Polyurethane foams have an upper operating temp of ~175F, well above the exit-air temp of your dryer unless it's already on fire. Even under fault conditions the temp at the exit is unlikely to exceed 70C/158F (source.)
Fireblock versions have the same operating temp, but are treated to limit flame spread & smoke (primarily between floors) when the house is already on fire. Since the vent is on an exterior wall, that feature isn't necessary.
Fiberglass insulation is nearly useless in this type of application and results in yet another air infiltration leak into the house. (Fiberglass is an air-filter, not an air-barrier. Stuffing wads of paper in there would be a more effective air-block.) The dryer vent itself is also a big leak, but some of the better vent backflow preventers reduce that air leak almost entirely (when the dryer isn't in use.):
(There are multiple vendors of similar units.)
These are far more effective than standard dryer vents, and are designed to be easily cleaned of lint, unlike some of their less-effective cousins.