Pigments dispersion testing

Color match accuracy is just one of many requirements that have to be met in any color formulation project. If pigments are used, the quality of the pigment dispersion is critical to the formulation s cost and performance. Light stability and physical strength properties deteriorate if the pigments are not fully dispersed. Our customers are continually challenging us with new applications, some of which have no standard testing procedures associated with them. We have to work harder and... 

In tests for melanophore pigment dispersion in eyestalkless individuals of the fiddler crab Uca pugilator, head extracts from the cockroach Periplaneta americana and the honey bee Apis mellifera showed strong activity, as did the crustacean eyestalk extracts 36). Head extracts of the butterfly Danaus plexippus and the mealworm Tenebrio molitor fere, however, inactive in the chromatophoral dispersion assay. 

Since the f mction of PDFs in insects is unknown, they have been tested for melanophore pigment dispersion in the fiddler crab. In this assay Acheta PDF and Romalea PDF were equipotent, and both were about 50% as potent as fiddler crab s PDH ( -PDH) and 10-fold more potent than a-PDH. The Acheta PDF and Romalea PDF differ from each other at position 14, with Val in the former and Leu in the latter. This substitution did not alter the melanophorotropic potency of the peptide. When compared to B-PDH, Acheta PDF has three residue substitutions position 4 (lie for Leu), position 8 (Leu for lie), and position 15 (Leu for Met). The substitution at position 8 does not seem to affect potency, because Penaeus PDH which has Leu-8 is as potent as B-PDH. 

Glass transition temperature, Tg, and storage modulus, E , were measured to explore how the pigment dispersion affects the material (i.e. cross-link density) and mechanical properties. Both Tg and E were determined from dynamic mechanical analysis method using a dynamic mechanical thermal analyzer (DMTA, TA Instruments RSA III) equipped with transient testing capability. A minimum of 3 to 4 specimens were analyzed from each sample. The estimated uncertainties of data are one-standard deviation. 

This may be a function of the higher levels of shear stress available to the twin screw operator though control of fill volume and throughput rates. Interestingly, superior pigment dispersion did not translate into significant increases in relative color strength values in film or in tint tests for MB-Yellow 1. 

Pigments and pigment dispersions have been and continue to be evaluated for color using a wide variety of methods. Over the years Oil Ink Tests, Latex Paint Tests, Liquid Ink Tests and PVC, Rubber, and Polyethylene Two-Roll Mill Tests have been used as Quality Control methods. We did not have extensive reproducibility data for these methods, but we felt that all of them could be improved using statistical tools. 

For the colored polyolefin piping and fittings, ISO 13949 specifies a test method for assessment of degree of pigment dispersion. 

Pigment Dispersion Application Forms Test Methods... 

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