... A major advantage of NMR over any spatially resolving optical spectroscopic technique is that... more ... A major advantage of NMR over any spatially resolving optical spectroscopic technique is that even nontransparent coatings can be used. ... After application of a paint film two stages can be distinguished, physical drying and curing. ...
Journal of Polymer Science: Polymer Physics Edition, 1976
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
... While side-chain ordering can be favorable in order to decrease the surface energy also side-... more ... While side-chain ordering can be favorable in order to decrease the surface energy also side-chain crystallization may occur (with perfluoroalkyl side-chains from eight carbon atoms) leading to pronounced instability in thin films and to dewetting [11]. ...
ABSTRACT Polyester-urethane resins are important candidates for high performance, outdoor coating... more ABSTRACT Polyester-urethane resins are important candidates for high performance, outdoor coating applications. Despite their relevance, quantitative information regarding the photodegradation of these materials is scarcely available. In the present study, a model polyester-urethane clearcoat without additives is artificially degraded and the changes in optical properties and chemical composition are studied by UV-VIS spectroscopy and FTIR-ATR microscopy, respectively. The change of the optical properties throughout the coating thickness is quantified and interpreted using a newly developed optical model. Chemical changes are quantified in a depth-resolved manner by combining FTIR-ATR microscopy with optical profilometry in order to visualise the time evolution of compositional gradients during photodegradation by accurate assignment of the correct depth position to all recorded ATR spectra. The rate of change for the concentration of several chemical entities in the model polyester-urethane was found to become constant after the initial stage of weathering. The loss of urethane crosslinks in the coating occurs faster and to a much larger extent as compared to ester bond scission. Results from the optical and the chemical characterisation are combined to propose a kinetic model for ester bond photolysis that provides an estimate of the quantum efficiency of this process.
The effect of three block copolymer dispersants with a poly (2-vinylpyridine) anchor block and a ... more The effect of three block copolymer dispersants with a poly (2-vinylpyridine) anchor block and a poly(ε-caprolactone) buoy block on the dispersing of TiO 2 pigments in a polyester powder coating has been studied with digital image analysis on scanning electron micrographs. The mixing in a lab-scale extruder resulted in a virtually complete break-up of the pigment agglomerates. The average TiO 2 particle size was only slightly reduced after further treatment of the TiO 2 pigments with any dispersant. However, a significant change in the colloidal stability of the dispersions was observed. Without dispersants, the pigments reagglomerated when heated to 200°C and 235°C. This reagglomeration was completely suppressed by the use of dispersants, as a result of a steric layer around the TiO 2 particles.
The partitioning of a micelle-forming octyl phenol ethoxylate surfactant (Triton X-100) between w... more The partitioning of a micelle-forming octyl phenol ethoxylate surfactant (Triton X-100) between water and sunflower oil was investigated and quantified as partition coefficient P, i.e. the ratio of total surfactant concentrations (molecules dissolved and in micelles) in oil and water. Values of P were determined over 5 decades of the concentration in the aqueous phase. Below the critical micelle concentration (cmc), P = 2.0 was found to be independent of concentration over a range of more than two decades. When adding surfactant to an oil-water two-phase system at or beyond the cmc, all extra surfactant accumulates in the water phase, and the value of P reduces accordingly. Arguments are given why emulsification leads to an O/W emulsion while Bancroft's rule as based on the molecular preference of the surfactant for oil (P = 2.0), would suggest the opposite. Bancroft's rule should be taken in its original form, taken into account all oil in both phases.
In this work we show that when producing an emulsion with typical mean drop size of 5 µm, it is p... more In this work we show that when producing an emulsion with typical mean drop size of 5 µm, it is possible to generate or not a large number of negatively charged small drops (smaller than 1 µm in diameter). The existence of the small charged drops is attributed to fact that the induced electrostatic repulsive force can be large enough
ABSTRACT Cross-linked composite PDMS coatings containing luminescent micrometer-sized Ce doped Y3... more ABSTRACT Cross-linked composite PDMS coatings containing luminescent micrometer-sized Ce doped Y3Al5O12 garnet particles were prepared. The garnet particles were homogeneously and individually dispersed across the bulk of the cross-linked composite coatings, which is an important requirement for the potential application of these polymer-based light converter coatings.The thermal and optical degradation of the composite coatings was investigated by TGA and after exposure to high temperature (300°C) and high power visible light irradiation (150W) for long periods of time, under air and atmospheric humidity conditions. The composite coatings were analyzed by SEM and optical microscopy after the heat and light exposure and no phase segregation, coloring or cracking was observed. Microscope–ATR–FTIR spectroscopy confirmed the stability of the composite coatings during the exposure to high temperature and light in the visible range, but small structural changes were revealed in the cross-linked PDMS network, mainly due to the formation of additional cross-links. The cross-linked composite coatings emit white light upon irradiation with a blue light source, even after being exposed to the degradation test, attesting for their potential application in new solid state lighting devices, i.e. high power LEDs.
The rheologicsl behaviour of concentrated suspensions of spherical glass particles can be influen... more The rheologicsl behaviour of concentrated suspensions of spherical glass particles can be influenced drastically by surface pretreatment of the particles. This treatment consisted of silanization with mono-or difunctional organo-silicon compounds. Results from ESCA, IR and SEM analysis strongly suggest that silanixation with the reagent dimethyldichlorosilane (DMDCS) results, depending on the processing, in a more or less homogeneous layer of oligomer and/or polymer. The particles were suspended in an apolar (DOP) and in a polar liquid (glycerol/water). All suspensions exhibited perfect or nearly Newtonian behaviour except DMDCS-coated glass in glycerol/water. With the latter, under oscillatory shear conditions, behaviour of a continuous coagulation network structure was found dynamic moduli are hardly dependent on frequency while network structure breakdown occurred already at the lowest accessible deformation ( 10m3). Under steady shear rate conditions pseudoplastic behaviour was found, with relative differential viscosities at high shear rates (10' s-l) approaching the value of equivalent suspensions of uncoated spheres. Results are interpreted with the giant floe model, according to which macroscopic shear is understood as microscopic slip along shear planes between coagulated domains. The origin of coagulation in these systems is not in van der Waals forces because bond strengths as judged from rheology are too high. Polymer bridging between coating polymers is suggested as flocculation mechanism.
A simple method is described on the preparation of low surface-tension epoxy films via thermal cu... more A simple method is described on the preparation of low surface-tension epoxy films via thermal curing. First a partially fluorinated diamine was synthesized by reacting perfluoroalkyl epoxide with a known excess of diamine. Then a mixture of the fluorinated diamine and diglycidyl ether of bisphenol-A was thermally cured, resulting in films with surface tensions as low as 15mN/m by using
This paper exposes an extension of an activation model previously published by the authors. When ... more This paper exposes an extension of an activation model previously published by the authors. When particles arranged along the compression axis of a sheared suspension, they may overcome the electrostatic repulsion and form force chains associated with shear thickening. A percolation based consideration, allows an estimation of the impact of the force chains on a flowing suspension. It suggests that, similar to mode-coupling models, the suspension becomes unstable before the critical stress evaluated from the activation model is reached. The theory is applicable only to discontinuous shear thickening, and the predictions are compared with results from two experimental studies on aqueous suspensions of inorganic oxides; in one of them hydration repulsion and in the other hydrophobic attraction can be expected. It is shown that the incorporation of non-DLVO forces greatly improve predictions of the shear thickening instability.
Cobalt based catalyst are widely used for curing of alkyd resins. The concern on the carcinogenic... more Cobalt based catalyst are widely used for curing of alkyd resins. The concern on the carcinogenicity of cobalt based catalyst is steadily growing. Therefore, possible alternative catalyst systems are investigated, e.g. based on Mn or Fe. Knowledge of the influence of these catalysts on the spatial and temporal evolution of the solidification of a coating is required to understand the mechanisms involved and to optimize the performance of catalyst. We have studied the curing of alkyd coatings with cobalt (Co) and manganese (Mn) based catalysts, using a high gradient nuclear magnetic resonance (NMR) setup with a spatial resolution of 5 m and Confocal Raman Microscopy (CRM). NMR probes the hydrogen density and the mobility of the hydrogen atoms attached to the polymers, which decreases with increased degree of cross-linking. CRM was used to obtain chemical information by probing the amount of double bonds in the fatty acid side chains of the alkyd molecules. The results indicate that the CRM profiles directly correspond with the observed NMR profiles, which indicates that NMR is a useful tool for depth profiling of coatings during curing. NMR measurements indicate that the curing process of an alkyd coating is strongly influenced by the type of catalyst. In the case of Co a sharp cross-linking front was observed, whereas no front was observed in the presence of a Mn catalyst, even at high Mn concentrations. The front formation in the presence of Co indicates that the oxygen transport limits the curing process, whereas the reactivity of the catalyst is the limiting factor in case of Mn.
... Jozua Laven, and Rob van der Linde. ... The film surface roughness in the 10 μm × 10 μm range... more ... Jozua Laven, and Rob van der Linde. ... The film surface roughness in the 10 μm × 10 μm range is within 5 nm, as observed on a Dimension 3100 AFM from Digital Instruments, Santa Barbara,CA, under tapping mode, and it is therefore not the source for contact angle hysteresis. ...
... A major advantage of NMR over any spatially resolving optical spectroscopic technique is that... more ... A major advantage of NMR over any spatially resolving optical spectroscopic technique is that even nontransparent coatings can be used. ... After application of a paint film two stages can be distinguished, physical drying and curing. ...
Journal of Polymer Science: Polymer Physics Edition, 1976
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
... While side-chain ordering can be favorable in order to decrease the surface energy also side-... more ... While side-chain ordering can be favorable in order to decrease the surface energy also side-chain crystallization may occur (with perfluoroalkyl side-chains from eight carbon atoms) leading to pronounced instability in thin films and to dewetting [11]. ...
ABSTRACT Polyester-urethane resins are important candidates for high performance, outdoor coating... more ABSTRACT Polyester-urethane resins are important candidates for high performance, outdoor coating applications. Despite their relevance, quantitative information regarding the photodegradation of these materials is scarcely available. In the present study, a model polyester-urethane clearcoat without additives is artificially degraded and the changes in optical properties and chemical composition are studied by UV-VIS spectroscopy and FTIR-ATR microscopy, respectively. The change of the optical properties throughout the coating thickness is quantified and interpreted using a newly developed optical model. Chemical changes are quantified in a depth-resolved manner by combining FTIR-ATR microscopy with optical profilometry in order to visualise the time evolution of compositional gradients during photodegradation by accurate assignment of the correct depth position to all recorded ATR spectra. The rate of change for the concentration of several chemical entities in the model polyester-urethane was found to become constant after the initial stage of weathering. The loss of urethane crosslinks in the coating occurs faster and to a much larger extent as compared to ester bond scission. Results from the optical and the chemical characterisation are combined to propose a kinetic model for ester bond photolysis that provides an estimate of the quantum efficiency of this process.
The effect of three block copolymer dispersants with a poly (2-vinylpyridine) anchor block and a ... more The effect of three block copolymer dispersants with a poly (2-vinylpyridine) anchor block and a poly(ε-caprolactone) buoy block on the dispersing of TiO 2 pigments in a polyester powder coating has been studied with digital image analysis on scanning electron micrographs. The mixing in a lab-scale extruder resulted in a virtually complete break-up of the pigment agglomerates. The average TiO 2 particle size was only slightly reduced after further treatment of the TiO 2 pigments with any dispersant. However, a significant change in the colloidal stability of the dispersions was observed. Without dispersants, the pigments reagglomerated when heated to 200°C and 235°C. This reagglomeration was completely suppressed by the use of dispersants, as a result of a steric layer around the TiO 2 particles.
The partitioning of a micelle-forming octyl phenol ethoxylate surfactant (Triton X-100) between w... more The partitioning of a micelle-forming octyl phenol ethoxylate surfactant (Triton X-100) between water and sunflower oil was investigated and quantified as partition coefficient P, i.e. the ratio of total surfactant concentrations (molecules dissolved and in micelles) in oil and water. Values of P were determined over 5 decades of the concentration in the aqueous phase. Below the critical micelle concentration (cmc), P = 2.0 was found to be independent of concentration over a range of more than two decades. When adding surfactant to an oil-water two-phase system at or beyond the cmc, all extra surfactant accumulates in the water phase, and the value of P reduces accordingly. Arguments are given why emulsification leads to an O/W emulsion while Bancroft's rule as based on the molecular preference of the surfactant for oil (P = 2.0), would suggest the opposite. Bancroft's rule should be taken in its original form, taken into account all oil in both phases.
In this work we show that when producing an emulsion with typical mean drop size of 5 µm, it is p... more In this work we show that when producing an emulsion with typical mean drop size of 5 µm, it is possible to generate or not a large number of negatively charged small drops (smaller than 1 µm in diameter). The existence of the small charged drops is attributed to fact that the induced electrostatic repulsive force can be large enough
ABSTRACT Cross-linked composite PDMS coatings containing luminescent micrometer-sized Ce doped Y3... more ABSTRACT Cross-linked composite PDMS coatings containing luminescent micrometer-sized Ce doped Y3Al5O12 garnet particles were prepared. The garnet particles were homogeneously and individually dispersed across the bulk of the cross-linked composite coatings, which is an important requirement for the potential application of these polymer-based light converter coatings.The thermal and optical degradation of the composite coatings was investigated by TGA and after exposure to high temperature (300°C) and high power visible light irradiation (150W) for long periods of time, under air and atmospheric humidity conditions. The composite coatings were analyzed by SEM and optical microscopy after the heat and light exposure and no phase segregation, coloring or cracking was observed. Microscope–ATR–FTIR spectroscopy confirmed the stability of the composite coatings during the exposure to high temperature and light in the visible range, but small structural changes were revealed in the cross-linked PDMS network, mainly due to the formation of additional cross-links. The cross-linked composite coatings emit white light upon irradiation with a blue light source, even after being exposed to the degradation test, attesting for their potential application in new solid state lighting devices, i.e. high power LEDs.
The rheologicsl behaviour of concentrated suspensions of spherical glass particles can be influen... more The rheologicsl behaviour of concentrated suspensions of spherical glass particles can be influenced drastically by surface pretreatment of the particles. This treatment consisted of silanization with mono-or difunctional organo-silicon compounds. Results from ESCA, IR and SEM analysis strongly suggest that silanixation with the reagent dimethyldichlorosilane (DMDCS) results, depending on the processing, in a more or less homogeneous layer of oligomer and/or polymer. The particles were suspended in an apolar (DOP) and in a polar liquid (glycerol/water). All suspensions exhibited perfect or nearly Newtonian behaviour except DMDCS-coated glass in glycerol/water. With the latter, under oscillatory shear conditions, behaviour of a continuous coagulation network structure was found dynamic moduli are hardly dependent on frequency while network structure breakdown occurred already at the lowest accessible deformation ( 10m3). Under steady shear rate conditions pseudoplastic behaviour was found, with relative differential viscosities at high shear rates (10' s-l) approaching the value of equivalent suspensions of uncoated spheres. Results are interpreted with the giant floe model, according to which macroscopic shear is understood as microscopic slip along shear planes between coagulated domains. The origin of coagulation in these systems is not in van der Waals forces because bond strengths as judged from rheology are too high. Polymer bridging between coating polymers is suggested as flocculation mechanism.
A simple method is described on the preparation of low surface-tension epoxy films via thermal cu... more A simple method is described on the preparation of low surface-tension epoxy films via thermal curing. First a partially fluorinated diamine was synthesized by reacting perfluoroalkyl epoxide with a known excess of diamine. Then a mixture of the fluorinated diamine and diglycidyl ether of bisphenol-A was thermally cured, resulting in films with surface tensions as low as 15mN/m by using
This paper exposes an extension of an activation model previously published by the authors. When ... more This paper exposes an extension of an activation model previously published by the authors. When particles arranged along the compression axis of a sheared suspension, they may overcome the electrostatic repulsion and form force chains associated with shear thickening. A percolation based consideration, allows an estimation of the impact of the force chains on a flowing suspension. It suggests that, similar to mode-coupling models, the suspension becomes unstable before the critical stress evaluated from the activation model is reached. The theory is applicable only to discontinuous shear thickening, and the predictions are compared with results from two experimental studies on aqueous suspensions of inorganic oxides; in one of them hydration repulsion and in the other hydrophobic attraction can be expected. It is shown that the incorporation of non-DLVO forces greatly improve predictions of the shear thickening instability.
Cobalt based catalyst are widely used for curing of alkyd resins. The concern on the carcinogenic... more Cobalt based catalyst are widely used for curing of alkyd resins. The concern on the carcinogenicity of cobalt based catalyst is steadily growing. Therefore, possible alternative catalyst systems are investigated, e.g. based on Mn or Fe. Knowledge of the influence of these catalysts on the spatial and temporal evolution of the solidification of a coating is required to understand the mechanisms involved and to optimize the performance of catalyst. We have studied the curing of alkyd coatings with cobalt (Co) and manganese (Mn) based catalysts, using a high gradient nuclear magnetic resonance (NMR) setup with a spatial resolution of 5 m and Confocal Raman Microscopy (CRM). NMR probes the hydrogen density and the mobility of the hydrogen atoms attached to the polymers, which decreases with increased degree of cross-linking. CRM was used to obtain chemical information by probing the amount of double bonds in the fatty acid side chains of the alkyd molecules. The results indicate that the CRM profiles directly correspond with the observed NMR profiles, which indicates that NMR is a useful tool for depth profiling of coatings during curing. NMR measurements indicate that the curing process of an alkyd coating is strongly influenced by the type of catalyst. In the case of Co a sharp cross-linking front was observed, whereas no front was observed in the presence of a Mn catalyst, even at high Mn concentrations. The front formation in the presence of Co indicates that the oxygen transport limits the curing process, whereas the reactivity of the catalyst is the limiting factor in case of Mn.
... Jozua Laven, and Rob van der Linde. ... The film surface roughness in the 10 μm × 10 μm range... more ... Jozua Laven, and Rob van der Linde. ... The film surface roughness in the 10 μm × 10 μm range is within 5 nm, as observed on a Dimension 3100 AFM from Digital Instruments, Santa Barbara,CA, under tapping mode, and it is therefore not the source for contact angle hysteresis. ...
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