The interaction in sorbitol-plasticized starch bionanocomposites via positron annihilation lifetime spectroscopy and small angle X-ray scattering
- Authors: Liu, Huihua , Chaudhary, Deeptangshu , Roberts, Jason , Weed, Ryan , Sullivan, James , Buckman, Stephen
- Date: 2012
- Type: Text , Journal article
- Relation: Carbohydrate Polymers Vol. 88, no. 4 (2012), p. 1172-1176
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- Description: We investigated the free volume variations (size and distribution) within sorbitol plasticized high amylose bionanocomposites of different formula where the interactions among sorbitol, amylose and hydrophilic montmorillonite nanoclay (MMT) modified the crystallinity and therefore, the free volume of the matrix. Positron Annihilation Lifetime Spectroscopy (PALS) is a useful technique to monitor the changes of free volume within the polymer matrix - due to polymer-plasticizer or polymer-polymer interactions. In a recent investigation (Liu et al.; Carbohydrate Polymer, 2011, 85(1), 97-104), we demonstrated that there exists a threshold plasticizer concentration - above which the matrix crystallinity and moisture content can be significantly altered. By investigating the relationship between the changes of free volume and the development of crystalline morphology, we presented evidence that, at the molecular level, the free volume changes due to amylose-MMT interactions were affected by the concentration of the sorbitol plasticizer. The free volume analysis revealed that when the concentration of sorbitol was low (5 wt%), the bionanocomposite showed a bimodal distribution for free volume pore-size. As the sorbitol concentration increased, these free volume pores coalesced. Further, due to sorbitol's hydrophilic nature, this study also presented the evidence of moisture 'lock-in' within the bionanocomposites matrix; only one pore size - was confirmed in the high moisture content samples; meaning that sorbitol was able to have binary interactions with the amylose and with the water molecules so that the free volume pore-size was relatively more uniform. © 2012 Elsevier Ltd. All rights reserved.
Characterization of starch films containing starch nanoparticles Part 1: Physical and mechanical properties
- Authors: Shi, Aimin , Wang, Li-Jun , Li, Dong , Adhikari, Benu
- Date: 2013
- Type: Text , Journal article
- Relation: Carbohydrate Polymers Vol. 96, no. 2 (2013), p. 593-601
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- Description: We report, for the first time, the preparation method and characteristics of starch films incorporating spray dried and vacuum freeze dried starch nanoparticles. Physical properties of these films such as morphology, crystallinity, water vapor permeability (WVP), opacity, and glass transition temperature (Tg) and mechanical properties (strain versus temperature, strain versus stress, Young's modulus and toughness) were measured. Addition of both starch nanoparticles in starch films increased roughness of surface, lowered degree of crystallinity by 23.5%, WVP by 44% and Tg by 4.3 °C, respectively compared to those of starch-only films. Drying method used in preparation of starch nanoparticles only affected opacity of films. The incorporation of nanoparticles in starch films resulted into denser films due to which the extent of variation of strain with temperature was much lower. The toughness and Young's modulus of films containing both types of starch nanoparticles were lower than those of control films especially at <100 °C. © 2012 Elsevier Ltd. All rights reserved.
- Description: C1
Effect of montmorillonite on morphology, glass transition and crystallinity of the xylitol-plasticized bionanocomposites
- Authors: Liu, Huihua , Chaudhary, Deeptangshu
- Date: 2013
- Type: Text , Journal article
- Relation: Carbohydrate Polymers Vol. 98, no. 1 (2013), p. 391-396
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- Description: High amylose based nanocomposites plasticized by xylitol were prepared via twin-screw extrusion. The synergistic interaction in the xylitol-plasticized nanocomposite was studied via various characterization methods and the unique behavior of the xylitol-plasticized nanocomposite had been discussed. As revealed in the XRD and TEM results, good intercalated/exfoliated morphology had been achieved in all the nanocomposites. Furthermore, the expansion of nanoclay basal spacing was related to the xylitol/nanoclay ratio. DSC analysis clearly proved the unique crystallization process of xylitol-plasticized samples. Moreover, in the crystallization domain results, two domains sized at approximately 93.7. Å and 346. Å were found. This observation points to a two-level complex effect from two aggregate domains; one, the re-aggregation of certain number of silicate layers into domains which trap some of the amylose polymer chains, and two, the bulk drying process which combines smaller amylose crystalline domains within a larger amorphous high amylose matrix. © 2013.
- Description: 2003011127