Surface Effect of Two Different Calcium Fluoride Fillers on the Non-Isothermal Crystallization Behavior of Poly(ethylene Terephthalate)

• Published in: Journal of macromolecular science. Physics 2014-02, Vol.53 (2), p.173-190
• Main Authors: Sánchez-Leija, Regina Janet, Riba-Moliner, Marta, Cayuela-Marín, Diana, Domínguez-Espinós, Octavio, Sánchez-Loredo, María Guadalupe
• Format: Article
• Language: English
• Subjects: Applied sciences; Calcium fluoride; calcium fluoride (CaF; calcium fluoride (CaF2); Composite materials; Composites; Cristal·lització; Crystallization; Enginyeria dels materials; Exact sciences and technology; Fluorurs; Forms of application and semi-finished materials; Materials compostos; non-isothermal crystallization; poly(ethylene terephthalate) (PET); Polyethylene terephthalate; Polymer industry, paints, wood; Technology of polymers; Àrees temàtiques de la UPC
• ISSN: 0022-2348; 1525-609X
• DOI: 10.1080/00222348.2013.810046

Two different types of calcium fluoride (CaF 2 ) particles were incorporated into a poly(ethylene terephthalate) (PET) matrix, fine particles (∼350 nm), and nanoparticles (∼70 nm). Both of them were synthesized by a chemical precipitation method using triethanolamine (TEA) as stabilizer. To obtain the nanoparticles, a greater amount of TEA was added during the synthesis in order to limit their growth. Therefore, unlike the fine particles, nanoparticles contained a greater amount of the stabilizer. Once CaF 2 particles were obtained, the composite materials were prepared by melt-blending PET and particles at different filler loadings. The influence of both kinds of particles on the non-isothermal crystallization behavior of PET was investigated by using differential scanning calorimetry and field emission scanning electron microscopy. The Jeziorny-modified Avrami equation was applied to describe the kinetics of the non-isothermal crystallization, and several parameters were analyzed (half-crystallization time, Avrami exponent, and rate constant). According to the results, it is clear that CaF 2 particles act as nucleating agents, accelerating the crystallization rate of PET. However, the effect on the crystallization rate was more noticeable with the addition of the fine particles where the surface plays an important role for epitaxial crystallization, while the addition of the nanoparticles with an organic surface coating resulted in a crystallization behavior similar to the observed for PET.