Common Phenomena and Solutions of

In the actual use process of silicone potting compounds, the catalyst in the system is easily affected by certain substances and changes its original structure, connector potting reducing its catalytic activity for the hydrogenation reaction of silicon, resulting in the phenomenon of curing obstacles in addition molding sealing adhesive, which is commonly referred to as "poisoning". Specifically, it is manifested as being still in a liquid state after solidification, with a sticky surface or low hardness after solidification.

What can be done to solve the poisoning caused by addition molding sealing adhesive

What are the substances that affect "poisoning"?
Generally speaking, the amount of catalyst used in addition molding potting adhesive is below 0.1%, so a very small amount of impurities can cause catalyst failure. silicone potting These substances mainly include:
Ionic compounds of heavy metals such as lead, mercury, bismuth, etc
Organic tin or organosilicon rubber containing organic tin catalysts (some condensed silicone)
Sulfur, polysulfide, polysulfone, or other sulfur-containing materials
Amine, polyurethane or other nitrogen-containing materials, such as amine cured epoxy resin (hot melt adhesive)
Phosphorus, arsenic or other materials containing phosphorus, arsenic
• Unsaturated hydrocarbon plasticizer (such as Exudate of some PVC wires and Electrical tape insulating paper)
• Some welding flux residues (rosin, solder, etc.)

Common "poisoning" phenomena and solutions
1. Poor solidification of the solder joint contact area of the circuit board
This is the most common curing obstacle phenomenon of addition molding potting adhesive, specifically manifested as the contact area between the potting adhesive and the solder joint of the circuit board not solidifying or not fully solidifying, and remaining in a liquid state after long-term storage. This situation is generally caused by catalyst failure caused by residual rosin flux on the circuit board.
Solution: Use circuit board cleaning agent to clean the solder surface before applying adhesive.

2. Poor solidification of plastic surface contact areas:
This phenomenon is caused by the catalyst failure caused by the residual release agent on the plastic surface. From the figure, it can be seen that there are liquid substances on the inner wall of the plastic shell, and there are also many dispersed droplets on the outer surface of the solidified colloid. (The porosity is due to the lack of vacuum pumping during the mixing and perfusion test)
Solution: Use ethanol or isopropanol to clean the plastic surface before applying adhesive.

The addition potting adhesive may contact various materials in the application process. If there is doubt about whether certain surfaces or materials will inhibit curing, it is recommended to conduct small-scale Compatibility testing first to determine its suitability in specific applications. If there is liquid or uncured product at the interface between the substrate surface and the cured organic silicone, it indicates poor compatibility. At this point, it is necessary to identify the causes of curing obstacles based on specific phenomena and careful experiments, and then eliminate them.