Epoxy Surface Research Articles

Microarray analysis of protein–protein interactions based on FRET using subnanosecond-resolved fluorescence lifetime imaging

The detection of protein–protein binding on microarrays using the fluorescence lifetime as a dynamic analytical parameter was investigated in a model system. The assay is based on Förster resonance energy transfer (FRET) and carried out with biotinylated Bovine Serum Albumin and streptavidin, labeled with the commonly used microarray dyes Alexa 555 and Alexa 647, respectively. This efficient FRET donor/acceptor pair was employed in a competitive assay format on three different microarray surfaces. The fluorescence was excited by 200 ps laser pulses from a mode-locked and cavity-dumped argon-ion laser, adapted to an intensified CCD camera as detection unit allowing time resolution with subnanosecond precision. Lifetime maps were recorded according to the Rapid Lifetime Determination (RLD) scheme. Interaction between the proteins could clearly be detected on all formats and resulted in almost complete quenching on CEL Epoxy surfaces upon addition of excess streptavidin labeled the FRET acceptor dye. In this case, the fluorescence lifetimes dropped by 90%, whereas on ARChip Epoxy and ARChip Gel the reduction was 54% and 47%, respectively. Good linearity of the quenching curve was obtained in all cases. The method is applicable to all types of protein interaction analysis on microarrays, particularly in cases where evaluation of fluorescence intensity is prone to erroneous results and a more robust parameter is required.

Sexual dimorphism in the attachment ability of the Colorado potato beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) to rough substrates

Many representatives of the beetle family Chrysomelidae exhibit a distinctive sexual dimorphism in the structure of adhesive tarsal setae. The present study demonstrates the influence of surface roughness on the friction force of Leptinotarsa decemlineata males and females. The maximum friction force of individual beetles was measured on epoxy resin surfaces (smooth and with asperities ranging from 0.3 to 12.0μm) using a centrifugal force tester. On the smooth surface, no considerable differences between males and females were found, whereas on rough surfaces, females attached significantly (up to two times) stronger than males. Clawless beetles generated lower forces than intact ones, but demonstrated similar differences between males and females. The results indicate that the female adhesive system has its main functional trait in a stronger specialisation to rough plant surfaces whereas the adhesive system of males possess a certain trade-off between attachment to rough plant surfaces during locomotion on vegetation and to the smooth surface of the female elytra, while mating.

Effect of polyhedral-oligomeric-sil-sesquioxanes on thermal and mechanical behavior of SC-15 epoxy

In this study, thermal and mechanical properties of nanocomposites containing SC-15 epoxy resin and polyhe- dral-oligomeric-sil-sesquioxanes (POSS) have been studied. Dynamic Mechanical Analysis (DMA) results show that the addition of 5 wt% of POSS yielded a 13% increase in the storage modulus and a 16°C enhancement in Tg. Thermo gravi- metric Analysis (TGA) results show that the thermal stability of epoxy increased with higher POSS content. Tension tests were used to evaluate the mechanical properties of materials. Both modulus and tensile strength are linear functions of POSS content. Scanning Electric Microscopy (SEM) pictures of fracture surfaces show that the roughness of the fracture surfaces of epoxy increased after adding POSS. Based on experiment results, a three-parameter nonlinear constitutive equa- tion was developed to describe the strain-softening stress-strain relationship behavior of materials. The parameters in this model are the elastic modulus, a strain exponent, m, and a compliance factor, β. Their relationships to the POSS weight fraction were obtained from the experiment results. The simulated stress-strain curves from the model agree with the test data. Analysis of the model shows that both the strain exponent, m, which controls the strain softening and hardening effect of the material, and the compliance parameter, β, which controls the flow stress level of the material, increase with higher POSS content.

Study on the viscoelastic properties of the epoxy surface by means of nanodynamic mechanical analysis

AbstractThe viscoelastic properties of the epoxy surface have been investigated by nanodynamic mechanical analysis (nano‐DMA). Both a Berkovich tip and a conospherical tip were used under the condition of different forces (i.e., different penetration depths) in the frequency range of 10–200 Hz. Loss tangent and storage modulus are characteristics that describe the viscoelastic properties. The effect of force frequency, penetration depth, and tip shape on the viscoelastic properties is studied and discussed according to the features of microstructures and mobility of molecular chains. The experimental results show important variations when the penetration depth is shallow (<30 nm). As the depth becomes deeper, the results tend to be stable and become almost constant over 120 nm. The two kinds of indenter tip can cause a slight difference of the storage modulus. A “master curve” of the storage modulus as a function of force frequency is established. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 281–288, 2008

Study of the Failure Mechanism of the Cu/Epoxy Interface After Modifications by Means of Surface Chemical Reactions

The chemical part of adhesion is studied at epoxy-copper interfaces. This is realized by creating epoxy surfaces with constant surface roughness by means of wet chemical pretreatments (sweller and oxidizer). These roughened epoxy surfaces are chemically transformed by nucleofilic substitutions using an anchoring molecule, 2-mercaptopyrimidine and glycerol. Cu is deposited by an electroless and electroplating scheme, followed by patterning. After patterning peel strengths are measured. The peeled epoxy surface and the backsides of the peeled Cu-strips are examined by means of XPS. These experiments are used to determine the influence of the interface atomic composition on the locus of failure during peeling.

The use of plant waxes as templates for micro- and nanopatterning of surfaces

Small wax sculptures on plant surfaces are responsible for a variety of functions, including the maintenance of sability, self-cleaning properties, prevention of insect attachment and reflection of light. Here we report on a method for using recrystallized plant wax crystals on flat technical surfaces for generating micro- and nanopatterned polymers with particular functions. Therefore a more than 4-thousand year old replica technique called the “lost wax technique” has been adapted for reproduction of complex, high aspect ratio surfaces and the large scale reproduction of micro- and nanopatterned surfaces. Highly ordered pyrolytic graphite substrates, covered with perpendicularly oriented platelets formed by the primary alcohol octacosan-1-ol, the main component of wheat ( Triticum aestivum) leaf waxes, were used as templates to make an epoxy resin surfaces with high aspect ratio platelets 400–700 nm wide and 10–50 μm thick. The technique holds great promise on the reproduction of micro- and nanopatterned surfaces.

Effects of surface modification with amino branched polydimethylsiloxane (ABP) on the corrosion protection of epoxy coating

An epoxy coating was designed to give a hydrophobic property on its surface by modifying it with three types of amino branched polydimethylsiloxane (ABP), and then effects of the modification on the structure, surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified epoxy coating were examined using FT-IR spectroscopy, hygrothermal cyclic test, and impedance test. The surface of epoxy coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between epoxy and modifier by the modification. The phase separation tendency is more appreciable when modified by ABP with higher molecular weight ABP at higher content. Water transport behavior of the modified epoxy coating decreased more in that with higher hydrophobic surface property. The resistance to localized corrosion of the modified epoxy coated carbon steel was well agreed with its water transport behavior and hydrophobic tendency.

Cryogenic mechanical behaviors of MMT/epoxy nanocomposites

Montmorillonite/epoxy (MMT/epoxy) nanocomposites were prepared by incorporating the organo-MMT slurry modified by acidified 2,4,6-tris-(dimethylaminomethyl) phenol (DMP-30) into the mixture of diglycidyl ether of bisphenol-A (DGEBA) and PU modified bisphenol-A using methyltetrahydrophthalic anhydride (MeTHPA) as the curing agent. X-ray diffraction (XRD) results showed that the nanocomposites at the 1 wt% MMT content exhibited no observable peaks in the range of 2–10° (2 θ), indicating that most of the organo-MMT particles in the nanocomposites were exfoliated. The dispersion and exfoliation of organo-MMT in the nanocomposites were also observed using transmission electron microscopy (TEM). Mechanical behaviors of MMT/epoxy nanocomposites at both room temperature (RT) and liquid nitrogen temperature (77 K) were investigated in terms of tensile and impact properties. The strength and modulus of the nanocomposites were significantly higher at 77 K than at RT and these observations were explained in terms of the interfacial adhesion and constituent properties at 77 K and RT. The fracture surfaces of neat epoxy and MMT/epoxy nanocomposites were examined using scanning electron microscopy (SEM). Finally, the dependence of the glass transition temperature on the organo-MMT content was examined by differential scanning calorimetry (DSC).

Filiform corrosion attack on pretreated aluminum alloy with tailored surface of epoxy coating

In the study, on the basis of material analysis of 6016 aluminum alloy widely used in Europe automotive industry, the influences of surface pretreatment on filiform corrosion and adhesion of epoxy coating/aluminum alloy interface were investigated, and the effect of rolling direction and coating property on filiform corrosion was also examined. The alloy surfaces were pretreated with etching solution, and then, respectively, with Aminopropyl silane solution, Aminopropyl phosphonate solution, and hexamethyldisiloxane plasma.The results showed that the susceptibility of pretreated surface to filiform corrosion was basically consistent with the distribution of intermetallic particles, and that water permeation and the tensility of coating were necessary for filament to grow. HMDSO plasma pretreatment could not only efficiently cover the matrix of 6016 aluminum alloy and cathodic intermetallic particles containing Al, Si, Mn, and Fe, but also apparently promote the adhesion of epoxy coating/aluminum alloy, as a result, the specimens with plasma pretreatment exhibited the superior performance in the filiform corrosion and peeling tests, so it was suitable to apply for the pretreatment of aluminum alloy in automotive industry.

Environmental degradation of epoxy–organoclay nanocomposites due to UV exposure. Part I: Photo-degradation

The environmental degradation mechanisms of epoxy–organoclay nanocomposites due to accelerated UV and moisture exposure are studied. Various characterisation tools, including FTIR, SEM, XRD and XRF analyses, were used to evaluate the effects of clay content on the progressive changes in chemical element, topography and colour of the nanocomposite. It is found that microcracks started to appear on both the neat epoxy and nanocomposite surface after about 300 h of UV exposure. The nanocomposite exhibited thicker and shallower cracks with a less degree of discoloration than the neat epoxy due to the diffusion barrier characteristics of organoclay with high aspect ratio. The presence of transition metal ions along with low-molecular-weight organic modifiers in organoclay, however, accelerated the degradation of polymer, counterbalancing the above ameliorating barrier properties of clay. FTIR analysis indicated that photo-degradation generated carbonyl groups by chain scission and the rate was slightly higher for the nanocomposites than for the neat epoxy. While moisture further accelerated the photo-degradation process through the enhanced mobility of free radicals and ions, the organoclay could limit the deteriorating effect of moisture, resulting in much better overall resistance to photo-degradation in the presence of moisture for the nanocomposite than the neat epoxy.

Enhancing polymer adhesion through surface activation using an in-line atmospheric pressure plasma

A reel-to-reel atmospheric pressure plasma treatment system known as Labline?, was used to activate the surface of Polypropylene (PP) and Polyethylene Terephthalate (PET). An epoxy adhesive was used to bond the activated polymers and the bond strength was assessed using the tensile lap shear test method. For PP treated in a helium discharge at 900 W a fivefold increase in adhesive bond strength was observed compared with that of the untreated polymer. The effect of adding nitrogen and oxygen into the helium plasma was examined, both with respect to the bond strength of the epoxy and polymer surface energy. An 18-fold increase in adhesive strength was observed after the treatment of PP in a helium/oxygen plasma, while a threefold increase was observed for PET. A similar increase in adhesion was observed for PET treated in a helium/nitrogen plasma, while a 16-fold increase in adhesion was obtained for PP.

Effect of fluorine functional groups on surface and mechanical interfacial properties of epoxy resins

To improve the surface and mechanical interfacial properties of epoxy resins, fluorine-containing epoxy resin (FEP) was prepared and blended with a commercially available tetrafunctional epoxy resin (TGDDM). As a result, when the fluorine content increased, the total surface energy of TGDDM/FEP blends was gradually decreased, while the water repellency of the blends was increased. The glass transition temperature and thermal stability factors of the blends showed maximum values at 20–40 wt% FEP compared with neat TGDDM epoxy resins. And the mechanical interfacial properties of the blend specimens were significantly increased with increasing the FEP content, which could be attributed to the intermacromolecular interactions in the cured TGDDM/FEP blends. These results indicate that the water repellency and toughness improvements have been achieved without significantly deterioration of the thermal properties in the TGDDM/FEP blends.

The role of castor oil in epoxy and polyamide systems for coating and adhesive application

Over the past few years, the challenges of globalisation, consolidation and economical point of view have meant that manufacturers of epoxy formulations have to constantly improve their capability to meet the needs of customers. An active area for advancement is that of epoxy and polyamide resin with castor oil. Generally, people working in the coating industries are familiar with castor oil, but this paper provides information on the new use of castor oil in epoxy and polyamide resin. This novel product (castor oil-modified epoxy resin/castor oil-modified polyamide) provides a previously unattainable combination and improved flexibility and toughness to a variety of ambient cure applications. This communication will review the performance of these castor oil-modified epoxy and polyamide resin surface coatings and adhesives. Based on the results of this study, these systems offer some advantages without much affecting the traditional properties of epoxy and polyamide resin in a variety of applications.

Chemical Modification of Buildup Epoxy Surfaces for Altering the Adhesion of Electrochemically Deposited Copper

The adhesion of electrochemically deposited copper on top of chemically surface modified epoxy layers for buildup purposes is examined. Using a wet-chemical surface synthesis reaction iminodiacetic acid, imidazole, and mercaptopyrimidine groups were chemically imprinted on the surface of buildup epoxy layers based on nucleofilic substitutions. The synthesis was followed by an identical electroless Cu deposition and peel strength measurement sequence. The identity of certain groups at the surface has pronounced influence on the adhesion strength of electrochemically deposited metals and is compared with traditional swell/oxidation treatments of the surface of the polymer. By varying the identity of the chemical groups at the surface, the chemical part of the adhesion can be altered. The changes in roughness of the polymer surface were minimized by choosing solvents that exhibit minimum diffusion into the polymer and by limiting the reaction temperature. In this way the changes in the physical part of adhesion could be kept to a minimum. The chemical composition of the surface is examined by attenuated total reflection-infrared and X-ray photoelectron spectroscopy measurements. Weight changes were recorded after each separate wet-chemical treatment. Surface synthesis influences the peel strength negatively or positively and modifies the deposition rate and etching speed of electrochemically deposited copper.

Amine-cured epoxy surface morphology and interphase with copper: an approach employing electron beam lithography and scanning force microscopy

The interphase between polymer and metal was investigated for further understanding of the mechanical properties. In particular, an analysis of the stiffness can provide significant information to determine the stress distribution in the interphase. The polymer–metal interphase was prepared by applying epoxy on micrometer-scale copper structures, which were created by electron beam lithography (EBL). The stiffness was characterized by force modulation microscopy (FMM), which is a scanning force microscopy (SFM)-based technique. According to the analysis, a stiffness variation was observed in the interphase. It showed a lower stiffness in the interphase than in the bulk epoxy, which is far from the copper structures. In addition, the morphology of epoxy surface was studied. The nodules on the epoxy surface were characterized and the average length was found to be approx. 76 nm. FMM showed adequate sensitivity to visualize the nodules on the epoxy. Therefore, FMM can also be a very effective method to analyze epoxy morphology and the stiffness in the interphase along with the topography images.

A flow simulation for the epoxy casting process using a 3D finite-element method

A three-dimensional flow simulation for epoxy casting has been developed. A control-volume-based finite-element method is employed, containing a conservative upwind formulation for the advection terms and equal order interpolations for all variables. This simulation predicts the non-isothermal and reactive flow behavior under the gravity. The viscosity and reaction-rate parameters were estimated by using a dynamic rheometer and a differential scanning calorimeter. The predicted flow front advancement and temperature profiles in the calculation domain similar to the mold cavity were in close agreement with the corresponding experimental results. The variation of epoxy surface configuration with flow rate also showed the same tendency between the prediction and the experiment. This simulation seems to be applicable not only to the epoxy casting, but also to other molding processes of various thermoset resins. POLYM. ENG. SCI. 45:364–374, 2005. © 2005 Society of Plastics Engineers.

Effect of surface treatment on the hydrolytic stability of E-glass fiber bundle tensile strength

The tensile strength of glass fiber bundles is highly dependent on flaw nucleation and growth from contact abrasion and hydrolytic degradation. The effect of fiber surface treatment on the hydrolytic stability of tensile strength is investigated for E-glass fiber bundles with four commercial sizings. Acoustic emission (AE) generated by individual fiber fracture events provides a means to determine a Weibull distribution of fiber strengths. Fiber bundles with starch, starch and silane, starch and wax, and epoxy surface treatments are tested following exposure to 10%, 40%, 80% relative humidity and immersion in water. The tensile break strength, number of breaks at peak load, and Weibull moduli of the glass fiber bundles are strongly dependent on the humidity level. The different surface treatments considered in this investigation strongly alter the absolute mechanical properties and the effect of exposure to humidity.

Fabrication of built-in copper microstructures on epoxy resin

This paper describes a simple and effective method to fabricate built-in copper microstructures on a polymer substrate. Our method uses a micropatterned amino (NH 2)-terminated self-assembled monolayer (SAM) as a template to fabricate patterned copper (Cu) film for transfer to an epoxy resin. Cu microstructures were first formed on a photolithographically micropatterned NH 2-SAM-covered SiO 2/Si substrate through conventional electroless plating, in which Cu deposition proceeded selectively on the NH 2-terminated areas while the photo-irradiated areas remained free of copper deposits. Next, epoxy glue (resin) was poured into a Teflon ® O-ring placed so as to surround the Cu-micropatterned substrate. Finally, after the resin completely hardened, it was removed from the substrate. Due to the weak adhesion between the Cu film and the NH 2-terminated surface, the area-selectively deposited Cu film could be readily peeled off and removed from the SiO 2/Si substrate and thus transferred to the resin surface. Through this technique, high-resolution 10-μm-wide Cu microstructures were successfully fabricated on the epoxy resin surface. These embedded Cu microstructures were tightly adhered to the resin. No peeling of the copper structures was observed in a Scotch ® tape peeling test.

AFM and impedance spectroscopy characterization of the immobilization of antibodies on indium–tin oxide electrode through self-assembled monolayer of epoxysilane and their capture of Escherichia coli O157:H7

The microscopic surface molecular structures and macroscopic electrochemical impedance properties of the epoxysilane monolayer and anti- Escherichia coli antibody layer on an indium–tin oxide (ITO) electrode surface were studied in this paper. Characterization of stepwise changes in microscopic features of the surfaces and electrochemical properties upon the formation of each layer were carried out using both atomic force microscopy (AFM) and electrochemical impedance spectroscopy in the presence of [Fe(CN) 6] 3−/4− as a redox couple. AFM images of the self-assembled monolayer (SAM) evidenced the dense, complete, and homogeneous morphology of the epoxysilane monolayer on the ITO surface. The uniformity of the epoxysilane SAM allowed antibodies to attach to the epoxy surface groups of the silanes in a similarly uniform fashion. The effects of epoxysilane monolayer and the antibody layer on the electrochemical properties of the electrode were quantitatively analyzed in terms of double layer capacitance, electron transfer resistance, Warburg impedance and solution resistance using Randles model as the equivalent circuit. It was demonstrated that the epoxysilane monolayer and the antibody layer act as barriers for the electron transfer between the electrode surface and the redox species in the solution, resulting in most significant increases in the electron transfer resistance compared to all the electric elements. Immunoreaction with E. coli O157:H7 cells demonstrated specific recognition of the immobilized anti- E. coli antibodies as evidenced by AFM imaging and impedance spectroscopy. It was found that the binding of E. coli cells mainly affected the electron transfer resistance and Warburg impedance.

Synergistic interaction of topographic features in the production of bone-like nodules on Ti surfaces by rat osteoblasts

The objective of this study was to study the responses of osteoblast-like cells to rough Titanium (Ti)-coated epoxy surfaces of differing topographic complexity. Four topographies were studied: polished (PO), coarse-blasted (CB), acid-etched (AE) and coarse-blasted+acid-etched (SLA). Rat osteoblasts were cultured on these surfaces and their morphology, thickness as well as the number and size of bone-like nodules measured. To determine cell shape and cell thickness, fluorescein-5-thiosemicarbazide was used to stain the cell components including the cell membrane, the stained cells were optically sectioned using epifluorescent microscopy and the optical sections were computationally reconstructed to obtain three-dimensional images in which cell volume and cell thickness could be determined. Similarly optical sections of bone-like nodules labeled with tetracycline were also reconstructed to determine their size. The different surface topographies were found to alter the thickness and morphology of osteoblasts cultured on these surfaces. Osteoblasts produced significantly more and larger nodules on SLA compared to other surfaces . Nevertheless and perhaps surprisingly, given the evidence in various cell populations that cell shape can affect cell differentiation, cell thickness was not directly correlated with an increase in bone-like nodule formation. Data were analyzed by factorial analysis of variance. In this way the primary effect of each surface treatment ( i.e. blasting and acid etching) could be assessed as well as their interaction. Both the acid etching and blasting processes significantly affected the number and size of bone-like nodules cultured on Ti surfaces. Moreover there were significant interaction effects indicating that surface topographic features can act synergistically to enhance bone formation. This result suggests that a useful approach to the optimization of surfaces for bone production could involve systematic investigation of combinations of processes each of which produces distinct surface topographical features.