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The past year marked a rebound in powder coating revenues, as well as investment in R&D. In particular, both the North American and Latin American powder markets showed growth of 3.5% and 1.8%, respectively, in 2022. These growth figures coincided with an introduction of several innovations spanning advancements in sustainability, low-temperature cure, corrosion resistance, outdoor durability, thin films, and thermoplastic application technology.
Sherwin-Williams recently introduced a powder coating product line based on post-consumer recycled plastic. Powdura® ECO powder coatings are formulated with polyester resins based on recycled polyethylene terephthalate plastic (rPET). Earlier versions of Powdura® ECO powder coatings were based on pre–consumer waste plastic that is generated in factories. This latest development will have an impact on recycling post-consumer plastic, mainly from beverage bottles.
Sherwin-Williams boasts that one pound of Powdura ECO TGIC/TGIC-free coatings contains the rPET equivalent of roughly 16 16-ounce water bottles, dependent on final product formulation. They estimate that one pound of Powdura ECO hybrid coatings contains roughly 7-10 16-ounce water bottles, dependent on formulation.
Pengchen (Simon) Yang, Ph.D., a senior researcher in allnex’s Corporate Innovation Group located in Wageningen, Netherlands, introduced a potentially game-changing powder technology at the 2023 European Coatings Conference. This breakthrough was described in his presentation, “Ultra-low temperature curing powder coating via real Michael addition.”
Dr. Yang’s work introduces a new chemistry to the low-temperature-cure powder coating universe. This fascinating technology is based on real Michael Addition (RMA) chemistry that includes an innovative catalysis system that provides cure latency to this highly reactive chemistry. An RMA reaction relies on a combination of a “Michael donor” in the form of a nucleophile, with an α,β-unsaturated carbonyl to create a Michael adduct. The allnex team, led by Dr. Yang, crafted this chemistry into solid polymers/oligomers that are extrudable and capable of film formation at relatively low temperatures (< 120°C). In addition, they are reportedly stable at room-temperature storage conditions.
This chemistry comprises two crosslinkable species: A) a material containing C-H acidic moieties and B) an unsaturated polymer. The most preferred component A is a malonate functional polyester resin, and methacrylated polymers (polyester, epoxy, or urethane-based) are the most preferred B component.
The catalysis system is rather complex and is based on a catalyst precursor (P1) in combination with a catalyst activator (C1). P1 is a weak base (DABCO™ or tetramethyl guanidine) that reacts with C1, generally an epoxide compound, to produce a strong base catalyst. The epoxide compound can be TGIC, GMA acrylic resin, or Araldite™ PT-910/912. This catalyst technology is quite reactive; therefore, a retarder (typically a carboxylate) is used to introduce a degree of latency.
Latency is critical to allow processing through conventional extrusion techniques common in the powder coating industry.
Latency is further enhanced by macrophysically separating reactive species in independent compounded mixtures. For example, the C1 catalyst activator may be extruded into binder components independent of the P1 catalyst precursor/retarder blend. Two powder materials are generated and then post-blended into a pseudo-2-K powder mixture that is then applied to a substrate and cured at low temperatures, typically around 110-130°C.
This groundbreaking technology is comprehensively detailed in world patent number WO-2022/236519 A1, which was issued on November 17, 2022. Hopefully ,the powder coating world will take notice of Dr. Yang’s fascinating low-temperature RMA curing technology, and this will open a spectrum of new opportunities for growth into new markets and applications.
Akzo-Nobel debuted Interpon W, which is a product group specially formulated for application to heat-sensitive substrates. These products can be used to coat wood and engineered boards, as well as various plastics, gypsum, and plastic composites. Interpon W includes thermoset as well as UV-curable powder technologies.
allnex resins is also supporting the development of low-temperature powder coatings with the introduction of ultra-low-temperature-cure polyester resins. These include Uvecoat (UV cure) and Crylcoat (thermoset) resins specifically designed to cure at temperatures ranging from 80-135°C.
UV-Cure Powder Coating
Keyland Polymer (Cleveland, Ohio) is responding to increasing interest in Europe for UV-cured powder by opening an expanded resin development laboratory in Barcelona. Staffed with six resin chemists and technicians, the lab will be capable of conducting small- and pilot-scale reactions, as well as developing new resins for UV-cured powder coatings and other UV-curable materials.
Evan Knoblauch has moved to Barcelona and is Keyland Polymer UV Materials Spain’s European business manager. Their focus is the development and manufacturing of UV-curable powder coating resins for heat-sensitive substrates, wood, MDF, plastics, composites, and carbon fiber. The next phase of this expansion is the addition of a UV powder formulation and application test and evaluation laboratory. This will enable them to accelerate the pace of not just resin development but UV powder process and performance validation.
Concerns regarding the rising costs of energy, energy supply uncertainty, and water availability make UV-cured powder coating a highly desirable alternative to thermoset powder coatings and waterborne liquid paints and coatings. In addition, managing thermal deformation and surface conditions that compromise adhesion are critical when coating any heat-sensitive material. UV-cured powder has a significant time and thermal advantages over many ultra-low-bake (ULB) or low-bake powders. Keyland claims that its UVP1300 resin is unsurpassed in processing and performance.
Considerable focus has been placed on improved corrosion resistance of powder coatings with performance advancements in primers and topcoats. AkzoNobel’s Interpon team recently commercialized their Redox Plus range of powder primers that give enhanced corrosion protection across a range of metal substrates, from mild steel to aluminum. They can protect products for ISO 12944-2 C5 environment conditions for seven to 15 years while providing more than 25 years of durability in a C3 corrosivity level. Interpon’s Redox Plus is also free from volatile organic compounds (VOCs).
Interpon debuted the Redox Plus range of powder primers with 3Brothers (Cairo, Egypt), a leading international lighting design and manufacturer. Egypt has many extremes of temperature, with high salinity in the air and frequent sandstorms. The Redox Plus range of powder primers were coupled with a UV-resistant powder topcoat to provide the most effective protection in the challenging environment of North Africa where the manufacturer’s products are primarily sold.
Axalta has launched Alesta® ZeroZinc UniPrime in the EMEA region. UniPrime is the newest addition to its Alesta ZeroZinc primer range and the first premium universal thermosetting powder primer available anywhere in the world. Like the other products in the Alesta ZeroZinc range, the ZeroZinc UniPrime has been formulated in accordance with high-density crosslinking (HDC) technology to protect against corrosion and help extend the working life of painted structures. In addition to meeting stringent anti-corrosion requirements, UniPrime is easy to apply.
PPG recently introduced its Envirocron Primeron primer powder portfolio, which is designed to provide high corrosion resistance for metal substrates, including steel, hot-dip-galvanized steel, metalized steel, and aluminum. PPG says the portfolio has been tested according to the ISO 12944-2 corrosivity categories and is approved by the Qualisteelcoat International quality label for coated steel. The series covers a range of requirements depending on end use, operating environment, and application to challenging substrates.
Thermoplastic Powder Coating
Axalta Coatings recently launched a high-performance thermoplastic powder, Abcite® 2060, designed for flame spray applications. This product is based on ethylene copolymer chemistry and is touted for its ability to provide exceptional corrosion resistance in a single-layer coat. The powder is applied in the field using a flame-spray technique to grit-blasted metal. This groundbreaking technology provides a coating that protects surfaces in extremely adverse environments as it passes the demanding CX specification of the ISO 12944 6/-9 standard for steel and galvanized substrates. It does all this without the need for a primer coat.
Abcite® 2060 is highly resistant to alkali and acid attack, as well as intense UV and weathering exposure. Films based on this co-polymer have a service temperature that ranges from -60°C to 75°C and provide excellent impact and abrasion resistance. Edge coverage is good, and the recommended film thickness is 400-3,000 microns. In addition, this product is BPA, VOC, and halogen free.
With this latest innovation in material technology, the high-volume use of powder coatings outside the controlled environment of a factory setting can be realized. In addition, the well-known advantages of powder coatings (e.g., no VOCs, high utilization efficiency, low toxicity, and high durability) will provide a highly sustainable solution for assets requiring high durability in the field.
Axalta recently announced the launch of a new thermoplastic powder coating designed to protect buildings and save lives in the event of fires. Plascoat® PPA571 FR can be deployed in a range of environments to provide fire resistance and act as a barrier to additional damage caused by the spread of flames. Unlike many other flame-retardant coatings, Plascoat® PPA571 FR does not contain a halogen constituent, such as chlorine or bromine, which minimizes the evolution of toxic fumes and their associated negative environmental impact.
Plascoat® PPA571 FR complies with several industry certifications, including British Standard 476, EN 45545-2 European Railway Standard for Fire Safety, British Standard 6853, International Maritime Organization FTPC standard, and UL 94 -Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.
Axalta Coating Systems recently announced the launch of its latest ICONICA collection of Alesta® SD powder coatings aimed at the U.S. The collection, composed of coatings based on a super-durable polyester resin system, combines higher grade pigments and stabilizers with an exterior durability that extends the life cycle of architectural projects. ICONICA is compliant with international standards such as Qualicoat Class 2 and AAMA 2604 and comes with a warranty up to 25 years.
ICONICA identifies a palette of 40 key finishes that capture the essence of our time, identified by research carried out by the team of Axalta color experts. Fourteen new colors were added to the collection, with innovative additions such as Grained Stone, Russet Scarabea, and Lunar Chrome, reflecting the degree of change witnessed over the past five years following major disruptive events such as the climate crisis and pandemic.
These products were developed with a key focus on the environment. The Alesta SD range of powder coatings is solvent- and VOC emissions-free and produces significantly less hazardous waste compared with solvent-borne coatings solutions, assisting in obtaining LEED credits for projects on which they are used and are supported by an EPD certification.
Handling Ultrafine Powder Particles
Although it has been an industrial coating process of choice for metal substrates for over 50 years, one nagging “Holy Grail” in powder coating technology is the ability to consistently apply thin films. Fundamental to powder coatings’ remarkable performance profile is the relatively thick film build inherent to this technology. Whereas many liquid paints can be easily applied at film thicknesses of 10- 15 microns, powder coatings struggle to form continuous films below 30 microns. This is partly due to the electrostatic application process, which rapidly delivers particles to a substrate and creates a relatively thick coating.
The particle size distribution of powder has a significant influence on film formation. Conventional powder coatings comprise particles ranging from approximately 1.0 micron upwards to about 90 or 100 microns. Median particle size typically ranges between 30-35 microns. Consequently, the formation of a thin film (i.e., < 10 microns) is impossible as large particles are not conducive to coalescing to form films significantly thinner than the diameter of a particle.
Technologists have investigated using ultrafine (< 25 microns) powder particles to generate thin films; however, powders in this particle size range are difficult to handle. Ultrafine particles, by their nature, exhibit poor dry-flow properties due to inter-particle interactions, mainly clumping and bridging from Van der Waal forces. The dry handling properties of ultrafine powders can be significantly improved with the addition of fluidization agents. However, film appearance and performance are compromised as these fluidization additives have high oil absorption that significantly increases melt viscosity. Excessively high melt viscosity creates undesirable surface texture, low-gloss films, and film defects.
Interesting work attempting to tackle this problem has been recently reported in the Progress in Organic Coatings journal. Professor Jesse Zhu and his colleagues at Tianjin University and the University of Western Ontario published their findings in “Enhanced flowability and film properties of ultrafine powder coatings modulated by modified flow additive.” The paper aptly describes the problem with handling ultrafine particles and conventional technology used to enhance flowability of powder coating particles. Commercially available nano-silica and nano-alumina are typically incorporated at 0.2-0.5% levels to improve the flowability of powder coatings. Higher levels create what these investigators call the “bridge effect.” In addition, the aforementioned film quality issues are produced by higher levels of these nanomaterials.
Zhu and his colleagues have investigated the use of resin-coated nano-silica flow additives, with promising results. A traditional nano-silica flow additive was encapsulated with either “hybrid” or polyester resin commonly used in powder coating formulation platforms. These coated nanoparticles were then incorporated into ultrafine polyester and “hybrid” powder coatings.
The ultrafine powder coatings modified with these encapsulated nano particles exhibited enhanced fluidization and handling properties without impairing film appearance and performance. Details of this research can be found in Volume 179, June 2023 issue of Progress in Organic Coatings.
The explosive growth in electric vehicles (EVs) has proven to be a gold mine for powder coating producers. Powders have been developed to meet the demanding requirements of the electric power train involving thermal dissipation, high dielectric strength, and excellent corrosion resistance.
AkzoNobel has launched a new range of Resicoat EV powder coatings to protect the battery system and electrical components of a new generation of EVs. The company recognized that the success of EVs is dependent on the performance of the battery and associated systems and that these components are highly impacted by the environment. The Resicoat EV powder coating line improves the performance of the battery by providing insulation from electric current and protection against corrosion. Battery life is significantly extended, and batteries maintain performance longer.
Each of the five product ranges developed within the Resicoat EV range has been specifically designed to enhance the safety and performance of the EV power systems. They have excellent electrical insulating properties and enhanced thermal management to help protect the battery systems, motors, and electrical storage units.
Arkema introduced two new polyamide 11 powder coating grades for use in EV battery systems and other related applications. Rilsan® T Orange 7706 is a fluid bed dipping grade designed to achieve high thickness (500 µm) in one dip. Rilsan® ESY Orange 7705 is a electrostatic coating grade for components that require thinner insulation. Both products can be applied in one coat and do not require a primer.
Each grade achieved CTI ratings greater than 600 volts and fire resistance class UL 94 V-0. In addition, these materials offer ease of processing due to their high level of flexibility and ability to be easily masked. Rilsan® polyamide 11 is a versatile polymer that is 100% bio-based (derived from castor oil), in addition to powder coating grades.
On the bright side, PPG has recently debuted a retroreflective powder coating product that provides reflectivity in low light environments. The company partnered with Lyft with its new high-visibility e-bikes. This program was launched in the Bay Area in California and has expanded into Chicago and New York City. Time magazine recognized Lyft’s retroreflective e-bike as one of “The Best Inventions of 2021.” Paul Bradley led PPG’s product development efforts with this new technology, which is dubbed Envirocron® LUM retroreflective powder.
Innovation in powder coating technology is alive and well thanks to the creativity and hard work of powder formulators and polymer scientists. The emerging needs of the dynamic industrial coatings industry are being met by a renewed effort to innovate and provide ecologically friendly and sustainable powder technology. The latest advancements are opening up new opportunities in alternative substrates, e-transportation, highly corrosive environments, and thin film powder coatings.
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1. Powder Coating Institute. Global Powder Coatings Quarterly Newsletter, 1st Quarter 2023.
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