Adhesive Polymer Research Articles

Absolute local conformation of poly(methyl methacrylate) chains adsorbed on a quartz surface.

Polymer chains at a buried interface with an inorganic solid play a critical role in the performance of polymer nanocomposites and adhesives. Sum frequency generation (SFG) vibrational spectroscopy with a sub-nanometer depth resolution provides valuable information regarding the orientation angle of functional groups at interfaces. However, in the case of conventional SFG, since the signal intensity is proportional to the square of the second-order nonlinear optical susceptibility and thereby loses phase information, it cannot be unambiguously determined whether the functional groups face upward or downward. This problem can be solved by phase-sensitive SFG (ps-SFG). We here applied ps-SFG to poly(methyl methacrylate) (PMMA) chains in direct contact with a quartz surface, shedding light on the local conformation of chains adsorbed onto the solid surface. The measurements made it possible to determine the absolute orientation of the ester methyl groups of PMMA, which were oriented toward the quartz interface. Combining ps-SFG with all-atomistic molecular dynamics simulation, the distribution of the local conformation and the driving force are also discussed.

Lubricant‐Infused Polymeric Interfaces: A Stretchable and Anti‐Fouling Surface for Implantable Biomaterials

AbstractDeveloping thin, highly stretchable coatings that inhibit the undesirable adhesion of biological substances on soft and high‐water‐content biomaterial surfaces is an area of significant interest. In this study, a stretchable antifouling coating named lubricant‐infused poly(1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinyl cyclotetrasiloxane) (V4D4) is introduced interface with perfluoropolymer (L‐VIP). The stretchable adhesive‐perfluoropolymer bilayer comprises stretchable adhesive polymer (V4D4) and perfluoropolymer (1H,1H,2H,2H‐perfluorooctyl methacrylate (FOMA)). The bilayer exhibits a strong affinity with the lubricant, imparting exceptional antifouling and slippery properties. L‐VIP coating displays superior fouling resistance against plasma proteins related to foreign body reactions (FBR) and biofilm‐forming bacteria. The coating exhibits impressive elastic limits exceeding 200% strain and exceptional stability under repeated cyclic stretching (> 2000 cycles at 150% strain) while maintaining its antifouling properties. Furthermore, the coating presents dielectric performance under accelerated aging conditions at a temperature of 70° and constant voltage stress of 10 V s−1 for over 50 days. To assess the biocompatibility of the L‐VIP coating, a series of in vitro and in vivo experiments are conducted, confirming its non‐toxicity for biomedical applications. It is expected that the stretchable L‐VIP coating will enhance medical devices’ longevity and help prevent bacterial infections, the formation of biofilms, and the nonspecific adherence of biological substances after implantation.

Water Clustering in Polyvinyl Butyral (PVB): Evidenced by Diffusion and Sorption Experiments.

Polyvinyl butyral (PVB) is a transparent amorphous polymer often used to protect fragile surfaces such as glass or photovoltaic panels. The polymer is then packaged in the form of adhesive sheets and bonded to the surfaces. The transport and retention of water in PVB are crucial properties to understand as they modulate the polymer's adhesion properties. In this work, we propose a detailed experimental study of water diffusion and sorption in PVB over a wide range of temperatures and humidity levels in the surrounding atmosphere. Using spectroscopic and gravimetric measurements, our study elucidates how the diffusion coefficient varies with temperature or vapor concentration and provides the activation energy for this process. In addition, dynamic vapor sorption experiments reveal (i) a strong dependence of sorption on hydroxyl group (-OH) concentration and (ii) that the solubility of vapor in PVB decreases with temperature. This enables us to trace the heat of the solution of water in PVB. A comparison of the thermodynamic data obtained with those for water in volume and with the engaged species induced clustering model supports the microscopic view of water organization in PVB in the form of clusters induced by hydrogen bonding.

Influence of high frequency on the fatigue life of metallic single lap joints

Polymer adhesives are known to exhibit time dependent mechanical behaviour, that becomes more and more evident approaching the glass transition temperature, Tg. When subjected to fatigue, bonded joint lifetime can be therefore affected by the loading frequency and amplitude. According to the literature, the influence of the frequency on the fatigue behavior manifests as a rise of the temperature in the adhesive due to the hysteretic heating, which is related in turn to Tg and to the viscoelastic properties of the adhesive. In this paper, cyclic loading was applied to single lap shear joints until failure at frequencies in the range of 70–90 Hz, that are little explored by the existing literature. The aim is twofold: on one side, to investigate the possibility to speed up fatigue tests in comparison to tests performed in the range of 7–9 Hz; on the other side, to explore the possibility to generate stress-life data in a range of number of cycles between 106 and 108, therefore two order of magnitude higher then usual, without exceeding with the time required for the tests. The joints were made with both aluminum and stainless-steel substrates bonded with a structural epoxy adhesive, to manufacture a Single Lap Joint (SLJ). Two loading ratios R (respectively 0.1 and 0.4, defined as the minimum over the maximum force of the fatigue cycle) and different load ranges were applied. Digital Image Correlation (DIC) technique was used to assess the presence of creep strains. A preliminary investigation consisting in a Dynamic Mechanical Analysis (DMA) of bulk adhesive for the range of frequency of interest, and in the measurement of the temperature of the adhesive layer during some selected fatigue tests was carried out. No significant changes of the viscoelastic properties of the adhesive were found for the frequency of interest, and, at the same time, temperature measurements revealed that the temperature increased by a few degrees, remaining in any case far from the glass transition temperature. The test results showed that only small effect due to the application of a high frequency cyclic loading on the fatigue life apparently occurs for tests carried out at the lowest load ratio, in particular when the applied loads were relatively low, and the number of cycles at failure relatively high. On the opposite, the results of tests carried out at the highest load ratio are affected by the loading frequency, and it has been related to the presence of significant creep deformation within the adhesive layer.

Improving the Strain Control Performance of MoS2 Monolayer to Develop Flexible Electronics

In recent years, two‐dimensional (2D) materials with unique mechanical, optical, and electrical properties have attracted extensive attention. In terms of mechanical properties, 2D molybdenum disulfide (MoS2) can perform larger strains than traditional semiconductor materials. In this contribution, the chemical vapor deposition technique to grow MoS2 films on a Si wafer and transfer them onto a flexible substrate is used. The controlled deformation of 2D MoS2 samples is realized by encapsulating them with a flexible acrylate film via successive spin‐coating and photopolymerization. Improved strain control is achieved due to the perfect integration of different components (MoS2/substrate) and the high adhesion of polymers. This approach provides a better detection of the changing structure of the MoS2 monolayer on the flexible substrate during tensile. It is noted that the crystal symmetry damage caused by strain is reflected in the redshift of the characteristic bands of MoS2. Hence, an effective way for strain regulation of MoS2 for future applications in flexible devices is provided.

Multiprocess additive manufacturing via fused deposition modeling, chemical deposition, and electroplating with tough interfacial adhesion

Multiprocess additive manufacturing (MPAM) unlocks new materials and design spaces where multimaterial components consisting of polymers, metals, and ceramics can be produced as one consolidated part. MPAM enables state-of-the-art 3D-printed electronics and devices with embedded functionality by combining fused deposition modeling with chemical deposition and electroplating processes. However, the metalized plastic devices produced by these processes have a short lifespan because of their poor structural integrity due to the low adhesion at the metal–polymer interface. In this study, we elaborated on the adhesion mechanism at the 3D-printed metal–polymer interface and identified the MPAM factors that elevated significantly the integrity of metalized plastic components. The effects of the 3D-printed surface texture and surface treatment on the adhesion strength of copper plated on acrylonitrile–butadiene–styrene parts were analyzed. We found that a certain 3D-printed topography modified by quick acid etching created a hierarchically structured interface with superimposed macroscale, microscale, and nanoscale roughness that symbiotically improved the metal–polymer adhesion. These results have practical implications for automated equipment manufacturers and the electronic industry adapting MPAM for the 3D printing of multimaterial components and devices with embedded functionality.

Evaluation of bonding techniques for ultrasound transducers

Development of ultrasound transducers for operation in high pressure and high temperature environments is still a challenge. This paper presents an evaluation of different bonding techniques for ultrasound transducers intended for harsh environments. Performance at temperature 180 °C was investigated at atmospheric pressure, and performance under hydrostatic pressure 1000 bar was investigated at temperature 15 °C. Five different bonding configurations were tested, two polymer adhesives and three metallurgical bonding methods. One of the polymer adhesives is a standard epoxy-adhesive, the other is an adhesive intended for operation at high temperatures. Two of the metallurgical bonding configurations studied are Solid-liquid Interdiffusion (SLID) bonds. The third metallurgical bonding method introduces preform soldering as a new bonding technique for ultrasound transducers. All the metallurgical bonding methods outperform polymer adhesives in shear strength and temperature stability. Compared to the SLID-methods, preform-soldering offers a faster and cheaper bonding process without the need for electroplating, making it an attractive metallurgical bonding technique for ultrasound transducers.

High-Throughput Screening of Thiol-ene Click Chemistries for Bone Adhesive Polymers.

Metal surgical pins and screws are employed in millions of orthopedic surgical procedures every year worldwide, but their usability is limited in the case of complex, comminuted fractures or in surgeries on smaller bones. Therefore, replacing such implants with a bone adhesive material has long been considered an attractive option. However, synthesizing a biocompatible bone adhesive with a high bond strength that is simple to apply presents many challenges. To rapidly identify candidate polymers for a biocompatible bone adhesive, we employed a high-throughput screening strategy to assess human mesenchymal stromal cell (hMSC) adhesion toward a library of polymers synthesized via thiol-ene click chemistry. We chose thiol-ene click chemistry because multifunctional monomers can be rapidly cured via ultraviolet (UV) light while minimizing residual monomer, and it provides a scalable manufacturing process for candidate polymers identified from a high-throughput screen. This screening methodology identified a copolymer (1-S2-FT01) composed of the monomers 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO) and pentaerythritol tetrakis (3-mercaptopropionate) (PETMP), which supported highest hMSC adhesion across a library of 90 polymers. The identified copolymer (1-S2-FT01) exhibited favorable compressive and tensile properties compared to existing commercial bone adhesives and adhered to bone with adhesion strengths similar to commercially available bone glues such as Histoacryl. Furthermore, this cytocompatible polymer supported osteogenic differentiation of hMSCs and could adhere 3D porous polymer scaffolds to the bone tissue, making this polymer an ideal candidate as an alternative bone adhesive with broad utility in orthopedic surgery.

Synthesis of novel vinyl preceramic polymer (PBSZ) adhesives and their performances in ceramic joints

It is a challenge to bind ceramics for aeronautical and astronautical engineering applications at ultrahigh temperature. In this work, a novel preceramic polymer (polyborosilazane, PBSZ) was synthesized by modifying polysilazane (PSZ) with n-butyllithium, vinylchloride and m-carborane. Furthermore, a high-temperature organic adhesive (PBSZ-based adhesive) was prepared with no pressure applied using PBSZ as a matrix and B4C powder as a filler. The ceramic yield of PBSZ-based adhesive increased to 86 wt%, and the binding strength between PBSZ-based adhesive and ceramic substrate could reach to 12.9 MPa after treatment at 800 °C. Also, the finite element analysis of PBSZ-based adhesive joint exhibited that the failure of joints occurred as the cohesion failure inside of the adhesive accompanied by the breakage of the substrate adjacent to the adhesive, which further confirmed good binding strength of the joint. The analysis of binding mechanism showed that the introduction of boron could generate strong chemical bonds (such as B–C, B–N, C–N, Si–B) in the adhesive, as well as intermolecular forces and B–C chemical bonds could be formed between the adhesive and the SiBON ceramic substrate. The high performance of the adhesive enables the application to the joining of ceramic materials for aerospace applications.

Mechano‐Activated Shape Morphing of Aluminum–Plastic Laminate Composites

Many “metallized plastic” packaging films bend if stretched and released. Such behavior can be reproduced in laminate composites prepared by bonding aluminum foil to an adhesive polymer sheet. It is shown that such bending occurs because stretching deforms the aluminum layer permanently (i.e., plastically), whereas the polymer layer deforms elastically. Upon releasing, the aluminum–polymer composite then resolves the strain mismatch by bending, with the aluminum on the convex side of the bend. The curvature is found to increase linearly with the applied strain and to reduce as the aluminum thickness increases. The theory of fully elastic bilayers with strain mismatch is in qualitative agreement with the results, but underpredicts the curvatures. It is shown how such bilayers can be patterned with defects such as holes or slits to realize more complex shape morphing, and also how one may achieve bidirectional bending. Such aluminum–polymer‐layered composites provide an inexpensive platform suitable for rapid prototyping of self‐folding origami structures using robust materials.

Modelling of damage and failure within polymeric adhesives

AbstractWithin this contribution, we propose a fully thermo‐mechanical coupled isotropic damage model for polymeric adhesives under finite strains. This model is based on the multiplicative decomposition of the deformation gradient into mechanical and thermal parts. We consider rate‐dependent damage behaviour (e.g. creep damage) of the material by applying a Perzyna‐type ansatz for the damage evolution equations. To overcome the pronounced mesh dependencies which would result from the usage of a local damage model, we make use of a gradient‐extended damage formulation. Besides the main aspects of model, we show the thermodynamically consistent derivation of constitutive quantities as well as the numerical treatment of the governing equations. Finally, we show selected numerical examples to demonstrate the capabilities of the model.

A crosslinked waterborne poly(vinyl acetate) for greenhouse gas fixation with improved elastomeric properties, shape-memory ability, and recyclability

The development of raw materials from methane and carbon dioxide holds significant potential to cut greenhouse gas (GHG) emissions and reduce the global carbon footprint. As an important monomer, vinyl acetate (VAc) can be produced by the consumption of acetic acid, which will potentially contribute to the reduction of GHGs emission. However, polymers based on VAc are usually prepared from emulsion polymerization in water which brings about the challenges of using modification processes to improve their properties. Here, a newly developed crosslink was able to establish covalently adaptable networks directly in water, enabling the formation of a poly(vinyl acetate) (PVAc) composite. As a result, PVAc emulsions using a monomer of 100% VAc could be transformed from a soft and weak adhesive polymer into an elastomeric polymer composite network with an elongation (775%) at break and flexibility. With the enhanced rubbery modulus, the polymer possesses characteristics for shape-memory material applications with 93% shape fixity and 99% shape recovery after repeated deformation and shape fixity for three times. The recyclability of the PVAc thermosets was demonstrated after granulating and remolding three times, representing an opportunity for designing a greenhouse gas fixing material.

Smallest form-factor multi-stacked ceramic patch antenna on package for 5G millimeter-wave mobile applications

A new design for a 5G millimeter-wave array antenna that is only 2.8 mm wide, using multi-stacked high-temperature ceramic substrates, is proposed in this paper. The antenna is designed to meet the requirements for esthetically pleasing and ergonomic smartphone designs and efficient component installations. To overcome challenges posed by the high relative permittivity and dielectric loss tangent of the ceramic substrates, the authors use a polymer adhesion layer with an air cavity and U-shaped probe feeding structures. The resulting 1 × 5 ceramic array antenna has a −10 dB impedance bandwidth in the low-band range of 24.25–28.35 GHz and the high-band range of 37–40 GHz, which covers the 5G New Radio frequency ranges n258, n260, and n261.

Blends of Conjugated and Adhesive Polymers for Sticky Organic Thin‐Film Transistors

AbstractHere, a polymer blend active layer that exhibits both electronic and adhesive properties is introduced. Various conjugated polymers are blended with a catechol‐based polymer that shows high adhesion, such that blends serve as the active layer of multifunctional sticky organic thin‐film transistors (OTFTs). Blend films maintain relatively constant field‐effect charge carrier mobility in OTFTs regardless of composition. Lap shear adhesion strength tests show that all blend films exhibit adhesive properties with adhesion values ranging from 0.05 to 4.30 MPa. With relatively consistent mobility and the presence of adhesive properties at different compositions, blends of conjugated and adhesive polymers can lead to next‐generation organic transistors for stable 3D stacking and waterproof adhesive sensors.

Effectiveness of Different Application Modalities on the Bond Performance of Four Polymeric Adhesive Systems to Dentin.

One of the major goals of adhesive dentistry is to improve the interaction of the already-existing adhesives with different substrates by using different application techniques. Thus, the objective of the present in vitro study was to assess the bond performance of four adhesive systems, Prime&Bond Universal (PBU), Clearfil SE Bond (CSE), OptiBond Universal (OBU), and OptiBond FL (OBFL), to dentin using various application modes: passive application (PA), active application (AA), Compo-Vibes modified application (CVM), and Compo-Vibes application (CV). Eighty extracted human molars were allocated into four groups based on the application modalities tested. The micro-tensile bond strength as well as fracture mode were tested in accordance with ISO/TS 11.405 after 24 h and 6 months of aging. Adhesive contact angle (CA) and scanning electron microscope analysis were also performed (n = 3). Statistical tests were performed with α = 0.05. After 24 h, a significant difference with a higher bond strength value was found for PBU in the AA modality and for CSE in the CVM modality (p < 0.05). However, no significant difference was shown between the techniques used among the other adhesives (OBFL and OBU). Moreover, at 24 h, only the PA demonstrated significant differences between the tested materials (p < 0.05). After 6 months, CSE, PBU, and OBU demonstrated significant differences between the techniques (p < 0.05), with a higher bond strength for CSE in AA and CVM modalities, for PBU in AA modality, and for OBU in AA and PA modalities. No significant differences were found between the techniques used among the OBFL (p > 0.05). In addition, only the CVM technique demonstrated significant differences between the tested materials after 6 months. CV and CVM showed a decreased value after aging for CSE and PBU, respectively. However, all the modalities decreased for OBU and OBFL after aging. All the adhesives showed marked resin infiltration into dentinal tubules in AA among all the modalities tested. Both universal adhesive systems (OBU and PBU) demonstrated statistically lower CA when compared to the other systems (CSE and OBFL) (p < 0.05) when applied in the PA mode. Concerning the AA mode, only CSE and OBFL were tested. The AA demonstrated lower CA values compared to the same adhesives in PA (p < 0.05). It could be concluded that the bond strength could be influenced by both materials and application techniques. It seems that the AA technique could be recommended as a gold standard for the application of an adhesive system to dentin. Plus, the CV and CVM modalities after 6 months of aging were considered stable for PBU and CSE, respectively. Consequently, the performance of these adhesive systems might vary when applied to other modalities. Future studies are needed to test this hypothesis.

Strong Protein Adhesives through Lanthanide-enhanced Structure Folding and Stack Density.

Generating strong adhesion by engineered proteins has the potential for high technical applications. Current studies of adhesive proteins are primarily limited to marine organisms, e.g., mussel adhesive proteins. Here, we present a modular engineering strategy to generate a type of exotic protein adhesives with super strong adhesion behaviors. In the protein complexes, the lanmodulin (LanM) underwent α-helical conformational transition induced by lanthanides, thereby enhancing the stacking density and molecular interactions of adhesive protein. The resulting adhesives exhibited outstanding lap-shear strength of ~31.7 MPa, surpassing many supramolecular and polymer adhesives. The extreme temperature (-196 to 200°C) resistance capacity and underwater adhesion performance can significantly broaden their practical application scenarios. Ex vivo and in vivo experiments further demonstrated the persistent adhesion performance for surgical sealing and healing applications.

In vitro evaluation of drying supports and adhesive polymers as adjuvants for biocontrol of Diplodia seriata by Trichoderma harzianum and Clonostachys rosea

Grapevine trunk diseases (GTDs) can cause large losses in vineyards. Diplodia seriata is an important GTD pathogen in Chile. Development and use of bioprotectors is a complementary alternative to the use of agrochemicals for disease management. To produce bioformulations for management of D. seriata, additives could be used to maintain viability and survival of biocontrol agents, such as Trichoderma harzianum and Clonostachys rosea. Effects of drying supports (inulin, maltodextrin, lactose, or talc) and adhesive polymers (carboxymethylcellulose, Aloe vera gel, or chitosan) were assessed on D. seriata conidium viability and mycelium development of T. harzianum and C. rosea, and for their biocontrol capacity against D. seriata. T. harzianum and C. rosea cultured in Potato Dextrose Agar containing inulin (at 10% w/v) maltodextrin (10% w/v), lactose (6% w/v), or talc (4% w/v), or the adhesive polymers carboxymethylcellulose (0.5% w/v), Aloe vera gel (0.5% w/v), or chitosan (1.5% w/v), maintained their biocontrol activity against D. seriata. These additives did not enhance D. seriata development. Therefore, these preparations, at the respective indicated concentrations, can be included in bioformulations for management of disease caused by this pathogen.

Study of microscopic imbibition and formation plugging mechanism of the compact oil reservoir based on SEM and NMR analysis

Unconventional reservoirs, such as compact reservoirs, have been extensively developed. The Changqing Oilfield is currently the largest compact reservoir oilfield in China. An effective method for developing compact reservoirs using hydraulic fracturing for reservoir modification is required. Some wells exhibited small production increases after fracturing, and some showed reductions in production. The impact mechanism of the fracturing fluid on the reservoir remains unclear. We used nuclear magnetic resonance (NMR) analysis and scanning electron microscopy (SEM) to investigate the utilization of a nano-micropore fluid and the surface morphology of the matrix during imbibition after fracturing. The results indicated polymer adhesion on the rock wall after the imbibition. The capillary force and the soaking pressure were the dominant driving forces during the imbibition. The capillary force was dominant in the small pores, and the soaking pressure had a larger influence on the fluid utilization of the large pores. The medium pores exhibited more significant solid phase damage, and the fluid utilization degree was relatively low. This study clarifies the impact mechanism of the fracturing fluid on the reservoir and the imbibition mechanism of slickwater. The results provide theoretical support and a scientific basis for optimizing fracturing, flowback methods, and post-fracturing stimulation in compact reservoirs.

Strong Protein Adhesives through Lanthanide‐enhanced Structure Folding and Stack Density

Generating strong adhesion by engineered proteins has the potential for high technical applications. Current studies of adhesive proteins are primarily limited to marine organisms, e.g., mussel adhesive proteins. Here, we present a modular engineering strategy to generate a type of exotic protein adhesives with super strong adhesion behaviors. In the protein complexes, the lanmodulin (LanM) underwent α‐helical conformational transition induced by lanthanides, thereby enhancing the stacking density and molecular interactions of adhesive protein. The resulting adhesives exhibited outstanding lap‐shear strength of ~31.7 MPa, surpassing many supramolecular and polymer adhesives. The extreme temperature (‐196 to 200°C) resistance capacity and underwater adhesion performance can significantly broaden their practical application scenarios. Ex vivo and in vivo experiments further demonstrated the persistent adhesion performance for surgical sealing and healing applications.

The influence of the microrelief of the metal surfaces of the substrate on the adhesive properties of meta-aramid coatings

Purpose. In order improving the tribotechnical properties of the surfaces of parts, a progressive method is the application of a polymer coating on a relatively cheap metal material. When choosing polymers for use in friction nodes, it is important to evaluate their properties, namely strength, heat resistance and wear resistance. In the technological process of applying coatings, the adhesion of polymers is a significant characteristic. The condition of the surface of the substrate and the viscosity of the polymer material should be attributed to the conditions affecting the formation of the adhesive contact. The purpose of this work is a detailed study of the influence of the nature and microrelief of the surface of the substrate on the adhesion ability of meta-aramid itself. The methods. To achieve the goal, a coating was applied to metal plates made of carbon steel St3 and copper alloy M1, the roughness of the surfaces of which was changed with the help of abrasive grinding wheels. The starting material of the coating in the form of a finely dispersed powder was dissolved in dimethylacetamide. A coating with a thickness of 80...100 μm was formed by applying a solution of meta-aramid on the surface of a metal substrate, followed by evaporation of the solvent in a drying cabinet at a temperature of 150...160ОС for 45...50minutes. To determine the strength of the adhesive joint of the meta-aramid coating from the surface roughness of the steel and copper substrate for different concentrations of the polymer solution, mathematical processing, approximation and extrapolation, experimental data were carried out in the work. Findings. The influence of the microrelief of the surface of metal substrates and the viscosity of the polymer solution on the adhesion ability of meta-aramid coatings was investigated. The optimal parameters of the roughness of the substrate and the concentration of the polymer solution were determined using the method of mathematical modeling. The originality. The relationship between adhesion indicators and the roughness of metal surfaces has been established. It helps to form recommendations regarding the parameters of the surface roughness of the substrate to ensure adhesion of the coating. Practical implementation. The application of polymer coating technology allows to increase the performance of parts in friction nodes, using relatively cheap metal materials for their manufacture. The obtained results form recommendations regarding the roughness parameters of the substrate surface and the concentration of the polymer solution.