Color specifications, plastics coloring

AppHcation of an adhesion-promoting paint before metal spraying improves the coating. Color-coded paints, which indicate compatibiHty with specific plastics, can be appHed at 20 times the rate of grit blasting, typically at 0.025-mm dry film thickness. The main test and control method is cross-hatch adhesion. Among the most common plastics coated with such paints are polycarbonate, poly(phenylene ether), polystyrene, ABS, poly(vinyl chloride), polyethylene, polyester, and polyetherimide. 

A mixture of a measured amount of dye or pigment and a specific plastic material base. A more precise color can be obtained using concentrates than using neat colors. Note Care should be taken to verify that the color concentrate base is miscible with the plastic it is to color. Color concentrate may contain up to 60 wt% of... 

Several categories of paint are generally used for painting on plastic. Water-based acrylic paints provide no harmful solvents. They are easy to apply and have many color possibilities. Lacquers contain solvents that evaporate, allowing the paint coating to dry without chemical reaction. The lacquer must be carefully chosen to have a solvent that is compatible with the plastic being painted. Enamels are based on a chemical reaction that causes the coating film to form and harden. The effect of this reaction on the parent plastic part must be carefully noted. Table P.2 provides recommended paints for specific plastics. 

Testing of phthalocyanines includes crystallization (qv), flocculation, and appHcation in paints, plastics (qv), and printing inks (1). The ASTM standard specifications include CuPc in dry powder form for various appHcations (153). The specifications cover color (qv), character or tint, oil absorption, reactions in identification tests, and dispersions and storage stabiUty. Quantitative deterrninations are possible with ceric sulfate (30) or sodium vanadate (154). Identification methods are given (155), including tests for different appHcations. 

Paints are complex formulations of polymeric binders with additives including anti-corrosion pigments, colors, plasticizers, ultraviolet absorbers, flame-retardant chemicals, etc. Almost all binders are organic materials such as resins based on epoxy, polyurethanes, alkyds, esters, chlorinated rubber and acrylics. The common inorganic binder is the silicate used in inorganic zinc silicate primer for steel. Specific formulations are available for application to aluminum and for galvanized steel substrates. 

In USA the major obstacle to using plastics in the past has been to convert standards and codes to include the use of plastics. There were standards and codes where plastic would meet all their requirements with flying colors except when they specifically stated that the material to be used had to be iron, steel, or other material (not plastics). Eventually (years passed) and plastics were included. So plastics could not be used until other materials such as plastics would be included or no specific material was specified. Outside USA the changes in most cases were immediately particularly immediately after 1945. 

Soxtherm can be used for a variety of substrates, such as plasticisers, and additives in plastics and rubber, fibre and textile coatings, colorants on textiles, fat in food, oils and lubricants, fertiliser coatings, etc. Specific reports are scarce. EPA method 3541 has adopted automated Soxhlet extraction [151]. 

Recrystallization too is attributable to the pigment having a specific solubility in the plastic. As in other media, it is demonstrated primarily in a change of transparency or opacity in transparent colorations and in the depth of shade in white reductions. Lack of recrystallization stability becomes evident for example in the manufacture and processing of pigment-plasticizer pastes and in various polymers at elevated processing temperatures. 

In many cases pigment-plasticizer pastes are also used for coloring PVC. Because of the mixing or embrittlement gap in the PVC-plasticizer system, which ranges from 5 to 18% for dioctyl phthalate for example, such pastes have little or no suitability for unplasticized PVC compounds. In this concentration range, which is specific for each plasticizer, no plasticizing effect is achieved, on the contrary the additive causes embrittlement of the PVC. 

In plastics, Toluidine Red is practically limited to rigid PVC. Its lightfastness in full shades and slight white reduction is fair. Besides, the pigment is also used to color a number of specific media, such as normal wax crayons and pastel chalks or low-cost watercolors. 

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