Interlayer Adhesion Research Articles

Enhancement of the Sensing Performance of Devices based on Multistimuli-Responsive Hybrid Materials.

Capturing environmental stimuli is an essential aspect of electronic skin applications in robotics and prosthetics. Sensors made of temperature- and humidity-responsive hydrogel and piezoelectric zinc oxide (ZnO) core-shell nanorods have shown the necessary sensitivity. This is achieved by using highly conformal and substrate independent deposition methods for the ZnO and the hydrogel, i.e., plasma enhanced atomic layer deposition (PEALD) and initiated chemical vapor deposition (iCVD). In this work, we demonstrate that the use of a multichamber reactor enables performing PEALD and iCVD, sequentially, without breaking the vacuum. The sequential deposition of uniform as well as conformal thin films responsive to force, temperature, and humidity improved the deposition time and quality significantly. Proper interlayer adhesion could be achieved via in situ interface activation, a procedure easily realizable in this unique multichamber reactor. Beyond the fabrication method, also the mechanical properties of the template used to embed the core-shell nanorods and the cross-linker density in the hydrogel were optimized following the results of finite element models. Finally, galvanostatic electrochemical impedance spectroscopy measurements showed how temperature and humidity stimuli have different effects on the device impedance and phase, and these differences can be the basis for stimuli recognition.

High performance inorganic fullerene cage WS2 enhanced cement

An original cement based material enhanced with inorganic fullerene tungsten disulfide (IF-WS2) nanoparticles has been engineered with superb shock absorbing properties. Physical properties were attributed to the IF-WS2 nano-hollow multiple layered onion-like structure. The effect of IF-WS2 concentration at 0.1 wt%, 1 wt% and 5 wt% on the hydration kinetics of ordinary Portland cement (CEM1), electrical impedance, thermal stability, rheology and strength development was thoroughly evaluated. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies confirmed the formation of the new phase, calcium tungstate (CaWO4), at the nano-particle/cement matrix interface during early hydration. 1 wt% IF-WS2 additions enhanced the impact energy of CEM1 by 89% compared to the control. An IF-WS2 cementitious mixture was developed for 3D printing based on the 1% WS2-CEM composition. The mix exhibited excellent workability and buildability enabling the creation of a layer-by-layer printed component. Intimate interlayer adhesion minimized the presence of voids leading to a high flexural strength of 6.7 MPa, which equated to an over 86% improvement compared to plain CEM1 printed components. This study showcases IF-WS2 nanoparticles as a new ground-breaking additive enabling the production of high-performance cementitious construction materials, for use under extreme environments demanding high strength and impact resistance.

Application of intraoperative optical coherence tomography in deep lamellar keratoplasty

Objective: To evaluate the clinical application value of intraoperative optical coherence tomography (iOCT) in deep anterior lamellar keratoplasty (DALK) using the big-bubble technique to bare Descemet's membrane. Methods: Retrospective case series. Clinical data of 92 patients (92 eyes) with monocular stromal corneal diseases who underwent big-bubble DALK in the Eye Hospital of Shandong First Medical University from January 2020 to August 2021 were collected. There were 53 males and 39 females. The average age was (53.2±16.0) years old. All patients underwent iOCT scanning to determine the location and depth of the injection needle after initial removal of the corneal lesion, to observe the integrity of the recipient bed, Descemet's membrane, after complete lesion removal, and to observe the adhesion between the corneal graft and the recipient bed and check folds on the recipient bed after suturing of the corneal graft. The intraoperative perforation of Descemet's membrane, postoperative thickness of the cornea and the recipient bed, visual acuity, and corneal astigmatism were recorded. Results: By iOCT, the thickness of the recipient bed was found to be about 1/2 of the corneal thickness and relatively uniform in all directions in 62 eyes (67.4%), so the sterile air was injected from the center of the recipient bed to separate it from the stromal layer. In 30 eyes (32.6%) with an uneven thickness of the recipient bed, the sterile air was injected from the paracentral area of the recipient bed. Under the guidance of iOCT scanning, 89 eyes (96.7%) did not experience any perforation of Descemet's membrane during surgery. The Descemet's membrane folds in the central 5-mm area of the recipient bed was observed and flattened in 20 eyes with the assistance of iOCT scanning. The postoperative corneal thickness was (578.95±108.26) μm, and the recipient bed thickness was (36.06±23.11) μm. The best corrected visual acuity of all patients at 6 months after surgery was 0.57±0.25 logMAR, which was significantly better than that before surgery (1.61±1.27 logMAR; P<0.001). The average corneal astigmatism at 6 months after surgery was (2.72±2.44) diopters. Conclusions: The application of iOCT scanning in DALK surgery assisted by the big-bubble method can provide safe guidance for surgeons to adopt correct surgical procedures, decrease the risk of Descemet's membrane perforation, reduce the recipient bed folds, and facilitate corneal interlayer adhesion, thereby improving the visual prognosis.

Interlayer adhesion strength of 3D-printed cement-based materials exposed to varying curing conditions

This study explores the influences of the curing regime on the interlayer adhesion properties of 3D printed cement (3DPC) paste. Phase compositions, pore structure, and microstructure of typical specimens were obtained by XRD, TG, MIP, SEM and BSE analyses. The results show that the bond strength of the 3DPC sample is decreased by air curing (AC) and stream curing (SC), compared with constant standard curing (CSC) specimens. In contrast, CO2 curing (CC) results in a good enhancement on the interlayer adhesion strength of the 3DPC matrix. The high plastic viscosity behaves as an improvement on the adhesion properties of the printed specimens with the similar level fluidity. Either air curing or stream curing degraded the adhesion strength of the printed mixture owing to the influence of hydration and form a looser microstructure with high porosity in the micro interface of printed pastes. The decreased bond strength of printed samples induced by relatively low humidity can be alleviated by carbonation curing. Therefore, the sequestration of carbon dioxide treatment provides a potential method for pursuing higher bond strength and lower environmental impact to manufacture 3DPC cement.

Accelerated annealing of fused filament fabricated (FFF) thermoplastics via an improved core–shell filament

Thermoplastic parts manufactured via fused filament fabrication (FFF) have limited strength and toughness compared to other types of polymer additive and subtractive manufacturing. Low strength results from poor interlayer adhesion, making FFF parts not suitable for most engineering applications. Post processing solutions, such as annealing, enable healing of these interlayers, thus approaching injection molded parts. Prior work demonstrated a core–shell polycarbonate (PC)—acrylonitrile butadiene styrene (ABS) structured dual material filament to provide thermo-structural stability during annealing of the ABS component; however, annealing was limited to relatively low temperatures (135 °C) and required long annealing times (72 h). In the current work, a PC copolymer with a higher glass transition temperature (173 °C) than conventional PC is processed along with an extrusion-grade ABS into a PC-ABS core–shell filament. This improved dual material filament was printed, annealed, and evaluated via Izod impact testing, ultimately yielding 83% of bulk annealed ABS z-direction strength at an accelerated annealing time (8 h) and higher annealing temperature (155—175 °C). A demonstration part is printed with the dual material filament and annealed at 155 °C for 8 h, resulting in excellent dimensional accuracy, and a ductile failure at 73% higher ultimate load compared to the brittle failure of an as-printed part. This work highlights that material selection and design of a bicomponent filament geometry can lead to parts printed with FFF, with increased strength compared to other post-processing techniques at reduced processing times.

Long-Term Performance Analysis of Epoxy Resin Ultra-Thin Wearing Course Overlay on Cement Concrete Pavement

The overall rigidity of the cement concrete pavement is high, but there are defects such as easy cracking and insufficient anti-slip performance. The epoxy resin ultra-thin wearing course overlay can effectively solve these issues. However, there is still a lack of knowledge about the long-term performance of epoxy resin ultra-thin wearing course overlay on cement concrete pavement. Therefore, this article analyzed the interlayer adhesion and durability of epoxy resin ultra-thin wearing course overlay through the Hamburg rutting test and a series of shear tests under damp heat, thermal oxygen aging, and ultraviolet (UV) aging conditions. Shear test results indicated that the shear performance of epoxy resin overlay grew with the increase in epoxy resin content and was severely affected by high temperature, and the optimal content was set as 3.4 kg/m2. The Hamburg rutting test results showed that the epoxy resin overlay exhibited satisfactory high-temperature performance and water resistance. For the damp heat effect, it was revealed that damp heat led to more significant shear strength loss compared with the overlay specimens without damp heat. The water immersion caused the shear strength decline due to the water damage to the overlay interface. As for the thermal oxygen aging effect, it was reflected that the short-term thermal oxygen aging had a minor impact on the shear performance of the epoxy resin overlay. However, with the increase in thermal oxygen aging duration, the shear strength of the epoxy resin overlay significantly decreased due to the aging of epoxy resin binders. Regarding the UV aging impact, it was also found that the shear performance of the epoxy resin overlay rapidly decreased as the UV aging duration grew whether at 20 °C or 60 °C. Moreover, UV aging led to a more significant impact on the shear performance of the epoxy resin overlay than thermal oxygen aging.

Anti-marine biofouling adhesion performance and mechanism of PDMS fouling-release coating containing PS-PEG hydrogel

Polystyrene microspheres compounded with polyethylene glycol–based hydrogel (PS-PEG)/polydimethylsiloxane (PDMS) coatings were prepared using the physical blending method. The chemical structure, surface and interface properties, interlayer adhesion, and tensile properties were tested in this paper. Furthermore, the antifouling performance was evaluated through bovine serum albumin fluorescent protein adsorption testing, marine bacteria adhesion testing, and benthic diatom adhesion testing. The results showed that the coating performance was best when 20 wt% PS-PEG hydrogel was added. Its surface energy was only 19.21 mJ/m2, the maximum breaking strength was 1.24 MPa, the maximum elongation rate was 675 %, the elastic modulus was 2.53 MPa, and the anti-stripping rate was 100 %. In addition, the coating with added 20 wt% PS-PEG hydrogel bacterial adherence rate was 5.36 % and 2.45 % after rinsing and washing, respectively, and the removal rate was 54.29 %. In the benthic diatom adhesion test, the chlorophyll concentration a-value was only 0.0017 mg/L after washing with added 20 wt% hydrogel, and the protein desorption rate was 84.19 % higher than PDMS in the fluorescent protein adsorption test. This coating has the ‘low adhesion’ and ‘desorption’ characteristics in the three growth stages of biofouling. Meanwhile, the low surface energy of the silicone is stable, and the hydrogel also dynamically migrates to the surface to gradually form a hydration layer, both are synergistic. When 20 wt% PS-PEG hydrogel was added, the coating demonstrated excellent antifouling performance due to its high hydration layer, low surface energy, high elasticity, and high interlayer adhesion. This research is expected to contribute to the practical applications of hydrogel coatings in marine antifouling.

Interlayer adhesion of 3D printed concrete: Influence of layer stacked vertically

3D printed concrete is an emerging intelligent construction method, and it has been attracting an exponential attention in this sector. However, one of the major issues in printed concrete is the cold joint between the neighbor layers. In this study, an experimental study on the relation between the number of stacked layers vertically and the interlayer adhesion of 3D printed element was conducted. Splitting method was carried out to test the interlayer bond strength, mercury intrusion porosimetry (MIP) and X-ray computed tomography (X-CT) scanner were used to investigate the pore structure of the interlayer zone. The experimental results indicated that a markable influence of the stacked layers vertically on the interlayer adhesion is found. The interlayer bond strength in the middle interface of the printed element is higher than that of the upper and bottom interfaces, especially the bond strength in the bottom interface is the least. Such result is also reflected in the results of the MIP test: the lower total pore volume and total pore surface area existed in the middle interfaces. The X-CT results showed that a large number of elongated and flat pores present in the interlayer zone, the pores in the bottom interface tend to be interconnected or continuous due to the pressure of upper printed layers. An empirical model was proposed to account for the formation of the irregular pore and the change of bond strengths between the vertical neighbored layers of 3D printed element.

Enhanced interlayer adhesion of wetted graphene oxide by confined water bridge.

Graphene oxide (GO) sheets are widely used as building blocks in flexible electronic devices, structural materials, and energy storage technology owing to physicochemical flexibility and remarkable mechanical properties. GO exists as lamellar structures in these applications and, thus, it urges to enhance interface interaction to prevent interfacial failure. This study explores the adhesion of GO with and without intercalated water utilizing steered molecular dynamics (SMD) simulations. We find the interfacial adhesion energy (γ) depends on the synergistic effect of the types of functional groups, the degree of oxidation (c), and water content (wt). The intercalated monolayer water confined within GO flakes can improve the γ by more than 50% whereas the interlayer spacing is enlarged. The enhancement of adhesion is from the cooperative hydrogen bonding bridges between confined water and functional group on GO. Furthermore, the optimal water content wt = 20% and oxidation degree c = 20% are obtained. Our findings provide an experimentally available way to improve interlayer adhesion through molecular intercalation, which opens the possibility of high-performance laminate nanomaterial-based films for versatile applications.

Investigating the Effect of Nozzle Diameter on Tensile Strength in 3D-Printed Printed Polylactic Acid Parts

Three-dimensional (3D) printing is a rapidly evolving manufacturing technology that enables the production of intricate, customizable parts with a wide range of applications. The quality and mechanical properties of printed parts are heavily influenced by the process parameters, such as nozzle size. This study presents a comprehensive investigation of the effect of nozzle diameter on the tensile strength of 3D-printed polylactic acid (PLA) parts, focusing on six nozzle sizes: 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 mm. PLA, a commonly used thermoplastic in 3D printing, was employed as the material of choice. Using an open-source Fused Filament Fabrication (FFF) 3D printer, dog bone-shaped specimens were printed according to the ASTM D638-Type IV standard for tensile testing. The results reveal a strong correlation between nozzle size and tensile strength, with smaller nozzles producing parts with higher tensile strength due to finer layers and improved interlayer adhesion. However, the trade-off between tensile strength and printing time associated with smaller nozzle sizes must be considered when optimizing the 3D printing process for specific applications. This study provides essential insights into the influence of nozzle diameter on tensile strength, offering valuable guidance for achieving desired mechanical properties in 3D-printed parts.

Defect-Induced Modulation of a 2D ZnO/Graphene Heterostructure: Exploring Structural and Electronic Transformations

This paper presents a theoretical study on the effects of selected defects (oxygen vacancies and substitutional FeZn atoms) on the structural and electronic properties of a 2D ZnO/graphene heterostructure. Spin-polarized Hubbard- and dispersion-corrected density functional theory (DFT) was used to optimize the geometrical configurations of the heterostructure and to analyze the equilibrium distance, interlayer distance, adhesion energy, and bond lengths. Charge density difference (CDD) analysis and band structure calculations were also performed to study the electronic properties of the heterostructure. The results show that the presence of defects affects the interlayer distance and adhesion energy, with structures including oxygen vacancies and FeZn substitutional atoms having the strongest interaction with graphene. It is demonstrated that the oxygen vacancies generate localized defect states in the ZnO bandgap and lead to a shift of both valence and conduction band positions, affecting the Schottky barrier. In contrast, Fe dopants induce strong spin polarization and high spin density localized on Fe atoms and their adjacent oxygen neighbors as well as the spin asymmetry of Schottky barriers in 2D ZnO/graphene. This study presents a comprehensive investigation into the effects of graphene on the electronic and adsorption properties of 2D ZnO/graphene heterostructures. The changes in electronic properties induced by oxygen vacancies and Fe dopants can enhance the sensitivity and catalytic activity of the 2D ZnO/graphene system, making it a promising material for sensing and catalytic applications.

Improving interlayer bond in 3D printed concrete through induced thermo-hydrokinetics

For 3D printable concrete, lack of interlayer adhesion (IA) is an important consideration. This paper presents an experimental study to investigate a novel method to mitigate lack of IA by enhancing the interlayer bond strength through induced thermo-hydrokinetics. Thermo-hydrokinetics in this study describe the motions of heated fluids and/or the forces which produce or affect such motions. Thermo-hydrokinetics were induced by steaming the interlayer region of a substrate right before placement of a fresh filament layer. The method is applied at 3 different pass times; typical pass time for the arbitrarily selected object for printing, 5 min, and 10 min. A control for each pass time, on which thermo-hydrokinetics were not induced is also obtained. Direct tensile tests are performed to quantify the interlayer bond strength (IBS) of printed specimens. The experimental results show that inducing thermo-hydrokinetics in the interlayer region, even with increasing pass times, is beneficial for the tensile performance of the printed specimen. Steamed tensile specimens showed superior mechanical performance, achieving a 28-day overall mean IBS value of 2.8 MPa, which was a 78 % increase from that of non-steamed tensile specimens. The strength development of the specimens was also quantified, and it was shown that the rate of strength development for the steamed regime specimens was greater than that of the non-steamed regime. Furthermore, scanning electron microscope images provided information into the material in the interlayer region, illustrating that induced thermo-hydrokinetics altered the material in the interlayer region.

Autonomous alignment and healing in multilayer soft electronics using immiscible dynamic polymers.

Self-healing soft electronic and robotic devices can, like human skin, recover autonomously from damage. While current devices use a single type of dynamic polymer for all functional layers to ensure strong interlayer adhesion, this approach requires manual layer alignment. In this study, we used two dynamic polymers, which have immiscible backbones but identical dynamic bonds, to maintain interlayer adhesion while enabling autonomous realignment during healing. These dynamic polymers exhibit a weakly interpenetrating and adhesive interface, whose width is tunable. When multilayered polymer films are misaligned after damage, these structures autonomously realign during healing to minimize interfacial free energy. We fabricated devices with conductive, dielectric, and magnetic particles that functionally heal after damage, enabling thin-film pressure sensors, magnetically assembled soft robots, and underwater circuit assembly.

Graphene's effect and mechanism on the properties of alkali-activated slag coating

Using alkali-activated slag to prepare coatings is an alternative solution for concrete repair and protection. However, shrinkage cracking limits the application of alkali-activated slag, which also increases the risk of coating peeling. Graphene dispersions (content of 0.2%, 0.4%, 0.6% and 0.8%) were added to the alkali-activated slag coatings. The drying time, apparent circumstance (thicknesses of 1 mm, 2 mm, 3 mm and 5 mm) and the tensile bond strength with 1 mm thickness coating were determined. The mechanism of action was analyzed in terms of both product and interfacial properties. The experimental results showed that the graphene dispersion would shorten the drying time of the coatings. The drying time was reduced by 57.1% (from 116 min to 52 min). Moreover, the graphene dispersion improves the cracking of the coating. The larger the coating thickness is, the better it improves the cracking effect. The surface cracking of the coating with 5 mm thickness was reduced by 60.7% (from 1.6751% to 0.6583%). Graphene can significantly improve the bond strength of the coating. When the graphene content is 0.8%, the bonding strength with a thickness of 1 mm is 0.502 MPa at 7 days and 1.577 MPa at 28 days. The bond strength increased by 280.3% and 175.2%, respectively, XRD, FTIR and SEM analysis showed that the increase in bond strength was caused by two factors. (1) Graphene can promote the generation of zeolite phase in alkali-activated slag. This is conducive to enhancing the interlayer adhesion of the coating itself. (2) Graphene is beneficial to reduce the pores in the transition zone between the coating and the substrate and enhance the contact area between the coating and the substrate and makes the transition zone denser.

An experimental investigation on the effect of nano-graphene oxide on the maximum peeling force of Al/GFRP laminates

The effect of adding different percentages of nano-graphene oxide (NGO) into the epoxy resin on the mechanical properties of NGO/epoxy and maximum peeling force of fiber-metal laminates (FMLs) with composite cores are investigated in this paper. Three different percentages of NGO including 0.1, 0.35 and 0.50 weight percentages (wt. %) are used to fabricate the tensile test samples of NGO/epoxy. Hand lay-up method is used to fabricate FML specimens with glass fiber reinforced plastic (GFRP) core and aluminum faces. Tensile tests are examined and the Young’s modulus and ultimate stress of NGO/epoxy samples are determined. It is found that after adding of 0.1 wt. % of NGO into the epoxy resin, the ultimate tensile strength decreased by 13.4% from 25.3 to 21.9 MPa. Moreover, using peeling test, the separation force between aluminum faces of Al/GFRP laminates are obtained. Based on the results, when 0.1 wt. % of NGO is mixed with the epoxy, the maximum peeling force of FML increases by 16% and amounts to 4 N/mm. Based on the results, when NGO is used next to micro fibers in the construction of composite core, they have an effective role on the interlayer adhesion of fibrous composites.

Development and implementation of in-process, orbiting laser-assisted healing technique on fused filament fabrication

Fused filament fabrication is one of the most widely used additive manufacturing processes for producing thermal plastic polymer materials due to the affordable cost and capability to build objects with complex structures. However, parts fabricated with this process exhibit lower mechanical strength when compared to parts manufactured using traditional methods. In this work, an in-process orbiting laser healing technique is developed and implemented on a 3D printer to enhance mechanical strength by improving interlayer adhesion. The orbiting laser assembly can position and align the laser-heated spot before the change of nozzle direction occurs, ensuring that the previous layer is heated prior to material deposition. This laser-heating technique increases the bending strength along the build direction by 40% and reaches 88.9% of the strength along the longitudinal direction. With this technique, the displacement at fracture also increased by 54.3% compared to control sample. The thermal profile of the melting pool and fracture surface was further characterized using a thermal camera and SEM to support the effect of laser heating on polymer microstructure, respectively. Due to its enhanced print quality and lower cost, this technique has the potential to expand the application field of fused filament fabrication to small batch and series production that are currently dominated by injection molding, as well as the high-quality prototyping field.

Anti-Ballistic Performance of PPTA/UHMWPE Laminates.

Poly(p-phenylene terephthalamide) (PPTA) and ultra-high-molecular-weight polyethylene (UHMWPE) are high-performance polymer materials largely used for body armor applications. Although composite structures from a combination of PPTA and UHMWPE have been created and described in the literature, the manufacture of layered composites from PPTA fabrics and UHMWPE films with UHMWPE film as an adhesive layer has not been reported. Such a new design can provide the obvious advantage of simple manufacturing technology. In this study, for the first time, we prepared PPTA fabrics/UHMWPE films laminate panels using plasma treatment and hot-pressing and examined their ballistic performance. Ballistic testing results indicated that samples with moderate interlayer adhesion between PPTA and UHMWPE layers exhibited enhanced performance. A further increase in interlayer adhesion showed a reverse effect. This finding implies that optimization of interface adhesion is essential to achieve maximum impact energy absorption through the delamination process. In addition, it was found that the stacking sequence of the PPTA and UHMWPE layers affected ballistic performance. Samples with PPTA as the outermost layer performed better than those with UHMWPE as the outermost layer. Furthermore, microscopy of the tested laminate samples showed that PPTA fibers exhibited shear cutting failure on the entrance side and tensile failure on the exit side of the panel. UHMWPE films exhibited brittle failure and thermal damage at high compression strain rate on the entrance side and tensile fracture on the exit side. For the first time, findings from this study reported in-field bullet testing results of PPTA/UHMWPE composite panels, which can provide important insights for designing, fabricating, and failure analysis of such composite structures for body armors.

Penetration depth optimization for proper interlayer adhesion using near-infrared laser in a low-temperature process of PBF-LB/P

The aim of this study is to discuss the influence of the optical properties of powder bed such as penetration depth, on the depth of fusion and proper interlayer adhesion. A low-temperature process of PBF-LB/P, in which the underlying layer was solid, was performed to gain insight into optimizing the optical properties of this process. The penetration depth was widely adjusted using near-infrared laser (wavelength 1.06 μm), which has high transmittance through most polymers, and by adding an optical absorbing agent to PA12 powder. To investigate the relationship between the penetration depth and depth of fusion when a powder bed is formed on top of the underlying layer, the depth of fusion at each penetration depth was estimated based on microstructural observations and a thermal analysis of the built specimens. The results showed a positive correlation between the penetration depth and depth of fusion when compared with the unified volumetric energy of the laser. The influence of the penetration depth and/or depth of fusion on interlayer adhesion, as well as the part resolution in the stacking direction, were discussed. The interlayer adhesion strength was evaluated from a tensile test in the stacking direction of specimens prepared using different penetration depths. The results demonstrated that the interlayer adhesion increased with increasing the penetration depth and that it was saturated at a certain penetration depth. Moreover, the part resolution simply tended to decrease with increasing the penetration depth. Therefore, it was shown that optimization can be realized by determining the penetration depth at which interlaminar adhesion is saturated.

Development of Biodegradable Polyamide 4/Polyvinyl Alcohol/Poly(lactic acid) Multilayer Films with Tunable Water Barrier Property and Superior Oxygen Barrier Property

Poor mechanical and barrier properties of biopolymer-based packaging materials limit their widespread applications. The combination of biopolymers with different nature is considered an effective strategy to obtain complementary properties, but this method is always restricted by the incompatibility between matrices. To combine polyamide 4 (PA4) and poly(lactic acid) (PLA), which present excellent oxygen barrier and water barrier properties, respectively, this study puts forward the use of polyvinyl alcohol (PVA) as a bonding layer to connect them and form the PA4/PVA/PLA multilayer films by the layer-by-layer solution casting method. PA4 and PLA are successfully linked through hydrogen bonding and electrostatic interactions with PVA. The cross-section morphology and peel test results proved the good interlayer adhesion between layers. After combination with PA4, the tensile strength, elongation at break, and oxygen barrier properties of PLA were greatly improved. The oxygen barrier of the PA4/PVA/PLA multilayer film was more than 260 times higher than that of the PLA monolayer. PA4/PVA/PLA films presented better thermal stability, transparency, and water barrier properties compared to the PA4 monolayer. Besides, PA4/PVA/PLA multilayer films presented a one-way water barrier characteristic, which made them effective in avoiding the condensation phenomenon when used as fruit or vegetable packaging. The study improved the poor interfacial compatibility between PA4 and PLA and provided a simple strategy for developing sustainable packaging with excellent performance.

Molybdenum Disulphide Modified Polylactide for 3D Printed (FDM/FFF) Filaments.

MoS2 is an additive used to improve the tribological properties of plastics. In this work, it was decided to verify the use of MoS2 as a modifier of the properties of PLA filaments used in the additive FDM/FFF technique. For this purpose, MoS2 was introduced into the PLA matrix at concentrations of 0.025-1.0% by weight. Through extrusion, a fibre with a diameter of 1.75 mm was obtained. 3D printed samples with three different filling patterns were subjected to comprehensive thermal (TG, DSC and HDT), mechanical (impact, bending and strength tests), tribological and physicochemical characteristics. The mechanical properties were determined for two different types of fillings, and samples with the third type of filling were used for tribological tests. Tensile strength has been significantly increased for all samples with longitudinal filling with improvement up to 49%. In terms of tribological properties, higher values of the addition (0.5%) caused a significant increase of up to 457% of the wear indicator. A significant improvement in processing properties in terms of rheology was obtained (416% compared to pure PLA with the addition of 1.0%), which translated into more efficient processing, increased interlayer adhesion and mechanical strength. As a result, the quality of printed objects has been improved. Microscopic analysis was also carried out, which confirmed the good dispersion of the modifier in the polymer matrix (SEM-EDS). Microscopic techniques (MO, SEM) allowed for the characterization of the effect of the additive on changes in the printing process (improvement of interlayer remelting) and to assess impact fractures. In the tribological area, the introduced modification did not bring spectacular effects.