The Curing Process of MS Sealant

The Curing Process of MS Sealant
The curing process of MS sealant is gradual and generally divided into three stages, with distinct changes in morphology and properties at each stage:
1. Induction Period (0.5-2 hours after application, depending on the formulation)
Reaction Characteristics: The accelerator and initiator begin to react, with the initiator slowly decomposing to produce a small amount of free radicals, but no obvious polymer chains have yet formed;
Appearance and Performance: The colloid remains liquid or semi-liquid, exhibiting a certain degree of fluidity and unable to withstand external forces (e.g., deformation due to pressure);
Core Function: This is the free radical “accumulation” phase, preparing for subsequent rapid polymerization. 2. Rapid Polymerization Phase (1-6 hours after the induction phase)
Reaction Characteristics: The free radical concentration reaches a critical value, triggering a chain polymerization reaction—a large number of monomer double bonds break, combining with the prepolymer to form linear polymers. Crosslinkers (such as monomers with multiple double bonds) then form a preliminary network structure.
Appearance and Performance: The colloid gradually loses fluidity, the surface begins to solidify (not sticky to the touch), while the interior remains semi-cured, with initial elasticity emerging.
Note: This stage is accompanied by a slight exotherm (polymerization heat), but because the monomer content is controllable, the exotherm temperature is typically < 40°C, posing no safety risks. 3. Full Curing Period (24-72 hours, subject to significant environmental impact)
Reaction Characteristics: Linear polymers further crosslink to form a dense three-dimensional network structure. Small amounts of unreacted monomer continue to polymerize until the reaction reaches equilibrium.
Appearance and Performance: The colloid fully cures into an elastomer with a smooth, non-sticky surface. It exhibits the designed tensile strength (typically 0.5-2 MPa), elongation at break (200%-500%), and weather resistance.
Key Performance Indicators: After full curing, the colloid maintains a relatively stable volume with no noticeable shrinkage, and can withstand long-term environmental stresses such as vibration and temperature fluctuations.