Effect of hydroxyl and carboxyl-functionalized carbon nanotubes on phase morphology, mechanical and dielectric properties of poly(lactide)/poly(butylene adipate-co-terephthalate) composites

Tailoring the structures and properties of biodegradable poly(lactic acid)/poly(butylene adipate-co-terephthalic acid) blends via reactive graphene oxide

In conventional elastomer-toughened PLA blends, the huge sacrifice in strength and modulus due to poor compatibility is a major problem plaguing such materials. In this work, oxide-epoxy-graphene (SGO-GMA) nanoparticles that can chemically react with both components of PLA/PBAT blends are prepared to serve as compatibilizer by "thiol-ene click" reaction. It is found that SGO-GMA tends to be dispersed in the PBAT phase thermodynamically. However, the one-step process, SGO-GMA is dispersed in both PBAT and PLA phases because of the chemical reaction limiting its migration, and the crystallization rate of the PLA phase is significantly increased. In contrast, in the two-step process, SGO-GMA is anchored at the interface by the in-situ reaction between epoxy groups in GMA with PLA and PBAT. Consequently, the mechanical properties of the samples prepared using a two-step process demonstrate a significant advantage. Specifically, incorporating 1 wt% SGO-GMA into PLA/PBAT blends results in simultaneous enhancements in tensile strength, elongation at break, and impact strength by 7.9%, 40.7%, and 57.1%, respectively. The improved mechanical properties that based on the roles functionalized GO compatibilization are expected to facilitate the application of PLA in tissue engineering materials, in vivo and in vitro medical devices and other fields.

Study on the Effects of Vibration Force Field on the Mixing and Structural Properties of PLA/PBS/EGMA Blends

This study investigates the effects of a vibration force field on the mixing and structural properties of polylactic acid (PLA), polybutylene succinate (PBS), and ethylene-glycidyl methacrylate terpolymer (EGMA) blends. A balanced triple-screw dynamic extrusion process was utilized to prepare PLA/PBS/EGMA composites under various vibration parameters, specifically amplitude and frequency. The results indicate that the introduction of a vibration force field significantly enhances the dispersion of the PLA/PBS/EGMA blend, leading to improved mechanical properties, thermal stability, and crystallization behavior. When the vibration frequency was 6 Hz and the amplitude was 1.0 mm, the impact strength increased from the steady-state value of 70.86 KJ/m2 to 88.21 KJ/m2. When the amplitude was 0.4 mm and the frequency was 10 Hz, the impact strength reached 81.86 KJ/m2. The orthogonal experimental design and entropy method analysis revealed that vibration frequency and amplitude play a dominant role in optimizing mechanical performance, whereas processing temperature and rotor speed exhibit minimal impact. Scanning electron microscopy (SEM) analysis confirmed that the vibration force field reduces phase separation, promoting a finer and more homogeneous dispersion of PBS and EGMA within the PLA matrix. Additionally, TGA and DTG curves suggest that when the vibration amplitude and frequency are lower than specific thresholds, the thermal stability of the blend deteriorates. In contrast, when they exceed those thresholds, thermal stability improves. For instance, with an amplitude of 1.0 mm, the initial degradation temperature (T5) climbs from 328.6 °C to 333.7 °C. At a frequency of 10 Hz, T5 reaches 333.1 °C. These findings provide theoretical support for the application of vibration-assisted extrusion in the development of high-performance biodegradable polymer blends.

Poly(lactide)/poly(butylene adipate-co-terephthalate)/carbon nanotubes composites with robust mechanical properties, fatigue-resistance and dielectric properties

A styrene-glycidylmethacrylate-1-allyl-3-vinylimidazole epoxy functionalized ionomer (EFI) was synthesized, and the EFI and carbon nanotubes (CNTs) were co-introduced into poly(lactide)/poly(butylene-adipate-co-terephtalate) (PLA/PBAT) blends to fabricate high performance composites with excellent mechanical properties, fatigue-resistance and dielectric properties. It is revealed that EFI can improve the interaction force between PLA and PBAT by inducing the interfacial crosslink reaction, thereby improving the melt strength of the samples. EFI can also refine the dispersion of CNT in the composites owing to the non-covalent force between EFI and CNT, promote the formation of filler network inside composites, which is demonstrated by DMA and rheological test results. The CNT can be anchored at the interface between PLA and PBAT owing to the interaction between EFI and CNT, and the synergistic effect of CNT and EFI on the interfacial structure and phase structure can significantly enhance the mechanical properties of the materials. When the CNT content is 3 wt%, the composite has a tensile strength of 30.4 MPa and an elongation at break of 279.3 %, which are 30 % and 48 % higher than that of PLA/PBAT blend, and it also exhibits excellent dielectric properties with a dielectric constant of 25.2 and a dielectric loss of 11.6. Moreover, the composites also have excellent fatigue resistance owing to the refined interfacial structure and compact CNT network.

Participation of Polymer Materials in the Structure of Piezoelectric Composites

This review explores the integration of polymer materials into piezoelectric composite structures, focusing on their application in sensor technologies, and wearable electronics. Piezoelectric composites combining ceramic phases like BaTiO3, KNN, or PZT with polymers such as PVDF exhibit significant potential due to their enhanced flexibility, processability, and electrical performance. The synergy between the high piezoelectric sensitivity of ceramics and the mechanical flexibility of polymers enables the development of advanced materials for biomedical devices, energy conversion, and smart infrastructure applications. This review discusses the evolution of lead-free ceramics, the challenges in improving polymer-ceramic interfaces, and innovations like 3D printing and surface functionalization, which enhance charge transfer and material durability. It also covers the effects of radiation on these materials, particularly in nuclear applications, and strategies to enhance radiation resistance. The review concludes that polymer materials play a critical role in advancing piezoelectric composite technologies by addressing environmental and functional challenges, paving the way for future innovations.

Enhancing Polylactic Acid Properties with Graphene Nanoplatelets and Carbon Black Nanoparticles: A Study of the Electrical and Mechanical Characterization of 3D-Printed and Injection-Molded Samples

This study investigates the enhancement of polylactic acid (PLA) properties through the incorporation of graphene nanoplatelets (GNPs) and carbon black (CB) for applications in 3D printing and injection molding. The research reveals that GNPs and CB improve the electrical conductivity of PLA, although conductivity remains within the insulating range, even with up to 10% wt of nanoadditives. Mechanical characterization shows that nanoparticle addition decreases tensile strength due to stress concentration effects, while dispersants like polyethylene glycol enhance ductility and flexibility. This study compares the properties of materials processed by injection molding and 3D printing, noting that injection molding yields isotropic properties, resulting in better mechanical properties. Thermal analysis indicates that GNPs and CB influence the crystallization behavior of PLA with small changes in the melting behavior. Dynamic Mechanical Thermal Analysis (DMTA) results show how the glass transition temperature and crystallization behavior fluctuate. Overall, the incorporation of nanoadditives into PLA holds potential for enhanced performance in specific applications, though achieving optimal conductivity, mechanical strength, and thermal properties requires careful optimization of nanoparticle type, concentration, and dispersion methods.

Insights into heterogeneous surface induced bubble nucleation mechanisms in cellulose reinforced polylactic acid foams

As the most abundant natural homo-polymer, cellulose has the potential to enhance polymer properties reducing the cost of raw materials. In this work, the carboxylate cellulose nanofiber (CNF-C) was selected to modify polylactic acid (PLA) foams, and the density functional theory was constructed to help analyze the foaming mechanism quantitatively. The theoretical results showed that the ordered structure, the carboxyl and the hydroxyl of CNF-C were more conducive to providing much stronger CO2 adsorption for bubble nucleation, where the predicted critical bubble size decreased and the cell density increased with the addition of CNF-C. The experimental results revealed that the CNF-C promoted the rheological properties and crystallization behaviors of PLA samples, the PLA/CNF-C foams were characterized with uniform structures, the average cell size decreased from 21.39 μm to 0.19 μm, and the cell number density increased from 2.65×1010cell/cm3 to 2.30×1014cell/cm3. Those improvements resulted in an increase of 394.0 % for the compressive strength of the prepared foams. Generally, the high-performance PLA/CNF-C foams were fabricated successfully without compromising the properties of bio-based and biodegradable, the foaming mechanism was analyzed combining theoretical results with experimental data, and it was believed to provide a guide for cellulose reinforcing biodegradable polymer materials.

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.

Strong synergistic toughening and compatibilization enhancement of carbon nanotubes and multi-functional epoxy compatibilizer in high toughened polylactic acid (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blends

Different carbon nanotubes (CNTs) contents on high-toughness polylactic acid (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blends were prepared by one-step melt blending using multifunctional epoxy oligomers (ADR) as reactive compatibilizer. During reactive blending, the PLA or PBAT chains were grafted onto the CNTs by allowing the carboxyl or hydroxyl groups to react with epoxy groups and form a branched CNTs-based copolymer. The branched copolymer at the interface between PLA and PBAT was dispersed through emulsion to improve the polymer-polymer or polymer-nanoparticle entanglement between the molecular chains. Interfacial adhesion, interface layer stability, and system viscoelasticity and compatibility were improved as indicated by rheological curves and dynamic mechanical analysis. The strength and toughness of the sample were simultaneously improved by the addition of CNTs and ADR. The impact strength reached 35.3 kJ/m2, which was approximately 7 times that of the PLA/PBAT blend, and the tensile strength was also increased from 33.6 MPa to 42.8 MPa. The properties of PLA/PBAT blend synergistically modified by ADR and CNTs were obviously better than those of PLA/PBAT blend modified by ADR or CNTs. The toughening synergistic effect of ADR and CNTs on PLA/PBAT was observed with efficiency reaching 3.05. With the further understanding of the toughening mechanism, the branched CNTs-based copolymers and CNTs clusters induce a synergistic effect, which increased the interfacial adhesion and ability of energy dissipation and stress transmission.

Super toughened blends of poly(lactic acid) and poly(butylene adipate-co-terephthalate) injection-molded foams via enhancing interfacial compatibility and cellular structure

Biodegradable poly(lactic acid) (PLA) foams have drawn increasing attention due to environmental challenges and petroleum crisis. However, it still remains a challenge to prepare PLA foams with fine cellular structures and high impact property, which significantly hinders its widespread application. Herein, phase interface-enhanced PLA/ poly(butylene adipate-co-terephthalate) (PBAT) blend foam, modified by a reactive compatibilizer through a simple reactive extrusion, was produced via a core-back foam injection molding technique. The obtained PLA blend foams displayed an impact strength as high as 49.1 kJ/m², which was 9.3 and 6.4 times that of the unmodified PLA/PBAT blend and its corresponding foam, respectively. It proved that the interfacial adhesion and cell size both strongly affected the impact strength of injection-molded PLA/PBAT foams, and two major conclusions were proposed. First, enhancing interfacial adhesion could cause a brittle-tough transition of PLA/PBAT foams. Additionally, for foams with high interfacial adhesion, small cell size (<12 μm) was more favorable for the stretching of cells and extension of the whitened region in comparison with big cell size (cell size >60 μm), leading to the drastic toughening of PLA blends. This study provides a feasible, industrially scalable and practical strategy to prepare super toughened and fully biodegradable PLA materials.

Fabricating super tough polylactic acid based composites by interfacial compatibilization of imidazolium polyurethane modified carbon nanotubes

The interfacial compatibilization and dispersion of carbon nanotubes (CNTs) in incompatible poly(lactic acid)/poly(butylene terephthalate adipate) (PLA/PBAT) composites are key points for evaluating the performance of the composites. To address this, a novel compatibilizer, sulfonate imidazolium polyurethane (IPU) containing PLA and poly(1,4-butylene adipate) segments modified CNTs, employed in conjunction with multi-component epoxy chain extender (ADR) to toughen synergistically PLA/PBAT composites. The thermal stability, rheological behavior, morphology, and mechanical properties of PLA/PBAT composites were performed by TGA, DSC, dynamic rheometer, SEM, tensile, and notched Izod impact measure. Moreover, the elongation at break and notched Izod impact strength of PLA5/PBAT5/4C/0.4I composites achieved 341 % and 61.8 kJ/m² respectively, whose tensile strength was 33.7 MPa. The interfacial compatibilization and adhesion were enhanced because of the interface reaction catalyzed by IPU and the refined co-continuous phase structure. The CNTs non-covalently modified by IPU that bridged at the PBAT phase and interface transferred the stress into the matrix, prevented the development of microcracks, and absorbed impact fracture energy in the form of pull-out of the matrix, inducing shear yielding and plastic deformation. This new type of compatibilizer with modified CNTs is of great significance for realizing the high performance of PLA/PBAT composites.

Highly toughened poly (lactic acid)/poly (butylene adipate-terephthalate) blends in-situ compatibilized by MMA-co-GMA copolymers with different epoxy group content

Poor compatibility limits the wide application of biodegradable poly (lactic acid)/poly (butylene adipate-terephthalate) (PLA/PBAT) blends in packaging industry. How to prepare compatibilizers with high efficiency and low cost by simple methods is a challenge. In this work, methyl methacrylate-co-glycidyl methacrylate (MG) copolymer with different epoxy group content are synthesized as reactive compatibilizers to resolve this issue. The effects of glycidyl methacrylate and MG contents on phase morphology and physical properties of the PLA/PBAT blends are systematically investigated. During melt blending, MG migrates to the phase interface, and then grafts with PBAT to form PLA-g-MG-g-PBAT terpolymers. When the molar ratio of MMA and GMA in MG is 3:1, the reaction activity of MG with PBAT is the highest and the compatibilization effect is the best. When the M₃G₁ content is 1 wt%, the tensile strength and the fracture toughness are increased to 37. 1 MPa and 120 MJ/m³, which increase by 34 % and 87 %, respectively. The size of PBAT phase decreases from 3.7 μm to 0.91 μm. Therefore, this work provides a low-cost and simple method to prepare the compatibilizers with high efficiency for the PLA/PBAT blend, and provides a new basis for the design of epoxy compatibilizers.

In-situ polycondensate-coated cellulose nanofiber heterostructure for polylactic acid-based composites with superior mechanical and thermal properties

Renewable yet biodegradable natural fiber (e.g., cellulose nanofiber (CNF)) reinforced bio-based polymers (e.g., polylactic acid (PLA)) are being applied for the manufacture of clean packaging products. The interface incompatibility between hydrophilic CNF and hydrophobic PLA still restricts the promotion of high-performance bio-based products. Herein, a polycondensate-coated CNF hybrid, wherein silane, aluminate, and titanate coupling agent monomers were in-situ polymerized onto the CNF surface via dehydration self-condensation, was designed and further employed as strengthening/toughening nanofillers for fabricating the CNF-reinforced PLA composite. Results showed that the polycondensate coatings could efficiently promote the dispersion of CNFs and enhance interfacial compatibility between CNFs and PLA. Attributing to the synergistic effect of polycondensate coatings and CNFs, a considerable improvement in processing, mechanical and thermal properties was obtained in resultant CNF/PLA composites. With adding 2.5 wt% polycondensate-coated CNFs, the tensile strength, Young's modulus, and tensile toughness of CNF-reinforced PLA composites was raised by about 27 %, 51 % and 68 %, respectively; also, such composite possessed greater elasticity and higher melt strength than pure PLA. This study provides a novel interface control strategy to fabricate low-cost yet high-performance PLA-based composites for sustainable packaging application.

Mechanically robust and flame-retardant poly(lactide)/poly(butylene adipate-co-terephthalate) composites based on carbon nanotubes and ammonium polyphosphate

In order to synchronously improve mechanical and flame retardant properties of polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) composites, a series of multifunctional composites containing multi-walled carbon nanotubes (CNTs), ammonium polyphosphate (APP) and a commercial multifunctional epoxy oligomer (MEO) as chain extender were prepared via melt blending. The results show that the optimal flame retardant properties of PLA5-PBAT5/10A/6C composite containing 6 % CNTs and 10 wt% APP, presented the limited oxygen index reached 28.3 % and exhibited a decrease in peak heat release rate (pHRR) and total heat release (THR) to 368 kJ/m² and 72 MJ/m², respectively because of the co-continuous phase, CNTs network and condensed effect of APP. Meanwhile, the construction of co-continuous phases endows PLA5-PBAT5 with better mechanical compared to PLA8-PBAT2 composites. The elongation at break reaches (245.9 %) and notched impact strength (16.5 kJ/m²) of PLA5-PBAT5/10A/6C were higher than the PLA8-PBAT2/10A/6C by 16.0 and 283.7 %.

Constructing a Superior Interfacial Microstructure on Carbon Fiber for High Interfacial and Mechanical Properties of Epoxy Composites

The interface quality is crucial for the properties of carbon fiber-reinforced polymer- matrix composites (CFRPs). In order to improve the interfacial and mechanical properties of CFRPs, a superior gradient modulus interfacial microstructure is constructed on the carbon fiber (CF) surface by chemically grafting a self-assembly carboxyl-terminated hyperbranched polymer (HP-COOH). A monofilament debonding test, a short beam shear test, an impact test and a dynamic mechanical thermal analysis (DMTA) were conducted to investigate the properties of the modified composite. Prominent improvements of 79.6% for the interfacial shear strength, 51.5% for the interlaminar shear strength, and 49.2% for the impact strength, as well as superior heat-resistance properties are achieved for composites with the gradient modulus interface over those of the untreated CF composites. The mechanism for performance improvement is mainly attributed to the enhanced CF surface energy, mechanical interlocking, and chemical bonding interactions. In particular, an atomic force microscopy (AFM) test proved that the gradient modulus interfacial microstructure formed by HP-COOH could widen the interface layer thickness and buffer the sharp variations in the modulus from CF to resin, thereby transmitting an external force and reducing the stress concentration. This work provides a facile and efficient strategy for constructing a superior and versatile interface for high- performance composites.

Hydrochar as an environment-friendly additive to improve the performance of biodegradable plastics

Plastic additives affect the properties of plastics, which further determine the application range of plastics. However, most plastic additives have environmental friendliness or performance issues limiting their application. Hydrochar (HC) from waste biomass by hydrothermal carbonization has been proved to contain organic matter as function substances, like a binder, and is environment-friendly material. Currently, hydrochar as a plastic additive has not been previously reported. In this study, the HC/PBAT composites were produced by hydrochar blending with poly (butylene adipate-co-terephthalate) (PBAT) which is a biodegradable polymer. The hydrochar produced at different hydrothermal carbonization temperatures (180 °C, 210 °C, 240 °C, 270 °C, and 300 °C) and the addition of hydrochar (10 wt%, 20 wt%) were investigated. The results showed that the elastic modulus of the composites was increased by 27.4 MPa and 32.5 MPa compared with virgin PBAT while adding 10 wt% and 20 wt% hydrochar, respectively. Moreover, the stiffness of the composite was improved, and the balance of stiffness and toughness of the composites was effectively maintained when adding 10 wt% hydrochar treated at 300 °C. The elongation at break, tensile strength, and the elastic modulus of its composites were 630.8 ± 13.7%, 23.0 ± 0.4 MPa, and 100.5 ± 2.7 MPa, respectively. Furthermore, the crystallization temperature of the composites was increased after hydrochar was added into PBAT, and the maximum was 87.9 °C. It also means that hydrochar has a great nucleation effect during plastic processing. Therefore, hydrochar can be used as an environment-friendly additive to promote the performance of biodegradable plastic and promise to be applied in the field of biodegradable plastics.

Microcellular injection molded lightweight and tough poly (L-lactic acid)/in-situ polytetrafluoroethylene nanocomposite foams with enhanced surface quality and thermally-insulating performance

High-performance microcellular polymer foams have been widely used all over the world, while the excessive usage of petroleum-based polymers caused serious environmental problems. As the eco-friendly awareness is increasing significantly, poly (L-lactic acid) (PLLA), as a typical biomass polymer, has gradually attracted widespread attention. However, the slow crystallization and poor melt strength of PLLA lead to low foaming ability and thus limiting its industrial applications. Herein, a novel and scalable strategy by coupling in-situ fibrillation and mold-opening microcellular injection molding (MOMIM) was developed to fabricate lightweight and tough PLLA/polytetrafluoroethylene (PTFE) foams. Thanks to the reticulated in-situ PTFE nanofibrils with a diameter of 100-200 nm, the crystallization and viscoelasticity of PLLA were dramatically promoted, and further contributing to its foaming ability. The expansion ratio of the MOMIM PLLA/PTFE foam was increased by 86 % compared with the regular microcellular injection molded (RMIM) PLLA foam. Moreover, the lower foam density and the toughening effect of PTFE nanofibrils resulted in the outstanding ductility of the PLLA/PTFE foams, whose tensile elongation, flexural strength, and impact strength were maximally increased by 52 %, 28 %, and 48 %, compared with PLLA foams. More importantly, the thermally-insulating performance and surface quality of PLLA/PTFE foams were also greatly improved.