Abstract
Research on compostable bioplastics has recently obtained performances comparable to traditional plastics, like water vapor permeability, sealability, and UV transmission. Therefore, it is crucial to create new tools that help the developers of new polymeric composites study them quickly and cost-effectively. In this work, Raman spectroscopy (RS) was proposed as a versatile tool to investigate the degradation of biobased plastics after a stress test in water: this approach is a novelty for food packaging. Treatments at room temperature (RT) and 80 °C were selected, considering that these biopolymers can be used to packaging ready meals. The investigation was carried out on single-layer sheets of poly-lactic acid (PLA), cellulose ester (CE), poly-butylene succinate (PBS), poly-butylene adipate-co-terephthalate (PBAT), and a new composite material obtained by coupling CE and PBS (BB951) and PLA and CE (BB961). The vibrational modes of the water-treated materials at RT and 80 °C were compared to the Raman spectra of the pristine bioplastic, and the morphologies of the polymers were analyzed by scanning electron microscopy (SEM) and optical microscopy. Composite sheets were the plastics which were mostly affected by the 80 °C treatment in water, through changes in morphology (wrinkling with alternate white and transparent zones), as was especially the case for BB951. The Raman spectra acquired in different zones showed that the vibrations of BB951 were generally maintained in transparent zones but reduced or lacking in white zones. At the same time, the single-layer materials were almost unchanged. For BB961, the Raman vibrations were only slightly modified, in agreement with the visual inspection. The results suggest that RS detects the specific chemical bond that was modified, helping us understand the degradation process of biobased plastics after water treatment.
Highlights
Plastic derived from petroleum or fossil fuels is a cheap, versatile, lightweight, resistant, and widely used material in crucial sectors such as packaging, agriculture, automotive and electric appliances
The surface morphology of single layer bioplastics was investigated by means of FE-scanning electron microscopy (SEM): the corresponding images collected at low magnification (5K×) are shown in presents a surface with bubbles showing on top
Room temperature exposure to water produced little effect on the characteristic vibrations of polymers, while treatment in water at 80 ◦C affected the bioplastics in a way that depended on the type of polymer and was more severe in the case of composite layers
Summary
Plastic derived from petroleum or fossil fuels is a cheap, versatile, lightweight, resistant, and widely used material in crucial sectors such as packaging, agriculture, automotive and electric appliances. Companies need to characterize newly developed bioplastic through expensive and time-consuming certifications, and would be highly interested in portable instruments that could check the polymer composition or modifications when the packaging material is modified (by temperature, aging, contact with food processing apparatus, and so on). In this way, a developer can test a polymer’s resistance to degradation in a fast and reliable way before spending time and money on a new certification
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