Testing methods for silicone sealant

Key pre-curing performance indicators for silicone sealants include tack-free time, snap-off time, viscosity, consistency, extrudability, slump, and density; standardized national test methods exist for each of these parameters.

The test standard for tack-free time is GB 13477-5; reaching this stage after application indicates that surface cross-linking has begun, so tooling operations should ideally be performed before this time is reached. The test standard for snap-off time is Appendix D.5 of GB 16776; this method applies only to two-component sealants and indicates the working time. The test standard for extrudability is GB/T 13477.4-2017; this reflects application performance, where higher extrudability corresponds to a greater volume of sealant dispensed per unit of time. The test standard for slump is GB/T 13477.6-2002; this reflects thixotropic properties, with low slump indicating good thixotropy.