PVC Wire Color

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mbrooke said:
What is the "real" color of THHN/THWN-2? How do they make red/green/black/white/orange/purple/grey ect?
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The inner layer is PVC which is whitish with no fillers or additives just like plumbing grade PVC pipe. The outer vinyl layer is clear. PVC breaks down in sunlight so adding carbon black protects it sort of like sun screen. It also strengthens it. The rest of the colors are just dyes mixed in. Vinyl starts out like soup. When you add a cross linking agent (chlorine) it makes the monomers cross link and stitch together. If the amount is low you get slime (think Nickelodeon). With more you get various grades of plastic eventually overdoing it in CPVC (over chlorinated PVC) that is heat resistant and lasts longer. PVC naturally turns into HCl (hydrochloride acid) and attacks itself over time. The amount of cross linking and amount of fillers controls rubberiness vs stiffness. Kaolin is also used which makes it whiter and stronger as opposed to black.
 
paulengr said:
The inner layer is PVC which is whitish with no fillers or additives just like plumbing grade PVC pipe. The outer vinyl layer is clear. PVC breaks down in sunlight so adding carbon black protects it sort of like sun screen. It also strengthens it. The rest of the colors are just dyes mixed in. Vinyl starts out like soup. When you add a cross linking agent (chlorine) it makes the monomers cross link and stitch together. If the amount is low you get slime (think Nickelodeon). With more you get various grades of plastic eventually overdoing it in CPVC (over chlorinated PVC) that is heat resistant and lasts longer. PVC naturally turns into HCl (hydrochloride acid) and attacks itself over time. The amount of cross linking and amount of fillers controls rubberiness vs stiffness. Kaolin is also used which makes it whiter and stronger as opposed to black.
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Alright. But how do they do white PVC?
 
mbrooke said:
Alright. But how do they do white PVC?
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White is the one color where you have to subtract pigment, rather than add it. For plastics in general, titanium dioxide is a typical additive to render the plastic white, to take the place of its original color. I don't know if this is what is used in wire specifically. In its raw form, before any colorant substance is added, plastic wire insulation is a beige color.

Manufacturers used to make wire with insulation that was the raw beige color of the plastic insulation, and it was known as "natural color". It was designated to the same application as white and gray wire is today. Rarely, if ever, will you see wire sold today with a "natural" finish.
 
Carultch said:
White is the one color where you have to subtract pigment, rather than add it. For plastics in general, titanium dioxide is a typical additive to render the plastic white, to take the place of its original color. I don't know if this is what is used in wire specifically. In its raw form, before any colorant substance is added, plastic wire insulation is a beige color.

Manufacturers used to make wire with insulation that was the raw beige color of the plastic insulation, and it was known as "natural color". It was designated to the same application as white and gray wire is today. Rarely, if ever, will you see wire sold today with a "natural" finish.
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Does that mean white wire meggers out less?
 
Carultch said:
White is the one color where you have to subtract pigment, rather than add it. For plastics in general, titanium dioxide is a typical additive to render the plastic white, to take the place of its original color. I don't know if this is what is used in wire specifically. In its raw form, before any colorant substance is added, plastic wire insulation is a beige color.

Manufacturers used to make wire with insulation that was the raw beige color of the plastic insulation, and it was known as "natural color". It was designated to the same application as white and gray wire is today. Rarely, if ever, will you see wire sold today with a "natural" finish.
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The three white pigments are titanium oxide, kaolin, and either ground or precipitated calcium carbonate. TiO2 runs around $2,000 per ton while filler grade GCC (literally ground limestone) and kaolin run around $65-75/ton while PCC runs around $150/ton last I knew although that was a few years ago when I worked for the largest specialty pigment producer in the world at the time. White is reflecting all light while black is absorbing everythjng. You get colors by starting with white and adding in either pigments or dyes. Aside from black and white, there are some other natural pigments like ochre but the biggest group I know is the iron pigments, fire engine red (Fe2O3), construction yellow (FeCl?), and black (Fe3O4). I’m not sure if these would be used in cables though for conductivity reasons. But as a general rule you make white plastic then dye it.
 
In college our professor was demonstrating how a scanning Auger electron microscope could show which chemical elements were in a sample. One of the students asked if he could check what was in the white letter "m" on the M&M's candies that he had with him. From the Auger spectrum the professor determined the white lettering was titanium dioxide.
 
mbrooke said:
So grey THHN is in its natural color state?
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No. Wire insulation with its raw color is no longer manufactured, and it is much closer to white than it is to gray. If I were to guess, gray pigment is probably a blend of the white colorants and a light dose of carbon black. Similar to the additives to make PVC conduit in contrast from PVC plumbing pipe.
 
When I watch How It's Made, uncolored plastic granules seem to be white or clear, and it takes a relatively small portion of colored granules to impart a saturated color.
 
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