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The purpose of this study is to design and develop a new functional coating system for aerospace AL7075-T6 alloy that would evaluate the mechanical properties of the coating.

This paper outlines the scratch adhesion characterisation of Cr/CrAlN coating using a combination of radio frequency (RF) and direct current (DC) physical vapour deposition (PVD) magnetron sputtering. The surface morphology, microstructure and chemical composition of the Cr/CrAlN film were evaluated by optical microscopy (OM), field emission scanning electron microscopy (FESEM) integrated with energy-dispersive X-Ray spectroscopy (EDX) and atomic force microscopy (AFM). The film-to-substrate adhesion was measured by a scratch test machine manufactured with a detection system, motorized stages, penetration depth sensors, optical microscope and tangential frictional load sensors.

The AFM and ultra-micro hardness results showed an increase in surface roughness to about 20 per cent and hardness to about 74 per cent. Moreover, the film-to-substrate adhesion strength of 1,814 mN was obtained with PVD deposition process.

The main limitation of this work is caused by PVD deposition process. Besides, surface defects such as pinholes contribute to a decrease in adhesion strength.

The higher hardness of CrAlN coating is used to improve the properties of softer aluminium substrates. This hardness prevents ploughing-induced wear and provides greater adhesion strength by preventing coating delamination.

Until now, CrAlN is coated only on ferrous alloys. It has not yet been tried on aluminium alloys. Moreover, coating functionality depends on higher adhesion and failure mechanisms involved in the film-to-substrate system, which is significant in aerospace applications.

The purpose of this work was to perform a systematic study on the effect of formulation on the physical and mechanical properties of ultaviolet (UV) curable urethane acrylate resins. In addition, the authors wanted to derive mathematical formula for the prediction of physical and mechanical properties for the aforementioned system.

The experiments were carried out based on mixture experimental design to determine the effect of different multifunctional acrylates (i.e. 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), trimethyolpropane triactylate (TMPTA)) concentration on the physical and mechanical properties of a UV curable polyurethane acrylate system. The urethane oligomer was synthesized and characterized by the research team. Microhardness, adhesion strength and scratch resistance of the cured films were evaluated as the physical and mechanical properties.

The results revealed that the resin and TMPTA concentrations had the most significant effects on the microhardness property. Adhesion strength of the films showed a linear trend with respect to all variables. Moreover, all components also had a significant and complex influence on the scratch resistance of the cured systems. In addition, mathematical equations proposed by mixture experimental design were derived for all the mentioned properties.

Other multifunctional acrylate monomers (i.e. more than three functional) can be used in the formulations. The kinetics of the curing can affect on the network formation and consequently on the properties of the cured films.

The obtained results can be used by the researchers who are active in the field of structure-property relationship of polymers and surface coatings. The reported data and the mathematical equations can also be used for the formulating of an appropriate formulation based on a specific application.

A systematic and statistical-based approach, i.e. mixture experimental design, was used to evaluate the effect of formulation on some of the properties of a UV curable polyurethane acrylate system. A urethane oligomer and three different multifunctional acrylate monomers as reactive diluents were used in the formulations. Noteworthy to mention that several mathematical models were derived by using analysis of variance for the prediction of the properties studied in this system.

This paper aims to gain a greater insight into the molecular level changes occurring in lac‐epoxy blends, at elevated temperatures for different intervals of time. It is also to determine the changes in key physico‐chemical parameters of these blends, before and after applying thermal stress on these blends.

Films of lac‐epoxy blends, applied on tin panels, were baked at 200°C for different time intervals. The baked films were examined by specular reflectance spectroscopy, as these were otherwise difficult to examine through conventional IR techniques, using KBr pellet method. The results obtained were compared and reported. The blends were also tested for different physico‐chemical parameters like scratch hardness, flexibility, adhesion, acid resistance, etc.

On baking the blends of lac‐epoxy resin at 200°C for different time intervals, the strained three membered epoxy ring apparently break open, releasing some free hydroxyl groups, which react with carboxylic groups in lac resin to form ester linkages, resulting in condensation. In terms of different physico‐chemical parameters, blends of 70 per cent lac:30 per cent epoxy were found to be better in performance than blends of 50 per cent lac:50 per cent epoxy and blends of 30 per cent lac:70 per cent epoxy resins, baked at 200°C for different time intervals. Adhesion and acid resistance of lac‐epoxy blends were very good compared with the parent resins.

The spectral studies on lac‐epoxy blends were done qualitatively. Although desirable, quantitative studies could not be carried out, due to the inherent difficulties in handling the resins.

Lac‐epoxy blends may find an important role in printing inks, varnishes and finishing industries owing to their very good adhesion, gloss, scratch hardness and resistance to the action of acids.

As of now, there is no record of specular‐reflectance and derivative spectrometric studies on lac‐synthetic resin blends. This paper represents the first attempt to obtain and correlate reflectance data with physico‐chemical changes. It also highlights the convenience of the method and the scope of sophisticated data analysis, including derivative spectrometry and spectral subtraction techniques.

To determine molecular level changes occurring in lac resin, due to the effect of thermal stress at different levels of temperature and baking times.

Films of lac resin were applied on tin panels and baked at 100 and 200°C for different time intervals. The baked films were examined by specular reflectance spectroscopy, as they were otherwise difficult to examine through conventional IR techniques, using KBr pellet method. The results obtained were compared and correlated with work reported by earlier authors using wet chemical methods.

No significant spectroscopic change was observed on heating lac resin films at 100°C for different time intervals, as compared to air‐dried (parent) lac films. However, it was observed that when the films were baked at 200°C, the spectroscopic data indicated anhydride formation in the oligomers, due to heating effects.

Chemical researches on lac resin have been typically limited by lack of modern tools, due to the difficult and unique nature of the material. The present method to determine molecular level changes in lac due to heating effects, using state‐of‐art instrumentation and computational technique opens a new vista in this field of research.

Lac resin still has a significant place in the surface coating industry, typically in food applications, insulating vanishes, etc. The results obtained indicate that lac‐based baking compositions, when baked at 200°C, exhibit improved characteristics, in terms of adhesion, scratch hardness and even acid resistance. Such an improvement can be attributed unequivocally to the formation of anhydride linkage as evident from spectroscopic data.

As of now, there is no report of specular reflectance data on lac resin and its derivatives. This paper represents the first attempt to obtain and correlate reflectance data on lac. It also highlights the convenience of the method and the scope of sophisticated data analysis, using computational methods.

In this special feature details are given of those British paints which can be described as corrosion‐resistant primers, both one‐ and two‐pack. The materials are generally classified according to the base or pigment which actively prevents corrosion—e.g. metallic zinc in zinc/epoxy formulations— or by the base which produces a barrier action against corrosion, e.g. bitumen in bituminous paints. Exceptions to this are the etching primers, which are separately classified. About 300 primers are described, the manufacturers' names and addresses being cross‐indexed and listed separately on page 48.

Reports on the preparation of some organic corrosion inhibitors, carried out by the reaction of epoxidized linseed oil free fatty acids with different aliphatic amines under the effect of γ‐ray irradiation. Notes that chemical and instrumental methods were used for identification of the reaction products and that the prepared inhibitors were tested for corrosion protection of steel surfaces by incorporating them in some chlorinated rubber varnishes. Reports that the physical, chemical and corrosion protective properties of the varnish films were studied. Concludes that the prepared inhibitors can be used in small quantities to provide varnishes of excellent adhesion and superior protective properties. Contends, also, that increase of the radiation dose during preparation of the inhibitors and/or during the drying process of the varnish films increases the protective properties of the formed films.

Introduction The application of organic coatings is the most extensive way of protecting metal products from corrosion. Developments of organic coatings and their applications are subject to the effects of many factors at present. The most important among these factors are ecological requirements aimed at the protection of the living and working environments, and the lack of raw materials and energy.

The purpose of this study is to reduce the application of petroleum in automobile paint industry by replacing it with bio-based castor oil along with nano fillers to synthesize automobile base coat (BC).

Bio-based polyurethane (PU) coating applicable in automobile BC was synthesized by using modified castor oil incorporated with nano silica (NS) and titanium-based pigment particles. The influential characteristics of the coating was studied by carrying out cross-cut tape test, abrasion resistance, pencil hardness, lap-shear, thermo gravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis and acid, alkali and oil resistance tests.

Incorporation of NS particles, along with titanium-based pigment particles in optimized ratio into the paint matrix, increases the mechanical, chemical and oil resistance properties and hydrophobicity of the BC, and the findings are compared with the petro-based commercial BC.

There is no significant improvement in thermal properties of the paint matrix, and it is less thermally stable than the commercial BC.

The paint developed through this study provides a simple and practical solution to reduce the petro-based feed-stock in automobile paint industry.

The current work which reports the use of ecofriendly PU BC for automobile paint applications is novel and findings of this study are original.

The purpose of this work was to develop a new trispiperazido phosphate-based reactive diluent (diphosphate-piperazine hydroxyl acrylate [DPHA]) and used as a flame retardant with an epoxy acrylate (EA) in ultraviolet (UV)-curable wood coating.

The concentration of reactive diluent was varied from 0% to 20% in the UV-curable formulation with constant photoinitiator concentration. The effect of DPHA concentration on film properties was studied by differential scanning calorimetry and thermogravimetric analysis, gel content, water absorption and limiting oxygen index.

The results showed that the viscosity of the prepared formulation decreased by increasing reactive diluent (DPHA) concentration which leads to improving the coating efficiency. A high concentration of reactive diluent (DPHA) of the cured films shows good resistance against stain, mechanical and thermal properties, which results in an increased glass transition temperature (T_g) and cross-linking density of the films.

The new trispiperazido phosphate-based reactive diluent was used in wood coating formulation, which resulted in excellent flame-retardant properties with higher cross-linked density with good stain resistance. This material can provide a wide range of application for coating industries to produce a glossy finish.

The disbonding of DLC coating is a main failure mode in the high-speed cavitation condition, which shortens the service life of the bearing. This study aims to investigate influence of adhesion strength on cavitation erosion resistance of DLC coating.

Three DLC coatings with different adhesion strengths were grown on the 304 steel surfaces by using a cathodic arc plasma deposition method. Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of a DLC coating. The cavitation mechanism of the substrate-coating systems was further discussed by means of surface analyses.

The results indicated that, the residual stress decreased and then increased with the increasing DLC coating thickness from 1 µm to 2.9 µm, and the lower residual stress can improve the adhesion strength of the DLC coating to the substrate. It was also concluded that, the plastic deformation as well as the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion strength. However, lower residual stress and better adhesion strength could help resist the occurrence of the coating fracture.

Cavitation tests were performed by using a vibratory test rig to investigate the influence of adhesion strength on cavitation erosion resistance of the DLC coating. The plastic deformation and the fracture occurred on the DLC coating surface at the same time, owing to higher residual stress and poorer adhesion of coating. Lower residual stress and better adhesion of coating could resist the occurrence of the DLC coating fracture.