The long-term weathering behavior of UV curable clearcoats

Seubert, Christopher; Nichols, Mark; Cooper, V.A.; Gerlock, John L.

doi:10.1016/s0141-3910(03)00079-x

Cited by 32 publications

(16 citation statements)

References 12 publications

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“…Less differentiation was observed between the clearcoats' mar resistance (deformation @ 5 mN). The crosslink density of the UV curable clearcoats is significantly higher (5-8 × 10 −3 mol/cc) than that of the thermally cured clearcoats (~2 × 10 −3 mol/cc) [5,11]. While the nano-scratch behavior is improved by an increase in crosslink density, the increase comes at the price of long-term cracking resistance [11], which implies the flaw sensitivity of the coating has been raised to an untenable level.…”

Section: Exterior Painted Class-a Bodymentioning

confidence: 99%

“…The crosslink density of the UV curable clearcoats is significantly higher (5-8 × 10 −3 mol/cc) than that of the thermally cured clearcoats (~2 × 10 −3 mol/cc) [5,11]. While the nano-scratch behavior is improved by an increase in crosslink density, the increase comes at the price of long-term cracking resistance [11], which implies the flaw sensitivity of the coating has been raised to an untenable level. This increased flaw sensitivity (decrease in fracture toughness) is a common outcome of an increase in yield strength [12,13].…”

Section: Exterior Painted Class-a Bodymentioning

confidence: 99%

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An Overview of the Scratch Resistance of Automotive Coatings: Exterior Clearcoats and Polycarbonate Hardcoats

et al. 2012

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Abstract:The scratch resistance of coatings used on two highly visible automotive applications (automotive bodies and window glazings) were examined and reviewed. Types of damage (scratch vs. mar), the impact on customers, and the causes of scratch events were investigated. Different exterior clearcoat technologies, including UV curable and self-healing formulations were reviewed, including results from nano-and macro-scratch tests. Polycarbonate hardcoat glazings were tested vs. annealed glass samples using a Taber abraser, with the resulting damage analyzed using transmitted haze measurements and optical profilometry. A correlation between the damage seen in glass samples (many smooth, shallow mars) and the best hardcoat samples (fewer, deeper scratches) and the haze measurements was discussed. Nano-scratch results showed similar fracture forces, but measurably improved mar resistance for the hardcoats/glass system compared to exterior clearcoats.

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Section: Exterior Painted Class-a Bodymentioning

confidence: 99%

Section: Exterior Painted Class-a Bodymentioning

confidence: 99%

An Overview of the Scratch Resistance of Automotive Coatings: Exterior Clearcoats and Polycarbonate Hardcoats

et al. 2012

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“…11 These usually absorb the harmful part of the solar spectrum or may deactivate free radicals to reduce photo oxidation rate. 12,13 To lower hydrolytic degradation, several approaches such as use of coatings with highly chemical stable linkages upon water uptake have been adopted. Improved surface hydrophobic and greater crosslinking density are the two scenarios by which water permeability can be diminished.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of weathering performance of two automotive refinish coatings: A case study

Yari

Mohseni

Ramezanzadeh

2008

J of Applied Polymer Sci

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The aim of this study was to compare the weathering performance of two commonly refinish coatings used in a domestic car manufacturer based on polyurethane (PU) and acid-catalyzed alkyd-melamine resins. The replacement of the alkyd-melamine refinish with the PU system was shown to largely lower the reported fading behavior of the monocoat system. For better comparison between the refinish coatings, an original equipment manufacturers' (OEM) topcoat, cured at production line, was also used. Different characterization methods including DSC, atomic force microscopy, thermo gravimetric analysis, DMTA, and Fourier transform infrared spectroscopy were performed to elucidate the changes observed in the optical, mechanical, and weathering performance of studied coatings. It was found that the main reason for the inferior behavior of the acid-catalyzed coatings compared with that of the PU and OEM was due to its low crosslinking density. The poor weathering resistance of the former coatings was attributed to its incomplete curing reaction and therefore, to its immatured film formation.

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“…The research to date, mainly by Decker, 4-7 Valet, 8 and the results presented in previously authored work, 9 has shown that the addition of UVAs, and particularly HALS, significantly improve their weathering performance.…”

mentioning

confidence: 98%

“…These measurements have a resolution of 5 µm and allow for a more comprehensive look at the clearcoats that were studied in previous work. 9 In this work, we report on the photooxidation, UVA, and HALS longevity as a function of depth from the coating surface.…”

mentioning

confidence: 99%

Long-term weathering behavior of UV-curable clearcoats: Depth profiling of photooxidation, UVA, and HALS distributions

Seubert

Nichols

Кучеров

2005

J Coat. Technol. Res.

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The long-term weathering performance of two UV-curable clearcoat systems was studied using in-plane microtomy in combination with infrared spectroscopy, UV spectroscopy, and ESR spectroscopy. Oxygen transport characteristics were also studied using the half-time method. The photooxidation versus depth profile was highly dependant on the presence of hindered amine light stabilizers (HALS) for both coating systems. Ultraviolet light absorbers (UVA) had little effect on the photooxidation profile. A photooxidation gradient was formed in both clearcoats due to a reduction in oxygen solubility when compared to standard thermoset clearcoats. This gradient was only seen in formulations not containing HALS.A utomotive clearcoats continue to evolve due to a variety of driving forces that include environmental regulations, customer performance demands, and cost pressures. High-solids solventborne 1K and 2K clearcoats are currently the industry standards in North America. However, super high-solids, powder, waterborne, and slurry clearcoats either have been recently introduced or are in advanced development. Each of these clearcoats offers reduced VOCs in comparison to conventional thermoset clearcoats, but all come with performance or cost compromises as well.Another class of clearcoats being developed, but not yet commercial for automobile bodies, is UV-curable clearcoats. UV-curable clearcoats typically crosslink via free radical polymerization upon exposure to UV radiation. These coating systems are typically mixtures of oligomers, monomers, solvents, one or more photoinitiator (PI), and other additives for weatherability enhancement, including ultraviolet light absorbers (UVA) and hindered amine light stabilizers (HALS). 1 UV-curable coatings are well established in such industries as telecommunications, wood finishing, and flooring manufacturing, but have only recently been seriously considered by the automotive industry for body paint applications. These coatings are of major interest for a variety of reasons, the most widely discussed of which is the potential for outstanding scratch resistance. This improved scratch resistance is mainly due to the extremely high crosslink density that can be achieved by UV-curable coatings. 2,3 In addition, UV-curable clearcoats have the potential to offer lower VOCs, improved process efficiency, shorter curing times, and lower energy consumption. These potential process advantages must be weighed against issues associated with reparability, adhesion, yellowing, and curing shadowed areas on highly contoured objects. One solution that addresses the shadowing issue is to utilize both thermal and UV curing to process the clearcoat. These systems, known as dual cure systems, allow the partial thermal cure of shadowed regions while giving the properties of full UVcure systems in unshadowed regions.Because UV-curable coatings have not been used extensively in outdoor environments, their long-term weathering behavior is largely unknown. The research to date, mainly by Decker, 4-7 Valet, 8...

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The long-term weathering behavior of UV curable clearcoats

Cited by 32 publications

References 12 publications

An Overview of the Scratch Resistance of Automotive Coatings: Exterior Clearcoats and Polycarbonate Hardcoats

An Overview of the Scratch Resistance of Automotive Coatings: Exterior Clearcoats and Polycarbonate Hardcoats

Comparisons of weathering performance of two automotive refinish coatings: A case study

Long-term weathering behavior of UV-curable clearcoats: Depth profiling of photooxidation, UVA, and HALS distributions

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