This article reports the fabrication of poly (3‐hydroxybutyrate) (PHB)/cellulose nanocrystal (CNC) based nanobiocomposite films with improved gas barrier and migration properties for food packaging applications. Acid hydrolysis of cellulose pulp from bamboo (Bambusabalcooa) yields CNCs with diameter of 15–20 nm and length of 400–600 nm. Evaluation of d‐spacing using XRD indicates intercalation of PHB matrix with CNC at optimum loadings of 2 wt%. Overall migration values in presence of both polar and nonpolar food simulants are found within standard limits. After migration studies on PHB/CNC films, significant decrease in crystallization temperature (by 15°C) is observed, with subsequent presence of multiple melting peaks. The oxygen transmission rate (OTR) decreases significantly (by ∼65%), even at low CNC (∼2 wt%) loadings. Permeation activation energy (calculated from Arrhenius equation) and barrier properties, such as solubility and diffusivity, improved (decreased by ∼57 and 17%, respectively) with loading fractions (∼2 wt%) due to the hydrogen bonded interaction of PHB with CNCs as well as tortuous path provided towards oxygen permeation. POLYM. ENG. SCI., 55:2388–2395, 2015. © 2015 Society of Plastics Engineers

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The work focused on the formation of percolation network by cellulose nanocrystals (CNCs) in poly(3-hydroxybutyrate) (PHB) matrix, which affects the rheological and mechanical properties of the polymer. Rheological investigations revealed the formation of a percolation network in the fabricated PHB/CNC films with a percolation threshold at a CNC loading of approximately 2 wt%. This observation was further confirmed by both mechanical analysis and modeling studies using Halpin-Kardos and Ouali models. The tensile modulus of the PHB/CNC films was found to be significantly higher (by 58%) than pristine PHB, leading to toughened and more flexible films. Fractured morphology showed the formation of bridge between the CNC and PHB matrix. The rheological parameters (linear and non-linear) were studied in detail to understand the viscoelastic properties of PHB/CNC nanocomposites. Rheological analysis was conducted over a wide range of temperature, and was coupled with differential scanning calorimetry measurements to examine the effect of temperature on the elastic modulus of the nanobiocomposites, especially near the crystallization temperature. The present study is expected to provide a better understanding of the effect of CNC dispersion on the structure-property relation of PHB/ CNC nanocomposites. POLYM. COMPOS., 00:000-000, 2015.

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