The effect of MDI on the structure and mechanical properties of poly(lactic acid) and poly(butylene adipate-co-butylene terephthalate) blends

Poly(butylene adipate-co-terephthalate)/Polylactic Acid/Tetrapod-Zinc Oxide Whisker Composite Films with Antibacterial Properties

Biodegradable composite films comprising of poly(butylene adipate-co-terephthalate) (PBAT), polylactic acid (PLA), and tetrapod-zinc oxide (T-ZnO) whisker were prepared by a melt-extrusion and blow molding process. The effect of the incorporation of the T-ZnO whisker (1 to 7 wt.%) in the PBAT/PLA blend film was studied systematically. The composite films with an optimal T-ZnO whisker concentration of 3 wt.% exhibited the highest mechanical (tensile strength ~32 MPa), rheological (complex viscosity~1200 Pa.s at 1 rad/s angular frequency), and gas barrier (oxygen permeability~20 cc/m2·day) properties, whereas the composite films with 7 wt.% T-ZnO whiskers exhibited the highest antibacterial properties. The developed composite films can find potential application as antibacterial food packaging materials.

Fractionated lignin as a green compatibilizer to improve the compatibility of poly (butylene adipate-co-terephthalate) /polylactic acid composites

Blending poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA) is a cost-effective strategy to obtain biodegradable plastic with complementary properties. However, the incompatibility between PBAT and PLA is a great challenge for fabricating high-performance composite films. Herein, the ethyl acetate fractionated lignin with the small glass transition temperature and low molecular weight was achieved and incorporated into the PBAT/PLA composite as a compatibilizer. The fractionated lignin can be uniformly dispersed within the PBAT/PLA matrix through a melt blending process and interact with the molecular chain of PBAT and PLA as a bonding bridge, which enhances the intermolecular interactions and reduces the interfacial tension of PBAT/PLA. By adding fractionated lignin, the tensile strength of the PBAT/PLA composite increased by 35.4 % and the yield strength increased by 37.7 %. Owing to lignin, the composite films possessed the ultraviolet shielding function and exhibited better water vapor barrier properties (1.73 ± 0.08 × 10-13 g·cm/cm2·s·Pa). This work conclusively demonstrated that fractionated lignin can be used as a green compatibilizer and a low-cost functional filler for PBAT/PLA materials, and provides guidance for the application of lignin in biodegradable plastics.

Improving the compatibility and toughness of sustainable polylactide/poly(butylene adipate-co-terephthalate) blends by incorporation of peroxide and diacrylate

Polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were compatibilized using dicumyl peroxide (DCP) and poly(ethylene glycol) 600 diacrylate (PEG600DA) through a one-step melt-blending process. The compatibility and performance of these blends were subsequently characterized. The results showed that grafts formed "in situ" effectively improved the compatibility and interfacial adhesion between PLA and PBAT phases. Melt viscosity and elasticity of both the PLA/PBAT/DCP and PLA/PBAT/DCP/PEG600DA blends evinced significant increases. Compared to PLA alone, both cold and melt crystallization abilities of the PLA/PBAT/DCP/PEG600DA blends were enhanced, with crystallinities increasing by 5 % - 10 %. Furthermore, the thermal stability, as well as hydrophobicity and oleophobicity of the compatibilized blends improved. In comparison with PLA, the elongation at break and notched impact strength for the PLA/PBAT/DCP/PEG600DA (60/40/0.1/4) blend achieved increases of 290 % and 44.23 kJ/m2, corresponding to improvements of 279 % and 1457 %, respectively. The toughening effect was substantially influenced by the ductile matrix (either a co-continuous phase or a flexible PBAT matrix) in addition to the strong interfacial adhesion and fine phase domain. These eco-friendly blends exhibit considerable potential for packaging articles and 3D printing products owing to their excellent mechanical properties and enhanced melt rheology.

Recent progress on biodegradable polylactic acid based blends and their biocomposites: A comprehensive review

Being less dependent on non-renewable resources as well as protecting the environment from waste streams have become two critical primers for a global movement toward replacing conventional plastics with renewable and biodegradable polymers. Despite all these efforts, only a few biodegradable polymers have paved their way successfully into the market. Polylactic acid is one of these biodegradable polymers that has been investigated thoroughly by researchers as well as manufactured on a large industrial scale. It is synthesized from lactic acid obtained mainly from the biological fermentation of carbohydrates, which makes this material a renewable polymer. Besides its renewability, it benefits from some attractive mechanical performances including high strength and stiffness, though brittleness is a major drawback of this biopolymer. Accordingly, the development of blends and biocomposites based on polylactic acid with highly flexible biodegradable polymers, specifically poly(butylene adipate co terephthalate) has been the objective of many investigations recently. This paper focuses on the blends and biocomposites based on these two biopolymers, specifically their mechanical, rheological, and biodegradation, the main characteristics that are crucial for being considered as a biodegradable substitution for conventional non-biodegradable polymers.

Effects of Chitosan Nanoparticles and 4,4' Methylene-Diphenyl Diisocyanate on the Polylactic Acid/Poly (Butyleneadipate-Co-Terephthalate) Composite Properties

Polylactic acid (PLA) is considered a mature alternative to synthetic plastics made from petroleum by-products, possessing the advantages of good mechanical strength. However, it also has some disadvantages such as brittleness and low toughness. In order to overcome and improve some of these unfavorable properties, PLA/PBAT composites were prepared by blending PLA with Poly (butylene adipate-co-terephthalate) (PBAT), and adding 4,4'-methylene diphenyl diisocyanate (MDI) and chitosan nanoparticles (ChNPs) as compatibilizers to investigate the effects of different compatibilizers on the properties of the composites. The main observations are as follows: FT-IR indicated that MDI did not add new groups, while the addition of ChNPs added a substantial amount of hydroxyl and methylene groups. The addition of both MDI and ChNPs did not have any effect on the crystalline shape of the composites, but could potentially reduce their crystallinity, increase the melt peak temperature, wet the boundary of the PLA and PBAT phases, decrease the size of the dispersed phases, reduce the number of dispersed phases, and improve interfacial compatibility. The incorporation of MDI increased the tensile strength from 13.02 MPa to 19.24 MPa, whereas the addition of ChNPs substantially enhanced the elongation at the break from 3.84% to 19.24%. Furthermore, the inclusion of MDI conferred enhanced moisture resistance, whereas the addition of ChNPs seemed to weaken the resistance to moisture.

Influence of a Multiple Epoxy Chain Extender on the Rheological Behavior, Crystallization, and Mechanical Properties of Polyglycolic Acid

This study investigated the impact of a multiple epoxy chain extender (ADR) on the rheological behavior, crystallization, and mechanical properties of polyglycolic acid (PGA). Tests of the torque and melt mass flow rate and dynamic rheological analysis were conducted to study the rheological behavior of PGA modified with ADR. The rheological results of the modified PGA showed a significantly increased viscosity and storage modulus with an increase in the ADR amount, which could be attributed to the chain extension/branching reactions between PGA and ADR. It was proved that ADR could be used as an efficient chain extender for tailoring the rheological performance of PGA. The Han plot of the modified PGA showed a transition of viscous behavior to elastic behavior, while the ADR content was increased from 0 to 0.9 phr. The formation of long-chain branches (LCBs) was confirmed via the Cole-Cole plot and weighted relaxation spectrum, wherein the LCBs substantially changed the rheological behavior of the modified PGA. The vGP plots predicted a star-type topological structure for the LCBs. The results of non-isothermal crystallization kinetics suggested that the crystallization of the modified PGA was predominantly homogeneous nucleation and three-dimensional growth. The crystallinity decreased slightly with the increase in the ADR amount. Compared to neat PGA, the modified PGA samples exhibited better tensile and flexural performances.

The Effect of Epoxidized Soybean Oil on the Physical and Mechanical Properties of PLA/PBAT/PPC Blends by the Reactive Compatibilization

Poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT)/poly (propylene carbonate) (PPC) multi-phase blends were prepared by melt processing technique under the presence of compatibilizer with various composition. The effect on the physical and the mechanical property with/without ESO was characterized with spectrophotometric analysis, mechanical properties, thermal properties, rheological properties and barrier properties, and the structure-properties relationship was assessed. ​​The functional groups of PPC were found to effective to improve an interaction with carboxyl/hydroxyl group of PLA/PBAT binary blends to enhance the mechanical and physical properties on multi-phase blend system. The presence of PPC in PLA/PBAT blend affected the reduction of voids on the interface phase resulting in enhancing the oxygen barrier properties. With addition of ESO, the compatibility of ternary blend was found to be enhanced since the epoxy group of ESO reacted with the carboxyl/hydroxyl group of PLA, PBAT, and PPC, and under the condition with critical content of 4 phr of ESO, the elongation behavior dramatically increased as compared to that of blends without ESO while affecting reduction of oxygen barrier properties. The effect of ESO as a compatibilizer was clearly observed from the overall performances of ternary blends, and the potential feasibility of the PLA/PBAT/PPC ternary blends as packaging materials was confirmed at this study.

Polylactic acid/tapioca starch/banana peel-based material for colorimetric and electrochemical biosensing applications

The rapidly growing electronic and plastic waste has become a global environmental concern. Developing advanced and environmentally safe agro-based materials is an emerging field with an enormous potential for applications in sensors and devices. Here, an agro-based material as membrane has been developed by incorporating tapioca starch and banana peel powder in polylactic acid, with uniform dispersibility and amorphous nature. The material was used for the development of electrochemical sensor for S-gene of SARS-CoV-2. Further, the membrane was used for the development of a non-invasive, colorimetric skin patch for the detection of glucose and a sensor for the assessment of fruit juice quality. Using OECD-recommended model systems, the developed membrane was found to be non-toxic towards aquatic and terrestrial non-target organisms. The developed conductive material opens new avenues in various electrochemical, analytical, and biological applications.

Processing Polymer Blends of Mater-Bi® and Poly-L-(Lactic Acid) for Blown Film Application with Enhanced Mechanical Strength

Mater-Bi^® is one of the most commercialized starch-based blends used in biodegradable flexible packaging. However, the high ductility and low stiffness of Mater-Bi^® might limit its application and developing a solution to tailor the stiffness and mechanical strength is highly desirable. In the present work, blends based on Mater-Bi^® and poly-L-(lactic acid) (PLLA) at a different ratio from 70/30 to 50/50 wt% were prepared via melt-extrusion and the effect of the PLLA content and Joncryl ADR^® as a reactive compatibilizing agent, on the mechanical properties, melts rheology, morphology and disintegration aptitude were investigated. The inclusion of PLLA in Mater-Bi^® has a marked beneficial effect on the tensile strength and stiffness of the blend while maintaining acceptable ductility. The addition of the reactive compatibilizing agent contributed to improving the strength and elongation at the break of the blend. The melt rheology of the blend was also affected by the ratio of the two components, mostly when the Joncryl ADR^® was present. The disintegration by biodegradation of the blend was preserved in the presence of PLLA, and it takes less than 30 days for the films to completely decompose and disintegrate under controlled composting conditions. Interestingly, a thin film from Mater-Bi^®/PLLA 60/40 was successfully prepared by blown film extrusion, demonstrating a good balance between stretchability (elongation at break exceeding 100%) and stiffness (1.8 GPa). This work opened to broadening the use of starch-based biodegradable plastic toward more demanding applications such as mulching films.

Triblock Copolymer Compatibilizers for Enhancing the Mechanical Properties of a Renewable Bio-Polymer

Poly(lactic acid) (PLA) is an emerging plastic that has insufficient properties (e.g., it is too brittle) for widespread commercial use. Previous research results have shown that the strength and toughness of basalt fiber reinforced PLA composites (PLA/BF) still need to be improved. To address this limitation, this study aimed to obtain an effective compatibilizer for PLA/BF. Melt-blending of poly(butylene adipate-co-terephthalate) (PBAT) with PLA in the presence of 4,4′-methylene diphenyl diisocyanate (MDI: 0.5 wt% of the total resin) afforded PLA/PBAT-MDI triblock copolymers. The triblock copolymers were melt-blended to improve the interfacial adhesion of PLA/BF and thus obtain excellent performance of the PLA-ternary polymers. This work presents the first investigation on the effects of PLA/PBAT-MDI triblock copolymers as compatibilizers for PLA/BF blends. The resultant mechanics, the morphology, interface, crystallinity, and thermal stability of the PLA-bio polymers were comprehensively examined via standard characterization techniques. The crystallinity of the PLA-ternary polymers was as high as 43.6%, 1.44× that of PLA/BF, and 163.5% higher than that of pure PLA. The stored energy of the PLA-ternary polymers reached 20,306.2 MPa, 5.5× than that of PLA/BF, and 18.6× of pure PLA. Moreover, the fatigue life of the PLA-ternary polymers was substantially improved, 5.85× than that of PLA/PBAT-MDI triblock copolymers. Thus, the PLA/PBAT-MDI triblock copolymers are compatibilizers that improve the mechanical properties of PLA/BF.

In Situ Formation of Microfibrillar PBAT in PGA Films: An Effective Way to Robust Barrier and Mechanical Properties for Fully Biodegradable Packaging Films

Poly(glycolic acid) (PGA) is a semicrystalline biodegradable polyester with high gas barrier properties. However, due to its poor processability and low ductility, PGA could hardly find applications in the packaging field. Here, a strategy was adopted for in situ generation of high-aspect-ratio flexible microfibrils with strong interface affinity for the PGA matrix. Because poly(butylene adipate-co-terephthalate) (PBAT) possesses impressive ductility, it was selected as the "fibrillar toughening phase" to enhance the ductility of PGA. Moreover, a chain extender was used to enhance the interfacial adhesion between the two polymers. The extrusion blown film technique was then used to develop fully biodegradable PGA/PBAT films with a superior combination of excellent barrier performance and robust mechanical properties. The PBAT phase can in situ form microfibrils under the influence of extensional flow. Simultaneously, the synergetic function of the extensional flow field could effectively promote the motion of the PGA molecular chain to develop an oriented crystalline microstructure. Because of the aligned oriented lamellar crystal of PGA and oriented PBAT fibril structures serving as robust "barrier walls" 60PGA/ADR blown films demonstrated dramatically improved resistance to oxygen and water vapor, with 59 and 44 times lower oxygen permeability and water vapor permeability, respectively, when compared to the neat PBAT blown film. As a result, PGA/PBAT blown films offer a variety of benefits, including superior ductility, toughness, and a strong gas barrier property. The potential of these films to degrade makes them a viable contender for replacing classical nondegradable packing films.

Municipal biowaste treatment plants contribute to the contamination of the environment with residues of biodegradable plastics with putative higher persistence potential

Biodegradable plastics (BDP) are expected to mineralize easily, in particular under conditions of technical composting. However, the complexity of the sample matrix has largely prevented degradation studies under realistic conditions. Here composts and fertilizers from state-of-the-art municipal combined anaerobic/aerobic biowaste treatment plants were investigated for residues of BDP. We found BDP fragments > 1 mm in significant numbers in the final composts intended as fertilizer for agriculture and gardening. Compared to pristine compostable bags, the recovered BDP fragments showed differences in their material properties, which potentially renders them less prone to further biodegradation. BDP fragments < 1 mm were extracted in bulk and came up to 0.43 wt% of compost dry weight. Finally, the liquid fertilizer produced during the anaerobic treatment contained several thousand BDP fragments < 500 µm per liter. Hence, our study questions, if currently available BDP are compatible with applications in areas of environmental relevance, such as fertilizer production.

Process-Induced Morphology of Poly(Butylene Adipate Terephthalate)/Poly(Lactic Acid) Blown Extrusion Films Modified with Chain-Extending Cross-Linkers

Process-induced changes in the morphology of biodegradable polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) blends modified with various multifunctional chain-extending cross-linkers (CECLs) are presented. The morphology of unmodified and modified films produced with blown film extrusion is examined in an extrusion direction (ED) and a transverse direction (TD). While FTIR analysis showed only small peak shifts indicating that the CECLs modify the molecular weight of the PBAT/PLA blend, SEM investigations of the fracture surfaces of blown extrusion films revealed their significant effect on the morphology formed during the processing. Due to the combined shear and elongation deformation during blown film extrusion, rather spherical PLA islands were partly transformed into long fibrils, which tended to decay to chains of elliptical islands if cooled slowly. The CECL introduction into the blend changed the thickness of the PLA fibrils, modified the interface adhesion, and altered the deformation behavior of the PBAT matrix from brittle to ductile. The results proved that CECLs react selectively with PBAT, PLA, and their interface. Furthermore, the reactions of CECLs with PBAT/PLA induced by the processing depended on the deformation directions (ED and TD), thus resulting in further non-uniformities of blown extrusion films.

A Comparative Study on the Aerobic Biodegradation of the Biopolymer Blends of Poly(butylene succinate), Poly(butylene adipate terephthalate) and Poly(lactic acid)

The aim of the present work is to evaluate the rate and mechanisms of the aerobic biodegradation of biopolymer blends under controlled composting conditions using the CO₂ evolution respirometric method. The biopolymer blends of poly (butylene adipate terephthalate) (PBAT) blended with poly (lactic acid) (PLA), and PBAT blended with poly (butylene succinate) (PBS) by melt extrusion, were tested to evaluate the amount of carbon mineralized under home and industrial composting conditions. The changes in the structural, chemical, thermal and morphological characteristics of the biopolymer blends before and after biodegradation were investigated by FT-IR, DSC, TGA, XRD and SEM. Both blends showed higher degradation rates under industrial composting conditions, when compared to home composting conditions. This was confirmed by FT-IR analysis showing an increase in the intensity of hydroxyl and carbonyl absorption bands. SEM revealed that there was microbial colony formation and disintegration on the surfaces of the biopolymer blends. The obtained results suggest that industrial composting conditions are the most suitable for an enhanced biodegradation of the biopolymer blends viz PBAT–PBS and PBAT–PLA.

The Effects of Chain-Extending Cross-Linkers on the Mechanical and Thermal Properties of Poly(butylene adipate terephthalate)/Poly(lactic acid) Blown Films

This study investigates the effects of four multifunctional chain-extending cross-linkers (CECL) on the processability, mechanical performance, and structure of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) blends produced using film blowing technology. The newly developed reference compound (M·VERA® B5029) and the CECL modified blends are characterized with respect to the initial properties and the corresponding properties after aging at 50 °C for 1 and 2 months. The tensile strength, seal strength, and melt volume rate (MVR) are markedly changed after thermal aging, whereas the storage modulus, elongation at the break, and tear resistance remain constant. The degradation of the polymer chains and crosslinking with increased and decreased MVR, respectively, is examined thoroughly with differential scanning calorimetry (DSC), with the results indicating that the CECL-modified blends do not generally endure thermo-oxidation over time. Further, DSC measurements of 25 µm and 100 µm films reveal that film blowing pronouncedly changes the structures of the compounds. These findings are also confirmed by dynamic mechanical analysis, with the conclusion that tris(2,4-di-tert-butylphenyl)phosphite barely affects the glass transition temperature, while with the other changes in CECL are seen. Cross-linking is found for aromatic polycarbodiimide and poly(4,4-dicyclohexylmethanecarbodiimide) CECL after melting of granules and films, although overall the most synergetic effect of the CECL is shown by 1,3-phenylenebisoxazoline.

Biodegradable Polyurethanes Based on Castor Oil and Poly (3-hydroxybutyrate)

Biodegradable polyurethanes (PUs) were produced from castor oil (CO) and poly (3-hydroxybutyrate) diol (PHBD) using hexamethylene diisocyanate as a crosslinking agent. PHBDs of different molecular weights were synthesized through transesterification of bacterial PHB and ethylene glycol by changing the reaction time. The synthesized PHBDs were characterized in terms of Fourier transform infrared and proton nuclear magnetic resonance spectroscopy. A series of PUs at different NCO/OH and CO/PHBD ratios were prepared. The resulting CO/PHBD-based PUs were then characterized in terms of mechanical and thermal properties. Increasing PHBD content significantly increased the tensile strength of CO/PHBD-based PUs by 300% compared to neat CO-based PU. CO/PHBD-based PUs synthetized from short chain PHBD exhibited higher tensile strength compared to those produced from long chain PHBD. As revealed by scanning electron microscopy analysis, such improvement in stiffness of the resulting PUs is due to the good compatibility between CO and PHBD. Increasing PHBD content also increased the crystallinity of the resulting PUs. In addition, higher degradation rates were obtained for CO/PHBD-based PUs synthetized from long chain PHBD compared to neat CO PU and PUs produced from short chain PHBD.

Effect of talc and diatomite on compatible, morphological, and mechanical behavior of PLA/PBAT blends

Biodegradable nanocomposites were prepared by melt blending biodegradable poly(lactic acid) (PLA) and poly(butylene adipate-co-butylene terephthalate) (PBAT) (70/30, w/w) with diatomite or talc (1–7%). From the SEM test, the particles were transported to the interface of two phases, which acted as an interface modifier to strengthen the interfacial adhesion between PLA and PBAT. Talc and diatomite acted as nucleating agents to improve the crystallization of PBAT in the blends by DSC analysis. Moreover, adding the particles improved the tensile and impact toughness of the blends. The elongation at break with 5% talc was 78% (vs ∼21%) and the impact strength was 15 kJ/m2 (vs ∼6.5 kJ/m2). The rheological measurement revealed that the talc and diatomite reduced the viscosity of the blends. The results showed a good possibility of using talc- and diatomite-filled PLA/PBAT blends with high toughness for green-packaging and bio-membranes application.

Morphological and mechanical properties of biodegradable poly(glycolic acid)/poly(butylene adipate-co-terephthalate) blends with in situ compatibilization

In the present work, the biodegradable blends of poly(glycolic acid) (PGA) and poly(butylene adipate-co-terephthalate) (PBAT) with in situ compatibilization using 4,4'-methylenebis(phenyl isocyanate) (MDI) were prepared. The combined results of FTIR, DSC, SEM, DSC, POM, TGA and rheology demonstrated that the MDI was successfully reacted with PGA/PBAT, the complex viscosity and storage moduli (G') of the blends were increased. Melt elasticity and viscosity of the blends were also increased on increasing the concentration of PBAT. SEM results indicated that the compatibility was improved by in situ compatibilization. Due to the apparent differences in melting temperature (T m) between PGA and PBAT, the morphology of the dispersed phase evolved from a spherical structure to in situ microfiber when the content of PBAT was up to 60% during injection molding. The interfacial adhesion between PGA and PBAT was strengthened, consequently, the impact strength of the blend was sharply increased from 9.0 kJ m-2 to 22.2 kJ m-2. On account of the chain extension effect, the crystallinity, crystallization temperature and crystallization size were decreased, which was also of benefit for the improvement of toughness. Meanwhile, the thermal stability of the PGA was improved through blending with PBAT. A novel biodegradable blending material with enhanced toughness and thermal stability was prepared.

Effect of blending procedures and reactive compatibilizers on the properties of biodegradable poly(butylene adipate-co-terephthalate)/poly(lactic acid) blends

The effect of Joncryl ADR®-4368 (abbreviated ADR) and dicumyl peroxide (DCP) on poly(butylene adipate-co-terephthalate) (PBAT)/poly(lactic acid) (PLA) blend was investigated. Two different blending procedures were adopted: (1) one-step blending of all components for 8 min; (2) premixing of PBAT and ADR (or DCP) for 4 min followed by addition of PLA blending for 4 min. ADR and DCP were effective compatibilizers for the PBAT/PLA blend by one-step blending which were confirmed by improving the phase interface between PBAT and PLA, decreasing the dispersed phase size, increasing the elasticity, viscosity and tensile strength. Moreover, the addition of ADR into PBAT/PLA blend by two-step blending was more efficient than the one-step blending based on refined morphology and further increased tensile properties. The two-step blending was beneficial to produce a larger amount of PBAT-graft-PLA (PBAT-g-PLA) copolymers at the phase interface. However, DCP was added to the PBAT/PLA blend by the two-step blending which showed lower properties than one-step blending. DCP triggered free branching reactions in a fast way. Based on the character of compatibilizers, choosing properly blending procedures can enlarge the tensile properties. These results would be interesting for industrial polymer materials, and may be importance to the wider practical application of PBAT/PLA blends.

Effects of Methylenediphenyl 4,4'-Diisocyanate and Maleic Anhydride as Coupling Agents on the Properties of Polylactic Acid/Polybutylene Succinate/Wood Flour Biocomposites by Reactive Extrusion

Polylactic acid (PLA)/polybutylene succinate (PBS)/wood flour (WF) biocomposites were fabricated by in situ reactive extrusion with coupling agents. Methylenediphenyl 4,4'-diisocyanate (MDI) and maleic anhydride (MA) were used as coupling agents. To evaluate the effects of MDI and MA, various properties (i.e., interfacial adhesion, mechanical, thermal, and viscoelastic properties) were investigated. PLA/PBS/WF biocomposites without coupling agents revealed poor interfacial adhesion leading to deteriorated properties. However, the incorporation of MDI and/or MA into biocomposites showed high performances by increasing interfacial adhesion. For instance, the incorporation of MDI resulted in improved tensile, flexural, and impact strengths and an increase in tensile and flexural modulus was observed by the incorporation of MA. Specially, remarkably improved thermal stability was found in the PLA/PBS/WF biocomposites with 1 phr MDI and 1 phr MA. Also, the addition of MDI or MA into biocomposites increased the glass transition temperature and crystallinity, respectively. For viscoelastic property, the PLA/PBS/WF biocomposites with 1 phr MDI and 1 phr MA achieved significant enhancement in storage modulus compared to biocomposites without coupling agents. Therefore, the most balanced performances were evident in the PLA/PBS/WF biocomposites with the hybrid incorporation of small quantities of MDI and MA.

Blends of poly(butylene adipate-co-terephthalate) (PBAT) and stereocomplex polylactide with improved rheological and mechanical properties

Schematic representation of formed solid sc-PLA in the PBAT melting during melt processing.

Preparation and Characterization of Bio-Based PLA/PBAT and Cinnamon Essential Oil Polymer Fibers and Life-Cycle Assessment from Hydrolytic Degradation

Nowadays, the need to reduce the dependence on fuel products and to achieve a sustainable development is of special importance due to environmental concerns. Therefore, new alternatives must be sought. In this work, extruded fibers from poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) added with cinnamon essential oil (CEO) were prepared and characterized, and the hydrolytic degradation was assessed. A two-phase system was observed with spherical particles of PBAT embedded in the PLA matrix. The thermal analysis showed partial miscibility between PLA and PBAT. Mechanically, Young's modulus decreased and the elongation at break increased with the incorporation of PBAT and CEO into the blends. The variation in weight loss for the fibers was below 5% during the period of hydrolytic degradation studied with the most important changes at 37 °C and pH 8.50. From microscopy, the formation of cracks in the fiber surface was evidenced, especially for PLA fibers in alkaline medium at 37 °C. This study shows the importance of the variables that influence the performance of polyester-cinnamon essential oil-based fibers in agro-industrial applications for horticultural product preservation.

Preparation and Characterization of Corn Starch Bio-Active Edible Packaging Films Based on Zein Incorporated with Orange-Peel Oil

Zein, corn starch (CS), and orange-peel oil (OPO) extracted from orange peels were used to prepare novel corn starch/orange-peel oil/zein nanocapsules (OZN) bio-active food packaging materials. The results showed that the OZN were round, smooth and in compact morphology with an average diameter of 102.7 ± 10.5 nm from OPO and zein (3:10, w/w). By testing the turbidity and atomic force microscopy (AFM) of OZN and the mechanical properties and water vapor permeability of the composite films, the comprehensive properties of composite films with different mass ratios were analyzed. It showed that the addition of OZN improved the mechanical and moisture barrier properties and extended the release time of OPO. When the ratio of OZN and CS is 5:5, the highest elongation at break and tensile strengths is achieved, at values of 30.91% ± 2.52% and 12.19 ± 1.97 MPa respectively. The relative release concentration of OPO was highest at a ratio of 5/5, and over time it would last longer to maintain a higher release concentration. Besides, the oxidation resistance of the composite film was good, especially when the ration of starch CS to OZN was 5/5, it had the highest DPPH radical scavenging activity (30.16% ± 1.69%). Thus, it can be used as a bio-active edible food packaging film to ensure the safety of food products and reduce environmental pressure to some extent.

Morphology and Properties of a New Biodegradable Material Prepared from Zein and Poly(butylene adipate-terephthalate) by Reactive Blending

In this study, zein, a renewable natural biopolymer from corn, was used to prepare a new biodegradable material with poly(butylene adipate-terephthalate) (PBAT) by reactive blending in the presence of poly(ethylene glycol diglycidyl ether) (PEGDGE). The effects of blending temperature and zein content on the morphology and mechanical and thermal properties of PBAT/zein blends with or without PEGDGE were investigated. Because of the high reactivity of the epoxy group in PEGDGE, the interfacial compatibility between zein and PBAT was improved greatly, and zein exhibited as a spheral phase with smaller size and finer dispersion in the PBAT matrix after the introduction of PEGDGE. Therefore, PEGDGE served as a plasticizer and reactive compatibilizer in the PBAT/zein blending system. Both the tensile strength and elongation at break of the blends with PEGDGE were improved greatly compared with those of the blends without PEGDGE but decreased gradually with the increase of zein content. These findings may provide a feasible way to utilize zein widely, and the new biodegradable blends with excellent stretchability could be used as packing materials in the future.