What is the difference between MS sealant and polyurethane sealant?

What is the difference between MS sealant and polyurethane sealant?
MS modified silane sealant, also known as MS modified silane structural sealant, is mainly a one-component or two-component elastic sealant made of MS polymer as the base polymer, with fillers, plasticizers and other functional additives. The curing method is mainly to hydrolyze and de-alcoholize silane with moisture in the air and then condense it. It is a hygroscopic curing glue.
Polyurethane sealant is a one-component environmentally friendly plastic glue composed of organic isocyanate (-NCO) and polyester with terminal hydroxyl (-OH). It is an elastic sealant made by polyurethane prepolymer, fillers, plasticizers and other functional additives. The product type is one-component or two-component. Elastomers are formed by the reaction of isocyanate with moisture in the air or other active hydrogen compounds.