The effect of activated fillers on the properties of styrene–acrylic adhesives

Results of kaolin modification by thermal activation, sonication and 3% solution of acetic acid are considered. It is shown that the introduction of thermally activated kaolin to compositions based on styrene–acrylic filming agents increases the adhesion characteristics by 1.25–1.4 times (for steel and cement–sand surfaces) and cohesive strength by 1.5–2 times.     

A comparative study on chemical treatment of jute fiber: potassium dichromate, potassium permanganate and sodium perborate trihydrate

Studies have been carried out on chemical treatments of jute fibers in order to hinder moisture absorption, which causes incompatibility with a non-polar polymer, and to increase the surface roughness for mechanical interlocking. The objective of this research is to improve the interfacial adhesion between jute fibers and polypropylene by oxidative treatments. On this basis, jute fibers were treated with potassium dichromate (PD), potassium permanganate (PM) and sodium perborate trihydrate (SP). Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy were used to characterize jute fibers. The effects of chemical treatments were also revealed by assessment of moisture absorbability, yarn tensile properties and interfacial shear strength with polypropylene. FTIR and XPS analyses confirmed oxidative modification of jute fibers using any of the surface treatments. It was observed that the proportion of O=C groups increased, whereas that of O–H groups decreased after oxidative modifications. Tensile strength and elasticity modulus results decreased after oxidative treatments, whereas PD, PM and SP enhanced the interfacial shear strength values by 25, 61 and 71 %, respectively. Only SP treatment influenced moisture absorbability results significantly. The surface roughness of untreated jute fibers shows increments after chemical treatments due to partial removal of surface cementings. According to the findings obtained from surface characterization methods and physical tests, the highest interfacial adhesion with better compatibility with polypropylene was achieved after SP treatment by providing the highest surface roughness values and hydrophobic character of jute fiber.     

Heterogeneous partial oxidation catalysis on metal oxides

This review paper presents an overview of heterogeneous selective ammoxidation and oxidative dehydrogenation (ODH) of light alkanes, particularly of ethane. The conversion of ethane to ethene is in great demand in the domestic and worldwide chemical industry. The review has been voluntarily restricted to metal oxide-type catalysts, as it is devoted to the special issue honouring Edmond Payen and is based on 30 years of experience and discussions with pioneering scientists in the field. The main key factors, designated by Grasselli as the “7 pillars”, have been emphasised: isolation of active sites, M–O bond strength, crystalline structure, redox features, phase cooperation, multifunctionality and the nature of the surface oxygen species. The main features and physical and chemical properties of solid catalysts for selective oxidation compared to total oxidation have also been emphasised. Several case studies have been presented to illustrate the concept and importance of the key factors of catalyst preparation and activation and of the catalytic atmosphere. Based on such analysis and recent discoveries and process developments perspective views are also given.     

Surface structural and energetic heterogeneity of carbon materials prepared from corn grains using steam and H3PO4‐steam activations

The porous activated carbons (ACs) were prepared from corn grains through physical (steam) and chemical–physical (H₃PO₄‐steam) activations. The effects of steam activation temperature (700–900 °C) on pore development, surface roughness, and energetic heterogeneity were investigated in both activations. Also, the effect of prior carbonization on H₃PO₄‐steam activation was studied. The physical properties, surface fractal dimensions, and adsorption energy distributions of ACs were determined from nitrogen adsorption–desorption isotherm data. Both physical and chemical–physical activations show that the AC with higher surface area, relatively smoother surface, and energetically heterogeneous surface could be produced at a maximum steam activation temperature (900 °C). Copyright © 2015 John Wiley & Sons, Ltd.     

Chemical and structural changes at the ABS polymer-copper metal interface

Creating oxygen containing moieties (hydroxyl or carbonyl) on polymer substrate surfaces is known to increase the adhesion strength of polymers to metals. However, we noticed adhesion increase with time even though no pre- or post-treatment of the polymer substrate was done. In the case of sputtered and galvanically strengthened copper coatings on acrylonitrile-butadiene-styrene polymer (ABS) substrate, the adhesion strength increased from approximately 6 J/m² to 53 J/m² during a 1008-h period. During this period structural and chemical changes of the polymer near the interface take place. Carbonyl functionalities developed on the ABS surface are most likely responsible for the large increase in the adhesion strength. Chemical changes of the polymer are probably a consequence of the galvanic deposition and a close contact of ABS with copper which is known to facilitate the oxidation of ABS.     

Surface modification of ultrahigh‐molecular‐weight polyethylene fibers

To prevent the loss of fiber strength, ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona‐discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE‐fiber‐reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6‐kW corona treatment, the T‐peel strength of the treated UHMWPE‐fiber composite was one to two times greater than that of the as‐received UHMWPE‐fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 463–472, 2004     

Surface grafting of a thermoplastic polyurethane with methacrylic acid by previous plasma surface activation and by ultraviolet irradiation to reduce cell adhesion

The material performance, in a biological environment, is mainly mediated by its surface properties and by the combination of chemical, physical, biological, and mechanical properties required, for a specific application.In this study, the surface of a thermoplastic polyurethane (TPU) material (Elastollan^®1180A50) was activated either by plasma or by ultra-violet (UV) irradiation. After surface activation, methacrylic acid (MAA) was linked to the surface of TPU in order to improve its reactivity and to reduce cell adhesion. Grafted surfaces were evaluated by X-ray photoelectron spectroscopy (XPS), by atomic force microscopy (AFM) and by contact angle measurements. Blood compatibility studies and cell adhesion tests with human bone marrow cells (HBMC) were also performed.If was found that UV grafting method led to better results than the plasma activation method, since cell adhesion was reduced when methacrylic acid was grafted to the TPU surface by UV.     

Preparation and properties of poly(dimethysilyleneethynylenephenylene‐ethynylene)/graphene Composites

Polymer composites with carbon‐based nano‐fillers have generated significant interest in industry and science because of their multifunctional and valuable properties. An APA‐functionalized GO nanofiller (GO–APA) was prepared through the reaction between graphene oxide (GO) and 3‐aminophenyl acetylene (APA) in dimethylformide (DMF) with ammonia hydroxide. Furthermore the PDSEPE/GO–APA composites were made from Poly(dimethysilyleneethynylenephenylene ethynylene) (PDSEPE) and GO–APA. FT‐IR, XRD, XPS, SEM, DSC and TGA techniques were used to characterize the chemical compositions and physical and chemical properties of GO–APA and PDSEPE/GO–APA composites. As a result, the prepared PDSEPE/GO–APA composites show high thermal stabilities, excellent electrical conductivity and good flexural strength. When the weight percentage of GO–APA reaches 0.5%, the PDSEPE/GO–APA composite electrical conductivity increases by 6 orders of magnitude and the flexural strength improves by nearly 33% compared with that of cured PDSEPE resin. Copyright © 2015 John Wiley & Sons, Ltd.     

Surface modification of a liquid‐crystalline polymer for copper metallization

The effects of different surface modifications on the adhesion of copper to a liquid‐crystalline polymer (LCP) were investigated with X‐ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, contact‐angle measurements, and pull tests. High pull‐strength values were achieved when copper was sputter‐deposited onto plasma and reactive‐ion‐etching (RIE)‐pretreated LCP surfaces. The values were comparable to the reference pull strengths obtained with laminated copper on the LCP. The adhesion was relatively insensitive to the employed feed gas in the pretreatments. The surface characterizations revealed that for RIE and plasma treatments, the enhanced adhesion was attributable to the synergistic effects of the increased surface roughness and polar component of the surface free energy of the polymer. However, if the electroless copper deposition was performed on RIE‐ or plasma‐treated surfaces, very poor adhesion was measured. Good adhesion between the LCP substrate and electrolessly deposited copper was achieved only in the case of wet‐chemical surface roughening as a result of the creation of a sufficient number of mechanical interlocking sites, together with a significant loss of oxygen functionalities, on the surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 623–636, 2003     

Quantitative changes in the elasticity and adhesive properties of Escherichia coli ZK1056 prey cells during predation by bdellovibrio bacteriovorus 109J

Atomic force microscopy (AFM) was used to explore the changes that occur in Escherichia coli ZK1056 prey cells while they are being consumed by the bacterial predator Bdellovibrio bacteriovorus 109J. Invaded prey cells, called bdelloplasts, undergo substantial chemical and physical changes that can be directly probed by AFM. In this work, we probe the elasticity and adhesive properties of uninvaded prey cells and bdelloplasts in a completely native state in dilute aqueous buffer without chemical fixation. Under these conditions, the rounded bdelloplasts were shown to be shorter than uninvaded prey cells. More interestingly, the extension portions of force curves taken on both kinds of cells clearly demonstrate that bdelloplasts are softer than uninvaded prey cells, reflecting a decrease in bdelloplast elasticity after invasion by Bdellovibrio predators. On average, the spring constant of uninvaded E. coli cells (0.23 +/- 0.02 N/m) was 3 times stiffer than that of the bdelloplast (0.064 +/- 0.001 N/m) when measured in a HEPES-metals buffer. The retraction portions of the force curves indicate that compared to uninvaded E. coli cells bdelloplasts adhere to the AFM tip with much larger pull-off forces but over comparable retraction distances. The strength of these adhesion forces decreases with increasing ionic strength, indicating that there is an electrostatic component to the adhesion events.     

Biocompatible,transparent, and water-resistant adhesive films with high mechanical stability derived from post-facile chemical cross-linking

Transparent surgical adhesives with excellent underwater adhesion and mechanical strength are strongly desirable for various biomedical applications such as wound closure and tissue healing. This is addressed in the present work by the development of biocompatible, transparent, and water-resistant adhesive films prepared from catechol-modified ε-poly(ʟ-lysine) and dopamine hydrochloride modified sodium hyaluronate layers successively applied using the layer-by-layer (LbL) assembly method. The LbL-assembled films are easily released from substrates via a mechanical exfoliation method with a blade to obtain free-standing multilayer films. The exceptional wet adhesion properties of the catechol groups yield films with excellent underwater adhesion strength. The underwater stability and mechanical strength of the free-standing multilayer films are improved via post-facile chemical cross-linking using biocompatible N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride. The post-treated free-standing multilayer films achieve a tensile strength of 0.36 ± 0.20 MPa and an elongation at break of 180.05% in water. The free-standing multilayer films exhibit a high optical transmittance greater than 55% in the visible region.     

Identifying promising metal–organic frameworks for heterogeneous catalysis via high-throughput periodic density functional theory

Metal–organic frameworks (MOFs) are a class of nanoporous materials with highly tunable structures in terms of both chemical composition and topology. Due to their tunable nature, high-throughput computational screening is a particularly appealing method to reduce the time-to-discovery of MOFs with desirable physical and chemical properties. In this work, a fully automated, high-throughput periodic density functional theory (DFT) workflow for screening promising MOF candidates was developed and benchmarked, with a specific focus on applications in catalysis. As a proof-of-concept, we use the high-throughput workflow to screen MOFs containing open metal sites (OMSs) from the Computation-Ready, Experimental MOF database for the oxidative C—H bond activation of methane. The results from the screening process suggest that, despite the strong C—H bond strength of methane, the main challenge from a screening standpoint is the identification of MOFs with OMSs that can be readily oxidized at moderate reaction conditions. © 2019 Wiley Periodicals, Inc.     

Towards scalable production of polyamide 12/halloysite nanocomposites via water‐assisted extrusion: mechanical modeling,thermal and fire properties

In this study, polyamide 12 (PA12)/untreated halloysite nanotubes (HNTs) nanocomposites are prepared in a semi‐industrial scale extruder using a non‐traditional “one step” water‐assisted extrusion process. A morphological study is carried out using a combination of scanning electron microscopy and transmission electron microscopy analyses to evaluate the influence of water injection and filler content on the quality of clay dispersion. The use of water injection slightly improves the nanoscale dispersion at low HNTs content (<8 wt.%), while this effect is more pronounced at higher filler loading (16 wt.%). A mechanism explaining the physico‐chemical action of water during extrusion is proposed. The materials are characterized with respect to their mechanical, thermo‐mechanical, thermal and fire properties. A strong correlation is found between nanostructure and physical properties; the more uniform dispersion of the clay nanotubes, the higher mechanical reinforcement, thermal stability and fire retardancy of PA12 nanocomposites. Tensile tests results are interpreted in terms of three mechanical models: the Halpin–Tsai's model for stiffness and the interfacial strength model and the Pukanszky's equation for yield strength. Linear fits of the experimental data confirm that the superior reinforcement of nanocomposites prepared using water injection results from improved clay dispersion and better interfacial adhesion between PA12 and HNTs. In view of these promising results, the proposed direct melt compounding method could be easily scaled‐up towards the production of PA12–HNTs nanocomposites at an industrial scale. Copyright © 2013 John Wiley & Sons, Ltd.     

Study of the carbon fiber–poly(ether–ether–ketone) (PEEK) interfaces, 2: relationship between interfacial shear strength and adhesion energy

In the second part of this general study, the carbon fiber–PEEK interfacial shear strength is measured by means of a fragmentation test on single-fiber composites. Different thermal treatments (continuous cooling from the melt, isothermal treatments and long melting temperature time) are applied to these model composites prior to testing. The results are systematically compared with the previously determined reversible work of adhesion between carbon fiber and PEEK. It is shown that physical interactions at the interface determine, to a large extent, the magnitude of the interfacial shear strength between both materials. However, it appears that the magnitude of the stress transfer from the matrix to the fiber is affected either by the existence of an interfacial layer or by a preferential orientation of the polymer chains near the fiber surface. The results obtained on systems that have been subjected to isothermal treatments (isothermal crystallization of PEEK) seem to confirm the existence of a transcrystalline interphase, the properties of which are dependent upon the crystallization rate of the matrix and the interfacial adhesion energy.     

Optimized methods for preparing activated carbon from rock asphalt using orthogonal experimental design

Journal of Thermal Analysis and Calorimetry - This work evaluated three activation methods, physical activation, chemical activation and combined physical–chemical activation, for preparing...     

Adhesion maps of spheres corrected for strength limit

Present understanding of adhesion is mostly due to the well-known contact theories for spheres, including JKR (Johnson-Kendall-Roberts), DMT (Derjaguin-Muller-Toporov) and MD (Maugis-Dugdale). Since most of the models exhibit their optimal applicability only in a specific regime, an adhesion map has been developed [K.L. Johnson, J.A. Greenwood, J. Colloid Interface Sci. (1997)] to guide the selection among different models. In the JG (Johnson-Greenwood) map, however, an important physical fact has been neglected that the adhesion strength must not exceed the theoretical strength; thereby the applicability of the classical adhesion models is overestimated and misguidance may arise from the JG map. To avoid this limitation, in this paper we introduce the strength limit into the adhesion map and find that the selection of adhesion models depends not only on the Tabor number but also on the ratio of the theoretical strength to the stiffness. Given this ratio, there exists a critical Tabor number or the size of the sphere, below which adhesion is dominated by the limiting strength and the classical adhesion models are no longer appropriate for spheres. These results eventually lead to a corrected adhesion map for spheres.     

Problems of adhesion strength in epoxy-allylic polymer-polymer systems

The main aspects of the problems associated with adhesion and adhesion strength, as well as the factors causing formation of boundary layers (BLs), are discussed. The results of studying the effect of various factors (the ratio between EA polymer components, the chemical structure of curing agents, and curing modes) on the formation of BLs and adhesion strength of adhesive substances are reported by the example of epoxy-allylic (EA) polymer-polymer systems are reported.     

Characterization of new natural cellulosic fiber from the Ipomoea staphylina plant

Natural fibers extracted from plants play a major role as reinforcement in polymer composite materials due to their superior properties. This work aims to comprehensively characterize the physical and chemical properties of Ipomoea staphylina fibers (ISFs), which are extracted from the stem of the Ipomoea staphylina plant. The ISFs show cellulose content (72.76 wt%), hemicelluloses content (13.6 wt%), density (1401 kg cm^?3), and tensile strength of 173–658 MPa with a strain rate of 2.03–6.63%. The thermal stability of ISFs illustrate that the fibers are stable up to a temperature of 311°C with kinetic activation energy of 99.82 kJ mol^?1.     

Chelates of Metals as Adhesion Promotors in Adhesive Compositions Based on Butadiene–Nitrile Rubber

The influence of chelates—complex compounds of various metals and phenol–formaldehyde resins as adhesion promotors—on the properties of adhesive compositions based on butadiene-nitrile rubber is considered. When using them, the strength of fabric–fabric bonds is increased by 150–250% and that of rubber–rubber and rubber–fabric ones by 100%.     

Porcelain tile surface modification with isocyanate coupling agent: interactions between EVA modified mortar and silane improving adherence

Adhesion between tiles and mortar is of paramount importance to the overall stability of ceramic tile systems. The interfaces between ceramic tiles and polymer‐modified Portland cement mortar are derived from several physical and chemical phenomena that take place during their formation. From the chemical perspective, weak forces are expected to occur preferably at the tiles and polymer‐modified Portland cement mortar interfaces. Therefore, the purpose of this study was to promote a new chemical functionalization of ceramic tile surfaces by modifying with isocyanate‐trialkoxysilane coupling agent in order to enhance the interfacial adhesion with poly (ethylene‐co‐vinyl acetate), EVA, polymer‐modified mortar. Pull‐off tests and Fourier Transformed Infrared Spectroscopy (FTIR), using the Attenuated Total Reflectance method, were carried out in order to characterize the system. The bond strength results have provided evidence toward improvements in adherence at the tile–polymer modified mortar interface, thus reflecting the development of urethane linkages between silane and EVA polymer, as detected by FTIR. Copyright © 2010 John Wiley & Sons, Ltd.