Coloring plastisol for dip molding, rotocast, and coated fabric

Plastisol takes a pigment dispersion in a plasticizer carrier, let down at about 2 percent of the compound, roughly a 50 to 1 ratio. The carrier is the same class of material the compound is already built on, so it needs no separate accounting the way it does in a reactive system.

That last point is the one worth understanding, because it is the reason coloring plastisol is simpler than coloring anything else on this site.

Why the carrier is not a compromise here

Plastisol is PVC resin suspended in plasticizer. It is not a solution and not a melt: the resin particles sit dispersed in the plasticizer until heat drives solvation and the mass fuses into a solid.

A pigment dispersion for plastisol is pigment ground into that same plasticizer. When it goes in, it is more of what is already there. It does not introduce a foreign phase, it does not have to be compatibilized, and it does not need a separate line in the formulation logic beyond the plasticizer it contributes.

Compare that with the other systems. In cast polyurethane a plasticizer carrier is a non-reactive addition that occupies volume between chains and shows up in hardness and rebound. In epoxy it is a diluent that takes no part in the amine-epoxy cure and slightly lowers glass transition temperature. Both are manageable and both need thinking about. In plastisol the carrier is native to the formulation.

The practical instruction that falls out of this: tell your colorant supplier which plasticizer your compound runs on. Matching the carrier to it keeps the addition inside your formulation rather than beside it.

How much, and what the percentage is of

The published figure for flexible PVC plastisol is about 2 percent, a 50 to 1 let-down, measured on the compound rather than on the resin alone. State the basis whenever you quote a loading, because a percentage with no basis is not a specification.

Where you land inside that depends on the pigment and on how much hide the shade has to deliver. Titanium dioxide, carbon black and an organic red need very different loadings to reach the same opacity, which is why a single flat number across a palette is a planning estimate rather than a formulation. Confirm it on a drawdown in your own compound.

The same ambiguity, and the same discipline, applies in cast polyurethane: see how much colorant to add to cast polyurethane.

Fusion is a pigment-selection question

Plastisol gets its properties from heat. The compound has to reach fusion temperature and hold there, and that puts the pigment, not the dispersion, on the critical path.

Organic pigments have real temperature limits and some of them sit uncomfortably close to a fusion schedule. Diarylide yellows release 3,3-dichlorobenzidine above 200 degrees C. That is a decomposition threshold rather than a fading threshold, and it is a reason to select the pigment against the process rather than against the color chip alone.

So the useful thing to send with a shade target is the fusion temperature and the dwell. A pigment that holds at your schedule is a selection decision made once, at match time, and it costs nothing to get right then.

The dispersion has to leave your rheology alone

Plastisol viscosity is a process variable. Dip thickness, pickup on a rotocast tool, coating weight on fabric: all of them move with it, and a shop that has tuned a compound to run at a given viscosity does not want a colorant retuning it.

Two things follow. The dispersion should meter at your conditions, which is a specification rather than an afterthought, and low-viscosity or pourable trims exist for shops running metering pumps rather than hand addition. Tell us the pump, the addition rate, and where in the process the color enters.

Plastisol color and plastisol ink are different products

Searching for plastisol color returns screen-printing content, because screen-printing plastisol ink is the largest consumer use of the word. It is a different product with a different job.

Screen-printing plastisol is a finished ink. It is sold ready to print, it is formulated to sit on the surface of a fabric, and its color is built in by the ink maker. A pigment dispersion is a concentrate: you let it down into your own compound at a couple of percent, and the color runs through the whole part rather than sitting on top of it.

The distinction matters when you are searching for a supplier, because the advice written for one does not transfer to the other. Cure temperatures, dye migration onto polyester, and squeegee technique are ink problems. Fusion schedule, viscosity, carrier plasticizer and hide are compound problems.

Phthalates

Our color runs on a phthalate-free terephthalate plasticizer. Terephthalate is the para isomer of the phthalate ring: the two carboxyl groups sit opposite each other rather than adjacent. That geometry is what the restricted-substance lists are drawn around, and it is why a terephthalate ester is not a phthalate.

Flexible PVC is where phthalate scrutiny lands hardest, which is why the carrier question comes up on this line more than on any other.

What to send so the first sample works

Four things.

The compound itself, because we match into your material rather than a substitute. The color reference, which can be a PANTONE code, a RAL number, a Federal Standard 595 chip, a molded part, or a photograph. The plasticizer the compound runs on, so the carrier suits it. And the fusion temperature and dwell, so the pigment is selected against your process.

A shade target on its own leaves three of those four open. Sent together, they usually make the first sample the last one.

Frequently asked

What kind of colorant does plastisol take?

A liquid pigment dispersion in a plasticizer carrier, let down into the compound before fusion. Plastisol is PVC resin suspended in plasticizer, so a plasticizer-carried dispersion is native to the formulation rather than a foreign phase in it.

How much dispersion does plastisol take?

About 2 percent of the compound, roughly a 50 to 1 let-down, is the published figure for flexible PVC plastisol. State the basis when you quote it. Where you land inside that depends on the pigment and the hide the shade needs, so confirm it on a drawdown in your own compound.

Does the colorant change my plastisol viscosity?

It can, and that is why viscosity belongs in the specification. Dip thickness, rotocast pickup and coating weight all move with compound viscosity. Low-viscosity and pourable trims exist for metering-pump shops. Tell us the pump and the addition rate and the dispersion is formulated to meter at your conditions.

Will the pigment survive fusion?

That is a pigment-selection question rather than a dispersion question. Organic pigments have real temperature limits: diarylide yellows release 3,3-dichlorobenzidine above 200 degrees C, close enough to a fusion schedule to matter. Send the fusion temperature and dwell with the shade target and the pigment is selected against them.

Is this the same as plastisol screen-printing ink?

No. Screen-printing plastisol is a finished ink formulated to sit on a fabric surface and sold ready to print. A pigment dispersion is a concentrate let down into your own compound so the color runs through the part. They share a name and a resin family and very little else.

Can you match into my own compound?

Yes. Send the plastisol and we match into it rather than into a substitute. Plastisol is the system we match most often, so the bench has seen compounds like yours before.

Send us the compound, not just the shade

Plastisol and cast urethane are seven in ten of what we match, and plastisol is the larger of the two. Custom matching is free, samples ship at 0.5 kg, and there is no minimum order. Colors ship in 5 kg, 12.5 kg and 20 kg pails, and in drums and totes.