Meaning
Thermodynamic forces acting at the boundary between two immiscible liquid phases determine the stability and dispersion of droplets in an emulsion. This boundary force, called interfacial tension, is crucial in polymer blending where different polymer melts must be mixed. Lower values favor the creation of smaller droplets and more stable blends.
Phase Interaction
Cohesion within each phase opposes the adhesion between the different polymers at their common boundary. During compounding, interfacial tension resists the deformation and breakup of the dispersed droplets under shear flow. Additives known as compatibilizers concentrate at this interface to lower the energy barrier, allowing for finer morphology and stronger mechanical properties in the final co-polymer alloy.
This suppression of phase separation ensures that the different polymeric components remain uniformly distributed during the extrusion process, resulting in a product with consistent tensile strength and impact resistance.
Measurement Method
Spinning drop tensiometry and pendant drop analysis provide quantitative measurements of the boundary forces under melt conditions. Technicians use these methods to evaluate the effectiveness of newly synthesized additives before running full-scale trials. These measurements help predict the final morphology of the extruded polymer.
Processing Risk
High boundary energy leads to rapid phase separation and coarse structures that weaken the physical integrity of the extruded plastic. When droplets coalesce too quickly, the resulting material suffers from poor delamination resistance. These issues can cause premature failure of the finished product.
