Il polietilene a bassa densita' (LDPE) e' comunemente usato per il packaging del cibo. L'aggiunta di nano-argille spesso ne migliora le proprieta' meccaniche, termiche e di barriera verso i gas. In questo lavoro, si sono applicate la spettroscopia NMR allo stato solido e la rilassometria protonica su un campione di LDPE e su un campione LDPE/montmorillonite per investigare l'effetto dell'argilla sulla morfologia e sulla dinamica del polimero.
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 1H 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 -45C and a melting point at 114C. The analysis of 1H low field NMR Free Induction Decays in the temperature range between 26 and 100C allowed three components with different mobility to be identified: crystalline, amorphous, and rigid amorphous fractions. 13C 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 1H longitudinal relaxation times in the laboratory frame (T1) at 300 MHz and in the rotating frame (T1) using 13C 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 1H T1 at Larmor frequencies ranging from 10 kHz to 30 MHz, exploiting a Fast Field-Cycling NMR relaxometer in the 26-120C 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. Int. J. Food Eng. 2006, 2(4), art. 5. [2] Coiai, S.; Scatto, M.; Bertoldo, M.; Conzatti, L.; Andreotti, L.; Sterner, M.; Passaglia, E.; Costa, G.; Ciardelli, F. e-Polymers 2009, 9, 606-623.
Polymer dynamics and morphology in LDPE nanocomposites studied by NMR spectroscopy and relaxometry
PIZZANELLI Silvia;CALUCCI Lucia;MASSA Carlo Andrea;FORTE Claudia
2017
Abstract
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 1H 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 -45C and a melting point at 114C. The analysis of 1H low field NMR Free Induction Decays in the temperature range between 26 and 100C allowed three components with different mobility to be identified: crystalline, amorphous, and rigid amorphous fractions. 13C 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 1H longitudinal relaxation times in the laboratory frame (T1) at 300 MHz and in the rotating frame (T1) using 13C 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 1H T1 at Larmor frequencies ranging from 10 kHz to 30 MHz, exploiting a Fast Field-Cycling NMR relaxometer in the 26-120C 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. Int. J. Food Eng. 2006, 2(4), art. 5. [2] Coiai, S.; Scatto, M.; Bertoldo, M.; Conzatti, L.; Andreotti, L.; Sterner, M.; Passaglia, E.; Costa, G.; Ciardelli, F. e-Polymers 2009, 9, 606-623.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
