The Mechanism of Action of Sugar Acetals as Nucleating Agents for Polypropylene

• Published in: Macromolecules 1994-06, Vol.27 (12), p.3147-3155
• Main Authors: Smith, Tammy L, Masilamani, Divakaran, Bui, Long Kim, Khanna, Yash P, Bray, Robert G, Hammond, Willis B, Curran, Sean, Belles, John J. Jr, Binder-Castelli, Shari
• Format: Article
• Language: English
• Subjects: Applied sciences; Crystallization; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma00090a006

We studied the nucleation of polypropylene via experimental measurements and molecular modeling, and we propose that sugar acetal nucleators stabilize the helical form of polypropylene at the molecular level. Through FTIR techniques, we established that the nucleators dibenzylidene sorbitol (DBS) and trinaphthylidene sorbitol are chemically stable in molten polypropylene. Using solid-state NMR, we determined that DBS is dispersed to particles 32 A in diameter. These particles are three orders of magnitude smaller than the 1-10 mu m size expected in the literature. DSC was employed to evaluate the nucleating ability of our nucleators. Through molecular modeling, we demonstrated that nucleating ability can be correlated with van der Waals attractions of the individual nucleator molecules with the helical form of polypropylene. A correlation was not seen when hydrogen-bonded nucleator dimers were used. The model correctly predicted that one TNS diastereomer nucleates polypropylene and that the other diastereomer does not.