Adhesive Resin Research Articles

Bioinspired water-retaining and strong soybean flour-based adhesive for efficient preparation of plywood

The development of a water-retaining and high-bond-strength soybean flour (SF) adhesive is important to improve the efficient and clean preparation of plywood, promoting the substitution of aldehyde resin adhesives in the wood-based panel industry. Soybean protein isolate (SPI) was enriched on boron nitride (BN) to form protein-functionalized BN nanosheets (BS) with dense hydrogen bonds. Drawing inspiration from the strength and toughness of muscles, bionic structures based on BS and SF were designed to enhance adhesive bonding strength and toughness. A water-retaining agent epoxy hyperbranched polyester (EHP) was also synthesized to improve water retention and further enhance the bond strength of adhesives. Results show that the prepared adhesive with BS and EHP exhibits better initial viscosity and coating performance compared with unmodified SF adhesives. The prepressing intensity and wet shear strength of the prepared plywood increased by 227% and 400% to 0.72 and 1.05 MPa. In addition, EHP significantly improved the water retention of the adhesive from 0.5 h to 2 h. After 2 h, the wet shear strength decreased by 30.5% to 0.73 MPa, still meeting the interior use plywood requirement. Notably, this study provides a simple technique of water spraying to recover the dried adhesive layer, and the wet shear strength increased from 0.73 MPa to 0.87 MPa. This preparation strategy of biomass adhesive with water retention and low environmental load bear guiding significance for the efficient and clean production of the wood-based panel.

Enhanced interfacial interaction, mechanical properties and thermal stability of basalt fiber/epoxy composites with multi-scale reinforcements

ABSTRACT In this work, epoxy (EP) resin composites with multi-scale reinforcements were prepared by hand lay-up and hot-pressing. The epoxy was reinforced with basalt fibers (BF) modified with a silane coupling agent (KH560). Carboxylated multi-walled carbon nanotubes (CNTs) were also grafted onto the surface of the modified BF using an impregnation method to achieve BF/CNTs multi-scale reinforcement. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that KH560 was successfully grafted onto the BF surface. Scanning electron microscopy (SEM), indicated a better resin adhesion on the BF and thus a stronger interfacial interaction in the BF/CNTs-reinforced composite. It was observed that the mass fraction of KH560 was a significant parameter in achieving desirable CNT immobilization and mechanical properties of the composites. At an optimal mass fraction of KH560 (5%), the tensile, flexural, and interlaminar shear strength (ILSS) of the modified composite (BF-5%KH560-CNT/EP) increased by 12.5%, 20.9%, and 25.5% respectively compared with the BF-washed/EP composite due to more efficient load transfer. In addition, compared with BF-washed/EP, the decomposition onset temperature of BF-5%KH560-CNT/EP increased from 387°C to 396°C, the maximum decomposition rate temperature increased from 400°C to 408°C, and the residual weight increased by 5.8%.

Bonding performance of experimental HEMA-free two-step universal adhesives to low C-factor flat dentin.

Experimental two-step universal adhesives (2-UAs) providing a particle-filled hydrophobic adhesive resin with a significant film thickness to hydrophobically seal the adhesive interface were designed and synthesized. This study aimed to characterize their interfacial interaction with dentin, to determine whether the 2-UA formulations achieve durable bonding to low C-factor flat dentin and to measure their water sorption. Bonding effectiveness of 2-UAs that combine a 10-MDP-based primer with hydrophobic adhesive resins differing only for filler (BZF-21, BZF-29, and BZF-29_hv) were comparatively investigated with the commercial adhesive Clearfil SE Bond 2 (C-SE2, Kuraray Noritake). Adhesive-dentin interfaces were characterized with TEM. Adhesive-resin disks were immersed in distilled water at 37°C for 1 week, 6 months and 1 year to measure water sorption and solubility. 'Immediate' and 'aged' micro-tensile bond strength (μTBS) of the adhesives applied in etch-and-rinse (E&R) and self-etch (SE) bonding mode to low C-factor flat dentin were measured. Statistical analyses involved linear mixed-effects (LME) modelling and Kruskal-Wallis testing (p<0.05). TEM revealed that E&R hybrid layers were more sensitive to aging than SE hybrid layers. Lower water sorption was recorded for all UAs compared with C-SE2. The immediate μTBS of BZF-21 and BZF-29 was not significantly different from that of C-SE2. The 1-year aged μTBS of all 2-UAs was significantly lower than that of C-SE2, except for BZF-29 applied in E&R mode. A significant reduction in μTBS upon 1-year aging was recorded for BZF-21 and BZF-29 applied in E&R mode. A significant difference in μTBS between E&R and SE bonding modes was recorded for all adhesives except BZF-21. Experimental 2-UAs with a hydrophobic adhesive-resin design produced±20-μm thick adhesive-resin layers, absorbed less water and resulted in bonding performance that was more aging-resistant when applied in SE than in E&R bonding mode. The silica-filled BZF-29 2-UA revealed the most comparable bonding performance with C-SE2 in a low C-factor condition (flat dentin).

Adhesion of veneering composite to metal-free CAD/CAM materials: effect of surface conditioning and adhesive resin type

ObjectivesThis study aimed to investigate the adhesion of veneering composite to metal-free computer-aided design/computer-aided manufacturing (CAD/CAM) materials with different compositions after surface conditioning and application of adhesive resins.Materials and MethodsA total of one hundred and sixty specimens were divided into four groups (n = 40) manufactured either from polyetheretherketone (PEEK; KERAstar PEEK), polyetherketoneketone (PEKK; Pekkton), fiber-reinforced composite (FRC; Trinia), or high-impact polymer composite (COMP; Bredent HIPC) CAD/CAM discs. Each group was then randomly subdivided into four different subgroups of adhesive systems (n = 10) as Visiolink (Bredent), Single Bond Universal (3M), G-Premio BOND (GC), and OptiBond Universal (Kerr). The shear bond strength (SBS) of each specimen with veneering composite material was tested with a universal testing machine following thermocycle aging (5000 times). The modes of failure resulting from the tests were determined with scanning electron microscope (SEM), dispersive spectroscopy (EDS), and analytical imaging. The data were statistically analyzed with two-way ANOVA and Bonferroni post hoc tests (alpha = 0.05).ResultsThe highest SBS values among all groups were found for the COMP material (20.28 ± 2.08 MPa) with OptiBond Universal adhesive, while the lowest for the PEEK material (10.33 ± 2.47 MPa) with G-Premio BOND. The most common failure mode for the PEEK and PEKK specimens was adhesive failure, for the FRC and COMP groups mixed failures were common.ConclusionsBond strength values of at least 10 MPa were achieved for all tested between metal-free CAD/CAM materials and adhesive resin application.

Immediate and Late Repair of Microhybrid Resin Composites: Effect of Silane Coupling Agent, Universal Adhesives and Photo Polymerization.

This study investigated the effect of silane coupling agent and universal adhesive application on repair bond strength of resin-based composite after bur grinding. Microhybrid resin composite (Charisma Smart) blocks (N=80; 8x8x4 mm3) were prepared, aged (37°C; 1 month), roughened, etched and randomly divided into two groups. Silane was applied to half of the groups (Porcelain Primer, Bisco), before one of the following universal primers/adhesives was applied: a) Scotchbond Universal (3M), b) All-Bond Universal (Bisco), c) G-Premio Bond (GC), and d) Clearfil SE Bond (Kuraray). In each adhesive group half of the group was photo-polymerized. The blocks were repaired with the same size resin composite and segmented into beams. Half of the beams were subjected to micro-tensile bond test (1 mm/min), while the other half was aged (37°C; 6 months) prior to testing. Failure modes were analyzed using Scanning Electron Microscopy (SEM). Data were analyzed using repeated measures of ANOVA, Tukey's post-hoc, and paired t-tests (alpha=0.05). The silane application did not affect the repair bond strength regardless of photo-polymerization of the adhesive resin. The repair bond strength decreased significantly after 6 months when adhesive resin was not photopolymerized (p⟨0.05). Photo-polymerizing universal adhesives might ensure higher repair bond strength and its maintenance after aging.

Kraft Lignin Periodate Oxidation for Biobased Wood Panel Resins

The development of biobased resins with high-bonding performance has gained considerable attention in the wood industry. In this study, we developed biobased novolacs phenol-formaldehyde (BNPF) resins by partially replacing petroleum-based phenol and formaldehyde with lignin derived from kraft biorefinery and modified kraft biorefinery-derived lignin, respectively. We first performed a mild and efficient chemical modification of the lignin through the periodate oxidation process. Sodium periodate was used to oxidize the hydroxyl functional groups present in the interunit linkages (β-O-4 bond) in the lignin structure and convert lignin partly to quinones. This was assessed by Fourier-transform infrared spectroscopy, elemental analysis, solid-state 1H–13C 2D HETCOR NMR, and aldehyde content analysis. We synthesized a series of BNPF resins by replacing phenol with lignin, then by replacing formaldehyde with oxidized lignin, and finally by replacing both phenol and formaldehyde with lignin and oxidized lignin. The structural characterization results of the NPF resins revealed the formation of methylene linkages in the phenolic rings. Before application as wood adhesives, we studied the curing behavior of the formulated adhesive via differential scanning calorimetry. The adhesion strength of the adhesive was determined using the tensile shear strength analysis. The bonding performance tests indicated that BNPF resin adhesives have high adhesion strengths (>0.7 MPa). The outcome of this research provides a promising perspective to utilize natural polymers such as lignin for the synthesis of biobased wood adhesives.

Comparative evaluation of the effect of 2% graphene oxide and 5% hydroxyapatite nanoparticles in isolation and in combination on micro tensile bond strength of 5th generation adhesive

Graphene is the thinnest, strongest and stiffest imaginable material. The biocompatible property of graphene oxide can initiate and facilitate cell adhesion, proliferation and differentiation of periodontal ligament, osteogenic and oral epithelial cells. Furthermore, the antibiofilm and anti-adhesion properties of graphene oxide in prevention of dental biofilm infections, dental caries, dental erosion as well as for implant surface modification and as anti-quorum sensing agent. Composites are most often utilised materials for restoration in the field of dentistry due to adhesive resins' improved mechanical and cosmetic properties. To safeguard the dentin and prevent dental cavities, dentin adhesives are utilised to affix hydrophobic resin composites to hydrophilic dentin tissue. Dental adhesives have a harder time adhering to dentin because it contains more water and is less mineralized than enamel. This makes the method more sensitive. As a result, it was chosen to assess and contrast the impact of 5% Hydroxyapatite nanoparticles and 2% Graphene oxide nanoparticles, both separately and together, on the Micro tensile bond strength of 5th generation adhesive. Graphene oxide is the most versatile form of Graphite in structural and functional configuration. Graphene oxide possess extraordinary physical, chemical, optical, electrical and mechanical properties. Among the graphene family nanomaterials, the reduced form of Graphite adding the oxygenated functional group to the structure increases the surface area and therefore exhibits enviable excellent interaction ability with metal and ions as well as organic species. Graphene oxide in dentistry has provided outstanding results in antimicrobial action, regenerative dentistry, bone tissue engineering, drug delivery, physicochemical property, enhancement of dental biomaterials and oral cancer treatment.

Straw density board vs. conventional density board: Is straw density board more sustainable?

The widespread use of density boards in various industries has caused a series of environmental issues. The results of this study can inform policy-making and facilitate the sustainable development of density boards. The research focuses on the comparison between 1m3 conventional density board and 1m3 straw density board, with the system boundary defined as "from cradle to grave." Their life cycles are evaluated across three stages: manufacturing, utilization, and disposal. To facilitate environmental impact comparisons, the production stage was divided into four scenarios based on different power supply techniques. To identify the environmental break-even point (e-BEP), variable parameters for transport distance and service life were incorporated into the usage phase. The disposal stage evaluated the most prevalent disposal method (100 % incineration). Regardless of the power supply method, the total environmental impact of conventional density board throughout its life cycle is always higher than that of straw density board, owing to the large amount of electricity consumption and the utilization of urea-formaldehyde (UF) resin adhesives in the raw material stage of conventional density boards. During the production stage, while the conventional manufacture of density boards results in environmental impacts ranging from 57 % to 95 %, which surpasses those of straw-based alternatives at 44 % to 75 %, modifying the power supply technique can alleviate such impacts by 1 % to 54 % and 0 % to 7 %, respectively. Thus, altering the power supply technique can effectively mitigate the ecological footprint of conventional density boards. Moreover, when assuming a service life, the remaining eight environmental impact categories exhibit an e-BEP at or prior to 50 years, with the exception of the primary energy demand (PED) values. Based on the environmental impact results, relocating the plant to a more judicious geographical location would indirectly increase the break-even transport distance and consequently mitigate the environmental impact.

Research of Potential Catalysts for Two-Component Silyl-Terminated Prepolymer/Epoxy Resin Adhesives.

The current research is devoted to the research of potential catalysts for the two-component silyl-terminated prepolymer/epoxy resin system. The catalyst system must catalyze the prepolymer of the opposite component while not curing the prepolymer in the component in which the catalyst is located. Mechanical and rheological characterization of the adhesive was performed. The results of the investigation showed that certain alternative catalyst systems, which are less toxic, may be used instead of traditional catalysts for individual systems. Two-component systems, obtained by using these catalysts systems, cure in an acceptable time scale and demonstrate relatively high tensile strength and deformation values.

Adhesion of individually formed fiber post adhesively luted with flowable short fiber composite

This laboratory study aimed to measure the push-out bond strength of individually formed fiber-reinforced composite (FRC) post luted with flowable short fiber-reinforced composite (SFRC) and to evaluate the influence of post coating with light-cured adhesive. Post spaces (Ø 1.7 mm) were drilled into 20 single-rooted decoronated premolar teeth. Post spaces were etched and treated with light-cured universal adhesive (G-Premio Bond). Individually formed FRC posts (Ø 1.5 mm, everStick) were luted either with light-cured SFRC (everX Flow) or conventional particulate-filled (PFC) dual-cure luting cement (G-CEM LinkForce). Half of the posts from each group were treated with dimethacrylate adhesive resin (Stick Resin) for 5 min before luting. After storage in water for two days, the roots were sectioned into 2 mm thick disks (n = 10/per group). Then, a push-out test-setup was used in a universal testing machine to measure the bond strength between post and dentin. The interface between post and SFRC was inspected using optical and scanning electron microscopy (SEM). Data were statistically analyzed using analysis of variance ANOVA (p = .05). Higher bond strength values (p < .05) were obtained when flowable SFRC was used as a post luting material. Resin coating of a post showed no significant effect (p > .05) on bond strength values. Light microscope images showed the ability of discontinuous short fibers in SFRC to penetrate into FRC posts. The use of flowable SFRC as luting material with individually formed FRC posts proved to be a promising method to improve the interface adhesion.

Influence of thickness and surface conditioning on fracture resistance of occlusal veneer

BackgroundThe purpose of the current study was to assess the impact of restoration thickness, surface conditioning and the interaction between them on the fracture resistance of CAD/CAM fabricated lithium disilicate occlusal veneers.MethodsA total of 42 maxillary molars were prepared to receive CAD/CAM fabricated lithium disilicate occlusal veneer either with 0.5 mm (n = 21) or 1 mm (n = 21) thickness. Each main group was divided into 3 subgroups (n = 7), according to surface treatment, HF acid (HF-1, HF-0.5), acidulated phosphate fluoride (APF-1, APF-0.5) and Monobond etch & prime (MON-1, MON-0.5). Multilinik N (Ivoclar-Vivadent) adhesive resin cement was used for bonding according to the manufacturer instructions. One hour after bonding, specimens were stored in water bath for 75 days followed by cyclic loading fatigue for 240,000 cycles to simulate clinical situation. Finally, specimens were fractured under compressive load in (N) using a universal testing machine. Two and one-way ANOVA and Post Hoc Tukey test were used for statistical analysis.ResultsThe means ± SD (N) fracture load for each group were calculated. MON-1 group showed the highest fracture load (1644.7 ± 155.3) followed by HF-1 group (1514.6 ± 212.5). Meanwhile, APF-0.5 showed the lowest fracture load (962 ± 249.6).ConclusionCAD/CAM fabricated lithium disilicate occlusal veneers can be used with a thickness of 0.5 mm instead of conventional crowns. Monobond etch & prime is recommended as a surface treatment for CAD/CAM fabricated lithium disilicate occlusal veneer due to biological hazards of Hydrofluoric acid.

Simulation and Experimental Study on Edge Bonding Shape for Reliable BGA Packages

In order to ensure thermal reliability including temperature cycling, semiconductor chips and packages mounted on a BGA substrate need a reinforced structure with adhesive resin. In this study, the relationship between reliability and the applied shape of the edge bond (EB) material was verified based on thermal stress simulation and actual experimental results. In consequence, the test vehicle with the cross-sectional area of 0.62 mm2 showed higher reliability than the one of 1.04 mm2 , and maintained the electrical continuity over 3100 cycles. This result showed that there was an optimal cross-sectional area of EB material to obtain high reliability.

Incorporation of Zirconium Oxide Nanoparticles in Adhesive Resin for Bonding of Brackets to Enamel Conditioned with Er,Cr:YSGG, Photodynamic Therapy, and Phosphoric Acid.

Objective: To evaluate the effect of enamel conditioning methods, that is, total-etch and rinse (TER), Er,Cr:YSGG (ECYL), and photodynamic therapy (PDT) on the shear bond strength (SBS) of orthodontic metallic brackets bonded using Zirconium oxide experimental adhesive (ZOEA). Methods: Sixty human incisor buccal surfaces were cleaned and allocated into three groups based on the method of enamel surface treatment, that is, TER using 37% phosphoric acid gel, methylene blue photosensitizer activated by PDT and ECYL (n = 20 each). Each group was further divided into two subgroups (n = 10) based on the type of adhesive, that is, ZOEA and experimental adhesive (EA). Metallic brackets were seated using composite resin. Samples were placed in a universal testing machine for SBS and failure mode using the ARI index. One-way analysis of variance and post hoc Tukey were used for multiple comparisons. ARI was presented in percentages in different investigated groups. Results: TER+ZOEA (17.16 ± 0.41 MPa) displayed the highest bond integrity. However, group PDT+EA (11.34 ± 0.25 MPa) demonstrated the lowest bond scores. The intergroup comparison revealed that the TER system displayed significantly higher SBS values than the PDT and ECYL groups (p < 0.05). The intragroup comparison revealed that enamel conditioned with TER and brackets bonded with ZOEA and EA displayed comparable bond integrity (p > 0.05). Conclusions: Enamel conditioned with TER bonded to a metallic bracket displayed better bond strength than PDT and ECYL. Zirconium oxide nanoparticles incorporated in adhesive have proved to be promising in improving the bond integrity of adhesive.

Surface adhesion of pMDI resin on wood biopolymer model films

Surface adhesion of pMDI resin on wood biopolymer model films

Flexural Properties in Edgewise Bending of LVL Reinforced with Woven Carbon Fibers.

This paper presents the results of experimental testing of the bending strength and modulus of elasticity in edgewise bending of unreinforced and reinforced seven-layer LVL (laminated veneer lumber) poplar veneer panels. The aim of the research is to determine the influence of woven carbon fibers on the improvement of the bending properties and modulus of elasticity of LVL bending in the plane of the plate, as well as the influence of adhesives on the bending properties of the composite product, in order to test the potential of using this newly obtained material as a structural element. Bending was performed on small-scale samples. The main research task is the examination of three types of reinforcement, which differ from each other in position, orientation, and number of layers of reinforcement, using two different types of adhesives: epoxy adhesive and Melamine Urea Formaldehyde Resins (MUF). The composite material was produced in four different combinations in relation to the orientation and position of the reinforcement in the layup. The applied reinforcement is defined through three different configurations (EK1, EK2, and EK3) and a fourth control sample (EK4). Each configuration was produced by applying the two previously mentioned types of adhesives. The research findings showed that in the case of samples produced by applying CFRP (carbon fiber reinforced polymer) using epoxy adhesive, it significantly affected the increase in bending strength and flexural modulus of elasticity. The average improvement in bending strength is 32.9%, 33.2%, and 38.7%, i.e., the flexural modulus of elasticity is 54.1%, 50.7%, and 54.7%, respectively, for configurations EK1, EK2, and EK3, compared to control sample EK4. During the testing, the test samples from reinforced panels EK1 and EK2 showed partly plastic behavior up to the fracture point, while the diagram for the test samples from reinforced panels EK3 shows elastic behavior to a considerable extent, with a significantly smaller plastic behavior zone. This research proved the impossibility of using melamine-urea formaldehyde adhesive to form a composite product based on veneer and carbon fabric. The greatest contribution of this work is the experimentally verified and confirmed result of the possibility of applying poplar veneer to design structural elements in LVL using epoxy adhesive.

Multi-Objective Optimization of Epoxy Resin Adhesive for Pavement Toughened by Self-Made Toughening Agent.

Epoxy resin adhesive for pavement is often insufficient in flexibility and toughness. Therefore, a new type of toughening agent was prepared to overcome this shortcoming. To achieve the best toughening effect of a self-made toughening agent on an epoxy resin adhesive, its ratio to the epoxy resin needs to be optimally selected. A curing agent, a toughening agent, and an accelerator dosage were chosen as independent variables. The epoxy resin's adhesive tensile strength, elongation at break, flexural strength, and flexural deflection were used as response values to establish a single-objective prediction model of epoxy resin mechanical property indexes. Response surface methodology (RSM) was used to determine the single-objective optimal ratio and analyze the effect of factor interaction on epoxy resin adhesive's performance indexes. Based on principal component analysis (PCA), multi-objective optimization was performed using gray relational analysis (GRA) to construct a second-order regression prediction model between the ratio and gray relational grade (GRG) to determine the optimal ratio and to validate it. The results showed that the multi-objective optimization using response surface methodology and gray relational analysis (RSM-GRA) was more effective than the single-objective optimization model. The optimal ratio of epoxy resin adhesive was 100 parts of epoxy resin, 160.7 parts curing agent, 16.1 parts toughening agent, and 3.0 parts accelerator. The measured tensile strength was 10.75 MPa, elongation at break was 23.54%, the bending strength was 6.16 MPa, and the bending deflection was 7.15 mm. RSM-GRA has excellent accuracy for epoxy resin adhesive ratio optimization and can provide a reference for the epoxy resin system ratio optimization design of complex components.

Effect of polymerization activation mode and accelerated aging in the degree of conversion of self-adhesive resin cements

Indirect adhesive restorations are increasingly being part of the oral rehabilitation procedures. With the purpose to reduce and minimize the difficulties and simplify the cementing technique with conventional adhesive resin cements, it was introduced a resin cement called self-adhesive for presenting chemical adhesion to dental tissues, ceramic and metal surfaces without the need for etching and adhesive systems aplications. Some studies point out to the problems of degradation of cement during storage. The inhibitors and peroxides presented in the cement composition are organic chemical compounds and, therefore, are susceptible to degradation phenomena under storage. For all of these factors, the resin cements have limited storage period and changes in the mechanism of polymerization may occur during this period. The present study has been prepared containing some variables to research. All these variables are seeking to investigate the consequences of different activation protocols of polymerization and the accelerated aging of self-adhesive dual cured resin cements on the degree of conversion. As well as test the null hypothesis that the activation protocol of polymerization and the accelerated aging do not cause alteration in the degree of conversion of the material to be tested.

Fabrication and Characterization of EVA Resins as Adhesives in Plywood.

The practical problem of free formaldehyde pollution in the plywood industry is that polyethylene films have been shown to be able to replace some urea-formaldehyde resins for wood adhesives. To broaden the variety of thermoplastic plywood, reduce the hot-press temperature, and save energy consumption, an ethylene-vinyl acetate (EVA) film was selected as a wood adhesive to manufacture a novel wood-plastic composite plywood via hot-press and secondary press processes. The effects of the hot-press and secondary press processes at different levels on the physical-mechanical properties of EVA plywood (tensile shear strength, 24 h water absorption, and immersion peel performance) were evaluated. The results showed that the properties of the resulting plywood using the EVA film as an adhesive could meet the type III plywood standard. The optimum hot-press time was 1 min/mm, the hot-press temperature was 110-120 °C, the hot-press pressure was 1 MPa, the dosage film was 163 g/m2, the secondary press time was 5 min, the secondary press pressure was 0.5 MPa, and the secondary press temperature was 25 °C. EVA plywood can be used in indoor environments.

Molecular Understanding of Adhesion of Epoxy Resin to Graphene and Graphene Oxide Surfaces in Terms of Orbital Interactions

The adhesion mechanism of epoxy resin (ER) cured material consisting of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenyl sulfone (DDS) to pristine graphene and graphene oxide (GO) surfaces is investigated on the basis of first-principles density functional theory (DFT) with dispersion correction. Graphene is often used as a reinforcing filler incorporated into ER polymer matrices. The adhesion strength is significantly improved by using GO obtained by the oxidation of graphene. The interfacial interactions at the ER/graphene and ER/GO interfaces were analyzed to clarify the origin of this adhesion. The contribution of dispersion interaction to the adhesive stress at the two interfaces is almost identical. In contrast, the DFT energy contribution is found to be more significant at the ER/GO interface. Crystal orbital Hamiltonian population (COHP) analysis suggests the existence of hydrogen bonding (H-bonding) between the hydroxyl, epoxide, amine, and sulfonyl groups of the ER cured with DDS and the hydroxyl groups of the GO surface, in addition to the OH-π interaction between the benzene rings of ER and the hydroxyl groups of the GO surface. The H-bond has a large orbital interaction energy, which is found to contribute significantly to the adhesive strength at the ER/GO interface. The overall interaction at the ER/graphene is much weaker due to antibonding type interactions just below the Fermi level. This finding indicates that only dispersion interaction is significant when ER is adsorbed on the graphene surface.

Preparation of Hydrophobic Low-k Epoxy Resins with High Adhesion Using a Benzocyclobutene-Rosin Modifier

With the development of high-frequency communication, the miniaturization of integrated circuits (ICs) has led to interconnected signal delays and losses. The dielectric properties of epoxy resins are no longer satisfactory, because of the presence of polar groups. Herein, a benzocyclobutene-rosin modifier was designed and synthesized to reduce the dielectric constant of epoxy resins. The recross-linking network of benzocyclobutene inhibits the polarizability of the polar groups, and rosin skeletons increase the free volume of epoxy resins. Consequently, the dielectric constant of epoxy resins decreased from 3.12 to 2.72 and their water absorption decreased from 1.06% to 0.861%. The dielectric constant and water absorption are lower than those of most commercial dielectric materials. Additionally, the adhesion of epoxy resins was improved, which broke the contradiction between the dielectric properties and the adhesion of traditional epoxy resins. The modified epoxy resin was finally applied to printed circuit boards. At 15 GHz, its signal loss was 28.8 dB, which was lower than that of a commercial epoxy resin (FR-4), demonstrating that the modified epoxy resin can better meet the miniaturization needs of ICs.