Sealants come in a wide variety of chemical base,however the three most common industrial sealants are
Silicones
Polyurethane
MS Polymer/Modified Silanes
All are single component sealants that cure when exposed to moisture.Curing rate depends on humidity,environmental and substrate temperature and thickness of sealant. However,they differ in their final physical properties achieved after full curing such as temperature resistance,Weaterability,Surface Preparation required and paintaibility etc. One must choose based on the final properties desired.