Thermoplastic Polymer Film Research Articles

Evaluation of Spatial Distribution of Crystallinity Induced by Local Heating Using Low-Frequency Raman Spectroscopy on Polyether Ether Ketone (PEEK)

Local heating was performed on a thermoplastic polymer film by contact with the tip of a soldering iron heated above the glass-transition temperature. The locally heated area was measured using microscopic Raman scattering spectroscopy, and the spatial distribution of the crystallinity was obtained from the low-frequency peak. The crystallinity distribution can be evaluated using the microscale spatial resolution. The temperature distribution around the locally heated area was calculated by applying the heat conduction equation, and good correspondence was obtained with the obtained crystallinity.

Dissipative Properties of Thermoplastic Polymer Films and Composite Materials Based on Poly(Butyl Methacrylate)

Dissipative Properties of Thermoplastic Polymer Films and Composite Materials Based on Poly(Butyl Methacrylate)

Nonlinear radiative oblique stagnation point flow of viscoelastic fluid due to stretching cylinder with polymer processing applications

The viscoelastic materials are a famous subclass of non-Newtonian fluids that present novel applications in various industrial processes. The most famous applications of viscoelastic fluid are observed in polymer processing. A major activity of the polymer processing industry is the production of thermoplastic polymer sheets and films. However, due to distinct rheology, a complete understanding of such materials is quite necessary for the polymer process. This continuation presents the rheological features of viscoelastic fluid with heat transfer phenomenon near the oblique stagnation point flow. The induced flow is accounted via stretched cylinder. The heat transfer analysis is also taken in the presence of non-linear heat flux. The problem is formulated using cylindrical coordinates in terms of non-linear coupled partial differential equations. Similarity transformation and normalized variables are used to convert the governing system into a set of ordinary differential equations. Due to the highly nonlinear model, the analytical solution of the system seems to be impossible therefore the approximate solution is obtained using the numerically stable and convergent finite difference method known as the Keller Box scheme. The simulated data via numerical algorithm is verified after comparing with already published investigations. The streamlines for the flow problem are presented.

Resonant vibration of a thin polymer film under optical excitation

We report on the mechanical excitation of a 220 μm thick thermoplastic film in its amorphous state by the radiation pressure of light. By modulating a low power visible laser (from 100 to 600 mW) at low frequencies (below 100 Hz), we observe a deformation of the film interfaces. The phenomenon, that is independent of the laser wavelength, is amplified at a resonant frequency and reaches 0.68 μm. The deformation is reversible and varies linearly with the optical power. Using the damped oscillator model, we show that the resonant frequency depends on the surface tension of the film. The associated free energy is then compared with the energy lost, taking into account the contribution of the damping corresponding to the imaginary part of the Young's modulus.

Sustainable Sandwich Composites Manufactured from Recycled Carbon Fibers, Flax Fibers/PP Skins, and Recycled PET Core

European union end of life vehicle directive mandates the use of more sustainable/recyclable materials in automotive industries. Thermoplastics matrix-based composites allow recyclability of composites at the end of life; however, their processing technology is more challenging than thermoset composites. Manufacturing process and mechanical testing of sustainable sandwich composite made from sustainable materials: flax, recycled carbon fiber, polypropylene, and recycled PET foam are presented in this article. High pressure compression molding with adhesive thermoplastic polymer film was used for manufacturing sandwich composite skin. The recycled PET foam core was integrated/joined with the skin using a thermoplastics adhesive film. A three-point bending test was conducted to compare the flexural properties. The results show that such sustainable sandwich composites will be an excellent material for truck side panel to operate in adverse wind/storm conditions. The sustainable sandwich composite can potentially be an excellent candidate for the fabrication of light-duty, lightweight, and low-cost engineering structures in automotive industry to meet the EU end of life requirements.

Fabrication of superhydrophobic surfaces on thermoplastic polymer films

Fabrication of superhydrophobic surfaces on thermoplastic polymer films

Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming.

Nanoimprint lithography (NIL) is a micro/nanoscale patterning technology on thermoplastic polymer films, and has been widely used to fabricate functional micro/nanoscale patterns. NIL was also used to develop micro/nanoscale patterns on curved surfaces by employing flexible polymer stamps or micropatterned metal molds with macroscopic curvatures. In this study, two-step ultrasonic forming was used to develop micropatterns on a curved surface out of a flat metal stamp, by connecting ultrasonic imprinting and stretching processes. Ultrasonic imprinting was used to replicate functional micropatterns on a flat polymer film, using a flat ultrasonic horn and micropatterned metal stamps with prism and dot micropatterns. An ultrasonic stretching process was then used to form a curvature on the patterned film using a curved ultrasonic horn and a soft mold insert, to avoid damage to the pre-developed micropatterns. The ultrasonic horn was designed to have three different tip radii, and the resulting forming depth and curvature formation were investigated experimentally. As a result, three different curved surfaces containing two different micropatterns were obtained. The developed curved films containing micropatterns were then evaluated optically, and showed different optical diffusion and illumination characteristics according to the film curvature and micropattern type. These results indicate that the proposed technology can extend the functionality of conventional micropatterned products by imposing appropriate curvatures.

Dissipative Properties of Polymer Films and Composite Materials Based on Polyvinyl Acetate

Commercial thermoplastic plasticized polymer films based on polyvinyl acetate of different chemical compositions and composite metal-viscoelastic polymer film-metal three-layer materials were studied by dynamic mechanical analysis. The dependences of the mechanical loss coefficient and elastic modulus of polymer films on temperature and strain frequency at dynamic extension were determined experimentally. The temperature intervals of efficient damping were determined. In these intervals, the mechanical loss coefficient of each polymer film exceeds 0.5 for the frequency range 1–10 000 Hz. The dissipative properties of polymer films and composite materials based on them were compared. The mechanical loss coefficients of the films materials are higher than those of the composite materials, but the composite materials have higher mechanical loss moduli. Their absolute values at the maximum-damping temperature reach ∼1011 Pa and more, which allows using them as effective vibration-damping coatings.

Comparative study on low energy ion beam modification of thermoplastic polymers

ABSTRACTPolycarbonate (PC) and polyethylene terephthalate (PET) thermoplastic polymer films were irradiated by low energy ion beams such as 100 keV Hydrogen (H+) ions and 350 keV Nitrogen (N+) ions at varied fluence from 1 × 1013 ions/cm2 to 5 × 1014 ions/cm2. The depth profile concentration of ions was calculated using Stopping and Range of Ions in Matter (SRIM) software code. Fourier Transform Infrared (FTIR) technique shows decrement in the intensity of peaks and disappearance of peaks mainly related to carbonyl stretching at 1770 cm−1 and C–C stretching at 1500 cm−1. Scanning electron microscopy (SEM) of irradiated polymers showed the formation of pores. X-ray diffraction (XRD) analysis has showed decrease in the intensity indicating the decrease in crystallinity after irradiation. Mechanical studies revealed that the molecular weight and microhardness decrease with increase in ion fluence due to increase in chain scission. The contact angle increased with increase in ion fluence indicating the hydrophobic nature of polymer after irradiation. Antibiofilm activity test of irradiated films shows resistance to Salmonella typhi (S. typhi) pathogen responsible for typhoid. The study shows that Nitrogen ion induces more damage compared to Hydrogen ions and PC films get more modified than PET films.

Hierarchically Patterned Elastomeric and Thermoplastic Polymer Films through Nanoimprinting and Ultraviolet Light Exposure.

The surface relief structure of polymer films over large areas can be controlled by combining nanoscale imprinting and microscale ultraviolet–ozone (UVO) radiation, resulting in hierarchical structured surfaces. First, nanoscale patterns were formed by nanoimprinting elastomer [poly(dimethylsiloxane) (PDMS)] films with a pattern on a digital video disk. Micron-scale patterns were then superimposed on the nanoimprinted PDMS films by exposing them to ultraviolet radiation in oxygen (UVO) through a transmission electron microscopy grid mask having variable microscale patterning. UVO exposure leads to conversion and densification of PDMS to SiOx, leading to micron height relief features that follow a linear scaling relation with pattern dimension. Further, the pattern scopes are shown to collapse into a master curve by normalized feature values. Interestingly, these relief structures preserve the nanoscale features. In this paper, the influence of the self-limiting PDMS densification, wall stress at the boundary of micro-depression, and UVO exposure energy is studied in control of the micro-depression scale. This simple two-step imprinting process involving both nanoimprinting and UV radiation allows for facile fabrication of the dimension adjustable micro–nano hierarchically structures not only on elastomer films but also on thermoplastic polymer films. Coarse-grained molecular dynamics simulations were performed to correlate the surface tension and elastic properties of polymeric materials to the deformation of the pattern structure.

Fabrication of Fiber Reinforced Plastics by Ultrasonic Welding

Ultrasonic fabrication of fiber reinforced plastics made from thermoplastic polymer films and carbon or glass fibers enables cycle times of a few seconds and requires investment costs of only some 10,000 €. Besides this, the raw materials can be stored at room temperature. A fiber content of 33 vol % and a tensile strength of approximately 1.2 GPa have been achieved by ultrasonic welding of nine layers of foils from polyamide, each 100 µm in thickness, and eight layers of carbon fibers, each 100 µm in thickness, in between. Besides unidirectional carbon fiber reinforced polymer composite (CFRP) samples, multi-directional CFRP plates, 116 mm, 64 mm and 1.2 mm in length, width and thickness respectively, were fabricated by processing three layers of carbon fiber canvas, each 300 µm in thickness, and eight layers of polyamide foils, each 100 µm in thickness. Furthermore, both the discontinuous and the continuous ultrasonic fabrication processes are described and the results are presented in this paper. Large-scale production still needs to be demonstrated.

Large area thermal nanoimprint below the glass transition temperature via small amplitude oscillatory shear forming

Small amplitude oscillatory shear forming is a technique that improves the performance of nanoimprint lithography by amplifying shear flow in narrow, squeezed geometries created during melt molding or glass forming of supported polymer films. To date, the technique has only been demonstrated for single micrometer-scale contacts representative of single features on wafer-scale nanoimprint stamps. In this work, we demonstrate scaling up of small amplitude shear forming to realize micrometer and nanometer feature patterning of thermoplastic polymer films over macroscopic centimetre square areas at temperatures in the vicinity of, and below the glass transition. By the use of a small amplitude (typically 5–10% the smallest pattern feature dimension) lateral oscillatory shear strain at a 10kHz frequency superposed during the normal motion of a nanoimprint mold, we are able to achieve high fidelity pattern replication in PMMA at temperatures as low as 35°C below its glass transition temperature. We further show that the technique is effective to pattern both bulk polymer surfaces and supported thin films, with samples as thick as 50μm and as films as thin as 40nm being successfully patterned. We demonstrate enhanced pattern fidelity using line-pattern imprint molds of 4μm pitch and 35nm relief, as well as an assortment of other geometries. For 800nm PMMA films, a 40% reduction in the residual layer thickness at 100°C was achieved by the addition of shear strain. No feature distortion is observed due to the oscillatory motion of the mold. The technique is particularly advantageous for large scale features and cavities, as well as high aspect ratio geometries, as the high speed lateral motion of the mold features acts to cyclically pump material into areas where stresses generated by the normal motion of the mold will not suffice.

Inexpensive, rapid fabrication of polymer-film microfluidic autoregulatory valve for disposable microfluidics.

This work presents the fabrication of a microfluidic autoregulatory valve which is composed of several layers of thin polymer films (i.e., polyvinyl chloride (PVC), polyethylene terephthalate (PET) double-sided tape, and polydimethylsiloxane (PDMS)). Briefly, pulsed UV laser is employed to cut the microstructures of through grooves or holes in the thermoplastic polymer films, and then the polymer-film valves are precisely assembled through laminating the PDMS membranes to the thermoplastic polymer films through the roll-lamination method. The effective bonding between the PVC film and the PDMS membrane is realized using the planar seal method, and the valve is sandwiched and compressed by a home-made housing to achieve the good seal effect. Then, the flow performances of the prototype valve are examined, and constant flow autoregulation is realized under the static or dynamic test pressures. The long-term response of the valve is also studied and minimum flow-rate decrements are found over a long actuation time. The fabrication method proposed in this work is successful for the low-cost and fast prototyping of the polymer-film valve. We believe our method will also be broadly applicable for fabrication of other low-cost and disposable polymer-film microfluidic devices.

Facile Exfoliation and Noncovalent Superacid Functionalization of Boron Nitride Nanosheets and Their Use for Highly Thermally Conductive and Electrically Insulating Polymer Nanocomposites

There is an increasing demand for highly thermally conductive and electrically insulating polymer materials for next-generation electronic devices, power systems, and communication equipment. Boron nitride nanosheets (BNNSs) are insulating materials with extremely high thermal conductivity. However, BNNSs suffer from the lack of facile and low-cost methods for producing large volumes of BNNSs, and extremely low through-plane thermal conductivities of BNNS/polymer composites as compared to the in-plane thermal conductivities. Herein, highly soluble, noncovalently functionalized boron nitride nanosheets (NF-BNNSs) with chlorosulfonic acid (CSA) were prepared by extremely facile and low-cost direct exfoliation of hexagonal boron nitrides (h-BNs), and acted as excellent nanofillers for dramatically improving both in- and through-plane thermal conductivities of insulating polymers. CSA is a cheap and versatile superacid with a large production volume. CSA showed strong physical adsorption on h-BN surfaces, giving few-layered NF-BNNSs in high yields (up to ∼25%). The crystallinity of the NF-BNNS was perfectly maintained even after CSA treatment. The physical adsorption of CSAs imparted high solubility for BNNSs in various organic solvents, yielding NF-BNNS uniformly dispersed-thermoplastic polymer composite films through a simple wet-process using predispersed NF-BNNS solutions. Random dispersion of NF-BNNSs in thermoplastic polymer films dramatically enhanced both the in- and through-plane thermal conductivities (>10 W m-1 K-1). The through-plane thermal conductivity of the NF-BNNS/polybutylene terephthalate (PBT) composite films was much greater (up to 11.0 W m-1 K-1) than those previously reported for BNNS/thermoplastic polymer composites (≤2.6 W m-1 K-1). These results are also due to an increase of interactions between the BNNS and polymer matrices, caused by physical adsorption of CSAs on BNNS surfaces. Moreover, the volume resistivity of the NF-BNNS/PBT composite films was significantly improved compared with pristine PBT. The NF-BNNS/polymer composites are very promising as highly thermally conductive and electrically insulating materials in various applications.

High surface area thermoplastic polymer films fabricated by mechanical tearing using nano-porous silicon

Micro-textured polymer thin films were produced by injecting polyvinylidene fluoride-trifluoroethylene chlorofluoroethylene (P(VDF–TrFE–CFE) thermoplastic polymer into porous silica substrates and applying pressure and heat followed by delamination of the substrates. Mechanical pressure was necessary to cause impregnation of the porous silica with the molten polymer. Following cooling, the adhesion forces between the polymer and the porous silica were greater than the cohesion of the polymer, resulting in tearing and elongation of the plastic fibers upon separation of the chips. The high surface area resulting films, which possess electro active capabilities, can potentially be used for applications requiring high surface area electro active polymer.

Effects of thermal treatment on the tribological characteristics of thermoplastic polymer film

Friction tests were carried out using a microtribometer to investigate the effect of thermal treatment on microscale friction and wear between poly(methyl methacrylate) (PMMA) film and a fused silica lens. Two films were examined: one that was baked at 413 K for 2 min and one that was baked at 433 K for 24 h. The friction forces on the PMMA films were measured under atmospheric conditions as the temperature of the films was increased from 300 K to 443 K. The contact area between the films and the lens was also examined. As the temperature increased, the friction force increased for both films. The slope of the friction force with temperature and the contact area varied, depending on the state of the film surface; glassy, rubbery, and viscous flow states. The baking conditions also affected the slope, contact area, and wear generation. For temperatures at which the samples were in a glassy state, wear particles were not generated on the sample baked for 24 h. The results demonstrate that the tribological characteristics can be altered by the thermal treatment of the PMMA film as well as the temperature. When the film contains some residual solvent, the residual solvent in the PMMA film can diffuse to the PMMA surface due to heating and thus decrease the friction force under room-temperature conditions.

Characterization of adhesion property between fused silica and thermoplastic polymer film in thermal nanoimprint lithography using a novel pull-off test

A novel pull-off test that mimics the actual thermal NIL process was conducted to investigate the adhesion properties between a flat fused silica and thermoplastic polymer film used in thermal NIL process. The pull-off force was measured under various NIL conditions—such as use of various polymer materials, imprint pressures, and separation velocities—and the surfaces of the mold and polymer film were observed after the test. The anti-sticking layer (ASL) derived from (1H,1H,2H,2H-perfluorooctyl)trichlorosilane (F 13-OTS) was coated on the fused silica and its effects on the adhesion characteristics was also examined. In cases of the mold without ASL, the pull-off force varied significantly according to the process conditions and damage on the polymer film was observed in most of the tests. In cases of the mold coated with the ASL, on the other hands, the pull-off force was maintained at a lower level in the range of the imprint pressure from 2 to 10 MPa or separation velocity from 1 to 25 μm/s, and there was no damage to the polymer film due to adhesion.

Fast electrical response to volatile organic compounds of 2D Au nanoparticle layers embedded into polymers

The conductivity of polymer–metal nanocomposites close to the percolation threshold is very sensitive to changes in the metal nanoparticle distances. Here the technical feasibility of a novel type of easy to prepare polymer–metal nanocomposite sensor is explored, which shall be able to detect a unique signal for various volatile organic compounds (VOCs) exhibiting a fast and reversible response. The composite consists of a nearly 2-dimensional Au nanoparticle layer near the percolation threshold thermally embedded into a thermoplastic polymer film. The sensoric response is based on the swelling behavior of the polymeric matrix upon exposure to the organic vapor molecules. Different from conventional nanocomposite sensors that require long-range diffusion of the volatile compound into the bulk of the matrix, the electrical response here only requires the penetration of the VOC a few nanometer below the surface thus causing a rapid detection. The degree of swelling depends on the type of polymer and VOC used as well as on the vapor pressure of the VOC leading to a characteristic response of each polymer to a specific VOC. This enables a “fingerprint” detection of different VOCs by an array of different polymer nanocomposite combined into one sensoric device.

Dielectric behavior characterization of a fibrous‐ZnO/PVDF nanocomposite

AbstractThis study is focused on forming a fibrous‐zinc oxide/polyvinylidine fluoride (ZnO/PVDF) nanocomposite and characterizing its dielectric behavior. The nanocomposite is prepared in two steps. First, a network of nanoscale diameter ZnO fibers is produced by sintering electrospun PVA/Zinc Acetate fibers. Second, the ZnO fibrous nonwoven mat is sandwiched between two PVDF thermoplastic polymer films by hot‐press casting. Scanning electron microscope images of the nanocomposite show that hot‐press casting of the fibrous‐ZnO network breaks the network up into short fibers. The in‐plane distribution of the ZnO fillers (i.e., the short fibers) in the PVDF matrix appears to comply with that of the pristine ZnO fibers before hot‐pressing, indicating that the fillers remain well‐dispersed in the polymer matrix. To the authors' knowledge, the work reported herein is the first demonstration of the use of electrospinning to secure the dispersion and distribution of a network of inorganic fillers. Moreover, processing a fibrous‐ZnO/PVDF flexible composite as described in this report would facilitate material handling and enable dielectric property measurement, in contrast to that on a fibrous mat of pure ZnO. Because of the high surface area of the short ZnO fibers and their polycrystalline structure, interfacial polarization is pronounced in the nanocomposite film. The dielectric constant is enhanced significantly‐up to a factor of 10 at low frequencies compared to the dielectric constant of constituent materials (both bulk ZnO and PVDF), and up to a factor of two compared to a bulk‐ZnO/PVDF composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Self-modulating polymer resist patterns in pressure-assisted capillary force lithography

We present pressure-assisted capillary force lithography (CFL) to generate self-modulating polymer resist patterns without residual layers and film instability. The method utilizes roof collapse of a patterned, deformable poly(dimethyl siloxane) (PDMS) mold that is placed on a thermoplastic polymer film with a constant external pressure (∼4 bars) and the resulting shape-variable capillary filling of a polymer melt into the reduced void space. A constraint on the coated polymer layer thickness was derived in order to ensure that there is no residual layer left after patterning and at the same time that film stability is guaranteed without film dewetting within the cavity. In addition, the height of a polymer pattern at the center of the filled void was estimated as a function of initial polymer layer thickness based on the assumption of the hemispherical shape of a meniscus and full capillary rise, which agrees well with the experimental data.