Significant Adhesion Enhancement Research Articles

Interleukin-6 Enhances Whereas Tumor Necrosis Factor α and Interferons Inhibit Integrin Expression and Adhesion of Human Mast Cells to Extracellular Matrix Proteins

Integrins are expressed on mast cells and constitute an essential prerequisite for the accumulation of the cells at sites of inflammation. In order to clarify a potential contribution of inflammatory cytokines to this process, we have studied the modulation of integrin expression and adhesion of immature human mast cells (HMC-1) to extracellular matrix proteins by interleukin-6, tumor necrosis factor alpha, interferon-alpha and interferon-gamma. Corticosteroids were used for comparison. On fluorescence-activated cell sorter analysis, preincubation of cells for 48 h with different concentrations of interleukin-6 induced a significant, up to 40%, increase of alpha v alpha 5, CD49b (alpha 2), CD49e (alpha 5), CD49f (alpha 6), and CD51 (alpha v). In contrast, different concentrations of tumor necrosis factor alpha, interferon-alpha, interferon-gamma, and dexamethasone (10-8-10-10 M) inhibited expression of adhesion receptors by up to 60%, reaching significance for some but not all integrins. On semiquantitative polymerase chain reaction analysis, interleukin-6, the other cytokines, and corticosteroids significantly modulated expression of alpha1, alpha v and alpha 5 integrin chains at mRNA level. Functional significance of these findings was proven in adhesion assays using fibronectin, laminin, and vitronectin, with interleukin-6 causing significant enhancement of adhesion in all cases, tumor necrosis factor alpha and dexamethasone inducing significant reduction of adhesion to fibronectin and laminin, and interferon-gamma significantly inhibiting adhesion to fibronectin only. Specificity of interleukin-6-induced changes was demonstrated using antibodies against alpha1 and alpha 5 integrins in unstimulated and interleukin-6-prestimulated cells. These data show that interleukin-6 stimulates mast cell adhesion to extracellular matrix and thus allows for the accumulation of the cells at tissue sites by enhancing integrin expression, whereas tumor necrosis factor alpha, interferon-alpha, interferon-gamma, and dexamethasone downmodulate this process.

An interfacial study of a hydrogenated carbon interlayer for adhesion enhancement of plasma deposited silica thin films on polycarbonate

This work presents a new plasma treatment for the adhesion enhancement of a plasma deposited silica layer to polycarbonate. After initial oxygen plasma treatment of the polycarbonate surface, a thin hydrogenated amorphous carbon layer is deposited before the silica layer. This interlayer is found to increase the number of Si—O—C bonds at the interface. The treatment leads to a significant adhesion enhancement of the silica layers and to increased resistance to temperature changes and moisture.

Adhesion studies using contact mechanics

AbstractWe report adhesion studies using the JKR contact mechanics method and poly(dimethylsiloxane) (PDMS) cross‐linked networks. When such networks are extracted, interdigitation of tethered chains into extraction zones at the network‐network interface results in a significant enhancement of adhesion. When these networks come into contact with a silicon oxide surface, an increase in adhesion hysteresis is observed in the order of increasing molecular weight between crosslinks, with a scaling factor of 1/2. Subjecting the system to maximum load for 30 min before unloading results in a scaling factor of 1/3, probably due to molecular weight dependent network relaxation rates. PDMS cross‐link networks form H‐bonds with surface Si–OH groups that result in significant and time‐dependent adhesion increase. Systematic studies of interfacial H‐bonding and its effect on adhesion have been carried out using self‐assembled monolayer (SAM) surfaces. An increase in adhesion strength was observed in the order of increasing acidity of surface OH protons [Au/S(CH2)11OH < Au/S(C6H4)2OH < Au/S(CH2)15COOH < Au/S(CH2)11PO(OH)2]. When surface OH concentration was controlled, the strength of adhesion was found to be proportional to the number of surface OH groups, with nonlinear relationship, probably due to the collective nature of H‐bonding between the PDMS chain and surface OH groups. Isotope effect studies confirmed the formation of interfacial H‐bonding.

POLYMER-POLYMER ADHESION IN MELT-PROCESSED LAYERED STRUCTURES

Improving the adhesion of polyolefins to glassy polymers is complicated by the semicrystalline nature of the polyolefins. Traditional methods used in glassy polymers to increase the interlayer adhesion, including the addition of a diblock copolymer or the formation of a copolymer through in situ reaction, are still successful with semicrystalline polymers. However, melt miscibility of the adhesion promoting molecules is no longer sufficient; they must also co-crystallize. Even when co-crystallization is achieved, the reactive method is shown to provide greater fracture toughness than the addition of a pre-made diblock copolymer. In the latter case, the formation of micelles limits the efficiency of the diblock copolymer. Finally, significant adhesion enhancement is attainable in reactive systems with contact times as short as 45 seconds as demonstrated through a multilayer coextrusion of amorphous nylon against a polypropylene-maleated polypropylene blend.

Adhesion Enhancement Via Crystalline-Embedded Entanglements in Melt-Processed Layered Structures

ABSTRACTImproving the adhesion of polyolefins to glassy polymers is complicated by the semicrystalline nature of the polyolefins. Traditional methods used in glassy polymers to increase the interlayer adhesion, including the addition of a diblock copolymer or the formation of a copolymer throughin situreaction, are still successful with semicrystalline polymers. However, melt miscibility of the adhesion promoting molecules is not the only consideration; co-crystallization can also be significant. Even when co-crystallization is achieved, the reactive method is shown to provide greater fracture toughness than the addition of a pre-made diblock copolymer. In the latter case, the formation of micelles limits the efficiency of the diblock copolymer. Finally, significant adhesion enhancement is attainable in reactive systems with contact times as short as 45 seconds as demonstrated through a multilayer coextrusion of amorphous nylon against a polypropylene-maleated polypropylene blend.

Marine microbial aggregating macromolecules: Potential mediators of coastal carbon flux

Microbial aggregation‐adhesion enhancing macromolecules (AAEM) in high molecular weight materials (HMWM) recovered from coastal seawater, suspended particulates and sediments were isolated using immunoaffinity chromatography. The quantity of AAEM recovered was an order of magnitude higher in suspended particulates compared to seawater and sediments. However, the AAEM/HMWM ratio remained constant in samples from all three sources. The fulvic acid component of suspended particulates had 91% of the AAEM, compared to 59% in the sediments. This change in AAEM distribution was directly correlated with decreased amounts of the predominant AAEM molecular size present in the sediment samples. Spectroscopic (FTIR) analyses revealed that the reduction in the relative quantities of fulvic acid AAEM in the sediment was most likely due to oxidative degradation of these residues. While significant adhesion enhancement activity was detected in both fulvic and humic acid AAEM fractions in sediments, the fulvic acid AAEM was significantly more active than the humic acid component. Fulvic and humic acid AAEM activity was strongly conserved in sediments despite reductions in quantity and oxidative degradation, indicating that these materials may play an important role in microbial organic carbon flux in this tropical coastal marine environment.

Use of coupling agents for internally reinforced rayon fibers

Two difunctional, sterically hindered compounds, 1,4-bis(3-aminopropyldimethylsilyl)-benzene and fumaric acid, were evaluated as possible coupling agents for composite skin-core textile fibers. Other silane coupling agents and surface treatments had been tried previously. The fibers were formed using a process similar to wire coating in which a commercially produced nylon 66 monofilament core fiber, pretreated with coupling agent, contacted a viscose rayon solution in the die. Subsequently, the coated fiber was passed through a sulfuric acid coagulation bath, water wash, and dryer. The coupling agent concentration and coating line speed were evaluated for their effect on enhancement of adhesion. The composite fibers were stitched into a carrier fabric which was subsequently abraded in an Accelerotor to test the effect of the variables on adhesion of the skin to the core. Certain combinations of line speed, concentration, and type of coupling agent were found to provide significant enhancement of adhesion ...

Microstructural and chemical characterization of ion beam mixed Fe/Al 2O 3 interface; effect on adhesion enhancement

Metallic iron layers (~ 60 nm) deposited on sapphire substrates have been mixed at room temperature with various ions (Ne, Ar, Kr, Xe) in wide dose and energy ranges. Microstructural characterization of the interface has been performed at the atomic scale using high-resolution transmission electron microscopy observations on cross-sectioned samples. Complementary measurements with conversion electron Mössbauer spectrometry (CEMS) and X-ray photoelectron spectrometry (XPS) give chemical information on the nature of the nonequilibrium phases formed at the interface. The mixed zone at the interface concerns few atomic planes and no long-range diffusion takes place at room temperature in those metal-ceramic systems. A significant enhancement of adhesion has been measured by the pin pull test for the mixed samples with a strong dependence on the energy deposition at the interface. These results will be discussed taking into account the microstructural and physicochemical aspects as well as the energy deposition in individual cascades during the primary ballistic phase (~ 10 −13 s) of the ion beam mixing process.

Influence of 27Al+ ion mixing on the adhesion and interfacial chemistry of Ni films on polyimide and polyester

In order to evaluate the influence of ion chemistry on ion-induced interfacial chemistry and thin film adhesion, 30 nm Ni films on polyester (PET) and polyimide (PI) substrates were implanted with various doses (1-10 x 1016 Al/cm2) of 50 keV 27Al+. The ion-induced interfacial chemistry and adhesion were then examined using X-ray photoelectron spectroscopy (XPS) and scratch testing, respectively. The implantation induced extensive interfacial mixing in both types of specimens. In addition, the implanted Al reacted with oxygen in the polymer substrates to form interfacial Al2O3 and Al-O-C layers in the Ni/PET and Ni/PI specimens, respectively. Despite the ion-induced interfacial mixing and compound formation, the scratch testing indicated that no significant adhesion enhancement was produced by the 27 Al+ ion mixing. The absence of adhesion enhancement was attributed to the absence of complete chemical bonding between the Ni films and the polymer substrates. Criteria for the selection of an effective reactive ion for adhesion enhancement in a given film/substrate system are discussed.