Abstract
Development of biodegradable materials for packaging is an issue of the utmost importance. These materials are an alternative to petroleum-based polymers, which contribute to environment pollution after disposal. In this work, graphene oxide (GO) and glucose-reduced graphene oxide (rGO-g) were incorporated to thermoplastic starch (TPS) by melt extrusion. The TPS/GO and TPS/rGO-g composites had their physical properties and biodegradability compared. X-ray diffraction (XRD) showed that the type of graphene used led to different dispersion levels of graphene sheets, and to changes in the crystalline structure of TPS. Tensile tests carried out for the compression-molded composites indicated that TPS/rGO-g composites presented better mechanical performance. The Young’s modulus (E) increased from E = (28.6 ± 2.7) MPa, for TPS, to E = (110.6 ± 9.5) MPa and to (144.2 ± 11.2) MPa for TPS with rGO-g incorporated at 1.0 and 2.0 mass% content, respectively. The acid groups from graphene derivatives promoted glycosidic bond breakage of starch molecules and improved biodegradation of the composites. GO is well-dispersed in the TPS matrix, which contributes to biodegradation. For TPS/rGO-g materials, biodegradation was influenced by rGO-g dispersion level.
Highlights
Petroleum-based plastics are inexpensive, durable and lightweight materials, present in our daily lives
graphene oxide (GO) is well-dispersed in the thermoplastic starch (TPS) matrix, which contributes to biodegradation
The mechanism of GO reduction is attributed to the alkali conversion of glucose into fructose [17,18]
Summary
Petroleum-based plastics are inexpensive, durable and lightweight materials, present in our daily lives. Microplastics are small pieces of synthetic materials, less than 5 mm in length, which have increasingly been found in the environment [1,2]. Starch-based plastics have emerged because of their relatively low cost, renewability and biodegradability in most environments [3,4]. This is because of its high hydrophilicity, which results in poor mechanical properties as it ages [7]. To solve this drawback, blending TPS with less hydrophilic polymers, or incorporating inorganic nanoparticles, has been addressed as alternatives to improve its physical properties [5,8]
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