The common phenomenon and solution of"poisoning"in addition molding sealing adhesive:In the actual use process,the catalyst in the system is easily affected by certain substances to change its original structure,reducing its catalytic activity for hydrosilylation reaction,and causing solidification obstacles in addition molding sealing adhesive,also known 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.These substances mainly include:
　　•Ionic compounds of lead,mercury,bismuth and other heavy metals
　　Organic tin or organosilicon rubber containing organic tin catalysts(some condensed silicone)
　　Sulfur,polysulfide,polysulfide 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 plasticizers(such as exudates from certain PVC wires and insulating tape insulation paper)
　　Common"poisoning"phenomena and solutions of some welding flux residues(rosin,soldering tin,etc.)
　　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 the catalyst failure caused by the 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 during the mixing and perfusion test)
　　Solution:Use ethanol or isopropanol to clean the plastic surface before applying adhesive.Addition potting adhesive may come into contact with various materials during the application process.If there are doubts about whether certain surfaces or materials will inhibit curing,it is recommended to conduct small-scale compatibility testing first to determine its suitability for 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.