COLOUR RETENTION

On the other hand, not only initial colour but colour change (discolouration) of the resin under UV light and heat is important. Colour retention of a resin is related to the chemical stability and increases as the degree of non-aromatic conjugated unsaturation of the resin molecule decreases. Thus, for rosins a high level of abietic-type resin acids lead to relatively unstable resins. Hydrogenation and disproportionation as well as esterification provide improved stability and colour retention to rosins. 

Post moulding operations Finishing - painting. Paint chips off easily Finishing - not required -painting not required. Compounded colour retention permanent. 

In considering exposure tests, whether in the form of laboratory, field or service tests it is important to consider the purpose of the test and the relevance of the data to the anti-corrosion function of the coating. Thus, in the case of paint coatings, factors such as gloss deterioration, chalking and colour retention are of considerable importance in some industries, for example the automotive industry, but perhaps of minor importance in the painting of structural steelwork. These assessment factors can nevertheless be of significance since they may be the precursors of corrosion of the basis metal. 

Rocha, T., Lebert, A., and Marty-Audouin, C., Effect of pretreatments and drying conditions on drying rate and colour retention of basil (Ocimum basilicum), Lebensm.-Wiss. u. TechnoL, 26, 456, 1993. 

Figure 4.17 New nanobinder Col.9 combines in one product the advantages of conventional coating types in terms of low dirt pick-up, chalking and rack resistance, and colour retention. (Reproduced from Col.9.com)...

Polyamine-cured epoxy systems have reasonable colour and colour retention, improved physical properties and good chemical resistance. They are, however, moisture sensitive, relatively toxic and have poor resistance to organic acids. Examples of this class are diethylene triamine (DETA) and triethylene tetramine (TETA). 

Methacrylate-based coating resistance to ultraviolet radiation chemical resistance permeability to water vapour carbon dioxide resistance colour retention anticarbonation coatings for concrete and masonry... 

MacDougall, D. B. and A. A. Taylor. 1975. Colour retention in fresh meat stored in oxygen—A commercial scale trial. Journal of Food Technology 10 339-347. 

Although more expensive, saturated polyester resins have better colour retention and water-resistance. Ether linkages are water-sensitive (diethyl ether, C2H3 0 C2H5, is partly soluble in water) and in polyethers they are repeated throughout the polymer chain without the separation by long, water-insensitive hydrocarbon chains which could offset their effect. 

Appearance Transparency Surface finish Colour matching and colour retention... 

A food-grade oleic acid has been produced commercially from tall oil. The main uses of tall oil fatty acids are as intermediates in the production of oleochemicals and as components of alkyd resins. The absence of linolenic acid conveys good colour retention and non-yellowing properties for protective coatings. 

PDBS-80 was the first in the series. This material is a homopolymer of dibromostyrene that contains 59-60% bromine. Its primary applications are in high-temperature polyamides and polyethylene terephthalate (PET) because it has excellent flow characteristics and very good thermal stability. In addition, there are benefits of excellent colour retention. The main weakness of this approach is the bromine content relative to the competitive material. Today s competition contains around 68% bromine. This can translate into a 2-3 parts difference in the load level needed in the protected polymer to give equivalent flame retardancy. 

PVC compounds in the window profile industry can usually accept ordinary calcium carbonate dose levels of only about 8%. But the favourable particle size distribution obtainable at the new Omya facility at Melton, on Humberside, UK, means that loadings of up to 15% are feasible, and 10% or 12% levels do not affect strength or gloss too much. Flowability and colour retention properties are also said to be excellent, and the availabiUty of these new grades is claimed to enable PVC compounders to lower their costs. 

Solid ingredients in a coating (that hold pigment particles in suspension and attach them to the substrate), which consist of resins (oils, alkyd, latex), the nature and amount of which determines the paint s performance such as its washability, toughness, adhesion, colour retention, etc. 

---