Facile Esterification of Degraded and Non-Degraded Starch

Starch ester film properties: The role of the casting temperature and starch its molecular weight and amylose content

Oleic acid and 10-undecenoic acid were used to esterify corn, tapioca, potato and a waxy potato starch, with a maximum degree of substitution of 2.4 and 1.9 respectively. The thermal and mechanical properties were investigated as a function of the amylopectin content and M_w of starch, and by the fatty acid type. All starch esters had an improved degradation temperature regardless of their botanical origin. While the T_g did increase with increasing amylopectin content and M_w, it decreased with increasing fatty acid chain length. Moreover, films with different optical appearances were obtained by varying the casting temperature. SEM and polarized light microscopy showed that films cast at 20 °C had porous open structures with internal stress, which was absent when cast at higher temperatures. Tensile test measurements revealed that films had a higher Young's modulus when containing starch with a higher M_w and amylopectin content. Besides that, starch oleate films were more ductile than starch 10-undecenoate films. In addition, all films were resistant to water at least up to one month, while some light-induced crosslinking took place. Finally, starch oleate films showed antibacterial properties against Escherichia coli, whereas native starch and starch 10-undecenoate did not.

A more efficient synthesis and properties of saturated and unsaturated starch esters

This work presents a series of starch esters synthesized via 1,5,7-triazabicyclo[4.4.0]-dec-5-ene (TBD) catalyzed transesterifications in dimethyl sulfoxide (DMSO). The reaction was performed with saturated and unsaturated fatty acids (8, 11, and 18 carbon atoms). The degree of substitution (DS) was raised by purging the reaction flask with nitrogen instead of simply performing the reaction under a nitrogen atmosphere. The increase of DS was most obvious for long-chain fatty acids, as an almost complete DS was observed for starch stearate (2.8) and starch oleate (2.7). The products were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction. Starch esters from unsaturated fatty acids have a lower T_g than their saturated analogues. Moreover, contact angle and moisture uptake measurements showed increased hydrophobicity for all starch esters in comparison to pristine starch. Our results show a more efficient method for synthesizing a biobased material that steers into the direction of a material that could replace conventional plastics.

Enzymatic transesterification of urethane-bond containing ester

Here we demonstrate the feasibility and successful application of enzymes in polyurethane network synthesis as well as occurring hurdles that have to be addressed when using urethanes synthesis substrates. The enzymatic transesterification of an urethane-bond containing monofunctional ester and a model alcohol carbitol using lipases is discussed. The reaction is optimized in terms of transesterification time and temperature, the reaction solvent, the possibility of a cosolvent and the alcohol amount, the used transesterification environment, and the biocatalyst. Enzymatic cross-linking of polyurethanes can open up a pool of new possibilities for cross-linking and related polyurethane network properties due to the enzymes high enantio-, stereo-, and regioselectivity and broad substrate spectrum.

Polyurethane Coatings Based on Renewable White Dextrins and Isocyanate Trimers

The polyurethane industry is strongly dependent on fossil-based polyols and polyisocyanates. Developing novel sustainable polyols from valuable biobased building blocks is a first step toward strong and durable development. The synthesis and properties of PU films based on pristine and acylated white dextrins (AVEDEX W80) as polyol and an aliphatic, low-viscosity, solvent-free triisocyanate based on hexamethylene diisocyanate (trimer-Desmodur N3300) as crosslinker is reported. After optimizing several conditions, such as the reaction time, reaction temperature, amount of solvent, isocyanate index, and amount per surface area, it is possible to obtain smooth PU films with good thermal properties.

Green Polyurethanes from Renewable Isocyanates and Biobased White Dextrins

Polyurethanes (PUs) are an important class of polymers due to their low density and thermal conductivity combined with their interesting mechanical properties—they are extensively used as thermal and sound insulators, as well as structural and comfort materials. Despite the broad range of applications, the production of PUs is still highly petroleum-dependent. The use of carbohydrates in PU synthesis has not yet been studied extensively, even though, as multihydroxyl compounds, they can easily serve as crosslinkers in PU synthesis. Partially or potentially biobased di-, tri- or poly-isocyanates can further be used to increase the renewable content of PUs. In our research, PU films could be easily produced using two bio-based isocyanates—ethyl ester L-lysine diisocyanate (LLDI] and ethyl ester l-lysine triisocyanate (LLTI)—, one commercial isocyanate—isophorone diisocyanate (IPDI), and a bio-based white dextrin (AVEDEX W80) as a crosslinker. The thermal and mechanical properties are evaluated and compared as well as the stability against solvents.

A new way to improve physicochemical properties of potato starch

Starch is an important class of macromolecules for human nutrition. However, its rapid digestibility leads to a high amount of glucose released into the blood and contributes to a high risk of obesity and type II diabetes. For these reasons, Heat-moisture treatment (HMT) of the starch was applied prior to complexation with linoleic acid to obtain a desired physicochemical properties while preserving its granular structure. The thermal properties, analyzed by DSC, implied that the HMT enhanced the formation of amylose-linoleic acid complexes, particularly when the complexation was succeeded at 70 °C. The viscosity behavior studied by RVA demonstrated a higher pasting temperature and lower peak viscosity due to less swelling. The granule-like structure remained after complexation at 70 °C for 30 min and followed by RVA to 85 °C. The combination of the HMT and linoleic acid addition improved the stability of the starch granules towards heating and shearing.