Biodegradable nanocomposites of poly (butylene adipate-co-terephthalate) (PBAT) with organically modified nanoclays

Biodegradation of PHB/PBAT films and isolation of novel PBAT biodegraders from soil microbiomes

Polyhydroxyalkanoates (PHAs) are important candidates for replacing petroleum-based plastics. This transition is urgent for the development of a biobased economy and to protect human health and natural ecosystems. PHAs are biobased and biodegradable polyesters that when blended with other polymers, such as poly(butylene adipate-co-terephthalate) (PBAT), acquire remarkable improvements in their properties, which allow them to comply with the requirements of packaging applications. However, the biodegradation of such blends should be tested to evaluate the impact of those polymers in the environment. For instance, PBAT is a compostable aliphatic-aromatic copolyester, and its biodegradation in natural environments, such as soil, is poorly studied. In this work, we evaluated the biodegradation of a bilayer film composed of PHB and PBAT, by a soil microbiome. The bilayer film reached 47 ± 1 % mineralization in 180 days and PHB was no longer detected after this period. The increased crystallinity of the PBAT residue was a clear sign of biodegradation, indicating that the amorphous regions were preferentially biodegraded. Seven microorganisms were isolated, from which 4 were closely related to microorganisms already known as PHB degraders, but the other 3 species, closely related to Streptomyces coelicoflavus, Clonostachys rosea and Aspergillus insuetus, were found for the first time as PHB degraders. Most remarkably, two fungi closely related to Purpureocillium lilacinum and Aspergillus pseudodeflectus (99.83 % and 100 % identity by ITS sequencing) were isolated and identified as PBAT degraders. This is very interesting due to the rarity of isolating PBAT-degrading microorganisms. These results show that the bilayer film can be biodegraded in soil, at mesophilic temperatures, showing its potential to replace synthetic plastics in food packaging.

Exploring the potential of lignin nanoparticles in enhancing the mechanical, thermal, and bioactive properties of poly (butylene adipate-co-terephthalate)

The preparation and characterization of lignin nanoparticles (LNPs) were described. LNPs were produced via the precipitation technique. Nanocomposites of LNPs with poly (butylene adipate-co-terephthalate) (PBAT) were prepared by melt mixing with various concentrations up to 6 wt% of LNPs. The assessment of the effects of LNP addition on the mechanical, thermal, morphological, cytotoxicity, antioxidant, antibacterial, and antiviral properties of nanocomposites was carefully performed. The addition of LNPs to PBAT enhances the thermal stability of the nanocomposites. The antioxidant effect of LNPs on PBAT increased with increasing filler content. LNPs showed higher efficiency as antioxidant agents than lignin particles (LP). The tensile modulus increased by 20 % for the nanocomposites with 6 % LNPs in comparison with neat PBAT. The crystallization peak temperature of PBAT was 80 °C, which increased to 104.6 °C with the addition of 6 wt% of LNPs, suggesting their strong nucleation activity. Antibacterial tests demonstrated the bacteriostatic activities of LNP, LP, and nanocomposites. Both LP and LNP showed considerable antiviral activity against herpes simplex virus type 1 and human coronavirus 229e. The antiviral activity of LNP was concentration-dependent. The findings suggest that LNP is a promising bio-additive for PBAT and can enhance its properties for various applications, including food packaging.

Degradation characteristics of polybutylene adipate terephthalic acid (PBAT) and its effect on soil physicochemical properties: A comparative study with several polyethylene (PE) mulch films

The degradation process of different types of mulch in agriculture and its effect on soil ecosystem should be considered comprehensively. To this end, the changes in performance, structure, morphology, and composition of PBAT film during the degradation process were examined through a multiscale approach in comparison with several PE films and their effects on the soil physicochemical properties were investigated. At the macroscopic scale, the load and elongation of all films decreased with increasing ages and depths. At the microscopic scale, the stretching vibration peak intensity (SVPI) for PBAT and PE films decreased by 48.8 ∼ 60.2% and 9.3 ∼ 38.6%, respectively. The crystallinity index (CI) increased by 67.3 ∼ 209.6% and 15.6 ∼ 21.8%, respectively. At the molecules scale, terephthalic acid (TPA) was detected in localized soil with PBAT mulch after 180 d. In short, the degradation characteristics of PE films were depended on their thickness and density. The PBAT film exhibited the highest degree of degradation. Simultaneously, the soil physicochemical properties such as soil aggregates, microbial biomass and pH were affected by the changes of film structure and components during the degradation process. This work has practical implications for the sustainable development of agriculture.

Biocomposite PBAT/lignin blown films with enhanced photo-stability

Lignin can be obtained as a byproduct during cellulose-rich pulp fibers production and it is habitually treated as waste or intended for low-value destinations. However, due to UV absorption and mechanical properties, lignin can contribute to the fabrication of biodegradable blown films with superior performances. In this study, it was established the suitability of lignin for manufacturing biocomposite PBAT blown films with higher stiffness and photo-oxidation resistance. The effect of the filler concentration on the melt rheological behavior in non-isothermal elongational flow was investigated. The results allowed us to choose the correct filler concentration for producing films through a film blowing operation. The PBAT/lignin blown film composites displayed an increase of the elastic modulus if compared to neat PBAT films without affecting their elongation at break. Furthermore, the filler delayed the photo-oxidative degradation of PBAT hence potentially allowing open-air applications.

Use of Biochar as Filler for Biocomposite Blown Films: Structure-Processing-Properties Relationships

In this work, biocomposite blown films based on poly(butylene adipate-co-terephthalate) (PBAT) as biopolymeric matrix and biochar (BC) as filler were successfully fabricated. The materials were subjected to a film-blowing process after being compounded in a twin-screw extruder. The preliminary investigations conducted on melt-mixed PBAT/BC composites allowed PBAT/BC 5% and PBAT/BC 10% to be identified as the most appropriate formulations to be processed via film blowing. The blown films exhibited mechanical performances adequate for possible application as film for packaging, agricultural, and compost bags. The addition of BC led to an improvement of the elastic modulus, still maintaining high values of deformation. Water contact angle measurements revealed an increase in the hydrophobic behavior of the biocomposite films compared to PBAT. Additionally, accelerated degradative tests monitored by tensile tests and spectroscopic analysis revealed that the filler induced a photo-oxidative resistance on PBAT by delaying the degradation phenomena.

Scale-up of non-toxic poly(butylene adipate-co-terephthalate)-Chitin based nanocomposite articles by injection moulding and 3D printing

Poly(butylene adipate-co-terephthalate) (PBAT), a compostable polymer, filled with different weight percentage of unbleached nano chitin (NC; 10%, 30% and 50%), a biodegradable filler from crustacean waste, were prepared from the extruded blends by injection moulding and 3D printing. The nanochitin required was prepared from chitin isolated from prawn shells (Fenneropenaeus indicus). The nanochitin crystals were observed to contain carboxylic acid surface functional groups as assessed by FT-IR, ¹³C solid state NMR (SS NMR) spectroscopy, zeta potential measurements and the extent of the same was estimated by potentiometric titration. The PBAT-NC nanocomposites were characterized SS NMR spectroscopy, FT-IR spectroscopy, wide angle X-ray diffraction, dynamic mechanical analysis, DSC and TGA. Thermal and mechanical properties of the nanocomposites were determined. The moulded nanocomposites changed more and more rigid with increasing weight percentage of NC without significant change in the tensile strength. The TGA indicated that the thermal stability of PBAT could be improved but not significantly by the addition of NC. Wound healing was enhanced in the presence of the nanocomposite while in vivo toxicity was significant at high concentration. The PBAT-NC nanocomposites could be moulded in to useful articles such as laptop charger cover, rat cover for washing machine, planters and key holders under conditions similar to that used in the processing of LDPE.

Synthesis, Characterization and Properties of Biodegradable Poly(Butylene Sebacate-Co-terephthalate)

In this study, poly(butylene sebacate-co-terephthalate) (PBSeT) was successfully synthesized using various ratios of sebacic acid (Se) and dimethyl terephthalate (DMT). The synthesized PBSeT showed a high molecular weight (M_w, 88,700–154,900 g/mol) and good elastomeric properties. In particular, the PBSeT64 (6:4 sebacic acid/dimethyl terephthalate mole ratio) sample showed an elongation at break value of over 1600%. However, further increasing the DMT content decreased the elongation properties but increased the tensile strength due to the inherent strength of the aromatic unit. The melting point and crystallization temperature were difficult to observe in PBSeT64, indicating that an amorphous copolyester was formed at this mole ratio. Interestingly, wide angle X-ray diffraction (WAXD) curves was shown in the cases of PBSeT46 and PBSeT64, neither the crystal peaks of PBSe nor those of poly(butylene terephthalate) (PBT) are observed, that is, PBSeT64 showed an amorphous form with low crystallinity. The Fourier-transform infrared (FT-IR) spectrum showed C–H peaks at around 2900 cm⁻¹ that reduced as the DMT ratio was increased. Nuclear magnetic resonance (NMR) showed well-resolved peaks split by coupling with the sebacate and DMT moieties. These results highlight that elastomeric PBSeT with high molecular weight could be synthesized by applying DMT monomer and showed promising mechanical properties.

The effects of blend ratio and storage time on thermoplastic starch/poly(butylene adipate-co-terephthalate) films

The objective of this work was to investigate blend ratio and storage time effects on the morphological, mechanical, and thermal properties of thermoplastic starch/poly(butylene adipate-co-terephthalate) (TPS/PBAT) films. TPS was prepared from plasticized cassava starch using a twin-screw extruder. TPS was subsequently melt-blended with PBAT with varied weight ratios (i.e., 20/80, 40/60 and 60/40) and blown to form TPS/PBAT films. It was found that increasing the TPS/PBAT ratio to 40/60 led to improved distributions of polymeric components and increased PBAT crystallization temperatures while reducing TPS melting transitions and tensile properties of TPS/PBAT films. After three months of storage at 30 °C, the tensile strength and secant modulus at 2% strain of TPS/PBAT films increased due to recrystallization of both TPS and PBAT. Blend ratios were the primary determinant for changes in TPS/PBAT film elongation at break with this storage time. Elongation at break decreased at low TPS:PBAT ratios (i.e., 20/80) and increased at high blend ratios (i.e., 60/40). The recrystallization of both TPS and PBAT components were observed from XRD and DSC analyses. Results obtained from both techniques confirmed the formation of additional crystalline structures of individual components during storage. The recrystallization phenomena also affected thermal transition temperatures of blend components. The crystallization temperature of PBAT-rich phase increased as starch could act as nucleating sites for PBAT. Using DMA, the tan δ curve of TPS/PBAT film exhibited two sharp individual peaks corresponding to the glass transitions of PBAT-rich and starch-rich phases. The tan δ of TPS-rich phase shifted to higher temperature due to recrystallization of TPS-rich phase.

Scale-Up Fabrication of Biodegradable Poly(butylene adipate-co-terephthalate)/Organophilic-Clay Nanocomposite Films for Potential Packaging Applications

The development of biodegradable packing materials is a global priority due to the huge volumes of plastic refuse entering landfills and the environment. In this study, a series of biodegradable nanocomposite films based on poly(butylene adipate-co-terephthalate) (PBAT) and reinforced with an organophilic layered double hydroxide (OLDH) were scale-up fabricated. The OLDH nanosheets with a basal spacing of 4.07 nm were presynthesized on a large-scale by solvent-free high-energy ball milling. All of the PBAT/OLDH nanocomposite films (0.5-4 wt % OLDH) showed a uniform dispersion of OLDH nanosheets in the PBAT matrix. A PBAT/OLDH film containing 1 wt % OLDH (denoted herein as OLDH-1) demonstrated outstanding thermal, optical, mechanical, and water vapor barrier properties compared with a pure PBAT film (OLDH-0), including a 37% reduction in haze and a 41.9% increase in nominal tensile strain at break dramatically. Furthermore, the food packaging measurement revealed that the OLDH-1 film showed a better packaging effect than the pure PBAT film and commercial polyethylene packing materials. The feasibility of scale-up manufacture and the excellent processability, manufacturing scalability, mechanical performance, optical transparency, water vapor barrier properties, and food packaging performance of the PBAT/OLDH nanocomposite films encourage their future application as biodegradable packaging films.

Antimicrobial and sustainable food packaging based on poly(butylene adipate-co-terephthalate) and electrospun chitosan nanofibers

PBAT/CS-NF bionanocomposites show an optimal combination of flexibility, strength, barrier, migration, and antibacterial properties, therefore are suitable for food packaging applications.