Influence of the Plasticizer
Plasticizers are used in many sealant formulas to control the flexibility. The influence that plasticizers exert on the weatherability was studied for a series of plasticizers that are based on polypropylene oxide type polyols end-capped with acetate groups (Table 4). As a model system an acrylic MS-1 sealant was selected. Sealant films of 0.2 and 5.0 mm thickness were exposed in a carbon arc weathermeter and evaluated after various exposure times. No difference between the plasticizers was observed in the case of the 5.0 mm film. However, for a 0.2 mm sealant film some differences were observed.
The results indicate that polypropylene oxide plasticizers of higher molecular weight improve the cracking performance slightly. However, data from thin films are not as reliable and need to be interpreted with caution.