If we compare addition-cure liquid silicone to a construction crew, the platinum catalyst would be the "start-work command." Without it, hydrogen-containing silicone oil and vinyl siloxanes would struggle to crosslink efficiently. However, if the command is too strong, too weak, or interfered with by the on-site environment, the curing process may also go awry.

1. It’s not a case of "the more, the better"

Increasing the dosage of platinum catalyst usually speeds up the reaction, shortening both the surface dry time and the overall curing time. However, this doesn't necessarily mean better performance.

Too much catalyst can lead to:

• Shorter working time, narrowing the process window for potting, coating, or molding;
• More concentrated exothermic heat, causing a more significant temperature rise inside thick-walled products;
• Overly rapid local curing, resulting in uneven stress distribution;
• Increased costs without necessarily improving mechanical properties.

Too little catalyst may result in:

• Incomplete curing;
• A tacky surface;
• Lower hardness in deeper sections;
• Reduced temperature resistance and aging resistance.

Therefore, the catalyst dosage usually needs to strike a balance between "working time" and "curing efficiency."

2. Temperature is a key variable

Addition-cure liquid silicone is quite sensitive to temperature. As the temperature rises, the speed of the platinum-catalyzed reaction typically accelerates significantly; if the temperature is insufficient, slow curing or uncured deep sections may occur.

In actual production, the curing profile is not as simple as just "setting a temperature." Heating rate, holding time, product thickness, mold thermal conductivity, and filler content all affect the final curing result. For instance, if thermal gels or potting compounds are filled with a large amount of thermal powder, the heat conduction paths and viscosity states will change, requiring the process conditions to be re-validated.

3. "Poisoning" and "Inhibition" are not exactly the same thing

The term "platinum poisoning" commonly used in the industry usually refers to the significant reduction or even loss of platinum catalyst activity due to certain substances. More rigorously speaking, some substances only temporarily inhibit catalytic activity, while others may cause more permanent deactivation.

Common sources of risk include:

• Sulfur-containing rubbers or residues from sulfur vulcanization systems;
• Certain amine-based curing agents or nitrogen-containing additives;
• Phosphorus-containing flame retardants;
• Residues from certain solvents, mold release agents, or cleaning agents;
• Impurities on the surface of fillers that haven't been sufficiently treated.

If the liquid adhesive comes into contact with these substances, phenomena such as local non-curing, surface tackiness, or softening at the boundaries may occur. During troubleshooting, don't just suspect the catalyst; also check whether the substrate, molds, cleaning agents, or packaging materials have introduced interferents.

4. Why do some products use "delayed" or "encapsulated" catalysts?

To balance storage stability with application convenience, many systems use platinum catalysts with relatively lower activity or those that have undergone encapsulation treatment. They exhibit lower activity at room temperature, facilitating storage and handling; once a certain temperature is reached, their activity is released, significantly boosting the curing speed.

This is valuable for applications that require a longer working time but also desire rapid curing, such as:

• Large-area electronic potting;
• Thick-layer thermal gel coating;
• Sealing of complex structural parts;
• Molding processes that require controlled gel times.

5. Step-by-step troubleshooting for failure analysis

When addition-cure liquid silicone exhibits curing anomalies, you can check the following aspects:

• Confirm whether the ratio of Component A to Component B is correct;
• Ensure mixing is uniform, especially at the bottom and edges of the container;
• Verify that the curing temperature and time meet requirements;
• Check for contact with sulfur-, nitrogen-, or phosphorus-containing substances;
• Determine if the substrate, molds, or cleaning agents introduced interference;
• Confirm whether the catalyst was contaminated or deactivated during storage;
• Ensure that fillers, additives, and diluents are compatible with the system.

Often, the problem doesn't necessarily stem from the catalyst itself, but is the result of a combination of process conditions, material compatibility, and environmental impurities.

6. How to use platinum catalysts more stably?

A more robust approach is to view the platinum catalyst as "part of the system" rather than a standalone "universal accelerator."

It is recommended to focus on:

• Matching the catalyst type with the reaction temperature;
• Synergy with the ratios of hydrogen-containing silicone oil and vinyl siloxanes;
• Whether fillers and additives have undergone compatibility verification;
• Stability of storage conditions;
• Consistency of the process window from small-scale trials and pilot runs to mass production;
• Establishing a standardized troubleshooting process for abnormal curing phenomena.