When a new customer places a first order, nine times out of ten the same question comes: "What is your platinum content, in percent?" Followed immediately by: "Then I'll take the 10% — higher content is better value."

That intuition happens to be exactly backwards. Platinum content is not a quality indicator; it is a metering specification. Choosing higher does not make it more active — it only makes it harder for you to weigh accurately and harder to mix uniformly.

1. Dispelling a Misconception First

Higher platinum content ≠ higher activity. Activity is determined by site structure, dispersion and ligand environment — not by the concentration of platinum in the solution. The same 10 grams of platinum formulated into 100 grams of solution and into 1 kilogram of solution has exactly the same total activity; the only difference is how much liquid you have to charge.

So what the platinum content figure actually does is: determine your charge volume and your metering precision.

2. Work Backwards from the Charge: the Only Correct Starting Point

The selection sequence should run like this:

Step one — calculate how many grams of platinum each batch needs. This is set by your formulation: the final platinum concentration in the system is normally at the ppm level, and multiplying that by the material per kettle gives the platinum mass required.

Step two — check whether the catalyst quantity corresponding to that mass can be weighed accurately.

Example: a 500-kilogram kettle, formulation requiring 10 ppm platinum, so 5 grams of platinum are needed.

• At 10% platinum content (i.e. 100 g/kg Pt): catalyst charge = 50 g
• At 2% platinum content (20 g/kg): charge = 250 g
• At 1% platinum content (10 g/kg): charge = 500 g

The difference is intuitive: weighing 50 grams on an ordinary bench scale can carry a relative error of several percent; 250 grams or 500 grams is far easier to weigh.

Step three — now look at small-batch production in reverse. If each kettle needs only 0.5 grams of platinum:

• At the 10% specification: only 5 grams of liquid — a quantity that cannot be dosed accurately into a kettle of several hundred kilograms, nor mixed uniformly;
• At the 1% specification: 50 grams is needed — meterable and dispersible.

Conclusion: the smaller the batch, the lower the content specification you should use; the larger the batch, the more you can use a high-content specification to reduce charge volume.

3. Typical Applications for the Four Specifications

There is also a class of even lower specifications (a few hundred ppm), serving products with strict limits on residual platinum — medical grade, food-contact grade and optical grade.

4. Metering Precision: the Most Underestimated Cost

The reality of charging on site is this: you cannot accurately add 5 grams of liquid into 500 kilograms of material.

A low-content specification brings three benefits:

1. It can be dosed continuously by metering pump — larger volume, easier to control, better reproducibility;
2. Dispersion is more uniform: a larger charge volume means the initial mixing after entering the kettle more readily reaches molecular-level dispersion, with no local over-concentration;
3. Human error is reduced — operators can weigh accurately with ordinary equipment, without depending on a precision balance.

The consequences of local over-concentration are very concrete: the reaction runs too fast at that point and gels prematurely, forming gel spots or fisheyes; while regions far from the dosing point are short of catalyst and never cure through. Both ends of the same kettle fail.

This is also why many customers buy a high-content specification and then have to dilute it themselves back at the plant — at which point they might as well have bought it pre-diluted.

5. What a High-Content Specification Costs You

Viscosity rises. At high platinum complex concentration the viscosity behaviour of the carrier silicone fluid changes, making pumping and metering harder.

Storage stability declines. At high concentration, interactions among platinum species strengthen, so slow agglomeration and activity decay are more likely over long storage. Dilute, low-content solutions normally have a steadier shelf life.

Self-dilution is costly. Dilution must use a carrier compatible with your system (normally the same grade of vinyl silicone fluid); you cannot make do with just any solvent. The dilution step must also guard against contamination and against moisture ingress — do it badly and you have destroyed the catalyst yourself.

Safety risk. If a concentrate leaks or is dosed in error, local platinum concentration becomes extremely high and can cause violent local reaction.

6. Three Things Not to Overlook

The carrier must match your system. Two products both at 2% platinum content are entirely different in character depending on whether the carrier is vinyl silicone fluid or xylene. A solvent-based carrier introduces volatiles and odour into the formulation; a silicone-fluid carrier requires confirmation of compatibility with your base polymer. Always ask what the carrier is when procuring.

Platinum content must have an accurate assayed value, consistent from batch to batch. In a process dosing at the ppm level, a 5% deviation in content means a 5% deviation in your formulation concentration. Require the supplier to provide the measured platinum content of every batch, not merely the nominal figure. On method, total content determined by fire assay or ICP is the most reliable.

Diluted material must be re-assayed. When you dilute it yourself, errors in the dilution ratio accumulate. Re-measure the platinum content after dilution and use the measured value as the basis for charging.

7. A Workable Selection Procedure

1. Fix the final platinum concentration (ppm) of the formulation and the material quantity per batch;
2. Calculate the platinum mass required per batch;
3. Work back to the catalyst charge at each specification — those landing in the 100 g to 2 kg range are the best fit: accurate enough to weigh, without excessive volume;
4. Verify carrier compatibility;
5. Request measured platinum content and batch data;
6. Run the three-step compatibility verification (static compatibility → dispersion uniformity → actual cure performance) before going to the line;
7. Once the specification is fixed, do not change it casually — changing the specification means changing the charge quantity and the dispersion method, and requires full revalidation.

8. The One-Sentence Summary

Platinum content is a metering specification, not a performance indicator. The only correct starting point for selection is "how many grams of platinum does each of my batches need," from which you work back to a charge that can be weighed accurately and mixed uniformly.

Small batches call for low content; large batches can use high content as a stock solution. But either way, keep your eye on the same three items: carrier compatibility, measured content, and batch-to-batch consistency. Buying high content because it "looks like better value" usually costs you back double on metering and dispersion.


Diethylenetetramethyldisiloxane platinum complex (platinum catalyst) MY 8115