Preparation of bioactive film for regulating chlorine dioxide release based on the hygroscopic properties of chitosan and its application in broccoli preservation

An active packaging film was developed by integrating sodium chlorite (SC) and citric acid (CA) into a Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) (PLA/PBAT) matrix, enabling the controlled release of chlorine dioxide (ClO2) gas. The release of ClO2 was further regulated by introducing chitosan (CS) into the film, leveraging its hygroscopic properties. The results showed that when the addition amount of CS was 4 wt%, the water vapor transmission rate increased by 41.41 %, the water contact angle decreased by 24.4 %, the ClO2 release increased by 2.81 times after 72 h, and the scavenging rate of DPPH free radicals reached 96.26 % after 96 h. When the film was applied to broccoli packaging, it successfully protected the appearance and color of broccoli, effectively inhibited the activity of oxidase and reduced the reduction of active substances, and maintained the marketable quality for up to 8 days. Therefore, this ClO2-releasing active film has application potential in the color protection and preservation of broccoli and other green vegetables.

Green composites for sustainable food packaging: Exploring the influence of lignin-TiO2 nanoparticles on poly(butylene adipate-co-terephthalate)

Titanium dioxide (TiO2) is a common pigment used in food packaging to provide a transparent appearance to plastic packaging materials. In the present study, poly(butylene adipate-co-terephthalate) (PBAT) incorporated with lignin-TiO2 nanoparticles (L-TiO2) eco-friendly composite films was prepared by employing an inexpensive melting and hot-pressing technique. The P-L-TiO2 composite films have been studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC) analysis. The FTIR results and homogeneous, dense SEM images confirm the interaction of L-TiO2 with the PBAT matrix. It has also been found that the addition of L-TiO2 nanoparticles can increase the crystallinity, tensile strength, and thermal stability of PBAT. The addition of L-TiO2 increased the tensile strength and decreased the elongation at break of films. The maximum tensile strength of the film, achieved with 5 wt% L-TiO2, was 47.0 MPa, compared with 24.3 MPa for pure PBAT film. The composite film with 5 wt% L-TiO2 has outstanding oxygen and water vapor barrier properties. As the content of lignin-TiO2 increases, the antimicrobial activity of the composite films also increases; the percentage of growth of all the tested bacteria Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) is significantly reduced. Strawberries were packed to evaluate the suitability of produced composite films as packaging materials, as they effectively preserved pigments from accumulation and extended the shelf-life as compared to commercial polyethylene packaging film.

Toughening and thermal characteristics of plasticized polylactide and poly(butylene adipate-co-terephthalate) blend films: Influence of compatibilization

Bio-based polylactide (PLA) derived from fermented corn starch was blended with poly(butylene adipate-co-terephthalate) (PBAT) and triethyl citrate (TEC) plasticizer using a twin screw extruder. PLA-grafted-maleic anhydride (PLA-g-MA) synthesized via reactive maleation and toluene diisocyanate (TDI) were used as compatibilizers for these blends. Improvements in the toughness, phase morphology and thermal behavior of the PLA/PBAT/TEC (PBT) blend films were evaluated in terms of compatibilization effect. The compatibilized PBT blends showed noticeably superior tensile strength, elongation, and tensile-impact toughness compared with uncompatibilized ones due to the greater compatibility of PLA and PBAT phases. Well dispersed PBAT particles and many elongated fibrils were observed on the fracture surface of the film after compatibilization. Both TDI and PLA-g-MA were effective compatibilizers for the blend at an appropriate level. The addition of PLA-g-MA to the plasticized blends not only significantly enhanced mechanical properties and phase adhesion, but also accelerated cold crystallization and formed crystal perfection, a result of improvements in chain mobility and packing efficiency. Differential scanning calorimetry (DSC) results revealed changes in T_g and melting behavior of the blends from influences of compatibilization. The different types and levels of compatibilizer affected the thermal stability of the PLA phase but did not affect char remaining.

Enhancement of the Mechanical Properties of Polyimide Film by Microwave Irradiation

Polyimide films have conventionally been prepared by thermal imidization of poly(amic acid)s (PAAs). Here we report that the improvement of tensile strength while increasing (or maintaining) film flexibility of polyimide films was accomplished by simple microwave (MW) irradiation of the PAAs. This improvement in mechanical properties can be attributed to the increase in molecular weight of the polyimides by MW irradiation. Our results show that the mechanical properties of polyimide films can be improved by MW irradiation, which is a green approach that requires relatively low MW power, very short irradiation time, and no incorporation of any additional inorganic substance.