Biodegradable polymer-clay composites produced with functionalized patagonian bentonite precur-sors

A. E. BIANCHI; L. JUNCIEL; G. A. ECHEVERRÍA; I.L. TORRIANI; P. EISENBERG; A. F. BOTANA; M. MOLLO; R.M. TORRES SANCHEZ; G. PUNTE

Santa Marta

Congreso; LATIN AMERICAN SEMINAR OF ANALYSIS BY X-RAY TECHNIQUES (SARX 2012); 2012

Universidad Industrial de Santander

Polymer composite films (PCF), based on semicrystalline biodegradable thermoplastic polyester, polycaprolactone (PCL), and a functionalized Patagonian bentonite were produced. The employed bentonite is predominately sodium montmorillonite (MMT), structural formula: [(Si3.89 Al0.11) (Al1.43 Fe0.26 Mg0.30)] M+0.41, cation exchange capacity (CEC): 174 meq/100g [1] and the organoclays had been prepared by addition of 1 and 2 CEC of hexadecyltrimethyl-ammonium (HDTMA) and octadecyl-trimethyl-ammonium  (ODTMA) to raw MMT diluted in deionized water and were fully characterized [2]. PCL/clay composites, with 5 per cent of clay content in weight, were synthesized by melt intercalation in a Brabender Plasticorder mixing chamber at 100 C, their thermal behavior was investigated by DSC. No difference was detected between melting point of PCL and those ones of the PCF, while a small decrease in the degree of crystallinity for PCF coming from 2 CEC loading organoclays could be perceived. SAXS and WAXS data analysis showed that organoclays expansion was not lost in the PCF. However, not all PCF present the same characteristics. PCL/ODTMA1 and PCL/HDTMA2 keep the Bragg reflections observed in the WAXS region in the precursor organoclays and increase the proportion of clay expanded to d001= 4.08 and 3.93nm, respectively, as indicated by the noticeable Bragg peak in the SAXS region. On the other hand, in the other PCF lower intensity and much larger broadening of the (001) reflections corresponding to different degree of expansion present in both WAXS and SAXS regions were observed. Bragg peaks in SAXS regions were located at 5.32 and 4.13 nm  and 5.37 and 3.32 nm and for PCL/ODTMA2 and PCL/HDTMA1, respectively. Dielectric measurements showed that all the films present the maximum in the dielectric constant at the lowest frequency explored, 0.1 Hz, and a steady diminution as the frequency increases up to 1MHz. PCF showed a dielectric constant higher than that of the PCL film up to approximately 50Hz. In PCF containing organoclays with 1 and 2 CEC loading of HDTMA, the dielectric constant is about double of the value found in the PCL film, disparity reduces to about 18per cent. at about 1kHz. The dielectric loss is also higher in PCF than in PCL for low frequencies. However, differences gradually decrease and PCF present comparable values to those of PCL within the frequency range 50 Hz to 1 MHz. [1] Magnoli. A. P. et al. (2008) Appl. Clay Sci. 40, 63-71.[2] Bianchi et al. ODTMA and HDTMA organomontymorillonites characterization: new insight by WAXS, SAXS and surface charge. Aceptado en revisión  Appl. Clay Sci.