Effects of sorbitol and formamide plasticizers on molecular motion in corn starch studied using NMR and DMTA

Abstract

Mechanical and thermal properties of composite polymer materials strongly depend on their local structure and molecular dynamics which can be effectively studied by the solid-state nuclear magnetic resonance (NMR) techniques. In the present paper, the influence of formamide (F) and sorbitol (S) plasticizers on molecular motion in thermoplastic starch (TPS) was studied using solid-state NMR spectroscopy and dynamic mechanical thermal analysis (DMTA). DMTA measurements carried out for formamide-(F-TPS) and sorbitol-plasticized (S-TPS) corn starches indicated heterogeneous plasticizer distribution of plasticizer-rich and starch-rich phases within the samples. The single pulse and cross-polarization 13 C NMR spectra measured for both plasticized starches confirmed the amorphous character of their structure and distinctly different chain mobility supported by the values of 13 C spin-lattice relaxation times. The results of the analysis of broad line and magic angle spinning 1 H NMR spectra are in accordance with the results of DMTA measurements, revealing lower mobility of starch chains within S-TPS in comparison to F-TPS. Crosslinking of the starch chains with sorbitol molecules was suggested as being responsible for the lower mobility of the starch chains in S-TPS.

Study of the Complex Permittivity of a Polyurethane Matrix Modified by Nanoparticles

“…They have various applications in industry due to their high adhesive strength and their excellent dielectric and mechanical properties. Due to their excellent dielectric properties, they are widely used as electrical insulation materials, and due to their adhesive properties, they are used as a binder for composites [11], [12], [13], [14], [15]. Today, polymer-based nanodielectric systems are more frequently investigated for their electrical properties because the introduction of nanofillers has indicated several advantages when compared with the similar properties obtained with pure epoxy systems without any particles or with epoxy systems with micrometre-sized fillers.…”

Effect of Plasticizers on Properties, Retrogradation, and Processing of Extrusion‐Obtained Thermoplastic Starch: A Review

“…The strength of these links effectively restricts the movement of the starch chains (a diagram of this interaction is shown in Figure 1), evidenced in the Fourier transform infrared spectroscopy (FTIR) spectra, [51] a behavior that has been corroborated by other authors through dynamic mechanical analysis (DMA) and nuclear magnetic resonance (NMR). [52] Isosorbide is another polyol that has shown good results in the thermoplasticization of starch by avoiding the retrogradation process and requiring a lower temperature for its transformation, [53][54][55] but its plasticization mechanism has not been studied in depth.…”

Synergistic toughening of polypropylene by thermoplastic starch acetate andSEBS‐MAH

“…However, the poor processability, weak mechanical properties, and severe hydrophilicity limit the wide application of starch. Therefore, the plasticization of starch is crucial in order to present melting behavior by adding common plasticizer molecules such as glycerol, 2–6 water, 7,8 urea, 9–11 citric acid, 12–14 formamide, 15–17 , etc.…”