Biodegradable poly(3‐hydroxybutyrate) (PHB)/functionalized multi‐walled carbon nanotubes (f‐MWNTs) nanocomposite was prepared in this work by solution casting method at 2 wt% f‐MWNTs loading. Scanning electron microscopy and transmission electron microscopy observations indicate a homogeneous distribution of f‐MWNTs in the PHB matrix. Nonisothermal melt crystallization, overall isothermal melt crystallization kinetics, and crystalline morphology of neat PHB and the PHB/f‐MWNTs nanocomposite were studied in detail. It is found that the presence of f‐MWNTs enhances the crystallization of PHB during nonisothermal and isothermal melt crystallization processes in the nanocomposite due to the heterogeneous nucleation effect of f‐MWNTs. Moreover, the incorporation of a small quantity of f‐MWNTs apparently improves the thermal stability of the PHB/f‐MWNTs nanocomposite with respect to neat PHB. Two methods are employed to study the activation energies of thermal degradation for both the neat PHB and the PHB/f‐MWNTs nanocomposite. The activation energy of thermal degradation of the PHB/f‐MWNTs nanocomposite is higher than that of neat PHB. Copyright © 2009 John Wiley & Sons, Ltd.

In this work, nonisothermal melt crystallization and subsequent melting behavior of poly(hydroxybutyrate) (PHB) and its nanocomposites at different multiwalled carbon nanotubes (MWCNTs) loadings were investigated. Increasing the MWCNTs loadings has enhanced the nonisothermal melt crystallization of PHB significantly in the nanocomposites when compared with that of the neat PHB; furthermore, increasing the cooling rates shift the crystallization exotherms to low temperature range for both neat PHB and its nanocomposites. Double melting behavior is found for both neat PHB and its nanocomposites crystallized nonisothermally from the melt, which is explained by the melting, recrystallization, and remelting model. Effects of the MWCNTs loadings, cooling rates, and heating rates on the subsequent melting behavior of PHB were studied in detail. It is found that increasing the MWCNTs loadings, decreasing the cooling rates, and increasing the heating rates would restrict the occurrence of the recrystallization of PHB in the nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2238–2246, 2009

Biodegradable poly(epsilon-caprolactone) (PCL)/multi-walled carbon nanotubes containing carboxylic groups (f-MWNTs) nanocomposites were prepared via simple melt compounding at low f-MWNTs loading in this work. Scanning and transmission electron microscopy observations indicate a homogeneous and fine distribution of f-MWNTs throughout the PCL matrix. The effect of low f-MWNTs loading on the crystallization, mechanical properties, and controlled enzymatic degradation of PCL in the nanocomposites were studied in detail with various techniques. The experimental results indicate that the incorporation of f-MWNTs enhances both the nonisothermal crystallization peak temperature and the overall isothermal crystallization rate of PCL in the PCL/f-MWNTs nanocomposites relative to neat PCL; moreover, the incorporation of a small quantity of f-MWNTs has improved apparently the mechanical properties of the PCL/MWNTs nanocomposites compared to neat PCL. The enzymatic degradation of neat PCL and the PCL/f-MWNTs nanocomposites at low f-MWNTs loading was studied in detail. The variation of weight loss with enzymatic degradation time, the surface morphology change, the reduced film thickness, the appearance of f-MWNTs on the surface of the films, and the almost unchanged molecular weight after enzymatic degradation suggest that the enzymatic degradation of neat PCL and the PCL/f-MWNTs nanocomposites may proceed via surface erosion mechanism. The presence of f-MWNTs reduces the enzymatic degradation rate of the PCL matrix in the nanocomposites compared with that of the pure PCL film.

Poly(3-hydroxybutyrate) (PHB) is a truly biodegradable and highly biocompatible polymer; [1][2][3][4][5][6] however, wider application range of PHB has been limited because of its stiffness and brittleness problems. Moreover, its melting temperature is so close to the thermal decomposition temperature that PHB becomes thermally unstable during processing. Therefore, many attempts have been made to improve its mechanical and thermal properties, among which polymer blending is an easy and convenient way of achieving desirable combination of properties. Ha et al. and Di Lorenzo et al. have recently reviewed miscibility, properties and biodegradability of polymer blends containing PHB. 7,8Addition of nano-particles such as carbon nanotubes (CNTs) to form nanocomposites has provided another means to improve materials performances.9,10 CNTs possess unique mechanical, electrical and thermal properties that make it ideal candidates to substitute conventional nano-fillers in the fabrication of polymer nanocomposites. [11][12][13][14][15][16] It is noted that the strong interfacial adhesion between polymer chains and nanotubes is critically important to effectively maximize load transfer from the matrix to CNTs. Recently, PHB/single walled carbon nanotubes (SWCNTs) nanocomposites have been prepared by solution casting method using chloroform as cosolvent. 17 The experimental results showed that the crystalline size substantially decreased for the PHB/SWCNTs nanocomposite with a 1% weight fraction of SWCNTs as compared to that of neat PHB; moreover, the polymer nanocomposite films showed an increase in hardness and Young's modulus with increasing SWCNTs contents. 17To the best of our knowledge, biodegradable PHB/multiwalled carbon nanotubes (MWNTs) nanocomposites have not been reported so far in the literature. We have recently prepared PHB/MWNTs nanocomposites at different MWNTs loadings by solution casting method and studied the effects of the presence of MWNTs and their loadings on the subsequent multiple melting behavior of PHB in the nanocomposites crystallized non-isothermally from the melt. 18 In this note, we further studied the isothermal melt crystallization kinetics of neat PHB and the PHB/MWNTs nanocomposites for a better understanding of the influence of the presence of MWNTs and the loadings on the crystallization behavior of PHB in the PHB/MWNTs nanocomposites.

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