Polyethylene Terephthalate Surface Research Articles

Manipulating Stem Cell Fate with Disordered Bioactive Cues on Surfaces: The Role of Bioactive Ligand Selection.

The development of 2D or 3D bioactive platforms for rapidly isolating pure populations of cells from adult stem cells holds promise for advancing the understanding of cellular mechanisms, drug testing, and tissue engineering. Over the years, methods have emerged to synthesize bioactive micro- and nanostructured 2D materials capable of directing stem cell fate. We introduce a novel method for randomly micro- or nanopatterning any protein/peptide onto both 2D and 3D scaffolds via spray technology. Our goal is to investigate the impact of arranging bioactive micropatterns (ordered vs disordered) on surfaces to guide human mesenchymal stem cell (hMSC) differentiation. The spray technology efficiently coats materials with controlled, cost-effective bioactive micropatterns in various sizes and shapes. BMP-2 mimetic peptides were covalently grafted, individually or in combination with RGD peptides, onto activated polyethylene terephthalate (PET) surfaces through a spraying process, incorporating nano/microscale parameters like size, shape, and composition. The study explores different peptide distributions on surfaces and various peptide combinations. Four surfaces were homogeneously functionalized with these peptides (M1 to M4 with various densities of peptides), and six surfaces with disordered micro- and nanopatterns of peptides (S0 to S5 with different sizes of peptide patterns) were synthesized. Fluorescence microscopy assessed peptide distribution, followed by hMSC culture for 2 weeks, and evaluated osteogenic differentiation via immunocytochemistry and RT-qPCR for osteoblast and osteocyte markers. Cells on uniformly peptide-functionalized surfaces exhibited cuboidal forms, while those on surfaces with disordered patterns tended toward columnar or cuboidal shapes. Surfaces S4 and S5 showed dendrite-like formations resembling an osteocyte morphology. S5 showed significant overexpression of osteoblast (OPN) and osteocyte markers (E11, DMP1, and SOST) compared to control surfaces and other micropatterned surfaces. Notably, despite sharing an equivalent quantity of peptides with a homogeneous functionalized surface, S5 displayed a distinct distribution of peptides, resulting in enhanced osteogenic differentiation of hMSCs.

Preparation of robust superhydrophobic surface on PET substrate using Box-Behnken design and facile sanding method with PTFE powder

Superhydrophobic surfaces have attracted increasing interests due to their excellent features, while achieving facile preparation of superhydrophobic surface with good mechanical stability is still a challenging work. In this paper, we prepared a superhydrophobic surface by sanding polytetrafluoroethylene powder directly onto the surface of a polyethylene terephthalate (PET) film by means of a simple sanding method with sandpaper. The fabrication parameters were firstly optimized using response surface methodology. Surface morphology and chemical composition of the fabricated surface were characterized by field emission scanning electron microscopy, Fourier transform infrared and x-ray photoelectron spectroscopy. The mechanical performance of the superhydrophobic PET surfaces was evaluated by tape peeling test, and potential applications of this surface in self-cleaning and anti-icing were finally carried out. The results showed that the water contact angle up to 153.5° and sliding angle less than ∼3° on PET surface could be prepared under the optimum conditions, and its superhydrophobicity of surfaces was attributed to the synergistically effect of low surface energy and surface roughness. The fabricated superhydrophobic surfaces also exhibited good resistance to abrasion, and they have great potential for application in the fields of self-cleaning and anti-icing.

Acid-base properties and modeling by quantum chemistry of adhesion interactions at the interface of thermoplastic-aluminum systems

Thermoplastic-aluminum systems are used in the manufacture of corrosion-resistant lightweight constructions in aerospace and automotive industries. The adhesion strength of such systems is determined by the mechanism of adhesion interaction. In this article, adhesion interactions between the surfaces of polyethylene terephthalate, poly(propylene carbonate), poly(methyl methacrylate), polystyrene, polypropylene and aluminum were studied to identify a correlation between the acid-base properties of the studied surfaces, the mechanism of adhesion interaction and energy characteristics in thermoplastic-aluminum systems using experimental and theoretical approaches. The experimental approach consisted of finding the values of the free surface energy components, the acidity parameters of thermoplastics and aluminum by the E.J. Berger and van Oss-Chaudhuery-Good methods. The theoretical approach consisted of the study of adhesion interactions in thermoplastic-aluminum systems using the quantum chemistry method B3LYP-GD3/6-31G(d,p). It was theoretically established the functional groups to be the active sites on the thermoplastics surface. At the same time, the strongest adhesion interaction is manifested in systems formed by a carbonyl oxygen atom.The experimental values of the components of the free surface energy of thermoplastics and aluminum are in good agreement with the theoretical values of the energy and force of the adhesion interaction of the systems under consideration.

5G NB-IoT System Integrated with High-Performance Fiber Sensor Inspired by Cirrus and Spider Structures.

Real-time telemedicine detection can solve the problem of the shortage of public medical resources caused by the coming aging society. However, the development of such an integrated monitoring system is hampered by the need for high-performance sensors and the strict-requirement of long-distance signal transmission and reproduction. Here, a bionic crack-spring fiber sensor (CSFS) inspired by spider leg and cirrus whiskers for stretchable and weavable electronics is reported. Trans-scale conductive percolation networks of multilayer graphene around the surface of outer spring-like Polyethylene terephthalate (PET) fibers and printing Ag enable a high sensitivity of 28475.6 and broad sensing range over 250%. The electromechanical changes in different stretching stages are simulated by Comsol to explain the response mechanism. The CSFS is incorporated into the fabric and realized the human-machine interactions (HMIs) for robot control. Furthermore, the 5G Narrowband Internet of Things (NB-IoT) system is developed for human healthcare data collection, transmission, and reproduction together with the integration of the CSFS, illustrating the huge potential of the approach in human-machine communication interfaces and intelligent telemedicine rehabilitation and diagnosis monitoring.

Analysis and identification of degradation products in gas, particle, and liquid phases of polypropylene and polyethyleneterephthalate microplastics aging through non-thermal plasma simulation.

Plastic aging can cause alterations in the physical and chemical characteristics of plastics, as well as their behavior in the environment. Due to the extremely slow natural aging process, laboratory simulated aging methods have to be used. In this study, non-thermal plasma (NTP) was adopted to investigate the aging process of polypropylene (PP) and polyethylene terephthalate (PET) microplastics. Various analytical instruments, including proton transfer reaction mass spectrometry and single-particle aerosol mass spectrometry, were employed to examine and identify the organic constituents of the gas, liquid, and particle phase degradation products, as well as to monitor the degradation process. The results showed that after 90min of aging, both PP and PET surfaces showed yellowing, and the carbonyl index of PP increased while that of PET decreased, with an increase in crystallinity. The organic components of reaction products, such as ketones, esters, acids, and alcohols, increased with longer aging times. Gas products mainly contain aromatic hydrocarbons, while particles from aged PET contain compounds with benzene rings and metal elements. Liquid products from aged PP show a significant presence of branched alkanes. Based on this analysis, degradation mechanisms of PP and PET by NTP were proposed. This investigation represents the initial systematically exploration of the release of organic substances during the degradation of microplastics mediated by NTP. It provides significant insights into the detrimental organic compounds emitted during this process, thereby offering valuable information for understanding the environmental and human health implications of natural microplastic degradation. Furthermore, it addressed the requirements for increased attention to the potential environmental risks associated with these harmful components.

Unveiling PET Hydrolase Surface Dynamics through Fluorescence Microscopy.

PET hydrolases are an emerging class of enzymes that are being heavily researched for their use in bioprocessing polyethylene terephthalate (PET). While work has been done in studying the binding of PET oligomers to the active site of these enzymes, the dynamics of PET hydrolases binding to a bulk PET surface is an unexplored area. Here, methods were developed for total internal reflection fluorescence (TIRF) microscopy and fluorescence recovery after photobleaching (FRAP) microscopy to study the adsorption and desorption dynamics of these proteins onto a PET surface. TIRF microscopy was employed to measure both on and off rates of two of the most commonly studied PET hydrolases, PHL7 and LCC, on a PET surface. It was found that these proteins have a much slower off rates on the order of 10-3 s-1 , comparable to non-productive binding in enzymes such as cellulose. In combination with FRAP microscopy, a dynamic model is proposed in which adsorption and desorption dominates over lateral diffusion over the surface. The results of this study could have implications for the future engineering of PET hydrolases, either to target them to a PET surface or to modulate interaction with their substrate.

Modification of AgNP-Decorated PET: A Promising Strategy for Preparation of AgNP-Filled Nuclear Pores in Polymer Membranes.

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties.

THE EFFECT OF THE FLUORINE CONCENTRATION IN A PLASMA-FORMING GAS MIXTURE ON THE CHEMICAL COMPOSITION, SURFACE CHARGE, AND RELIEF PARAMETERS OF FLUOROCARBON COATINGS ON PET

In this work, the main factors influencing the appearance of the antiadhesive properties on the surface of polyethylene terephthalate (PET) with a fluorocarbon film were considered. The chemical composition, surface charge, and surface relief of antimicrobial fluorocarbon films deposited on PET were studied. The fluorocarbon films were formed by ion-plasma technology at reduced pressure using a two-component gas mixture consisting of tetrafluoromethane and cyclohexane.

Enhancement of hydrophilicity and color strength in plasma treated PET with water vapor post-exposure using a new in-line pilot scale DBD plasma

Due to its low hydrophilicity, direct sublimation inkjet printing on woven polyester fabric surfaces is challenging. This research experimentally studies the efficacy of dielectric barrier discharge (DBD) roll-to-roll plasma treatment with or without water vapor post-exposure as a novel method to modify polyethylene terephthalate (PET) surfaces to enhance hydrophilicity, color performance, and printing quality. The Response Surface Methodology (RSM) was used to design experiments, and the optimum conditions were analyzed through statistical calculations. Their results were examined using Optical Emission Spectroscopy (OES), Atomic Force Microscopy (AFM), field emission scanning electron microscopy (FESEM), Energy Dispersive X-ray (EDX), X-ray Photoelectron Spectroscopy (XPS), and Attenuated Total Reflectance Fourier Transform Infra-Red spectroscopy (ATR-FTIR) tests. Qualitative and quantitative tests for color performance and wicking test used for hydrophilicity assessment confirms the effectiveness of this Green inline pretreatment for industries to enhance direct sublimation inkjet printing quality on PET by a decrease in absorption time from 12051 to 202 s and an increase in the color depth to 12.49%, 25.89 and 18.07% for Cyan, Magenta and Key (black) respectively. One of the stable optimum conditions in which three printed colors: Cyan, Magenta, and Black (Key), show high-quality color performance is at 15 processing rounds, 2 m/min velocity in the absence or presence of water vapor post-exposure. Water vapor post-exposure exhibits a beneficial, economic effect along with plasma treatment. The results show that the chemical modification aspect of this treatment plays a more significant role in printing quality enhancement than its morphological modification.

Highly Efficient and Reliable Organic Light–Emitting Diodes Enabled by a Multifunctional Hazy Substrate for Extreme Environments

AbstractAs transparent, flexible, and wearable organic electronics degrade under normal outdoor environmental conditions (e.g., water vapor, oxygen, and UV light) and extreme environments, including washing or rain, a customized encapsulation technology is required to improve device reliability. Herein, a simple process is presented for fabricating multifunctional hazy substrates (MFHSs) with excellent gas diffusion barrier (GDB), flexibility, UV reflectance, light scattering, and waterproof properties. First, a spiky polyethylene terephthalate (PET) surface is produced with 76.0% optical haze through ion‐beam treatment followed by the formation of a hydrophobic layer to achieve a waterproof effect (contact angle: 153.3°). Then, a multifunctional multibarrier film is fabricated based on a nano‐laminated distributed Bragg reflector and functional polymer on the functional PET substrate to serve as a GDB and UV filter. This multibarrier film has excellent mechanical and chemical stabilities, in addition to having a water vapor transmission rate of 10−6 g m−2 day−1 and UV transmittance of <3%. The so‐fabricated MFHS not only increases the device efficiency by 73% but also enables a highly flexible and environmentally stable organic light–emitting diode. The surface treatment and encapsulation technologies developed in this study are expected to increase the lifetime of organic devices and facilitate high outdoor usability.

Supercritical CO2 Assisted Ni-P Electroless Plating of PET Components with Complex 3D Structures

There is an increasing demand of methodologies to metallize complex polymer materials for application in electronics such as wearable devices and robotic products. In various metallization methods, electroless plating is a powerful and promising approach to meet this demand. The present conventional electroless plating requires pretreatment steps to deposit catalyst onto surfaces of polymer materials, which results in damages to their surfaces and also deformation of their shape because of the usage of strong acidic solvents. Furthermore, the adhesion strength between the polymer material and the metal layer is insufficient. To overcome these problems, a catalyzation step using supercritical carbon dioxide (sc-CO2) as the solvent is proposed.[1] The sc-CO2-assisted catalyzation enables a deep impregnation of catalysts into the polymer material without the pretreatment step, and this enhances the adhesive properties of the deposited metal on the polymer. By the sc-CO2-assisted catalyzation, electroless Ni-P plating of polyethylene terephthalate (PET) is realized. [1] Metallization of polymer materials with complex 3D structures is a more attractive topic, but it is widely accepted to be more difficult than film structures. Also, application the electroless plating via sc-CO2-asssited catalyzation to 3D-structured polymer materials remains unexplored. In this presentation, we report Ni-P plating of PET samples having complex 3D structures by the sc-CO2-assisited catalyzation process.A PET based material with a concavo-convex structure was designed and fabricated by the processing machine as shown in Figs. 1(a)–(b). Sc-CO2-assisted catalyzation process was performed in a high pressure reactor[1] containing palladium (II) hexafluoroacetylacetonate (Pd(C5HF6O2)2) as the palladium catalyst source at 70 °C under 15 MPa for 2 h. After the catalyzation process, the reactor was cooled to room temperature while maintaining the pressure in the reactor, and then the pressure in the reactor was reduced to atmospheric pressure. The collected PET sample from the reactor was kept under ambient atmosphere for two weeks, and then it was subjected to electroless Ni-P plating at 70 ℃ for 10 min.Fig. 1(c) shows the PET sample obtained after the sc-CO2-assisted catalyzation process followed by the post-treatment process. The volume of the catalyzed PET sample was scarcely changed. On the other hand, the post-treatment processes performed under the different conditions were found to cause undesired swelling and white turbidity of the PET sample, presumably because of microbubbles derived from residual CO2 in the PET. Fig. 1(d) shows an image of Ni-P successfully metallized on the PET surface. The electrical resistance of the Ni-P/PET material was 8.7 Ω, which is acceptable for electronic device applications. From these results, we concluded that sc-CO2-assisted catalyzation is applicable to metallization of PET materials with complex 3D structures. Reference [1] P.-W. Cheng, C.-Y. Chen, T. Ichibayashi, T.-F.M. Chang, M. Sone, S. Nishimura, J. Supercrit. Fluids 180 (2022) 105455. Figure 1

Sulfation of furcellaran and its effect on hemocompatibility in vitro

In this study, furcellaran (FUR) obtained from Furcellaria lumbricalis was firstly employed for sulfation via various methods, including SO3-pyridine (SO3∙Py) complex in different aprotic solvents, chlorosulfonic acid and sulfuric acid with a “coupling” reagent N,N′-Dicyclohexylcarbodiimide. Structural characterization through FT-IR, GPC, XPS and elemental analyses confirmed the successful synthesis of 6-O-sulfated FUR derivates characterized by varying degrees of sulfation (DS) ranging from 0.15 to 0.91 and molecular weight (Mw) spanning from12.5 kDa to 2.7 kDa. In vitro clotting assays, partial thromboplastin time (aPTT), thrombin time (TT), and prothrombin time (PT) underscored the essential role of sulfate esters in conferring anticoagulant activity whereas FUR prepared via chlorosulfonic acid with DS of 0.91 reached 311.4 s in aPPT showing almost 4-fold higher anticoagulant activity than native FUR at the concentration 2 mg/mL. MTT test showed all tested samples decreased cell viability in a dose dependent manner while all of them are non-cytotoxic up to the concentration of 0.1 mg/mL. Furthermore, sulfated derivates deposited onto polyethylene terephthalate surface presented substantial decrease in platelet adhesion, as well as absence of the most activated platelet stages. These findings support the pivotal role of O-6 FUR sulfates in enhancing hemocompatibility and provide valuable insights for a comparative assessment of effective sulfating approaches.

Interfacial mechanical properties of graphene on randomly rough PET substrate surface: A molecular dynamics study

In this work, molecular dynamics (MD) simulations are performed to create a series of polyethylene terephthalate (PET) substrates with random roughness, and the morphological characteristics and interfacial bonding of graphene on the real rough PET surface are first simulated. The results show that the interfacial mechanical behavior of graphene freely adhered to the PET roughness is influenced by the surface profile. Besides causing the non-conformal contact, the rough surface hinders the propagation of bending waves from the graphene corner regions during the adhesion and weakens their overlap. The increased surface roughness weakens interfacial adhesion and inhibits interfacial sliding, leading to the formation of larger morphological defects such as wrinkles. Furthermore, the measurement of the interfacial adhesion energy of graphene/PET substrate is achieved by the shaft loaded blister test (SLBT), which for the first time is used to simulate the interfacial debonding of graphene on rough PET surfaces. For low surface roughness, interfacial adhesion dominates the debonding behavior and the blister boundary preferentially extends along the interfacial defect area. For high surface roughness, the increasingly serious non-conformal contact makes the blister more likely to instability and enter the stage where normal and shear interactions are coupled.

The enhancement of waste PET particles enzymatic degradation with a rotating packed bed reactor

Polyethylene terephthalate (PET) is widely used, and biodegradation of waste PET results in a residue-free process, generating recyclable products, thereby contributing to the advancement of a more recyclable plastics lifecycle. Extensive research has been conducted on the modification and evolution of enzyme for PET degradation. As a solid-liquid heterogeneous reactions of PET degradation, the slow diffusion rate of the enzyme from liquid to solid PET surface leading to a slow reaction rate. Enhancement of mass transfer would accelerate PET degradation. Rotating packed bed (RPB) is a mass transfer enhancement reactor, but shear strength generated by the enzyme molecule knocking on rotator of RPB leads to enzyme denaturation. To address this issue, shear strength resistance agents were introduced in this study. With the protection of β-cyclodextrin combined with kieselguhr, PET particle degradation rate of 95% was achieved under the optimum conditions in 24 h, which was improved by 30% compared to that in stirred tank reactor. The results of this work demonstrated that the mass transfer greatly influenced the PET biodegradation process. RPB combined with the function of shear strength resistance agents could greatly improve the efficiency of the biodegradation process. This study provides a reference for the scaling up of PET degradation, and holds significant promise in the broader context of combatting plastic pollution challenges and advancing sustainable solutions for plastic waste.

On the Effect of Non-Thermal Atmospheric Pressure Plasma Treatment on the Properties of PET Film.

The aim of the work was to investigate the effect of non-thermal plasma treatment of an ultra-thin polyethylene terephthalate (PET) film on changes in its physicochemical properties and biodegradability. Plasma treatment using a dielectric barrier discharge plasma reactor was carried out in air at room temperature and atmospheric pressure twice for 5 and 15 min, respectively. It has been shown that pre-treatment of the PET surface with non-thermal atmospheric plasma leads to changes in the physicochemical properties of this polymer. After plasma modification, the films showed a more developed surface compared to the control samples, which may be related to the surface etching and oxidation processes. After a 5-min plasma exposure, PET films were characterized by the highest wettability, i.e., the contact angle decreased by more than twice compared to the untreated samples. The differential scanning calorimetry analysis revealed the influence of plasma pretreatment on crystallinity content and the melt crystallization behavior of PET after soil degradation. The main novelty of the work is the fact that the combined action of two factors (i.e., physical and biological) led to a reduction in the content of the crystalline phase in the tested polymeric material.

Solvent‐Free Depolymerization of Plastic Waste Enabled by Plastic‐Catalyst Interfacial Engineering

AbstractDepolymerization of condensation polymers by chemolysis often suffers from the large usage of solvents and homogeneous catalysts such as acids, bases, and metal salts. The catalytic efficiency of heterogeneous catalysts is largely constrained by the poor interfacial contact between solid catalysts and solid plastics below melting points. We report here our discovery of autogenous heterogeneous catalyst layer on polyethylene terephthalate surfaces during the generally believed homogeneous catalytic depolymerization process. Inspired by the “contact mass” concept in industrial chlorosilane production, we further demonstrate that the construction of plastic‐catalyst solid‐solid interfaces enables solvent‐free depolymerization of polyethylene terephthalate by vapor phase methanolysis at relatively low temperatures. Trace amounts of earth‐abundant element (zinc) introduced by electrostatic adsorption is sufficient for catalyzing the depolymerization. The concept of plastic‐catalyst contact mass interfacial catalysis might inspire new pathways for tackling plastic waste problems.

Solvent-Free Depolymerization of Plastic Waste Enabled by Plastic-Catalyst Interfacial Engineering.

Depolymerization of condensation polymers by chemolysis often suffers from the large usage of solvents and homogeneous catalysts such as acids, bases, and metal salts. The catalytic efficiency of heterogeneous catalysts is largely constrained by the poor interfacial contact between solid catalysts and solid plastics below melting points. We report here our discovery of autogenous heterogeneous catalyst layer on polyethylene terephthalate surfaces during the generally believed homogeneous catalytic depolymerization process. Inspired by the "contact mass" concept in industrial chlorosilane production, we further demonstrate that the construction of plastic-catalyst solid-solid interfaces enables solvent-free depolymerization of polyethylene terephthalate by vapor phase methanolysis at relatively low temperatures. Trace amounts of earth-abundant element (zinc) introduced by electrostatic adsorption is sufficient for catalyzing the depolymerization. The concept of plastic-catalyst contact mass interfacial catalysis might inspire new pathways for tackling plastic waste problems.

Enzymatic Degradation of PET plastic

Polyethylene terephthalate (PET) plastic is one of the most commonly used polymers worldwide and found in high rates as environmental waste. Previous studies have shown that the degradation of plastics using commercial grade enzymes is possible and highly effective in lab settings. However, the effectiveness and rates of enzymatic plastic degradation at environmentally relevant conditions is less known. In this study, we set up a series of sacrificial incubation experiments using a commercial enzyme, Humicola insolens cutinase (HiC), to examine the effect of various environmental variables, including temperature, pH, and salinity, on the hydrolytic degradation of PET. This was performed by measuring the mass loss at different time points during degradation, dissolved organic carbon produced in solution by PET hydrolysis, the Fourier transform infrared (FTIR) spectra of the PET surfaces, and scanning electron microscope (SEM) images of the PET surfaces. The results indicate that the degradation rate is 15-times faster at 55 °C than at 40 °C at pH 8 (1.93 mg day-1 versus 0.13 mg day-1), giving an initial estimate for the activation energy of PET hydrolysis of 2.2 kJ mol-1. In the 55 °C experiment which ran for 10 days, there was a noticeable decrease in the plastic strength and deformation of the plastic after 1 week of degradation. In the 40 °C experiment (duration 16 weeks), FTIR spectral changes were observed as early as week 6, with peaks of interest at 2,970 cm-1, 2,350 cm-1, 1,240 cm-1 , and between 1,300-1,000 cm-1. Ongoing experiments with pH and salinity will provide insight into their effects on the PET degradation rate. Altogether, these results will provide a comprehensive framework for predicting PET degradation rates, and by extension, other plastics that are degraded by hydrolysis, at environmentally relevant pH, temperature, and salinity conditions. In addition, these results provide insight into the effect of degradation on the chemical spectra of plastics and microplastics.

The growth mechanisms of TiO2 film onto PET surfaces by atomic layer deposition

Atomic layer deposition (ALD) was used to coat a polyethylene terephthalate (PET) polymer substrate with TiO2 film. The TiO2 was grown onto the surface with better film coverage by using thicker ALD deposition. Further evaluation on the coated substrates indicated that the reactive sites of –C=O that existed on PET surface played a significant contribution to facilitating the initial ALD growth of the TiO2 thin film. The chemical composition of the coated substrates was characterised using energy dispersive X-ray spectroscopy, which showed that increasing the TiO2 film thickness increased the Ti element content. Two growth mechanisms, namely, diffusion growth and direct coordination through the precursor coordination with surface reactive sites of –C=O with product release occurred simultaneously in the initial growth of TiO2 coating onto PET polymer by ALD. The surface alteration of the coated ALD was characterised by Fourier transform infrared spectroscopy, which showed that the hydroxyl –OH groups emerged in the TiO2 ALD film.

Synergistic interlaminar strengthening of unidirectional carbon fiber-reinforced composites using carbon nanofiber-modified sizing on the surface of PET interleaves

A unidirectional carbon fiber-reinforced composite with excellent interlaminar fracture toughness (ILFT) was fabricated, analyzed, and evaluated. The composites were formed by inserting polyethylene-terephthalate (PET)-based thermoplastic veils between prepregs to enhance the ILFT. Carbon nanofiber (CNF)-modified coupling agents were spray-deposited onto the PET veil surface to minimize the reductions in the tensile strength and modulus of the composites caused by the use of thermoplastic veils and maximize the enhancements in the ILFT. The microfibers of the PET veils endowed the composites with delamination resistance, whereas the coupling agents and CNFs coated on the PET surface induced chemical bonding and mechanical interlocking with the epoxy matrix, respectively. Therefore, multiscale reinforcement mechanisms, including these mechanical and chemical interactions, generated a synergistic effect on the mechanical properties of the composites. Reductions in the tensile strength and modulus of the composites decreased by up to 104.7% and 100.8%, respectively, following the application of the CNF/coupling agent-modified PET interleaves, and their Mode-Ⅰ and Mode-Ⅱ ILFT values increased by up to 105.3% and 610.9%, respectively, compared with those of neat composites.