Black color streaks

Black Color Streaks in Molded Parts Case One... 

Figure 11.30 Photograph of black-colored streaks in a PP molded part...

Figure 11.32 Black color streaks on the surface of an injection-molded electronics housing made from HIPS and a gray color concentrate masterbatch...

The mixing requirement presented here is extremely difficult and noncommercial due to the very high letdown ratio used and the use of TlOj in the main resin. For experiments where natural ABS resin (no added Ti02) was used at a 100 1 letdown ratio with the black color concentrate, the very small white streaks at screw speeds... 

A few years ago it was pointed out to me by Sterling Hendricks that ordinary black mica, biotite, which has an intensely black color, owes this color to the presence of iron in both the ferrous and ferric oxidation state. Black tourmalines also usually contain both ferrous and ferric iron. Another intensely black mineral, with black streak, is ilvaite, with composition Ca(Fe )aFe+++(Si04)20H. 

JAMESON ITE. This mineral is commonly called brittle Jciillier-tirr from its brittle character and usual habit in acicular mats of crystals. It crystallizes in the monociinic system and is ot metallic luster, opaque with gray-black color and streak. It has a hardness of 2.5 and a specific gravity of 5-63-5.67. It is a sulfide of lead and iron antimony. Pb4FeSb(,S 4. 

Properties Iron-black to brownish-black color, dark-brown streak, metallic to submetallic luster. D 3.6, Mohs hardness 5.5. 

Properties Black color, brownish-black streak, pitchy to dull luster. Mohs hardness 5.5, d 6.5-8.5. 

Properties Red to reddish-brown to black color, adamantine to submetallic luster, streak pale-brown. Hardness 6-6.5, d 4.3, mp 1640C, refr index 2.7. Insoluble in acids. 

As discussed in Section 11.12.2, several root causes exist for black streak contamination in molded parts. These root causes include degradation of the resin in the screw channels and nonreturn valve or runner system, degraded material entering with the resin feedstock, and poorly dispersed pigments in the color masterbatch. To determine if the color concentrate masterbatch was the source of the black streaks, the color concentrate was removed from the feedstock and only natural... 

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