Paints and coatings have been used for thousands of years. Evidence from the walls of caves in Europe and Africa has proven that prehistoric man made and used paint. In the 1700s, paint and coatings became manufactured products that not only added beauty to our world, but also protected and preserved many man-made objects.
1700s -1800s Coatings have been manufactured in the United States since 1700, when Thomas Child operated the first paint mill in Boston. The industry was well established by the 1800s, with numerous small manufacturers producing oil-based alkyds and enamels for their local markets.
1940s -1950s New resin technologies appeared in the 1940s and 1950s. Polyurethane coatings, originally developed in Germany, found their way into the U.S. market. During this period, the first epoxy-based formulations were introduced, as well as flexible, solvent-based vinyl paints. Water-based paints (protective inorganic zinc coatings and acrylic emulsions) and powder coatings were also developed during this timeframe.
1960s Improvements to many of these technologies were made during the 1960s. Better curing agents and high solids content increased both ease of application and performance of epoxy coatings. The development of self-curing zinc coatings eliminated the need for a post-cure step.
1970s New regulations in the 1970s — most notably the state of California Rule 66 and the Clean Air Act (CAA) of 1970 — drove R&D efforts. Most types of coatings were reformulated with lower organic solvent content to meet these new standards.
New electrostatic deposition techniques and improvements in appearance characteristics made it possible for powder coatings to be used in many industrial and automotive applications. Also during this decade, efforts to improve the performance of acrylic latex paints were successful, and these coatings matched or exceeded the durability of solventborne paints, ultimately leading to their widespread use in architectural (household paint) applications.
1980s During the 1970s and 1980s, the auto industry faced a number of challenges, including severe competition from overseas manufacturers and durability issues due to rising acid rain pollution. Automakers began using electrodeposition primers to reduce body corrosion and moved to a basecoat/clearcoat system to provide improved coating performance.
1990s Throughout the 1980s and 1990s, regulatory restrictions for volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) continued to drive development of paint technologies. Radiation-cured coatings, which typically use ultraviolet (UV) light rather than heat to cure, have been making inroads in the market since their introduction in the 1990s. These formulations require little or no solvent, cure almost instantly and provide superior performance.
High solids, solvent-borne coatings also first appeared during the 1990s. Modified resin technologies and specialty additives made it possible to reformulate solvent-based coatings to meet regulatory requirements, while still maintaining the desired level of performance.
Today, paints and coatings are being made for countless purposes — from painting the 40-yard line on a football field, to killing bacteria and viruses, to harnessing solar energy. In fact, today’s wide array of paints and coatings serve as evidence that the industry has been devoted to improving its products — and the world we live in — through the development of advanced technologies.
Formulation and Process Development in the 21st Century
Two drivers have dominated formulation and process technology in the last decade: sustainability and
cost efficiency. Ever lower limits on VOCs and HAPS, a growing demand by consumers for ‘green’
products, and rising energy and raw material prices have driven formulators to seek multifunctional
ingredients with environmentally friendly profiles, and processes with a minimal environmental
footprint, all while improving efficiency and performance.
Advanced Technologies for Formulation
Waterborne, high solids solvent-based, and UV-cured coatings have taken center stage in many applications, with much R&D effort targeted at developing coatings that compete on price and performance when compared to traditional solvent-based paints. These coatings meet regulatory and consumer requirements, have low-to-no VOCs, exhibit low-to-no odor, and can be applied over an expanded temperature and humidity range. They also have properties that equal or beat their solvent-based counterparts.
Some of these formulations incorporate new hybrid resins that combine two or more different types of chemistries that each contribute desirable and sometimes contrasting properties. This technology has made it possible to achieve improved performance in water-based coatings.
Others have relied on novel additives and resins that incorporate silicon or florine atoms that impart special capabilities to coatings used in high-performance applications, such as the aerospace and marine industries. Many of these compounds are multifunctional in nature, reducing the number and quantity of ingredients required.
Nanomaterials — from nanoparticles to nano-sized resins — have been shown to enhance performance in a number of ways, imparting improved anti-microbial, anti-static, corrosion and scratch resistance, mechanical and optical properties, as well as modifying surface energies and providing self-cleaning capabilities.
For some, the focus has been on replacement of active ingredients that are effective but have negative environmental profiles. For example, new pigments, anti-corrosive agents and biocides have been identified that afford excellent color and appearance, superior rust protection and excellent anti-microbial activity.
Naturally-derived ingredients have become much more widely available too, as ingredient suppliers discover a broad range of new raw materials that afford increased formulating flexibility to coating manufacturers. Both resins and additives prepared from renewable resources have been incorporated into paints used in architectural, industrial, automotive and numerous specialty applications.
Formulators have focused efforts in developing coatings designed to save energy once applied to a surface. Roof coatings containing specially designed resins and pigments contribute to measurably lower cooling and heating costs for many industrial and residential buildings.
Advanced Process Technologies
Paint and coatings manufacturers have not limited their development work to product improvements; They have also made technical advances in both production and application processes in recent years.
Many producers have refined their production equipment and systems to reduce energy and water consumption and dramatically lower emissions to the environment. Extensive recycling, redesign of polymerization reactors and mixing tanks, and new cleaning procedures are just some examples. The use of stir-in pigments and pigments that are more easily dispersable have resulted in reduced waste, lower overall cost and increased color consistency.
Working closely with customers, paint manufacturers have developed new coatings that take less time and energy to dry. Entire steps in the coating process have been eliminated through the introduction of formulations that perform as well with one coat as they did with an older, two-coat system. Advances in spraying equipment and booth technology have also dramatically reduced waste in the application process.
New pre-treatment systems based on zirconium oxide as a replacement for zinc phosphate are another example. These processes require fewer steps, avoid the use of heavy metals and consume less water and energy.
These advances in technology have not come easily. They have been achieved only with a significant investment in time, money and human resources and reflect the commitment of the paint and coatings industry to continuous improvement.
Developing water-based and high-solids formulations that are manufactured in a sustainable way and meet stringent regulatory requirements while providing superior performance has been a challenge the industry has tackled vigorously. Ingredient suppliers, formulators and application equipment manufacturers have worked together to create the most cost efficient and effective products and processes that meet the needs of their customers in all segments of the market.
Ongoing efforts focus on future expectations for the industry, taking into consideration the continued need for minimizing the environmental impact of processes, ingredients and final coatings products. Raw material availability, energy costs, transportation issues, geographical differentiation, global and regional regulatory requirements — are all factors that are considered when developing new binders, additives and solvents for use in paint and coatings formulations.
Smart Technologies of the Future
Future expectations remain high. Numerous technologies in the nascent stages of development will enable the industry to bring about profound changes in performance and durability.
Smart coatings sense a change in conditions in the environment and respond to that change in a predictable and noticeable manner. They have the potential to reduce costs, decrease maintenance requirements, and potentially eliminate hazardous painting/depainting operations.
These coatings can be used to detect corrosion, stress, temperature changes, microbes and other potential problems, and then take some sort of action to repair damage or destroy the cause. Potential applications are endless — corrosion control, camouflage, bio-weapon detection and destruction, medical devices, textiles, electronics. The need for functional surfaces exists in almost every industry.
Peizoelectric paints can be used to measure shock and vibration damage on large structures such as bridges, off-shore platforms and pipelines. Coatings containing thermochromic pigments and polymers can serve as reversible temperature indicators in safety devices or indicators for food packaging.
Numerous methods for creating anti-microbial coatings are also in development. Many of these formulations rely on some form of silver ion to destroy microbes. Others are focusing on the use of titanium dioxide as a photocatalyst to create active oxygen species that kill many different types of microbiologicals. Some researchers are taking a very different approach, and are developing resins with nanoscale features that cause physical damage to the cell walls of microbes.
Photocatalysts have applications in self-cleaning coatings as well. Ultrahydrophobic coatings, too, may provide water repellant capabilities for use as corrosion inhibitors, stain-resistant clothing and antifouling paints.
Self-stratification is a new technique for preparing coatings comprised of different types of tethered resins, each with unique properties. Selection of the appropriate process conditions enables the organization of the coating structure such that the functionality of each resin type is maximized.
As these examples suggest, the potential for new technological advances in the paint and coatings industry is vast. Manufacturers and their suppliers are working diligently to commercialize these new opportunities and bring both enhanced performance and novel capabilities to their customers while further reducing the environmental impact of their operations and their products.
Acrylic — polymers prepared from acrylic acid and its derivatives; acrylic acid (2-propenoic acid) contains both carbon and oxygen functionality; coatings containing acrylic polymers are water-based
Additive, specialty — specially formulated materials designed to affect particular properties in a coating, such as gloss, clarity, hardness, etc.
Alkyd — polyester polymers used to form solvent-based coatings; coating formulations also contain ‘drying oils’ derived from plant or vegetable oils
Antifouling paints — coatings designed to prevent the growth of barnacles and other marine organisms on ships’ bottoms.
Anti-microbial — a substance that kills or inhibits the growth of microorganisms.
Curing agent — chemical used to cause a reaction necessary for formation of the finished coating after the coating formulation has been applied to the surface
Electrostatic deposition — a technique for moving and charging a powder coating so that it is deposited on a grounded substrate or surface
Enamel — a smooth, hard, highly glossy coating; can be based on polyester or other types of polymers; initially referred only to solvent or oil-based paints, but now some waterborne coatings have adopted the term
Epoxy — polymers containing numerous carbon and oxygen linkages; the structure provides chemical and temperature resistance, weatherabilty and other high performance properties; initially only available in solvent formulations, but water-based versions are being developed
High solids — coatings dissolved in solvents where the content of the solids in the solvent is very high (usually 80% or higher)
Inorganic zinc — coatings made from zinc-rich silicate materials that contain no carbon; they are often used as
a base coat over steel to protect the surface in high temperature applications
Photocatalyst — A substance that absorbs light and, in doing so, catalyzes a reaction; catalyst stimulated by action of light.
Piezoelectric — the ability to generate an electric potential (voltage) in response to a mechanical stress
Polyurethane — polymers made from isocyanates, organic compounds that contain nitrogen; also contain carbon and oxygen groups; often used as protective coatings; initially developed as solventborne formulations, but water dispersions are now available
Polymerization — chemical reaction in which two or more small molecules (monomers) combine to form large molecules (polymers, macromolecules) that contain repeating structural units of the original molecules and reflect the percentage composition of the original molecules
Post-cure — the period after curing of a coating is complete but before the coating is completely finished
Powder coating — dry coating formulation that exists in a powder form; applied using electrostatic attractive forces created between the surface and the coating
Pre-treatment — a step required to prepare a metal surface before coating; involves surface cleaning and corrosion protection
Resin — polymer that forms the paint or coating film on a surface; also referred to as the binder
Solvent Vinyl — polymers prepared from vinyl chloride, vinyl acetate or other monomers; coatings containing vinyl polymers are typically solvent-based