Effect of food additives on the microstructure of polyurethane films for packaging applications

ANBINDER, P.S.; PERUZZO, P.J.; AMALVY, J.I.

Campinas

Congreso; 18a. RAU Reunión Anual de Usuarios LNLS; 2008

Laboratorio Nacional de Luz Sincrotron - Brasil

The incorporation of an active compound to a polymeric matrix can provide distinctive functionalities as controlled release system of the active compound. The efect of additives on the morphological structure of a polymeric film is an important aspect in film characterization from a practical point of view, due to changes in permeability and mechanical properties. The objective of this study is to investigate the efects of common antioxidant molecules like butylated hydroxytoluene (BHT) and tocopherol (Toc) and antimicrobial compounds as the sodium salt of the ethylenediamine tetra acetic acid (EDTA-Na) and potassium sorbate (PS) on the morphological structure of polyurethane (PU) ¯lms based on IPDI/PPG1000. The infuence of additives on polymer structure was evaluated by SAXS. Measurements of ¯lms samples were performed at the SAXS2 beam line at the LNLS (Campinas, Brazil) using a monochromatic beam of wavelength 1.608 A and exposure time of 300 sec, and a sample-detector distance of 728.32 mm for values of scattering vector 0.02<q<0.355 ºA-1. Pure PU shows in the SAXS curve the typical shoulder at about 0.1 A-1 due to the hard segments/soft segments segregation and the interdomain spacing. Samples with BHT display a decrease on the intensity of this shoulder probably due to the BHT molecules break the segments interaction, leading therefore to a good incorporation of additive. The remaining SAXS curve does not show any change. In the other hand SAXS spectra of films with tocopherol do not show important diferences respect to pure PU, probably because of the bigger size of the tocopherol molecule compared with BHT. In this case, the microrange of heterogeneity in the PU matrix is not afected and phase segregation is expected. On the contrary, SAXS spectra of films doped with EDTA or PS show an important change at a q value around 0.08 ºA-1, increasing scattering intensity with increasing the additive content in the ¯lm. Unlike BHT, EDTA and SA are ionic compounds and speci¯c ionic interactions, preferentially with the urethane groups, are expected changing the size of aggregates.