Accelerated Waterborne Pressure Sensitive Adhesive Development
Through Rheological Screening
Water-based pressure sensitive adhesives (PSAs) are viscoelastic materials commonly utilized for labels and tapes, among other applications. Basic PSA performance attributes such as tack, peel and shear depend on the polymer’s bulk linear viscoelastic properties.1,2 Moreover, correlations exist between adhesion test time scales and polymer deformation frequencies, with tack, peel and shear test time scales spanning the frequency range 10-2 to 102 rad/s.1,2 Chang used this frequency range coupled with PSA storage (G’) and loss (G”) moduli to define so-called viscoelastic windows, wherein a given PSA’s window provides insight into its performance properties and the type of PSA (e.g., removable, general purpose, etc.).1,2
This relationship between PSA viscoelastic behavior at given frequencies and performance is useful as a means to target PSA performance attributes and application fit. Standard adhesive application tests like tack, peel and shear can be time consuming and highly dependent on film thickness and quality, which can lead to high variability in the test results (particularly with shear resistance testing). However, using rheology to probe PSA viscoelastic behavior is much less time consuming, more repeatable and more representative of in-use performance. Rheology enables one to screen samples quickly and accurately identify trends for synthetic parameters to achieve targeted PSA properties.