Combining Asymmetrical Flow Field-Flow Fractionation with Light Scattering and Inductively Coupled Plasma Mass Spectrometric Detection for Characterization of Nanoclay used in Biopolymer Nanocomposites
Résumé
It is expected that biopolymers obtained from renewable resources will in due course become fully competitive with fossil fuel-derived plastics as food packaging materials. In this context, biopolymer nanocomposites are a field of emerging interest since such materials can exhibit improved mechanical and barrier properties and be more suitable for a wider range of food packaging applications. Natural or synthetic clay nanofillers are being investigated for this purpose in the current NanoPack project funded by the Danish Strategic Research Council. In order to detect and chracterize the size of clay nanoparticulates, an analytical system combining asymmetrical flow field-flow fractionation (AF4) with multi angle light scattering detection (MALS) and inductively coupled plasma mass spectrometry (ICP-MS) is presented here. In a migration study we tested a biopolymer nanocomposite consisting of polylactide (PLA) with 5 % Cloisite®30B, a derivatised montmorillonite clay, as filler. Based on AF4-MALS analyses we found that particles ranging from 50 to 800 nm in radius indeed migrated into the 95 % ethanol used as food simulant. The full hyphenated AF4-MALS-ICP-MS system showed however, that none of the characteristic clay minerals were detectable, and we conclude that clay nanoparticles was absent in the migrate. Finally, by means of centrifugation experiments, a platelet aspect ratio of 320 was calculated for montmorillonite clay using AF4-MALS for platelet size measurements.
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