MJ Walzak | University of Western Ontario (original) (raw)
Papers by MJ Walzak
Surface and Interface Analysis, 2011
, a gut bacterial metabolic end product and common food preservative, which produces reversible b... more , a gut bacterial metabolic end product and common food preservative, which produces reversible behavioral and electrographic effects coupled with increased oxidative stress and innate neuroinflammatory changes consistent with findings in ASD patients. PPA appears to be a potential environmental trigger linking the disparate behavioral, dietary, gut, metabolic and immune factors implicated in ASD. These previous studies used traditional immunohistochemical and biochemical techniques to examine increased oxidative stress and visualize neurons, reactive astrocytes, and activated microglia in hippocampus and adjacent external capsule white matter from coronally sectioned rat brain. As PPA is also an important metabolic intermediate of fatty acid beta oxidation, we have repeated the experiments with deuterium-tagged PPA (DPPA) and employed ToF-SIMS to trace the deuterium decoration of comparable brain regions ipsilateral to the DPPA infusion. In the present case of revealing DPPA-induced changes in brain regions, ToF-SIMS imaging of deuterium confirms the effectiveness of the methodology and the imaging results support the PPA-triggered ASD rodent model.
Langmuir : the ACS journal of surfaces and colloids, Jan 29, 2005
As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA... more As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA) on a muscovite mica substrate were found to be mechanically robust and to serve as a lubricant to protect the underlying mica substrate. For comparison purposes, three polymer films were subjected to scratch tests under the same conditions. The scratch tests were conducted using a diamond-tipped stylus, and the resultant scratches were examined using atomic force microscopy. The excellent mechanical strength of OPA SAMs is supported by analysis with time-of-flight secondary ion mass spectrometry, which suggests that the headgroup of the OPA is strongly bonded to the substrate atoms. The molecular lubrication provided by OPA SAMs suggests that the interaction between the headgroup and the substrate is sufficiently strong to endure significant shear force and that the hydrocarbon chains are able to dissipate shear energy.
Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distr... more Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distributions of fatty amines, alcohols and esters spin coated onto gold surfaces and commercial aluminium-magnesium (Al-Mg) alloy surfaces, cleaned using UV-ozone. The aim of this study is to develop an understanding of the interactions of model lubricants with metal surfaces, such as gold and aluminium. This static SIMS study of organic thin films has been able to identify specific reaction products on the aluminium surface for each functional group. This work demonstrates that organic molecules with alcohol, ester and amine functional groups undergo specific chemical reactions with oxidized Al-Mg alloy surfaces. For example, films composed of the fatty alcohol dodecanol were observed to emit monomers, dimers and trimers with discrete distributions. In addition, negative secondary ion mass spectra indicate that a surface carboxylate is formed from the alcohol. The formation of carboxylate reaction products was confirmed by Fourier transform infrared spectroscopy. On Al-Mg alloy surfaces, a direct interaction with the amine and aluminium oxide surface is observed by the detection of a molecular ion that corresponds to the mass of dodecylamine and AlO − , characteristic of aluminium oxide. Ethyl laurate was shown to eliminate the ethyl group, leaving the laurate anion. This study demonstrates the ability of time-of-flight (ToF) SIMS to discriminate and detect chemical reaction products formed between model lubricant molecules and metal surfaces. As a result of this study, the use of ToF-SIMS to identify reaction products of model lubricants can be extended to provide a better understanding of the interactions of lubricants and metal surfaces at high temperatures and pressures that more closely resemble the conditions encountered in industrial rolling processes.
Journal of Physical Chemistry C, 2007
Thin and thick cubic boron nitride (cBN) films were grown on nanodiamond (nanoD), using radio-fre... more Thin and thick cubic boron nitride (cBN) films were grown on nanodiamond (nanoD), using radio-frequency magnetron sputtering and plasma-enhanced chemical vapor deposition. The chemical composition of the cBN surface layer was nearly stoichiometric, which yielded an essentially pure cubic phase. The root-mean-square roughness of the nanoD and cBN films varied from 4 to 37.5 nm, depending on the pretreatment, method of deposition, and film thickness. The surface free energy of the cBN films with respect to the nanoD was determined by the contact angle measurements. The surface free energy was affected by surface roughness, but the surface energy of nanodiamond was always slightly higher than that of cBN films. This relationship between the surface free energies has important implications for material compatibility and possible local heteroepitaxial growth of cBN on nanoD.
Surface and Interface Analysis, 2005
Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distr... more Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distributions of fatty amines, alcohols and esters spin coated onto gold surfaces and commercial aluminium-magnesium (Al-Mg) alloy surfaces, cleaned using UV-ozone. The aim of this study is to develop an understanding of the interactions of model lubricants with metal surfaces, such as gold and aluminium. This static SIMS study of organic thin films has been able to identify specific reaction products on the aluminium surface for each functional group. This work demonstrates that organic molecules with alcohol, ester and amine functional groups undergo specific chemical reactions with oxidized Al-Mg alloy surfaces. For example, films composed of the fatty alcohol dodecanol were observed to emit monomers, dimers and trimers with discrete distributions. In addition, negative secondary ion mass spectra indicate that a surface carboxylate is formed from the alcohol. The formation of carboxylate reaction products was confirmed by Fourier transform infrared spectroscopy. On Al-Mg alloy surfaces, a direct interaction with the amine and aluminium oxide surface is observed by the detection of a molecular ion that corresponds to the mass of dodecylamine and AlO − , characteristic of aluminium oxide. Ethyl laurate was shown to eliminate the ethyl group, leaving the laurate anion. This study demonstrates the ability of time-of-flight (ToF) SIMS to discriminate and detect chemical reaction products formed between model lubricant molecules and metal surfaces. As a result of this study, the use of ToF-SIMS to identify reaction products of model lubricants can be extended to provide a better understanding of the interactions of lubricants and metal surfaces at high temperatures and pressures that more closely resemble the conditions encountered in industrial rolling processes.
Surface and Interface Analysis, 2003
Static secondary ion mass spectrometry was used to study the surface reactions and lateral distri... more Static secondary ion mass spectrometry was used to study the surface reactions and lateral distributions of fatty carboxylic acid molecules on sputter-deposited gold and aluminium surfaces, as well as commercial aluminium-magnesium alloy surfaces, cleaned using UV/ozone. Films were prepared by spin coating dilute solutions of stearic acid and lauric acid onto the above surfaces. These carboxylic acids were shown to react with the oxide formed on the aluminium and aluminum-magnesium alloy substrates to produce a deprotonated acid anion, stabilized by the formation of a magnesium soap on the aluminium-magnesium alloy surface. Secondary ion imaging of stearic acid films revealed the formation of C-type crystals.
Surface and Interface Analysis, 2011
, a gut bacterial metabolic end product and common food preservative, which produces reversible b... more , a gut bacterial metabolic end product and common food preservative, which produces reversible behavioral and electrographic effects coupled with increased oxidative stress and innate neuroinflammatory changes consistent with findings in ASD patients. PPA appears to be a potential environmental trigger linking the disparate behavioral, dietary, gut, metabolic and immune factors implicated in ASD. These previous studies used traditional immunohistochemical and biochemical techniques to examine increased oxidative stress and visualize neurons, reactive astrocytes, and activated microglia in hippocampus and adjacent external capsule white matter from coronally sectioned rat brain. As PPA is also an important metabolic intermediate of fatty acid beta oxidation, we have repeated the experiments with deuterium-tagged PPA (DPPA) and employed ToF-SIMS to trace the deuterium decoration of comparable brain regions ipsilateral to the DPPA infusion. In the present case of revealing DPPA-induced changes in brain regions, ToF-SIMS imaging of deuterium confirms the effectiveness of the methodology and the imaging results support the PPA-triggered ASD rodent model.
Review of Scientific Instruments, 2002
Langmuir, 1999
Localized shear deformation of biaxially oriented polypropylene (PP) film using a stylus force of... more Localized shear deformation of biaxially oriented polypropylene (PP) film using a stylus force of 0.4 mN results in a reorientation of polymer strands in the shear-force direction, which appears as a striped region. This change in surface structure, which was observed by atomic force microscopy (AFM), resulted in an increase in the adhesion force as determined from the interaction between the AFM tip and the sample surface. This increase in adhesion force results from an increase in surface energy, which is thought to be caused by an increase in density and closer ordering of the polymer strands on the film surface. We demonstrate that the surface energy of PP film can be increased either by this mechanical scratching on the surface or by adding oxidation-induced chemical functional groups to the surface. The increase in surface energy from mechanical scratching of the PP surface is comparable to that introduced by surface oxidation of the unscratched PP surface after 1-min UV/ozone exposure.
Langmuir, 2005
As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA... more As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA) on a muscovite mica substrate were found to be mechanically robust and to serve as a lubricant to protect the underlying mica substrate. For comparison purposes, three polymer films were subjected to scratch tests under the same conditions. The scratch tests were conducted using a diamond-tipped stylus, and the resultant scratches were examined using atomic force microscopy. The excellent mechanical strength of OPA SAMs is supported by analysis with time-of-flight secondary ion mass spectrometry, which suggests that the headgroup of the OPA is strongly bonded to the substrate atoms. The molecular lubrication provided by OPA SAMs suggests that the interaction between the headgroup and the substrate is sufficiently strong to endure significant shear force and that the hydrocarbon chains are able to dissipate shear energy.
Journal of Polymer Science Part A: Polymer Chemistry, 1999
Chemical reactions of the surface of a polypropylene (PP) film in the presence of various combina... more Chemical reactions of the surface of a polypropylene (PP) film in the presence of various combinations of ultraviolet light and ozone gas (UVO) conditions were studied. Exposure of the polymer surface was carried out in a laboratory-scale UVO reactor in which the following parameters could be varied: ozone concentration, wavelength of ultraviolet (UV) radiation, pulsed operation of the UV lamps, the treatment distance between the PP film and the lamps, and water vapor concentration. Advancing and receding contact angle measurements were used to monitor surface energy changes imparted by the treatment. Two spectroscopic techniques, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), were used to monitor changes in the polymer surface chemistry. Oxidation of the PP surface is proposed to occur through two alternate mechanisms: (1) insertion of an O ( 1 D) atom to form ether linkages, or (2) hydrogen abstraction by O ( 3 P), followed either by crosslinking or by reaction with oxygen species to form carbonyl and/or carboxyl functional groups. It was found that reaction 1 dominates initially, but that its rate is reduced by the formation of products from reaction 2. It appears that the ether functional groups produced by reaction 1 are responsible primarily for increased surface energy. Carbonyl, carboxyl, and hydroxyl groups formed in reaction 2 appear to have little additional effect on surface energy; it is proposed that these groups are involved strongly in intramolecular hydrogen bonding, thereby decreasing their availability to contribute to increased surface energy. High-energy UV radiation was found to play only a minor role in the surface modification of PP. Of the narrow range of ozone concentrations studied, no clear relationship was found to exist between ozone concentration and rate of modification of the surface; thus, the concentration of ozone must not affect the relative concentrations of products from the competing reactions. Increased surface oxidation and decreased contact angles were observed when the lamp-to-sample distance was minimized. The presence of water vapor during UVO treatment was found to lead to greater oxygen uptake after short-term treatments but did not result in increased surface energy.
Journal of Materials Engineering and Performance, 1998
ABSTRACT Coatings are applied to surfaces for a variety of reasons: to enhance their appearance, ... more ABSTRACT Coatings are applied to surfaces for a variety of reasons: to enhance their appearance, to protect the substrate, to augment the adhesion to other layers, or to functionalize them for further reactions. To evaluate the efficacy of the coating, it is often necessary to analyze the substrate and the coating to ensure that the needed characteristics are present. To this end, the use of x-ray photoelectron spectroscopy (XPS), contact angle, and atomic force microscopy (AFM) can provide information about the surface composition, its morphology, and its ability to be wetted with various solvents. Scanning electron microscopy with energy dispersive x-ray analysis (SEM/EDX) and Fourier transform infrared spectroscopy (FTIR) can provide a clear picture of the near surface components as well as the continuity of coatings. All of these aspects are valuable in evaluating a coating and essential when problems are encountered. The application of these techniques to the analysis of coatings is discussed.
Journal of Materials Engineering and Performance, 2004
Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space mo... more Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.
Journal of Adhesion Science and Technology, 2003
... MARÍA D. ROMERO-SÁNCHEZ1, M. MERCEDES PASTOR-BLAS1, JOSÉ MIGUEL MARTÍN-MARTÍNEZ1; and MJ WAL... more ... MARÍA D. ROMERO-SÁNCHEZ1, M. MERCEDES PASTOR-BLAS1, JOSÉ MIGUEL MARTÍN-MARTÍNEZ1; and MJ WALZAK2 1 Adhesion and Adhesives Laboratory, Department of Inorganic Chemistry, University of Alicante, 03080 Alicante, Spain 2 Surface Science Western ...
International Journal of Adhesion and Adhesives, 2007
Two styrenebutadienestyrene block rubbers, one with 10wt% calcium carbonate filler (S6C), and o... more Two styrenebutadienestyrene block rubbers, one with 10wt% calcium carbonate filler (S6C), and one without (S6) were surface treated with UV radiation. The resulting surface modifications and adhesion properties with polyurethane adhesive were studied. The ...
International Journal of Adhesion and Adhesives, 2005
The effect of exposure to different ozone concentrations, in conjunction with UV radiation, on th... more The effect of exposure to different ozone concentrations, in conjunction with UV radiation, on the surface modification and adhesion properties of a block synthetic styrene-butadiene-styrene (S6) rubber was studied. The treatment time varied between 10 s and 30 min. Three different surface treatments were investigated: ozone only (O 3 ), UV radiation in the presence of air, and UV radiation in the presence of externally generated, supplemental ozone (UV/O 3 ). The surface modified S6 rubber was characterized using contact angle measurements (ethylene glycol, 25 1C), Fourier transform infrared spectroscopy using an attenuated total reflection attachment (ATR-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). T-peel tests of surface modified S6 rubber/polyurethane (PU) adhesive/leather joints were carried out to quantify the changes in the adhesion properties.
Applied Surface Science, 1999
It is well known that topographic features can give rise to edge effects when making lateral forc... more It is well known that topographic features can give rise to edge effects when making lateral force measurements in Ž . contact mode atomic force microscopy AFM . Using a 'smooth' polypropylene film, which was also imaged by non-contact mode AFM, we showed that the edge effect can be used to reveal topographic features clearly through an enhancement of their outlines. Using photo-cured polymers we demonstrated that lateral force imaging is especially useful in revealing topographic features on surfaces which have large height differences. q
Surface and Interface Analysis, 2011
, a gut bacterial metabolic end product and common food preservative, which produces reversible b... more , a gut bacterial metabolic end product and common food preservative, which produces reversible behavioral and electrographic effects coupled with increased oxidative stress and innate neuroinflammatory changes consistent with findings in ASD patients. PPA appears to be a potential environmental trigger linking the disparate behavioral, dietary, gut, metabolic and immune factors implicated in ASD. These previous studies used traditional immunohistochemical and biochemical techniques to examine increased oxidative stress and visualize neurons, reactive astrocytes, and activated microglia in hippocampus and adjacent external capsule white matter from coronally sectioned rat brain. As PPA is also an important metabolic intermediate of fatty acid beta oxidation, we have repeated the experiments with deuterium-tagged PPA (DPPA) and employed ToF-SIMS to trace the deuterium decoration of comparable brain regions ipsilateral to the DPPA infusion. In the present case of revealing DPPA-induced changes in brain regions, ToF-SIMS imaging of deuterium confirms the effectiveness of the methodology and the imaging results support the PPA-triggered ASD rodent model.
Langmuir : the ACS journal of surfaces and colloids, Jan 29, 2005
As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA... more As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA) on a muscovite mica substrate were found to be mechanically robust and to serve as a lubricant to protect the underlying mica substrate. For comparison purposes, three polymer films were subjected to scratch tests under the same conditions. The scratch tests were conducted using a diamond-tipped stylus, and the resultant scratches were examined using atomic force microscopy. The excellent mechanical strength of OPA SAMs is supported by analysis with time-of-flight secondary ion mass spectrometry, which suggests that the headgroup of the OPA is strongly bonded to the substrate atoms. The molecular lubrication provided by OPA SAMs suggests that the interaction between the headgroup and the substrate is sufficiently strong to endure significant shear force and that the hydrocarbon chains are able to dissipate shear energy.
Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distr... more Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distributions of fatty amines, alcohols and esters spin coated onto gold surfaces and commercial aluminium-magnesium (Al-Mg) alloy surfaces, cleaned using UV-ozone. The aim of this study is to develop an understanding of the interactions of model lubricants with metal surfaces, such as gold and aluminium. This static SIMS study of organic thin films has been able to identify specific reaction products on the aluminium surface for each functional group. This work demonstrates that organic molecules with alcohol, ester and amine functional groups undergo specific chemical reactions with oxidized Al-Mg alloy surfaces. For example, films composed of the fatty alcohol dodecanol were observed to emit monomers, dimers and trimers with discrete distributions. In addition, negative secondary ion mass spectra indicate that a surface carboxylate is formed from the alcohol. The formation of carboxylate reaction products was confirmed by Fourier transform infrared spectroscopy. On Al-Mg alloy surfaces, a direct interaction with the amine and aluminium oxide surface is observed by the detection of a molecular ion that corresponds to the mass of dodecylamine and AlO − , characteristic of aluminium oxide. Ethyl laurate was shown to eliminate the ethyl group, leaving the laurate anion. This study demonstrates the ability of time-of-flight (ToF) SIMS to discriminate and detect chemical reaction products formed between model lubricant molecules and metal surfaces. As a result of this study, the use of ToF-SIMS to identify reaction products of model lubricants can be extended to provide a better understanding of the interactions of lubricants and metal surfaces at high temperatures and pressures that more closely resemble the conditions encountered in industrial rolling processes.
Journal of Physical Chemistry C, 2007
Thin and thick cubic boron nitride (cBN) films were grown on nanodiamond (nanoD), using radio-fre... more Thin and thick cubic boron nitride (cBN) films were grown on nanodiamond (nanoD), using radio-frequency magnetron sputtering and plasma-enhanced chemical vapor deposition. The chemical composition of the cBN surface layer was nearly stoichiometric, which yielded an essentially pure cubic phase. The root-mean-square roughness of the nanoD and cBN films varied from 4 to 37.5 nm, depending on the pretreatment, method of deposition, and film thickness. The surface free energy of the cBN films with respect to the nanoD was determined by the contact angle measurements. The surface free energy was affected by surface roughness, but the surface energy of nanodiamond was always slightly higher than that of cBN films. This relationship between the surface free energies has important implications for material compatibility and possible local heteroepitaxial growth of cBN on nanoD.
Surface and Interface Analysis, 2005
Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distr... more Static secondary ion mass spectrometry was used to study the chemical reactions and lateral distributions of fatty amines, alcohols and esters spin coated onto gold surfaces and commercial aluminium-magnesium (Al-Mg) alloy surfaces, cleaned using UV-ozone. The aim of this study is to develop an understanding of the interactions of model lubricants with metal surfaces, such as gold and aluminium. This static SIMS study of organic thin films has been able to identify specific reaction products on the aluminium surface for each functional group. This work demonstrates that organic molecules with alcohol, ester and amine functional groups undergo specific chemical reactions with oxidized Al-Mg alloy surfaces. For example, films composed of the fatty alcohol dodecanol were observed to emit monomers, dimers and trimers with discrete distributions. In addition, negative secondary ion mass spectra indicate that a surface carboxylate is formed from the alcohol. The formation of carboxylate reaction products was confirmed by Fourier transform infrared spectroscopy. On Al-Mg alloy surfaces, a direct interaction with the amine and aluminium oxide surface is observed by the detection of a molecular ion that corresponds to the mass of dodecylamine and AlO − , characteristic of aluminium oxide. Ethyl laurate was shown to eliminate the ethyl group, leaving the laurate anion. This study demonstrates the ability of time-of-flight (ToF) SIMS to discriminate and detect chemical reaction products formed between model lubricant molecules and metal surfaces. As a result of this study, the use of ToF-SIMS to identify reaction products of model lubricants can be extended to provide a better understanding of the interactions of lubricants and metal surfaces at high temperatures and pressures that more closely resemble the conditions encountered in industrial rolling processes.
Surface and Interface Analysis, 2003
Static secondary ion mass spectrometry was used to study the surface reactions and lateral distri... more Static secondary ion mass spectrometry was used to study the surface reactions and lateral distributions of fatty carboxylic acid molecules on sputter-deposited gold and aluminium surfaces, as well as commercial aluminium-magnesium alloy surfaces, cleaned using UV/ozone. Films were prepared by spin coating dilute solutions of stearic acid and lauric acid onto the above surfaces. These carboxylic acids were shown to react with the oxide formed on the aluminium and aluminum-magnesium alloy substrates to produce a deprotonated acid anion, stabilized by the formation of a magnesium soap on the aluminium-magnesium alloy surface. Secondary ion imaging of stearic acid films revealed the formation of C-type crystals.
Surface and Interface Analysis, 2011
, a gut bacterial metabolic end product and common food preservative, which produces reversible b... more , a gut bacterial metabolic end product and common food preservative, which produces reversible behavioral and electrographic effects coupled with increased oxidative stress and innate neuroinflammatory changes consistent with findings in ASD patients. PPA appears to be a potential environmental trigger linking the disparate behavioral, dietary, gut, metabolic and immune factors implicated in ASD. These previous studies used traditional immunohistochemical and biochemical techniques to examine increased oxidative stress and visualize neurons, reactive astrocytes, and activated microglia in hippocampus and adjacent external capsule white matter from coronally sectioned rat brain. As PPA is also an important metabolic intermediate of fatty acid beta oxidation, we have repeated the experiments with deuterium-tagged PPA (DPPA) and employed ToF-SIMS to trace the deuterium decoration of comparable brain regions ipsilateral to the DPPA infusion. In the present case of revealing DPPA-induced changes in brain regions, ToF-SIMS imaging of deuterium confirms the effectiveness of the methodology and the imaging results support the PPA-triggered ASD rodent model.
Review of Scientific Instruments, 2002
Langmuir, 1999
Localized shear deformation of biaxially oriented polypropylene (PP) film using a stylus force of... more Localized shear deformation of biaxially oriented polypropylene (PP) film using a stylus force of 0.4 mN results in a reorientation of polymer strands in the shear-force direction, which appears as a striped region. This change in surface structure, which was observed by atomic force microscopy (AFM), resulted in an increase in the adhesion force as determined from the interaction between the AFM tip and the sample surface. This increase in adhesion force results from an increase in surface energy, which is thought to be caused by an increase in density and closer ordering of the polymer strands on the film surface. We demonstrate that the surface energy of PP film can be increased either by this mechanical scratching on the surface or by adding oxidation-induced chemical functional groups to the surface. The increase in surface energy from mechanical scratching of the PP surface is comparable to that introduced by surface oxidation of the unscratched PP surface after 1-min UV/ozone exposure.
Langmuir, 2005
As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA... more As determined by scratch tests, self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA) on a muscovite mica substrate were found to be mechanically robust and to serve as a lubricant to protect the underlying mica substrate. For comparison purposes, three polymer films were subjected to scratch tests under the same conditions. The scratch tests were conducted using a diamond-tipped stylus, and the resultant scratches were examined using atomic force microscopy. The excellent mechanical strength of OPA SAMs is supported by analysis with time-of-flight secondary ion mass spectrometry, which suggests that the headgroup of the OPA is strongly bonded to the substrate atoms. The molecular lubrication provided by OPA SAMs suggests that the interaction between the headgroup and the substrate is sufficiently strong to endure significant shear force and that the hydrocarbon chains are able to dissipate shear energy.
Journal of Polymer Science Part A: Polymer Chemistry, 1999
Chemical reactions of the surface of a polypropylene (PP) film in the presence of various combina... more Chemical reactions of the surface of a polypropylene (PP) film in the presence of various combinations of ultraviolet light and ozone gas (UVO) conditions were studied. Exposure of the polymer surface was carried out in a laboratory-scale UVO reactor in which the following parameters could be varied: ozone concentration, wavelength of ultraviolet (UV) radiation, pulsed operation of the UV lamps, the treatment distance between the PP film and the lamps, and water vapor concentration. Advancing and receding contact angle measurements were used to monitor surface energy changes imparted by the treatment. Two spectroscopic techniques, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), were used to monitor changes in the polymer surface chemistry. Oxidation of the PP surface is proposed to occur through two alternate mechanisms: (1) insertion of an O ( 1 D) atom to form ether linkages, or (2) hydrogen abstraction by O ( 3 P), followed either by crosslinking or by reaction with oxygen species to form carbonyl and/or carboxyl functional groups. It was found that reaction 1 dominates initially, but that its rate is reduced by the formation of products from reaction 2. It appears that the ether functional groups produced by reaction 1 are responsible primarily for increased surface energy. Carbonyl, carboxyl, and hydroxyl groups formed in reaction 2 appear to have little additional effect on surface energy; it is proposed that these groups are involved strongly in intramolecular hydrogen bonding, thereby decreasing their availability to contribute to increased surface energy. High-energy UV radiation was found to play only a minor role in the surface modification of PP. Of the narrow range of ozone concentrations studied, no clear relationship was found to exist between ozone concentration and rate of modification of the surface; thus, the concentration of ozone must not affect the relative concentrations of products from the competing reactions. Increased surface oxidation and decreased contact angles were observed when the lamp-to-sample distance was minimized. The presence of water vapor during UVO treatment was found to lead to greater oxygen uptake after short-term treatments but did not result in increased surface energy.
Journal of Materials Engineering and Performance, 1998
ABSTRACT Coatings are applied to surfaces for a variety of reasons: to enhance their appearance, ... more ABSTRACT Coatings are applied to surfaces for a variety of reasons: to enhance their appearance, to protect the substrate, to augment the adhesion to other layers, or to functionalize them for further reactions. To evaluate the efficacy of the coating, it is often necessary to analyze the substrate and the coating to ensure that the needed characteristics are present. To this end, the use of x-ray photoelectron spectroscopy (XPS), contact angle, and atomic force microscopy (AFM) can provide information about the surface composition, its morphology, and its ability to be wetted with various solvents. Scanning electron microscopy with energy dispersive x-ray analysis (SEM/EDX) and Fourier transform infrared spectroscopy (FTIR) can provide a clear picture of the near surface components as well as the continuity of coatings. All of these aspects are valuable in evaluating a coating and essential when problems are encountered. The application of these techniques to the analysis of coatings is discussed.
Journal of Materials Engineering and Performance, 2004
Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space mo... more Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.
Journal of Adhesion Science and Technology, 2003
... MARÍA D. ROMERO-SÁNCHEZ1, M. MERCEDES PASTOR-BLAS1, JOSÉ MIGUEL MARTÍN-MARTÍNEZ1; and MJ WAL... more ... MARÍA D. ROMERO-SÁNCHEZ1, M. MERCEDES PASTOR-BLAS1, JOSÉ MIGUEL MARTÍN-MARTÍNEZ1; and MJ WALZAK2 1 Adhesion and Adhesives Laboratory, Department of Inorganic Chemistry, University of Alicante, 03080 Alicante, Spain 2 Surface Science Western ...
International Journal of Adhesion and Adhesives, 2007
Two styrenebutadienestyrene block rubbers, one with 10wt% calcium carbonate filler (S6C), and o... more Two styrenebutadienestyrene block rubbers, one with 10wt% calcium carbonate filler (S6C), and one without (S6) were surface treated with UV radiation. The resulting surface modifications and adhesion properties with polyurethane adhesive were studied. The ...
International Journal of Adhesion and Adhesives, 2005
The effect of exposure to different ozone concentrations, in conjunction with UV radiation, on th... more The effect of exposure to different ozone concentrations, in conjunction with UV radiation, on the surface modification and adhesion properties of a block synthetic styrene-butadiene-styrene (S6) rubber was studied. The treatment time varied between 10 s and 30 min. Three different surface treatments were investigated: ozone only (O 3 ), UV radiation in the presence of air, and UV radiation in the presence of externally generated, supplemental ozone (UV/O 3 ). The surface modified S6 rubber was characterized using contact angle measurements (ethylene glycol, 25 1C), Fourier transform infrared spectroscopy using an attenuated total reflection attachment (ATR-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). T-peel tests of surface modified S6 rubber/polyurethane (PU) adhesive/leather joints were carried out to quantify the changes in the adhesion properties.
Applied Surface Science, 1999
It is well known that topographic features can give rise to edge effects when making lateral forc... more It is well known that topographic features can give rise to edge effects when making lateral force measurements in Ž . contact mode atomic force microscopy AFM . Using a 'smooth' polypropylene film, which was also imaged by non-contact mode AFM, we showed that the edge effect can be used to reveal topographic features clearly through an enhancement of their outlines. Using photo-cured polymers we demonstrated that lateral force imaging is especially useful in revealing topographic features on surfaces which have large height differences. q