Polyester Powder Coatings Research Articles

Sustainable lignin-based powder coatings doped with ZnO displayed excellent UV resistance properties

Lignin with increased polyhydroxyl content (LOH) was prepared via a one-pot synthesis using enzymatically hydrolyzed lignin (EHL) as the raw material. The modified structure and hydroxyl content of LOH were analyzed using FT-IR, 1H NMR, and 31P NMR. LOH was blended with zinc oxide (ZnO), polyester resin and hydroxyl alkyl amide (HAA) to prepare polyester powder coatings. The anti-UV properties of the coating were significantly enhanced by the addition of LOH and ZnO. The coating exhibits exceptional adhesion, rating at level 0, and achieves a pencil hardness of 7H. The gel time for the coating is 195 s, and it has a 5-degree Celsius increase in melting temperature, which greatly enhances its storage stability. Considering a range of factors, the formula LOH7.5 % has been identified as the optimal composition. The results of this study demonstrate an easy approach to developing sustainable lignin-based powder coatings with excellent properties.

Zinc-rich polyester powder coatings with iron Phosphide: Lower zinc content and higher corrosion resistance

Many conductive fillers such as carbon black, carbon nanotube and graphene, have been developed to reduce zinc content for zinc-rich coatings, but very few of them could reduce zinc content by 10 % while maintaining the original corrosion protection ability. The carbon-based conductive additives have the issue of corrosion promotion after cathodic protection. In this study, low-cost iron based conductive additive, iron phosphide was used to reduce zinc content in environmentally friendly zinc-rich polyester powder coatings. We investigated the anti-corrosive performance of the prepared coatings by open circuit potential, electrochemical impedance spectroscopy measurements and neutral salt spray tests. The corrosion products were analyzed with Raman spectroscopy, X-ray diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. It was found that iron phosphide, due to its conductive nature, inert chemistry, activation function and barrier effect of the lamellar shape, can establish cathodic protection at a low zinc content of 45 wt% with an active protection period of 20 days. It can replace 10 wt% of zinc in 75 wt% zinc-rich polyester powder coatings while maintaining the original cathodic protection ability, as long as 86 days for a 40 μm film. In addition, iron phosphide can significantly inhibit localized corrosion and decrease corrosion creepage by about 20 % during 2500 h salt spray tests. Moreover, a possible corrosion protection mechanism for iron phosphide in zinc-rich polyester coatings was proposed.

Synergistic Effect of Nanoclay and Barium Sulfate Fillers on the Corrosion Resistance of Polyester Powder Coatings

Nanoclay has proven to be an active anti-corrosive additive due to the self-repairing effect from nanoclay swelling and expansion, except for its passive barrier effect due to the high aspect ratio. But it is still uncertain how these effects of nanoclay are intertwined with the other components in a complex coating system in corrosive environments. In this study, we examined the combined effects of nanoclays of two particle sizes with a commonly used cost-reducing filler, BaSO4. By employing neutral salt spray tests, electrochemical analysis, and surface characterization, we identified the optimal conditions for achieving a strong barrier effect. Surprisingly, a relatively low nanoclay dosage of 2% combined with BaSO4 filler exhibited synergistic behavior. Nanoclay not only compensated for the reduction in the barrier effect owing to the addition of BaSO4 by offering self-repairing and barrier effects, but also overcame the delamination issues observed at higher nanoclay dosages (4% and above). The coating panel with 2% larger nanoclay and BaSO4 showed two orders of magnitude higher pore resistance than the coating without nanoclay, remaining at 107 Ω∙cm2 after 25 days of immersion. As a result, this coating panel demonstrated significantly slower corrosion expansion and reached a lifetime of 2500 h when creepage exceeded 2 mm in salt spray tests. This study contributes to a full understanding and proper utilization of nanoclay for high-performance, smart anti-corrosive coatings.

Corrosion, electrical and thermal behaviour of graphene modified polyester powder coatings

Corrosion, electrical and thermal behaviour of graphene modified polyester powder coatings

Corrosion, electrical and thermal behaviour of graphene modified polyester powder coatings

This work investigates polyester powder coatings containing graphene on aluminium alloy AA6060. The coatings were developed with a multifunctional approach in order to combine efficient barrier properties and high electrical and thermal conductivity. Graphene contents up to 10 wt% were introduced in the composite powder coatings. The barrier properties were investigated by means of electrochemical impedance spectroscopy (EIS) in 0.1 M NaCl solution. This technique was also employed to obtain information about the electrical parameters of the coatings. Although barrier properties remain high over immersion times up to 35 days, a strong increase of coating capacitance and a decrease of coating resistance were observed by EIS for the coatings with graphene content above 1 wt%. Impedance data were interpreted on the base of the electrical percolation theory in order to correlate the increase of capacitance and the decrease of the resistance to the existence of graphene-rich agglomerates in the composites coatings. Moreover, the thermal behaviour of the composite powder coatings was preliminarily evaluated indicating that the introduction of graphene can improve heat dissipation.

A Mechanistic Study on the Anti-Corrosive Performance of Zinc-Rich Polyester/TGIC Powder Coatings

Powder coatings represent an environmentally friendly VOC-free alternative to widely used solvent-borne zinc-rich coatings, with economic and ecological benefits. In particular, powder coatings have several advantageous properties, such as chemical resistance and mechanical strength. However, the performance and characteristics of polyester-based zinc-containing powder coatings remain unknown. In this study, the corrosion performance of polyester powder coatings containing up to 80% zinc is compared. Electrochemical and salt-spray testing results indicate that coatings formulated with 80% zinc demonstrate superior anti-corrosive properties than coatings with lower zinc dosages. Two distinct behavioral phases of the coating with 80% zinc were observed by measurements of open circuit potential (OCP) and polarization resistance (Rp) during immersion tests—a phase indicative of a barrier effect and a phase consistent with galvanic protection. The evolution of the coating was further characterized and interpreted as five stages by electrochemical impedance spectroscopy (EIS), and the mechanistic details were discussed. This UV-resistant single-layer powder coating has the potential to replace the commonly used high-VOC multi-layer liquid coating systems at a significantly lower cost.

Influence of Branching on Network Formation and the Thermomechanical Properties of UV-Curable Polyester Powder Coating Resins

Influence of Branching on Network Formation and the Thermomechanical Properties of UV-Curable Polyester Powder Coating Resins

Urethane methacrylate reactive diluents for UV-curable polyester powder coatings

Urethane methacrylate reactive diluents for UV-curable polyester powder coatings

Urethane methacrylate reactive diluents for UV-curable polyester powder coatings

Three urethane methacrylates, one monofunctional derivative and two di-functional derivatives with different chain lengths were used as reactive diluents in UV-curable polyester powder coatings. Each reactive diluent was formulated with a methacrylated polyester oligomer using conventional melt extrusion techniques. The effect of these compounds on zero-shear melt viscosity was investigated. Incorporation of 10 wt% reactive diluent effectively reduced the viscosity by an order of magnitude. After UV-curing, the viscoelastic, thermal, and mechanical properties of the films were characterized using dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, and tensile tests. The type and concentration of reactive diluent that was used directly influenced the glass transition temperature, modulus, % elongation-at-break, and crosslink density. Of the two di-functional reactive diluents that were used, the derivative that contained a shorter methylene spacer group resulted in more heterogeneous crosslinked networks.

Investigation of the Performance of Fumed Silica as Flow Additive in Polyester Powder Coatings

Fumed silica is one of the most commonly used flow additives in the powder coating industry. To investigate the influence of the properties of fumed silica on powder coatings, three different types of fumed silica, Aerosil R812, R972, and R8200, were selected and introduced to an ultra-high-gloss powder paint by the dry-blending method with preset mixing conditions and times. Their effect on the powder flowability, coating application related properties and film properties were carefully studied. The angle of repose (AOR) and bed expansion height data, which represent the semi-dynamic and dynamic flowability of powders respectively, show a strong flowability enhancement for the powders with additives, and R812 exhibits the best performance compared to 8200 and R972, mainly due to its high hydrophobicity and specific surface area. For the ultra-high-gloss powder paint, all the flow additives cause slight gloss reductions, surface roughness increase and a significant effect on the distinctness of image (DOI). The addition of R972 is beneficial to the transfer efficiency of powders compared with the other two, while the additives impose only a minor influence in the Faraday cage effect. The melting and curing dynamics, i.e., gel time, and inclined plate flow, are not affected by the flow additives.

Corrosion Resistance of Polyester Powder Coatings Using Fillers of Various Chemical Nature

In the article the effect of fillers of various chemical nature on the corrosion resistance of polyester powder coatings in terms of flaking widths and corrosion expansion widths in accordance with DSTU ISO 4628-8: 2012 was reviewed. According to the results of studies, the effectiveness of the use of fillers to increase the corrosion resistance of the powder coating varies depending on the average particle size and crystalline form of the filler was found. As a rule, in order to receive a powder coating based decorative coating you should apply only one layer of paint, while liquid coatings require applying several layers; this increases the time of coating production. The powder coating can be easily utilized and recycled, thus the economic feasibility of production increases.

Analysis and fate of the hindered amine light stabilizer in polyester powder coatings using high performance liquid chromatography / time of flight mass spectrometry

Analysis and fate of the hindered amine light stabilizer in polyester powder coatings using high performance liquid chromatography / time of flight mass spectrometry

Analysis and fate of the hindered amine light stabilizer Tinuvin 622 in polyester powder coatings using high performance liquid chromatography / time of flight mass spectrometry

Hindered amine light stabilizers are used to protect polymers from heat- and light-induced degradation. In this study the oligomeric stabilizer Tinuvin 622 was analysed in-depth employing high performance liquid chromatography/time of flight mass spectrometry (HPLC/TOF-MS) to differentiate products of different manufacturers in respect of their terminating groups and oligomer length. Additionally, the behaviour of the stabilizer in uncured and cured polyester powder coatings was investigated regarding its interaction with the other coating components and chemical changes during the crosslinking process. The extraction efficiency was determined as a function of oligomer length and coating colour.

Determination of Triglycidyl Isocyanurate in Workplace Air.

Triglycidyl isocyanurate (TGIC) is a white solid in powder or granular form. TGIC does not occur naturally in the environment. It is intentionally manufactured and used as a crosslinking agent or hardener to produce polyester powder coatings. TGIC may cause genetic defects. This article presents the method of TGIC determination in workplace air using high-performance liquid chromatography (HPLC) with a diode-array detector (DAD). The method is based on the collection of TGIC present in the air on a polypropylene filter, extraction with acetonitrile, and chromatographic analysis of the solution obtained in this way. The determination was carried out in the reverse-phase system (mobile phase: acetonitrile: water) using an Ultra C18 column. The measurement range is 2 to 40 µg/m3 for a 720 liters air sample. Limit of detection (LOD) is 23 ng/m3 and limit of quantification (LOQ): 70 ng/m3. The method can be used for assessing occupational exposure to TGIC and associated risk to workers’ health.

AkzoNobel launches range of sustainable polyester powder coatings

AkzoNobel launches range of sustainable polyester powder coatings

Thermosetting powder coating for asphalt pavement

The high temperature in asphalt pavement during summer accelerates the rutting and aggravates the phenomenon of urban heat island (UHI). One of the mitigation methods is the use of heat-reflective coating (HRC) on asphalt pavement. However, conventional HRC faces some challenges such as poor abrasion resistance, poor skid resistance and environment pollution. In this paper, a new type of coating, named thermosetting powder coating (TPC), was developed for reflecting heat off asphalt pavement. Four types of TPCs, including the polyester powder coating (PPC), modified polyester powder coating (MPPC), polyester/epoxy powder coating (PEPC) and modified polyester/epoxy powder coating (MPEPC) were made. Meanwhile, A type of conventional HRC was chosen as a reference. Performances tests were conducted to evaluate the cooling effect, skid resistance, abrasion resistance, adhesion strength, anti-glare performance and erosion resistance of the asphalt concrete specimens coated by the TPCs or conventional HRC. Impacts on performances of several factors such as resin type, application rate and texture agent were discussed. Finally, the costs of the TPC and conventional HRC were compared. Results indicate that though the cooling effect and anti-glare performances of these two types of coatings are resembled, the skid resistance, abrasion resistance and adhesion strength of the TPC are better than those of conventional HRC. What’s more, the cost of the former is only 0.1 times of that of the latter. Among four types of TPCs, MPPC is recommended to be used for reflecting heat and its optimum application rate (dosage) is 100–150 g/m2.

Experimental Evaluation of Polyester and Epoxy–Polyester Powder Coatings in Aggressive Media

Protective coatings are the most widely used corrosion protection method for construction materials in different environmental conditions. They isolate metals from aggressive media, making the structure more durable. Today, alongside good anti-corrosive properties, coatings need to be safe for the environment and harmless to those who apply them. The high volatile organic compound (VOC) content in conventional solvent-borne coatings presents a huge ecological problem. A solution for indispensable solvent emission reduction is the application of powder coatings. This study evaluates the corrosion performance and surface morphology of polyester and epoxy–polyester powder coatings. Electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) measurement, salt spray chamber and humidity chamber testing followed by adhesion testing were used to investigate the protective properties of powder coatings. Scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX) was used to analyse the surface morphology and chemical composition, whereas the microstructure and coating uniformity were determined by optical microscope examination. The research revealed a negative influence of coating surface texture on coating thickness and consequently a lack of barrier and adhesion properties. The epoxy–polyester powder coating showed a better performance than the polyester coating. All tested coatings showed uniform structure.

Accelerated weathering degradation behaviour of polyester thermosetting powder coatings

Abstract The development of new products and their introduction in the market need rapid and reliable accelerated durability tests have the capacity to predict the service lifetimes of the materials. In this paper we report time-consuming standardised procedures in order to study the durability and the stability of typical polyester powder coatings, used as surface and structure white decorative finish in external architecture. SUNTEST, UVA and UVB accelerated aging tests were done in order to compare the resistance to weathering degradation of different kinds of coatings, four of standard durable and seven of superdurable type. The stability of the single formulation was determined through the evaluation of some chemicals and physical changes on aged samples respect the unaffected one. ATR measurements showed as the degradation differ mainly on the specific type of reactive binder system meanwhile the DSC measurements showed if the accelerate aging processes involved hydrolysis or an increase of the degree of polymerization. A good resistance, in term of gloss and colour retention, were also determined.

Polyester Powder Coatings: TGIC vs. HAA

Polyester Powder Coatings: TGIC vs. HAA

Effect of inhibitor-loaded halloysites and mesoporous silica nanocontainers on corrosion protection of powder coatings

Abstract We carried out the comparative study of the effect of inhibitor-loaded nanocontainers on the corrosion protection performance of polyester powder coatings by neutral salt-spray test (5% NaCl, 35 °C, different time). Halloysites and mesoporous silica particles loaded with corrosion inhibitor 8-hydroxyquinoline were homogeneously distributed in powder coating effectively reducing corrosion of the metal substrate over 1000 h of salt-spray test. Addition of only 2 wt.% of inhibitor encapsulated either in halloysites or in mesoporous silica particles to the powder coating is sufficient to decrease the delamination effect by >4 times and to suppress the formation of the blisters on the low carbon steel substrates.