A Study on Thermal Behaviour of Thermoplastic Starch Plasticized by [Emim] Ac and by [Emim] Cl

Starch/PVOH aqueous solutions: a chemical-physical characterization

This work investigates the relationship between the structure and physicochemical properties of three different starches in starch/polyvinyl alcohol aqueous solutions. For this purpose, accurate nuclear magnetic resonance (NMR) analyses were performed to determine the role that the starch structure plays in the formation of binder solutions. Moreover, a dynamic shear rheometer (DSR) was used to investigate the mechanical properties of the solutions and correlate them with the structure of each starch. Complete characterization of the analysed starches and the starch/PVOH solutions was also carried out through light scattering measurements. Furthermore, by crossing the data coming from NMR and light scattering with those coming from rheology, the best solution was identified. Finally, to confirm the interaction mechanism between starch and PVOH, thermogravimetric analysis and an NMR study, using 1H and 13C NMR spectra, were carried out on the film obtained from the best solution. The analyses carried out showed that PVOH has a stabilizing effect on starch/PVOH solutions, and the starch with the greatest branching degree is the one that forms a more structured network.

Use of Raw Peach Gum as a Sustainable Additive for the Development of Water-Sensitive and Biodegradable Thermoplastic Starch Films

In this study, formulations of thermoplastic starch (TPS) with 5, 10, and 15 parts per hundred resin (phr) of raw peach gum (PG) were prepared by melt extrusion followed by injection molding to obtain standard specimens for characterization. In addition, biodegradable films were developed by compression molding. It was determined that TPS with 5 phr and 10 phr of PG presented similar mechanical behavior to pure TPS after the processing. However, results indicated that adding PG in 10 phr slowed down the starch's retrogradation, delaying the TPS structure's stiffening. Moreover, the TPS-PG formulations presented improved solubility, which increased by 24% with 10 and 15 phr of PG compared to that shown for TPS. Additionally, PG enhanced the compostability of TPS, causing the sample to disintegrate in a shorter period. In conclusion, it was determined that raw PG added in 10 phr could be added as a sustainable additive to modify the biodegradation and water sensitivity of TPS without affecting its mechanical behavior after processing and delaying the retrogradation of the TPS structure, increasing its shelf life.

Co-Plasticization of Starch with Glycerol and Isosorbide: Effect on Retrogradation in Thermo-Plastic Cassava Starch Films

Thermoplastic starch (TPS) has emerged as an essential alternative to produce environmentally friendly packaging; however, retrogradation is a disadvantage that affects its shelf life. This study analyzed the co-plasticizing effect of isosorbide on the mechanical, thermal, physicochemical, and microstructural properties and the retrogradation of films obtained by blown film extrusion from thermoplasticized starch with mixtures of glycerol and isosorbide in different ratios (3:0, 2:1, 1:2, and 0:3, respectively). The results showed that the higher concentration of isosorbide significantly increased the tensile strength; however, it reduced the elongation. Retrogradation modeled using the Avrami equation showed that the presence of isosorbide reduced the retrogradation rate (k) and modified the recrystallization mechanism (n). The relative crystallinity in the plasticized TPS films was reduced to 89%, and the adsorption significantly decreased. Isosorbide was very important in reducing the retrogradation of TPS. The best performance was obtained with the 2:1 ratio of glycerol/isosorbide due to the synergistic effect between the plasticizers. The results would allow tuning the properties of TPS films by combining glycerol/isosorbide in different ratios, which enables the design of materials tailored to potential application requirements.

Advances in green solvents for production of polysaccharide-based packaging films: Insights of ionic liquids and deep eutectic solvents

The problems with plastic materials and the good film-forming properties of polysaccharides motivated research in the development of polysaccharide-based films. In the last 5 years, there has been an explosion of publications on using green solvents, including ionic liquids (ILs), and deep eutectic solvents (DESs) as candidates to substitute the conventional solvents/plasticizers for preparations of desired polysaccharide-based films. This review summarizes related properties and recovery of ILs and DESs, a series of green preparation strategies (including pretreatment solvents/reaction media, ILs/DESs as components, extraction solvents of bioactive compounds added into films), and inherent properties of polysaccharide-based films with/without ILs and DESs. Major reported advantages of these new solvents are high dissolving capacity of certain ILs/DESs for polysaccharides (i.e., up to 30 wt% for cellulose) and better plasticizing ability than traditional plasticizers. In addition, they frequently display intrinsic antioxidant and antibacterial activities that facilitate ILs/DESs applications in the processing of polysaccharide-based films (especially active food packaging films). ILs/DESs in the film could also be further recycled by water or ethanol/methanol treatment followed by drying/evaporation. One particularly promising approach is to use bioactive cholinium-based ILs and DESs with good safety and plasticizing ability to improve the functional properties of prepared films. Whole extracts by ILs/DESs from various byproducts can also be directly used in films without separation/polishing of compounds from the extracting agents. Scaling-up, including costs and environmental footprint, as well as the safety and applications in real foods of polysaccharide-based film with ILs/DESs (extracts) deserves more studies.

Effect of Agar on the Mechanical, Thermal, and Moisture Absorption Properties of Thermoplastic Sago Starch Composites

Thermoplastic starch is a material that has the potential to be environmentally friendly and biodegradable. However, it has certain drawbacks concerning its mechanical performance and is sensitive to the presence of moisture. The current study assessed agar-containing thermoplastic sago starch (TPSS) properties at various loadings. Variable proportions of agar (5%, 10%, and 15% wt%) were used to produce TPSS by the hot-pressing method. Then, the samples were subjected to characterisation using scanning electron microscopy (SEM), mechanical analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and moisture absorption tests. The results demonstrated that adding agar to starch-based thermoplastic blends significantly improved their tensile, flexural, and impact properties. The samples' morphology showed that the fracture had become more erratic and uneven after adding agar. FT-IR revealed that intermolecular hydrogen bonds formed between TPSS and agar. Moreover, with an increase in agar content, TPSS's thermal stability was also increased. However, the moisture absorption values among the samples increased slightly as the amount of agar increased. Overall, the proposed TPSS/agar blend has the potential to be employed as biodegradable material due to its improved mechanical characteristics.

Preparation of chemical staple fibers by plasticizing bleached coniferous pulps with 1-allyl-3-methylimidazolium chloride

In this study, we prepared chemical staple fibers (CSFs) by plasticizing bleached coniferous pulps (BCPs) with 1-allyl-3-methylimidazolium chloride (AMIMCl) under high temperature and pressure.

A novel method to prepare chemical fibers by plasticizing cotton with 1-allyl-3-methylimidazolium chloride

In this study, we developed a novel method to prepare chemical fibers by plasticizing cotton with 1-allyl-3-methylimidazolium chloride (AMIMCl) under high temperature and pressure. Cotton was homogeneously mixed with AMIMCl by kneading in a certain mass proportion. It would be a sheet after hot-pressing and this process could be repeated several times. The morphologies of chemical fibers showed that cotton was successfully plasticized by AMIMCl with the crystallinity of the chemical fibers increased by about 15%. Differential scanning calorimetry (DSC) showed that the glass transition temperature (T_g) occurred in chemical fibers and we could further verify cotton was plasticized by AMIMCl. This simple and green method will be helpful to modify and broaden the application field of cotton.

Narrowing the Gap for Bioplastic Use in Food Packaging: An Update

Plastic production has outgrown most other man-made materials, with more than 90% being petroleum-based and nonbiodegradable. Packaging, primarily food packaging, consumes the most plastic and is the largest contributor to municipal solid waste. In addition, its dependence on crude oil feedstock makes the plastic industry unsustainable and renders plastic markets vulnerable to oil price volatility. Therefore, the development of bioalternatives to conventional plastics is now a priority of the food packaging industry. Bioplastics are polymers that are either biobased (fully or partially), or biodegradable, or both. This review aims to provide an insightful overview of the most recent research and development successes in bioplastic materials, focusing on food packaging applications. Bioplastics are compared to their conventional counterparts with respect to their mechanical, thermal, barrier, and processability properties. The gaps between bio- and conventional plastics in food packaging are elucidated. Potential avenues for improving bioplastic properties to broaden their food packaging applications are critically examined. Furthermore, two of the most controversial topics on bioplastic alternatives, sustainability assessment and their impact on the plastic waste management system, are discussed.

Comparative study on properties of starch films obtained from potato, corn and wheat using 1-ethyl-3-methylimidazolium acetate as plasticizer

Starch films are gaining attention as substitutes of synthetic polymers due to their biodegradability and low cost. Some ionic liquids have been postulated as alternatives to glycerol, one of the best starch plasticizers, due to their great capacity to form hydrogen bonds with starch and hence great ability of preventing starch retrogradation and increasing film stability. In this work, [emim⁺][Ac^-]-plasticized starch films were prepared from potato, corn and wheat starch. The effect of starch molecular structure in terms of granular composition (amylose and phosphate monoester contents) and molecular weight (M_w) on film properties was evaluated. Potato starch films were the most amorphous because of the higher M_w and phosphate monoester content of potato starch, both contributing to a lower rearrangement of the starch chains making the crystallization process difficult. In contrast, corn and wheat starches lead to more crystalline films because of their lower M_w, which may imply higher mobility and crystal growth rate, and lower phosphate monoester content. This more crystalline structure could be the responsible of their better mechanical properties. [emim⁺][Ac^-] can be considered suitable for manufacturing starch films showing corn and wheat starch films similar properties to synthetic low-density polyethylene, but involving a simple and environmentally-friendly process.