Rheology as a Tool to Investigate Anti-Nucleation in Semicrystalline Polymers

In semicrystalline polymers, the crystallization process plays a vital role in determining their properties. Differential scanning calorimeter (DSC) is the conventional method for studying crystallization kinetics in polymers but may lack sensitivity in detecting antinucleating phenomena. This work applied a rheological technique to detect the antinucleating effect of 3,4-dihydroxyhydrocinnamic acid (hydrocaffeic acid [HCA]) on polycaprolactone (PCL). While DSC was useful in detecting HCA's ability to reduce PCL's melting point, it could not detect the polymer's crystallization during the cooling cycle. Adding the nucleating agent dibenzylidene sorbitol (DBS) did not negate HCA's antinucleating effect. Parallel plate rheology revealed that HCA caused a fourfold reduction in solidification time, with Avrami crystallization rate constants changing by 10⁻³ times. Additionally, polarized optical microscopy visually demonstrated the hindering effect of HCA on PCL crystallization. Analyzing crystallization kinetics by rheological measurements and the Avrami model proved successful in studying the crystallization kinetics of PCL with the antinucleating agent HCA while observing the crystallization process.