Matjaž Kunaver | University of Ljubljana (original) (raw)

Papers by Matjaž Kunaver

Progress in Organic Coatings, 2005

The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samp... more The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samples were prepared by variation of the bonding time and the temperature associated with the production of the powders. SEM micrographs show that only smaller flakes (<10 μm) bond to the surface of the powder. The influence of bonding parameters on the microstructure of the cured coatings was studied using various optical methods. The colour differences measured in four perpendicular reflectance planes and the lightness flop were practically the same for all the coatings. The scattering of infrared light shows that longer bonding times give coatings in which the flakes are distributed more uniformly, parallel to the coating surface. The topmost layer of flakes was seen on SEM micrographs of selectively etched samples. The film forming process and reorientation of flakes were monitored on samples that were prepared at curing temperatures between 80 and 180 °C. It was observed that the flakes reorient from their initial position in the bonded powder to the final position in the effect coating almost completely during the formation of the continuous film. This process was accomplished at 100 °C.

Dyes and Pigments, 2007

A study of gloss reduction of powder coatings was performed using different waxes, fillers and no... more A study of gloss reduction of powder coatings was performed using different waxes, fillers and non-compatible polymer resins (matting hardeners). Coatings with reduced surface smoothness were analysed. Scanning electron micrographs were taken to visualize the surfaces. All of the applied matting additives changed the surface profile of coating. The most interesting surface structural form is provided by wax particles. The average size of these forms was calculated by applying image analysis to some sample micrographs. The surface shape of all of the prepared coatings was analysed using surface profile measurements. Two parameters of these profiles were determined, the average roughness and the mean spacing between the surface peaks. The influence of several physical surface parameters on specular gloss characteristics is discussed.

Journal of Coatings Technology and Research, 2000

The influence of dispersing additives on the electrical conductivity of carbon black pigments dis... more The influence of dispersing additives on the electrical conductivity of carbon black pigments dispersed in an organic medium was studied. Two dispersing additives were examined in combination with two different carbon blacks, a conductive carbon black and a nonconductive one. These carbon blacks differ in the size of their aggregates and in the amounts of surface oxygen groups. Both of

Journal of Wood Chemistry and Technology, 2012

Beech (Fagus Sylvatica) milled-wood lignin was used as a model substrate in a study of lignin-cat... more Beech (Fagus Sylvatica) milled-wood lignin was used as a model substrate in a study of lignin-catalyzed liquefaction in the presence of p-toluene sulfonic acid monohydrate (PTSA) or sulphuric acid as the catalysts. The structural changes that lignin undergoes during the treatment were studied by NMR spectroscopy, FTIR, size-exclusion chromatography, and high-performance liquid chromatography. For the sulphuric acid-catalyzed liquefaction, it was

Bioresource Technology, 2000

In our research, we have utilized high energy ultrasound for the liquefaction of different lignoc... more In our research, we have utilized high energy ultrasound for the liquefaction of different lignocellulosic materials, wood wastes in particular. We developed a highly efficient way of transforming this biomass waste into valuable chemicals. It was found, that the reaction yield in all experiments was high and that the reaction times were shortened up to nine times when using the

Catalysis Today, 2010

A blend of spruce (Picea spp.) and fir (Abies spp.) sawdust was liquefied by an optimized techniq... more A blend of spruce (Picea spp.) and fir (Abies spp.) sawdust was liquefied by an optimized technique in the presence of multifunctional alcohols and p-toluene sulfonic acid monohydrate as a catalyst. The lignin behaviour during wood liquefaction was studied at different reaction times. Samples prepared by the new separation procedure were characterized by quantitative 31P, 13C NMR and by size-exclusion

European Polymer Journal, 2008

A series of multiblock poly(ether–ester)s based on poly(butylene succinate) (PBS) as the hard seg... more A series of multiblock poly(ether–ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether–ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2002

Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element p... more Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element polymer matrix. The spatial distribution and orientation of metallic flakes inside the matrix determines the covering efficiency of the paint, glossiness, and its angular-dependent properties such as lightness flop or color flop (two-tone). Such coatings are extensively used for a functional (i.e. security) as well as

Bioresource Technology, 2010

Different types of southern European hardwoods and softwoods were subjected to a liquefaction pro... more Different types of southern European hardwoods and softwoods were subjected to a liquefaction process with glycerol/diethylene glycol. The liquefied spruce wood was reacted in a condensation reaction in the hot press with different melamine–formaldehyde and melamine–urea–formaldehyde resin precursors and used as adhesives for wood particle boards. The mechanical properties of these particle boards and the determination of formaldehyde release, proved

Journal of Applied Polymer Science, 2006

Microwave radiation was used as the sole heating source to achieve liquefaction of Central Europe... more Microwave radiation was used as the sole heating source to achieve liquefaction of Central European hardwoods, with glycols and organic acid anhydrides, using phosphoric acid as the acid catalyst. Pulsed microwaves of 300 -700 W power were applied for 5-20 min. The efficiency of liquefaction increased with higher microwave power, longer radiation time, and higher phosphoric acid addition. With minor amounts of added acid it was possible to achieve complete liquefaction in 20 min. The method was tested for different hardwood types, with a series of glycols and anhydrides, and was found to be generally applicable.

Wood is one of the most abundant natural materials, and despite its complex composition it can be... more Wood is one of the most abundant natural materials, and despite its complex composition it can be used as a potential renewable feedstock for polymer production. One of the possible routes to achieving this is through liquefaction where wood or lignocellulosic materials reacts with multifunctional alcohols to yield low molecular mass, liquid products that can be used for polymer synthesis.

The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samp... more The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samples were prepared by variation of the bonding time and the temperature associated with the production of the powders. SEM micrographs show that only smaller flakes (<10 m) bond to the surface of the powder. The influence of bonding parameters on the microstructure of the cured coatings was studied using various optical methods. The colour differences measured in four perpendicular reflectance planes and the lightness flop were practically the same for all the coatings. The scattering of infrared light shows that longer bonding times give coatings in which the flakes are distributed more uniformly, parallel to the coating surface. The topmost layer of flakes was seen on SEM micrographs of selectively etched samples. The film forming process and reorientation of flakes were monitored on samples that were prepared at curing temperatures between 80 and 180 • C. It was observed that the flakes reorient from their initial position in the bonded powder to the final position in the effect coating almost completely during the formation of the continuous film. This process was accomplished at 100 • C.

Powder Technology, 2004

The quantitative method for the evaluation of the degree of pigment dispersion in powder coatings... more The quantitative method for the evaluation of the degree of pigment dispersion in powder coatings is described here. The quantitative information is obtained using selective oxygen plasma etching, scanning electron micrography and image analysis. This procedure was used in order to analyse the influences of the input power of the extrusion equipment on the pigment dispersion in powder coatings. The

Surface Coatings International Part B-coatings Transactions, 2002

Summaries The microstructure of a system of metal-effect coatings was studied with respect to th... more Summaries The microstructure of a system of metal-effect coatings was studied with respect to the types of metal falkes used, their dispersion and their orientation. Some indirect and some direct methods were applied on the same silver metallic acrylic coatings and blue metallic acrylic coatings, prepared with various amounts of different types of metallic flakes. Indirect methods were used to measure

Dyes and Pigments, 2003

Assessment of the state of a pigment dispersion in powder coatings is hindered by the lack of a s... more Assessment of the state of a pigment dispersion in powder coatings is hindered by the lack of a simple and effective method of evaluation, particularly during the production process. A method for evaluating dispersion quality in cured powder coatings or in samples taken immediately after the extrusion process is described in this paper. Quantitative information of pigment dispersion were obtained

Vacuum, 2005

Different polymers with various chemical and physical properties are used as a binder in pigmente... more Different polymers with various chemical and physical properties are used as a binder in pigmented coatings. The etching rate of these coatings with neutral oxygen plasma depends on the nature of the applied binder. To optimize the process, the chemical reaction of the oxygen plasma with the binder should be analyzed. The etching of a two-component polyester–polyisocyanate system was analyzed

Applied Physics A-materials Science & Processing, 2009

SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive ... more SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive chemical sensor, ready for integration with a generic double-metal CMOS technology. It was observed that the response of the sensor slowly increases with the temperature applied in hard-baking process as long as it remains below 300°C. At this temperature the response of the sensor abruptly

Thin Solid Films, 2004

The technology of selective plasma etching was applied in order to study particle distribution in... more The technology of selective plasma etching was applied in order to study particle distribution in powder coatings. Etching was performed in pure oxygen plasma. Plasma parameters were measured with a double Langmuir probe and a catalytic probe. At the neutral gas temperature of approximately 50 8C, the electron temperature was approximately 60 000 8C, the density of positive ions approximately 1=10 m , and the density of neutral oxygen atoms 2=10 m . In order to prevent sample overheating, 16 y3 2 1 y3 plasma was applied in time intervals of 20 s. The removal of the polymer matrix was accomplished within 2-4 min. After plasma treatment, the samples were analyzed with a scanning electron microscope. All the pigment and filler particles were left intact thus enabling the determination of the original distribution of the particles in the coating. ᮊ

Progress in Organic Coatings, 2005

The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samp... more The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samples were prepared by variation of the bonding time and the temperature associated with the production of the powders. SEM micrographs show that only smaller flakes (<10 m) bond to the surface of the powder. The influence of bonding parameters on the microstructure of the cured coatings was studied using various optical methods. The colour differences measured in four perpendicular reflectance planes and the lightness flop were practically the same for all the coatings. The scattering of infrared light shows that longer bonding times give coatings in which the flakes are distributed more uniformly, parallel to the coating surface. The topmost layer of flakes was seen on SEM micrographs of selectively etched samples. The film forming process and reorientation of flakes were monitored on samples that were prepared at curing temperatures between 80 and 180 • C. It was observed that the flakes reorient from their initial position in the bonded powder to the final position in the effect coating almost completely during the formation of the continuous film. This process was accomplished at 100 • C.

Surface Coatings International Part B: Coatings Transactions, 2003

Summaries The state of pigment dispersions in powder coatings was determined by applying scannin... more Summaries The state of pigment dispersions in powder coatings was determined by applying scanning electron microscopy (SEM) on coating surfaces that had been etched using an oxygen plasma. Image analysis with a modifed data interpretation was used to quantify the size distribution of the dispersed pigment particles. These methods were developed to determine the distribution of pigments throughout the cured powder

Progress in Organic Coatings, 2005

The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samp... more The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samples were prepared by variation of the bonding time and the temperature associated with the production of the powders. SEM micrographs show that only smaller flakes (<10 μm) bond to the surface of the powder. The influence of bonding parameters on the microstructure of the cured coatings was studied using various optical methods. The colour differences measured in four perpendicular reflectance planes and the lightness flop were practically the same for all the coatings. The scattering of infrared light shows that longer bonding times give coatings in which the flakes are distributed more uniformly, parallel to the coating surface. The topmost layer of flakes was seen on SEM micrographs of selectively etched samples. The film forming process and reorientation of flakes were monitored on samples that were prepared at curing temperatures between 80 and 180 °C. It was observed that the flakes reorient from their initial position in the bonded powder to the final position in the effect coating almost completely during the formation of the continuous film. This process was accomplished at 100 °C.

Dyes and Pigments, 2007

A study of gloss reduction of powder coatings was performed using different waxes, fillers and no... more A study of gloss reduction of powder coatings was performed using different waxes, fillers and non-compatible polymer resins (matting hardeners). Coatings with reduced surface smoothness were analysed. Scanning electron micrographs were taken to visualize the surfaces. All of the applied matting additives changed the surface profile of coating. The most interesting surface structural form is provided by wax particles. The average size of these forms was calculated by applying image analysis to some sample micrographs. The surface shape of all of the prepared coatings was analysed using surface profile measurements. Two parameters of these profiles were determined, the average roughness and the mean spacing between the surface peaks. The influence of several physical surface parameters on specular gloss characteristics is discussed.

Journal of Coatings Technology and Research, 2000

The influence of dispersing additives on the electrical conductivity of carbon black pigments dis... more The influence of dispersing additives on the electrical conductivity of carbon black pigments dispersed in an organic medium was studied. Two dispersing additives were examined in combination with two different carbon blacks, a conductive carbon black and a nonconductive one. These carbon blacks differ in the size of their aggregates and in the amounts of surface oxygen groups. Both of

Journal of Wood Chemistry and Technology, 2012

Beech (Fagus Sylvatica) milled-wood lignin was used as a model substrate in a study of lignin-cat... more Beech (Fagus Sylvatica) milled-wood lignin was used as a model substrate in a study of lignin-catalyzed liquefaction in the presence of p-toluene sulfonic acid monohydrate (PTSA) or sulphuric acid as the catalysts. The structural changes that lignin undergoes during the treatment were studied by NMR spectroscopy, FTIR, size-exclusion chromatography, and high-performance liquid chromatography. For the sulphuric acid-catalyzed liquefaction, it was

Bioresource Technology, 2000

In our research, we have utilized high energy ultrasound for the liquefaction of different lignoc... more In our research, we have utilized high energy ultrasound for the liquefaction of different lignocellulosic materials, wood wastes in particular. We developed a highly efficient way of transforming this biomass waste into valuable chemicals. It was found, that the reaction yield in all experiments was high and that the reaction times were shortened up to nine times when using the

Catalysis Today, 2010

A blend of spruce (Picea spp.) and fir (Abies spp.) sawdust was liquefied by an optimized techniq... more A blend of spruce (Picea spp.) and fir (Abies spp.) sawdust was liquefied by an optimized technique in the presence of multifunctional alcohols and p-toluene sulfonic acid monohydrate as a catalyst. The lignin behaviour during wood liquefaction was studied at different reaction times. Samples prepared by the new separation procedure were characterized by quantitative 31P, 13C NMR and by size-exclusion

European Polymer Journal, 2008

A series of multiblock poly(ether–ester)s based on poly(butylene succinate) (PBS) as the hard seg... more A series of multiblock poly(ether–ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether–ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2002

Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element p... more Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element polymer matrix. The spatial distribution and orientation of metallic flakes inside the matrix determines the covering efficiency of the paint, glossiness, and its angular-dependent properties such as lightness flop or color flop (two-tone). Such coatings are extensively used for a functional (i.e. security) as well as

Bioresource Technology, 2010

Different types of southern European hardwoods and softwoods were subjected to a liquefaction pro... more Different types of southern European hardwoods and softwoods were subjected to a liquefaction process with glycerol/diethylene glycol. The liquefied spruce wood was reacted in a condensation reaction in the hot press with different melamine–formaldehyde and melamine–urea–formaldehyde resin precursors and used as adhesives for wood particle boards. The mechanical properties of these particle boards and the determination of formaldehyde release, proved

Journal of Applied Polymer Science, 2006

Microwave radiation was used as the sole heating source to achieve liquefaction of Central Europe... more Microwave radiation was used as the sole heating source to achieve liquefaction of Central European hardwoods, with glycols and organic acid anhydrides, using phosphoric acid as the acid catalyst. Pulsed microwaves of 300 -700 W power were applied for 5-20 min. The efficiency of liquefaction increased with higher microwave power, longer radiation time, and higher phosphoric acid addition. With minor amounts of added acid it was possible to achieve complete liquefaction in 20 min. The method was tested for different hardwood types, with a series of glycols and anhydrides, and was found to be generally applicable.

Wood is one of the most abundant natural materials, and despite its complex composition it can be... more Wood is one of the most abundant natural materials, and despite its complex composition it can be used as a potential renewable feedstock for polymer production. One of the possible routes to achieving this is through liquefaction where wood or lignocellulosic materials reacts with multifunctional alcohols to yield low molecular mass, liquid products that can be used for polymer synthesis.

The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samp... more The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samples were prepared by variation of the bonding time and the temperature associated with the production of the powders. SEM micrographs show that only smaller flakes (<10 m) bond to the surface of the powder. The influence of bonding parameters on the microstructure of the cured coatings was studied using various optical methods. The colour differences measured in four perpendicular reflectance planes and the lightness flop were practically the same for all the coatings. The scattering of infrared light shows that longer bonding times give coatings in which the flakes are distributed more uniformly, parallel to the coating surface. The topmost layer of flakes was seen on SEM micrographs of selectively etched samples. The film forming process and reorientation of flakes were monitored on samples that were prepared at curing temperatures between 80 and 180 • C. It was observed that the flakes reorient from their initial position in the bonded powder to the final position in the effect coating almost completely during the formation of the continuous film. This process was accomplished at 100 • C.

Powder Technology, 2004

The quantitative method for the evaluation of the degree of pigment dispersion in powder coatings... more The quantitative method for the evaluation of the degree of pigment dispersion in powder coatings is described here. The quantitative information is obtained using selective oxygen plasma etching, scanning electron micrography and image analysis. This procedure was used in order to analyse the influences of the input power of the extrusion equipment on the pigment dispersion in powder coatings. The

Surface Coatings International Part B-coatings Transactions, 2002

Summaries The microstructure of a system of metal-effect coatings was studied with respect to th... more Summaries The microstructure of a system of metal-effect coatings was studied with respect to the types of metal falkes used, their dispersion and their orientation. Some indirect and some direct methods were applied on the same silver metallic acrylic coatings and blue metallic acrylic coatings, prepared with various amounts of different types of metallic flakes. Indirect methods were used to measure

Dyes and Pigments, 2003

Assessment of the state of a pigment dispersion in powder coatings is hindered by the lack of a s... more Assessment of the state of a pigment dispersion in powder coatings is hindered by the lack of a simple and effective method of evaluation, particularly during the production process. A method for evaluating dispersion quality in cured powder coatings or in samples taken immediately after the extrusion process is described in this paper. Quantitative information of pigment dispersion were obtained

Vacuum, 2005

Different polymers with various chemical and physical properties are used as a binder in pigmente... more Different polymers with various chemical and physical properties are used as a binder in pigmented coatings. The etching rate of these coatings with neutral oxygen plasma depends on the nature of the applied binder. To optimize the process, the chemical reaction of the oxygen plasma with the binder should be analyzed. The etching of a two-component polyester–polyisocyanate system was analyzed

Applied Physics A-materials Science & Processing, 2009

SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive ... more SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive chemical sensor, ready for integration with a generic double-metal CMOS technology. It was observed that the response of the sensor slowly increases with the temperature applied in hard-baking process as long as it remains below 300°C. At this temperature the response of the sensor abruptly

Thin Solid Films, 2004

The technology of selective plasma etching was applied in order to study particle distribution in... more The technology of selective plasma etching was applied in order to study particle distribution in powder coatings. Etching was performed in pure oxygen plasma. Plasma parameters were measured with a double Langmuir probe and a catalytic probe. At the neutral gas temperature of approximately 50 8C, the electron temperature was approximately 60 000 8C, the density of positive ions approximately 1=10 m , and the density of neutral oxygen atoms 2=10 m . In order to prevent sample overheating, 16 y3 2 1 y3 plasma was applied in time intervals of 20 s. The removal of the polymer matrix was accomplished within 2-4 min. After plasma treatment, the samples were analyzed with a scanning electron microscope. All the pigment and filler particles were left intact thus enabling the determination of the original distribution of the particles in the coating. ᮊ

Progress in Organic Coatings, 2005

The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samp... more The orientation of aluminium flakes in powder coatings has been studied. Three effect powder samples were prepared by variation of the bonding time and the temperature associated with the production of the powders. SEM micrographs show that only smaller flakes (<10 m) bond to the surface of the powder. The influence of bonding parameters on the microstructure of the cured coatings was studied using various optical methods. The colour differences measured in four perpendicular reflectance planes and the lightness flop were practically the same for all the coatings. The scattering of infrared light shows that longer bonding times give coatings in which the flakes are distributed more uniformly, parallel to the coating surface. The topmost layer of flakes was seen on SEM micrographs of selectively etched samples. The film forming process and reorientation of flakes were monitored on samples that were prepared at curing temperatures between 80 and 180 • C. It was observed that the flakes reorient from their initial position in the bonded powder to the final position in the effect coating almost completely during the formation of the continuous film. This process was accomplished at 100 • C.

Surface Coatings International Part B: Coatings Transactions, 2003

Summaries The state of pigment dispersions in powder coatings was determined by applying scannin... more Summaries The state of pigment dispersions in powder coatings was determined by applying scanning electron microscopy (SEM) on coating surfaces that had been etched using an oxygen plasma. Image analysis with a modifed data interpretation was used to quantify the size distribution of the dispersed pigment particles. These methods were developed to determine the distribution of pigments throughout the cured powder