Aljaž Vilčnik | Private - Academia.edu (original) (raw)

Papers by Aljaž Vilčnik

Research paper thumbnail of Hydrophobic properties and water-vapour transmission of surface treated and non-treated wood, modified with TiO2

Research paper thumbnail of Vpliv vsebnosti vode v smrekovem lesu na kakovost hidrotermalne depozicije TiO2 na površini lesnih vzorcev

Research paper thumbnail of Functionalisation of cotton with hydrophobic urea/polydimethylsiloxane sol-gel hybrid

Acta Chimica Slovenica

A novel organic-inorganic sol-gel hybrid precursor, di-ureapropyltriethoxysilyl [bis aminopropyl)... more A novel organic-inorganic sol-gel hybrid precursor, di-ureapropyltriethoxysilyl [bis aminopropyl)terminated-polydimethylsiloxane (1000)| (PDMSU), was synthesized and tested as a hydrophobic impregnation for cotton fabrics. Hydrolysis of the precursor was performed with 0.1 mol L -1 HCl and for deposition 4% sols of PDMSU in EtOH were used. Contact angle measurements revealed the hydrophobicity of the coating, either on Al substrate (⊖ > 100°) or on cotton (⊖ ∼ 130°). IR attenuated total reflection (ATR) spectroscopy showed that urea groups participate in PDMSU/cotton interface bonding. while free urea groups (1725, 1691 cm were noted in the spectra of PDMSU/Al and PDMSU/xerogel samples. The stability of the coatings was determined by repetitive washing. Degradation of the coatings was evidenced from the decrease in contact angle values and the relaxation of the urea-urea associations, leading to the appearance of the new Amide II band (1541 cm -1 ) in the IR ATR spectra.

Research paper thumbnail of Biodegradability of cellulose fabric modified by imidazolidinone

Carbohydrate Polymers, 2007

The influence of modifying cellulose by imidazolidinone on its biodegradability was studied using... more The influence of modifying cellulose by imidazolidinone on its biodegradability was studied using the soil burial test and enzymatic hydrolysis. The degree of biodegradation was determined on the basis of scanning electron micrographs, tensile strength, degree of polymerization, polymer solubility measurements, and infrared spectroscopic analyses (FT-IR). The results show that the incorporation of 1,3-dimethyl-4,5-dihydroxyethylene urea into the structure of cellulose highly decreased the biodegradability of cellulose macromolecules. This was confirmed by the smaller morphological changes, lower decrease of breaking strength and lower polymer solubility determined for the modified cellulose. FT-IR spectra analysis also revealed that during the biodegradation period much greater structural damage was caused in the case of unmodified than of modified cellulose, and that the intensity of the bands at 1640 and 1548 belonging to the Amides I and II bonds resulting from the presence of protein produced by microbial growth.

Research paper thumbnail of Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Journal of Sol-Gel Science and Technology, 2008

Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres we... more Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS)(Degussa), nanosized silver (Ag)(CHT) and a reactive organic–inorganic binder (RB ...

Research paper thumbnail of Structural Properties and Antibacterial Effects of Hydrophobic and Oleophobic Sol−Gel Coatings for Cotton Fabrics

Langmuir, 2009

In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltrie... more In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltriethoxysilane [bis (aminopropyl)-terminated polydimethylsiloxane (1000)] (PDMSU) sol-gel hybrid, which forms washing-resistant water-repellent finishes on cotton fabrics, were further investigated. The addition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) to PDMSU resulted in a highly apolar low-energy surface on aluminum with γ S total equal to 14.5 mJ/m 2 and a ΔG iwi value of-82 mJ/m 2. Mixed PFOTES-PDMSU finishes applied on cotton fabrics increased the water contact angles (θ w) from ∼130°(PDMSU) to 147°, also imparting oleophobicity (θ diiodomethane = 130°, θ n-hexadecane = 120°) to the finished cotton fabrics. Washing caused breakage of the coating's integrity as established from SEM, which was attributed to the partial removal of PFOTES from the composite films, also shown by subtractive IR attenuated total reflectance (ATR) and XPS spectral measurements made on washed and unwashed fabrics. The antibacterial properties of the PFOTES-PDMSU-finished fabrics were assessed with the transfer method (EN ISO 20743:2007), revealing that the reduction of Escherichia coli bacteria on unwashed cotton fabrics was nearly 100%. Moreover, for washed (10 times) cotton fabrics a much higher bacterial reduction was noted for the PFOTES-PDMSU finishes (60.6 (10.8%), surpassing PDMSU (30.4 (6.1%) and commercial fluoroalkoxysilane (FAS) (21.9 (5.7%) finishes. The structure of PFOTES-PDMSU gels, xerogels, and the corresponding coatings was investigated by analyzing the 29 Si NMR and IR ATR spectra and comparing them with the spectra of PFOTES and octameric (T 8) PFOTES based polyhedra. The results revealed the tendency of PFOTES to condense in octameric silsesquioxane polyhedra (T 8), coexisting in the PDMSU sol-gel network with cyclic tetramers (T 4 (OH) 4) and open cube-like species (T 7 (OH) 3). The presence of-OH-functionalized PFOTES silsesquioxanes, established even in coatings heat-treated at 140°C (15 min), also explained the excellent washing fastness of PFOTES finishes on cotton fabrics. The regenerative nature of the water-and oil-repellent properties of washed PFOTES-PDMSU-finished cotton fabrics was attributed to the surface mobility of the T 8 PFOTES based polyhedra, ousted from the coating interior during consecutive washings.

Research paper thumbnail of Structural studies of TiO2/wood coatings prepared by hydrothermal deposition of rutile particles from TiCl4 aqueous solutions on spruce (Picea Abies) wood

Applied Surface Science, 2016

Research paper thumbnail of Adhesion and thermal stability of thickness insensitive spectrally selective (TISS) polyurethane-based paint coatings on copper substrates

Solar Energy Materials and Solar Cells, 2009

Thickness insensitive spectrally selective (TISS) paint coatings based on a polyurethane polymeri... more Thickness insensitive spectrally selective (TISS) paint coatings based on a polyurethane polymeric binder deposited on copper substrates were investigated to obtain information about their service lifetime. The degradation of TISS paint coatings was performed according to the methodology worked out within Task 10 of the IEA's Solar heating and the cooling programme. The activation energy (E a) for the degradation process was derived from vibrational band changes of the polyurethane binder recorded in the infrared hemispherical reflectance spectra of TISS paint coatings exposed to different thermal loads. The results of the vibrational band analysis were correlated with cross-cut tests, showing that the coatings started to lose integrity at 190 1C but protected the copper substrate against oxidation perfectly even at 200 1C (15 days). An accelerated test procedure confirmed that TISS coatings could be safely used in solar collectors for at least 45 years.

Research paper thumbnail of Structural and water-repellent properties of a urea/poly(dimethylsiloxane) sol-gel hybrid and its bonding to cotton fabric

Langmuir : the ACS journal of surfaces and colloids, Jan 18, 2006

A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (... more A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (PDMSU) sol-gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea-urea associations, as inferred from the appearance of a new amide II band at 1541 cm(-1).

Research paper thumbnail of Structural studies of sol–gel urea/polydimethylsiloxane barrier coatings and improvement of their corrosion inhibition by addition of various alkoxysilanes

Progress in Organic Coatings, 2008

A sol–gel organic–inorganic hybrid precursor, bis[(ureapropyl)triethoxysilane]bis(propyl)-termina... more A sol–gel organic–inorganic hybrid precursor, bis[(ureapropyl)triethoxysilane]bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU, for short), was tested as a corrosion barrier coating for AA 2024 aluminium alloy. The PDMSU coatings were prepared in either ethanol (PDMSU/EtOH) or propanol (PDMSU/PrOH) solvents. XRD measurements of xerogels showed the diffraction peak of amorphous silica domains at 21.5° and a broad peak at approximately 12.2°, which could be associated

Research paper thumbnail of Structural and Water-Repellent Properties of a Urea/Poly(dimethylsiloxane) Sol−Gel Hybrid and Its Bonding to Cotton Fabric

Langmuir, 2006

A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (... more A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (PDMSU) sol-gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea-urea associations, as inferred from the appearance of a new amide II band at 1541 cm(-1).

Research paper thumbnail of Corrosion Studies and Interfacial Bonding of Urea/Poly(dimethylsiloxane) Sol/Gel Hydrophobic Coatings on AA 2024 Aluminum Alloy

Langmuir, 2007

Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an org... more Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an organic-inorganic hybrid, diluted in either EtOH or a mixture of EtOH-PrOH, was used in thin film form (<200 nm) to inhibit the corrosion of AA 2024 alloy. Potentiodynamic, time-dependent cyclovoltammetric measurements and salt spray tests showed that the corrosion inhibition of the latter was 10 times higher than that of the former films. This was correlated with the higher degree of hydrolysis and the formation of more open polyhedral silsesquioxane species (T2) in the bulk heat-treated PDMSU/EtOH-PrOH xerogels (29Si NMR spectra). The structure of the coatings deposited on AA 2024 Al alloy was deduced from the infrared reflection-absorption (IR RA) spectra, which revealed more extensive urea-urea interactions and more efficient silane-Al interface bonding for the PDMSU/EtOH-PrOH coatings with higher corrosion inhibition. Ex situ IR RA potentiodynamic spectroelectrochemical measurements of PDMSU coatings revealed that their degradation did not proceed via the formation of silanol groups and consequent hydration of the coatings but that they decomposed above E(corr) by forming fragments composed of -CH2- segments in an all-trans conformation.

Research paper thumbnail of Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Journal of Sol-Gel Science and Technology, 2008

Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres we... more Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS)(Degussa), nanosized silver (Ag)(CHT) and a reactive organic–inorganic binder (RB ...

Research paper thumbnail of Hydrolysis and Solvolysis of Methyltriethoxysilane Catalyzed with HCl or Trifluoroacetic Acid: IR Spectroscopic and Surface Energy Studies

Journal of Sol-Gel Science and Technology, 2005

The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEO... more The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEOS) catalysed with HCl (hydrolysis) and to compare them with IR spectra of MTEOS catalysed with trifluoroacetic acid (TFAcOH). TFAcOH as a strong carboxylic acid performs non-hydrolytic sol-gel process based on the condensation between the alkoxide and the acid function, liberating ester molecules (solvolysis). We assessed from the timedependent IR attenuated reflection spectroscopic (IR ATR) measurements the solvolysis and hydrolysis reactions, formation of the oligomeric species and final condensation products. Additional evidence for the formation of these species was obtained from the spectra of films dip-coated from sols aged to different extent. The results of the IR spectral analysis showed that the structure of both xerogels consisted of irregular T n (n = 8, 10, 12) cube-like species bridged via the ladder-like oligomers (in the case of MTEOS/TFAcOH) and open-chain trisiloxane species (for MTEOS/HCl). 29 Si NMR spectra of MTEOS/TFAcOH showed only signals of T 3 while MTEOS/HCl spectra showed beside T 3 also T 2 signals, in agreement with IR spectra results. From the XRD peaks at low Bragg angles (∼ 9-10 • ) we inferred that both xerogels consisted of nanocrystalline CH 3 -SiO 3/2 species. In addition, the surface energy values of the films deposited from the corresponding sols were measured and the dispersive and polar portions correlated with the spectral features noted in the films.

Research paper thumbnail of Biodegradability of cellulose fabric modified by imidazolidinone

Carbohydrate Polymers, 2007

ABSTRACT The influence of modifying cellulose by imidazolidinone on its biodegradability was stud... more ABSTRACT The influence of modifying cellulose by imidazolidinone on its biodegradability was studied using the soil burial test and enzymatic hydrolysis. The degree of biodegradation was determined on the basis of scanning electron micrographs, tensile strength, degree of polymerization, polymer solubility measurements, and infrared spectroscopic analyses (FT-IR). The results show that the incorporation of 1,3-dimethyl-4,5-dihydroxyethylene urea into the structure of cellulose highly decreased the biodegradability of cellulose macromolecules. This was confirmed by the smaller morphological changes, lower decrease of breaking strength and lower polymer solubility determined for the modified cellulose. FT-IR spectra analysis also revealed that during the biodegradation period much greater structural damage was caused in the case of unmodified than of modified cellulose, and that the intensity of the bands at 1640 and 1548 belonging to the Amides I and II bonds resulting from the presence of protein produced by microbial growth.

Research paper thumbnail of Structural Properties and Antibacterial Effects of Hydrophobic and Oleophobic Sol−Gel Coatings for Cotton Fabrics

Langmuir, 2009

In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltrie... more In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltriethoxysilane [bis(aminopropyl)-terminated polydimethylsiloxane (1000)] (PDMSU) sol-gel hybrid, which forms washing-resistant water-repellent finishes on cotton fabrics, were further investigated. The addition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) to PDMSU resulted in a highly apolar low-energy surface on aluminum with gammaStotal equal to 14.5 mJ/m2 and a DetlaGiwi value of -82 mJ/m2. Mixed PFOTES-PDMSU finishes applied on cotton fabrics increased the water contact angles (thetaw) from approximately 130 degrees (PDMSU) to 147 degrees, also imparting oleophobicity (thetadiiodomethane=130 degrees, thetan-hexadecane=120 degrees) to the finished cotton fabrics. Washing caused breakage of the coating's integrity as established from SEM, which was attributed to the partial removal of PFOTES from the composite films, also shown by subtractive IR attenuated total reflectance (ATR) and XPS spectral measurements made on washed and unwashed fabrics. The antibacterial properties of the PFOTES-PDMSU-finished fabrics were assessed with the transfer method (EN ISO 20743:2007), revealing that the reduction of Escherichia coli bacteria on unwashed cotton fabrics was nearly 100%. Moreover, for washed (10 times) cotton fabrics a much higher bacterial reduction was noted for the PFOTES-PDMSU finishes (60.6+/-10.8%), surpassing PDMSU (30.4+/-6.1%) and commercial fluoroalkoxysilane (FAS) (21.9+/-5.7%) finishes. The structure of PFOTES-PDMSU gels, xerogels, and the corresponding coatings was investigated by analyzing the 29Si NMR and IR ATR spectra and comparing them with the spectra of PFOTES and octameric (T8) PFOTES based polyhedra. The results revealed the tendency of PFOTES to condense in octameric silsesquioxane polyhedra (T8), coexisting in the PDMSU sol-gel network with cyclic tetramers (T4(OH)4) and open cube-like species (T7(OH)3). The presence of -OH-functionalized PFOTES silsesquioxanes, established even in coatings heat-treated at 140 degrees C (15 min), also explained the excellent washing fastness of PFOTES finishes on cotton fabrics. The regenerative nature of the water- and oil-repellent properties of washed PFOTES-PDMSU-finished cotton fabrics was attributed to the surface mobility of the T8 PFOTES based polyhedra, ousted from the coating interior during consecutive washings.

Research paper thumbnail of Hydrophobic properties and water-vapour transmission of surface treated and non-treated wood, modified with TiO2

Research paper thumbnail of Vpliv vsebnosti vode v smrekovem lesu na kakovost hidrotermalne depozicije TiO2 na površini lesnih vzorcev

Research paper thumbnail of Functionalisation of cotton with hydrophobic urea/polydimethylsiloxane sol-gel hybrid

Acta Chimica Slovenica

A novel organic-inorganic sol-gel hybrid precursor, di-ureapropyltriethoxysilyl [bis aminopropyl)... more A novel organic-inorganic sol-gel hybrid precursor, di-ureapropyltriethoxysilyl [bis aminopropyl)terminated-polydimethylsiloxane (1000)| (PDMSU), was synthesized and tested as a hydrophobic impregnation for cotton fabrics. Hydrolysis of the precursor was performed with 0.1 mol L -1 HCl and for deposition 4% sols of PDMSU in EtOH were used. Contact angle measurements revealed the hydrophobicity of the coating, either on Al substrate (⊖ > 100°) or on cotton (⊖ ∼ 130°). IR attenuated total reflection (ATR) spectroscopy showed that urea groups participate in PDMSU/cotton interface bonding. while free urea groups (1725, 1691 cm were noted in the spectra of PDMSU/Al and PDMSU/xerogel samples. The stability of the coatings was determined by repetitive washing. Degradation of the coatings was evidenced from the decrease in contact angle values and the relaxation of the urea-urea associations, leading to the appearance of the new Amide II band (1541 cm -1 ) in the IR ATR spectra.

Research paper thumbnail of Biodegradability of cellulose fabric modified by imidazolidinone

Carbohydrate Polymers, 2007

The influence of modifying cellulose by imidazolidinone on its biodegradability was studied using... more The influence of modifying cellulose by imidazolidinone on its biodegradability was studied using the soil burial test and enzymatic hydrolysis. The degree of biodegradation was determined on the basis of scanning electron micrographs, tensile strength, degree of polymerization, polymer solubility measurements, and infrared spectroscopic analyses (FT-IR). The results show that the incorporation of 1,3-dimethyl-4,5-dihydroxyethylene urea into the structure of cellulose highly decreased the biodegradability of cellulose macromolecules. This was confirmed by the smaller morphological changes, lower decrease of breaking strength and lower polymer solubility determined for the modified cellulose. FT-IR spectra analysis also revealed that during the biodegradation period much greater structural damage was caused in the case of unmodified than of modified cellulose, and that the intensity of the bands at 1640 and 1548 belonging to the Amides I and II bonds resulting from the presence of protein produced by microbial growth.

Research paper thumbnail of Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Journal of Sol-Gel Science and Technology, 2008

Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres we... more Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS)(Degussa), nanosized silver (Ag)(CHT) and a reactive organic–inorganic binder (RB ...

Research paper thumbnail of Structural Properties and Antibacterial Effects of Hydrophobic and Oleophobic Sol−Gel Coatings for Cotton Fabrics

Langmuir, 2009

In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltrie... more In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltriethoxysilane [bis (aminopropyl)-terminated polydimethylsiloxane (1000)] (PDMSU) sol-gel hybrid, which forms washing-resistant water-repellent finishes on cotton fabrics, were further investigated. The addition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) to PDMSU resulted in a highly apolar low-energy surface on aluminum with γ S total equal to 14.5 mJ/m 2 and a ΔG iwi value of-82 mJ/m 2. Mixed PFOTES-PDMSU finishes applied on cotton fabrics increased the water contact angles (θ w) from ∼130°(PDMSU) to 147°, also imparting oleophobicity (θ diiodomethane = 130°, θ n-hexadecane = 120°) to the finished cotton fabrics. Washing caused breakage of the coating's integrity as established from SEM, which was attributed to the partial removal of PFOTES from the composite films, also shown by subtractive IR attenuated total reflectance (ATR) and XPS spectral measurements made on washed and unwashed fabrics. The antibacterial properties of the PFOTES-PDMSU-finished fabrics were assessed with the transfer method (EN ISO 20743:2007), revealing that the reduction of Escherichia coli bacteria on unwashed cotton fabrics was nearly 100%. Moreover, for washed (10 times) cotton fabrics a much higher bacterial reduction was noted for the PFOTES-PDMSU finishes (60.6 (10.8%), surpassing PDMSU (30.4 (6.1%) and commercial fluoroalkoxysilane (FAS) (21.9 (5.7%) finishes. The structure of PFOTES-PDMSU gels, xerogels, and the corresponding coatings was investigated by analyzing the 29 Si NMR and IR ATR spectra and comparing them with the spectra of PFOTES and octameric (T 8) PFOTES based polyhedra. The results revealed the tendency of PFOTES to condense in octameric silsesquioxane polyhedra (T 8), coexisting in the PDMSU sol-gel network with cyclic tetramers (T 4 (OH) 4) and open cube-like species (T 7 (OH) 3). The presence of-OH-functionalized PFOTES silsesquioxanes, established even in coatings heat-treated at 140°C (15 min), also explained the excellent washing fastness of PFOTES finishes on cotton fabrics. The regenerative nature of the water-and oil-repellent properties of washed PFOTES-PDMSU-finished cotton fabrics was attributed to the surface mobility of the T 8 PFOTES based polyhedra, ousted from the coating interior during consecutive washings.

Research paper thumbnail of Structural studies of TiO2/wood coatings prepared by hydrothermal deposition of rutile particles from TiCl4 aqueous solutions on spruce (Picea Abies) wood

Applied Surface Science, 2016

Research paper thumbnail of Adhesion and thermal stability of thickness insensitive spectrally selective (TISS) polyurethane-based paint coatings on copper substrates

Solar Energy Materials and Solar Cells, 2009

Thickness insensitive spectrally selective (TISS) paint coatings based on a polyurethane polymeri... more Thickness insensitive spectrally selective (TISS) paint coatings based on a polyurethane polymeric binder deposited on copper substrates were investigated to obtain information about their service lifetime. The degradation of TISS paint coatings was performed according to the methodology worked out within Task 10 of the IEA's Solar heating and the cooling programme. The activation energy (E a) for the degradation process was derived from vibrational band changes of the polyurethane binder recorded in the infrared hemispherical reflectance spectra of TISS paint coatings exposed to different thermal loads. The results of the vibrational band analysis were correlated with cross-cut tests, showing that the coatings started to lose integrity at 190 1C but protected the copper substrate against oxidation perfectly even at 200 1C (15 days). An accelerated test procedure confirmed that TISS coatings could be safely used in solar collectors for at least 45 years.

Research paper thumbnail of Structural and water-repellent properties of a urea/poly(dimethylsiloxane) sol-gel hybrid and its bonding to cotton fabric

Langmuir : the ACS journal of surfaces and colloids, Jan 18, 2006

A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (... more A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (PDMSU) sol-gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea-urea associations, as inferred from the appearance of a new amide II band at 1541 cm(-1).

Research paper thumbnail of Structural studies of sol–gel urea/polydimethylsiloxane barrier coatings and improvement of their corrosion inhibition by addition of various alkoxysilanes

Progress in Organic Coatings, 2008

A sol–gel organic–inorganic hybrid precursor, bis[(ureapropyl)triethoxysilane]bis(propyl)-termina... more A sol–gel organic–inorganic hybrid precursor, bis[(ureapropyl)triethoxysilane]bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU, for short), was tested as a corrosion barrier coating for AA 2024 aluminium alloy. The PDMSU coatings were prepared in either ethanol (PDMSU/EtOH) or propanol (PDMSU/PrOH) solvents. XRD measurements of xerogels showed the diffraction peak of amorphous silica domains at 21.5° and a broad peak at approximately 12.2°, which could be associated

Research paper thumbnail of Structural and Water-Repellent Properties of a Urea/Poly(dimethylsiloxane) Sol−Gel Hybrid and Its Bonding to Cotton Fabric

Langmuir, 2006

A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (... more A novel diureapropyltriethoxysilane [bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000)] (PDMSU) sol-gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea-urea associations, as inferred from the appearance of a new amide II band at 1541 cm(-1).

Research paper thumbnail of Corrosion Studies and Interfacial Bonding of Urea/Poly(dimethylsiloxane) Sol/Gel Hydrophobic Coatings on AA 2024 Aluminum Alloy

Langmuir, 2007

Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an org... more Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an organic-inorganic hybrid, diluted in either EtOH or a mixture of EtOH-PrOH, was used in thin film form (<200 nm) to inhibit the corrosion of AA 2024 alloy. Potentiodynamic, time-dependent cyclovoltammetric measurements and salt spray tests showed that the corrosion inhibition of the latter was 10 times higher than that of the former films. This was correlated with the higher degree of hydrolysis and the formation of more open polyhedral silsesquioxane species (T2) in the bulk heat-treated PDMSU/EtOH-PrOH xerogels (29Si NMR spectra). The structure of the coatings deposited on AA 2024 Al alloy was deduced from the infrared reflection-absorption (IR RA) spectra, which revealed more extensive urea-urea interactions and more efficient silane-Al interface bonding for the PDMSU/EtOH-PrOH coatings with higher corrosion inhibition. Ex situ IR RA potentiodynamic spectroelectrochemical measurements of PDMSU coatings revealed that their degradation did not proceed via the formation of silanol groups and consequent hydration of the coatings but that they decomposed above E(corr) by forming fragments composed of -CH2- segments in an all-trans conformation.

Research paper thumbnail of Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Journal of Sol-Gel Science and Technology, 2008

Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres we... more Abstract Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS)(Degussa), nanosized silver (Ag)(CHT) and a reactive organic–inorganic binder (RB ...

Research paper thumbnail of Hydrolysis and Solvolysis of Methyltriethoxysilane Catalyzed with HCl or Trifluoroacetic Acid: IR Spectroscopic and Surface Energy Studies

Journal of Sol-Gel Science and Technology, 2005

The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEO... more The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEOS) catalysed with HCl (hydrolysis) and to compare them with IR spectra of MTEOS catalysed with trifluoroacetic acid (TFAcOH). TFAcOH as a strong carboxylic acid performs non-hydrolytic sol-gel process based on the condensation between the alkoxide and the acid function, liberating ester molecules (solvolysis). We assessed from the timedependent IR attenuated reflection spectroscopic (IR ATR) measurements the solvolysis and hydrolysis reactions, formation of the oligomeric species and final condensation products. Additional evidence for the formation of these species was obtained from the spectra of films dip-coated from sols aged to different extent. The results of the IR spectral analysis showed that the structure of both xerogels consisted of irregular T n (n = 8, 10, 12) cube-like species bridged via the ladder-like oligomers (in the case of MTEOS/TFAcOH) and open-chain trisiloxane species (for MTEOS/HCl). 29 Si NMR spectra of MTEOS/TFAcOH showed only signals of T 3 while MTEOS/HCl spectra showed beside T 3 also T 2 signals, in agreement with IR spectra results. From the XRD peaks at low Bragg angles (∼ 9-10 • ) we inferred that both xerogels consisted of nanocrystalline CH 3 -SiO 3/2 species. In addition, the surface energy values of the films deposited from the corresponding sols were measured and the dispersive and polar portions correlated with the spectral features noted in the films.

Research paper thumbnail of Biodegradability of cellulose fabric modified by imidazolidinone

Carbohydrate Polymers, 2007

ABSTRACT The influence of modifying cellulose by imidazolidinone on its biodegradability was stud... more ABSTRACT The influence of modifying cellulose by imidazolidinone on its biodegradability was studied using the soil burial test and enzymatic hydrolysis. The degree of biodegradation was determined on the basis of scanning electron micrographs, tensile strength, degree of polymerization, polymer solubility measurements, and infrared spectroscopic analyses (FT-IR). The results show that the incorporation of 1,3-dimethyl-4,5-dihydroxyethylene urea into the structure of cellulose highly decreased the biodegradability of cellulose macromolecules. This was confirmed by the smaller morphological changes, lower decrease of breaking strength and lower polymer solubility determined for the modified cellulose. FT-IR spectra analysis also revealed that during the biodegradation period much greater structural damage was caused in the case of unmodified than of modified cellulose, and that the intensity of the bands at 1640 and 1548 belonging to the Amides I and II bonds resulting from the presence of protein produced by microbial growth.

Research paper thumbnail of Structural Properties and Antibacterial Effects of Hydrophobic and Oleophobic Sol−Gel Coatings for Cotton Fabrics

Langmuir, 2009

In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltrie... more In a continuation of previous studies, the wetting properties of the hydrophobic diureapropyltriethoxysilane [bis(aminopropyl)-terminated polydimethylsiloxane (1000)] (PDMSU) sol-gel hybrid, which forms washing-resistant water-repellent finishes on cotton fabrics, were further investigated. The addition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) to PDMSU resulted in a highly apolar low-energy surface on aluminum with gammaStotal equal to 14.5 mJ/m2 and a DetlaGiwi value of -82 mJ/m2. Mixed PFOTES-PDMSU finishes applied on cotton fabrics increased the water contact angles (thetaw) from approximately 130 degrees (PDMSU) to 147 degrees, also imparting oleophobicity (thetadiiodomethane=130 degrees, thetan-hexadecane=120 degrees) to the finished cotton fabrics. Washing caused breakage of the coating's integrity as established from SEM, which was attributed to the partial removal of PFOTES from the composite films, also shown by subtractive IR attenuated total reflectance (ATR) and XPS spectral measurements made on washed and unwashed fabrics. The antibacterial properties of the PFOTES-PDMSU-finished fabrics were assessed with the transfer method (EN ISO 20743:2007), revealing that the reduction of Escherichia coli bacteria on unwashed cotton fabrics was nearly 100%. Moreover, for washed (10 times) cotton fabrics a much higher bacterial reduction was noted for the PFOTES-PDMSU finishes (60.6+/-10.8%), surpassing PDMSU (30.4+/-6.1%) and commercial fluoroalkoxysilane (FAS) (21.9+/-5.7%) finishes. The structure of PFOTES-PDMSU gels, xerogels, and the corresponding coatings was investigated by analyzing the 29Si NMR and IR ATR spectra and comparing them with the spectra of PFOTES and octameric (T8) PFOTES based polyhedra. The results revealed the tendency of PFOTES to condense in octameric silsesquioxane polyhedra (T8), coexisting in the PDMSU sol-gel network with cyclic tetramers (T4(OH)4) and open cube-like species (T7(OH)3). The presence of -OH-functionalized PFOTES silsesquioxanes, established even in coatings heat-treated at 140 degrees C (15 min), also explained the excellent washing fastness of PFOTES finishes on cotton fabrics. The regenerative nature of the water- and oil-repellent properties of washed PFOTES-PDMSU-finished cotton fabrics was attributed to the surface mobility of the T8 PFOTES based polyhedra, ousted from the coating interior during consecutive washings.