3.- Ávila-Orta, C., Espinoza-González, C., Martínez-Colunga, G., Bueno-Baqués, D., Maffezzoli, A. and Lionetto, F. (2013), An Overview of Progress and Current Challenges in Ultrasonic Treatment of Polymer Melts. Adv. Polym. Technol., 32: E582–E602. doi: 10.1002/adv.21303
† This paper was presented at Theplac2011, June 23–24, 2011, Lecce, Italy.
An overview of the current state of art of the ultrasonic treatment technology applied to polymer melts is presented. The research and technological advancements of the ultrasonic treatment as applied to development of polymeric materials are discussed. An analysis of the technological progress shows that the mechanism of the effects of ultrasound on polymer melts is not fully understood at present. Such lack in fully understanding the mechanism could limit the use of this versatile technology in future applications. Based on the critical analysis of the research progress to date, some key issues for a deeper understanding of the chemical and physical effects of ultrasound on polymer melts are identified. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E582–E602, 2013;
4.- Carlos Alberto Ávila-Orta, Pablo González-Morones, Carlos José Espinoza-González, Juan Guillermo Martínez-Colunga, María Guadalupe Neira-Velázquez, Aidé Sáenz-Galindo and Lluvia Itzel López-López (2013). Toward Greener Chemistry Methods for Preparation of Hybrid Polymer Materials Based on Carbon Nanotubes, Syntheses and Applications of Carbon Nanotubes and Their Composites, Dr. Satoru Suzuki (Ed.), ISBN: 978-953-51-1125-2, InTech, DOI: 10.5772/51257. Available from: http://www.intechopen.com/books/syntheses-and-applications-of-carbon-nanotubes-and-their-composites/toward-greener-chemistry-methods-for-preparation-of-hybrid-polymer-materials-based-on-carbon-nanotub
This chapter is about the microwaves, ultrasound and plasma assisted functionalization of CNTs as greener chemistry methods to produce hybrid polymer materials. After a brief overview on preparation of hybrid polymer materials containing CNTs, it is presented the physical principles, mechanisms and processing conditions involved in the functionalization of CNTs for each of these “Green” chemistry methods, and then we present our point of view on challenges and opportunities in both the immediate and long-term future.
2.- Heriberto Rodríguez-Tobías, Graciela Morales, Javier Enríquez, Carlos Espinoza-González and Daniel Grande (2015). Use of Micro- and Nano-ZnO particles as Catalysts for the Microwave-Assisted Polymerization of D,L-lactide. MRS Proceedings, 1767, pp 3-9. doi:10.1557/opl.2015.220.
The use of a catalyst is required to synthesize poly(D,L-lactide) (PLA) and tin (II) 2-ethylhexanoate could be highlighted among them. However, this kind of catalysts can produce bio-dangerous compounds limiting the PLA in medical applications, therefore there is a need to investigate novel bio-safe catalysts. Taking into account this problem, this communication reports the use of micro- and nano-ZnO particles as catalysts for the microwave-assisted polymerization of D,L-lactide. By microwave heating a high monomer conversion (higher than 95%) was achieved in a relatively short reaction time (3 hours). Morphology/size and concentration of ZnO particles presented a strong effect on the production of PLA, star-like microparticles leaded to conversion ca. 25%, well below to the values achieved with the nanoparticles. Furthermore, the formation of a ZnO-PLA hybrid was evidenced by spectroscopic and thermal characterization techniques. The methodology herein developed represents a new pathway for the green synthesis of PLA.
1.- C., Espinoza-González, Ávila-Orta, C., Martínez-Colunga, G., Maffezzoli, A. and Lionetto, F. (2016), A Measure of CNTs Dispersion in Polymers with Branched Molecular Architectures by UDMA. IEEE Transactions on Nanotechnology Vol. 15 (5), pp 731-737.
† This paper was presented at NanoFim 2015, June 24–25, 2015, Lecce, Italy.
The need for new measurement techniques able to assess the nanofiller dispersion is still receiving great consideration when nanocomposites are developed. This occurs since different routes to disperse nanostructures generate molecular changes in polymer matrices that promote complex polymer-polymer and polymer-nanofiller interactions, which make difficult a suitable estimation of the dispersion. In this work, ultrasonic waves at different frequencies and power were used for preparing nanocomposite samples and for evaluating the nanofiller dispersion. First, a patented method was used to disperse multi wall carbon nanotubes (MWCNTs) in polyamide 12 through extrusion assisted by low-frequency and high power ultrasound (with frequency ranging between 20 and 50 kHz). This “green” processing method was able to induce different states of dispersion of the nanofillers, as well as chemical modifications to polymer chains promoting branching reactions. Then, ultrasonic dynamic mechanical analysis (UDMA with ultrasound frequency in the MHz range) was used to estimate the dispersion of the different nanocomposite samples. Compared to rheological measurement methods, UDMA provided a better estimation of the quality of dispersion, being sensitive both to the complex molecular architectures in polymer matrices and to the scattering due to MWCNT agglomerates.