Carbon Nitride Grafting Modification of Poly(lactic acid) to Maximize UV Protection and Mechanical Properties for Packaging Applications

Abstract

Due to their biobased nature and biodegradability, poly­(lactic acid) (PLA) rich blends are promising for processing in the packaging industry. However, pure PLA is brittle and UV transparent, which limits its application, so the exploration of nanocomposites with improved interfacial interactions and UV absorbing properties is worthwhile. We therefore developed and optimized synthesis routes for well-designed nanocomposites based on a PLA matrix and graphitic carbon nitride (g-C3N4; CN) nanofillers. To enhance the interfacial interaction with the PLA matrix, a silane-coupling agent (γ-methacryloxypropyl trimethoxysilane, KH570) is chemically grafted onto the CN surface after controlled oxidation with nitric acid and hydrogen peroxide. Interestingly, only 1 wt % of CNO-KH570, as synthesized under mild conditions, is needed to significantly improve the UV absorption, blocking even a large part of both UV-C, UV-B, and UV-A outperforming the UV absorption performance of PLA and, for instance, polyethylene terephthalate (PET). The low nanofiller loading of 1 wt % also results in a higher ductility with an increase in elongation at break (+73%), maintaining the tensile modulus. The results on a joint optimization of UV protection and mechanical properties are supported by a broad range of experimental characterizations, including FTIR, XRD, DSC, DSEM, FETEM, XPS, FTIR, TGA, and BET N2 adsorption–desorption analysis.

Playing with Low Amounts of Expanded Graphite for Melt-Processed Polyamide and Copolyester Nanocomposites to Achieve Control of Mechanical, Tribological, Thermal and Dielectric Properties

“…The introduction of filler thus clearly induces a ductile-brittle transition. Similarly, Zheng et al [20] reported an increase in tensile modulus and a significant decrease in elongation at break where HDPE was reinforced with 3 wt% of EG. Furthermore, the results are in line with the results found by Liu et al [55], as their results indicated a strong improvement in elastic modulus through the addition of 1 wt% of GO in a polyimide matrix.…”

“…It further follows from Figure 6c the virgin polymer materials showed strain hardening near the end of the tensile te with PA11 also showing some signs of necking. The composites, on the other hand, not show this ductile behaviour, as fillers within the polymer matrix acted as stress c centrators, therefore raising the localized stresses before failure occurred [20]. The in duction of filler thus clearly induces a ductile-brittle transition.…”

“…To alter/increase the EMI, EC, TC or mechanical properties of composites, carbonbased fillers [15] have been of increasing interest due to their high intrinsic EC and TC, stability, light weight and low cost [16,17]. Many allotropic forms of carbon, e.g., graphene, carbon nanotubes (CNTs), graphene oxide (GO) and expanded graphite (EG) [18], have been studied within the scope of material property modifications [19,20]. Graphene is a single sheet of carbon atoms, while GO is prepared by treating graphite flakes with oxidizing agents, introducing polar groups onto the graphite surface [19].…”

Fibrous Material Structure Developments for Sustainable Heterogeneous Catalysis – An Overview

“…Nanomaterials bring the highest specific surface area, and thus often an enhanced chemical reactivity. [3][4][5][6][7] Moreover, they often exhibit improved mechanical strength, hardness, and toughness compared to their bulk counterparts because the small size generally allows for better control over the arrangement of atoms and thus the creation of stronger bonds. [8][9][10] Examples are (semi-)metal oxides, active carbon, porous polymers, zeolites, and metal-organic frameworks (MOFs).…”