Poly (Lactic Acid)/Thermoplastic Starch Films: Effect of Cardoon Seed Epoxidized Oil on Their Chemicophysical, Mechanical, and Barrier Properties

Recent advancements in polyurethane-based membranes for gas separation

Gas separation membranes are critical in a variety of environmental research and industrial applications. These membranes are designed to selectively allow some gases to flow while blocking others, allowing for the separation and purification of gases for a variety of applications. Therefore, the demand for fast and energy-efficient gas separation techniques is of central interest for many chemical and energy production diligences due to the intensified levels of greenhouse and industrial gases. This encourages the researchers to innovate techniques for capturing and separating these gases, including membrane separation techniques. Polymeric membranes play a significant role in gas separations by capturing gases from the fuel combustion process, purifying chemical raw material used for plastic production, and isolating pure and noncombustible gases. Polyurethane-based membrane technology offers an excellent knack for gas separation applications and has also been considered more energy-efficient than conventional phase change separation methodologies. This review article reveals a thorough delineation of the current developments and efforts made for PU membranes. It further explains its uses for the separation of valuable gases such as carbon dioxide (CO2), hydrogen (H2), nitrogen (N2), methane (CH4), or a mixture of gases from a variety of gas spillages. Polyurethane (PU) is an excellent choice of material and a leading candidate for producing gas-separating membranes because of its outstanding chemical chemistry, good mechanical abilities, higher permeability, and variable microstructure. The presence of PU improves several characteristics of gas-separating membranes. Selectivity and separation efficiency of PU-centered membranes are enhanced through modifications such as blending with other polymers, use of nanoparticles (silica, metal oxides, alumina, zeolite), and interpenetrating polymer networks (IPNs) formation. This manuscript critically analyzes the various gas transport methods and selection criteria for the fabrication of PU membranes. It also covers the challenges facing the development of PU-membrane-based separation procedures.

Preparation of degradable chemically cross-linked polylactic acid films and its application on disposable straws

The semi-rigidity of the polylactic acid (PLA) molecular chain makes it brittle, poor impact resistance and barrier properties, which severely limits its practical applications. In this paper, a bio-based reactive plasticizer epoxy soybean oil (ESO) was used to improve the mechanical and barrier properties of maleic anhydride grafted polylactic acid (MAPLA) by the chemical reaction between the epoxy and anhydride group. Firstly, the optimum curing conditions were 93.5 °C, 100 °C, and 110.8 °C for 2 h. The effects of different mass fractions of ESO on the properties of MAPLA-ESO (ME) films were systematically investigated. It was found that when the content of ESO was 10 wt%, the tensile properties of the resulting ME films were the best, with a tensile strength of 35.2 MPa. And it had an elongation at break of 20.0 % and toughness of 5.4 MJ/m3, which increased to 690 % and 675 %, respectively, compared with pure MAPLA films. The chemically crosslinked ME films also displayed excellent water resistance, well degradation, low migration properties, and better performance than that of commercial paper straws and PLA straws, exhibiting great application potential as degradable disposable straws. Therefore, this work provides an effective way to develop high-performance, green, and degradable PLA films and products.

High-performance thermoplastic starch/poly(butylene adipate-co-terephthalate) blends through synergistic plasticization of epoxidized soybean oil and glycerol

Utilizing starch, an abundant polysaccharide, as the renewable filler to blend with poly(butylene adipate-co-terephthalate) (PBAT) is a feasible tactic to construct cost-effective and high-performance biodegradable materials. It's worth noting that the thermal processing properties of starch can be manipulated by its plasticized behavior. Herein, epoxidized soybean oil (ESO) and glycerol were used as the plasticizer for native corn starch and the plasticized starch was integrated with PBAT to manufacture starch-based biodegradable blend films. ESO breaks the hydrogen bonds between starch chains through the fatty chains grafting reaction and increases the distance between starch molecular chains due to the large molecular weight of ESO. Meanwhile, glycerol molecules are incorporated into the starch molecular chains, and fatty chains grafted starch chains, effectively reducing the intermolecular forces of molecular chains. On account of the synergistic plasticization of ESO and glycerol which possess good compatibility with PBAT, the PS_G20E10 blend film achieved a tensile strength, an elongation at break of 16.11 MPa and 612.09 %, and the balanced water and oxygen permeability properties.

Preparation, compatibility and barrier properties of attapulgite/poly (lactic acid)/thermoplastic starch composites

In this study, AT (attapulgite)/PLA/TPS biocomposites and films were prepared by melt blending technique using PLA and TPS as matrix, polyethylene glycol (PEG) as plasticizing modifier of PLA and AT clay as additive. The effect of AT content on the performance of AT/PLA/TPS composites was investigated. The results showed that, as the AT concentration increased, the fracture surface of the composite showed a bicontinuous phase structure when the AT content was 3 wt%. The rheological properties showed that the addition of AT resulted in more significant deformation of the minor phase, which reduced the phase size and led to lower complex viscosity, and more processability from the industrial perspective. The mechanical properties showed that the addition of AT nanoparticles could simultaneously improve the tensile strength and elongation at break of the composites, reaching a maximum at 3 wt% load. The water vapor barrier performance results showed that AT significantly improved the WVP of the film, and the moisture resistance performance was increased by 254 % compared with the PLA/TPS composite film within 5 h. In conclusion, the obtained AT/PLA/TPS biocomposites showed potential in packaging engineering and injection molding products, especially when renewability and full biodegradability of the material are required.

Co-Plasticization of Starch with Glycerol and Isosorbide: Effect on Retrogradation in Thermo-Plastic Cassava Starch Films

Thermoplastic starch (TPS) has emerged as an essential alternative to produce environmentally friendly packaging; however, retrogradation is a disadvantage that affects its shelf life. This study analyzed the co-plasticizing effect of isosorbide on the mechanical, thermal, physicochemical, and microstructural properties and the retrogradation of films obtained by blown film extrusion from thermoplasticized starch with mixtures of glycerol and isosorbide in different ratios (3:0, 2:1, 1:2, and 0:3, respectively). The results showed that the higher concentration of isosorbide significantly increased the tensile strength; however, it reduced the elongation. Retrogradation modeled using the Avrami equation showed that the presence of isosorbide reduced the retrogradation rate (k) and modified the recrystallization mechanism (n). The relative crystallinity in the plasticized TPS films was reduced to 89%, and the adsorption significantly decreased. Isosorbide was very important in reducing the retrogradation of TPS. The best performance was obtained with the 2:1 ratio of glycerol/isosorbide due to the synergistic effect between the plasticizers. The results would allow tuning the properties of TPS films by combining glycerol/isosorbide in different ratios, which enables the design of materials tailored to potential application requirements.

Understanding Marine Biodegradation of Bio-Based Oligoesters and Plasticizers

The study reports the enzymatic synthesis of bio-based oligoesters and chemo-enzymatic processes for obtaining epoxidized bioplasticizers and biolubricants starting from cardoon seed oil. All of the molecules had M_W below 1000 g mol^-1 and were analyzed in terms of marine biodegradation. The data shed light on the effects of the chemical structure, chemical bond lability, thermal behavior, and water solubility on biodegradation. Moreover, the analysis of the biodegradation of the building blocks that constituted the different bio-based products allowed us to distinguish between different chemical and physicochemical factors. These hints are of major importance for the rational eco-design of new benign bio-based products. Overall, the high lability of ester bonds was confirmed, along with the negligible effect of the presence of epoxy rings on triglyceride structures. The biodegradation data clearly indicated that the monomers/building blocks undergo a much slower process of abiotic or biotic transformations, potentially leading to accumulation. Therefore, the simple analysis of the erosion, hydrolysis, or visual/chemical disappearance of the chemical products or plastic is not sufficient, but ecotoxicity studies on the effects of such small molecules are of major importance. The use of natural feedstocks, such as vegetable seed oils and their derivatives, allows the minimization of these risks, because microorganisms have evolved enzymes and metabolic pathways for processing such natural molecules.

Toward Sustainable Wearable Electronic Textiles

Smart wearable electronic textiles (e-textiles) that can detect and differentiate multiple stimuli, while also collecting and storing the diverse array of data signals using highly innovative, multifunctional, and intelligent garments, are of great value for personalized healthcare applications. However, material performance and sustainability, complicated and difficult e-textile fabrication methods, and their limited end-of-life processability are major challenges to wide adoption of e-textiles. In this review, we explore the potential for sustainable materials, manufacturing techniques, and their end-of-the-life processes for developing eco-friendly e-textiles. In addition, we survey the current state-of-the-art for sustainable fibers and electronic materials (i.e., conductors, semiconductors, and dielectrics) to serve as different components in wearable e-textiles and then provide an overview of environmentally friendly digital manufacturing techniques for such textiles which involve less or no water utilization, combined with a reduction in both material waste and energy consumption. Furthermore, standardized parameters for evaluating the sustainability of e-textiles are established, such as life cycle analysis, biodegradability, and recyclability. Finally, we discuss the current development trends, as well as the future research directions for wearable e-textiles which include an integrated product design approach based on the use of eco-friendly materials, the development of sustainable manufacturing processes, and an effective end-of-the-life strategy to manufacture next generation smart and sustainable wearable e-textiles that can be either recycled to value-added products or decomposed in the landfill without any negative environmental impacts.

Supercritical CO2 Impregnation of Thymol in Thermoplastic Starch-Based Blends: Chemico-Physical Properties and Release Kinetics

The aim of the present study was to investigate starch-based materials, prepared in an environmentally friendly way and from renewable resources, suitable for the development of biodegradable active food packaging. For this purpose, a bioactive compound (thymol) was incorporated into thermoplastic starch (TPS) and a TPS blend with poly (ε-caprolactone) (TPS-PCL) by the supercritical CO₂ (scCO₂) impregnation process. Impregnation experiments with scCO₂ were carried out at a pressure of 30 MPa and temperatures in the range of 40-100 °C during 1 to 20 h. The structural, morphological, and thermal properties of the obtained materials were comprehensively evaluated. Bioactive component release kinetic studies were performed in water at 6 °C and 25 °C. It was shown that the scCO₂ impregnation process could be successfully employed for thymol loading into TPS and TPS-PCL. The process was significantly influenced by the operating temperature and time as well as content of PCL. The samples showed a controlled release of thymol within seven days with a higher amount of released thymol from the TPS-PCL blend. The obtained materials are solvent-free and release the bioactive component in a controlled manner.

The Green Era of Food Packaging: General Considerations and New Trends

Recently, academic research and industries have gained awareness about the economic, environmental, and social impacts of conventional plastic packaging and its disposal. This consciousness has oriented efforts towards more sustainable materials such as biopolymers, paving the way for the “green era” of food packaging. This review provides a schematic overview about polymers and blends of them, which are emerging as promising alternatives to conventional plastics. Focus was dedicated to biopolymers from renewable sources and their applications to produce sustainable, active packaging with antimicrobial and antioxidant properties. In particular, the incorporation of plant extracts, food-waste derivatives, and nano-sized materials to produce bio-based active packaging with enhanced technical performances was investigated. According to recent studies, bio-based active packaging enriched with natural-based compounds has the potential to replace petroleum-derived materials. Based on molecular composition, the natural compounds can diversely interact with the native structure of the packaging materials, modulating their barriers, optical and mechanical performances, and conferring them antioxidant and antimicrobial properties. Overall, the recent academic findings could lead to a breakthrough in the field of food packaging, opening the gates to a new generation of packaging solutions which will be sustainable, customised, and green.

Effect of surfactant content on rheological, thermal, morphological and surface properties of thermoplastic starch (TPS) and polylactic acid (PLA) blends

Miscibility in biopolymeric blends is a critical process that requires evaluation of the effect of surfactants or coupling agents under conditions similar to processing. Different mixtures in the molten state of plasticized starch and polylactic acid in the presence of a surfactant (Tween 20) at different concentrations were studied. This allowed knowing the rheological, thermal and surface behavior of the mixtures. The results of the dynamic rheological analysis showed increases in viscosity in the presence of the surfactant, in which strong interactions were produced at high shear rates that reflect possible crosslinking between the polymer chains, in addition to intermolecular interactions that were evidenced in the infrared spectrum. Likewise, the storage and loss modulus showed transitions mainly from viscous to elastic typical for thermoplastics. The thermogravimetric analysis did not show significant changes between the mixtures. However, the calorimetric analysis showed changes in the crystallinity of the mixtures, the tensoactive promotes greater freedom of movement and rearrangements in the microstructure with decrease of interface between polymers, and less compaction of the material induced by the emulsion. Analysis derived from biopolymeric films against contact with water shows significant changes. Interaction with water in short times (in the order of minutes) according to the sessile drop technique, favors hydrophilicity by increasing the concentration of Tween 20. However, interaction with water for prolonged times (in the order of hours), shows that the absorption reaches saturation in samples a stabilization in the absorption is observed. The results demonstrate that the miscibility of PLA in AS was achieved in the presence of the tween, under conventional processing conditions. The stability of the different formulations allows the production of films for packaging and biomedical applications.

Bio-based thermoplastic natural rubber based on poly(lactic acid)/thermoplastic starch/calcium carbonate nanocomposites

Bio-based thermoplastic natural rubber (TPNR) has recently received much attention due to its sustainability. TPNR based on natural rubber (NR), poly(lactic acid) (PLA), thermoplastic starch (TPS), and nano-precipitated calcium carbonate (NPCC) was fabricated using a twin-screw extruder with two different mixing sequences: MI (NPCC was first compounded with PLA) and MII (NPCC was initially compounded with TPS), and then converted to a sheet through cast sheet extrusion. A constant weight ratio of NR:PLA:TPS at 30:40:30 and varying concentrations of NPCC at 0.5, 1, 3, and 5 wt% were employed. The effects of NPCC and mixing sequence on the properties of NR/PLA/TPS/NPCC nanocomposites were investigated. The NR and TPS phases were dispersed in the PLA matrix. The nanocomposites loaded with a small amount of NPCC (0.5 and 1 wt%) showed increased tensile strength and Young's modulus. NPCC enhanced melt flowability, slightly improved the water vapor barrier property of the NR/PLA/TPS blend and caused decreased T_g, T_cc, and T_m of PLA in the nanocomposites. The PLA phase of the MI nanocomposites contained a higher amount of NPCC, consequently having greater PLA chain scission and poorer tensile properties than that of the MII nanocomposites.

Ulomoides dermestoides Coleopteran action on Thermoplastic Starch/Poly(lactic acid) films biodegradation: a novel, challenging and sustainable approach for a fast mineralization process

Ulomoides dermestoides (UL) are macroinvertebrates insects belonging to Tenebrionidae Coleopteran family. They were used to hasten, in five days, the biodegradation-mineralization of thermoplastic starch (TPS)-poly(lactic acid) (PLA) films, otherwise biodegradable under composting conditions. After the contact of TPS-PLA film with UL for five days, TPS was metabolized and PLA was hydrolysed, as evidenced by decreasing of hydroxyl and carbonyl group peaks intensity by FTIR spectra, increasing of 13% of PLA crystallinity by DSC thermograms, reduction of PLA and TPS thermal stability by TGA analysis; faecal residues evidenced two glass transition temperature T_g, at 33 °C and 57 °C, associated with depolymerized TPS and PLA, respectively. SEM micrographs highlighted consumption of TPS-PLA surface, while GPC analysis showed a decrease in PLA concentration by 20% during contact by UL. Mineralization tests evidenced UL boosted effect on TPS biodigestion-biodegradation (80%) and PLA biodisintegration (50%), envisaging a challenging perspective for end-life management of bioplastics in environmental conditions.

Effect of PVOH/PLA + Wax Coatings on Physical and Functional Properties of Biodegradable Food Packaging Films

Biodegradable polymers suffer from inherent performance limitations that severely limit their practical application. Their functionalization by coating technology is a promising strategy to significantly improve their physical properties for food packaging. In this study, we investigated the double coating technique to produce multifunctional, high barrier and heat-sealable biodegradable films. The systems consisted of a web layer, made of poly(lactide) (PLA) and poly(butylene-adipate-co-terephthalate) (PBAT), which was first coated with a poly(vinyl) alcohol based layer, providing high barrier, and then with a second layer of PLA + ethylene-bis-stereamide (EBS) wax (from 0 to 20%), to provide sealability and improve moisture resistance. The films were fully characterized in terms of chemical, thermal, morphological, surface and functional properties. The deposition of the PVOH coating alone, with a thickness of 5 μm, led to a decrease in the oxygen transmission rate from 2200 cm³/m² d bar, for the neat substrate (thickness of 22 μm), to 8.14 cm³/m² d bar (thickness of 27 μm). The deposition of the second PLA layer did not affect the barrier properties but provided heat sealability, with a maximum bonding strength equal to 6.53 N/25 mm. The EBS wax incorporation into the PLA slightly increased the surface hydrophobicity, since the water contact angle passed from 65.4°, for the neat polylactide layer, to 71° for the 20% wax concentration. With respect to the substrate, the double-coated films exhibited increased stiffness, with an elastic modulus ca. three times higher, and a reduced elongation at break, which, however still remained above 75%. Overall, the developed double-coated films exhibited performances comparable to those of the most common synthetic polymer films used in the packaging industry, underlining their suitability for the packaging of sensitive foods with high O₂-barrier requirements.

Poly(lactic acid)/thermoplastic cassava starch blends filled with duckweed biomass

Duckweed (DW) is a highly small, free-floating aquatic plant. It grows and reproduces rapidly, comprises mainly protein and carbohydrate, and has substantial potential as a feedstock to produce bioplastics due to its renewability and having very little impact on the food chain. The aim of this work was to analyze the effect of DW biomass on the characteristics and properties of bio-based and biodegradable plastics based on a poly(lactic acid)/thermoplastic cassava starch (PLA/TPS) blend. Various amounts of DW biomass were compounded with PLA and TPS in a twin-screw extruder and then converted into dumbbell-shaped specimens using an injection molding machine. The obtained PLA/TPS blends filled with DW biomass exhibited a lower melt flow ability, higher moisture content, and increased surface hydrophilicity than the neat PLA/TPS blend. Incorporation of DW with low concentrations of 2.3 and 4.6 wt% increased the tensile strength, Young's modulus, and hardness of the PLA/TPS blend. Moisture and glycerol from DW and TPS played important roles in reducing the T_g, T_cc, T_m, and T_d of PLA in the blends. The current work demonstrated that DW could be used as a biofiller for PLA/TPS blends, and the resulting PLA/TPS blends filled with DW biomass have potential in manufacturing injection-molded articles for sustainable, biodegradable, and short-term use.

Effects of Modified Thermoplastic Starch on Crystallization Kinetics and Barrier Properties of PLA

This study reports on using reactive extrusion (REX) modified thermoplastic starch particles as a bio-based and biodegradable nucleating agent to increase the rate of crystallization, percent crystallinity and improve oxygen barrier properties while maintaining the biodegradability of PLA. Reactive blends of maleated thermoplastic starch (MTPS) and PLA were prepared using a ZSK-30 twin-screw extruder; 80% glycerol was grafted on the starch during the preparation of MTPS as determined by soxhlet extraction with acetone. The crystallinity of PLA was found to increase from 7.7% to 28.6% with 5% MTPS. The crystallization temperature of PLA reduced from 113 °C to 103 °C. Avrami analysis of the blends showed that the crystallization rate increased 98-fold and t_1/2 was reduced drastically from 20 min to <1 min with the addition of 5% MTPS compared to neat PLA. Observation from POM confirmed that the presence of MTPS in the PLA matrix significantly increased the rate of formation and density of spherulites. Oxygen and water vapor permeabilities of the solvent-casted PLA/MTPS films were reduced by 33 and 19% respectively over neat PLA without causing any detrimental impacts on the mechanical properties (α = 0.05). The addition of MTPS to PLA did not impact the biodegradation of PLA in an aqueous environment.

Nutritional and Chemical-Physical Characterization of Fresh Pasta Gnocchi Prepared with Sea Water as New Active Ingredient

This study shows the chemical-physical and nutritional results obtained using food-grade sea water for the preparation of fresh pasta Gnocchi with respect to those prepared with tap water. Gnocchi obtained by mixing the flour with seawater (GSW) were compared with traditional Gnocchi made with tap water (GTW). The contents of sodium chloride, macro and micro elements, volatile molecules profile, thermal properties, and morphological analysis were investigated in both Gnocchi types. The analysis of chlorides showed that the samples prepared with sea water had a significantly lower NaCl content after cooking in comparison with those prepared with tap water. These results were also confirmed by the inductively coupled plasma (ICP) analysis for sodium content. The profiles of the volatile molecules acquired by gas chromatography-mass spectrometry (GC-MS) evidenced significant differences between the groups of aromatic molecules of the two typologies of samples. Morphological analysis evidenced that both raw and cooked GSW Gnocchi were structurally tightened whereas GTW Gnocchi showed a labile and weak macromolecular network. In addition, GSW Gnocchi was more thermally stable than GTW Gnocchi, as evidenced by thermogravimetric analysis (TGA).

Development of Polylactic Acid Thermoplastic Starch Formulations Using Maleinized Hemp Oil as Biobased Plasticizer

In this study, hemp seed oil was reacted with maleic anhydride in an ene reaction to obtain maleinized hemp seed oil (MHO). The use of MHO as a plasticizer and compatibilizer has been studied for polylactic acid (PLA) and thermoplastic starch (TPS) blends (80/20, respectively). By mechanical, thermal and morphological characterizations, the addition of MHO provides a dual effect, acting as plasticizer and compatibilizer between these two partially miscible biopolymers. The addition of MHO up to 7.5 phr (parts by weight of MHO per hundred parts of PLA and TPS) revealed a noticeable increase in the ductile properties, reaching an elongation at break 155% higher than the PLA/TPS blend. Furthermore, contrary to what has been observed with maleinized oils such as linseed oil, the thermal properties do not decrease significantly as a result of the plasticizing effect, due to the compatibilizing behavior of the MHO and the natural antioxidants present in the oil. Finally, a disintegration test was carried out in aerobic conditions at 58 °C, for 24 days, to demonstrate that the incorporation of the MHO, although causing a slight delay, does not impair the biodegradability of the blend, obtaining total degradation in 24 days.

Study of the Physical and Mechanical Properties of Thermoplastic Starch/Poly(Lactic Acid) Blends Modified with Acid Agents

In this work, we present a functionalization strategy of starch-poly(lactic acid) (PLA) blends with organic acids. Lactic and acetic acid were used as acid agents, and oleic acid was also included in the previous acids, with the aim of finding a synergy that thermodynamically benefits the products and provides hydrophobicity. The ratio of starch and sorbitol was 70:30, and the added acid agent replaced 6% of the plasticizer; meanwhile, the thermoplastic starch (TPS)–PLA blend proportion was 70:30 considering the modified TPS. The mixtures were obtained in a torque rheometer at 50 rpm for 10 min at 150 °C. The organic acids facilitated interactions between TPS and PLA. Although TPS and PLA are not miscible, PLA uniformly dispersed into the starch matrix. Furthermore, a reduction in the surface polarity was achieved, which enabled the wettability to reach values close to those of neat PLA (TPS–L-PLA increased by 55% compared to TPS–PLA). The rheological results showed a modulus similar to that of TPS. In general, there were transitions from elastic to viscous, in which the viscous phase predominated. The first and second-order thermal transitions did not show significant changes. The structural affinity of lactic acid with biopolymers (TPS–L-PLA) allowed a greater interaction and was corroborated with the mechanical properties, resulting in a greater resistance with respect to pure TPS and blended TPS–PLA (28.9%). These results are particularly relevant for the packaging industry.

Epoxidised sesame oil as a biobased coupling agent and plasticiser in polylactic acid/thermoplastic yam starch blends

This work aims to improve the physicochemical properties of polylactic acid (PLA) and thermoplastic yam starch (TPS) blends using epoxidised sesame oil (ESO). We used epoxidised sesame oil from two Colombian Caribbean crops: Dioscorea rotundata and Sesamum indicum, with an oil substitution of 58.4 %. Films were obtained through extrusion and compression moulding processes. Moisture content, solubility, contact angle, and mechanical, barrier, and structural properties were determined using optical and scanning electron microscopy, infrared Fourier transform spectroscopy. Thermal analyses were also performed using thermogravimetry and differential scanning calorimetry techniques. The results suggest that the PLA and TPS interactions can be improved with the addition of ESO as coupling agent, enhancing the interfacial adhesion between the polymers, and favouring the smoothness of the film surface. Furthermore, the ESO addition led to increased thermal stability while restricting molecular mobility, indicating a coupling agent effect. In conclusion, the use of epoxidised oil for preparing films based on high PLA content and TPS allows obtaining enhanced interfacial adhesion. Considering the above, the developed materials have potential application in semi-rigid food packaging.

Biodegradable polymers as carriers for tuning the release and improve the herbicidal effectiveness of Dittrichia viscosa plant organic extracts

BACKGROUND

The organic extracts (OEs) of Dittrichia viscosa, a ruderal plant common in the Mediterranean regions, proved to have herbicidal properties. In order to improve OE effectiveness and to develop novel eco-friendly bioherbicidal products, different amounts of OE were included in poly(butylene succinate)- and polycaprolactone-based films (PBS and PCL, respectively). Particular attention was given to the study of interactions between the polymers and OEs, with a deep spotlight concerning the influence of OEs on structural, morphological and thermal properties of both polymers, in order to assess the OE releasing kinetics from the matrices and its tuned herbicidal action against seeds.

RESULTS

The bioassays carried out on Lepidium sativum and Phelipanche ramosa seeds evidenced a more controlled and effective OE release by PBS than PCL, and a longer lasting efficacy by the polymers with a higher OE content. The chemical-physical analyses were performed on films before and after biological assays. The thermogravimetric analysis confirmed that OE was a thermal stabilizer of the polymer; the presence of OE and polymer separated degradative kinetics suggested that only a partial and functional miscibility between polymers and OE occurred. The morphological analysis confirmed the good OE dispersion between PBS and PCL molecular chains. Infrared spectroscopy highlighted the enhanced hydrolysed structure of the doped polymers after the bioassays. These outcomes well matched the quantitative information outlined by release kinetics.

DISCUSSION

The use of biodegradable polymers allows the effectiveness and tuning of the release of the formulated bioactive compounds to be improved. The easy-to-obtain and easy-to-formulate OE could become a suitable and environmentally friendly instrument in weed management programmes.

UV-Cured Biodegradable Methacrylated Starch-Based Coatings

Promising UV-curable starch-based coatings were fabricated by utilizing methacrylated starch. The aqueous methacrylated starch solution was cast on a glass substrate, and UV-cured after drying. The efficiency of UV-curing process was monitored with gel percentage measurements. The thermal and mechanical properties of the fabricated UV-cured coatings were investigated through differential scanning calorimetry and tensile test and compared with the starch-based uncured casted coatings. A complete characterization of the surface properties was performed by means of pencil hardness, adhesion, solvent resistance, and surface tension measurements. The cross-linking by UV-curing significantly enhanced the mechanical and surface properties of the coating. The effect of UV-curing on the biodegradability of the coating was evaluated by following the enzymatic degradation by α-amylase by determining the amount of glucose and maltose released from the coatings. UV-cured methacrylated starch based coating with promising material and surface properties and retained biodegradation potential was demonstrated.

In vivo and Post-synthesis Strategies to Enhance the Properties of PHB-Based Materials: A Review

The transition toward "green" alternatives to petroleum-based plastics is driven by the need for "drop-in" replacement materials able to combine characteristics of existing plastics with biodegradability and renewability features. Promising alternatives are the polyhydroxyalkanoates (PHAs), microbial biodegradable polyesters produced by a wide range of microorganisms as carbon, energy, and redox storage material, displaying properties very close to fossil-fuel-derived polyolefins. Among PHAs, polyhydroxybutyrate (PHB) is by far the most well-studied polymer. PHB is a thermoplastic polyester, with very narrow processability window, due to very low resistance to thermal degradation. Since the melting temperature of PHB is around 170-180°C, the processing temperature should be at least 180-190°C. The thermal degradation of PHB at these temperatures proceeds very quickly, causing a rapid decrease in its molecular weight. Moreover, due to its high crystallinity, PHB is stiff and brittle resulting in very poor mechanical properties with low extension at break, which limits its range of application. A further limit to the effective exploitation of these polymers is related to their production costs, which is mostly affected by the costs of the starting feedstocks. Since the first identification of PHB, researchers have faced these issues, and several strategies to improve the processability and reduce brittleness of this polymer have been developed. These approaches range from the in vivo synthesis of PHA copolymers, to the enhancement of post-synthesis PHB-based material performances, thus the addition of additives and plasticizers, acting on the crystallization process as well as on polymer glass transition temperature. In addition, reactive polymer blending with other bio-based polymers represents a versatile approach to modulate polymer properties while preserving its biodegradability. This review examines the state of the art of PHA processing, shedding light on the green and cost-effective tailored strategies aimed at modulating and optimizing polymer performances. Pioneering examples in this field will be examined, and prospects and challenges for their exploitation will be presented. Furthermore, since the establishment of a PHA-based industry passes through the designing of cost-competitive production processes, this review will inspect reported examples assessing this economic aspect, examining the most recent progresses toward process sustainability.

Bio-Based Active Packaging: Carrageenan Film with Olive Leaf Extract for Lamb Meat Preservation

Carrageenan-based active packaging film was prepared by adding olive leaf extract (OLE) as a bioactive agent to the lamb meat packaging. The OLE was characterized in terms of its phenolic compounds (T.ph), antioxidant activity (AA), oleuropein, and minimum inhibitory concentration (MIC) against Escherichia coli. The film’s formulation consisted of carrageenan, glycerol as a plasticizer, water as a solvent, and OLE. The effects of the OLE on the thickness, water vapor permeability (WVP), tensile strength (TS), elongation at break (EB), elastic modulus (EM), color, solubility, and antimicrobial capacity of the carrageenan film were determined. The OLE had the following excellent characteristics: the T.ph value was 115.96 mg_GAE∙g⁻¹ (d.b), the AA was 89.52%, the oleuropein value was 11.59 mg∙g⁻¹, and the MIC was 50 mg∙mL⁻¹. The results showed that the addition of OLE increased the thickness, EB, and WVP, and decreased the TS and EM of the film. The solubility was not significantly affected by the OLE. The color difference with the addition of OLE was 64.72%, which had the benefit of being a barrier to oxidative processes related to light. The film with the OLE was shown to have an antimicrobial capacity during the storage of lamb meat, reducing the count of psychrophiles five-fold when compared to the samples packed by the control and commercial films; therefore, this novel film has the potential to increase the shelf life of lamb meat, and as such, is suitable for use as active packaging.