Characterization of the morphology of iPP/sPP blends with various compositions

The paper investigates the morphology and the structural properties of blends of isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) having different compositions using different techniques. Solid-state nuclear magnetic resonance (NMR) permits via appropriate sequence to measure the composition, conformation and dynamics, and intimacy of mixing of polymeric materials. Measurement of relaxation times gives information on local structure of phases with different mobility. The morphology is directly related to the structural organization of the blends. The crystallization rate decreases as a function of the sPP content. The minor component is dispersed as a nodule in the main component of the blend and it plays the role of nucleating agent on it. Besides, morphology changes occur for the composition 50/50 (wt/wt) of the blend iPP/sPP. Different phases are identified, namely free amorphous, constrained amorphous and crystalline regions which exhibit different molecular mobilities. It is also shown at the interphase matrix-nodules, the nodules create a constrained amorphous zone.