Speaker
Dr
Lucia Calucci
(ICCOM-CNR)
Description
`Low density polyethylene (LDPE) is commonly used for food packaging [1]. The addition of nano-clays often improves the mechanical, thermal and gas-barrier properties of the polymer matrix, making the composite a potentially superior industrial product.
In this work, solid state NMR spectroscopy and $^{1}$H NMR relaxometry techniques were applied to a neat LDPE and a LDPE/montmorillonite nanocomposite sample [2] in order to investigate the effect of the filler on polymer morphology and dynamics, molecular level properties which are related to the mentioned macrocroscopic properties.
The studied LDPE sample showed a glass transition at -45$^\circ$C and a melting point at 114$^\circ$C. The analysis of $^{1}$H low field NMR Free Induction Decays in the temperature range between 26 and 100$^\circ$C allowed three components with different mobility to be identified: crystalline, amorphous, and rigid amorphous fractions. $^{13}$C direct excitation NMR spectra were also recorded at room temperature to further characterize these fractions. In addition, in order to get insight into the phase heterogeneity we measured the $^{1}$H longitudinal relaxation times in the laboratory frame (T$_{1}$) at 300 MHz and in the rotating frame (T$_{1\rho}$) using $^{13}$C detection through Cross Polarization Magic Angle Spinning (CP MAS) at room temperature and performed spin diffusion experiments. Moreover, the chain segmental and collective dynamics was characterised by measuring $^{1}$H T$_{1}$ at Larmor frequencies ranging from 10 kHz to 30 MHz, exploiting a Fast Field-Cycling NMR relaxometer in the 26-120$^\circ$C temperature interval. The results obtained for the neat polymer and the nanocomposite were compared and discussed.`
References
[1] Ray, S.; Quek, S. Y.; Easteal, A.; Chen, X. D. `$\textit{Int. J. Food Eng.}$` 2006, `$\textbf{2}$`(4), art. 5.
[2] Coiai, S.; Scatto, M.; Bertoldo, M.; Conzatti, L.; Andreotti, L.; Sterner, M.; Passaglia, E.; Costa, G.; Ciardelli, `$\textit{F. e-Polymers}$` 2009, `$\textbf{9}$`, 606-623.
Primary authors
Dr
Lucia Calucci
(ICCOM-CNR)
Dr
Silvia Pizzanelli
(ICCOM-CNR)
Co-authors
Mr
Carlo Andrea Massa
(IPCF-CNR)
Dr
Claudia Forte
(ICCOM-CNR)
