Green Nanocomposites Based on Thermoplastic Starch: A Review

Abstract

The development of bio-based materials has been a consequence of the environmental awareness generated over time. The versatility of native starch is a promising starting point for manufacturing environmentally friendly materials. This work aims to compile information on the advancements in research on thermoplastic starch (TPS) nanocomposites after the addition of mainly these four nanofillers: natural montmorillonite (MMT), organically modified montmorillonite (O-MMT), cellulose nanocrystals (CNC), and cellulose nanofibers (CNF). The analyzed properties of nanocomposites were mechanical, barrier, optical, and degradability. The most important results were that as the nanofiller increases, the TPS modulus and strength increase; however, the elongation decreases. Furthermore, the barrier properties indicate that that the incorporation of nanofillers confers superior hydrophobicity. However, the optical properties (transparency and luminosity) are mostly reduced, and the color variation is more evident with the addition of these fillers. The biodegradability rate increases with these nanocompounds, as demonstrated by the study of the method of burial in the soil. The results of this compilation show that the compatibility, proper dispersion, and distribution of nanofiller through the TPS matrix are critical factors in overcoming the limitations of starch when extending the applications of these biomaterials. TPS nanocomposites are materials with great potential for improvement. Exploring new sources of starch and natural nano-reinforcement could lead to a genuinely eco-friendly material that can replace traditional polymers in applications such as packaging.

Monomers and Macromolecular Materials from Renewable Resources: State of the Art and Perspectives

“…The research on starch-based materials is mostly based on the design of novel systems—mainly blends and composites—aiming at overcoming some practical drawbacks of TPS, whose implementation has been limited by its tendency to absorb moisture and thus a loss of mechanical properties. The efforts devoted to the association of TPS with natural montmorillonite, organically modified montmorillonite, cellulose nanocrystals, and cellulose nanofibers were discussed [ 53 ], with particular attention directed to the ensuing properties of composites, such as biodegradability, mechanical, barrier, and optical properties. In fact, the association between starch and (nano)celluloses has been vastly exploited in recent literature, and some approaches include the incorporation of starch into non-renewable polymers aiming at reducing the dependence on petroleum-based macromolecular materials.…”

Thermoplastic Starch-Based Blends with Improved Thermal and Thermomechanical Properties

“…For example, cassava starch is 17% amylose and 83% amylopectin, while maize starch is 28% amylose and 72% amylopectin [ 8 ]. Native starch has no plastic properties; however, when subjected to stress, under the action of temperature and in the presence of a plasticizer, a thermoplastic starch (TPS) can be obtained [ 11 ]. A TPS is meltable and processable by conventional processing methods.…”

Effective Aging Inhibition of the Thermoplastic Corn Starch Films through the Use of Green Hybrid Filler

“…Glycerol and water can effectively reduce the intermolecular force of granule starch and loosen up the dense packing structure. Full disruption of the starch structure can be achieved through the presence of plasticizers and a sufficient supply of thermomechanical energy [7].…”

“…Many factors can lead to the retrogradation of the TPS films, such as humidity, storage time, and glass-transition temperature, Tg [7]. Retrogradation is a process of reconstruction of the crystalline structure of starch chains.…”