Resins additive coloring effects

Further experimentation is needed to understand the interaction between process variables and responses. The effects of resin, additives and colorants, and mold geometry also need to be explored in a follow-up experiment. 

Indeed, it is the properties of the engineering resin which most likely led to its selection in the first place, so the influence of colorants on them is of utmost importance. Molders and part designers generally understand that mechanical property loss can be expected from the addition of colorants. However, problems arise when they grossly imderestimate their effect. A recent informal survey of part designers revealed that they typically plan for a 5% reduction in mechanical properties due to colorants. Depending on the resin and colorant selection, this number can easily exceed 30% Whafs more, the drive towards thinner and thinner wall sec-... 

In addition to removing colored impurities and other colloids, ion exchange resins effectively remove the uncolored precursor of these colored substances. It has long been recognized that a small amount of 5-hydroxymethylfurfural (HMF), formed from dextrose by the action of acid catalysts, decomposes to form organic acids as well as pigments which polymerize to form highly colored bodies.23 Normal bone char... 

In addition to jetness, plastics pigmented with carbon blacks typically exhibit color undertones. Undertone in black plastics appears as a distinct blue or brown-to-orange undertone, depending on the particle size of the carbon black used. In general, in full-shade, black molded applications, fine-particle-size carbon blacks impart a bluer tone. This behavior reverses itself in tints. Large-particle-size carbon blacks impart bluer undertone. Note that the effects of fillers, polymers, and dispersion can alter the typical behavior described above. Tint strength is the relative ability of the carbon black to darken a resin colored with chromatic pigments. 

It is important to note that not all dyestuffs behave the same when used in different applications or different polymers. Similarly, the hue of the dyestuff may change when the dyestuff is used in different plastics due to its solubility in that resin as well as factors created by the inherent color of the polymer. Residual volatile components in the polymer as well as catalysts and other additives have a distinct effect on the property of the dyestuff. Trace contaminants in the dyestuff can also have a profound effect on the dyestuff performance in different resins. 

So is the case in polymers containing additive systems. As will be shown, some additive systems can impart so much light scattering to the base resin that certain colors can no longer be achieved. Or if they can be achieved, other properties may be adversely affected, such as impact strength and cost. In either case, the practical color gamut or palette that is obtainable with this particular resin system is reduced. The discussion below presents the effects that the polymer and its additives can have on colorability. Color data presented in the following tables have been calculated under illuminant D-65,10° observer, specular included, expressed in CIELAB units, unless otherwise noted. 

The above discussion deals with the base polymer only. One can see that if the additive system imparts light scattering similar to these examples above, the effect on coloring the total resin system can be dramatic. We begin our discussion of additives by looking at polymer blends, where the secondary polymer can be considered an additive to the continuous base polymer. 

Virtually all polymeric resins undergo oxidation in the presence of oxygen. To retard this degradation, antioxidants are typically added. These additives are usually hindered phenols, amines, hydroxylamines, phosphites, or thioesters. In general, antioxidants will have little effect on colorability since they are typically used at low levels. At higher levels, they may increase light scattering and impact colorability depend-... 

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