Processing and properties of PLA/thermoplastic starch/montmorillonite nanocomposites

Polymer International, 2019

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Heliyon, 2019

A structural study about the changes induced by plasticization of native corn starch was carried out in this work. The influence of talc nanoparticles presence during starch thermal processing was also evaluated. Macroscopic observation of the granules appearance evolution during melt-mixing and thermo-compression was supported by a theoretical description related to these processing methods. Melt-mixing induced a polymorphic transformation from A-to V h-type and a reduction in the degree of crystallinity. Homogenous appearance of the plasticized starch was in accordance to the disruption of granules integrity, evidenced by SEM. This observation agreed to the distinctive XRD pattern of plasticized starch from unprocessed granules. Talc incorporation did not require the adjustment of processing parameters in order to obtain a homogenous thermoplastic material, with an adequate particles distribution within the matrix. Regardless talc presence, plasticized starch presented a V h-type crystalline structure. Thermo-compression led to particles alignment promoted by talc laminar morphology.

2007

Starches, including high amylose cornstarch, normal cornstarch, and waxy cornstarch, were gelatinized and mixed with nanoclay aqueous dispersion and different amount plasticizer. The mixtures were then cast onto Teflon plate and allowed to dry naturally. The dried film were conditioned in an environmental chamber at 25°C, and 50% relative humidity for more than 24 hours before tested for water permission, mechanical strength and XRD. The intercalation of starches into nanoclay depended on the chain length of starch main chain and of side chain in absence of plasticizer. The shorter the chain length of starch was, the higher the degree of intercalation. Plasticizers had much smaller molecular weight than that of starch, plasticizer instead of starch intercalated into the nanoclay as shown by XRD when starch films were prepared in the presence of plasticizer.

Macromolecules, 1996

Industrial Crops and Products, 2011

A simple method based on the combination of the intercalation from solution and melt-processing preparation methods was used to prepare highly exfoliated and compatible thermoplastic starch (TPS) and montmorillonite clay (MMT) nanocomposites. The effects of the MMT content on the thermal, structural, and mechanical properties of the nanocomposites were investigated. XRD diffraction was used to investigate the MMT exfoliation/intercalation degrees in the TPS matrix. Data from thermogravimetric analysis and differential scanning calorimetry revealed that the addition of MMT increased the thermal stabilities of TPS nanocomposites. Young's modulus and tensile strength increased from 8.0 to 23.8 MPa and 1.5 to 2.8 MPa with an increasing MMT content from 0 to 5 wt% without diminishing their flexibility. The improvement in such properties can be attributed to the good dispersion/exfoliation of MMT in the TPS matrix. Combining both methods, it was possible to obtain homogenous and transparent nanocomposites with excellent thermal and mechanical properties for application as packaging materials.

IOP Conference Series: Materials Science and Engineering, 2019

Nature has developed several biodegradable materials which can be used in architectural and civil engineering to address the challenges of a more sustainable construction and housing industry to mitigate and adapt to climate change. Nowadays, there is an increasing interest in using biodegradable polymers from renewable resources such as starch and cellulose derivatives in the global plastic industry in order to reduce the environmental pollution caused by the petroleum-based traditional synthetic plastic waste. In this study, conventional composite and nanocomposite films of plasticized corn starch were prepared with sodium montmorillonite clay by a solution mixing procedure with glycerol as a plasticizer. The obtained nanocomposite microstructures were ascertained by XRD and SEM techniques and the tensile properties were investigated as a function of clay and plasticizer contents, in order to analyze the mechanical properties of the films.

Polymers

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 variat...

Starches used to develop biodegradable composites belong to different botanical sources that exhibit different microstructures and morphologies. This results in confused relationship and no comparison of data for applications. In this work, the most popular ten different starches were used as model materials to investigate the relationship between starch microstructure and the performance of poly(lactic acid) (PLA)/starch composites. It was found that: (a) composites filled with either well-sized (small-sized and non-agglomerated) starch granules or those containing high amylose content (G-50 and G-80) improves the reinforcing ability of PLA, with least reduction in deformation; (b) aggregation tendency of small-sized starch granules can be controlled using surface modification approach that not only reduces the phase-separation between starch and PLA but also improves the dispersion; and (c) no discernible relationship exists between the starches, from different botanical sources, and the thermal performance of PLA/ starch composites. The results provide practical guidelines to develop starch-based biodegradable composites for commercial applications.

Food Hydrocolloids, 2015

This work analyzed the effect of talc morphology on structural characteristics and final properties of thermoplastic corn starch (TPS). In this sense, composite films based on TPS containing talc nanoparticles were obtained by melt-mixing and thermo-compression. Talc samples with different morphological characteristics (platy-microcrystalline and blocky-macrocrystalline), derived from their formation process, were used. Platy and blocky morphology was distinguished by Scanning Electron Microscopy performed on composites films. Microcrystalline morphology induced smaller TPS crystallites than macrocrystalline one, indirectly evidenced by X-Ray Diffraction and Differential Scanning Calorimetry. Crystalline character of talc particles also affected visible and UV barrier capacity of TPS films. Blocky morphology of mineral filler led to the highest reduction of TPS water vapor permeation. Both talc samples acted as matrix reinforcement agents. However, macrocrystalline particles induced the major changes on elastic modulus and tensile strength, without affecting films ductility.