Curing of epoxy resins containing two epoxy groups per molecule can be readily accomplished by the addition of primary polyamines, such as ethylene diamine, diethylene triamine, triethylene tetramine, tetra-ethylene pentamine, etc. Aliphatic polyamines produce cured resins with the greatest chemical resistance. However, these systems have inadequate durability, weather resistance and film-forming properties. They are sensitive to humidity, errors in addition rates are quite possible, and the catalysts are relatively toxic. 

Heterocyclic Epoxy Compounds. The technically most important heterocyclic epoxy resin is triglycidyl isocyanurate, obtained by reacting cyanuric acid with epichlorohydrin (Araldite PT 810, Ciba-Geigy Tepic, Nissan). This trifunctional epoxy resin is combined with carboxy-terminated polyesters to give weather-resistant powder coatings [2.122]-[2.124]. 

Powder coatings based on aromatic epoxy resins have high chemical and mechanical resistance, but are not resistant to weathering. To obtain weather-resistant powders, triglycidyl isocyanurate (Araldite PT 810, Ciba-Geigy Tepic, Nissan) must be used as the epoxy component with carboxy-functional polyesters. 

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