Color part II

In the previous part we discussed some of the terms of the color and plastics.  In this part let us continue that discussion, and other points.

Dispersions:
What this refers to is the Dispersion or uniformity of color in the pigment but eventually in the part. Sometimes this may mean that the pigment is not disperse, or that the concentrate pellet, which carries the pigment, has not dispersed the pigment. Though these are similar they offer different problems.
1- Dispersion of the concentrate pellets may show up as a mottled color where you see color streaks or heavy areas of color. Almost as if we did not mix the pellets together.  A marbled effects if you would.
2- Dispersion of pigment can start in the concentrate pellets themselves. But within the part these can be dark streaks or spots of pure pigment.
3- In either of the two cases above we have not distributed or mixed the systems together.   In the case of the concentrate the easy fix is in mixing within the barrel.  In the case of pigment it can be more complicated due to the nature of the pigments.

Let-Down ratio:
1- Basic to the strength of the color concentrates. It refers to how much natural material is mixed with 1 pound of color concentrate.
2- An example would be 25:1 meaning those 25 pounds of natural are mixed with 1 pound of color concentrate.
3- The let down is very important in regards to what your cost may be. Basically if you are using a let down of 25:1 it than means you need 4 pounds of color concentrate for every 100 pounds of natural, if we went to 50:1 let down we now need only 2 pounds per 100 pounds of natural. Thus what is the cost of 25:1 material versus the cost of 50:1 material, since cost of manufacture is 4 times one versus 2 times the other respectively.
Hue:
 This refers to the color of finished product, basically red, blue, green, etc

Opacity:
This refers to the light transmittance of the finished product. Basically what is the hiding power of the pigments.  Or if making a transparent what finished transmittance do you wish and what is the wall thickness.

Temperature stability:
What this means is what temperature are you running the materials at. If in fact the temperature stability of the concentrate or pigments is not equal or above that of the material we can see color shift, black streaks, and a host of other problems. So it is important that processing conditions and especially temperature ranges be given up front when ordering the color concentrate.

To be continued:

Thanks for the time.

Steven L Silvey
Sr. Technical Service
General Polymers Division
Ashland Distribution