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Chen J.,Yangzhou University | Chen J.,Provincial Key Laboratories of Environmental Engineering and Material | Xu C.,Yangzhou University | Wu D.,Yangzhou University | And 6 more authors.
Carbohydrate Polymers | Year: 2015

Cellulose crystals, including microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC), were used as the fillers to prepare green composites with poly(β-hydroxybutyrate) (PHB) by melt mixing for crystallization study. The results reveal that the spherulite morphology of PHB and its composites depends highly on the crystallization temperature, evolving from bundle shaped to ring-banded and finally to irregular or zigzag textures with increase of temperature. However, the ring-banded structure is strongly affected by the presence of cellulose crystals, and the average band space decreases evidently with the addition of MCC or NCC. Compared with PHB/MCC composite, PHB/NCC composite shows degraded spherulite structure with smaller band space and higher flocculation level of peak-to-valley height because of stronger unbalanced stresses in this system. Besides, cellulose crystals can act as good heterogeneous nucleating agent to accelerate the crystallization of PHB, which is further confirmed by the polarized optical microscopy observations and the kinetic analyses. © 2015 Elsevier Ltd. All rights reserved.


Chen J.,Yangzhou University | Chen J.,Provincial Key Laboratories of Environmental Engineering and Material | Wu D.,Yangzhou University | Wu D.,Provincial Key Laboratories of Environmental Engineering and Material | Pan K.,Yangzhou University
International Journal of Biological Macromolecules | Year: 2016

Ethyl cellulose (EC) was blended with poly(β-hydroxybutyrate) (PHB), aiming at controlling crystallization and mechanical properties of PHB. The obtained PHB/EC blend is an immiscible system, and the discrete EC phase behaves dual characteristics in the PHB matrix, as the viscoelastic droplets during processing, and as the rigid filler particles during shear flow. This is confirmed by the rheological tests. The presence of EC domains acts as the tackifier, sharply increasing system viscosity from 1000 Pa s to 5000 Pa s, and as a result, has large influence on the spherulite morphology of PHB and its crystallization kinetics. The PHB spherulite growth rate reduces in the presence of inert EC, accompanied by decreased degree of crystallinity and reduced lamella defects. These affect the mechanical properties of PHB strongly, together with reinforcing effect of EC itself. At the lower content level, EC can act as both reinforcement and toughener. The presence of 1 wt% EC enhances the tensile strength of PHB by about 22%, from 27.5 MPa to 33.3 MPa, accompanied by 15% increase of impact strength. This work provide an easy way to control the structure and properties of PHB using EC. © 2016 Elsevier B.V.

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