Chris Molaison

The development of combinatorial chemistry methods for coating development: I. Overview of the experimental factory

Abstract Combinatorial chemistry has proven to be a valuable tool for the development of new compounds. The combinatorial methodology is well suited to the development of complex, multicomponent materials that, typically, require extensive experimentation for their development. As a result, coating development appeared to be a good candidate for the application of the combinatorial methodology. A “combinatorial factory” capable of preparing and testing over 100 coatings per day has been developed. The components of the factory consist of: (1) an automated system to prepare liquid coating formulations; (2) a novel coating application process capable of making high density arrays of coatings of controlled thickness; (3) curing of the coating arrays either thermally or with UV light; (4) testing of the coatings using newly developed high throughput screening methods; and (5) a data handling process to quickly identify the most promising coatings produced. Various aspects of the application of the combinatorial methodology to coating development are described.

Combinatorial chemistry methods for coating development: III. Development of a high throughput screening method for abrasion resistance: correlation with conventional methods and the effects of abrasion mechanism

Combinatorial chemistry has proven to be a valuable tool for the development of new compounds. In the pharmaceutical industry, where combinatorial chemistry began, the approach has been instrumental in the high-speed development of new drugs. Due to the overwhelming success of the combinatorial methodology in the pharmaceutical industry, it has been recently applied to materials development. We have developed a combinatorial factory capable of preparing and evaluating of the order of 100 organic clear coatings per day. One of the most challenging aspects of the creation of the combinatorial factory was the development of the high throughput screening (HTS) methods for determining the primary properties of interest such as optical clarity, abrasion resistance, adhesion, and weatherability. For each property, an entirely new method was developed that allowed for rapid measurement on very small samples. This paper describes, in detail, some of the results obtained during the development of an HTS method for abrasion resistance. In particular, this document illustrates the importance of understanding the mechanism of abrasion and its influence on the measurement of abrasion resistance.

Combinatorial chemistry methods for coating development: V. The importance of understanding process capability

A combinatorial method for the development of organic clear coatings for plastic substrates has been developed. The combinatorial process possesses all the aspects of a conventional combinatorial process such as automated sample preparation, miniaturized samples configured in an array format, high throughput screening (HTS) of the properties of interest, and computer software developed for data management, storage, and analysis. The combinatorial factory has greatly enhanced the rate of organic clear coat development. A very important activity involved in the development of the combinatorial factory was the determination of process capability for each component of the factory. A good understanding of process capability and sources of variability was required to obtain high quality, reliable data.

Development of low temperature curing, 120°C, durable, corrosion protection powder coatings for temperature sensitive substrates

Commercial low temperature cure powder coatings, including candidates representative of all the major coating chemistries, were evaluated. Nearly all failed to adequately react at a cure schedule of 120°C for 30 min, and none, even when prepared at their manufacturer’s lowest recommended cure conditions, met the stringent performance needs for temperature-sensitive military applications. Initial research is presented toward developing low temperature cure powder coatings that simultaneously meet all performance requirements at this target cure schedule. Using commercial resins, corrosion inhibitors, and catalysts, this research effort has closed gaps in low temperature cure coating performance and has helped to identify critical deficiencies. This study establishes direction for future developments in new resin and catalyst technologies.

Optical tools for high-throughput screening of abrasion resistance of combinatorial libraries of organic coatings

Design, validation, and implementation of an optical spectroscopic system for high-throughput analysis of combinatorially developed protective organic coatings are reported. Our approach replaces labor-intensive coating evaluation steps with an automated system that rapidly analyzes 8x6 arrays of coating elements that are deposited on a plastic substrate. Each coating element of the library is 10 mm in diameter and 2 to 5 micrometers thick. Performance of coatings is evaluated with respect to their resistance to wear abrasion because this parameter is one of the primary considerations in end-use applications. Upon testing, the organic coatings undergo changes that are impossible to quantitatively predict using existing knowledge. Coatings are abraded using industry-accepted abrasion test methods at single-or multiple-abrasion conditions, followed by high- throughput analysis of abrasion-induced light scatter. The developed automated system is optimized for the analysis of diffusively scattered light that corresponds to 0 to 30% haze. System precision of 0.1 to 2.5% relative standard deviation provides capability for the reliable ranking of coatings performance. While the system was implemented for high-throughput screening of combinatorially developed organic protective coatings for automotive applications, it can be applied to a variety of other applications where materials ranking can be achieved using optical spectroscopic tools.

High-Throughput Adhesion Evaluation and Scale-up of Combinatorial Leads of Organic Protective Coatings

Coupling of combinatorial chemistry methods with high-throughput (HT) performance testing and measurements of resulting properties has provided a powerful set of tools for the 10-fold accelerated discovery of new high-performance coating materials for automotive applications. This approach replaces labor-intensive steps with automated systems for evaluation of adhesion of 8 × 6 arrays of coating elements that are discretely deposited on a single 9 × 12 cm plastic substrate. Performance of coatings is evaluated with respect to their resistance to adhesion loss. This parameter is one primary consideration in end-use automotive applications. Coating leads identified from the HT screening have been validated on the traditional scale. Details of these validation studies are discussed.