Thin Plastic Film Research Articles

An Innovative Approach to Closing the Loop in a Circular Plastic Economy by Upcycling Single-Use Post-consumer Thin Film Plastic Packaging Waste into Durable Plastic Products

AbstractThe waste system requires a circular economy business solution to upcycle millions of tonnes of contaminated post-consumer single-use multi-material, multilayer, plastic packaging films/foils. This waste is rarely collected for recycling, firstly because the market for such waste is new and very small, and secondly due to technical issues and cross-contamination at waste recycling facilities. Conventionally, two linear disposal routs exist, energy recovery through incineration or landfill, both having an economic cost. Being very lightweight, plastics are blown around and end up contaminating terrestrial and marine environments. This paper evaluates intrusion extrusion moulding technology with agglomeration to make products. With a 50-year first lifespan and nine more life cycles, they can be used multiple times as a substitute for wood and concrete. Public bodies can catalyse the intrusion extrusion moulding manufacturing industry by including such products during their procurement processes. The technology works and the business can be profitable.

Properties of poly(butylene adipate-co-terephthalate)/thermoplastic starch filled with treated and untreated sugarcane bagasse fiber

Sugarcane bagasse, comprising fibrous rind and spongy pith, is frequently employed as a reinforcing agent in both concrete and plastic composites. In thin plastic films, sugarcane bagasse is typically utilized as finely ground particles within the composite film. The integration of this agricultural byproduct into biodegradable plastic films could potentially lower production expenses and promote the film's biodegradability. This study presents the development of poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch (TPS) (90/10) formulations incorporating varying loadings of sugarcane bagasse fibers. The impact of alkaline and silane surface treatments on tensile strength, thermal properties, and water barrier properties was investigated. Upon the inclusion of sugarcane bagasse (5%, 10%, 15%, and 20%), a decrease in tensile strength from 23.47 to 8.41 MPa and elongation at break from 1135% to 55.83% was observed. Conversely, the Young's modulus increased from 47.12 to 188.50 MPa following the addition of 20% sugarcane bagasse in the PBAT/TPS matrix. Modest enhancements in tensile properties, thermal characteristics, and water barrier properties were noted after treating the bagasse fibers with alkaline and silane. Scanning Electron Microscope (SEM) analysis revealed that silane-treated sugarcane bagasse exhibited increased surface roughness due to the removal of lignin and hemicellulose, facilitating better adhesion between the fibers and the PBAT/TPS matrix.

Linear and nonlinear stretching sheet for enhanced heat and mass transfer in Casson nanofluid with activation energy

In this study, we delve into the magnetohydrodynamic heat and mass transfer flow of a Casson nanofluid over specifically chosen linear and nonlinear stretching surfaces embedded in a porous medium to understand their distinct effects on fluid behavior. By focusing on the influences of Brownian motion, thermophoresis, thermal radiation, and chemical reactions, we transformed nonlinear partial differential equations into ordinary differential equations, leveraging the Runge-Kutta method and Shooting Techniques for numerical solutions of momentum, temperature, and concentration profiles under predetermined boundary conditions. Our results, depicted in both graphical and tabular forms, shed light on how various parameters, including the Casson fluid characteristics, magnetic fields, buoyancy ratio, and mixed convection effects, influence fluid dynamics. A notable finding is that an increase in the Brownian motion parameter intensifies the fluid velocity and temperature profiles, but reduces its concentration profile, unveiling complex interactions within the nanofluid dynamics. This investigation underscores the importance of linear and nonlinear stretching surfaces in mimicking practical industrial scenarios, thereby providing insights that are crucial for optimizing processes such as coating, cooling of electronic devices, and in the manufacturing of thin plastic films, where precise control over heat and mass transfer is essential.

Thin, disposable, antibacterial, heat-pressed photocatalytic plastic films

The production of several different thin, highly flexible, disposable, antibacterial, photocatalytic plastic films is described. A thin layer of a semiconductor photocatalyst, SC, powder is partially embedded in a thin (ca. 30 μm), highly flexible film of low-density polyethylene, LDPE, by heat-pressing the two together. The resulting SC/LDPE film is then tested for photocatalytic activity, via the photo-oxidised bleaching of methylene blue, MB, and photocatalysed antibacterial activity, via its inactivation of Escherichia coli, E. coli. The SCs tested include, P25 TiO2, high surface area Tronox rutile TiO2, low surface area rutile TiO2, ZnO and WO3. The MB test results reveal photocatalytic activities of the SC/LDPE films are, P25 TiO2 > ZnO > rutile TiO2 ≈ Tronox rutile TiO2 > WO3, which suggest the kinetics depend largely on the redox potential of the photogenerated conductance band electrons. In contrast, the E. coli deactivation results show that the order of activities of the SC/LDPE films, in the dark and (with an increased rate) upon illumination, are, Tronox rutile TiO2 > P25 TiO2 > ZnO > WO3 > rutile TiO2, which is similar to the variation in roughness factor, Rf. It appears that rough films are better at deactivating E. coli, not only under illumination, via both a photocatalytic and thermal mechanism, but also in the dark, via a ‘bed-of-nails’/shear stress physical mechanism. Encouragingly, in most cases, the photocatalysed antibacterial activity exhibited by the SC/LDPE films is not much (ca. 74 %) lower when a cool white fluorescent rather than UVA lamp is used (UVA irradiance = 47 μW/cm2 and 1.5 mW/cm2, respectively). The Tronox rutile TiO2 film was also found to be effective in deactivating another Gram-negative bacterium and, to a lesser extent, two Gram-positive bacterial species. The potential of these thin plastic films with a notable antibacterial activity under room light and in the dark is discussed briefly.

Non-Destructive Thin Film Thickness Measurement based on Coplanar Capacitive Sensor and Printed Circuit Board Platform

This paper presents a compact design of a coplanar capacitive sensor based on a printed circuit board (PCB) to apply in non-contact and non-destructive thin film thickness measurement. The capacitive sensor design is structured by two coplanar capacitors, including a reference coplanar capacitor and a sensing coplanar capacitor. Using this structure, the thin film thickness could be estimated through the imbalance voltage produced between the two signals from the reference capacitor and sensing capacitor. The size of the proposed sensor is 9.99 × 9.99 mm and the capacitor electrodes structured by shapes of spiral, interdigital, and round are studied and optimized. Those electrode structures have been modelled and simulated and the simulation results reveal that the spiral structure gives the best performance. The experiment was conducted using plastic thin films with thickness ranging from 10 to 230 µm and dielectric constants ranging from 1.375 to 3.19 to investigate the working principle of the sensor. Experiment results show the approximate linearity of the output voltage corresponding to the various thickness at measurement range from 0 to 90 µm. The sensitivity of the sensor is 13.5 and 29 mV/µm corresponding to the 1.375 and 3.19 dielectric constants of the thin films, respectively. The proposed coplanar capacitive sensor is fabricated based on the PCB platform and shows good performance with a minimum cost. The experiment results demonstrate that this sensor has a high potential to be applied in several biomedical and industrial thin film thickness measurement applications.

Ultra-Large Compressive Plasticity of E-Ga2O3 Thin Films at the Submicron Scale.

Gallium oxide (Ga2O3) usually fractures in the brittle form, and achieving large plastic deformability to avoid catastrophic failure is in high demand. Here, ε-Ga2O3 thin films with columnar crystals and partial unoccupied Ga sites are synthesized, and it is demonstrated that the ε-Ga2O3 at the submicron scale can be compressed to an ultra-large plastic strain of 48.5% without cracking. The compressive behavior and related mechanisms are investigated by in situ transmission electron microscope nanomechanical testing combined with atomic-resolution characterizations. The serrated plastic flow and large strain burst are two major deformation forms of ε-Ga2O3 during compression, which are attributed to the dislocation nucleation and avalanches, formation of new grains, and amorphization. The ultra-large compressive plasticity of ε-Ga2O3 thin films at the submicron scale can inspire new applications of Ga2O3 in micro- or nano- electronic and optoelectronic devices, especially those that require impact resistance during processing or service.

(Invited) Exploitation of Electron Transfer Reactions for Latent Fingerprint Visualization: Fundamental Concepts and Technology Transfer

A fingerprint is a unique time-invariant attribute of an individual and is the most frequent physical evidence used to identify a suspect in a criminal investigation. An image of the fingerprint left on a surface by the transfer of material between the fingertip and the surface can establish contact between the individual and an object (e.g. weapon) or a fixed location (crime scene). In practice, most marks are so-called latent (non-visible) fingermarks that require chemical treatment to generate a visible image. This presentation describes the contribution of electron transfer reactions (redox processes) to this endeavor and reveals the variety of reaction type, reagent materials, and substrate surfaces.The key to a successful fingermark reagent is the facility to deliver it with high spatial selectivity to either the deposited residue (representing ridges on the finger) or the bare substrate (representing furrows on the finger), such that there is visual contrast between the ridge and furrow areas. The lateral (horizontal) patterning of so-called second level features (such as ridge endings, crossovers and bifurcations) is the basis of the identification. Superficially, the distance scale is macroscopic (ridge width ca. 100 mm), but the aspiration of a suitably sharp image involves so-called third level detail at the mesoscopic level (ridge edge shape resolution ca. 1 mm). However, this lateral image quality requires vertical control of reagent deposition at the nanoscale. Here we explore how latent fingermark visualization can be accomplished by controlled molecular mechanisms involving metallic and polymeric materials.Two established (but previously poorly mechanistically understood) metal deposition processes are physical developer (PD) and multi-metal deposition (MMD). PD involves redox generation of silver nanoparticles that deposit selectively on fingermark residue on paper substrates (e.g., documents, correspondence, paper currency). We show how mechanistic understanding [1] of a recent PD re-formulation [2] has been used to overcome the environmental outlawing of a critical surfactant in the classical process, revealing latent marks up to a century after deposition. MMD is a more sophisticated variant, in which gold nanoparticles are pre-deposited on the residue and act as nucleation sites for silver deposition to reveal marks on thin plastic films (e.g., drugs and explosives wrappings). We show how the kinetics of redox-driven silver deposition on ridge vs furrow regions define image contrast.In a complementary strategy, we use the fingerprint residue as a template (“mask”) to direct electrochemically generated reagent to the bare surface between the deposited ridges, creating a negative image of the fingerprint. When the surface is a reactive metal (Cu or Fe), a more noble metal (Ag) can oxidize exposed substrate atoms. The electron transfer process results in solution oxidant (here, Ag) being reduced to elemental metal that deposits on the surface and dissolution of an equivalent amount of substrate. Complexing agents influence both reaction thermodynamics and kinetics. Optical and SEM imaging and EDAX surface analysis reveal high quality images with clear third level detail.When the surface is an inert metal, exemplified by stainless steel (forensically relevant to knife crime), the above galvanic exchange cannot take place. In this instance, electrochemically driven oxidation of aromatic monomers creates negative images of latent marks via polyaniline [3], PEDOT [4] or poly(pyrrole-co-EDOT) [5] films. We show how these electrochromic systems offer the prospect of optimization of visual contrast via light absorption. More recently, we have explored the prospect of incorporating fluorescent dyes (Methyl Red, Methyl Orange, Indigo Carmine, Basic Yellow 40) in the polymer films, using functionalization, ion-exchange and physical encapsulation strategies [6].We discuss the practicalities and prospects for technology transfer of these approaches to the practitioner environment; even for the nominally established PD and MMD processes, this is not trivial. Positive outcomes lie at the core of collaborative expertise provided by practitioners, researchers, regulatory authorities and investigators. We discuss how this can be realized through engagement of these parties and researcher use of the image capture and enhancement technologies used by practitioners.

Abundance and composition of small floating plastics in the eastern and southern sectors of the Atlantic Ocean

We report the distribution of floating plastics in the eastern and southern sectors of the Atlantic Ocean based on 35 neuston net trawl samples collected during two research cruises in 2016 and 2017. Plastic particles (>200 μm) were found in 69% of net tows, with median densities of 1583 items·km−2 and 5.1 g·km−2. Most particles (80% of 158) were microplastics (<5 mm) of secondary origin (88%), followed by industrial pellets (5%), thin plastic films (4%) and lines/filaments (3%). Due to the large mesh size we used, textile fibers were not considered in this study. μFTIR analysis revealed that most particles found in the net were made of polyethylene (63%), followed by polypropylene (32%) and polystyrene (1%). A transect between 0 and 18°E along 35°S in the South Atlantic Ocean revealed higher densities farther west, supporting the accumulation of floating plastics in the South Atlantic gyre, mainly west of 10°E.

Plastic Pollution in Nigeria: The Need for Legislation to Tackle the Menace

Collection, disposal and management of plastic waste and polythene bags is a growing problem in Nigeria. The use of plastic/polythene bags made of thin plastic film has increased significantly in recent years. The manner of disposal of these items has resulted in the degradation of the natural environment. In Nigeria, lots of plastics are used on daily basis, of which most, if not all of them, are not properly disposed of. Some of these items end up in landfills, littering the environment, harming wildlife or blocking drainages, therefore, increasing the risk of flood. This paper examines the existing laws in relation to waste management in Nigeria and the inadequacies of the existing legislation in combating this phenomenon. The doctrinal method of research was used and it is recommended that there is a need for new legislation to be enacted for Nigeria to surmount the menace of plastic pollution.

An Innovative Approach to Closing the Loop in a Circular Plastics Economy by Upcycling Single Use Post Consumer Thin Film Plastic Packaging Waste into Durable Plastic Products

An Innovative Approach to Closing the Loop in a Circular Plastics Economy by Upcycling Single Use Post Consumer Thin Film Plastic Packaging Waste into Durable Plastic Products

Marine-Derived Actinomycetes: Biodegradation of Plastics and Formation of PHA Bioplastics-A Circular Bioeconomy Approach.

Plastics are present in the majority of daily-use products worldwide. Due to society's production and consumption patterns, plastics are accumulating in the environment, causing global pollution issues and intergenerational impacts. Our work aims to contribute to the development of solutions and sustainable methods to mitigate this pressing problem, focusing on the ability of marine-derived actinomycetes to accelerate plastics biodegradation and produce polyhydroxyalkanoates (PHAs), which are biodegradable bioplastics. The thin plastic films' biodegradation was monitored by weight loss, changes in the surface chemical structure (Infra-Red spectroscopy FTIR-ATR), and by mechanical properties (tensile strength tests). Thirty-six marine-derived actinomycete strains were screened for their plastic biodegradability potential. Among these, Streptomyces gougerotti, Micromonospora matsumotoense, and Nocardiopsis prasina revealed ability to degrade plastic films-low-density polyethylene (LDPE), polystyrene (PS) and polylactic acid (PLA) in varying conditions, namely upon the addition of yeast extract to the culture media and the use of UV pre-treated thin plastic films. Enhanced biodegradation by these bacteria was observed in both cases. S. gougerotti degraded 0.56% of LDPE films treated with UV radiation and 0.67% of PS films when inoculated with yeast extract. Additionally, N. prasina degraded 1.27% of PLA films when these were treated with UV radiation, and yeast extract was added to the culture medium. The main and most frequent differences observed in FTIR-ATR spectra during biodegradation occurred at 1740 cm-1, indicating the formation of carbonyl groups and an increase in the intensity of the bands, which indicates oxidation. Young Modulus decreased by 30% on average. In addition, S. gougerotti and M. matsumotoense, besides biodegrading conventional plastics (LDPE and PS), were also able to use these as a carbon source to produce degradable PHA bioplastics in a circular economy concept.

Mechanics of micropillar confined thin film plasticity

Micropillar compression experiments probing size effects in confined plasticity of metal thin films, including the indirect imposition of ‘canonical’ simple shearing boundary conditions, show dramatically different responses in compression and shear of the film. The Mesoscale Field Dislocation Mechanics (MFDM) model is confronted with this set of experimental observations and shown to be capable of modeling such behavior, without any ad-hoc modification to the basic structure of the theory (including boundary conditions), or the use of extra fitting parameters. This is a required theoretical advance in the current state-of-the art of strain gradient plasticity models. It is also shown that significantly different inhomogeneous fields can display qualitatively similar size effect trends in overall agreement with the experimental results. The (plastic) Swift and (elastic) Poynting finite deformation effects are also demonstrated.

Attosecond dispersion as a diagnostics tool for solid-density laser-generated plasmas

Extreme-ultraviolet pulses can propagate through ionised solid-density targets, unlike optical pulses and, thus, have the potential to probe the interior of such plasmas on sub-femtosecond timescales. We present a synthetic diagnostic method for solid-density laser-generated plasmas based on the dispersion of an extreme-ultraviolet attosecond probe pulse, in a pump–probe scheme. We demonstrate the theoretical feasibility of this approach through calculating the dispersion of an extreme-ultraviolet probe pulse propagating through a laser-generated plasma. The plasma dynamics is calculated using a particle-in-cell simulation, whereas the dispersion of the probe is calculated with an external pseudo-spectral wave solver, allowing for high accuracy when calculating the dispersion. The application of this method is illustrated on thin-film plastic and aluminium targets irradiated by a high-intensity pump pulse. By comparing the dispersion of the probe pulse at different delays relative to the pump pulse, it is possible to follow the evolution of the plasma as it disintegrates. The high-frequency end of the dispersion provides information on the line-integrated electron density, whereas lower frequencies are more affected by the highest density encountered along the path of the probe. In addition, the presence of thin-film interference could be used to study the evolution of the plasma surface.

High-performance solid-state metal-air batteries with an innovative dual-gel electrolyte

An innovative dual-gel electrolyte design is proposed in this work for solid-state metal-air batteries, which utilizes the acid-alkaline dual-gel for the Al-air and Zn-air batteries, and the acid-salt dual-gel for the Mg-air battery. During battery storage, a plastic thin-film can be used for dual-gel separation, which can be removed before battery usage. And during battery working, benefited from the higher ionic diffusion resistance of gel electrolytes, the mixing of different electrolytes is significantly reduced without using complex flowing system or expensive bipolar membrane separator, ensuring a pseudo-stable battery system. The acid-alkaline dual-gel Al-air and Zn-air batteries can provide ∼0.5 V higher voltage output than the corresponding alkaline single-gel batteries, and the discharge lifetime is not compromised too much due to the effective suppression of acid-alkaline neutralization. As for the acid-salt dual-gel Mg-air battery, attributed to the Mg(OH)2 dissolution by crossovered acid, both a 0.65 V higher discharge voltage and a 5.5 times longer discharge lifetime are achieved compared with the salt single-gel battery. By simulating the variation of ion concentration inside gels during battery discharge, it is found that the effective ion diffusivity in gel plays a vital role in the battery stability. In general, a moderate value is favored to avoid both the ion shortage at the electrode-electrolyte interface and the vigorous neutralization at the gel-gel contact surface. Furthermore, a flexible version of the dual-gel metal-air battery is demonstrated by using paper-based gel electrolytes.

Investigating Nanoscale Contact Using AFM-Based Indentation and Molecular Dynamics Simulations

In this work we study nanocontact plasticity in Au thin films using an atomic force microscope based indentation method with the goal of relating the changes in surface morphology to the dislocations created by deformation. This provides a rigorous test of our understanding of deformation and dislocation mechanisms in small volumes. A series of indentation experiments with increasing maximum load was performed. Distinct elastic and plastic regimes were identified in the force-displacement curves, and the corresponding residual imprints were measured. Transmission electron microscope based measured dislocation densities appear to be smaller than the densities expected from the measured residual indents. With the help of molecular dynamics simulations we show that dislocation nucleation and glide alone fail to explain the low dislocation density. Increasing the temperature of the simulations accelerates the rate of thermally activated processes and promotes motion and annihilation of dislocations under the indent while transferring material to the upper surface; dislocation density decreases in the plastic zone and material piles up around the indent. Finally, we discuss why a significant number of cross-slip events is expected beneath the indent under experimental conditions and the implications of this for work hardening during wear.

Simultaneous extraction of the elastic-plastic properties of a thin film and its substrate from an identifiability-based design of depth-sensing nanoindentation testing

This work presents an approach to simultaneously identify reliable elasto-plastic properties of a 100 nm amorphous alumina film and plastic properties of its silicon substrate by the Finite Element Model Updating (FEMU) method, using exclusively nanoindentation P−h curves. A 2D axisymmetric finite element model simulates the nanoindentation tests, and the Young's modulus E, the initial yield stress σy and the hardening modulus Hp of the thin film, as well as the yield stress of silicon σys are the parameters to identify. This work relies on a numerical design of experiments carried prior to the identification process. It uses the sensitivity of the nanoindentation force to a variation of the parameters to define an identifiability indicator (I-index) based on the conditioning of the inverse problem. It reflects the stability of the potential solution of the inverse problem. I-index minimisation below a certain value allows to ensure a reliable identification by designing the best combination of experiments in terms of relevant information. I-index analyses values demonstrate that combining Berkovich and cube corner nanoindentation tests at two different indentation depths brings sufficient information to well-conditioned the inverse problem. Indeed, the increased penetration and the varied indenter tip shape induce differentiating factors which activates the substrate effect, or anvil effect, and allow the dissociation of the thin film plasticity from that of the substrate, and thus its identification. The identification procedure of the four parameters carried out with the designed dual nanoindentation test from several starting points reveals that the FEMU method converged to a unique solution. Lastly, the identified parameters are validated by confronting experimental and numerical (i) P−h curves of a Berkovich test on a bulk silicon sample and (ii) residual topographies using a 3D FEM of a Berkovich test on the composite system thin film – substrate.

Strain ratio and thickness effects on plasticity and crack patterns of Nickel thin films

The influence of the strain ratio (equibiaxial or uniaxial) and the strain path (equibiaxial or sequenced uniaxial) on the cracking of metallic thin films is studied. We used 20, 100 and 600 nm Nickel films deposited onto flexible substrates, analysed with in-situ X-ray diffraction and digital image correlation, and post-mortem optical microscopy. It is shown that the thickness and the loading ratio effects are interweaved. In particular, 600 nm films show a small (1.9%) von Mises fracture strain and straight cracks when strained equibiaxially, but a larger (2.7%) fracture strain and more tortuous cracks when strained uniaxially. On the contrary, 20 and 100 nm thin films show different von Mises ultimate tensile strengths, though their von Mises fracture strain and theirs cracks tortuosity hardly depend on the test.

Numerical Investigation of Excitation of Various Lamb Waves Modes in Thin Plastic Films

Ultrasonic-guided waves are widely used for the non-destructive testing and material characterization of plates and thin films. In the case of thin plastic polyvinyl chloride (PVC), films up to 3.2 MHz with only two Lamb wave modes, antisymmetrical A0 and symmetrical S0, may propagate. At frequencies lower that 240 kHz, the velocity of the A0 mode becomes slower than the ultrasonic velocity in air which makes excitation and reception of such mode complicated. For excitation of both modes, we propose instead a single air-coupled ultrasonic transducer to use linear air-coupled arrays, which can be electronically readjusted to optimally excite and receive the A0 and S0 guided wave modes. The objective of this article was the numerical investigation of feasibility to excite different types of ultrasonic-guided waves, such as S0 and A0 modes in thin plastic films with the same electronically readjusted linear phased array. Three-dimensional and two-dimensional simulations of A0 and S0 Lamb wave modes using a single ultrasonic transducer and a linear phased array were performed. The obtained results clearly demonstrate feasibility to excite efficiently different guided wave modes in thin plastic films with readjusted phased array.

Mechanics of Micropillar Confined Thin Film Plasticity

Mechanics of Micropillar Confined Thin Film Plasticity

Simultaneous Measurement of Thickness and Elastic Properties of Thin Plastic Films by Means of Ultrasonic Guided Waves.

Ultrasonic guided waves are already used for material characterization. The advantage of these waves is that they propagate in the plane of a plate and their propagation characteristics are sensitive to properties of the material. The objective of this research was to develop an ultrasonic method that could be used to measure the properties of thin plastic polyvinylchloride films (PVC). The proposed method exploits two fundamental Lamb wave modes, A0 and S0, for measurement of a thin film thickness and Young’s modulus. The Young’s modulus is found from the measured phased velocity of the S0 mode and the film thickness from the velocities of both A0 and S0 modes. By using the proposed semi-contactless measurement algorithm, the Young’s modulus and thickness of different thickness (150 µm and 200 µm) PVC films were measured. The uncertainty of thickness measurements of the thinner 150 µm PVC film is 2% and the thicker 200 µm PVC film is 3.9%.