How does the intumescent work in a collar?

When exposed to elevated temperatures the polymericnpipe materials will begin to soften and collapse depending upon the materialntype. During the softening phase of the pipe, the intumescent material willnexpand, generating pressure to effective crush the remaining pipe material,nprior to being fully consumed. The intumescent will form a thermal barrier bynforming a hard-residual char, to restrict the passage of fire through thensupporting construction.