Syntactic polyurethane elastomers are made using a non-mercury catalyst. The elastomer is made from a reaction mixture containing a polyether polyol, a chain extender, a polyisocyanate and microspheres. The elastomer is characterized morphologically by the presence of small discrete morphological domains 0.1 to 3 μm in diameter, and the substantial absence of discrete morphological domains 5 to 30 μm in diameter. The elastomer adheres well to itself, which makes it very useful as thermal insulation for pipelines and other structures that have a complex geometry.