Resin Film Research Articles

Effects of sandwiched film thickness and cutting tool water contact angle on the processing outcomes in nanoskiving of nanowires

To calculate the shear yield stress and effect of the gold film thickness on sandwich structures, a force transducer was used to measure cutting forces during nanoskiving, and an orthogonal cutting model, which considered liquid parameters, was used for analysis the slicing process. Sandwich structures with gold film thicknesses of 50 nm and 150 nm were prepared. The contact angles between the water surface in the trough and its edge line were 0° (horizontal) and 35° (protruding) during slicing. The cutting feed of the slab should be < 430 nm for sandwich structures with a 50-nm gold film thickness and < 344 nm for a 150-nm gold film thickness to ensure dimensional accuracy. The sandwich structure with a gold film had a higher shear yield stress than a pure epoxy structure. Increasing the thickness of the gold film and the contact angle with the water surface decreased the strength of the structure, thereby facilitating cutting. In accordance with a comparison of segmented cutting-force curves for the sandwich structure, this characteristic is a result of different adhesions between the resin and metal film. Thus, researchers should improve epoxy material preparation to reduce adhesion of the material and improve the stability of the slicing.

Improving water resistance and mechanical properties of waterborne acrylic resin modified by 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether

3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether (TMBPDGE) modified waterborne acrylic resin with excellent water resistance and mechanical properties was synthesized by a homogeneous solution polymerization. Infrared analysis revealed that TMBPDGE could successfully participate in the synthesis. On this basis, the experimental conditions such as polymerization method, solid content, monomer addition method and curing temperature are optimized by using the results of immersion test, contact angle, tensile strength, elongation at break and hardness determination. The optimal amount of TMBPDGE is investigated and the resin is further characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The experimental results show that when the amount of TMBPDGE is 10 wt%, the water resistance and mechanical properties of the resin are greatly enhanced, and the cured resin film modified by TMBPDGE can withstand the soaking in water for more than 35 days, while that of film without modification is only one day. The tensile strength can reach 9.12 MPa, which is 2.2 times than that of the film without modification. Based on the enhanced properties, the modified resin provides a great potential in the fields of wood coatings, which require good water resistance and mechanical properties.

Mitigating void growth in out-of-autoclave prepreg processing using a semi-permeable membrane to maintain resin pressure

In this work, we investigate the use of discontinuous resin films in prepregs (semipregs) combined with a semi-permeable (air-permeable, resin-impermeable) release film intended to allow through-thickness air evacuation while simultaneously restricting resin loss. In situ measurements of resin pressure were deployed to test the hypothesis that resin pressure was maintained during prepreg cure when using a semi-permeable release film. Concurrently, visualization of the tool-side surface during cure revealed efficient evacuation of entrapped air. Porosity in laminates formed at high temperatures when using resin-permeable consumables, but did not form when using resin-impermeable (semi-permeable) consumables. To confirm that the observed void growth behavior was due to a loss in resin pressure, experiments were conducted to measure resin pressure during cure with both resin-permeable and resin-impermeable (semi-permeable) consumables. In both cases, resin pressure peaked before decreasing, a finding attributed to resin flowing to fill dry regions in the fabric, present by design. The drop in resin pressure, however, was greater in magnitude and longer in duration when using resin-permeable edge and bag-side surface boundaries, indicating that the observed void growth at elevated temperature was caused by a loss in resin pressure. Use of a semi-permeable membrane was effective in retaining resin content and mitigating such porosity.

Enhancement of surface electrical performances of epoxy film by blending with fluorinated and crosslinking monomer

• Fluorinated monomers were synthesized through a facile method to prepare fluorinated epoxy films. • Effects of introducing –CF 3 groups on physicochemical characters of the films are studied. • Electrical strength of the fluorinated film was evidently enhanced. In order to introduce fluorine-containing functional groups into epoxy resins to stably enhance the surface electrical properties of thin films, the trifluoromethyl group containing diglycidyl ethers bisphenol A (F-DGEBA) monomer was prepared by a simple and environmentally friendly method. Further, the film was obtained by blending the prepared monomers with DGEBA in different proportions and curing at high temperature with methyl tetrahydrophthalic anhydride (MTHPA). The prepared films not only have improved hydrophobic properties, but also exhibit better surface electrical properties. With the increase of the content of F-DGEBA, the epoxy resin films have higher surface insulation strength and better potential decay performance, which is due to the existence of –CF 3 groups changing the distribution of deep and shallow traps. Compared with the non-fluorinated film, the flashover voltage of the fluorinated film with the best electrical properties is increased by 32.2%, and the potential decay rate is also much faster.

A maddock mixer design that mitigates gels in polyethylene resin film applications

Maddock mixers are ubiquitous in plastics processing for single-screw extruders and injection molding plasticators due to their low cost to build and their ability to provide a uniform level of dispersive mixing. If the mixer is designed properly, all entering solid polymer fragments and certain types of gels can be trapped and dispersed into the matrix resin. Many mixers that are used commercially, however, provide lower levels of dispersive stress mixing than required by the process and they can degrade polyethylene (PE) resins. This paper will describe the mechanisms that are occurring in a Maddock mixer and develop guidelines for obtaining optimal mixing stresses while mitigating resin degradation.

Vibro-acoustic characteristics of multifunctional carbon fiber reinforced panel

This paper deals with the assessment of vibro-acoustic properties of a multifunctional carbon fiber reinforced panel manufactured by bulk infusion, a modified resin film infusion process. The components of the epoxy resin were chosen to contrast the electrical insulating property and poor flame resistance of the epoxy resins impregnating carbon woven fabric. To confer electrical conductivity to the resin a percentage of 0.5 wt% of Multi-Wall Carbon Nanotubes (MWCNTs) was dispersed in the resin, whereas to increase flame resistance a percentage of 5 wt% of Glycidil Polyhedral Oligomeric Silsesquioxanes (GPOSS) was solubilized in the epoxy mixture. Furthermore, as hardener agents, a mixture of 4,4’-DiaminoDiphenyl Sulfone (DDS) (53.4 wt%) and Bis(3-Aminophenyl) Methyl Phosphine Oxide (BAMPO) (46.7 wt%) was used. The values of the electrical conductivity were found satisfactory enough, being 4.02 × 10−2 S/m for the multifunctional resin and 1.39 × 104 S/m for the in-plane conductivity of the panel, whereas the Limiting Oxygen Index (LOI) value of the multifunctional resin was found to increase from 27% to 36%. Considering these promising results, an experimental assessment of the vibro-acoustic properties of the manufactured multifunctional panel was also performed. The panel was tested mainly to evaluate its low-frequency vibration damping and sound insulation characteristics. The manufactured panel demonstrated an improved efficiency if compared to a baseline configuration, presenting almost the double modal damping and a gain of 10 dB on the global noise reduction.

Composite laminates made of unidirectional carbon fiber reinforced polymer interleaved with recycled carbon fiber and short virgin aramid fiber non‐woven mats for structural applications

AbstractThe Ashby limit for mechanical damping and stiffness trade‐off must be escaped to quantify composites for structural applications. To make the composites, all the participating fibers were converted into 60 g/m2 non‐woven mats, which were then sized with 1.5 wt. percent titanate coupling, TCA‐L12, before being sandwiched between two layers of 125 g/m2 resin films and used to interleave 12 unidirectional carbon fiber reinforced polymer prepreg tapes. Using the vacuum‐assisted compression molding method, the assemblage was subsequently turned into composites. The impact of micro‐hybridizing recycled carbon fibers with short virgin aramid fibers on mechanical damping and stiffness trade‐offs was examined. The Ashby limit was exceeded by 1600%, and compared to the control sample, the best laminate had a figure of merit that was 15.3% higher.

Analysis of low-energy impact damage to epoxy resin film based on surface damage characteristics

For fiber reinforced epoxy resin composites, when low-energy impact events occur, although the surface damage of the structure is invisible, a large area of delamination might have appeared inside. In order to detect these less noticeable impact damages, epoxy resin is intended to be used as an indicative coating to show obvious surface characteristics when the impact damage occurs. On that basis, the main purpose of this study is to establish the correspondence between the damage patterns of the epoxy resin film and the low-energy impact. First, a three-dimensional progressive finite element model was established and the impact damage mechanism of the film was analyzed. Then both numerical simulation and experimental investigation were conducted for the low-energy impact response of the film, and they were in good agreement with each other. The results showed that the damage characteristics of the epoxy resin film were clearly visible and changed regularly with the impact, as reflected by the fact that the damage area, the number of cracks and the crack distribution obviously depended on the magnitude of the impact energy. Therefore, the established simulation model can be used to predict and obtain systematic damage patterns of the film and offers the potential to evaluate the invisible impact damage of composite structures based on the regular damage patterns if the film is used as the indicative coating.

Electrical Investigation by Tunneling Atomic Force Microscopy of Carbon Fiber‐Reinforced Panels Manufactured by Modified Resin Film Infusion

AbstractThe purpose of this work is the detection of the electrical current map by tunneling atomic force microscopy (TUNA) of carbon fiber‐reinforced panels (CFRPs). The impregnation of the CFRPs is carried out through a multifunctional epoxy formulation containing glycidyl polyhedral oligomeric silsesquioxane (GPOSS), for improving flame resistance, and multiwall carbon nanotubes (CNT) to contrast the electrical insulating properties of the epoxy resin. The multifunctional panels are manufactured by an appropriately modified resin film infusion (RFI) process. The effects of the different ply numbers (seven, 14, and 24) on the TUNA electrical performance are assessed. In particular, TUNA technique, which is able to detect ultralow currents ranging from 80 fA to 120 pA, allows to identify the conductive paths due to CNTs. The CNTs result firmly anchored to the carbon fibers of the fabric layers. The adopted manufacturing process allows the transit of the nanofilled resin avoiding filtration effects. TUNA's current images highlight the presence, in the interlayer space of carbon fibers, of conductive three‐dimensional networks of CNTs through the plies. This occurrence ensures good electrical properties of the multifunctional panels, which results suitable for advanced structural applications.

Tack of epoxy resin films for aerospace-grade prepregs: Influence of resin formulation, B-staging and toughening

Aerospace-grade prepreg resin films based on multifunctional tetraglycidyl-4,4′-methylenedianiline (TGMDA), triglycidyl p-aminophenol (TGAP), Bisphenol A diglycidyl ether (DGEBA) and curing agent 4,4'diaminodiphenyl sulfone (DDS) are investigated in terms of tackiness by probe testing. The model epoxy systems are modified regarding the thermoplastic toughener content (polyethersulfone, PES) and the B-stage level, which is adjusted by cure prediction based on a model-free isoconversional method (Flynn-Wall-Ozawa). Additional DSC and rheological analysis are performed to study the thermal and viscoelastic material behavior in conjunction to its impact on temperature-dependent tack. Maximum achievable tack is found to decrease as a function of both degree of conversion and toughener content. Meanwhile, both influencing factors shift the tack maximum towards higher temperatures corresponding to increased flow characteristics attributed to evolving network formation and the incorporation of high molecular weight PES. In terms of absolute tack level and corresponding temperature, probe tack values similar to commercial prepreg systems (∼100 μJ mm−2) are recorded for TGMDA-based formulations containing 10 wt% PES at 20% pre-cure. Model formulations, which have neither been exposed to B-staging nor toughened, show exceptionally high tack below room temperature for all investigated epoxy prepolymers and are therefore not considered processable by automated fiber placement.

Enhanced damping and stiffness trade-off of composite laminates interleaved with recycled carbon fiber and short virgin aramid fiber non-woven mats

This paper proposes composite laminates interleaved with recycled carbon fiber and short virgin aramid fiber non-woven mats to enhance the trade-off of mechanical damping and stiffness. Compared with their virgin counterparts, recovered carbon fibers (rCFs) have the potential for damping enhancement at the cost of only minimal degradation in strength. A papermaking method was used to convert rCFs and virgin aramid fibers (vAFs) separately into 60 g/m2 non-woven mats, which were then sandwiched between two layers of 125 g/m2 epoxy resin films before interleaving. A vacuum-assisted compression molding process was then used to produce the laminates. The effect of a titanate coupling agent on the adhesion between the mats and the epoxy matrix was studied. The experimental results showed that the titanate coupling agent was an effective sizing agent for rCF and vAF mats with epoxy matrix. The laminate with a single core layer of sized rCF mat showed better flexural properties and dynamic performance than those with the sized vAF mat. The flexural modulus and dynamic properties were found to depend on the stacking sequence of the added non-woven mats. Compared with the control sample, the best laminate had a figure of merit of 0.73 GPa, which was 23.7% higher.

Experimental Study on Repairing Corroded Cracks by Electrophoretic Deposition

The corrosion of reinforced concrete could reduce its mechanical properties and cause concrete cracking. Electrophoretic deposition is a new method for repairing rust-cracked reinforced concrete. In this study, we observed the crack surface morphology, mass growth, epoxy resin film thickness, ultrasonic rate, and epoxy resin filling depth of rust-cracked reinforced mortar specimens during the repair process and investigated internal microstructure and phase composition of the repaired mortar, and clarified the principle behind the electrophoretic deposition of cationic epoxy resin and curing agent molecules in the repair solution. The result of research shows that longer repair times decreased the carbonization depth and water absorption of the specimens. After repair, the porosity of the surface mortar decreased, owing to the filling of epoxy resin, and the newly generated epoxy resin film had a dense structure. Thus, the carbonization resistance and waterproof performance of the repaired specimens improved. The repair process of electrophoretic deposition can be divided into the immersion, repair, and curing stages, and the physical and chemical principles of each stage were explained.

Adhesion Mechanism between Mold Resin and Sputtered Stainless Steel Ground Films for Electromagnetic Wave Shield Packages

Adhesion Mechanism between Mold Resin and Sputtered Stainless Steel Ground Films for Electromagnetic Wave Shield Packages

BIO16: Toward a Blood-Compatible, 3D Printing Resin For Microfluidic Artificial Organs

Purpose: Thrombogenic events are a limitation of artificial lung technologies for device longevity and patient safety. Currently, hollow fiber lungs and microfluidic artificial lungs (µALs) rely on surface modifications to improve hemocompatibility. Our goal to 3D print µALs inspired the development of a blood-compatible 3D printing resin to streamline fabrication of devices and remove the need for surface coatings. We aim to improve the blood compatibility of 3D-printed µALs via the inclusion of hydrophilic molecules directly into a high-resolution, polydimethylsiloxane 3D-printing resin formula. Methods: Hydrophilic molecules, dimethylsiloxane-[60-70% ethylene oxide] block copolymer (PEG-PDMS) and 2-Methacryloyloxyethyl phosphorylcholine (MPC) were directly integrated into our high-resolution 3D printing resin. Following resin work and printing characterization, thin films were made on the Asiga MAX X27 UV printer for subsequent testing. Wettability of the cured resin was determined with contact angle measurements over time. Blood compatibility was measured by exposing cured films to whole ovine blood, then running fluorescent assays and imaging for clot formation. Results: Incorporation of hydrophilic molecules induced a surface change from hydrophobic to hydrophilic when cured resin is exposed to water (Fig 1a). Printed surfaces containing hydrophilic additives reduced blood protein and cell adhesion after exposure to whole blood, as illustrated by reduced fluorescence intensity of FITC Fibrinogen and Membrite cell membrane stains (Fig 1b). Conclusion: The inclusion of hydrophilic molecules in the resin reduces the formation of blood clots thereby improving blood compatibility and potentially removing the need for subsequent surface modifications of printed parts. Fig. 1. (A) Contact angle measurements of commercially available PDMS, Sylgard 184, high-resolution resin alone referred to as “baseline resin”, the baseline resin with 1%MPC, and the baseline resin with 2%PEG (B) Protein (FITC Fibrinogen) and cell adhesion (Membrite) to cured films of resins (n=3 each) with and without hydrophilic additives. Images of representative films after testing with freshly drawn sheep blood are shown for (C) Sylgard 184, (D) Baseline resin, (E) 1% MPC, and (F) 2% PEG. The addition of hydrophilic molecules PEG and MPC to the resin decrease protein and cell adhesion compared to both the baseline resin and Sylgard 184.

Acrylic resin based dielectric composite with a novel hybrid composed of carbon nanotube grafted with graphene oxide

With the continuous miniaturization and integration of electronic devices, polymeric composites with high dielectric constant and low loss have received more and more attention from the field of research. In this work, a novel chemical modification method to fabricate a three-dimensional filler structure consisting of graphene oxide and carbon nanotube (CNT-g-GO) was proposed. Then this filler was introduced into acrylic resin elastomer (AE), and an approach of solution casting combined with hot pressing was used to fabricate the composite films, besides the physical blending composite films of graphene oxide, carbon nanotube and acrylic resin (CNT/GO/AE) were also prepared for a comparison. Results show that the composite containing a volume fraction of 6.72 vol% CNT-g-GO exhibits a dielectric constant of 204.3 and a dielectric loss of 0.16 at 100HZ. The hybrid filler of CNT grafted GO further improves the breakdown strength of composites below the 4.5 vol% filler addition. Furthermore, the origin of the dependence of dielectric loss factor on the frequency at the low frequency was studied with a theoretical model, additionally the mechanism on that enhanced interfacial interaction can more effectively influence the dielectric relaxation behaviors of composites was investigated according to Cole-Cole theoretical model.

Probing water uptake gradient in an epoxy matrix via scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) is used to detect and observe the presence of water inside polymeric film at the microscopic scale around 200–500 μm. The principle is based on the use of SECM performed with a room temperature ionic liquid (RTIL) and K4Fe(CN)6 as redox sensor. The particular electrochemical behaviors obtained in such medium have been investigated by performing cyclic voltammetry and approach curves in negative feedback mode. Then, the cross-section of epoxy resin films has been repeatedly scanned using the SECM probe over several days of immersion in the RTIL. As the presence of water impacts the electrolyte viscosity, the electrochemical signal was sensitive to the amount of water around the microelectrode. The sensitivity of this technique to the presence of water released from the materials at the microscopic scale was demonstrated by comparing electrochemical signals obtained on dry and saturated specimens. Such results appeared to be very promising for the development of new methods to locally detect the presence of water in thick polymeric materials and to measure humidity gradient within the material thickness.

Large-format preparation technology and electric heating performance of wooden electric heating flooring

A large-format manufacturing process of electric heating floors for indoor heating was evaluated in this work using large-format high-density fiberboard as the substrate, carbon fiber paper as the electric heating element, and semi-cured melamine resin film as the bonding material to elevate its production efficiency. The semi-cured melamine resin film permeated the carbon fiber paper to form a glued structure via hot-pressing process, which improved the water resistance and insulation of the electric heating layer. The internal bonding strength of the floor reached 1.63 MPa with the enhanced waterproof properties. The temperature rise of both the electric heating floor and the assembled floors can reach 20.5 °C within 60 min under the voltage of 220 V. There was a small difference of approximately 2 °C in the ambient temperature between the heights of 0.6 m and 1.8 m above the running assembled electric heating floors. The power of the assembled 16 pieces of floors stabilized at 830 W after the continuous electrification for 12 h in this test condition, which demonstrated the comfortable and high-efficiency heating performance of the assembled electric heating floors.

Photocatalytic Silica–Resin Coating for Environmental Protection of Paper as a Plastic Substitute

We developed an easy silica–resin coating technique to compensate for paper’s weaknesses, including its lack of water resistance and strength, and proposed its use as an environmentally friendly alternative to plastic. We demonstrate here that 2 nm anatase TiO2 nanoparticles were finely dispersed in a coating film with a thickness of several micrometers formed on the paper’s cellulose fibers and exhibited moderate photocatalytic effects such as methylene blue degradation and antibacterial activity. Additionally, the porous silica–resin film has a high adsorptive capacity, efficiently capturing organic pollutants until they decompose via photocatalytic reactions. As a result, the stable silica–resin–TiO2 composite coating protects paper from the environment for an extended period of time, transforming it into an excellent plastic substitute with enhanced functionality.

Influence of anode material on the effect of electrophoretic deposition for the repair of rust-cracked reinforced concrete

This study develops an electrophoretic deposition repair method explored the influence of anode materials on the repair efficiency and ability to prolong the service life of rust-cracked reinforced concrete effectively. The results show that the carbonation resistance and waterproofing performance of the repaired specimens are improved irrespective of the anode material. The material affected the morphology and thickness of the epoxy resin film on the repaired specimen surface and the depth of epoxy resin deposition within cracks, effected the waterproofing and carbonation resistance. The repair efficiency and effect were the best when a graphite plate was chosen as the anode, compared with the results observed use a graphite stick, stainless plate, stainless net, and titanium plate.

Modeling sizing emulsion droplet deposition onto silica using all-atom molecular dynamics simulations

Understanding structure–function relationships of the matrix–fiber interphase is important for the future design of composites with enhanced performance. This interphase structure is determined in part by sizing, an emulsion of epoxy film-former, silane coupling agent , and surfactant applied to fibers prior to work-up and resin impregnation . The multicomponent, microphase-separated nature of sizing makes it difficult to study using experiments and continuum-level simulations. In this study, microsecond all-atom molecular dynamics (MD) simulations are used to elucidate the dynamics of complex multicomponent sizing droplets on glass fiber surfaces. We analyze droplet/surface properties such as spreading factor, component density profiles, and spatial distribution of hydrogen bonds. From these observables, we show that the triblock copolymer surfactant enhances wetting of the epoxy resin film former on the glass surface, whereas the silane coupling agent slows down the spreading by pinning the droplet via siloxyl-surface hydrogen bonding. This work takes a step toward systematic understanding of the functionality of sizing in allowing pre-cured resin to wet glass surfaces in the context of composite lay-up. • Spreading dynamics of sizing droplets on silica depend on their composition. • Coupling agents deposit in rings that pin droplet contact lines and slow spreading.