Fabrication and Characterization of Poly(hydroxybutyrate)- and Poly(caprolactone)-Based Active Biodegradable Films Incorporating Allyl Isothiocyanate

In this study, in order to overcome the fragility and cost disadvantages of PHB-based films, PHB was blended with PCL. Additionally, allyl isothiocyanate (AITC) was incorporated as an active component. The resulting PHB, PCL, and PHB/PCL composite films with/without allyl isothiocyanate (AITC) prepared via the casting method were analyzed for their physicochemical, thermal, mechanical, barrier, morphological properties and antimicrobial and antioxidant activities. While neat PHB films showed the highest tensile strength (TS) of 19.82 MPa and the lowest elongation at break (EB) of 1.13%, PHB/PCL blend films exhibited lower TS (15.34 MPa) and higher EB values (21.33%). AITC addition decreased TS significantly while showing no significant impact on EB. PHB/PCL blend films had the highest water vapor permeability (WVP) values, possibly due to their increased porosity, while neat PCL- and PHB-based films showed better oxygen and water vapor barrier properties, respectively. DSC analysis showed that PHB and PCL films had a crystalline phase, while in the case of PHB/PCL blend films, both polymers maintained their characteristic melting behaviors. The addition of AITC affected the thermal stability by increasing the melting temperature of the PHB films and decreasing the melting temperature of the PCL films. SEM analyses revealed that PHB and PHB-A films had a homogeneous structure, while irregular spherical structures and cracks were also observed in PCL and PCL-A films. The incorporation of AITC into the film samples (PHB-A, PCL-A, and PHB/PCL-A) brought remarkable antimicrobial (from 16.25 mm to 37.25 mm of inhibition zones) and antioxidant activity (from 281.85 to 286.41 mg trolox equivalent/1 g film sample, as measured by CUPRAC), while no activity was observed in the control films without AITC (PHB, PCL, and PHB/PCL). In conclusion, new AITC-activated PHB-, PCL-, and PHB/PCL-based films were successfully designated with additional functionalities and showed valuable potential to be used in active biodegradable food packaging applications.