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Pre-painted sheet metal (e.g. coil coated with polyester-melamine) undergoes large deformations when formed into architectural cladding or white goods. The coatings provide protection and superior aesthetics, so must withstand failure by cracking or delamination during forming. The T-bend test is an industry standard test used to qualitatively compare the formability of coatings and mimics the conditions experienced during hemming processes. The failure of coatings during forming is strain governed, so understanding the surface strains in the T-bend test is of great interest to manufacturers. For the first time, the maximum surface strains experienced during the T-bend test have been predicted using finite element modelling (FEM) and verified experimentally using digital image correlation. The experimental shapes of the deformed blank are compared with the FEM results for further verification. In addition, a novel analytical model is proposed to determine the maximum surface strains. It is shown that strains of up to ~ 225% are applied during a 0T test (bent around a zero thickness spacer) reducing to ~ 23% at 4T (bent around a four times sheet thickness spacer). The finite element model, experimental data and new analytical model show excellent agreement and indicate that behaviour is independent of the substrate thickness or material used. Understanding the strain behaviour quantifies the formerly qualitative T-bend. This will improve the efficacy of the test, allowing metal formers and coating developers to better understand the performance requirements, to reduce waste and to develop better coatings. Graphical abstract

BACKGROUND: Forty percent of hepatitis B carriers have no knowledge of their diagnosis. A prior study in British Columbia suggested high rates of hepatitis B among immigrants. The authors undertook a large-scale screening study to validate these rates. METHODS: Attendees at Asian health fairs without knowledge of their hepatitis B status participated. They completed a questionnaire, and blood was drawn for HBV serologies. Active HBV was defined as HBV surface antigen positive. RESULTS: Of 2,726 patients, 1,704 (62.5%) were female and 1,022 (37.5%) male. Mean age was 62.7 (SD 22.1) years, and mean time of residing in Canada was 27.5 (SD 15.3) years. Most patients originated from China (1,042 patients, 38.2%) and Hong Kong (871, 31.2%). Fifty-six patients tested positive (seroprevalence rate 2.05%, 95% CI 1.52%–2.59%). Most seropositive patients were from China (28 patients, 50.0%). Mean time of residence in Canada for seropositive patients (23.8 [SD 2.1] y) was less than seronegative patients (27.6 [SD 0.3] y) ( p = 0.06). There was a trend towards association of seropositivity with time of residence in Canada (OR 0.98, 95% CI 0.96–1.00, p = 0.09). 8 (14.3%) seropositive patients did not have family doctors, compared with 128 (4.8%) seronegative patients. Lack of a family doctor was strongly associated with seropositivity (OR 3.31, 95% CI 1.32–7.25, χ2 = 10.42, p = 0.001). INTERPRETATION: The authors have shown that high risk immigrant populations may have seroprevalence rates as high as 2,700 per 100,000. Lack of a family physician was associated with seropositivity. These results should be used to design improved outreach programs.

Computational simulations can be used to save on both time and costs, complementing experimental work and providing further guidance. Immiscible polymer blends induce phase segregation, and in some cases can produce useful multicoat systems. This works uses a range of Molecular Dynamics Simulations methods, including an extended Flory Huggins Interaction Parameter χ to initially probe the interactions and miscibility between ester monomers commonly used in coil coatings. This work indicates that blends with similar backbone structures or “like with like” show increased miscibility and those with different structures lead to a large χ value and immiscibility. Further to this, polyester blends with different backbone structures have then been coarse grained with MARTINI beads and simulations of 10 µs have been run to identify the morphology of the blends at the mesoscopic level. Finally, the melamine crosslinker commonly used in polyester formulations has previously been shown to form agglomerates at higher melamine content, these agglomerates have been shown in atomistic simulations.

This chapter discusses the interrelationship of light and darkness from the viewpoint of the lighting designer. It analyses the current situation and the changing response to darkness and darkness’s necessary role within lighting design; it closes with the authors’ recommendations of how to incorporate darkness to promote a richer experience for the viewer. Lighting design, as a designated unique discipline, is a relatively recent field, particularly when compared to the long-established history of architecture and engineering. Throughout its short history, its definition has continuously evolved to align with a growing understanding of the relationship between light, architecture and people. The chapter’s key message is born of the desire to inspire design practices which encourage the creation of unique, emotive and captivating designs which enhance the visual experience of the built environment and deliver richer experiences for the viewer. Understanding that there are inherent tensions between scientific and artistic approaches, the authors promote creative freedom balanced with minimum necessary rational standardisation and place confidence in the extraordinary adaptability of the human visual system.

Thermosetting polyester coatings crosslinked with hexa(methoxymethyl)melamine (HMMM) are ubiquitous for the pre-painted metal sheet used in white goods and architectural cladding. The coatings are typically 20 μm thick and must have superior resistance to cracking during the forming process to maintain their excellent aesthetics and corrosion resistance. Hence, understanding their structure-property relationships is key to design durable coatings with good formability. The thermo-mechanical properties of clear and TiO2-pigmented polyester-HMMM free-films with varying number average molecular weight (MW) from Mn =1500 g/mol to 3300 g/mol and a constant crosslinker content of 20 % have been determined, and this work provides a fundamental investigation into the effects of varying the MW for the first time. Increasing the MW decreases the glass transition temperature (Tg) as the crosslink density reduces due to fewer functional chain ends. The Young’s modulus and yield stress decrease with an increase in MW at low temperatures, and the strain to failure increases around Tg. The TiO2 pigment increases the stiffness of the coatings and reduces the strain to failure around Tg, but has a toughening effect at higher temperatures. All the coatings show comparable behaviour in the Erichsen cupping test; however, increasing the MW reduces the damage during the T-bend test as the coatings are able to withstand higher applied strains. Thus controlling the MW allows a balance of properties to be achieved, as increasing the MW reduces the Tg and modulus while increasing the strain to failure and formability of the coating. Such an understanding of the structure-property relationships allows for better formulating and targeted coating design, reducing cost and increasing performance in the coil coating industry.

A sample of pre-painted metal was investigated using the dual beam system of a focused ion beam (FIB) and scanning electron microscope (SEM). The FIB was used to remove material (known as ‘milling’), clean and ‘polish’ the sample exposing a cross-section of the coating. SEM was then used to investigate and analyse the structure and composition of the coating system. However, preliminary trials showed that in order to have good compositional data the technique needs to be developed and optimised. This paper presents the experimental work that was carried out in order to achieve this. First the milling area was changed from the centre of sample to the edge of the sample. Second, the mill shape needed to be changed from a rectangle to an isosceles trapezoid to allow better detection of the characteristic X-rays for the detector. Finally the tilt and rotation of the stage were changed for further improvement in X-ray detection. Focused ion beam/scanning electron microscope (FIB/SEM) was found to be a useful technique to study the cross-sections of pre-painted metal. Information from secondary and backscatter electrons images can reveal the quality of the coating (for example adhesion to substrate, pigment dispersion, interfacial properties etc.) and also the thickness of the coating causing less damage to the sample compared to other mechanical sectioning techniques. Additionally it offers the ability to look at specific areas of interest such as defects, contamination and corroded areas. Energy dispersive X-ray spectroscopy (EDS) analysis allows mapping of the elements which are shown distributed in the coating and also the quantification of those elements. The results obtained from EDS analysis were representative of the components that were formulated into the pre-painted metal product.

Summary The output from a molecular model of a polyester melamine thermoset coating, generated using techniques developed for modelling biological systems, that attempts to predict the performance of free films in a tensile test, is compared to empirical results and the out-put from a phenomenological model. The latter was constructed using standard equations used by engineers to predict the behaviour of polymers under various conditions from a set of parameters measured by Dynamic Mechanical Analysis. Both come close to predicting reality but a more rapid change in intermolecular forces with temperature, for the first model, would help it to achieve more accurate predictions. Associating some of the parameters of the phenomenological model with molecular mass and chain length may help improve the second model.

OBJECTIVE: Surveillance imaging is considered mandatory after endovascular aneurysm repair (EVAR), but many patients are lost to follow up and the impact of this is poorly understood. This study aimed to examine compliance with post-operative surveillance in the UK and the impact of mal-/non-compliance on endograft re-interventions and survival. METHODS: EVAR-SCREEN centres reported EVAR for intact infrarenal abdominal aortic aneurysms (AAA) from 1 January 2007 to 31 December 2010, with follow up included up to 31 July 2014. Non-compliance was defined by the presence of a single 18 month period in which no surveillance imaging was performed. The outcomes were reported in compliant and non-compliant groups with survival analysis. RESULTS: EVAR was performed in 1414 patients in 10 UK centres. At the end of the study period there were 378 patients with five years of follow up available for analysis. Compliance with surveillance was 66% (61-68%). Compliance varied widely, from 9% to 88% between centres. Age (hazard ratio [HR] 1.03, 95% confidence interval [CI] 1.01-1.05; p = .02) and distance from hospital (HR 1.01, 95% CI 1.00-1.01; p

Pre-painted metal sheet (PPM) is used in applications from domestic appliances to architectural cladding. The coating provides excellent aesthetics and corrosion protection, but must possess excellent formability to not fail due to the large strains applied during the folding and hemming processes used to produce components. Therefore it is important to understand how the coating formulation affects the free-film properties and formability of a coating system. Polyester coatings crosslinked with hexa(methoxymethyl)melamine (HMMM) with a Tg of ∼40 °C were used, pigmented with TiO2. The glass transition temperature was increased by increasing the crosslinker content (from 5% to 30%), decreasing the adipic acid content (from 24% to 12%) and decreasing the molecular weight (from Mn = 3300 g/mol to Mn = 1500 g/mol). The chemical structure of the resin had little effect on the formability of the coatings when the test temperature was normalised with respect to Tg. The formability measured using the Erichsen cupping and T-bend tests is related to the tensile properties of the free-films. The damage induced by the T-bend is greater than that by the Erichsen cupping test due to the higher applied deformation rates in T-bend tests. Increasing the apparent yield and fracture stress increases the likelihood of damage at lower deformation levels, whilst increasing the strain to failure decreases the likelihood of damage in both the T-bend and Erichsen cupping tests. The strength of these correlations reduces with an increase in T-bend level as the magnitudes of the strains applied are reduced. This work takes a holistic approach to correlate structure and tensile properties with formability in both the Erichsen cupping test and T-bend test for the first time, enabling industry to improve coating performance significantly but cost-effectively.

© 2020 Elsevier B.V. Pre-painted sheet metal produced by coil coating is subjected to large deformations during manufacture of white goods and architectural cladding. The thermosetting polyester coatings must resist failure by cracking, and their formability can be assessed qualitatively using the industry-standard Erichsen cupping test. However, this only provides strains much smaller than the coatings can withstand, and hence does not discriminate between coating behaviour. Finite element (FE) modelling has been used to show that the applied strain governs the failure of coil coatings during forming, and to demonstrate how increased surface strains can be achieved by altering key parameters to make the Erichsen cupping test discriminating and quantitative. The surface strains are increased by increasing the coefficient of friction between the indenter and the substrate, and by increasing the thickness of the substrate. A parametric study on substrate properties showed that a smaller strain hardening exponent (i.e. more plastic behaviour) gave higher surface strains. There was no variation in the surface strains over a temperature range of -60 °C to 60 °C. Understanding how the test conditions and substrate properties influence the surface strains improves the efficacy of the Erichsen cupping test. The surface strains applied to a coating can be varied by changing the substrate properties, which allows for greater differentiation between coatings and for the coating failure strains to be determined quantitatively. This provides a data-driven approach to develop and formulate better coatings using a single, efficient and easy test.

Thermosetting polyester-based coatings are used to produce pre-painted metal in the coil coating industry. The coated steel sheet is formed into white goods and architectural cladding, which involves large deformations of the metal and results in large strains in the coating. The Erichsen cupping test is a standard method used to assess the formability, ductility and adhesion of coatings, which induces similar strains to those experienced during forming. It is a qualitative and robust quality control method, but the behaviour of coatings during the test has never been previously studied quantitatively. Failure of coatings on sheet metal during forming is a strain-governed process, so understanding the behaviour of a coating in the Erichsen cupping test will allow the formability, material properties and chemical structure of the polymer to be linked more closely, enabling the development of better coatings. A finite element model has been developed to calculate the coating surface strains for any level of indentation during the test, and has been validated using the surface strains during cupping measured by digital image correlation. A master curve of the maximum strain versus the indentation depth (Erichsen index) has been determined. This allows the strain to failure of the coating on a substrate, a critical material property which is otherwise difficult and laborious to obtain, to be simply determined from the Erichsen test for the first time. The relationship between the Erichsen index and maximum surface strain presented here enables users to obtain this material property both from future tests and from the results of historic tests (as many coating suppliers and users have extensive databases of Erichsen test results stretching back many years). This novel framework provides a quantitative method to analyse the performance of coatings used in the coil industry, redeveloping a century-old technique.

The thermosetting polyester-based coatings crosslinked with hexa(methylmethoxy)melamine (HMMM) used for coil coating sheet metal experience large deformations when formed into architectural cladding and white goods. Cracking of the 20-μm-thick coatings must not occur during forming, to prevent corrosion of the steel substrate, so the relationship between the composition and the thermal-mechanical properties is critical to develop highly formable and durable coatings, and to choose suitable forming conditions. Free films of coatings with 5% to 30% crosslinker content have been analysed. Dynamic mechanical analysis (DMA) showed that the glass transition temperature (Tg) and crosslink density increase with crosslinker content. Differential scanning calorimetry (DSC) has been used to measure the Tg from the thermal response, based solely on the chemical structure, and agrees well with the DMA. Tensile tests were performed at temperatures as a function of DSC Tg (Tg − 40 °C to Tg + 50 °C). There was little variation in Young’s modulus and strain to failure in the glassy region where the intermolecular forces dominate, but in the rubbery region governed by the covalent bonds a lower crosslinker content gave lower values. This indicates that the failure mechanism undergoes a transition with increasing temperature from being controlled by the brittle fracture stress to the yield stress. The addition of TiO2 pigment increased the modulus and apparent yield stress at low temperatures in the glassy region, and increased the strain to failure and failure stress in the rubbery region. Failure envelopes, normalising the tensile data with the DSC Tg and the crosslink density, show the dependence on crosslinker content and pigmentation. This allows the behaviour of coatings to be predicted from their structure, and enhanced coatings to be developed based on the required mechanical properties.

A step scan phase modulation photo-acoustic (SS-PM-PA) Fourier transform infrared (FTIR) peak fitting method has been developed and applied to study (i) the degradation of the polyurethane (PU) coatings crosslinked with different isocyanates, (ii) the harshness of the natural exposure sites, and (iii) the correlation between the accelerated and natural exposure sites in terms of the degradation. Methyl ethyl ketoxime (MEKO) blocked hexamethylene diisocyanate biuret (HDI-BI), MEKO blocked hexamethylene diisocyanate cyclic trimer (HDI-CT) and 3,5-dimethyl pyrazole (DMP) blocked isophorone diisocyanate cyclic trimer (IPDI-CT) were used as-received to crosslink a cycloaliphatic saturated polyester resin binder. It was found that HDI-CT crosslinked PU coating is more durable compared to the HDI-BI. IPDI-CT crosslinked PU coating gives higher durability than the HDI-CT and the HDI-BI. The areas of deconvoluted peaks with Centre X (cm −1 ) = 1573, 1553 and 1535 (amide II, NH–CO) and Centre X (cm −1 ) = 1832, 1813, 1792 and 1770 (acid, anhydride, peracid) are used for degradation index calculation, due to their consistent decreasing and increasing trends, respectively, along with the degradation. It has been found that the natural weathering site in Kuala Lumpur, Malaysia (KL) is harsher than that at Vereeniging, South Africa (SA). The harshness of one year SA and KL natural weathering is comparable to 300 h–900 h of the QUV A exposure test. FTIR peak fitting method outperformed the integration method by giving a better correlation between the accelerated and natural weathering tests in terms of the degradation.

The depth distribution of a TiO 2 pigment within the polyurethane (PU) coil coatings is investigated using step scan phase modulation photoacoustic (SS-PM-PA) FTIR. Coil coatings with different pigment contents were prepared and the modulation frequency (MF) of the SS-PM-PA FTIR varied to record the depth distribution of the pigment within the coating. The TiO 2 pigment was shown to contribute significantly to the SS-PM-PA FTIR signal. A TiO 2 aggregated region within the topcoat is found close to the topcoat-primer interface and further away from the topcoat surface. A deeper TiO 2 aggregated region can be identified when pigment content is relatively low. The SS-PM-PA FTIR signal shows a considerable contribution from the primer originated signal, provided the TiO 2 pigment content is sufficiently high and the modulation frequency applied is relatively low. SEM cross-section imaging results show a strong correlation of the TiO 2 depth distribution with SS-PM-PA FTIR results, which confirms the applicability of the SS-PM-PA FTIR technique to the depth profiling study of TiO 2 pigmented coil coatings.

We hereby present a coarse-grained model of a typical polyester resin for coil coating applications. We validate the model via comparison with experimental data. The interactions between coarse-grained particles are described by the MARTINI force-field [Marrink et al.J. Phys. Chem. B 2007, 11, 7812]. Our model and molecular dynamics simulation protocols include the description of a hardener and the formation of cross-links between the hardener and the polyester resin. We perform experimental tests on the thermodynamic and mechanical properties of the system, and compare them with molecular dynamics simulations. The model estimates the glass transition temperature of the coating within 30 K of the experimental measurement. The model captures correctly the broadening effect of cross-linking on the glass transition, and on the temperature dependence of the elastic response of the polyester resin.

Stable isotopes get personal in this analysis of burials at a medieval cathedral. Compared with the local meat-eating rank and file, those people identified as bishops consumed significantly more fish and were incomers from the east. These results, while not so surprising historically, lend much increased confidence that isotope analysis can successfully read the status and mobility of individuals in a cemetery.

A series of complex polymeric paint formulations have been investigated by ToF-SIMS depth profiling. Employing a Bin+ analysis source and a Buckminster Fullerene (C60) etch source in the dual-beam mode of operation, depth profiles from poly(vinylidene difluoride) (PVdF), poly(urethane) (PU), polyester (PE) and epoxy-based commercial coatings were obtained to determine the distribution of minor components included in the coating formulation. The addition of small quantities of additives such as flow agents is known to induce significant changes in the surface composition of the paint. Depth profiles were obtained from a PU primer formulation to which a 35Cl/37Cl labelled flow agent had been added. The depth profiles show that the chlorine tagged component is confined to the surface region of the coating due to segregation of the flow agent to the air/coating surface. Depth profiles obtained from a PVdF topcoat formulation that included a hexamethoxymethyl melamine (HMMM) cross-linking agent demonstrate that the HMMM intensity is greater at the coating surface than in the bulk. The HMMM depth profile also reveals that the HMMM possesses a depletion zone between the coating bulk and the air/coating surface. Depth profiles obtained from both PE and epoxy primer formulations show that the concentration of inorganic particles included as pigments and anti-corrosion agents in the coatings is greater in the coating bulk than at the coating surface, demonstrating effective detection of these second phase particles, and that, as expected, they are properly dispersed in the organic phase. The results demonstrate that depth profiling of polymeric coatings, when employing a C60 etch source, can be used to determine the distribution of minor components within cured coatings. Copyright © 2008 John Wiley & Sons, Ltd.

Coil Coating is an industrial process widely used to apply a paint layer to metal coil stock, in order to improve the resistance to corrosion as well as the aestetics of the surface. Three thermally cured coatings, formulated on a low Tg ispophtalic based polyester, were investigated by XPS and ToF-SIMS. A model formulation was employed for all three coatings investigated, however, the crosslinking agents used were varied for each formulation. Hexamethoxymethyl melamine (HMMM), tris isocyanurate (TIC) and a combination of HMMM and TIC were included as the cross linking agents in the three coating formulations. The use of TIC alone required a Sn based catalyst to promote the curing reaction. The aim of this work was to investigate the difference in the surface composition of the three coatings and the different behaviour of the different crosslinking agents used. This was in preparation for further studies which will involve interfacial analysis in order to elucidate the mechanism behind intercoat adhesion. The XPS analysis of the air/coating surfaces revealed a nitrogen concentration consistent with the concentration expected from the formulation for the coating containing HMMM. In the other two formulations a lower concentration then that calculated from the formulation was observed. The surface concentration of the two crosslinking agents is not influenced by the presence of the others, indeed the formulation containing both crosslinking agents is, in term of nitrogen concentration, merely a simple combination of the other two coatings. Peaks diagnostic of the cross linking agents were observed in ToF-SIMS spectra acquired from the air/coating surfaces. The coating with HMMM revealed peaks not present on the coating with TIC and vice versa, however the coating with a combination of HMMM and TIC showed all the peaks, with different relative intensities. In the positive spectrum of the sample with TIC the characteristic pattern of the tin catalyst can be observed. By XPS and ToF-SIMS analysis, we have been able to determinate that the HMMM and the TIC have a different distribution on the coating/air surface. Their distribution is not affected by the presence of the other crosslinking agent.

This paper draws on pedagogical research, and in particular it focuses on a research project developed by the Photography team at the University of Northampton: Leet, S., Kalpaxi, E., Sherwood, T., Murphy, A., Dalum-Tilds, G, Lowe, C. (2014-2015) ‘From Material to Virtual’, funded by the Institute of Learning and Teaching (ILT) of the University of Northampton. The transfiguration of historically-accepted material or physical forms of photographic practice and research to a largely virtual experience reflects on-going technological changes which impact on contemporary arts and photography. The vision was to create a high-quality online learning environment requiring innovative approaches to design and delivery, leading to an enhanced student experience. The impetus of the project is driven by the need to develop innovative online approaches to L&T in a changing HE and wider educational market, with the challenge being the translation of a practical image-based subject onto a largely virtual platform whilst sustaining academic standards. This development in online learning coincides with the need to invent new platforms for the circulation of photography, academic projects and art – and where students are required to engage in flipped learning, and to explore these developments in relation to their own practice in a self-reflexive manner. Sample multimedia content created (videos and stills) will form the basis of a toolkit for users to develop their practical knowledge. A prototype of an interactive image gallery where individuals will be able to upload their images and collaborate with others to curate content, along with an integrated feedback/discussion platform will be designed. Testing will be underway with regards to its integration into UoN’s VLE. Interactive lectures will be created using Adobe Captivate, where e-tivities are embedded into subject specific content. Questionnaires, feedback surveys and a seminar involving students and external contributors will be used to assess its functionality and quality.

The migration and segregation of a minor silicone containing additive in a multilayer, organic coating system has been investigated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The silicone containing additive employed was the most compatible thermally stable, polyester modified poly(dimethyl siloxane) (PDMS) flow agent. A polyester/polyurethane (PU) based primer and a poly(vinylidene difluoride) (PVdF) based topcoat on an aluminium substrate were used as a model, multilayer, organic coating system. XPS and SIMS characterisation of the PU primer formulation (with and without addition of the PDMS based flow agent), confirmed that the PDMS based flow agent segregated to the PU primers air/coating surface. Characterisation of the PVdF topcoats air/coating surface, after application and curing over the PU primers, revealed the presence of the PDMS based flow agent at the PVdF air/coating surface when the topcoat was applied to the PU primer containing the PDMS based flow agent. Ultra-low-angle microtomy (ULAM) was employed to produce an ultra-low-angle taper that passes through the entire thickness of the PVdF topcoat (∼20 μm). XPS linescan analysis along the ULAM taper indicated that the PDMS based flow agent had migrated from the PU primer surface into the bulk of the PVdF topcoat. Analysis of the shape of the silicon concentration profile revealed the existence of a silicon concentration gradient and indicated that the PDMS based flow agent was segregating towards the PVdF topcoats air/coating surface. Such migration and segregation phenomena have major implications for formulators in the coatings/paint industries.

The strength of intercoat adhesion exhibited between a series of polyester/polyurethane (PU) based primer formulations and a standard poly(vinylidene difluoride) (PVdF) based topcoat formulation has been investigated by X-ray photoelectron spectroscopy (XPS). An initial XPS study of changes in surface elemental composition (induced by variation of the peak metal temperature (PMT) achieved during thermal curing), on a subset of the PU primers employed, indicates that beyond a PMT of 232 °C changes in PU primer surface composition are negligible. A reference PU primer coating formulation and four variations of this formulation, produced by including, excluding or substituting components/additives in the reference formulation, are characterised by XPS. The PU primer formulation in which a flow agent additive is included exhibits segregation of the flow agent to the primer surface. The PU primer and PVdF topcoat intercoat adhesion failure surfaces resulting from failure at or near the PVdF/PU interface as a result of a peel test are also characterised by XPS. Additionally, the PVdF topcoat air-coating surface is characterised by XPS. The interface analyses for the flow agent containing PU primer formulation indicates stripping of the flow agent layer from the PU primer and transfer of the flow agent to the PVdF topcoat interfacial failure surface. Similarly, PU primer formulations in which the concentrations of a cross-linking resin are changed demonstrate that the transfer of carbon and oxygen containing materials from the PU primer to the PVdF topcoat occurs, due to insufficient cross-linking of the polyester component of the PU primer formulation. These results suggest a correlation between the nitrogen concentration at the PU primer surface and the strength of the intercoat adhesion exhibited by the PU primer towards the PVdF topcoat.

Conventional rotary microtomy in combination with high-precision, ultra-low-angle sectioning blocks have been used to produce cross-sectional, ultra-low-angle tapers in polymeric coating systems. Tapered samples produced by ultra-low-angle microtomy (ULAM) have been employed in the investigation of intercoat bonding interfaces in multilayer polymeric coatings and for the compositional depth profiling of polymer/polymer + additives systems. X-ray photoelectron spectroscopy (XPS) cross-sectional analysis of a poly(vinylidene difluoride) (PVdF) based topcoat and a poly(urethane) based primer interface exposed by ULAM processing indicates diffusion of fluorine-containing components of the PVdF topcoat formulation into the uppermost nanometres of the underlying poly(urethane) primer. It is demonstrated that a ULAM exposed, cross-sectional multilayer interface, with a taper of

The interfacial region of a model, multilayer coating system on an aluminium substrate has been investigated by high resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS). Employing ultra-low-angle microtomy (ULAM), the interface between a poly(vinylidene difluoride) (PVdF) based topcoat and a poly(urethane) (PU) based primer ‘buried’ over 20μm below the PVdF topcoat’s air/coating surface was exposed. Imaging ToF-SIMS and subsequent post-processing extraction of mass spectra of the ULAM exposed interface region and the PVdF topcoat and PU primer bulks indicates that the material composition of the polymer-polymer interface region is substantially different to that of the bulk PVdF and PU coatings. Analysis of the negative ion mass spectra obtained from the PVdF/PU interface reveals the presence of a methacrylate based component or additive at the interface region. Reviewing the topcoat and primer coating formulations reveals the PVdF topcoat formulation contains methyl methacrylate (MMA)/ethyl acrylate (EA) acrylic co-polymer components. Negative ion ToF-SIMS analysis of an acrylic co-polymer confirms it is these components that are observed at the PVdF/PU interface. Post-processing extraction of ToF-SIMS images based on the major ions of the MMA/EA co-polymers reveals these components are observed in high concentration at the extremities of the PVdF coating i.e. at the polymer-polymer interface but are also observed to be distributed evenly throughout the bulk of the PVdF topcoat. These findings confirms that a fraction of the MMA/EA acrylic co-polymers in the formulation segregate to the topcoat-primer interface where they enhance the adhesive properties exhibited by the PVdF topcoat towards the underlying PU primer substrate.

The influence of peak metal temperature (PMT) applied to crosslinkable industrial coil coatings has been investigated by angle-resolved XPS (ARXPS). Two series of coatings based on different reactive polyester resins (linear or branched) but the same hexa-methoxy-methyl melamine crosslinking agent were involved. The formulations also contained either a poly(acrylic) or a silicone-based flow agent additive respectively. The coatings were cured to different extents (seriously undercured, just undercured, properly cured and overcured, respectively). ARXPS demonstrated minor modifications in the chemical composition of the surfaces of these paints as the PMT (and hence cure) was varied, for a given take-off angle of analysis. However, characterisation of the elemental composition at different take-off angles allowed the determination of an elemental depth profile for each coating. These elemental depth profiles clearly demonstrate a preferential segregation of the flow agent additive towards the air–coating surface. The thickness of flow agent outerlayer was evaluated in the range of 1.0–1.5 nm depending on the nature of the flow agent added in the formulation.