Paint and Coating Testing Manual: Fifteenth Edition of the Gardner-Sward Handbook
|Publication Date:||1 January 2012|
PAST TO PRESENT
The previous edition of this manual, the 14th, described in detail the changes that took place in the coating industry from the early 1970s to the early- to mid-1990s. Published in 1995, the 14th edition classified powder coating, radiation-cured coatings, and higher-solids coatings as new, with a potentially reasonable growth curve. It noted that at the time, all liquid coatings were at higher solids content (lower volatile organic solvent content) than in the 1960s when Rule 66 came into being. Powder coating and radiation curing were sufficiently new enough that chapters related to testing them were not included in the manual. High-solids development still struggled with the difficulties of decreasing molecular weight for low viscosity purposes and achieving the low molecular weight with functionality on all molecules that quality coatings require. However, the solids level has increased in solvent-based coatings and achievements have been realized in decreasing volatile organic content (VOC).
Since that time, powder coating has exploded. Today the technology is well established, has a significant share of the coatings market, is internationally accepted, and has a strong technical society that aids in future growth. To illustrate the widespread acceptance of powder coatings, one merely needs to look at advertisements. Outdoor metal furniture advertisements, for example, proudly include words that imply quality and durability-that is to say, "powdercoated finishes."
Of course, such furniture certainly is not the only commercial outlet for powder coatings. Applications include lighting fixtures, tubing and aerosol cans, automobile and bicycle wheels, rebars, store fixtures, agriculture and construction materials, and on and on. Initially, colors and color changeovers were considered to be a major obstacle to powder coating development, but today a broad variety of colors is available, including many metallic and special effect finishes with abrasion resistance, brilliance, and overall high quality. Powder coating provides quality, economy in manufacturing space, increased production, energy usage reduction, and other facets important to product development and sales in today's marketplace.
As with powder coating, radiation curing of coatings with either ultraviolet or electron beam radiation is no longer a new process. This technology also has been experiencing strong growth since the last edition of this manual. It is the technology in which, through an in situ means, a low viscosity liquid system is converted into a polymeric film or coating directly on a substrate that can be varied in nature-i.e., metal, wood, plastic, composite structures, etc. In effect, the originally liquid system is instantaneously converted into the final high molecular weight, cross-linked coating. Radiation curing of liquid systems is not limited to coatings, and it is growing in the printing ink and adhesive areas. It is considered to be "green" technology, is well established in the marketplace, has garnered a significant portion of the total coatings market, has a strong technical society dedicated to it, and is internationally accepted.
Radiation-curing technology has many facets that will ensure future growth. Harboume1 has pointed out that over and above the usual advantages behind ultraviolet radiation curing technology-energy conservation, usage efficiency, and environmental conservation-its driving force is the fact that the UV process has enabled production and development of products that could not have been achieved with earlier existing technologies. Such products include flexible electronics for energy storage and circuit development, polymeric solar cells, printable electronics, medical devices, touch screens, optical films, and on and on. In the area of solar energy, highly efficient organic photovoltaic cells are being developed that are thinner and lighter in weight with significantly decreased production costs. Such cells are used in emergency power generation, lighting, and outdoor power generation. New smart materials with self-healing properties will provide overall cost savings through high value-added finishes on a variety of substrates. Solvent-based, high-solids coating systems continue to be developed. Such coatings have markedly decreased volatile organic content and provide high quality coatings and reduced environmental damage.