Polymers additive coloring effects

A product of given characteristics can be obtained by mixing pellets of different polymers, additives such as colorants, stabilizers, antioxidants, flame-retardants, and so forth. Thermomechanical modifications can be brought about either by silanes or peroxides or by exposure to ionizing radiation. A product of good quality is certainly the result of experience, ability, and good knowledge of the interactions between the different substances, and also characterization of final products with the most effective techniques is of vital importance. Many techniques, collected in Table 1, are available for the characterization of PEX. ... 

Polyolefins are intrinsically unsuitable for outdoor durable applications since the will easily photo-oxidize in exterior conditions. However, their combination of low cost, ease of processing, and recyclability continues to promote research into effective methods of photo stabilization of polyolefins. Adequate pigment levels will afford some protection from UV radiation to the host polyolefin. UV stabilizers and antioxidants, however, need to be added to the durable in order to ensure long term performance in outdoor environments. There is usually negligible to no protection of colorants from photo degradation with these same polymer additives. 

Sodium antimonate contains less antimony than either antimony trioxide or pentoxide and is thus less effective. However, its unique pH and low refractive index makes the antimonate the most desirable synergist for polymers that hydrolyze when processed with acidic additives or in polymers for which deep color tones are specified. Sodium antimonate costs approximately 3.30—4.40/kg and can be obtained from either Elf Atochem NA under the Thermoguard name or from Anzon Inc. as a Timinox product. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Temperature control at -15° to -25°C was also required for maximum yield. The best results were obtained by maintaining a temperature of -20 to -25°C during the addition of citral anil to the acid and at -15°C for the duration of the reaction. At this temperature range, the formation of a-cyclocitral (III) is favored. Higher temperatures caused excessive polymer formation and favored formation of e-cyclocitral whereas lower temperatures caused a reduction 1n the yield of the citral mixture. At least part of the problem with the lower temperature reaction was the fact that the sulfuric acid tended to freeze around the inside of the reaction vessel causing the effective molar ratio of acid to anil to be reduced. These lower temperature reaction mixtures were also lighter in color which indicated less polymer formation but this was accompanied by a lower yield of cyclocitrals. 

The color of the final product primarily depends on the qualification of the raw materials, TPA, DMT and EG. The content of heavy metals in TPA, residues of catalysts employed during oxidation of p-xylene, and polymer processing affect the final color of the polymer. The tendency of certain catalysts, such as titanium or tin derivatives, to make the polyester yellowish in color is well established. The conversion during esterification is prolonged due to larger TPA particles or their hardness. Color can be influenced by these factors, as well as by chemical impurities in the raw materials, such as water, aldehydes or the quality of insufficiently recovered EG. Similar effects on color can be observed as a result of impurities caused by additives, particularly from less purified Sb2C>3. The quality of the latter can be assessed simply by the color of its solution in EG. 

The clean and efficient production of azo dyes is a classical chemistry problem. The manufacture of this industrially important family of compounds is traditionally associated with the additional formation of large quantities of hazardous and colored waste. A method for the construction of both phenolic and amino azodyes has been reported using a polymer-supported nitrite reagent to effect diazoti-zation of aromatic amines (Scheme 2.53) [80]. Waste minimization and operational simplicity, along with improved separation technologies, are key advantages of polymer-supported reagents in this area. 

Catalysts, colorants, foaming agents, biocides, lubricants, and antistats are also used as additives for polymers. Although foaming agents reduce the specific gravity, the other cited additives, when used in moderate amounts, have little effect on the physical or thermal properties of the polymers. 

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