PBAT Based Composites Reinforced with Microcrystalline Cellulose Obtained from Softwood Almond Shells

Improved Mechanical and Thermal Properties of Date Palm Microfiber-Reinforced PCL Biocomposites for Rigid Packaging

To increase the use of agricultural residues, such as date palm fibers, for the sustainable reinforcement of biocomposites, this study investigated the incorporation of varying weight percentages of date palm microfibers (DPMF) ranging from 0 wt.% to 10 wt.% into polycaprolactone (PCL) matrix. Biocomposites were fabricated using a combination of compression molding and dry blending techniques with and without sodium hydroxide (NaOH) alkali treatment. The surface modification was found to increase the surface roughness of the fibers, removing impurities such as lignin, hemicellulose, and wax, while improving crystallinity, as evidenced by FTIR, XRD, TGA, and particle size analyses. Among the different biocomposites investigated, the results for 5 wt.% DPMF content biocomposites exhibited the highest tensile properties: approximately 20% increase in tensile strength and 164% increase in Young's Modulus in comparison to neat PCL. The crystallinity of the matrix exhibited an increasing trend from approximately 39% for neat PCL to 43% for the 5 wt.% DPMF biocomposites. Furthermore, treated biocomposites demonstrated higher water-repellency behavior and improved thermal properties. Dynamic mechanical analysis (DMA) results indicated enhanced storage moduli for alkali-treated composites; at 35 °C, the storage modulus showed approximately 22% increase compared to the untreated DPMF biocomposites, reflecting improved stiffness and thermomechanical performances. This study highlights the potential of DPMF as an efficient, eco-friendly alternative to fossil-based conventional reinforcement for biocomposite materials' potential for sustainable rigid packaging applications.

Adding Mandarin Peel Waste to a Biodegradable Polymeric Matrix: Reinforcement or Degradation Effect?

In the current context, the use of fillers derived from fruit and vegetable waste is a crucial approach to mitigate waste and promote sustainable resource use, thus contributing to product life cycle completion and the achievement of sustainability goals. This study focuses on incorporating an endemic waste hitherto considered irrelevant within a biodegradable matrix. The resulting biocomposites were carefully characterized mechanically, rheologically, and morphologically to identify the connections between processability, structure, and properties. The results show that the presence of the filler results in an increase in the stiffness of the material (up to 27% in elastic modulus) accompanied by a decrease in tensile strength (approximately 50%) and elongation at break, which is on average about 7% at the highest filler content. This behavior was attributed to poor interfacial adhesion and the influence of a degradation process caused by the presence of citric acid and/or impurities in the filler.

Valorization of Winery By-Products as Bio-Fillers for Biopolymer-Based Composites

Grape seeds (GS), wine lees (WL), and grape pomace (GP) are common winery by-products, used as bio-fillers in this research with two distinct biopolymer matrices-poly(butylene adipate-co-terephthalate) (PBAT) and polybutylene succinate (PBS)-to create fully bio-based composite materials. Each composite included at least 30 v% bio-filler, with a sample reaching 40 v%, as we sought to determine a composition that could be economically and environmentally effective as a substitute for a pure biopolymer matrix. The compounding process employed a twin-screw extruder followed by an injection molding procedure to fabricate the specimens. An acetylation treatment assessed the specimen's efficacy in enhancing matrix-bio-filler affinity, particularly for WL and GS. The fabricated bio-composites underwent an accurate characterization, revealing no alteration in thermal properties after compounding with bio-fillers. Moreover, hygroscopic measurements indicated increased water-affinity in bio-composites compared to neat biopolymer, most significantly with GP, which exhibited a 7-fold increase. Both tensile and dynamic mechanical tests demonstrated that bio-fillers not only preserved, but significantly enhanced, the stiffness of the neat biopolymer across all samples. In this regard, the most promising results were achieved with the PBAT and acetylated GS sample, showing a 162% relative increase in Young's modulus, and the PBS and WL sample, which exhibited the highest absolute values of Young's modulus and storage modulus, even at high temperatures. These findings underscore the scientific importance of exploring the interaction between bio-fillers derived from winery by-products and three different biopolymer matrices, showcasing their potential for sustainable material development, and advancing polymer science and bio-sourced material processing. From a practical standpoint, the study highlighted the tangible benefits of using by-product bio-fillers, including cost savings, waste reduction, and environmental advantages, thus paving the way for greener and more economically viable material production practices.

Mechanical and Rheological Evaluation of Polyester-Based Composites Containing Biochar

The use of biodegradable polymers as matrices in composites gives a wide range of applications, especially in niche areas. The assessment of the effect of the filler content on the change of mechanical properties makes it possible to optimize the composition for specific needs. Biochar was used as a filler in the studied composites with two different biodegradable blends as a matrix. Poly(1,4-butylene adipate-co-1,4-butylene terephthalate)/polylactide/biochar (PBAT/PLA/BC) and polylactide/poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate]/biochar (PLA/P(3HB-co-4HB)/BC) composites with 0, 10, 15, 20 and 30 wt% of biochar underwent mechanical tests. The test results revealed a change in the properties of the composites related to the filler content. The results of the tensile test showed that increasing the biochar content increased the tensile modulus values by up to 100% for composites with 30 wt% of biochar, compared to unfilled matrices, and decreased the elongation associated with the breaking of PBAT/PLA and PLA/P(3HB-co-4HB) matrix composites. The elongation values at break of PBAT/PLA and PLA/(3HB-co-4HB) composites with 30 wt% biochar were reduced by 50% and 65%, respectively, compared to the unfilled matrices. PLA/P(3HB-co-4HB) matrix composites, in contrast to PBAT/PLA/BC, showed a decrease in tensile strength with the increases in filler content from 35.6 MPa for unfilled matrix to 27.1 MPa for PLA/P(3HB-co-4HB)/BC30 composites. An increase in filler content increased the brittleness of the composites regardless of the matrix used, as determined under the Charpy impact-test. This phenomenon was observed for all tested PLA/P(3HB-co-4HB) composites, for which the impact strength decreased from 4.47 kJ/m2 for the matrix to 1.61 kJ/m2 for the composite containing 30 wt% biochar. PBAT/PLA-based composites with 10 wt% of biochar showed slightly lower impact strength compared to the unfilled matrix, but composites with 30 wt% biochar showed 30% lower impact strength than PBAT/PLA. The complex viscosity value increased with increased filler content. For all composites tested on both polyester matrices, the viscosity decreased with increasing angular frequency.

Biobased Films Based on Chitosan and Microcrystalline Cellulose for Sustainable Packaging Applications

The transition to a more sustainable lifestyle requires a move away from petroleum-based sources and the investigation and funding of renewable and waste feedstocks to provide biobased sustainable materials. The formulation of films based on chitosan and microcrystalline cellulose with potential applications in the packaging sector has been demonstrated. Glycerol is also used as a plasticizer in the formulation of flexible films, while mucic acid is used as a valid alternative to acetic acid in such films. The film based on chitosan, microcrystalline cellulose, glycerol, and mucic acid shows properties and a performance similar to those of the film formulated with acetic acid, and, in addition, it seems that the photo-oxidation resistance of the film based on mucic acid is better than that of the material containing acetic acid. The films were characterized using spectroscopy (FTIR and UV-vis), tensile testing, water contact angle measurements, surface observations, and photo-oxidation resistance measurements. The presence of microcrystalline cellulose enhances the mechanical behavior, UV barrier properties, and surface hydrophobicity of the film. The feasibility of formulating chitosan-based films, with or without microcrystalline cellulose, which exhibit good properties and performances is demonstrated. Mucic acid instead of acetic acid is used in the formulation of these film.

Effect of Microcrystalline Cellulose on the Properties of PBAT/Thermoplastic Starch Biodegradable Film with Chain Extender

Poly (butylene adipate-co-terephthalate) (PBAT) is a fully biodegradable polymer with toughness and ductility. It is usually compounded with thermoplastic starch (TPS) to balance the cost for manufacturing biodegradable films such as disposable plastic bags. However, blending with TPS reduces valuable tensile strength, which limits the bearing capacity of PBAT film. In this study, microcrystalline cellulose (MCC) was employed as a reinforcement to strengthen the PBAT/TPS biodegradable film. The effect of MCC content on the mechanical, thermal, and morphological properties of the composite film were investigated. The optimal tensile strength and elongation at break reached 5.08 MPa and 230% when 4% MCC was added. The thermal stability and thermal resistance were improved with the addition of MCC; for example, Tmax increased by 1 °C and Tonset increased by 2-8 °C. Moreover, good compatibility among PBAT, TPS, and MCC can be achieved when the MCC content was below 6%. Consequently, the optimal MCC content was found to be 4%. These results could provide experimental data and method support for preparing high-performance PBAT hybrid films.

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.

The Use of Waste Hazelnut Shells as a Reinforcement in the Development of Green Biocomposites

Biodegradable Mater-Bi (MB) composites reinforced with hazelnut shell (HS) powder were prepared in a co-rotating twin-screw extruder followed by compression molding and injection molding. The effects of reinforcement on the morphology, static and dynamic mechanical properties, and thermal and rheological properties of MB/HS biocomposites were studied. Rheological tests showed that the incorporation of HS significantly increased the viscosity of composites with non-Newtonian behavior at low frequencies. On the other hand, a scanning electron microscope (SEM) examination revealed poor interfacial adhesion between the matrix and the filler. The thermal property results indicated that HS could act as a nucleating agent to promote the crystallization properties of biocomposites. Furthermore, the experimental results indicated that the addition of HS led to a significant improvement in the thermomechanical stability of the composites. This paper demonstrates that the incorporation of a low-cost waste product, such as hazelnut shells, is a practical way to produce low-cost biocomposites with good properties. With a content of HS of 10%, a remarkable improvement in the elastic modulus and impact strength was observed in both compression and injection-molded samples. With a higher content of HS, however, the processability in injection molding was strongly worsened.

Tailoring Interfacial Adhesion between PBAT Matrix and PTFE-Modified Microcrystalline Cellulose Additive for Advanced Composites

Cellulose materials have the potential to serve as sustainable reinforcement in polymer composites, but they suffer from challenges in improving interfacial compatibility with polymers through surface modification. Here, we propose adjusting the interfacial compatibility between microcrystalline cellulose (MCC) and poly (butylene adipate-co-terephthalate) (PBAT) through the strategy based on surface energy regulation. Mechanical ball milling with polytetrafluoroethylene (PTFE) powder was used to simultaneously pulverize, and surface modify MCC to produce MCC sheets with different surface energy. The modified MCC was used to reinforce PBAT composites by simple melt blending. The surface morphology, surface energy of MCC, and the amount of friction transferred PTFE during ball milling were characterized. The mechanical performance, composite morphology, crystallization behavior and dynamic thermomechanical analysis of the composites were investigated. The interfacial adhesion strength of composites closely relates to the surface energy of modified MCC. When the surface energy of MCC is closer to that of the PBAT matrix, it exhibits the better interfacial adhesion strength, resulting in the increased mechanical properties, crystallization temperature, storage modulus, and loss modulus. This work provides effective strategy for how to design fillers to obtain high-performance composites.

Hemicellulose and Nano/Microfibrils Improving the Pliability and Hydrophobic Properties of Cellulose Film by Interstitial Filling and Forming Micro/Nanostructure

In this paper, nano/microfibrils were applied to enhance the mechanical and hydrophobic properties of the sugarcane bagasse fiber films. The successful preparation of nano/microfibrils was confirmed by scanning electron microscope (SEM), X-ray diffraction (XRD), fiber length analyzer (FLA), and ion chromatography (IC). The transparency, morphology, mechanical and hydrophobic properties of the cellulose films were evaluated. The results show that the nanoparticle was formed by the hemicellulose diffusing on the surface of the cellulose and agglomerating in the film-forming process at 40 °C. The elastic modulus of the cellulose film was as high as 4140.60 MPa, and the water contact angle was increased to 113°. The micro/nanostructures were formed due to hemicellulose adsorption on nano/microfilament surfaces. The hydrophobicity of the films was improved. The directional crystallization of nano/microfibrous molecules was found. Cellulose films with a high elastic modulus and high elasticity were obtained. It provides theoretical support for the preparation of high-performance cellulose film.

Improvement of Gas Barrier Properties for Biodegradable Poly(butylene adipate-co-terephthalate) Nanocomposites with MXene Nanosheets via Biaxial Stretching

In order to ease the white pollution problem, biodegradable packaging materials are highly demanded. In this work, the biodegradable poly (butylene adipate-co-terephthalate)/MXene (PBAT/Ti₃C₂T_X) composite casting films were fabricated by melt mixing. Then, the obtained PBAT/Ti₃C₂T_X composite casting films were biaxially stretched at different stretching ratios so as to reduce the water vapor permeability rate (WVPR) and oxygen transmission rate (OTR). It was expected that the combination of Ti₃C₂T_X nanosheets and biaxial stretching could improve the water vapor and oxygen barrier performance of PBAT films. The scanning electron microscope (SEM) observation showed that the Ti₃C₂T_X nanosheets had good compatibility with the PBAT matrix. The presence of Ti₃C₂T_X acted as a nucleating agent to promote the crystallinity when the content was lower than 2 wt%. The mechanical tests showed that the incorporation of 1.0 wt% Ti₃C₂T_X improved the tensile stress, elongation at break, and Young’s modulus of the PBAT/Ti₃C₂T_X nanocomposite simultaneously, as compared with those of pure PBAT. The mechanical dynamical tests showed that the presence of Ti₃C₂T_X significantly improved the storage modulus of the PBAT nanocomposite in a glassy state. Compared with pure PBAT, PBAT-1.0 with 1.0 wt% Ti₃C₂T_X exhibited the lowest OTR of 782 cc/m²·day and 10.2 g/m²·day. The enhancement in gas barrier properties can be attributed to the presence of Ti₃C₂T_X nanosheets, which can increase the effective diffusion path length for gases. With the biaxial stretching, the OTR and WVPR of PBAT-1.0 were further reduced to 732 cc/m²·day and 6.5 g/m²·day, respectively. The PBAT composite films with enhanced water vapor and water barrier performance exhibit a potential application in green packaging.

Combining carvacrol and nisin in biodegradable films for antibacterial packaging applications

In this work, the feasibility of antibacterial biopolymeric films containing carvacrol (CRV) and a nisin commercial formulation (Nis) for potential food packaging applications was investigated. As polymer matrix, a commercial biodegradable polymer formulation of Mater-Bi (MB) was chosen due to its significant food packaging applications. CRV and Nis were chosen due to their well-established antibacterial properties and their potential synergistic effect. MB/CRV, MB/Nis, and MB/CRV/Nis systems were produced by melt mixing and compression molding. The mechanical properties of the films were evaluated by tensile tests. Differential scanning calorimetry was assessed aiming at investigating the effect of the two compounds and their mixture on the thermal properties of MB. The release profile of CRV and Nis from the MB-based films was evaluated in water at 4 °C by UV-Vis measurements and it was fitted with a power-law model. The antibacterial activity of MB-based films was tested in vitro against Listeria monocytogenes, Salmonella enteritidis, Escherichia coli, and Staphylococcus aureus. The combination of CRV and Nis strongly affected the properties of the MB-based films and ensured higher antibacterial activity if compared to MB/CRV and MB/Nis systems.