Microsphere pressure sensitive adhesives—acrylic polymer/montmorillonite clay nanocomposite materials

In this study, the synthesis and characterization of acrylic polymer/montmorillonite (MMT) clay nanocomposite pressure sensitive adhesives (PSA) are presented. Different types and amounts of modified and unmodified montmorillonite clays were dispersed in ethyl acrylate (EA)/2-ethylhexyl acrylate (2-EHA) monomer mixture, which was then polymerized using a suspension polymerization technique. Polymerization was monitored in-line using attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy. The adhesion properties of the synthesized nanocomposite materials were determined using standard measurements of tack, peel and shear strength. Viscoelastic properties of dried adhesive films were analyzed using dynamic mechanical analysis (DMA). The results showed that the kinetics of suspension polymerization was independent of the addition of MMT clays. On the other hand, adhesive properties were strongly influenced by the type and the amount of MMT clay added. While peel strength and tack gradually decreased with higher amount of modified MMT clay, a substantial increase in shear strength was determined with a maximal value at 1 wt% of added MMT clay. Moderate influence on tack, peel and shear strength was observed when the unmodified type of MMT clay was used. DMA analysis showed an increase in storage modulus (G′) for adhesives synthesized with MMT clay addition, but no significant differences were determined between particular types of MMT clays. A decrease in tan δ value for adhesives with 1 wt% of added MMT clay was observed, which also concurs with higher shear strength and implies to the improved cohesion of adhesive.     

Mechanical behaviour of adhesively bonded polyethylene tapping tees

The mechanical properties of adhesively bonded MDPE joints were studied. The lap-shear joints were prepared using PE80 polyethylene gas pipe and four adhesive types; two acrylic and two epoxy resins. The key mechanical properties of lap shear strength and impact resistance were investigated as a function of adhesive type and surface preparation technique. Mechanical abrasion of the PE80 surface increased the strength of the bonds from 40 to 460% for the four adhesives, with the best performing acrylic adhesive having a lap-shear strength of 1.76 MPa and impact strength of 2.5 kJ/m². When used to bond PE80 tapping tees to PE80 gas pipe, the acrylic adhesive produced a gas tight seal at both the standard test pressure of 0.4 MPa and at an increased pressure of 0.8 MPa, and outperformed the PE80 tapping tee during shear testing and withstood a maximum of 10 cycles of 175 J during impact testing. These results highlight the potential of adhesive bonding as a method of joining PE80 tapping tees to PE80 gas pipe.     

Synthesis of a novel preceramic polymer (V-PMS) and its performance in heat-resistant organic adhesives for joining SiC ceramic

Heat-resistant organic adhesives are urgently needed for aeronautical and astronautical applications, and there have been only a few successful studies in this field. In this work, a novel preceramic polymer (V-PMS) has been synthesized by modifying polymethylsilane with 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, [CH₃(CH₂CH)SiO]₄, and this has been used as a heat-resistant adhesive. The obtained adhesive was found to exhibit outstanding thermal and bonding properties. The ceramic yield was about 81% (in Ar) and 90.6% (in air) at 1200 °C. The shear strength was 14.9 MPa at room temperature, and this increased to a maximum of 31.7 MPa after treatment at 1000 °C for 2 h in air. Moreover, it was interesting to find that on addition of B₄C powder to the preceramic polymer, its shear strength was surprisingly enhanced up to 50.8 MPa after annealing at 1200 °C under air atmosphere. Their excellent performances make the obtained adhesives promising candidates for joining SiC ceramics in high-temperature applications.     

Effect of proanthocyanidin incorporation into dental adhesive on durability of resin–dentin bond

BackgroundProanthocyanidin has shown to have beneficial effects on dentin bonding via its collagen cross-linking and protease inhibitory effects.ObjectiveThis study evaluated the effect of incorporation of 1–3% PA into a dental adhesive on durability of resin–dentin bond.Materials and methodsThe experimental adhesive was first formulated by combining 50 wt% comonomer mixtures with 50 wt% ethanol. PA was then added to the ethanol-solvated adhesive to yield three groups of adhesives at concentrations of 1.0 wt%, 2.0 wt% and 3.0 wt%. The PA-free adhesive served as control. Flat dentin surfaces from forty extracted third molars were etched with 32% phosphoric acid and the specimens were randomly assigned to one of the four adhesive groups. Two layers of experimental adhesives were applied to etched dentin and light-cured for 20 s after solvent evaporation. Composite build-ups were performed using Filtek Z250 (3M ESPE). The bonded teeth were divided into three subgroups for different methods of storage: (1) 24 h indirect water exposure (IE), (2) 6 M IE and (3) 6 M direct water exposure (DE). After the designated period of water storage, the bonded teeth were sectioned into 0.9 mm×0.9 mm beams for bond strength testing. Bond strength data were evaluated by two-way ANOVA and Tukey׳s tests (α=0.05). Interfacial nanoleakage was examined using a field-emission scanning electron microscopy. Two-way ANOVA and Tukey׳s tests were used to examine the effects of PA concentration and water exposure on bond strength and percentage of nanoleakage (α=0.05).ResultsTwo-way ANOVA showed that the factors, water exposure and PA concentration had a significant effect on bond strength (p<0.001). Interaction between the two factors was also significant (p<0.001). Bond strength of all four adhesives decreased with PA concentrations and ageing. Type of water exposure had no effect on the bond strength of PA-incorporated adhesive; while direct water exposure significantly reduced the bond strength of PA-free adhesive. Conversely, the factors, water exposure and PA concentration showed a significant effect on nanoleakage percentage (p<0.001). Interaction between the two factors was not significant (p>0.05).ConclusionIncorporation of proanthocyanidin into a dental adhesive did not prevent resin–dentin bond degradation over time.     

Preparation of high-temperature organic adhesives and their performance for joining SiC ceramic

Two kinds of high-temperature organic adhesives were prepared and successfully applied to join SiC ceramic. One adhesive was composed of preceramic polymer (V-PMS) and B₄C powder (HTA-1), and the other was composed of V-PMS, B₄C powder and low melting point glass powder (HTA-2). The properties of the obtained adhesives were investigated by TGA, XRD, bonding test and SEM analysis. The results show that the obtained adhesives exhibit outstanding heat-resistant property and excellent bonding strength. The bonding strength of HTA-1 treated at 200 °C, 400 °C, 600 °C were 26.8 MPa, 18.9 MPa, 7.3 MPa, respectively. When the temperature increased to 800 °C or even higher, the shear strengths of the joints were enhanced to over 50 MPa. Moreover, by adding glass powder as the second filler, it was found that the minimum shear strength of HTA-2 was enhanced to 16.4 MPa. The excellent performances of the obtained adhesives make them as promising candidates for joining SiC ceramics for high-temperature applications.     

Design of experiments for optimization a biodegrable adhesive based on ramon starch (Brosimum alicastrum Sw.)

In this work, a Central Composite Design (CCD) and Response Surface Methodology (RSM) were used to study the effect of starch content, hydrolyzing agent (NaOH) content, temperature and cooking period on peel strength and shear strength of biodegradable adhesives based on Ramon (Brosimum alicastrum Sw.) and Corn (Zea mays L.) starch. Scribe® paper was used as substrate or adherent. The CCD consisted of 36 experiments (including 12 central points). The second-order regression models of the response surface method, used to predict the response variables, exhibited a high correlation between the data obtained and the predicted data, and were thus considered reliable to optimize the mechanical properties for peel strength and shear strength of the Ramon starch adhesives. Starch content, hydrolyzing agent content and the cooking temperature of the adhesives proved to be the most significant factors affecting peel strength and shear strength of the adhesives of both the Ramon and corn starch. Moreover, the interactions of Starch-NaOH and Starch-Temperature were found to be the most significant in the adhesive properties in both adhesives. The mechanical properties (peel strength and shear strength) of both adhesives increased until reaching approximately their temperatures of gelatinization (T _{RAMON GEL} = 83 °C, T _{GEL CORN} = 72 °C). At higher temperatures, the mechanical properties of the adhesives diminished. The results of this study show that the adhesive prepared with the Ramon starch presents adhesive properties similar to those of an adhesive prepared with corn starch. This would imply that the Ramon starch is a viable alternative to substitute corn starch in industrial applications not relating to food production.     

Tensile shear strength of wood bonded with urea–formaldehyde with different amounts of microfibrillated cellulose

Urea–formaldehyde (UF) adhesive mixtures with a 5% suspension of microfibrillated cellulose (MFC) at 0.5, 1, 3, and 5 wt% loading levels based on the solid weight (62.4%) of the UF adhesive were prepared. Beech lamellas with dimensions of 5 mm×20 mm×150 mm were prepared from beech lumbers using a planer saw. The UF adhesive (E0 class) was mixed with the MFC using a magnetic stirrer to achieve a proper distribution of the MFC in the UF adhesive. The tensile shear strength of single lap-joint specimens bonded with UF adhesive containing MFC was determined in accordance with EN 205 (2003). The specimens bonded with UF adhesive containing the MFC showed better tensile shear strengths as compared to the control. As compared to the control specimens, the tensile shear strength of the specimens increased by 5.7% as 3 wt% of the MFC was incorporated into the UF adhesive. However, a further increment in the MFC content up to 5 wt% decreased the tensile shear strength of the specimens (−14.3% of control specimen). The MFCs were well dispersed in the UF resin and were cross-linked to form a network to reinforce the bond line, improving bonding performance.     

Process optimization of solvent based polybenzimidazole adhesive for aerospace applications

The use of adhesive bonding for high temperature applications is becoming more challenging because of low thermal and mechanical properties of commercially available adhesives. However, the development of high performance polymers can overcome the problem of using adhesive bonding at high temperature. Polybenzimidazole (PBI) is one such recently emerged high performance polymer with excellent thermal and mechanical properties. It has a tensile strength of 160 MPa and a glass transition of 425 °C. Currently, PBI is available in solution form with only 26% concentration in Dimethyl-acetamide solvent. Due to high solvent contents, the process optimization required lot of efforts to form PBI adhesive bonded joints with considerable lap shear strength. Therefore, in present work, efforts are devoted to optimize the adhesive bonding process of PBI in order to make its application possible as an adhesive for high temperature applications. Bonding process was optimized using different curing time and temperatures. Epoxy based carbon fiber composite bonded joints were successfully formed with single lap shear strength of 21 Mpa. PBI adhesive bonded joints were also formed after performing the atmospheric pressure plasma treatment of composite substrate. Plasma treatment has further improved the lap shear strength of bonded joints from 21 MPa to 30 MPa. Atmospheric pressure plasma treatment has also changed the mode of failure of composite bonded joints.     

Effects of adding nano-clay (montmorillonite) on performance of polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives in Carapa guianensis,a tropical species

The aim of this study was to improve the bond strength resistance of polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives modified with nano-clay (montmorillonite) with a tropical species of wood known to exhibit adhesion related problems. These adhesives were evaluated with 1.0 and 1.5 wt% nano-clay concentrations with lap shear strength (SS), and the percentage of wood failure (PWF) in dry and wet conditions being evaluated. An additional aim of this study was to observe the presence of nano-clay within both adhesive types using Atomic Force Microscopy (AFM) and the Transmission Electron Microscopy (TEM). Color, viscosity and the thermostability of these adhesives with nano-clay were also evaluated. First, AFM and TEM studies showed adequate dispersion and impregnation of nano-clay. The viscosity of PVAc adhesive was not affected by the incorporation of nano-clay, whereas the UF adhesive was. With both PVAc and UF adhesives, the presence of nano-clay increased the L^⁎ and b^⁎ color parameters, especially when 1.5 wt% nano-clay was used. The incorporation of the nano-clay improved thermostability, as determined by thermogravimetric analysis (TGA). Finally, it was shown that the nano-clay incorporation improved SS and PWF. The highest values of SS were obtained when nano-clay was added at 1.5 wt% concentration in the PVAc adhesive under dry conditions. SS was not affected by nano-clay addition in the UF adhesive under dry conditions. However, under wet conditions, both 1.0 and 1.5 wt% loadings of nano-clay increased SS with both adhesive types. The addition of nano-clay in both proportions increased PWF by approximately 15% and between 20–30% in dry and wet conditions, respectively, for the PVAc adhesive. For the UF adhesive, PWF increased by approximately 10% under dry conditions and 25–50% in wet conditions.     

Effect of erosive challenge and Nd:YAG laser irradiation on bond strength of adhesive systems to dentin

PurposeTo evaluate the effect of Nd:YAG laser irradiation and erosive challenge on bond strength of two adhesive systems to dentin.MethodsTwenty bovine incisors were cut and grounded to obtain eighty slabs of flat dentin. Specimens were allocated into eight groups, based on: adhesive system—a two-step etch-and-rinse and a two-step self-etch; laser irradiation—Nd:YAG (1 W/10 Hz) or control (no laser irradiation); and erosive challenge after restorative procedure—presence or absence of erosive challenge. Nd:YAG laser groups were submitted to laser irradiation before the restorative procedure. Blocks of composite resin were built up on the bonded surfaces with a Southern Dental Industries device to perform shear bond strength (SBS) test. After, each specimen of erosive challenge, groups were subjected to immersion in Sprite Zero^® (20 ml/2 h/24 °C/under agitation). The SBS test (0.5 mm/min) was performed after 24 h of water storage at 37 °C. Failure mode was evaluated with a stereomicroscope (X400). Data were analyzed with three-way ANOVA and Tukey’s post hoc tests (α=0.05).ResultsThe etch-and-rinse adhesive system presented higher bond strength values than self-etch adhesive. Laser irradiation increased the bond strengths values when erosive challenge was present. The predominant failure mode observed was adhesive.ConclusionsThe irradiation of Nd:YAG laser positively influences the bond strength values when erosive challenges are present. Moreover, the etch-and-rinse adhesive system is a better option to be used in dentin in this clinical condition.     

Application of selected 2-methylbenzothiazoles AS cationic photoreactive crosslinkers for pressure-sensitive adhesives based on acrylics

Since their introduction half a century ago, acrylic pressure-sensitive adhesives have been successfully applied in many fields. They are used in self-adhesive tapes, label signs, marking films and protective films as well as in medical pharmaceutical applications for plaster, in dermal dosage systems and in a wide range of biomedical electrodes. In the last 15 years or so, the UV technology, especially UV-crosslinking, is well established in the market and allows the production of UV-crosslinkable pressure-sensitive adhesives (PSA) based on acrylics with interesting performance. So much so that the larger manufacturers of pressure-sensitive adhesive materials and their suppliers now use very expensive equipment to study pressure-sensitive adhesive behavior: tack, peel adhesion and shear strength. The balance between adhesive and cohesive strength after the crosslinking process is very important and critical for properties of acrylic PSA in form of self-adhesive films. In this work the cationic UV-crosslinking of acrylic PSA containing epoxy groups in their structure and additionally cationic photoinitiators based on 2-methylbenzothiazoles as photoreactive crosslinkers have been investigated using UV-lamp as ultraviolet sources. The investigated acrylic PSA were synthesized from 80 wt% of butyl acrylate, and 20 wt% of glycidyl methacrylate. The use of selected photoreactive crosslinkers: 1,5-bis[N,N׳-(2-methylbenzothiazolium)]pentane diiodide and 1,10-bis[N,N׳-(2-methylbenzothiazolium)]decane diiodide allows manufacturing of high quality PSA materials with interesting properties, such as high tack, high peel adhesion, and excellent shear strength.     

Standardized methodology for in vitro assessment of bone-to-bone adhesion strength

Advancement of adhesives technology has been limited in orthopedics, which still has a striking reliance on metal hardware to help facilitate fracture healing. Despite an obvious clinical need, bone adhesives are not currently available on the market. Testing the bone adhesion strength and other aspects of the adhesive performance is extremely complex. This paper presents standardized methodology for in vitro assessment of bone-to-bone adhesion strength. Two test configurations (lap shear and butt joint) were used to comparatively assess the adhesion strength of four commercially available adhesive material, poly(methyl methacrylate) cement (CMW), glass-ionomer cement (FUJI), dimethacrylate resin (SB) and cyanoacrylate resin (VB), which were allowed to set under two environmental conditions (air and water). Under dry conditions, both test configurations generally yielded similar measurements of adhesion strength, which was around 1.1, 2.8 and 9.1 MPa for CMW, FUJI and VB, respectively. The dry adhesion strength for SB measured using the butt configuration (2.5 MPa) was 43.2% higher compared to that measured using lap shear (1.4 MPa). In a wet environment, the measured adhesion strength generally decreased and was dependent on the test configuration used. The failure mode of the samples adhered using CMW was adhesive, while that using FUJI, SB and VB was a combination of both adhesive and cohesive, independent of the test configuration and the setting condition. This proposed methodology is comparable to ASTM standards and can be used to study the effect of different biomaterial formulations as well as test parameters on the bone-to-bone adhesion strength, in a reproducible manner.     

Influence of storage time on bond strength of self-etching adhesive systems to artificially demineralized dentin after a papain gel chemical–mechanical agent application

ObjectivesThe aim of this study was to evaluate the influence of storage time on the bond strength of self-etching adhesive systems to artificially demineralized dentin submitted to application of a papain-based chemical mechanical agent for carious tissue removal.Materials and MethodsTwenty-four blocks of human coronal dentin were randomly divided into 2 groups: (1) restored with a two-step self-etching adhesive system (Clearfil SE Bond); (2) restored with a one-step self-etching adhesive system (One-Up Bond F Plus). After artificial caries induction, the specimens were treated with papain-based gel, received an application of the adhesive system according to the respective group, and blocks of microhybrid resin composite measuring 5.0 mm high and 5.0 mm wide were fabricated incrementally on the tooth, which would later be cut to obtain sticks with a bond area of around 1 mm², for use in the microtensile tests. After this, half of the sticks obtained from each tooth were submitted to the microtensile test 24 h later, while the other half were stored in water, in an oven at 37° C for a period of 180 d. The specimens were submitted to the microtensile test in a Universal Test Machine at a speed of 0.5 mm/min. The surfaces of the fractured test specimens were examined visually under a stereoscopic loupe in order to classify the fracture type. After exploratory analysis of the data, the two-way Analysis of Variance (ANOVA) and the Tukey test were applied. The data on the fracture types were analyzed by the Exact Fisher test.ResultsNo statistically relevant differences were verified among the means of the microtensile bond strength values of the adhesive systems evaluated in the different storage times. Mixed and adhesive fractures types were observed for both groups.ConclusionStorage time did not influence the bond strength of the two-step or one-step self-etching adhesive systems to artificially demineralized dentin submitted to application of a papain-based chemical mechanical agent for carious tissue removal. Both adhesive systems provided similar bond strength at different storage times.     

A multi-wall carbon nanotube-reinforced high-temperature resistant adhesive for bonding carbon/carbon composites

Multi-wall carbon nanotubes (MWCNTs) were chemically functionalized by 3-aminpropyltriethoxysilane and used to increase the strength and stiffness of an adhesive for joining carbon/carbon (C/C) composites. The silanized MWCNTs were uniformly dispersed in the adhesive with a good interface adhesion between them. When the content of silanized MWCNTs in the adhesive was 0.2 wt.%, average shear strength of the C/C joint was 10.40 MPa, which was 31% higher than that of neat C/C composites. The adhesive could be cured at room temperature with good heat-resistant property. The MWCNTs reacted with B₄C filler to establish strong B–O–C bond with C/C substrate.     

The effect of polymer molecular weight and crosslinking reactions on the adhesion properties of microsphere water-based acrylic pressure-sensitive adhesives

In this work, the effect of polymer molecular weight and crosslinking reactions on the end-use properties of the microsphere water-based acrylic pressure-sensitive adhesives (PSA) is presented. Polymer molecular weight and polymer microstructure were regulated using different chain transfer agent (CTA) concentrations and by addition of a diacrylic monomer (MM). The adhesion properties of the synthesized PSAs were characterized via measurements of tack, peel adhesion and shear strength. The results of experiments have shown that the kinetics of suspension polymerization is relatively independent on the amount of CTA and MM. The amount of gel phase in the adhesive was reduced with increasing amount of CTA agent, and gel phase amount may be considered as a function of polymer molecular weight. With a combination of CTA and MM was possible to regulate the amount of formed gel phase in the adhesive, as well sol phase molecular weight. All of the measured adhesion properties strongly depend on molecular weight of the synthesized polymer and on the amount of gel phase. For adhesives synthesized solely with addition of CTA, tack decreased with lower polymer molecular weight and consecutively also with lower amount of gel phase. The same trend was also observed for peel strength measurements, whereas a cohesive failure was observed for adhesives with low amount of gel phase. A maximum value for tack and shear strength was observed at 80 wt% of gel phase. In case of syntheses with a combination of CTA and MM (amount of gel phase in range from 70 to 80 wt%), tack values were distributed in quite narrow range. On the other hand, peel strength values decreased in comparison with adhesives synthesized only with CTA, regardless to the equal amount of gel phase. Poor shear strength was observed for all adhesives synthesized by combination of CTA and MM.     

High-frequency welding of polypropylene using dielectric ceramic compounds in composite adhesive layers

In this study, high-frequency welding of polypropylene by melting composite adhesive layers containing dielectric ceramics was investigated. Various dielectric ceramics were mixed in a fixed ratio with polypropylene to make the composite adhesive layers, and the resulting dielectric properties were measured using an impedance analyser. The highest loss factor in the composite adhesive layer was found when 40 vol% silicon carbide (SiC) was used in the mixture. Dynamic viscoelasticity measurements showed that all composite adhesive layers softened at approximately 170 °C and melted (fluidised) at approximately 190 °C. Each composite adhesive layer was inserted between two polypropylene plates, and irradiated at a frequency of 40 MHz. The composite adhesive layers that included 20 vol% anatase-titanium oxide, 20 vol% or 40 vol% zinc oxide and 20 vol% or 40 vol% SiC melted in 40–70 s. The bond strength of the welded material obtained was high, and the adherend failure occurred by a tensile lap shear test. The heating efficiencies of the composite adhesive layers by high-frequency radiation were related to the tanδ/ε′ value of the composites.     

Adhesion properties of soy protein adhesives enhanced by biomass lignin

Soy protein adhesives have great potential as sustainable eco-friendly adhesives. However, low adhesion under wet conditions hinders its applications. The objective of this research was to enhance the water resistance of soy protein adhesives. The focus of this research was to understand the effect of protein to lignin ratio and lignin particle size i.e. large (35.66 μm), medium (19.13 μm), and small (10.26 μm) on the adhesion performance of soy protein adhesives as well as to characterize its rheological and thermal properties. Results showed that the lignin particle size and the protein to lignin ratio greatly affected the adhesion performance of soy protein adhesives. The addition of lignin slightly increased the viscosity, spreadability, and thermostability of soy protein adhesives. The wet strength of soy protein adhesives increased as lignin particle size decreased. Soy protein mixed with small size lignin at a protein to lignin ratio of 10:2 (w/w) at 12% concentration presented the lowest contact angle and the highest wet adhesion strength of 4.66 MPa., which is 53.3% higher than that of 10% pure soy protein adhesive. The improvements in adhesion performance and physicochemical properties of soy protein adhesives by lignin were ascribed to the interactions between protein and lignin. Lignin with smaller particle size increased the wet shear strength of soy protein adhesives because a larger surface area of lignin was available to interact with the protein.     

Evaluation of CaO–Al2O3 adhesive bonding properties for β″-Al2O3 solid electrolyte sealing for alkali metal thermal electric converter

The β″-Al₂O₃ solid electrolyte (BASE) tube is an essential component of the alkali metal thermal electric converter (AMTEC) system for inducing the conduction of Na ions and generating electricity. Maintaining gas-tightness to produce Na vapor pressure deference and providing insulation to prevent the loss of generated current from BASE are important factors for the AMTEC system. The Na–sulfur (NAS) battery has a similar driving system and uses glass adhesives, which are not adequate for operation temperatures higher than 800 °C or in a Na atmosphere. In this study, CaO–Al₂O₃ was used as the adhesive to resolve such bonding issues. The bonding strength changes were evaluated as the adhesive bonding process temperature varied and also the results showed that CaO–Al₂O₃ maintained bonding shear strength of 400 MPa for more than 1000 h in a molten Na environment. This study also proposes an experimental technique based on tube-type impedance measurement to assess the bonding between the BASE and the α-Al₂O₃ insulator and to detect Na leakage. After conducting the experiment for 500 h, CaO–Al₂O₃ adhesive can offer higher reliability than glass adhesives.     

Preparation and characterization of novel film adhesives based on cyanate ester resin for bonding advanced radome

In this paper, the novel film adhesives based on phenolphthalein poly(ether sulfone) (PES-C) and epoxy (EP) modified cyanate ester resin (CE) were prepared for bonding an advanced radome. The film adhesives are convenient for applying to manufacture, possessing good adhesion strength, thermal durability and excellent dielectric property. The curing behaviors were confirmed by differential scanning calorimetry (DSC), showing that the main reaction pathways are not varied with adding PES-C but the reaction rates are evidently accelerated, and the film adhesives can be well cured at lower temperature of 177 °C. The adhesion strength was evaluated in lap shear strength and peel strength, indicating that the better adhesion strength is obtained with increasing in PES-C. The maximum value of lap shear strength is 33 MPa at room temperature. The thermal durability was determined by thermal aging tests of lap shear specimens, showing that the decrease in strength gets faster with adding PES-C, and the usability of film adhesives over 2000 h at 200 °C. The dielectric properties were measured by dielectric resonator methods, finding that the introduction of PES-C brings a positive effect on dielectric properties. The lowest value of determined dielectric loss is 0.0075 at 10 GHz.     

The effect of four methods of surface activation for improved adhesion of wood polymer composites (WPCs)

Wood Polymer Composites (WPCs) have attracted a lot of interest in recent years as materials with a high renewable content. However the adhesion between WPC components is problematic because of low surface energy and the hydrophobic nature of the most widely used polymer matrices, i.e. polyolefins. Thus this paper has looked at four surface activation pretreatment methods to improve adhesion properties for bonding using epoxy adhesives, namely: hydrogen peroxide solution; hot air; a gas flame; and halogen heating lamps. The treatments were applied to WPC materials made from 60% wood flour in a polypropylene matrix, and lap joint shear strength was measured.Shear strength values showed that all treatments except the halogen heating lamps increased the bond strength and the best results were achieved with hydrogen peroxide treatment at a pH of 7.5 (37% improvement); a two pass hot air treatment at a pass speed of 75 mm s⁻¹ (44% improvement); and a gas flame treatment at a pass speed of 175 mm s⁻¹(41% improvement).The bond strength was increased to values that caused failure within the material, rather than at the interfaces of the bond line.