Are there any test results from known independent research institutes?

Yes, since 1995 TNO in Delft (The Netherlands) has developed a research program based on practical research and evaluation to test the durability of the products used to repair windows and windowframes.
All products from Repair Care have been tested according to the TNO method. In addition, Repair Care itself has been testing with its own test station in the Austrian Alps for more than 20 years.
In Europe, the test institutes have further agreed that the test standards are mutually recognized.