Karlis Adamsons

Oligomers in the evolution of automotive clearcoats: mechanical performance testing as a function of exposure

Automotive coatings must provide excellent resistance to chemical and mechanical damage in order to maintain a vehicles long-term appearance and the owners long-term satisfaction. The Automotive Industry and coating suppliers are partners in design and delivery of future coatings capable of meeting customer demanded performance. As a result of this partnership, new coating materials are being explored based on oligomer chemistry that show promise in providing improvements in both physical and chemical properties/performance and the long-term maintenance of those properties. Oligomeric systems are also useful in design of low VOC coatings. These supersolids coatings will be capable of meeting current and future air quality standards. In this paper measurement techniques for monitoring chemical and mechanical property changes, including cure rate, crosslinking, tensile properties, rheology and scratch and mar performance, were explored. Laboratory mar tests, wet and dry rub tests, which have been validated by commercial experience, are currently used as the basis for comparison of a coatings mechanical performance. QUV accelerated weathering was combined with micro-scratch experiments, atomic force microscopy, optical microscopy, image analysis and IR surface characterization techniques to provide correlations between chemical composition and mechanical performance, and an indication of service life.

Scratch and mar and other mechanical properties as a function of chemical structure for automotive refinish coatings

Abstract Due to continued customer demand for better quality and more durable coatings, interest in improving the physical damage resistance of automotive refinish coatings has intensified. New coating materials are being explored based on oligomer chemistry that show promise in providing improvements in both physical and chemical properties, and in the long-term maintenance of those properties. In this paper, measurement techniques for monitoring chemical and mechanical property changes, including cure rate, crosslinking, photo-oxidation index, hardness and scratch and mar performance, were explored. The use of the single scratch indentor, a method pioneered in this laboratory, provides a basis for mechanical property evaluation. Constant temperature and relative humidity (CTR) storage and QUV accelerated weathering were used in this study. Mechanical performance was determined using hardness measurements, nano-scratch experiments and wet/dry rubtests. Infrared was the primary method of chemical analysis. This characterization was done to broaden our understanding of structure/property relationships, as well as to provide a more reliable prediction of service life.

Chemical depth profiling of multi-layer automotive coating systems

Abstract Detailed chemical analysis of high performance automotive coating systems can be done with a relatively available and affordable set of measurement technologies, including infrared (IR), ultraviolet–visible (UV–Vis) and optical microscopy (OM) based methods. These tools are very versatile in the ability to do both surface and interface characterization, as well as depth profiling. Their utility is illustrated using a broad range of applications: surface-specific defect analysis; stratification/segregation of network components; mechanisms/kinetics leading to coating degradation and material loss; UVA permanence in coating systems; and UVA interphase mixing between clearcoats and BCs. Many of the studies were conducted as a function of exposure time and conditions (i.e., outdoor/field environments; accelerated aging via QUV, UV only, CHC or xenon borosilicate/borosilicate protocols) or application conditions. Albeit the focus of this work is on chemistry and associated changes while in use, correlations to appearance, physical properties, and mechanical performance will be noted to underscore significance of the changes in chemical composition. Also, sampling techniques used in isolating chemical species or isolating bulk material from a given depth locus will be shown for each application. Since the approaches described herein do not require expertise/equipment that is available to only a few, these works should highlight the potential utility of such tools.

Chemical depth profiling of automotive coating systems using slab microtome sectioning with IR/UV-VIS spectroscopy and optical microscopy

Chemical surface/near-surface analysis and depth profiling of high performance automotive coating systems can be done efficiently by commonly available infrared (IR), ultraviolet-visible (UV-VIS) and optical microscopy (OM) measurement technologies. The different stages of mass loss for acrylic/melamine-crosslinked clearcoats modeled after those used in high performance automotive coating systems were explored as a function of exposure time/conditions. Two approaches were used. Transmission mode IR experiments were conducted to monitor mass loss in isolated clearcoats. OM was used to monitor mass loss in clearcoats that are part of actual multilayered coating systems. UV-screener (UVA) permanence and interphase mixing (i.e., between clearcoat and basecoat layers) as well as general chemistry depth profiling studies of model acrylic/melamine-crosslinked and acrylic/melamine+silane-crosslinked clearcoats were done as a function of system preparation and exposure time/conditions. UVA depth profiles were obtained using slab microtomy sectioning co-planar to the surface, followed by solvent extraction and UV-VIS solution analysis to monitor UVA content as a function of section mass and thickness. General chemistry depth profiles were obtained using slab microtomy sectioning (as mentioned previously), followed by ATR (IR) analysis to monitor changes in the photooxidation index values and the spectral envelop in the 2600–3800 cm−1 range. The approaches described herein do not require expertise/equipment that is available to only a few, thus increasing the potential utility of such tools.

Structure/Property Relationships In Flexible Alkoxysilane Automotive Coatings

Flexible automotive coatings are susceptible to scratch and mar damage, especially during finishing and assembly operations. One-component (1K) flexible clearcoats exhibit very good scratch and mar resistance, but unfortunately suffer from poor durability and environmental etch resistance. Two-component clearcoats offer improvements in both etch and durability, but at the expense of scratch and mar. In this paper, the concept and properties of 1K flexibilized silane clearcoats for use on automotive plastics will be introduced and their structure/property relationships examined as they apply to scratch and mar.The role of coating crosslink density, toughness, glass transition temperature (Tg), and surface profile on the scratch damage of coated plastic substrates will be described. In addition, a new scratch methodology, termed Scratcho, is utilized to determine relative scratch performance and is compared to conventional scratch resistance testing. Results to date indicate that hardness, as affected by the glass transition temperature, and crosslink density, as it contributes to higher essential work values, both affect resultant scratch propensity of the flexible coatings. The relative ranking of different coating systems employing alternate crosslinkers (e.g., isocyanate and melamine) is also presented and compared to the newly developed silane crosslinked coatings.

A modern analytical toolbox: defect (W&D) studies of automotive coating systems, including depth profiling studies

Chemical and microscopy measurement technologies have proven to be very powerful in our failure analysis efforts to detail composition and morphology changes of multilayered automotive coating systems obtained from the field. Weathering and durability (W&D) analyses used include those following chemical composition and property changes, at surface/near-surface and interface/interphase loci, as well as depth profiling through one or more system layers. Microscopy tools include a variety of techniques to study surfaces and normal cross sections. Both macro- and micro-morphology details can be effectively imaged to help investigators correlate coating system appearance changes with the mechanisms, and associated kinetics, of degradation. This article will offer an overview of commonly used analyses for developing new coating systems and for tracking appearance, chemical, physical, and mechanical changes due to common mechanisms causing coating systems to fail during service in the field.

Use of Paramagnetic Relaxation Agents in the Characterization of Acrylic Polymers: Application of Chromium (III) Acetylacetonate and Iron (III) Acetylacetonate

The quantitation of acrylate polymers by high-resolution 13C-NMR requires a knowledge of the spin-lattice relaxation times. For signals from non-protonated carbons, such as carbonyls, these relaxat...

Saving Judd's Untitled 1964: Revival of a Galvanized Steel Single Stack Sculpture with Red Nitrocellulose Paint

Abstract This article describes the conservation treatment of the first cantilevered single stack by Donald Judd, dated March 30, 1964. A section of this galvanized steel work is painted red with a Harley- Davidson paint, a proprietary product developed for the motorcycle and automotive industry. This work is pivotal in Judds oeuvre, not only because it is a very early example of the application of Harley- Davidson colors to his works, but also because this is the only piece where the sheet metal was applied over a wooden core, representing a turning point from works in wood to objects in metals. Rediscovered in 2003 in a condition declared beyond repair, this early piece called for innovative treatment solutions not previously established. Identification, instrumental analysis, and reproduction of the original paint are described. Highlights of the treatment include consolidation of the severely damaged and failing original nitrocellulose-based paint system, and loss compensation of the Harley-Davidson paint and of the spangled pattern of the galvanized steel. The treatments developed and described in this article present viable new options for a range of objects beyond Judds oeuvre.

Scratch and Mar Performance of Coatings: Measurement and Structure Property Relationships

Abstract Scratch and mar of coatings is an important aspect of retaining initial performance levels. A number of test methods have been developed to measure coating resistance to damaging conditions. For the coatings industry, it is critical to have accelerated tests that indicate probable long term (i.e., service life) performance, and to have a means to correlate mar performance with chemical substructures of coatings. In this paper the synergism of measurement techniques for monitoring scratch and mar performance is explored. Laboratory mar tests, which have been validated by commercial experience, are used as the basis for comparison of a coatings performance. The combined elements of chemical, physical, mechanical, morphological and appearance properties of coatings have been explored. Chemical changes during cure and subsequent exposure have been followed by infrared techniques which show degree of cure, extent of photo-oxidation and hydrolysis, as well as changes in cross-linking with time and temperature. Physical and mechanical properties measured include T g, hardness, standard stress/strain measurements, as well as “Method of Essential Work”. Physical properties can be correlated with visual recovery of plastic flow damage and resistance to mar. Furthermore, microscratch experiments have been utilized to explore forces that are needed to induce surface damage and to determine the transitions between elastic deformation, plastic flow, and brittle fracture type damage. Morphology of scratches was examined by the use of atomic force microscopy before and after exposure. Optical imaging techniques were used to characterize scratch and mar. These studies are useful in understanding mechanisms of coating failure.

Disfiguring organic residues on industrially produced sheet metal coupons simulating copper and brass works of art by Donald Judd: Attenuated total reflectance Fourier transform infrared spectroscopy analysis and treatment recommendations

Abstract The Minimalist work of Donald Judd exemplifies modern and contemporary works of art that utilize the appearance of bare metal as an integral component of the artists intent. Decades after fabrication, disfiguring patterns have appeared on the surfaces of many such works. These patterns are not related to the formation of tarnish or other corrosion effects caused by improper storage, display, or transportation and handling; rather, they are associated with the initial processing of the metal sheets and subsequent fabrication of the art objects. Due to the challenges of obtaining analytical data directly from works of art, the authors present results from industrial sheet metal coupons prepared to simulate materials and techniques used in Donald Judds copper and brass artworks. Attenuated total reflectance Fourier transform infrared spectroscopy carried out on each side of 55 coupons indicated the presence of organic materials such as long-chain aliphatic hydrocarbons, esters, and ethers, consistent with the types of compounds used in industrial lubricants. In addition to conducting the first systematic instrumental analysis of these residues, the authors propose the use of specific solvents for their removal as an alternative to abrasive methods, which cause removal of original surface from the objects.