Crystallization Behavior of Poly (Propylene Succinate) Stereocomplex from the Melt

• Other Authors: Okpowe, Omena (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Materials science
• Online Access: http://purl.flvc.org/fsu/fd/FSU_2017SP_Okpowe_fsu_0071N_13679

The isothermal and non-isothermal crystallization kinetics of poly (propylene succinate) stereocomplex over a broad range of temperatures has been studied. Crystallization peaks from Differential Scanning Calorimeter are only observed when cooling (at 10°C/min) from melt temperatures ~15 degrees above the observed melting peak due to self-seeding (heterogeneous melt). Annealing in this range of melt temperatures leads to a faster crystallization. This behavior is not found in analogs stereocomplexes of PLA, and is attributed to the interplay between dipolar interactions and diffusion of the enantiomeric helical sequences with formation of more nuclei with time in the melt. From a heterogeneous melt at low undercooling, the polymer displays a faster nucleation confined to the spherulitic boundaries, and then a growth with rate similar to that from a homogenous melt temperature. Linear spherulitic growth rates of the stereocomplex from a homogenous melt follow the classical bell shape crystallization temperature dependence peaking at 61ºC. The analysis of the growth rates according to secondary nucleation theory indicate two regimes of crystallization conforming to a transition from regime II to III. From the analysis, the nucleus basal surface free energy is estimated as ~ 55 ergs/cm2, in close agreement to values obtained for similar polyesters. === A Thesis submitted to the Program in Materials Science and Engineering in partial fulfillment of the Master of Science. === Spring Semester 2017. === April 10, 2017. === Includes bibliographical references. === Rufina G. Alamo, Professor Directing Thesis; Eric Hellstrom, Committee Member; Hoyong Chung, Committee Member.