An Investigation of the Effect of Semi-Acetal Formation on the Properties of Dialdehyde Starch and its Thermoplastic Blend with Glycerol

Abstract

Dialdehyde sweet potato starch (DASS) with various aldehyde contents was prepared and the properties analyzed in terms of solubility, intrinsic viscosity, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results demonstrated that when the aldehyede content of DASS was increased from 20% to 95%, the solubility, molecular weight, crystallizability, and thermal stability decreased. Thermoplastic DASS (TPDASS) was prepared by adding glycerol as a plasticizer; the thermal, rheological, hydrophobic, and tensile properties of TPDASS were investigated. The results indicated that, for the same glycerol content, with the increase of aldehyde content, the moisture adsorption decreased, while the shear viscosity, glass transition temperature, and tensile properties of TPDASS increased significantly. The effects were attributed to the introduction of aldehyde groups reducing the hydrogen bonds and decreasing the hydrophility of the starch. Moreover, the aldehyde and hydroxyl groups of DASS favored a semi-acetal formation with higher aldehyde content and cross-linking of DASS occurred with the increase of aldehyde content. In summary, compared to starch, the thermoplastic properties and hydrophobicity of DASS was improved. In the presence of water (10 wt%), the tensile strength of TPDASS with 95% aldehyde content (TPDASS95) moderately decreased, from 16.7 MPa to 14.0 MPa, when the glycerol content increased from 10% to 30%. The TPDASS with improved properties will find their applications in preparing biodegradable plastics.

Development of Biodegradable Thermosetting Plastic Using Dialdehyde Pineapple Stem Starch

“…This suggests that the thermosetting plastic generated could form an inter-and intramolecular acetal and hemiacetal crosslinking network during the hot compression molding process for sheet production [25,26]. Furthermore, as previously reported, aldehyde materials can establish network linkages with hydroxyl functional groups [68][69][70]. Thus, while glycerol acts as a plasticizer, it may also engage in acetal linkage formation with dialdehyde starch.…”

“…The proposed linkage structure of thermosetting plastic derived from dialdehyde pineapple starch is visualized in Figure 9. Notably, the highest strength values achieved by the thermosetting plastic, prepared using dialdehyde pineapple starch in this study, surpass those of other aldehyde starch-based plastics, which typically fall within the range of 2 MPa to 30 MPa [53,69]. The densities of the starch-based plastics were also monitored, as depicted in Figure 10b.…”

“…Conversely, thermosetting plastic starch or D30PSS-based plastics exhibited a marked increase in stress and a substantial decrease in extensibility as higher glycerol content was introduced. Figure 7b-d groups [68][69][70]. Thus, while glycerol acts as a plasticizer, it may also engage in acetal linkage formation with dialdehyde starch.…”

Preparation and Characterization of Superabsorbent Polymers Based on Starch Aldehydes and Carboxymethyl Cellulose

“…In previous studies, based on the high functionality and reactivity of aldehyde groups, there have been attempts to use environment-friendly and non-toxic dialdehyde carbohydrates as crosslinking agents to replace glutaraldehyde. The linkages between aldehyde and hydroxyl groups are used to prepare films [25,26] while the linkages between aldehyde and amine groups are used to prepare films or gels and fix biological tissues [27,28,29]. Citric acid, which is environment-friendly, non-toxic, and biodegradable, is used as an excellent crosslinking agent in the food and drug industry [30,31].…”

A Long-Chain Alkylation of Dialdehyde Starch to Improve Its Thermal Stability and Hydrophobicity

“…It has been reported that dialdehyde yam starch has poor stability as compared to native starch when the content of the aldehyde groups is increased [12]. A recent study has also suggested that thermal stability of dialdehyde sweet potato starch will decrease when the aldehyde content was increased from 20% to 95% [13]. Therefore, knowing how to further improve the thermal stability of DAS is deserving of research.…”