The Role of Structure and Interactions in Thermoplastic Starch-Nanocellulose Composites

Processing, Properties, Modifications, and Environmental Impact of Nanocellulose/Biopolymer Composites: A Review

The increasing concerns about plastic pollution and climate change have encouraged research into bioderived and biodegradable materials. Much attention has been focused on nanocellulose due to its abundance, biodegradability, and excellent mechanical properties. Nanocellulose-based biocomposites are a viable option to fabricate functional and sustainable materials for important engineering applications. This review addresses the most recent advances in composites, with a particular focus on biopolymer matrices such as starch, chitosan, polylactic acid, and polyvinyl alcohol. Additionally, the effects of the processing methods, the influence of additives, and the outturn of nanocellulose surface modification on the biocomposite's properties are outlined in detail. Moreover, the change in the composites' morphological, mechanical, and other physiochemical properties due to reinforcement loading is reviewed. Further, mechanical strength, thermal resistance, and the oxygen-water vapor barrier properties are enhanced with the incorporation of nanocellulose into biopolymer matrices. Furthermore, the life cycle assessment of nanocellulose and composites were considered to analyze their environmental profile. The sustainability of this alternative material is compared through different preparation routes and options.

The Effect of Surface Characteristics of Clays on the Properties of Starch Nanocomposites

In this research, different clays such as laponite and montmorillonite (NaMMT) are used as fillers in the preparation of thermoplastic starch/clay nanocomposites. Thin films are produced by casting and evaporation in a wide composition range, using glycerol as the plasticizer at two different concentrations. The surface energy of clay fillers is measured by inverse gas chromatography (IGC); X-ray diffraction (XRD) and light transmission measurements (UV-VIS) are carried out to characterize the structure of nanocomposites; and mechanical properties and water vapor permeability are also studied. While all the starch/montmorillonite nanocomposites possess intercalated structures, significant exfoliation can be noted in the starch/laponite nanocomposites, mainly at low clay contents. Due to the larger surface energy of montmorillonite, stronger polymer/clay interactions and better mechanical properties can be assumed in starch/NaMMT composites. The smaller surface energy of laponite, however, can facilitate the delamination of laponite layers. Thus, the specific surface area of laponite can be further increased by exfoliation. Based on the results, the better exfoliation and the much larger specific surface area of laponite lead to higher reinforcement in starch/laponite nanocomposites.

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

Recently, hybrid fillers have been widely used to improve the properties of biopolymers. The synergistic effects of the hybrid fillers can have a positive impact on biopolymers, including thermoplastic corn starch film (TPCS). In this communication, we highlight the effectiveness of hybrid fillers in inhibiting the aging process of TPCS. The TPCS, thermoplastic corn starch composite films (TPCS-C), and hybrid thermoplastic corn starch composite film (TPCS-HC) were stored for 3 months to study the effect of hybrid filler on the starch retrogradation. TPCS-C and TPCS-HC were prepared by casting method with 5 wt% of fillers: nanocellulose (NC) and bentonite (BT). The alteration of the mechanical properties, aging behavior, and crystalline structure of the films were analyzed through the tensile test, Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and water absorption analysis. The obtained data were correlated to each other to analyze the retrogradation of the TPCS, which is the main factor that contributes to the aging process of the biopolymer. Results signify that incorporating the hybrid filler (NC + BT) in the TPCS/4BT1NC films has effectively prevented retrogradation of the starch molecules after being stored for 3 months. On the contrary, the virgin TPCS film showed the highest degree of retrogradation resulting in a significant decrement in the film’s flexibility. These findings proved the capability of the green hybrid filler in inhibiting the aging of the TPCS.