Fabrication Of Composites Research Articles

Effect of filler orientation on mechanical and thermal properties of microwave absorbent 3D printed polycaprolactone/carbonyl iron particle composites

A thorough investigation was conducted in the present work on the mechanical and thermal characteristics of polycaprolactone/carbonyl iron particle composites. For composite fabrication, 3D printing technique was utilized. The fabricated composites were categorized as oriented, non-oriented and polycaprolactone samples based on orientation and concentration of filler particle. To evaluate the effect of orientation of carbonyl iron particle, two orientation directions, viz. parallel orientation, and perpendicular orientation with respect to loading direction were tried. The sample with parallel orientation exhibited the highest tensile strength followed by 90° orientation and pure polycaprolactone samples respectively. Oriented composites exhibited elevated dynamic modulus in comparison to the composites without orientation. The oriented composites demonstrated stiffness and tensile strength in the order of 13.66 ± 0.94 MPa and 3.79 ± 0.26 MPa respectively. The proposed methodology in the present study can be used to align carbonyl iron fillers in polymer matrix to tailor the mechanical, viscoelastic, and degradation properties.

Innovative Vancomycin-Loaded Hydrogel-Based Systems - New Opportunities for the Antibiotic Therapy.

Surgical site infections pose a significant challenge for medical services. Systemic antibiotics may be insufficient in preventing bacterial biofilm development. With the local administration of antibiotics, it is easier to minimize possible complications, achieve drugs' higher concentration at the injured site, as well as provide their more sustained release. Therefore, the main objective of the proposed herein studies was the fabrication and characterization of innovative hydrogel-based composites for local vancomycin (VAN) therapy. Presented systems are composed of ionically gelled chitosan particles loaded with vancomycin, embedded into biomimetic collagen/chitosan/hyaluronic acid-based hydrogels crosslinked with genipin and freeze-dried to serve in a flake/disc-like form. VAN-loaded carriers were characterized for their size, stability, and encapsulation efficiency (EE) using dynamic light scattering technique, zeta potential measurements, and UV-Vis spectroscopy, respectively. The synthesized composites were tested in terms of their physicochemical and biological features. Spherical structures with sizes of about 200 nm and encapsulation efficiencies reaching values of approximately 60% were obtained. It was found that the resulting particles exhibit stability over time. The antibacterial activity of the developed materials against Staphylococcus aureus was established. Moreover, in vitro cell culture study revealed that the surfaces of all prepared systems are biocompatible as they supported the proliferation and adhesion of the model MG-63 cells. In addition, we have demonstrated significantly prolonged VAN release while minimizing the initial burst effect for the composites compared to bare nanoparticles and verified their desired physicochemical features during swellability, and degradation experiments. It is expected that the developed herein system will enable direct delivery of the antibiotic at an exposed to infections surgical site, providing drugs sustained release and thus will reduce the risk of systemic toxicity. This strategy would both inhibit biofilm formation and accelerate the healing process.

Tailored Fabrication of Full-Color Ultrastable Room-Temperature Phosphorescence Carbon Dots Composites with Unexpected Thermally Activated Delayed Fluorescence.

The development of single-system materials that exhibit both multicolor room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) with tunable after glow colors and channels is challenging. In this study, four metal-free carbon dots (CDs) are developed through structural tailoring, and panchromatic high-brightness RTP is achieved via strong chemical encapsulation in urea. The maximum lifetime and quantum yield reaches 2141 ms and 56.55%, respectively. Moreover, CDs-IV@urea, prepared via coreshell interaction engineering, exhibits a dual afterglow of red RTP and green TADF. The degree of conjugation and functional groups of precursors affects the binding interactions of the nitrogen cladding on CDs, which in turn stabilizes triplet energy levels and affects the energy gap between S1 and T1 (ΔEST) to induce multicolor RTP. The enhanced wrapping interaction lowers the ΔEST, promoting reverse intersystem crossing, which leads to phosphorescence and TADF. This strong coreshell interaction fully stabilizes the triplet state, thus stabilizing the material in water, even in extreme environments such as strong acids and oxidants. These afterglow materials are tested in multicolor, time, and temperature multiencryption as well as in multicolor in vivo bioimaging. Hence, these materials have promising practical applications in information security as well as biomedical diagnosis and treatment.

Cytotoxicity, Corrosion Resistance, and Wettability of Titanium and Ti-TiB2 Composite Fabricated by Powder Metallurgy for Dental Implants

Objectives: Orthopedics and dentistry have widely utilized titanium alloys as biomaterials for dental implants, but limited research has been conducted on the fabrication of ceramic particle-reinforced Ti composites for further weight reductions. The current study compared titanium–titanium diboride metal composites (Ti-TiB2) with pure titanium (processed by powder metallurgy) in terms of toxicity, corrosion resistance, and wettability. Methods: First, cell lines of a primary dermal fibroblast normal human adult (HDFa) were used to test the cytocompatibility (in vitro) of the composite and pure Ti using an indirect contact approach. Corrosion testing was performed for the materials using electrochemical techniques such as potentiodynamic polarization in a simulated bodily fluid (SBF) in conjunction with a three-electrode electrochemical cell. The entire set of experimental tests was conducted according to the ASTM F746-04 protocol. The contact angles were measured during wettability testing in accordance with ASTM D7334-08. An X-ray diffractometer (XRD) was used to catalog every phase that was visible in the microstructure. A scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to determine the chemical composition. Results: The cytotoxicity tests revealed that there was no detectable level of toxicity, and there was no significant difference in the impact of either of the two materials on the viability of human fibroblasts. An increase in the corrosion resistance of the composite (0.036 ± 0.0001 mpy (millimeters per year)) demonstrated the development of a passive oxide coating. According to the findings, the composites showed a greater degree of hydrophilicity (contact angle 44.29° ± 0.28) than did the pure titanium (56.31° ± 0.47). Conclusions/Significance: The Ti-TiB2 composite showed no toxicity and better corrosion resistance and wettability than did pure Ti. The composite could be a suitable alternative to Ti for applications involving dental implants.

Composite wick heat pipe fabrication and performance study

A composite wick heat pipe is designed and prepared: a copper mesh is fixed on the copper pipe, and copper powder is filled in the gap between the mesh and the mandrel through the mandrel. A test device is assembled to test the maximum thermal conductive power and temperature stabilization time of the heat pipe. The results show that: the composite wick structure and the copper powder structure compared with the ultimate heat transfer performance increased by 20%, when the heat capacity is increased, the overall temperature difference will increase accordingly, and the optimal liquid injection rate of 100%, the ultimate power of up to 100 W, when filling with powder, it has the best thermal conductivity, the ultimate heat transfer power in the state of gravity is three times higher than that of the state of resistance to gravity, and it is 28.6% higher than that in the state of horizontality. The composite wick structure starts 17.6% faster than the copper powder structure.

A Solid-State Reaction in a Vapor Chamber: Synthesis of Bi2(MoO4)3 Nanorods as High-Capacity Anode for Lithium-Ion Batteries

Conversion- and alloying-type materials have been investigated as alternatives to intercalating graphite anodes of lithium-ion batteries for recent decades. However, the electrochemical pulverization and limitations in large-scale production of metal oxides prohibit them from practical applications. This work provided an ambient solid-state reaction accelerated by water vapor for synthesizing Bi2(MoO4)3 nanorods combined with carbon under mild-condition ball-milling for composite fabrication. The obtained composite performs superior electrochemical performance: a delivered capacity of 802.2 mAh·g−1 after 300 cycles at a specific current of 500 mA·g−1 with a retention of 82.3%. This improvement was ascribed to the better accommodation to volume variation and reinforced physical contact raised by one-dimensional morphology and ball-milling treatment. The complex conversion-intercalation-alloying mechanism of the lithium-ion storage in Bi2(MoO4)3 anode was also clarified using cyclic voltammetry and ex situ X-ray photoelectron spectroscopy results.

Fabrication and characterization of Zn-hydroxy double salt-loaded composite: Antimicrobial and flame-retardancy properties

Herein, a novel versatile composite comprising Zn-hydroxy double salt (ZnHDS) and tannic acid (TA) fillers within a polyvinyl alcohol-polyethylene imine (PVA-PEI) mixed matrix (ZnHDS-TA@PVA-PEI) was fabricated and characterized. This composite exhibited dual functionality as an antimicrobial agent and a flame retardant. The composite exhibited significant antimicrobial activity against E. coli and S. aureus strains. The incorporation of ZnHDS into TA@PVA-PEI significantly enhanced its antimicrobial efficacy and flame-retardancy. Clearing zones for the ZnHDS-TA@PVA-PEI against E. coli and S. aureus with 3.8 % ZnHDS loading were obtained as 8.5 and 5.5 mm, respectively. The ZnHDS-TA@PVA-PEI, with a 3.8 % ZnHDS loading, required 18.52 kJ/mol of energy to initiate its thermal decomposition and absorbed a net energy of 41.40 J/g during the process. The maximum weight loss rates for ZnHDS, PVA-PEI, TA@PVA-PEI, and ZnHDS-TA@PVA-PEI were 0.50, 0.75, 0.99, and 0.85 %/°C, respectively. Water solubility tests demonstrated augmented resistance to water with increasing ZnHDS content. The introduction of ZnHDS into TA@PVA-PEI significantly improved the flame-retardancy, was slow to ignite, and self-extinguished within seconds. The thermal decomposition process, antimicrobial activity, and flame-retardancy mechanisms of the composites are discussed. These results, along with the affordability, biocompatibility, and eco-friendliness of ZnHDS, revealed its potential for multiple applications.

A new mechanism of mechanical reinforcement for 3D printing CF/PA12 composite based on microwave treatment

AbstractAlthough 3D printing technology has been widely applied in fabrication of polymer composite, yet, it still exhibits low mechanical performance, restricting its application in structural materials. Herein, a new 3D printing polymer composite composed of carbon fiber and polyamide12 (PA12) is fabricated and subsequently treated by microwave treatment. It is found that the tensile strength and modulus of 3D printing CF/PA12 composite with microwave treatment are improved by 23.8% and 10.2% compared with the original specimen, respectively. Moreover, a new mechanism of mechanical reinforcement is investigated and proposed by nanoindentation and 3D X‐ray computed tomography. The work does not only confirm formation of 3D printing CF/PA12 composite with good mechanical properties, but also proposes a new mechanism of microwave treatment effect on 3D printing polymer composite based on carbon fiber.Highlights A new 3D printing CF/PA12 composite based on microwave treatment is developed. The 3D printing composite exhibits good mechanical properties. A new mechanism of mechanical reinforcement is proposed.

Investigation of mechanical properties and self‐healing efficiency of carbon fibers composites infused with unsaturated polyester vitrimer

AbstractUnsaturated polyester resins (UPR) are widely in composite manufacturing, particularly in the energy, wind, and construction sectors. When these composites sustain damage, defects or cracks, several methodologies are employed to heal and repair them to extend their lifespan while reducing environmental impacts. In this work, the use of vitrimeric UPR (UPRv) as a matrix for carbon fiber composite, was investigated in terms of healing efficiency by mechanical and thermal properties. Flexural and interlaminar shear strength tests revealed healing efficiencies exceeding 40% and 90%, respectively. These results were attributed to the transesterification exchange occurring within the crosslinked networks of UPRv. As described in our previous work, the incorporation of “Covalent Adaptable Networks (CANs)” enables the conversion of commercial thermoset (UPR) into vitrimeric resins, thereby providing reprocessing and healing capabilities. Furthermore, a comparison between pristine and healed composites with Mode I DCB and Mode II ENF tests, confirm how the introduction of vitrimer in composite facilitates the manufacturing of a self‐healing product, with a significant recovery of the original properties.Highlights Application of a previous synthetized vitrimeric unsaturated polyester resin (UPRv)—fabrication of CF's composites reinforced with UPRv—investigation of the self‐healing property of the developed laminates—potential application as green and sustainable composites.

Fabrication, Structural Characterization, and Photon Attenuation Efficiency Investigation of Polymer-Based Composites.

Experiments have assessed various polymer composites for radiation shielding in diverse applications. These composites are lighter and non-toxic when compared to lead (Pb), making them particularly effective in diagnostic imaging for shielding against low-energy photons. This study demonstrates the fabrication of four composites by combining a base material, specifically a high-density polyethylene (HDPE) polymer, with 10% and 20% silicon (Si) and silicon carbide (SiC), respectively. Additionally, 5% molybdenum (Mo) was incorporated into the composites as a heavy metal element. The composites obtained were fabricated into 20 disks with a uniform thickness of 2 mm each. Discs were exposed to radiation from a low-energy X-ray source (32.5-64.5 keV). The chemical and physical properties of composites were assessed. The shielding ability of samples was evaluated by determining the linear and mass attenuation coefficients (μ and μm), radiation protection efficiency (RPE), half-value layer (HVL), and mean free path (MFP). According to our findings, supplementing HDPE with additives improved the attenuation of beams. The μm values showed that composite X-ray shielding characteristics were enhanced with filler concentration for both Si and SiC. Polymer composites with micro-molecule fillers shelter X-rays better than polymers, especially at low energy. The HVL and MFB values of the filler are lower than those of the pure HDPE sample, indicating that less thickness is needed to shield at the appropriate energy. HC-20 blocked 92% of the incident beam at 32.5 keV. This study found that increasing the composite sample thickness or polymer filler percentage could shield against low-energy radiation.

The Effectiveness Mechanisms of Carbon Nanotubes (CNTs) as Reinforcements for Magnesium-Based Composites for Biomedical Applications: A Review.

As a smart implant, magnesium (Mg) is highly biocompatible and non-toxic. In addition, the elastic modulus of Mg relative to other biodegradable metals (iron and zinc) is close to the elastic modulus of natural bone, making Mg an attractive alternative to hard tissues. However, high corrosion rates and low strength under load relative to bone are some challenges for the widespread use of Mg in orthopedics. Composite fabrication has proven to be an excellent way to improve the mechanical performance and corrosion control of Mg. As a result, their composites emerge as an innovative biodegradable material. Carbon nanotubes (CNTs) have superb properties like low density, high tensile strength, high strength-to-volume ratio, high thermal conductivity, and relatively good antibacterial properties. Therefore, using CNTs as reinforcements for the Mg matrix has been proposed as an essential option. However, the lack of understanding of the mechanisms of effectiveness in mechanical, corrosion, antibacterial, and cellular fields through the presence of CNTs as Mg matrix reinforcements is a challenge for their application. This review focuses on recent findings on Mg/CNT composites fabricated for biological applications. The literature mentions effective mechanisms for mechanical, corrosion, antimicrobial, and cellular domains with the presence of CNTs as reinforcements for Mg-based nanobiocomposites.

Charge Storage Properties of Ferrimagnetic BaFe12O19 and Polypyrrole-BaFe12O19 Composites.

This investigation is motivated by an interest in multiferroic BaFe12O19 (BFO), which combines advanced ferrimagnetic and ferroelectric properties at room temperature and exhibits interesting magnetoelectric phenomena. The ferroelectric charge storage properties of BFO are limited due to high coercivity, low dielectric constant, and high dielectric losses. We report the pseudocapacitive behavior of BFO, which allows superior charge storage compared to the ferroelectric charge storage mechanism. The BFO electrodes show a remarkably high capacitance of 1.34 F cm-2 in a neutral Na2SO4 electrolyte. The charging mechanism is discussed. The capacitive behavior is linked to the beneficial effect of high-energy ball milling (HEBM) and the use of an efficient dispersant, which facilitates charge transfer. Another approach is based on the use of conductive polypyrrole (PPy) for the fabrication of PPy-BFO composites. The choice of new polyaromatic dopants with a high charge-to-mass ratio plays a crucial role in achieving a high capacitance of 4.66 F cm-2 for pure PPy electrodes. The composite PPy-BFO (50/50) electrodes show a capacitance of 3.39 F cm-2, low impedance, reduced charge transfer resistance, enhanced capacitance retention at fast charging rates, and good cyclic stability due to the beneficial effect of advanced dopants, HEBM, and synergy of the contribution of PPy and BFO.

Development of a low-temperature novel porous Si3N4–Al2O3 composite with excellent specific mechanical properties

Porous composites of Si3N4 and Al2O3 have potential applications for various engineering applications. Fabrication of porous ceramic composites is generally expensive due to the requirement of high sintering temperatures and expensive raw materials. A relatively simple, cost-effective, versatile, and novel processing technique with phosphoric acid performing the dual roles of binder and pore-former has been proposed in this work. Porous Si3N4–Al2O3 composites with up to 20 vol% Al2O3 content and porosities in the range of 37–54 vol% were fabricated at only 1200 °C. Young's modulus, flexural strength, and compressive strength of the porous composites were found to be in the range of 21–54 GPa, 31–110 MPa, and 39–103 MPa, respectively. The best combination of mechanical properties was achieved at 10 vol% Al2O3 content, which corresponded to 39 % total porosity. The combination of low density and good mechanical properties yielded outstanding specific properties, which are significantly higher than monolithic porous Si3N4. The excellent combination of a low processing cost, tunable porosity and pore morphology, outstanding mechanical properties, as well as the inherent chemical and thermal stability of these porous composites render them potentially very attractive as chemical filters, porous membranes, as well as porous preforms for interpenetrating metal/ceramic composites.

Highly electrically conductive MOF/conducting polymer nanocomposites toward tunable electromagnetic wave absorption

Metal-organic frameworks (MOFs) have attracted significant interest as self-templates and precursors for the synthesis of carbon-based composites aimed at electromagnetic wave (EMW) absorption. However, the utilization of high-temperature treatments has introduced uncertainties regarding the compositions and microstructures of resulting derivatives. Additionally, complete carbonization has led to diminished yields of the produced carbon composites, significantly limiting their practical applications. Consequently, the exploration of pristine MOF-based EMW absorbers presents an intriguing yet challenging endeavor, primarily due to inherently low electrical conductivity. In this study, we showcase the utilization of structurally robust Zr-MOFs as scaffolds to build highly conductive Zr-MOF/PPy composites via an inner-outer dual-modification approach, which involves the production of conducting polypyrrole (PPy) both within the confined nanoporous channels and the external surface of Zr-MOFs via post-synthetic modification. The interconnection of confined PPy and surface-lined PPy together leads to a consecutive and extensive conducting network to the maximum extent. This therefore entails outstanding conductivity up to ∼14.3 S cm−1 in Zr-MOF/PPy composites, which is approximately 1–2 orders of magnitude higher than that for conductive MOF nanocomposites constructed from either inner or outer modification. Benefiting from the strong and tunable conduction loss, as well as the induced dielectric polarization originated from the porous structures and MOF-polymer interfaces, Zr-MOF/PPy exhibits excellent microwave attenuation capabilities and a tunable absorption frequency range. Specifically, with only 15 wt.% loading, the minimum reflection loss (RLmin) can reach up to –67.4 dB, accompanied by an effective absorption bandwidth (EAB) extending to 6.74 GHz. Furthermore, the microwave absorption characteristics can be tailored from the C-band to the Ku-band by adjusting the loading of PPy. This work provides valuable insights into the fabrication of conductive MOF composites by presenting a straightforward pathway to enhance and regulate electrical conduction in MOF-based nanocomposites, thus paving a way to facilely fabricate pristine MOF-based microwave absorbers.

Preparation and properties of Janus nanoparticles at pickering emulsion interface

Janus nanomaterials are characterized by their anisotropic structural properties, wherein two distinct chemical compositions or polarities coexist inside the same structure. These materials are typically observed at the nanoscale or micrometer level and are mostly synthesized through chemical modification or organized assembly facilitated by intermolecular interactions. The preparation process of Janus material is contingent upon the intricacy of its structural complexity. Various preparation methods have been devised to address important aspects such the composition of components, control over size and morphology, and localized alteration of functionality such as interface protection, phase separation, microfluidic control, self-assembly, among others. The Pickering emulsion templating method is widely recognized as a highly effective approach for the synthesis of Janus particles. On the other hand, the structural composition and straightforward fabrication of Janus nanoparticles play a crucial role in facilitating the interface catalysis of Pickering emulsions. The paper employed literature review and literature analysis as research methods to investigate the assembly of Janus nanoparticles at the Pickering emulsion interface. Additionally, the study aimed to examine the properties and potential uses of Janus particles across different domains. The utilization of Janus materials has demonstrated promising potential in several applications such as emulsification, encapsulation, catalysis, drug delivery, battery separators, and the creation of superstructure materials.

Attuning doped ZnO-based composites for an effective light-driven mineralization of pharmaceuticals via PMS activation

Water treatment technologies need to go beyond the current control of organic contaminants and ensure access to potable water. However, existing methods are still costly and often inadequate. In this context, novel catalysts that improve the mineralization degree of a wider range of pharmaceuticals through more benign and less consuming methodologies are highly sought after. ZnO, especially when doped, is a well-known semiconductor that also excels in the photocatalytic removal of persistent organic pollutants. In this study, we investigated the effect of doping ZnO nanoparticles with either copper, gallium or indium on the structure, morphology, photophysical properties and photocatalytic mineralization of pharmaceuticals. Their architecture was further improved through the fabrication of composites, pairing the best performing doped ZnO with either BaFe12O19 or nickel nanoparticles. Their suitability was tested on a complex 60-ppm multi-pollutant solution (tetracycline, levofloxacin and lansoprazole). The activation strategy combined photocatalysis with peroxymonosulfate (PMS) as an environmentally friendly source of highly oxidative sulfate radicals. The alliance of doped ZnO and BaFe12O19 was particularly successful, resulting in magnetic microcroquette-shaped composites with excellent inter-component synergy. In fact, indium outperformed the other proposed metal dopants, exceeding 97% mineralization after 1 h and achieving complete elimination after 3 h. All composites excelled in terms of reusability, with no catalytic loss after 10 consecutive cycles and minimal leakage of metal ions, highlighting their applicability in water remediation.

A universal strategy towards the fabrication of ultra-high temperature ceramic matrix composites with outstanding mechanical properties and ablation resistance

Materials with both excellent mechanical properties and good ablation resistance are urgently needed for the applications of thermal protection system in extreme high temperature oxidizing environments. However, owing to the lack of efficient fabrication processes, the existing materials suffer from either insufficient mechanical properties or poor ablation resistance. Herein, we report a novel solid–liquid combination fabrication strategy that successfully achieves the efficient incorporation of ultra-high temperature ceramics into 3D continuous carbon fiber performs as well as rapid densification. The relative density of the green body approaches the cubic close packing of spherical particles. Using Cf/ZrB2–SiC as an example, the as-prepared composite exhibits outstanding mechanical properties with a flexural strength surpasses 600 MPa and an unprecedented work of fracture of 11,851 ± 838 J/m2, which is two orders of magnitude higher than that of the currently reported monolithic ultra-high temperature ceramics. Moreover, the high ZrB2 content endows the composites with excellent ablation resistance and is thus capable of maintaining long-term non-ablative conditions at 2500 °C. The strategy possesses remarkable universality and high design flexibility, providing a time-saving and cost-effective universal strategy for the on-demand design and fabrication of high-performance ceramic, carbon, metal, and polymer matrix composites.

Multi-scale corrosion behavior of Al/Ti/Fe multi-interfaces composites

In this study, we are presented a thermodynamics and kinetics model to reveal the corrosion sensitivities of Al/Ti/Fe multi-interface composites. The model demonstrates that impurity elements (Mn) and interface intermetallics alter the electrochemical polarization behavior of the Al and Fe layers, leading to a shift to cathodic control. Additionally, intermetallic compounds, which are formed at the interface enhance wear resistance and modify its electrochemical corrosion behavior. This study provides new insights into the interface corrosion mechanism of multi-interface composites and offers directions to improve the multi-interfaces composites corrosion resistance, which is an important step for future fabrication and applications of multi-interface composites.

Polylactic Acid Composites Reinforced with Eggshell/CaCO3 Filler Particles: A Review

Statistics reveal that egg production has increased in recent decades. This growth suggests there is a global rise in available eggshell biomass due to the current underutilization of this bio-waste material. A number of different applications for waste eggshells (WEGs) are known, that include their use as an additive in human/animal food, soil amendment, cosmetics, catalyst, sorbent, and filler in polymer composites. In this article, worldwide egg production and leading countries are examined, in addition to a discussion of the various applications of eggshell biomass. Eggshells are a rich supplement of calcium carbonate; therefore, they can be added as a particulate filler to polymer composites. In turn, the addition of a lower-cost filler, such as eggshell or calcium carbonate, can reduce overall material fabrication costs. Polylactic acid (PLA) is currently a high-demand biopolymer, where the fabrication of PLA composites has gained increasing attention due to its eco-friendly properties. In this review, PLA composites that contain calcium carbonate or eggshells are emphasized, and the mechanical properties of the composites (e.g., tensile strength, flexural strength, tensile elastic modulus, flexural modulus, and elongation (%) at break) are investigated. The results from this review reveal that the addition of eggshell/calcium carbonate to PLA reduces the tensile and flexural strength of PLA composites, whereas an increase in the tensile and flexural modulus, and elongation (%) at break of composites are described herein.

Adhesion to untreated polyethylene by diffusion: Effect of polyurethane adhesive molecular weight on polyethylene penetration

Polyethylene is the most consumed plastic globally; however, its poor adhesiveness poses serious challenges, particularly in the fabrication of composites and the recycling of mixed plastic waste. While these unfavorable properties are conventionally improved by pretreating the polyethylene surface, the treated surface frequently reverts to its original state over time, which is an unresolved drawback. Here, we describe a novel adhesion system; a polyurethane adhesive penetrates an amorphous part of untreated polyethylene and they form a mixing layer at the adhesive interface. The interfacial mixing layer forms upon heat treatment, even below the melting point of polyethylene and the polymers bind tightly at the interface via entanglement. The peel strength increases with increasing the thickness of the mixing layer. While decreasing the molecular weight of polyurethane promotes inter-diffusion, it also causes a decline in the mechanical strength of the polyurethane adhesive layer. Polyurethanes with optimally balanced molecular weight exhibit superior adhesion due to balance diffusivity and mechanical strength.