CRJ-700 Captain reported sealant began to smear across the windscreen after takeoff. The Captain's windshield had been replaced and speed tape applied over the uncured sealant to expedite departure. The flight crew requested priority handling and made an air turn back and precautionary landing at departure airport.

Narrative

Front portion of left windshield seal began to detach at altitude on previous flight; leaving multiple stains on window from turbulent flow prior to full detachment. Approximately 8 to 16 inches in total for two locations; each within close proximity. Maintenance explained the seal had not cured for a sufficient time period from previous maintenance. Speed tape was applied to both areas and signed off for flight. During climb out on the ZZZZZ departure on Aircraft X; speed tape began to separate from applied locations; removing further seal. This began about 9000 ft. and continued for a few thousand feet. I notified ATC about 13000 ft. that we needed to return to field for a flight deck windshield seal issue. We leveled off at 14000 ft. and ATC cleared us to descend to 11000 ft. I did not request priority handling after ATC inquiry since any pressurization issues would not be a serious factor with our return to a lower altitude; in which further descent continued. I also chose to return to the field because of the additional information that the seal had not cured properly and now questioned if the seal detaching was entirely aerodynamic; part of the outer protection of the inner windshield seal; and/or whether it was local in nature or encompassed the entire edge of the windshields and forward windows. I did not have enough information to be confident in a decision to climb to a cruise altitude and continue with the flight. I changed to Pilot Flying and we returned to the field with no further incident; we were assigned a new aircraft to complete the flight.