Microwave-assisted green approach for graft copolymerization ofl-lactic acid onto starch

Effects of microwave radiation on the physicochemical properties, structure, and digestibility of the synthesized different crystal forms of malic acid starch ester

The effects of microwave combined with L-malic acid treatment on the degree of substitution (DS), structure, physicochemical properties, and digestibility of sweet potato starch (A-type), potato starch (B-type), and pea starch (C-type) were evaluated. The order of DS obtained was: DSM-POS > DSM-SPS > DSM-PES. Fourier transform-infrared spectroscopy (FT-IR) showed that the obtained modified starch produced a new absorption band at 1735 cm-1. Scanning electron microscopy (SEM) and polarized light microscopy indicated that different types of native starches exhibited different granular morphologies and appeared to have different degrees of damage, but still had polarized crosses after modification. Sweet potato starch had the smallest particle size, while potato starch had the largest. X-ray diffractometry (XRD) showed that the modified starches still retained the same crystal structure as the native starches, but the relative crystallinity decreased. The apparent viscosity and swelling power of modified starches dropped, but their water/oil holding capacity, amylose content, and resistant starch content all increased. The results demonstrate that the degree of influence on the structure, physicochemical properties, and digestibility of different starches varies under the same modification conditions.

Structural and property changes of starch derivatives under microwave field: A review

Native starches are commonly modified for desired properties because of their limited applications. Among various modifications, microwave irradiation has been gaining strong interests and becoming a focal area to transform starch during the last few years. Such interests reside in microwave irradiation's high heating rates, lesser extent of loss in nutritional qualities, and so on when compared with other approaches. This review summaries the effects of microwave field on the structural (e.g. morphology characteristic, lamellae structure, crystallinity, and molecular structure) and physicochemical properties (e.g. pasting properties and gelatinization) of naturally existing starch derivatives. Different microwave-assisted chemical derivatizations can directly or indirectly affect starch structure from the macroscopic to the microscopic level, thereby resulting in various functionalities. Moreover, conventional starch modification processes can be optimized by applying microwave irradiation to obtain modified starch with high degree of substitution and low viscosity. The future research will help to better understand the structural changes of microwave-assisted starch chemical derivatization and thereby creating a wide range of functionalities.

Copolymer Based on Polyglycerol-Acrylate-Lactate as Potential Water Viscosifier and Surfactant for Enhanced Oil Recovery

Polymer and surfactant flooding are widely applied processes in enhanced oil recovery (EOR) in which viscous polymers or surfactants aqueous solutions are introduced in oil reservoirs to rise the recovery of the remaining oil. In this regard, one of the challenges of EOR practices is the use of efficient but low-cost viscosifier and surfactant polymers. This work is aimed at synthesizing a polyglycerol derived from the biodegradable and nontoxic monomer, glycerol, and evaluating the effect of its copolymerization on rheological and interfacial properties, which were tested in water and brine for the former and in the water/oil system for the last properties. The copolymers were synthesized using a polyglycerol backbone, acrylic acid, lactic acid, and oleic acid. The chemical structure of copolymers was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The viscosity and the interfacial tension (IFT) of polymeric solutions were tested. Thus, the viscosity and surface performance of the prepared polymer solutions in distilled water and brine were analyzed according to the structure of the synthesized polymers. The results showed that the synthesized polymers modified water viscosity and surface tension between water and oil. The developed polymers could be candidates for applications in enhanced oil recovery and related applications.

Improved Thermal Processing of Polylactic Acid/Oxidized Starch Composites and Flame-Retardant Behavior of Intumescent Non-Wovens

Thermoplastic processing and spinning of native starch is very challenging due to (a) the linear and branched polymers (amylose and amylopectin) present in its structure and (b) the presence of inter-and-intramolecular hydrogen bond linkages in its macromolecules that restrict the molecular chain mobility. Therefore, in this study, oxidized starch (OS) (obtained after oxidation of native starch with sodium perborate) was melt-blended with polylactic acid (PLA) polymer to prepare PLA/OS blends that were then mixed together with ammonium polyphosphate (APP), a halogen-free flame retardant (FR) used as acid donor in intumescent formulations on twin-screw extruder to prepare PLA/OS/APP composites. OS with different concentrations also served as bio-based carbonic source in intumescent formulations. PLA/OS/APP composites were melt spun to multifilament fibers on pilot scale melt-spinning machine and their crystallinity and mechanical properties were optimized by varying spinning parameters. The crystallinity of the fibers was studied by differential scanning calorimetry and thermal stabilities were analyzed by thermogravimetric analysis. Scanning electron microscopy was used to investigate the surface morphology and dispersion of the additives in the fibers. Needle-punched non-woven fabrics from as prepared melt-spun PLA/OS/APP fibers were developed and their fire properties such as heat release rate, total heat release, time to ignition, residual mass % etc. by cone calorimetry test were measured. It was found that PLA/OS/APP composites can be melt spun to multifilament fibers and non-woven flame-retardant fabrics produced thereof can be used in industrial FR applications.

Cross-Linked Hydrophobic Starch Granules in Blends with PLA

The majority of native starch is used in the food sector and in the paper industry. Only a small amount is used in polymer engineering. One reason for the reluctance of the plastics processing industry to use starch as a filling material in polymer blends is the unsatisfactory mechanical behavior of starch when combined with thermoplastics. Another reason is the hydrophilicity of starch. In order to make these materials capable of competing, an amelioration of the mechanical properties is compulsory. By means of modifying the native starch and optimizing the compounding process, it is possible to improve the performance of starch blends, and, thus, increase the number of application areas of these materials. For this reason, native starch was modified with a cross-linking agent using a laboratory mixer. Subsequently, the modified starch and poly(lactic acid) were compounded using a co-rotating twin screw extruder. Cross-linking of the native starch in the laboratory mixer resulted in an increase in the mechanical strength of the starch blends. In addition, the blends with cross-linked starch displayed lower moisture absorption levels than blends with native starch as a filling material.