Adhesion strength and fracture behavior between carbon black-filled rubber sheets

Adhesion behavior at the interface between a partially-crosslinked and a fully-crosslinked sheet of carbon black-filled rubber compound was investigated over a temperature range from 30 to 120°C. The values of adhesion fracture energy G_a were compared with those of cohesive tear energy G_c. A considerable chemical, as well as physical, interfacial bonding is formed when the uncrosslinked or partially-crosslinked sheet is crosslinked in contact with even a fully-crosslinked sheet. However, there is only a small possibility of chemical bonding when the two fully-crosslinked rubber layers are again crosslinked in contact with each other. An interesting failure mode, termed 'interfacial knotty tearing' was found for a strain-induced crystallizable natural rubber.     

Combustion and decomposition of VOCs from shell moulds by regenerative thermal oxidiser

Abstract

In the present work, the regenerative thermal oxidiser (RTO) with preheating and baking system was applied to treating volatile organic compounds (VOCs) discharged from the shell mould casting. As a result, it was found that the tar characterised by more than 523 K of high boiling point was formed by the shell mould casting. The Fourier transform infrared spectrometry analysis showed that the tar was composed of paraffin, zinc stearate and quartz. A part of the tar was deposited on the ceramic honeycombs in the heat exchanger. However, the tar can be almost completely removed by means of baking treatment at 623 K in the RTO. Regarding the decomposition of VOCs, it was found that the concentrations of all VOCs were reduced to less than 1 ppm. Further, 98% of offensive odour was removed by the treatment. Thus, it can be concluded that the RTO is suitable for decreasing VOCs from the shell mould casting in the foundry.     

Laser pressure welding of Al alloy and low C steel

Abstract

This study was performed to obtain fundamental knowledge concerning the development of laser pressure welding technology for the joining of dissimilar metals. Laser pressure welding of Al alloy A6061 and low C steel SPCC sheets was carried out to investigate the effects of the roller pressure, laser beam scanning speed and irradiation position on the tensile shear and peel strength of welded joints. The interfaces of the joints were observed and analysed by SEM and EDX, and the formation phases on the peeled surfaces were identified with XRD. It was revealed that prevention and suppression of oxidation during welding was extremely important to the production of a sound joint with good mechanical properties. The highest tensile strength and the highest peel strength of joints were obtained at a laser power of 1·8 kW, laser scanning speed of 30 Hz, laser irradiation position at the centreline, roller pressure of more than 245 MPa and welding speed of 0·5 m min^?1 in an Ar atmosphere. The fracture occurred not in the welded zone but in the A6061 base alloy specimen.     

Vacuum hot roll bonding of titanium alloy and stainless steel using nickel interlayer

Abstract

Vacuum hot roll bonding of titanium alloy and stainless steel using a nickel interlayer was investigated. No obvious reaction or diffusion layer occurs at the interface between stainless steel and nickel. The interface between titanium alloy and nickel consists of an occludent layer and diffusion layers, and there are the intermetallic compounds (TiNi₃, TiNi, Ti₂Ni and their mixtures) in the layers. The total thickness of intermetallic layers at the interface between titanium alloy and nickel increases with the bonding temperature, and the tensile strength of roll bonded joints decreases with the bonding temperature. The maximum tensile strength of 440·1 MPa was obtained at the bonding temperature of 760°C, the reduction of 20% and the rolling speed of 38 mm s^–1.     

Wear behaviour of Fe/M7C3 metal matrix composites with various microstructures during dry sliding

Abstract

The wear mechanisms of iron based metal matrix composites and the wear behaviours of various microstructures were systematically studied by dry sliding wear testing and SEM examination. The experimental results show that three dominant wear mechanisms appeared in succession with increasing normal load during dry sliding. The transition of the wear mechanisms depended mainly upon the conditions of testing, and additionally it was seen that changes in microstructure of the steel had no marked effect on the transition. In the case of mild wear, no obvious differences in wear volume were found for the various microstructures. However, considerable differences in the wear volumes were observed under conditions of severe wear characterised by adhesion and delamination. The experimental results also indicate that the differences in wear resistance of the various microstructures were caused by differences in microstructural thermal stability, resistance to plastic deformation, resistance to nucleation and propagation of microcracks and especially by differences in energy consumption in these layers during wear.     

40—SELF-CROSS-LINKING IN HEATED KERATIN

An account is given of an investigation of the influence of dry heat on wool keratin. It is shown by three different chemical techniques that cross-linking occurs up to a temperature at which the amino-acid decomposition becomes marked. Although Iysinoalanine and lanthionine are shown to be formed, these amino acids do not appear to be major contributors to the cross-linking of the heated protein.

The covalent binding of the ?-amino group of lysine was determined quantitatively, and, from the results obtained, it is deduced that this group is involved to a large extent in the formation of cross-links.

On the basis of these findings, it is postulated that amide cross-links are formed through the ?-amino group of lysine by reaction with carboxylic side chains of aspartic or glutamic acids or their amide derivatives.     

Effects of boron compounds on the bonding strength of phenol-formaldehyde and melamine-formaldehyde adhesives to impregnated wood materials

Wood materials are increasingly being used in the construction of structural beams, sports equipment, etc. This study was carried out to determine the bonding strength of phenol-formaldehyde (PF) and melamine-formaldehyde (MF) adhesives to impregnated wood materials. For this purpose, brutia pine (Pinus brutia Ten) and elm (Ulmus compestris L.) woods were impregnated with borax (Bx), boric acid (Ba), Bx + Ba (wt:wt 50:50%), di-ammonium phosphate (D), [D + (Bx + Ba)]/(50 + (25 + 25%), w/w) and Tanalith-C 3310 (T-C 3310) using the vacuum method according to ASTM-D 1413-76. The effects of wood species, impregnating material and type of adhesive on the bonding strength were determined. The highest shear strength (11.09 N/mm²) was obtained from elm wood control (i.e., without any impregnating materials) samples with MF; thus, the impregnation process negatively affected the adhesive bonding strength. Impregnating materials, especially those containing oily or similar solutions such as T-C 3310, are not advised for wood elements which are subjected to shear.     

Atmospheric-Pressure Plasma Amination of Polymer Surfaces

Using dielectric barrier discharges (DBDs) in suitable gas atmospheres, appreciable densities of amino groups can be generated on polymer surfaces. After the introduction and a few remarks on analytical methods for the determination of functional groups densities, this paper presents a short summary of recent studies on the mechanism of the polymer surface amination from nitrogen and nitrogen/hydrogen mixtures, and possible relevant precursor species. Combination of chemical derivatization with quantitative FT-IR spectroscopy was employed for the determination of primary amino groups densities introduced on polyolefin surfaces in DBD afterglows in N₂ and N₂ + H₂ mixtures. Owing to the possibility to generate atmospheric-pressure plasmas in sub-mm³ volumes, DBD plasmas can be used to modify polymer surfaces area selectively: a new process termed 'plasma printing' can be applied for the achievement of micropatterned surface modifications, such as hydrophilization/hydrophobization or chemical functionalization. Direct-patterning polymer surface modification processes are of interest for biochemical/biomedical applications as well as for polymer electronics. Two examples are presented in more detail: ? the area-selective plasma amination of carbon-filled polypropylene minidiscs to manufacture microarrays with peptide libraries utilizing parallel combinatorial chemical synthesis, and ?the continuous treatment of polymer foils by means of reel-to-reel patterned plasma amination for the subsequent electroless copper metallization, leading to a fast and highly efficient process for the manufacture of structured metallizations for flexible printed circuits or RFID antennas.     

Capability of Differently Charged Plasma Polymer Coatings for Control of Tissue Interactions with Titanium Surfaces

Titanium surfaces were equipped with positively and negatively charged chemical functional groups by plasma polymerization. Their capability to influence the adhesion of human mesenchymal stem cells (hMSCs) and inflammation processes was investigated on titanium substrates, which are representative of real implant surfaces. For these purposes, titanium samples were coated with plasma polymers from allylamine (PPAAm) and acrylic acid (PPAAc). The process development was accompanied by physicochemical surface analysis using XPS, FT-IR and contact angle measurements. Very thin plasma polymer coatings were created, which are resistant to hydrolysis and delamination. Positively charged amino groups improve considerably the initial adhesion and spreading steps of hMSCs. PPAAm and PPAAc surfaces have an effect on the differentiation of hMSCs, e.g., the expression of osteogenic markers in dependence on culturing conditions. Acrylic acid groups appear to stimulate early mRNA differentiation markers (ALP, COL, Runx2) under basal conditions, whereas positively and negatively charged groups both stimulate late differentiation markers, like BSP and OCN, after 3 days of osteogenic stimulation. Long-term intramuscular implantation in rats revealed that PPAAc surfaces caused significantly stronger reactions by macrophages and antigen-presenting cells compared to untreated control (polished titanium) samples, while PPAAm films did not show a negative influence on the inflammatory reaction after implantation.     

Adhesion of nylon-6 to triazine trithiol-treated metals during injection molding

Abstract —An examination was made of the adhesion of nylon-6 resin to treated metals such as phosphor bronze, brass plates, and electronickel platings during injection molding. No adhesion to any of these metals was noted to occur under ordinary injection molding conditions and an aqueous solution of 1,3,5-triazine-2,4,6-trithiol mononatrium (TTN) was thus used to induce adhesion. Following treatment with aqueous TTN solution under optimal conditions, nylon-6 adhered tightly to all the above metals under ordinary injection molding conditions. The TTN treatment led to the formation of surface films containing metal salts of 1,3,5-triazine-2,4,6-trithiol (TT). Conditions were made optimal with regard to time, temperature and TTN concentration. Adherent films were generally formed when bronze and brass were treated for short periods, at low temperature, and at low TTN concentration, although this was not the case with nickel plating. There was no adhesion to nickel plating even for a prolonged treatment time, high temperature, and high TTN concentration. Adherent and non-adherent films did not differ in the chemical structures of the metal salts of TT but they did differ in morphology. Good adhesion was noted in the case of TT-metal salts present at low density on the metal surface. Some films readily reacted with amino compounds under conditions similar to those generally used for the injection molding of nylon. The adhesion was concluded to be due to the formation of interfacial bonds during injection molding.