Evaluation of the scratch resistance with nano- and multiple scratching methods

The scratch resistance of automotive clear coats was investigated by a single and multi scratch test procedure. New data characteristic for the reflow capability, the scratch hardness and the lateral scratch resistance were generated and evaluated. A correlation between single and multi scratch data was established.     

Acid and scratch resistant coatings for melamine based OEM applications

Increasing the mar resistance of OEM clear coats has been one of the main R&D priorities of paint manufacturers over the last years. Reaching a good mar resistance level without compromising other coating properties such as acid resistance proves to be a major challenge. We investigated the use of branched glycidyl esters in melamine based OEM acrylic formulations. Our results show that systems based on this type of esters lead to good overall coating properties as well as a good balance between acid and scratch resistance.     

A study of thermal–mechanical properties of an automotive coating exposed to natural and simulated bird droppings

Biological resistance of coatings can be regarded as one of the main properties in automotive industries. This study aims to investigate the effects of biological materials on the mechanical performance of an automotive clear coat. To this end, two acrylic melamine clear coats containing different melamine cross-linker contents were used. In addition, biological resistance of these clear coats were studied at two different ageing processes including pre-ageing and post-ageing which involve various hot-cold, humid shockings and UV radiation of sunlight. By the aid of optical microscopy, micro Vickers and DMTA analyses, different optical and mechanical properties such as micro hardness, T _g, cross-linking density and storage modulus were studied. Results revealed an inverse impact of both biological materials to decrease the clear coats mechanical attributes. In addition, a complicated effect of ageing conditions was observed for both clear coats exposed to these materials. It was shown that the coating having a higher mechanical properties and T _g even resulted in a lower biological resistance.     

Optimization of scratch resistance and mechanical properties in wollastonite‐reinforced polypropylene copolymers

The aim of this research was to establish a balance between scratch resistance and scratch damage visibility in the wollastonite‐filled heterophasic polypropylene copolymers.The influences of various factors including the surface hardness, elasticity, friction coefficient, and combinations thereof on the scratch behavior (scratch resistance and scratch visibility) were elucidated. Using micro‐scale and nano‐scale scratch tests and image analysis techniques, the scratch hardness, scratch depth, and scratch visibility of the composites were characterized.It was found that the introduction of wollastonite in the polypropylene copolymer matrix contributes to ductile fracture behavior because of an induced crystallization alteration. Accordingly, the scratch resistance of reinforced composites revealed an increase as a result of higher stiffness of the wollastonite as well as contribution of new crystalline structure. The addition of siloxane to the composites improved the resistance to surface damage by lowering the surface friction coefficient originated from enhanced chain mobility. Simultaneous addition of high density polyethylene and siloxane induced a significant influence on the resistance to the scratch damage. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of weathering on scratch/mar and mechanical behaviour of clearcoats

The study examines the effect of weathering on mechanical and chemical properties of two 2K (twopack, with and without light stabilisation additives) and one 1K (onepack) clearcoats, concentrating on scratch and mar resistance and acid etch resistance. The clearcoats were investigated before and in the course of accelerated weathering. For determining the mar resistance two different instruments were used: - AMTEC laboratory car wash equipment (rotating wet brush) - Crockmeter Explanations for the changes in clearcoat properties caused by weathering are given by Dynamic-Mechanical Analysis, FT-IR-Spectroscopy, Universal-hardness and surface tension measurements. The clearcoat systems investigated show a clear deterioration of their properties after short periods of accelerated weathering. This effect is more expressed for the clearcoat samples without light stabilizers.     

Scratch resistance and weatherfastness of uv-curable clearcoats

UV-cuing has found an increasing number of industry allocations over the past decade due to its unique benefits, e.g. solvent free formulations, high cure speed and low temperature processing. In addition to these benefits two additional properties of uv-cured coatings are of today's interest, especially in the automotive industry: scratch resistance and resistance against chemicals. One of the most important requirements for a broad use of uv-curable coatings in the coating industry is that coatings are stable against degradation caused by atmospheric influences since coatings for outdoor use are subject to especially harsh weathering conditions, e.g. uv-light, oxygen, moisture and air pollutants. This weathering leads to a degradation of the polymeric binder. Clearcoats containing photoinitiators based on bis-acylphosphinoxide (“BAPO”) and a combination of hydroxyphenyl-s-triazine uv-absorber and a sterically hindered amine as a light stabilizer package show a very good curing behavior as well as an improved weatherfastness over a long period of time and a good scratch and chemical resistance.     

Scratch behavior and material property relationship in polymers

The scratch behaviors of a broad range of polymers are investigated to understand how the material characteristics of a polymer affect the scratch resistance. A constant load scratch test and a progressive load scratch test are chosen for the present study. A scratch model proposed by Hamilton and Goodman is applied to correlate the mechanics and material parameters during the scratch process. An attempt is made to correlate the scratch behavior and basic material properties, such as the Young's modulus, yield stress, and tensile strength. A correlation between the scratch behavior and material surface characteristics, such as the friction coefficient, scratch hardness, and elastic recovery, under the current scratch tests are also made. Scratch subsurface damage in polymers is studied using optical microscopy. It is shown that shear yielding is the main cause of the plastic flow scratch pattern, while tensile tear on the surface and shear‐induced fracture on the subsurface are the main damage mechanisms found in the fracture scratch pattern. The main causes for the susceptibility of thermoplastic polyolefins to scratch damage are discussed. Approaches for making scratch‐resistant polymers are also addressed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 47–59, 2001     

Preparation and properties of copolymer resins based on phenolphthalein benzoxazine–benzoic acid and bisoxazoline

The novel phenolphthalein benzoxazine–benzoic acid (PBB) was synthesized. The structure of the monomer was supported by FTIR, ¹H-NMR, and elemental analysis. The curing behavior of PBB–bisoxazoline (1,3-PBO) resin was monitored by FTIR and differential scanning calorimetry. It was found that PBB–bisoxazoline resin exhibited two-stage polymerization mechanism. The thermogravimetry showed that PBB–bisoxazoline resin had good heat resistance due to the rigidity of PBB polymer chains and the high cross-linking density of copolymer. Furthermore, it seemed that the reaction between PBB and 1,3-PBO also led to an additional cross-linking, which increased the cross-linking density and delayed the decomposition. The cured resin had low water absorption.     

Studies on the Properties of ZnO Crystal Plane Grown by the Innovated Hydrothermal Method

ZnO single crystals were grown by the innovated hydrothermal method. The crystal surfaces were polished, and then studied by atom force microscope （AFM） and wet-chemical etching （WCE）. It was found that the Zn polar plane was smoother than O polar plane under the same polishing conditions. The etch pit density of Zn polar plane is 4.3×10^3 cm^-2, which is consistent with the previous report, while the density of etch pit of O polar plane is more than 103cm^-2. After annealing treatment, the density of etch pit of Zn plane reduces to 5.8×102 cm^2 and is superior to the current report. This investigation reveals that the high quality ZnO single crystals with fine Zn polar plane can be obtained by the innovated hydrothermal method.     

Additives for UV-curable coatings and inks

UV-curable silicones are a highly specialised class of compounds that can be applied in various applications e.g. as additives in UV-curable inks and coatings or as release coatings on paper and plastic substrates. Basically two classes of radiation curable silicones are available on the market today. Both, the free radical and the cationic curing process, offer each unique advantages to the customer. Applied as additives in UV-curable inks and coatings they offer several advantages such as improved wetting behaviour, scratch resistance, flow and levelling of the UV-curable inks and coatings. Additionally, the efficient cross-linking properties minimise the risk of migration.     

2 K clearcoats based on silane and urethane technology

Despite significant advances since the late 80's the balance between mar- and acid etch resistance of automotive clearcoats still is a subject of intense research. Among others silane- and PUR technology is used to produce clearcoats today. Generally speaking the silane based systems show better mar resistance whereas PUR based systems have advantages in acid etch resistance. We wish to show that a certain group of silane modified polyisocyanates can be used as crosslinkers for hybride systems exhibiting an improved balance between mar- and acid etch resistance.     

Curing and properties of chloroprene and butadiene rubber (CR/BR) blends cross-linked with copper(I) oxide or copper(II) oxide

This paper discusses the curing and properties of chloroprene and butadiene rubber (CR/BR) blends cross-linked with copper(I) oxide (Cu₂O) or copper(II) oxide (CuO). The results revealed that the cross-linking degree of CR/BR blends decreased with the increasing amount of butadiene rubber (BR) in the blends. The mechanical properties of cured CR/BR blends depended on the proportion of elastomers in blends, as well as on the type and amount of the cross-linking agent (Cu₂O, CuO). The cross-linking of CR/BR/Cu₂O or CR/BR/CuO blends followed according to cationic mechanism, using Lewis acid, copper(I) chloride (CuCl) or copper(II) chloride (CuCl₂) generated in situ. Additionally, the prepared compositions, both unfilled and filled, were characterized by very high resistance to flame.     

Effect of gamma irradiation on the etching properties of Lexan and Makrofol-DE polycarbonate plastics

It is observed that for Lexan and Makrofol-DE polycarbonate plastic detectors the mean diameters of fission fragments from a ²⁵²Cf source increases as a result of gamma-ray exposure. We have studied the bulk etching rate and track etching rate before and after gamma-ray irradiation on Lexan and Makrofol-DE polycarbonate plastics. The mechanism of Lexan and Makrofol-DE polycarbonate plastic detectors can be understood with the help of this exposures. It is also noted that degree of ordering of Lexan and Makrofol-DE polycarbonate is dependent on the gamma ray dose due to degradation and cross-linking processes. The results show that bulk and track etch rate increases with gamma dose while activation energy associated with bulk and track etch rates at a particular temperature and sensitivity decreases with gamma dose.     

Corrosion behavior of tantalum alloying on γ‐TiAl by double‐glow plasma surface metallurgy technique

The Ta coating with corrosion resistance is grown on the γ‐TiAl substrate by double‐glow plasma surface metallurgy technique, followed by the electrochemical test in 10 wt%, 20 wt% HCl and 10 wt%, 40 wt% H₂SO₄ solution. The data of nanohardness and elastic modulus are collected by the nanoindention test. The adhesion strength of Ta coating is investigated by means of the scratch test. The study of corrosion resistance is performed using potentiodynamic polarization and electrochemical impedance spectroscopy and measured by SEM and X‐ray diffraction. Results highlight that the Ta coating is tightly bonded to the γ‐TiAl substrate, consisting of the deposition layer and diffusion layer. Experimental data indicate that the Ta coating presents excellent corrosion resistance, which is confirmed by the high values of polarization resistance (R_p) and the low values of corrosion current density (i_corr). The surface nanohardness of the Ta coating is improved from 3.41 to 7.29 GPa, nearly twice of that of the substrate. The Ta₂O₅ formed on the coating is able to hold back the penetration of adverse ions inwardly, owing to its dense structure and adhesion effect. Copyright © 2017 John Wiley & Sons, Ltd.     

Hydrogen bubbles and formation of nanoporous silicon during electrochemical etching

Many nanoporous Si structures, including those formed by common electrochemical etching procedures, produce a uniformly etched nanoporous surface. If the electrochemical etch rate is slowed down, details of the etch process can be explored and process parameters may be varied to test hypotheses and obtain controlled nanoporous and defect structures. For example, after electrochemical etching of heavily n‐doped (R = 0.05–0.5 Ω·cm) silicon 〈100〉 single crystals at a current density of 10 mA cm^?2 in buffer oxide etch (BOE) electrolyte solution, defect craters containing textured nanopores were observed to occur in ring‐shaped patterns. The defect craters apparently originate at the hydrogen/BOE bubble interface, which forms during hydrogen evolution in the reaction. The slower hydrogen evolution due to low current density and high BOE viscosity allows sufficient bubble residence time so that a high defect density appears at the bubble edges where local reaction rates are highest. Current‐carrying Si? OH species are most likely responsible for the widening of the craters. Reducing the defect/doping density in silicon lowers the defect concentration and thereby the density of nanopores. Measurements of photoluminescence lifetime and intensity show a distinct feature when the few nanopores formed at the ring edges are isolated from each other. Overall features observed in the photoluminescence intensity by XPS strongly emphasize the role of surface oxide that influences these properties. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis and kinetics of non-isothermal degradation of acetylene terminated silazane

Novel acetylene terminated silazane compounds,with three types of substituent,were synthesized by the aminolysis of dichlorosilane with 3-aminophenylacetylene(3-APA).Thermal property of the compounds is studied by thermogravimetry analysis (TGA).It shows that the acetylene terminated silazane has high temperature resistance.The char yield at 1000℃is 77.6,81.9 and 68.7 wt%for methyl,vinyl,and phenyl substituted silazane,respectively.The pyrolysis kinetics of the silazane is investigated by non-isothermal thermogravimetric measurement.The pyrolysis undergoes three stages,which is resolved by PEAKFTT.The kinetic parameters are calculated by the Kissinger method.The role of functionalities on the thermal resistance is discussed.The vinyl-silazane exhibits higher thermal stability because of higher cross-linking density.     

Characterization of the morphology and composition of commercial negative resists used for lithographic processes

We present a spectroscopic and microscopic characterization of the chemical composition, structure, and morphology of two commercial negative resists using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For this purpose, films of a novolak-based resist (ma-N 2400) and hydrogen silsesquioxane (HSQ) are treated under different conditions (temperature, deep ultraviolet (DUV) exposure, CHF₃ plasma). Topographic AFM images show that both heating and DUV exposure strongly affect the surface morphology of as-prepared ma-N 2400 resist films. These different treatment conditions also lead to decreasing roughnesses, which indicates structural reorganization. Furthermore, the decrease of the photoactive compound (bisazide) in the ma-N 2400 resist films, observed in FTIR spectra, suggests cross-linking of the resist after CHF₃ plasma treatment, heating, or DUV exposure. XPS measurements on different CHF₃ plasma-treated surfaces reveal that a structurally homogeneous fluorine-containing polymer is generated that is responsible for an enhanced etch resistance. FTIR measurements of HSQ films show a correlation between the degree of HSQ cross-linking and baking time.     

A chemical modification approach for improving the oil resistance of ethylene-propylene copolymers

The need for a low-cost and weather, high-temperature and oil-resistant rubber is well-established in the market place. Such products have the potential to replace high cost rubbers and/or oil-resistant rubbers that lack weather and high-temperature resistance. The present study aims at increasing the polarity of EP(D)M rubber by chemical modification and cross-linking of EPM copolymer grafted with maleic anhydride (EPM-g-MA). First, it is shown that the oil resistance of rubbers can be predicted using calculated solubility parameters. Next, a variety of modified EPMs has been designed, directed at a high polarity in combination with a relatively low glass transition temperature, and have subsequently been prepared to validate the concepts experimentally. The various modification approaches resulted in (significantly) improved oil resistance and are in fair agreement with the calculated oil swell data. It is concluded that new rubber materials based on EPM-g-MA can be developed, that may replace existing oil-resistant elastomers.     

Evolution of nanopolar phases, interfaces, and increased dielectric energy storage capacity in photoinitiated cross-linked poly(vinylidene fluoride)-based copolymers

Photoinitiated cross-linking of poly(vinylidene fluoride-co-chlorotrifluoroethylene) can offer a significant increase in electric energy storage capacity. This improvement is related to the structural changes in the copolymer crystals brought by cross-linking. Cross-linking favors formation of polar crystalline phase, drastic reduction of spherulite sizes, and increase in copolymer inner interface area. This copolymer case demonstrates the greatly enhanced energy storage behavior, including increased discharge energy density at reduced field strength, and improved capacitor efficiency at relatively high degree of cross-linking, which may facilitate a better design for polymer dielectric materials in their application of high energy density capacitors.     

Studies of GaAs surface roughness and organic masks resistance depending on the ion-beam energy

Summary The development of A^III–B^V semiconductor surfaces exposed to ion-beam irradiation in the ion energy range from 100 to 1000 eV and the ion current density of 1 mA/cm² (max) is investigated. The ion-beam etching with an ion energy of 1 keV results in sharp cones and needles on the semiconductor surface due to the surface contamination and unevenness. Etching with ion-beam energies in the order of 300 eV and with etch rates higher than 1000 /min produces relatively even GaAs surfaces. In case of reactive gases (i.e. CCl₂F₂ and the mixture of CCl₂F₂+Ar) ion-beam etching results in significantly higher etch rates; however, the mask residue contains Cl and F. In studies on the ion-beam resistance of organic masks selectivities as high as 13:1 for the photoresist CM-79 with an ion energy of 180 eV and an ion current density of approximately 0.3 mA/cm² were achieved.