Depthwise Viscosity Gradients in UV‐Cured Epoxy Coatings

Song, Jin Oh; McCormick, Alon V.; Francis, Lorraine F.

doi:10.1002/mame.201100362

Cited by 13 publications

(13 citation statements)

References 22 publications

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“…The characterization of thin films where materials are subject to chemical reactions and transformations is a challenge . MRS allows one to make a step forward and study polymerization and sol/gel transitions in thin films.…”

Section: Characterization Of Rheological Properties Of Thin Films Witmentioning

confidence: 99%

“…Characterization of thin coating films during composite manufacturing remains challenging. Different experimental methods have been proposed and developed for in situ characterization of rheological properties of thin films and coatings . It appears that unique features of rotation of ferromagnetic nanorods can be used for characterization of very thin films when other methods fall short.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Kornev

2016

Adv Funct Materials

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3796 wileyonlinelibrary.com nanorods as the fi llers are believed to be the best candidates for materials working in extreme environment and hence they are on demand in aerospace and space exploration applications. [39][40][41][42][43] In composite fi lms needed for inductor and antennae applications, the alignment of magnetic particles is required to increase the high frequency permeability and to lower the hysteresis losses. [44][45][46][47] In applications to manufacturing of high density recording fi lms and discs, spin alignment is required to carry the recorded information when spins in magnetic nanorods are prone to align parallel to the nanorod axis. [ 37,[48][49][50] In optical applications, magnetic liquid crystals are attractive candidates for making reconfi gurable magnetooptical devices with the fast time response measured in milliseconds. [11][12][13][14][15][16][17][18][51][52][53] In all these applications, one needs to control the alignment of magnetic nanorods in liquid medium. Therefore, this problem is actively discussed in the literature; however, the general strategy for making macroscopic samples with ordered nanorods has not been developed yet and it remains the main challenge of materials engineering [32][33][34][35][39][40][41][42]54 ] Processing of multifunctional coatings and thin fi lms require many steps and hence one needs to control the fi lm properties at each step.Rheological properties of the fi lms at each stage of their processing play the most important role in nanorod ordering and keeping nanorods in place. Characterization of thin coating fi lms during composite manufacturing remains challenging. Different experimental methods have been proposed and developed for in situ characterization of rheological properties of thin fi lms and coatings. [ 20,[25][26][27][55][56][57][58][59][60] It appears that unique features of rotation of ferromagnetic nanorods can be used for characterization of very thin fi lms when other methods fall short. Recently introduced magnetic rotational spectroscopy (MRS) with nanoparticles and nanorods allows one to probe fl uid rheology in very thin fi lms and nanoliter droplets. [ 12,20,22,25,60,61 ] MRS takes advantage of a distinguishable behavior of rotating magnetic tracers as the frequency of applied rotating fi eld changes. Unlike many methods based on the analysis of small oscillations, which are diffi cult to interpret when the fi lm is very thin, MRS with magnetic nanorods enjoys analysis of full revolutions of magnetic tracers. [ 20,22,24,25,60,62,63 ] Understanding of the characteristic features of rotation of a single nanorod in complex fl uids and alignment of an assembly

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Section: Characterization Of Rheological Properties Of Thin Films Witmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Kornev

2016

Adv Funct Materials

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“…So, uneven cure results in the form of wrinkles on sample surface. 110 For certain applications where additives are compulsory, another approach was applied, where photoinitiators and additives absorb at different wavelengths. 111 But this approach is not practicable for all kinds of additives and fails to work for certain fillers like CB that absorbs all wavelengths, or titanium dioxide that reflects all.…”

Section: Thick Dimension Epoxy Compositesmentioning

confidence: 99%

Cationically UV-Cured Epoxy Composites

2015

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This review article is a comprehensive study of different approaches utilized by various researchers for UV-cure epoxy composites through the cationic route in the form of transparent or colored composites either in thin films or thick dimensions. Generally UV curing is applied on thin and transparent materials, yet attempts are being made to cure intensely colored and thick composite samples. In recent times, thick sample UV-curing has been actively explored to decrease the processing and fabrication expenses of complex assemblies. In this article, data has been reviewed about epoxy curing with methodological trends, not only in thin films but also in thick samples.

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“…For example, UV-curable coatings can exhibit low gloss surfaces when random wrinkling at their surface arises after UV irradiation. Due to this effect, a large amount of work has been carried out on the fabrication of different surface patterns based on surface instabilities [3,[23][24][25][26][27][28][29][30]. From these studies, it has been established that wrinkle formation on polymer surfaces can be obtained using different strategies.…”

Section: Introductionmentioning

confidence: 99%

“…Their work describes how an initially liquid coating develops a gradient in crosslinking during curing and, thus, the mechanical properties have an associated gradient [31]. This phenomenon is mainly explained by the decrease in the UV intensity throughout the depth of a coating [25,32]. The top layer is crosslinked to a larger extent than the bulk of the film and, thus, behaves like a solid skin.…”

Section: Introductionmentioning

confidence: 99%

Effect of Copolymer on the Wrinkle Structure Formation and Gloss of a Phase-Separated Ternary Free-Radical/Cationic Hybrid System for the Application of Self-Matting Coatings

2022

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Hybrid free-radical/cationic systems can generate phase-separated polymers or interpenetrating networks driven by photopolymerization. In this study, phase separation of a ternary mixture composed of a polybutadiene urethane diacrylate (PBUDA), a cycloaliphatic diepoxyde (CE), and hexanediol dimethacrylate (HDDMA) was investigated. Using systematic variations of the initial composition of the mixture, a miscibility phase diagram of the ternary mixture was established. Based on this diagram, a reactive copolymer (poly(butyl acrylate-co-glycidyl methacrylate) (PBGMA)) was introduced in a reference hybrid system to manipulate the crosslinking network, polymer morphology, and properties (e.g., roughness, gloss, strain at break, and glass transition temperature Tg). When cured as a coating, the ternary hybrid system showed a depthwise gradient of epoxy conversion, and thereby developed a mostly cured skin above a viscous sublayer of uncured monomer. This skin can develop compressive stress due to the swelling from the diffusion of unreacted monomers beneath, and if the compressive stress is significantly high, wrinkles appear on the coating’s surface. This work highlights how both skin thickness and elastic modulus impact wrinkle frequency and amplitude. It was demonstrated that these wrinkle parameters can be manipulated in the ternary system by the addition of PBGMA. We also demonstrated that by employing UV irradiation and varying the PBGMA content, it is possible to engineer coatings that range from smooth surfaces with high gloss to wrinkled topographies with a very low associated gloss.

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Depthwise Viscosity Gradients in UV‐Cured Epoxy Coatings

Cited by 13 publications

References 22 publications

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Ferromagnetic Nanorods in Applications to Control of the In‐Plane Anisotropy of Composite Films and for In Situ Characterization of the Film Rheology

Cationically UV-Cured Epoxy Composites

Effect of Copolymer on the Wrinkle Structure Formation and Gloss of a Phase-Separated Ternary Free-Radical/Cationic Hybrid System for the Application of Self-Matting Coatings

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