Search

Ferulic acid (FA) is an unsaturated hydroxycinnamic acid that can be isolated from lignin. In this study, the biorenewable FA was allylated to result in a library of mono- or diallylated monomers, either having the inherent cinnamoyl double bond intact or saturated through hydrogenolysis. All monomers were photo-chemically cured with trimethylolpropane tris(3-mercaptopropionate) (TRIS) into crosslinked films in the presence of a photoinitiator (Irgacue 819). The reactivity of the FA-derived monomers toward TRIS was investigated in detail by photorheology and FT-IR spectroscopy to reveal details on the relative reaction rates for the different alkene groups. The thermo-mechanical properties of the crosslinked films were fully characterized by means of dynamic mechanical analysis (DMTA) and thermal calorimetry (DSC). It was demonstrated that the glass transition temperature of the final crosslinked network could be controlled by the addition of a monoallylated monomer. By increasing the content of the monoallylated compound, it was possible to observe a linear decrease of the Tg-values of the crosslinked films.

In this research, a fundamental study was conducted on damage behavior of cathodic arc evaporated TiN and Ti0.44Al0.56N coatings, in terms of oxidation and cracking/spallation, when they were exposed to single-pulse laser treatment in a temperature range of 1200–2100 °C. Moreover, a multiple-pulse laser treatment was designed to apply thermo-mechanical loads on the coatings in order to evaluate their thermal degradation during rapid heating/cooling cycles between 200 and 1200 °C. Single-pulse treatment of TiN up to 1500 °C led to the intercolumnar cracking and formation of ultrafine TiO grains. An increase in temperature up to 2100 °C resulted in a notable bulging of the surface, and formation of TiO2 of various morphologies such as grainy structure, dense molten and re-solidified structure, droplets from melt expulsion and, more interestingly, nanofibers. Multiple-pulse treatment of TiN was accompanied by a severe cracking and spallation, which divided the surface into two layers: a heavily cracked top layer composed of dense TiO2 grains, and a bottom layer having porous TiO2 grains indicating incomplete oxidation. Conversely, Ti0.44Al0.56N did not show any visible cracking and oxidation after single-pulse treatment. Multiple-pulse treatment did not also yield cracking and spallation for Ti0.44Al0.56N, and its ablated region consisted of TiO2 grains combined with thin Al2O3 platelets. An excellent combination of properties including higher oxidation resistance and greater fracture toughness at high temperatures led to a higher thermal damage resistance for Ti0.44Al0.56N coating compared to TiN when undergoing single- and multiple-pulse laser treatments.

A series of renewable unsaturated polyesters were synthesized from itaconic acid (IA), succinic acid, and 1,4-butanediol by solvent-free polycondensation. Previous studies utilizing IA to make polyesters for coating applications have shown great potential; however, the curing and material properties have not been investigated in detail. The aim of this study was to investigate how the curing is affected by the amount of unsaturations and how well itaconate-based polyesters crosslink without the addition of any other unsaturated monomers or reactive diluents. The chemical structures of the polyesters were confirmed with FTIR, 1H-NMR, and THF–SEC. The degree of curing was studied with FTIR, and the mechanical properties of the crosslinked polyesters were evaluated with DMA, pendulum hardness, and microindentation. The degree of curing was found to be up to 75%, and furthermore, it was found that the final mechanical properties of the crosslinked coatings could be tuned by modifying the IA content in the monomer composition. The results from DMA showed that there is a clear trend between mechanical properties and crosslinking density.

In polymer nanocomposites, particle-polymer interactions influence the properties of the matrix polymer next to the particle surface, providing different physicochemical properties than in the bulk matrix. This region is often referred to as the interphase, but detailed characterization of its properties remains a challenge. Here we employ two atomic force microscopy (AFM) force methods, differing by a factor of about 15 in probing rate, to directly measure the surface nanomechanical properties of the transition region between filler particle and matrix over a controlled temperature range. The nanocomposite consists of poly(ethyl methacrylate) (PEMA) and poly(isobutyl methacrylate) (PiBMA) with a high concentration of hydrophobized silica nanoparticles. Both AFM methods demonstrate that the interphase region around a 40-nm-sized particle located on the surface of the nanocomposite could extend to 55-70nm, and the interphase exhibits a gradient distribution in surface nanomechanical properties. However, the slower probing rate provides somewhat lower numerical values for the surface stiffness. The analysis of the local glass transition temperature (T

The use of bio-based raw material is regarded as a sustainable way to address environmental concerns. A naturally occurring monomer, 9,10-epoxy-18-hydroxyoctadecanoic acid (EFA), was retrieved from outer birch bark. A series of model experiments revealing relative reaction rates for epoxide, carboxylic acid, and alcohol functional groups was investigated. Real-time Fourier transform infrared spectroscopy and nuclear magnetic resonance were used to follow the different model experiments. The results on the model systems were then compared to the thermoset formation of thermally cured EFA. Finally, the adhesive properties of crosslinked EFA on different substrates were evaluated.

Coatings of (Al1-xVx)2O3, with x ranging from 0 to 1, were deposited by pulsed DC reactive sputter deposition on Si(100) at a temperature of 550 {\deg}C. XRD showed three different crystal structures depending on V-metal fraction in the coating: {\alpha}-V2O3 rhombohedral structure for 100 at.% V, a defect spinel structure for the intermediate region, 63 - 42 at.% V. At lower V-content, 18 and 7 at.%, a gamma-alumina-like solid solution was observed, shifted to larger d-spacing compared to pure {\gamma}-Al2O3. The microstructure changes from large columnar faceted grains for {\alpha}-V2O3 to smaller equiaxed grains when lowering the vanadium content toward pure {\gamma}-Al2O3. Annealing in air resulted in formation of V2O5 crystals on the surface of the coating after annealing to 500 {\deg}C for 42 at.% V and 700 {\deg}C for 18 at.% V metal fraction respectively. The highest thermal stability was shown for pure {\gamma}-Al2O3-coating, which transformed to {\alpha}-Al2O3 after annealing to 1100{\deg} C. Highest hardness was observed for the Al-rich oxides, ~24 GPa. The latter decreased with increasing V-content, larger than 7 at.% V metal fraction. The measured hardness after annealing in air decreased in conjunction with the onset of further oxidation of the coatings.

The objective of this study was to modify highly insulative and lightweight biorenewable foam thermosets to be semi-conductive for primarily building material applications. The foams were formed an ...

This study describes the formulation, curing, and characterization of solid polymer electrolytes (SPE) based on plasticized poly(ethylene glycol)-methacrylate, intended for use in structural batteries that utilizes carbon fibers as electrodes. The effect of crosslink density, salt concentration, and amount of plasticizer has been investigated. Adding a plasticizing solvent increases the overall performance of the SPE. Increased ionic conductivity and mechanical performance can be attained compared to similar systems without plasticizer. At ambient temperature, ionic conductivity (σ) of 3.3 × 10−5 S cm−1, with a corresponding storage modulus (E′) of 20 MPa are reached. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44917.

The increased environmental awareness has driven academia and industry to utilize environmentally benign sources. An industrially available process that is effective in the coatings industry is the ...

The aim of this study is to better understand the oxidation mechanism of the fatty acids applied on wood surfaces. In the present study, model hemicellulose compounds were used to measure the effec ...

The wear characteristics of PVD coated (TiN, TiSiN, TiAlN, and AlCrN) polycrystalline cubic boron nitride (PCBN) cutting tools were compared to those of uncoated PCBN during single point turning of case hardened steel 16MnCr5. Post-cutting observations of the worn inserts were performed using high resolution field emission gun scanning electron microscope (FEG-SEM) in combination with focus ion beam (FIB) and analytical transmission electron microscopy (TEM). Substantial differences in the wear behaviour of the different coating materials could therefore be observed. In particular, a remarkable tendency for TiN to exhibit plastic deformation was revealed while TiSiN exhibited a more brittle behaviour evidenced by adhesive wear and microchipping. TiAlN and AlCrN on the other hand exhibited less workpiece adhesion. The wear mechanisms of the above thin coating layers are discussed and interpreted in light of thermal, mechanical, and frictional conditions occurring at the tool–chip contact.

Ti–Si–C–N thin films with composition of 1–11 at.% Si and 1–20 at.% C have been deposited onto cemented carbide substrates by arcing Ti–Si cathodes in a CH 4 + N 2 gas mixture and, alternatively, through arcing Ti–Si–C cathodes in N 2 . Films of comparable compositions from the two types of cathodes have similar structure and properties. Hence, C can be supplied as either plasma ions generated from the cathode or atoms from the gas phase with small influence on the structural evolution. Over the compositional range obtained, the films were dense and cubic-phase nanocrystalline, as characterized by X-ray diffraction, ion beam analysis, and scanning and transmission electron microscopy. The films have high hardness (30–40 GPa by nanoindentation) due to hardening from low-angle grain boundaries on the nanometer scale and lattice defects such as growth-induced vacancies and alloying element interstitials.

International audience; Despite having been used for ages to protect wood against the influence of outdoor elements, the chemistry of vegetable oils within wood is poorly known. We propose a method based on solid-state magic-angle sample spinning NMR to in situ characterize oil oxidation as well as its immobilization. To eliminate signal coming from wood molecules but to keep signal from the oil, direct 13C excitation is performed with low-power 1H decoupling during signal acquisition. To suppress the effect of anisotropic spin-interactions and magnetic field inhomogeneity, the sample is spun at the magic-angle. Mono- and polyunsaturated fatty acid derivatives show a difference in their oxidation process: the monounsaturated methyl oleate reacts with wood components and becomes immobilized while the polyunsaturated methyl linoleate becomes oxidized and form oligomers but does not seem to bind to wood. Linola® oil behaves as would be expected on the basis of its composition by monounsaturated and polyunsaturated chains. This method can be generalized to all coating treatments to characterize chemical pathways and reactions. A better understanding of coating effects on wood is a crucial step to design more efficient protective mixtures.

The isostructural decomposition of arc evaporated Ti0.6Al0.4N coatings at the elevated temperatures and high stresses occurring during metal cutting have been studied. Comparisons are made with sho ...

The wear resistance of metal cutting inserts coated with metastable Ti0.34Al0.66N/TiN multilayers was tested in continuous turning of an AISI 316L stainless steel. The multilayers had periods of 25 ...

Ti1 − xSixCyN1 − y films have been deposited by reactive cathodic arc evaporation onto cemented carbide substrates. The films were characterized by X-ray diffraction, elastic recoil detection an ...

ZrN 1.20 /Zr 0.44 Al 0.56 N 1.20 multilayer films as well as ZrN 1.17 and Zr 0.44 Al 0.56 N 1.20 films were deposited by reactive arc evaporation on WC–Co substrates. Samples were post-deposition annealed for 2 h at 800–1200 °C. As-deposited and heat treated films were characterized by scanning transmission electron microscopy, X-ray diffraction and nanoindentation. The thermal stability was studied using a combination of differential scanning calorimetry, thermogravimetry, and mass spectrometry. The as-deposited Zr 0.44 Al 0.56 N 1.20 film exhibits a nanocomposite structure of cubic and wurtzite ZrAlN. During annealing, the formation of ZrN- and AlN-rich domains results in age hardening of both the Zr 0.44 Al 0.56 N 1.20 and the ZrN/ZrAlN multilayers. The age hardening is enhanced in the ZrN/ZrAlN multilayer due to straining of the ZrAlN sublayers in which a maximum hardness of 31 GPa is obtained after annealing at 1100 °C.

A series of allyl ether functionalized hyperbranched (HB) polyester of three generations was synthesized from commercially available Boltorn (R). These modified HB polymers were homopolymerized to ...

A method based on focused ion beam milling and analytical electron microscopy to investigate the nature of the tool-chip interface is presented. It is employed to study tool-chip interfaces of the rake face of a (Ti0.83Si0.17)N coated PCBN insert after turning of case-hardened steel. Analytical electron microscopy shows the presence of a smeared adhered layer on the coating, which consists of steel elements from the work-piece, oxygen, and Si and N, most likely originating from the coating. Original Publication:Axel Flink, R M Saoubi, Finn Giuliani, J Sjolen, T Larsson, Per Persson, M P Johansson and Lars Hultman, Microstructural characterization of the tool-chip interface enabled by focused ion beam and analytical electron microscopy, 2009, WEAR, (266), 11-12, 1237-1240.http://dx.doi.org/10.1016/j.wear.2009.03.001Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com/

It can be concluded by the study of UV primer formulations on sheet molding compound (SMC) substrates that all studied formulation parameters affect adhesion. Moreover, the dual cure approach can result in acceptable adhesion of UV primers on SMC substrates if the coating procedure and composition are well designed. Adhesion of UV cure primers as determined by the cross-cut test is significantly improved in formulations containing solvent. This is a result of enhanced wetting and interaction of the solvent with the SMC substrate, confirmed by contact angle and gravimetric swelling studies. Furthermore, sanded SMC surfaces demonstrated superior UV primer adhesion. This results from the increased surface area of the topography, confirmed by CSLM and the exposure of more oxygen moieties such as pigments and silanols at the air-substrate interface as confirmed by AFM and XPS. The UV films have a higher modulus with increasing resin functionality and resulting cross-link density which correlated with reduced adhesion in formulations without an added isocyanate functional UV monomer. This indicates that cure shrinkage may play a role in the adhesion of UV cure primers and will be investigated further. Also, the added adhesion that an isocyanate functional UV monomer provides results in a significant increase in the glass transition temperature (Tg) giving a glassier film at room temperature.

Sheet molded compound (SMC) is a highly filled, glass fiber reinforced, thermoset material used in trim and body panel automotive parts. When SMC-substrates are coated with conventional thermally c ...

Four different fatty acid methyl esters (FAMEs): rape seedmethyl ester (RME), tall oil methyl ester (TOME), and two types of linseed oilmethyl ester (Linutin) have been studied as reactive diluents ...

The solvent content of a thermally cured coil-coating paint may be reduced by introducing a reactive diluent derived from a vegetable oil and thereby producing a coating partly based on a renewable resource. A reactive diluent acts as a solvent in the liquid paint, lowering the viscosity, and is then incorporated into the film during cure. In the present study, rape seed methyl ester (RME) has been evaluated as reactive diluent in a thermally cured hydroxyl-functional polyester/melamine system. RME has suitable diluting properties and functionality to be incorporated into the dry coating. Dynamic mechanical analysis of free standing films shows that the final film properties are affected by presence of reactive diluent, oven temperature, choice of co-solvent, and flash-off period.

In this paper the bonding of thin vegetable oil films on mercapto silane treated aluminium surfaces has been studied. The silane molecules are attached to the surface by metal–oxygen–silicon bonds. The coupling between the unsaturated bonds of the vegetable oil and the thiol functionalised surface was obtained through a photoinduced thiol-ene reaction. The surfaces were characterised by X-ray photoelectron spectroscopy (XPS). Vegetable oil contains both saturated and unsaturated carbon chains. For the reactions investigated in this study it is the unsaturated carbon chains that can react by a thiol-ene reaction and the results indicate that it is possible to attach a vegetable oil to a metal surface pre-treated with a thiol functionalised silane.

A model study on the transesterification reaction between fatty acid methyl ester (FAME), e.g. methyl oleate, methyl linoleate, rape seed methyl ester and different alcohols in thin films have been ...

The present study describes the mechanical behaviour of powder coatings used under very high compressive loads in clamping force joints. Carboxyl functional polyester powder coatings cured with hydroxyl functional β-hydroxyalkylamides with variations in amount of filler have been studied. The coatings were subjected to relaxation tests in tension and in compression. The tests in compression were performed in specially designed tests developed to study the behaviour of powder coatings under compressive loads in clamping force joints. The relaxation results for the matrix were used in a unit cell in micromechanical finite element (FE) model to predict the homogenised viscoelastic properties of the particle composite. These constitutive properties were subsequently used to evaluate the behaviour on a macromechanical scale in a screw joint. The model corresponds well with experimental data at ambient temperature. When increasing the temperature above the glass transition of the coating, however, the model predictions and experimental data differ. Experiments in compression show a much lower relaxation as compared to the FE model. The relaxation simulations of the coating under compressive loads from screw joints showed a significant sensitivity to the Poisson's ratio of the polymer matrix. As the Poisson's ratio approaches 0.5, the matrix becomes hydrostatically incompressible, which resulted in a negligible relaxation of the coating at the screw joint.

Thermosetting resins based on semi-crystalline poly(dimethyl trimethylene carbonate) (PDTC) were synthesised and characterised. Polymers with linear and branched architectures were synthesised thro ...

Studies of the drying of two linseed oils with different fatty acid patterns, oil A (74.2% linoleic acid) and oil B (55.2% of linolenic acid), show that the structural variations and the addition of the methyl ester of oil A as a reactive diluent (0, 20 and 40wt%) influenced the drying performance and final film properties of the oils. The incorporation of reactive diluents reduced the effects of surface sealing for oil B at higher temperatures and increased the through-drying rate of oil B. Softer coatings were obtained for both oils when using a reactive diluent. Chemical reactions induced by the wood substrates are shown to affect the drying.

The present study describes the mechanical behavior of powder coatings used under very high compressive loads in clamping force joints.

A radiation curable resin has been synthesized from a hydroxy functional hyperbranched polyether onto which an epoxy functional fatty acid, vernolic acid, has been attached. The resin was cationica ...

ToF-SIMS has been used to analyse an aluminium surface treated with a vegetable oil using a mercapto silane as a coupling agent between the aluminium substrate and the vegetable oil. The coupling between the vegetable oil and the mercapto silane was obtained through a photoinduced thiol-ene reaction using UV-radiation. The ToF-SIMS results show that the desired thiol-ene reaction has taken place between the unsaturated parts of the vegetable oil and the thiol groups of the mercapto silane via the thiol-ene reaction forming a surface film.

Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, ...

An increased demand for new and improved coating systems, both due to environmental as well as performance reasons, have appeared during the last decades. Techniques such low temperature curing powder coatings, radiation curable systems, and high solids have gained an increased interest and obtained significant market shares. Although improved in many aspects, these systems still have limited use in certain applications due to technical reasons. One way to change the properties of thermoset resins that has obtained significant interest during the last decade is by changing the molecular architecture of the resin. An example of polymers which exhibit different properties compared to conventional linear structures are highly branched, dendritic, polymers [1-3]. These polymers, for example, exhibit a higher solubility and lower melt viscosity compared to their linear counterparts. They can also be tailored with respect to functionality and polarity to adjust the properties for certain applications. Coating resins based on hyperbranched polymers have been described both for liquid UV-curable systems as well as powder coatings [4-6]. This presentation will focus on how properties of resins based on dendritic polymers can be tailored and how this can applied to coating systems such as powder coatings, radiation curable resins and no-solvent liquid systems. The correlation between resin structure and its properties both before and after cure will be discussed.

Ductile polymer coatings were investigated in terms of their response to uniaxial deformation and contact deformation with respect to indentation and scratching. The effects of pigmentation, contact geometry, load and speed on the mechanical response were studied. The materials have been tested with extended spherical contacts deep into the coating layer and concentrated conical contacts close to the surface. The residual deformation pattern was examined with optical microscopy, white-light interferometry and atomic force microscopy. In the case of extended spherical contacts, corresponding to small effective strains, there was a correlation between the magnitude of residual deformation and the tensile strength. In the case of concentrated conical contacts, corresponding to larger strains, the materials were ranked differently. Reproducible failure transitions were detected with increased scratch load for the conical contacts. These failure transitions could not be directly linked to uniaxial break parameters. Stratification appears to be an issue in pigmented coatings. The effect of pigmentation was increased tensile stiffness and improved scratch resistance.

The scope of this work has been to investigate storage and recovery processes in ductile polymer coatings. The effects of storage have been measured in terms of variations in mechanical response with time. The use of contact tests in combination with sophisticated surface imaging tools offered unique possibilities to monitor deformation recovery over long periods of time. The kinetics of the recovery processes has been monitored. Polyurethane coatings were found to recover in a similar fashion to a viscous liquid. By comparing the time scale of the recovery with transient tests, it was evident that this was not a viscoelastic effect. The effect of exposure to water and humidity on deformation response and recovery was significant for polyurethane coatings. In addition, high amounts of pigmentation had a great effect on recovery processes. Surface-, bulk-, and interfacial-properties were greatly affected by storage time.

Two ductile coating ma-terials were subjected to a combined indentation and scratch test procedure de-signed to screen a predetermined pattern of many small sample surfaces in a limited time. The screening of 50 surface spots ordered in a matrix pattern on the surface was carried out in 4.5 hr. The test provides reproducible data in terms of indentation modulus, elastic recovery, scratch penetration depth, and scratch residual depth, and also offers the possibility of detecting critical mechanical transitions such as rupture. The presented procedure produces sufficient data in a limited time scale to fulfill the requirements for a fast method to screen coating compositions.

A Tribological Study of a Novel Pre-Treatment With Linseed Oil Bonded to Mercaptosilane Treated Aluminium

The use and interpretation of contact scratch tests on polymer coatings has been investigated. The influences from test parameters such as scratch speed, contact geometry and load on the deformation response were examined. Two ductile polymer coatings of commercial grade tailored for pre-painted steel applications were used as model systems. The residual deformation pattern was examined with optical microscopy, white-light interferometry, and atomic force microscopy. Free-standing coating films were also subjected to static, transient and dynamic tensile testing to find a correlation between the intrinsic coating properties and the scratch behavior. The results indicate that the use of a single set of contact parameters is insufficient to reflect the overall response of a coating material to real contact conditions. A well-designed scratch test will however give a substantial amount of useful information.

Limitation of volatile organic compound (VOC) emissions has lead to the development of new coil coating systems with reduced solvent content. Reactive diluents derived from vegetable oils have been used to substitute up to 40% of the white spirit. The use of vegetable oil derivatives further reduces the handling of solvents improving the workplace environment and safety, enhances the film properties, and introduces a renewable resource in the final coating. The concept can be described as a melamine crosslinkable alkyd which is formed in parallel to the crosslinking process.

Silicon–carbon–nitride (Si–C–N) thin films were deposited by reactive magnetron co-sputtering of C and Si targets in a mixed Ar/N2 discharge. Films were grown to a thickness of more than 0.5 μm on ...

The hardness, elasticity, wear rate and friction coefficient of carbon nitride (CNx) films of defined microstructure and composition are presented. CNx films were deposited by dc reactive magnetron sputtering from a C target in N2/Ar plasma. Films were grown on Si (001), Ni, and HSS substrates to thickness of ~0.5 µm at a total pressure of 3 mTorr with the N2 fraction varied from 0 to 1, and the substrate temperature Ts, varied from ambient to 350°C. The mechanical and tribological properties of the coatings were evaluated by nanoindentation and dry ball-on-disk test. For CNx (0 = x = 0.35) films deposited below 200°C (amorphous structure), the elastic recovery and hardness do not change significantly with increasing N concentration, however, the friction coefficient increases from 0.19 to 0.45, while the coating wear rate is low. For CNx (0 = x = 0.15) films grown at Ts = 350°C, where a transition from a graphite-like to a "fullerene-like" phase occurs, a dramatic increase in hardness and elasticity is observed. Furthermore, the rms surface roughness decreases from 15.0 to 0.4 nm. For 0.15 = x = 0.20, CNx films deposited at Ts = 350°C (fullerene-like phase) exhibit a smooth surface, high hardness and elasticity (~90% recovery), and a coefficient of friction against hard steel of ~0.25. For all substrates, film friction coefficient tends to increase as the nitrogen content in the film is increased. Results also indicate the formation of a transfer layer which improves the tribological properties of the films. © 2001 Elsevier Science B.V. All rights reserved.

The growth and microstructure evolution of carbon nitride CN x (0≤ x ≤0.35) films, deposited by reactive d.c. magnetron sputtering in Ar/N 2 discharges has been studied. The substrate temperature T S varied between 100 and 550°C, and the N 2 fraction in the discharge gas varied from 0 to 100%. It is found that the deposition rate and film morphology show strong dependence on T S and nitrogen fraction. For growth temperature of 100°C, the films are amorphous, and essentially unaffected by the nitrogen fraction. For T S >200°C, however, the nitrogen fraction has more significant effect on the growth and structural evolution of the films. The pure carbon films appear porous and have a high surface roughness. For increasing nitrogen fraction the films become denser and the roughness decreases by one order of magnitude. It is suggested that a chemical sputtering process, during which desorption of volatile N 2 and CN-species, predominantly C 2 N 2 , is important not only for the deposition rate and the nitrogen incorporation, but also for the resulting film structure. The chemical sputtering process becomes more pronounced at elevated temperatures with higher nitrogen fractions.

The concept of using hyperbranched polymers as scaffolds for solid thermoset resin applications is de-scribed. A series of semi-crystalline methacrylate-functional aliphatic poly-esters has been synthesized and characterized for applications as solid thermoset resing, e.g., powder coating resins. The polyester resins have been crosslinked by UV irradiation producing either amorphous or semi-crystalline crosslinked films depending on the initial structure. The resins are based on hyperbranched aliphatic polyesters onto which crystalline linear aliphatic polyester chains have been grafted and end-capped with methacrylate moieties. The resins exhibit a rheological behavior suitable for low temperature curing powder coatings, i.e., films that can be readily formed and UV cured at temperatures below 80°C.

TiCxN1-x films with x ranging from 0 to 1 were grown by arc evaporation by varying the flow ratio between the reactive gases. The substrates were cemented carbide inserts (WC-6 wt.% Co) which were negatively biased at 400 V, resulting in a deposition temperature of similar to 550 degrees C. The film composition, as measured by glow discharge optical emission spectroscopy, was found to vary almost linearly with the gas flow ratio. Cross-sectional transmission electron microscopy in combination with X-ray diffraction (XRD) showed that the films were of single-phase NaCl-structure with a dense columnar microstructure. The intrinsic stress analyzed using the XRD sin(2)psi method, was found to have a maximum of - 5.9 GPa in the composition range of 0.4 less than or equal to x less than or equal to 0.7 which correlated with a maximum in XRD peak broadening due to inhomogeneous strains. The hardness and Young's modulus of the as-deposited TiCxN1-x films were measured by the nanoindentation technique. A maximum in hardness of 45 GPa was found at the same composition range (0.4 Ix I 0.7) as the intrinsic stress maximum. The hardness for x = 0 (TiN) and x = 1 (TiC) were found to be 28 and 36 GPa, respectively. The Young's modulus was constant similar to 610 GPa for films with compositions up to x = 0.6, thereafter it decreased to 540 GPa at x = 1. The increase in intrinsic stress with increasing carbon content is suggested to be due to increased stability of defects created from the collision cascade or/and by a change in the defect structure itself. The fact that hardness showed a maximum at the same composition as residual stress and FWHM indicates that obstruction on dislocation movement has a major influence on the hardness of these films. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

Symmetric CNx/BN:C multilayer thin films, with nominal compositional modulation periods of Λ=2.5, 5, and 9 nm were deposited by unbalanced dual cathode magnetron sputtering from C (graphite) and B4C targets in an Ar/N2 (60/40) discharge. The multilayers and single-layer of the constituent CNx and BN:C compounds were grown to a total thickness of 0.5 μm onto Si(001) substrates held at 225°C and a negative floating potential of ∼30 V (Ei≈24 eV). Layer characterizations were performed by TEM, X-ray reflectivity, RBS, and nanoindentation measurements. Results show that CN0.33 and BN:C (35, 50, and 15 at.% of B, N, and C, respectively) layers were prepared at the above conditions. It is suggested that all films exhibit a three-dimensional interlocked structure with a cylindrical texture in the film growth direction. The structure was continuous over relatively well defined and smooth CNx/BN:C interfaces. All coatings exhibit extreme elasticity with elastic recoveries as high as 85–90% (10 mN maximum load) attributed to the observed structure. However, the multilayers were stiffer and more elastic compared to that of the single-layers and thus shows promise for improved protective properties.

A research area that has obtained increasing interest during the last decade concerns improvement of macromolecular properties by changes in the macromolecular architecture. One group of these materials is dendritic polymers, which are highly branched structures exhibiting very different properties compared with linear polymers. One potential application for these polymers is as radiation curable thermoset resins. This article describes a study where the use of an aliphatic hyperbranched polyester as a base for new radiation curable thermoset resins. The hyperbranched polyesters have been characterized with respect to cure rate and final mechanical properties compared with conventional resins. It is shown that hyperbranched polyesters can be used as versatile scaffolds for various radiation curable resin structures.

Ag/Ni multilayers have been grown by ultra high vacuum d.c. magnetron sputtering onto oxidized Si(001) substrates held at room temperature. Films were grown in both Ar and Kr discharges at different sputtering pressures p. The effects of the different discharge pressures and post-deposition annealing were investigated. The structure evolution was studied using atomic force microscopy (AFM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD pole figure analysis show that all films exhibit a pronounced 〉111〈 fiber texture. Sputtering using low pressures resulted in a reduction of the surface roughness, compared to films grown at higher pressures, and films with rms roughness values as low as 1–2 nm were obtained. XRD analysis show that also the definition of the layer interfaces and the crystallinity of the films improved when the pressure was lowered and when using Ar instead of Kr. The increase in surface roughness with discharge pressure is explained by a reduced adatom mobility on the growing film surface at higher pressures and a wider range of incidence angles of the adatoms when arriving at the surface due to gas scattering. The improved crystalline quality when using Ar instead of Kr is explained using similar arguments. Short post-deposition annealing at 280°C resulted in improved layer definitions as well as improved intralayer order whereas prolonged annealing or annealing at 390°C resulted in agglomeration of Ag precipitates and loss of the compositional modulation. A qualitative model based on the immiscibility of the Ag-Ni system and different diffusivities of Ag and Ni, is proposed.