In the previous part much was touched on as to color.
 
 
Color Index (CI) - this is a standard to the actual pigment and dye in a generic sense. Basically giving the color but no specifics of that color makeup, though type of pigment/dye and other information can be found for a fee at http://www.colour-index.org/
 
Heat resistance - The supplier of the color should list maximum processing temperature for the color, thus preventing a color shift when processing at a temperature below this point.
 
Light fastness - this is the effect of UV on the color and is rated at 8 for very good fade resistance to a 1 at a very poor resistance to color fade.
 
Weather fastness - In addition to the UV rays there are IR rays, moisture, rain, and temperature fluctuation which can affect the color quality of the part.
 
Migration - this is sometimes referred to as bleeding and blooming and it is color coming to the surface of the part, basically the pigment dye is not stable within our part.
 
Abrasion - Some inorganic pigments such as titanium dioxide are very abrasive, causing long term wear on screws and barrels, and other components to the process.
 
Plate-out - this is where incompatible pigments within the system will plate out to the processing equipment.
 
Chalking -  this is where when to much pigment is added the surface of the part rapidly degrades in a weathering test.
 
 
Let Down ratio - defines the strength of the coloring power of the concentrate. It indicates the number of pounds of Natural resin which can be colored by one pound of concentrate
 
Percentage of Pigment - this is how much pigment is in the concentrate. Typically 40 to 50 % but in some cases up to 80% for an extrusion application or use.
 
Hue - refers to an actual color desired, red, green, and blue, etc.
 
Opacity - This is an evaluation of the hiding power of the final product. To what extent does it transmit light. This is very important in matching colors and to formulating the concentrates.  Certain materials already have some color or opacity to them and have a range within them. Thus matching these ranges with a color and staying within the range desired can sometimes be an issue.
 
 
Dispersion - refers to the operation of creating the concentrate. If this is done properly it well achieve a uniform color in the final mix, given that again to make a color we may have various pigments incorporated into our concentrate.
 
If upon using the concentrate it is noticed that the green color shows streaks of blue than this may be a dispersion issue and not an issue for the processor. Note that it must first be determined if the green is pigment, and typically cutting it out and wiping on a white piece of paper should tell. If the result was a color streak of blue than dispersion is the issue. It is important to distinguish this, as contamination within the barrel and or plant may contribute to what look like a dispersion issue.  
 
Incorporation - This is the use of colorant in our natural material and issues can be streaks, light and dark areas and generally just not a good uniform color in our part.  This is not to be confused with dispersion where we see individual colors but see our final color not mixing well.
This can be a screw, barrel, temperature, melt flows and other issues causing this. The best method for determination of a good mixing screw is to place one pellet in the throat and allow mixing with material. If the resulting color pellet comes out as a pastel mixed area the screw function is good for mixing. If in fact we get a nice streak of color than the screw is not necessary good for mixing. 

SL Silvey

 

 

 Beaumont Technologies, Inc.
2103 East 10th  Street
Erie, PA 16511
Telephone  814-899-6390
Fax   814-899-7117
www.beaumontinc.com
 

     When size, stress and repeatability definitely have to be identical from 1 cavity to 96 cavities in the parts, give me call, or give BTI a call direct and tell them Steve sent ya.