UV ageing studies: evaluation of lightfastness declarations of commercial acrylic paints

The lightfastness declarations of several different commercial acrylic paints and different quality series were tested by artificial UV ageing. To evaluate their lightfastness declarations, three acrylic colours (cadmium red, ultramarine blue and chromium oxide green) from six companies (Lascaux, Liquitex, Lukas, Rembrandt, Schmincke, and Winsor & Newton) were analysed before and after UV exposure. Characterisation and identification of these materials were carried out with Py–GC/MS, FTIR–ATR analyses, and colour measurements. Particular attention was focused on the Py–GC/MS measurements and on comparison of the single-shot method for pyrolysis of polymers and the double-shot mode which enables a unique combination of pyrolysis methods for analysis of polymers and thermal desorption for documentation of the volatile compounds. Depending on the particular company and the specific value of the lightfastness declaration, different binding media (i.e. poly(EA/MMA), poly(nBA/MMA), and poly(2-EHA/MMA)), and fillers (i.e. kaolinite, calcium carbonate, barite, and talc) were characterised and identified by Py–GC/MS and FTIR–ATR analyses. After UV exposure, several alteration processes with consequent formation of volatile compounds or new products were observed by both techniques, especially for the blue paints. In particular, the double-shot mode of Py–GC/MS enabled the detection of oxidation products, which could not be detected with the single-shot mode. Comparison of the lightfastness declarations for each of the blue, green, and red paints and the noted alterations broadly agreed for most of the paints.     

X-ray absorption spectroscopy of ultramarine pigments: A new analytical method for the polysulfide radical anion S3 chromophore

Blue and mauve ultramarine artists' pigments and their heat-treated products have been investigated by sulfur K-edge X-ray absorption. X-ray absorption near-edge structure spectra are dominated by features of reduced sulfur and sulfate species. There is also a pre-peak at about 2468.0 eV which reflects the presence of the unpaired electron on the polysulfide radical anion (S₃⁻). Pre-peak intensity is directly proportional to the depth of blue coloration, and provides a new, independent method for estimating the proportion of ultramarine cage sites occupied by the blue chromophore. The occupancy of the polysulfide radical anion S₃⁻ is estimated to be 33% in an intense ultramarine blue pigment, 22% in a dark blue ultramarine pigment, and 1% in deep royal blue lazurite from Afghanistan. The more efficient development of color in lazurite is attributed to extensive annealing of the mineral structure in the natural environment.     

Synthesis and characterization of environmentally benign calcium-doped Pr2Mo2O9 pigments: Applications in coloring of plastics

A new class of environmentally benign rare earth pigments of general formula Pr_2−xCa_xMo₂O_9−δ (x ranges from 0 to 1.0) displaying colors ranging from green to yellow were synthesized by traditional solid-state route, as alternatives to lead, cadmium and chromium colorants. The products were characterized by X-ray powder diffraction, UV-vis spectroscopy and CIE-L*a*b* 1976 color scales. The coloring mechanism is based on the strong absorptions of the pigments in the blue and red regions due to electronic transitions between 4f²→4f¹5d¹ states of Pr³⁺. The designed pigments consist of non-toxic elements and further found to be thermally and chemically stable. The yellow-green pigments were found to be interesting alternatives to existing toxic pigments for coloration of plastics.     

A DSC study of the effect of lead pigments on the drying of cold pressed linseed oil

Cold pressed linseed oil and paints prepared using the inorganic pigments; lead white and red lead, were characterized using non-isothermal differential scanning calorimetry (DSC) in an air atmosphere to determine the effect of the pigment on the oxidative polymerisation of the drying oil medium. For each paint sample, the onset temperature for oxidation was reduced from 166°C to the range 50 to 60°C when a heating rate of 5 K min^-1 was used. In order to determine the rate of drying, the non-isothermal experiments were carried out using a range of heating rates. A change in the mechanism oxidative polymerization was observed as the heating rate was increased.     

Thermal runaway reaction evaluation of benzoyl peroxide using calorimetric approaches

Benzoyl peroxide (BPO) has been used as initiator or medicine in the chemical industries. Several thermal runaway reactions, fires, and explosions have occurred in Taiwan due to its thermal reactivity and explosive properties. A serious accident was analyzed occurring at Fu-Kao Chemical Plant in Taiwan because of runaway reaction in a batch reactor including methyl acrylate (MA), acrylic acid (AA), and BPO. This accident resulted in one death and more than 100 injuries. Differential scanning calorimetry and thermogravimetry (TG) were used to investigate and calculate the thermal hazard and safety parameter of BPO. Finally, the effects of MA and AA mixed with BPO by DSC/TG were analyzed in this study. The T ₀ of BPO was 109 °C in this study. Therefore, the T ₀ of BPO/MA was calculated to be 105 °C by DSC. AA and MA were identified as catalyst for thermal decomposition of BPO.     

Thermal studies on purine complexes. I. Thermal behaviour of some xanthine complexes of cobalt(II), copper(II) and cadmium(II)

Cobalt, copper and cadmium xanthinate tetrahydrates have been prepared in aqueous medium, and characterized on the basis of elemental analysis, IR and ¹HNMR studies. The thermal behaviour of these compounds has been studied using TG, DTG and DSC techniques. Heats of dehydration have been calculated from DSC curves.     

Characterization and identification of acrylic binding media: influence of UV light on the ageing process

This study characterizes and identifies two different acrylic binding media such as Plextol® D498 and Primal® AC33, which are widely used in modern and contemporary art. In order to investigate their fast photooxidative deterioration when exposed to ultraviolet (UV) light, ageing studies on these materials were carried out. For this purpose, pure synthetic materials but also mixed with different inorganic pigments were identified and characterized before and after UV exposure by means of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Particular attention was paid to the comparison of two different analytical methods: (1) single-shot method based on a pyrolysis for the analysis of polymers and (2) double-shot method, which allows a unique combination of thermal desorption for the analysis of volatile compounds and pyrolysis of the polymers themselves. These analyses have been complemented by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) studies. The comparison of the results obtained from unaged samples and UV-aged clearly showed material alterations as well as the formation of new products, which were recorded by FTIR-ATR. Generally, these changes were more pronounced when the acrylic binding media were mixed with pigments. The double-shot technique of Py-GC/MS additionally allowed the detection of the phenolic antioxidant in unaged Plextol® D498, but no oxidation products could be identified by Py-GC/MS in all samples.     

Assessment of the impact of bacteria Pseudomonas denitrificans,Pseudomonas fluorescens,Bacillus subtilis and yeast Yarrowia lipolytica on commercial poly(ether urethanes)

The assessment of the impact of the bacteria Pseudomonas denitrificans, Pseudomonas fluorescens, Bacillus subtilis and yeast Yarrowia lipolytica on commercial poly(ether urethanes) Tecoflex^® and Tecothane^® is presented. The polyurethane samples were incubated with pure cultures of the microorganisms at 30 °C for five months. The changes in the chemical structure of the polymers were evaluated using loss of weight and contact angle measurements, infrared spectroscopy (ATR-FTIR), mass spectrometry (Py-MS), differential scanning calorimetry (DSC) and the thermogravimetric analysis (TG). In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied for imaging changes in surface morphology of the poly(ether urethanes). Comparative analysis of these polyurethane features before and after incubation with the microorganism cultures showed that Tecoflex^® was less stable than Tecothane^®. This can be explained by the presence of aromatic rings within the diphenylmethane diisocyanate group in the chemical structure of the latter. Bacterial strains of Bacillus subtilis and Pseudomonas fluorescens showed a much more prominent destructive effect compared to the strain of yeast Y. lipolytica.     

Oscillatory diffuse X-ray scattering from lead chalcogenides

New inorganic compounds having the general formula (Bi₂O₃)_1−x (Lu₂O₃) _x (x ranges from 0.1 to 0.5) displaying orange colours have been synthesized by traditional solid-state route, as viable alternatives to lead, cadmium and chromium based yellow toxic inorganic pigments. The host lattice of these pigments is Bi₂O₃ that is doped by Lu³⁺ ions. The goal was to develop conditions for the synthesis of these compounds and to determine the influence of calcination temperature and lutetium content on their colouring effects. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. The pigments were also evaluated from the standpoint of their structure and particle sizes.     

The infrared microspectroscopic and energy dispersive X-ray analysis of paints removed from a painted, medieval sculpture of Saint Wolfgang

A spectroscopic study of paints removed from a 15th century sculpture depicting Saint Wolfgang, which is housed in the Ball State Museum of Art, was performed. Infrared spectra on the minute paint samples were obtained using a microscope accessory in the transmission mode, and the spectra were compared to reference spectra of known art pigments and materials. In addition, energy dispersive X-ray spectra were obtained using a scanning electron microscope source. Although many of the pigments found are relatively modern pigments, the first application of paint is composed of materials consistent with the sculpture's medieval date. Pigments identified include brass gilding, calcium carbonate, China clay, lac dye, orpiment, Prussian blue, satin ochre, ultramarine blue and red, and zinc chromate. A zinc tungate finish was also identified.     

Micro-Raman analysis of coloured lithographs

Raman micro-spectroscopy was chosen for analysis and identification of the pigments present in four nineteenth-century hand-coloured lithographs, as this technique has several advantages over others for this purpose. The possibility of performing completely non-destructive analysis without any sampling is probably one of its most favourable qualities for art analysis. Raman spectroscopy can also be used to determine some pigments that cannot be detected using FTIR, such as vermilion, carbon blacks, cadmium pigments, etc. Among others, Prussian blue, ultramarine blue, carbon black, chrome yellow, yellow ochre, red lead, red iron oxide, burnt Sienna, indigo blue, chrome orange, phthalocyanine green, and some other organic pigments, were determined in the specimens. The results obtained have led to doubts about the age of the lithographs.     

The resonance Raman spectrum of ultramarine blue

The resonance Raman spectrum of ultramarine blue has been observed by the use of 457.9, 488.0, 514.5, 568.2 and 647.1 nm excitation. With 457.9 nm excitation three progressions are observed; comparison of the results with earlier data from sulphur-doped alkali halide crystals indicates that ultramarine blue contains the S₂^? as well as the S₃^? anion.     

Effects of various fire-extinguishing reagents for thermal hazard of triacetone triperoxide (TATP) by DSC/TG

Acetone, hydrogen peroxide (H₂O₂), and sulfuric acid (H₂SO₄) are easily to produce triacetone triperoxide (TATP), which is an organic peroxide and a hazardous material. The aim of this study was to analyze the thermal hazard of various fire-extinguishing reagents mixed with TATP. Various functions of fire-extinguishing reagents may have different extent of reactions with TATP. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG) were used to detect the thermal hazard and to evaluate the effect of fire-extinguishing reagents mixed with TATP under fire condition. TATP decomposed rapidly and final decomposition was calculated before 200 °C. Therefore, heat of decomposition (ΔH _d) of TATP was evaluated to be 2,500 J g^?1 by DSC under 2 °C min^?1 of heating rate. H₂O₂, acetone, and H₂SO₄ should not be mixed in a wastewater drum. TATP decomposed at 50 °C by DSC using O₂ of reaction gas that is an exothermic reaction and can decompose a large amount of heat. Therefore, TATP was applied to assess thermal pyrolysis by DSC employing N₂ of reaction gas that can analyze an endothermic reaction. Mass loss percentage of TATP was evaluated to be 100 % when the ambient temperature exceeds 110 °C by TG using O₂ or N₂ of reaction gas.     

Synthesis and study of mixed oxide inorganic pigment from Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO–CeO<Subscript>2</Subscript> system

Novel environment-friendly yellow mixed oxide inorganic pigment from Bi₂O₃–ZnO–CeO₂ system with the composition 23 mol% Bi₂O₃, 15 mol% ZnO and 62 mol% CeO₂ was successfully synthesized by a conventional solid-state reaction method. Comprehensive analyses were carried out to characterize the develop pigment powder including simultaneous TG–DTA thermal analysis, colour properties and particle size distribution. The results demonstrated that the optimum calcination for pigment synthesis was located at a range 800–950 °C. The colour of the studied mixed oxide pigment is connected with the calcination condition. The substitution of Zn²⁺ changes the colour from orange to yellow. The colour of the obtained samples was dependent on the calcination condition and the particle size distribution. The most saturated yellow hue was obtained at the calcination temperature of 950 °C for 2 h in a furnace of pure air and after its application into organic binder in mass tone. The value C of this sample was approx. 65. The mixed oxide pigments were also evaluated from the standpoint of their particle size distribution. Bi₂Ce₂O₇ is considered to be a non-toxic compound, and the other component (Zn²⁺ ions) is also the safe element. Therefore, the present mixed oxide could be an attractive candidate as a novel environment-friendly inorganic yellow pigment.     

Study of stability and drug-excipient compatibility of diethylcarbamazine citrate

Diethylcarbamazine citrate (DEC) is the main drug used in the lymphatic filariasis treatment. This study aimed to evaluate drug-excipient compatibility of binary mixtures (BMs) (1:1, w/w), initially by differential scanning calorimetry (DSC), and subsequently, if there were any interaction evidence, by complementary techniques, such as thermogravimetric (TG), non-isothermal kinetics, Fourier transform infrared (FT-IR), and X-ray diffraction (XRD). For the analyses of the BMs by DSC, we selected those with Tabletose^®, representing the excipients containing lactose, polivinilpirrolidona (PVP), and magnesium stearate (MgS). The additional analyses by FT-IR and XRD showed no interaction evidence. The TG curves of DEC–Tabletose^® showed no signs of interaction, unlike the TG curves of PVP and MgS, confirming the results of non-isothermal kinetics, in which the BMs with PVP and MgS decreased the reaction activation energy. Thus, it was concluded after evaluation that the excipients, especially the PVP and MgS, should be avoided.     

Investigation of thermal behavior of Heliotropium indicum L. lyophilized extract by TG and DSC

Thermogravimetric (TG) techniques and differential scanning calorimetry (DSC) used for the study of pre-formulation or drug–adjuvant compatibility have been gaining importance in Brazil. These techniques are being used for the verification of possible interactions between drugs and adjuvants. Aiming at studying the behavior of a plant extract and its mixture with adjuvants, using these thermoanalytical techniques the plant species Heliotropium indicum L. was used. This plant which is originally from India and has been well acclimatized in Brazil has healing and anti-inflammatory properties. The methodology for obtaining the extract followed the Brazilian Pharmacopoeia methodology. And the incorporation of the extract with adjuvants was through binary mixtures (1:1 w/w). The TG and DSC curves were obtained under nitrogen atmosphere (25 mL min^?1) at a heating rate of 5 °C min^?1; TG tests were analyzed within a temperature range from 25 to 600 °C and DSC from 25 to 300 °C. The TG curves show good thermal stability of the extract and its mixtures with adjuvants up to 150 °C, except the propylene glycol (PLG). The DSC curves revealed an incompatibility of the extract with methylparaben and PLG mixture.     

Discriminating Amino Resin Paints From Alkyd Resin Paints with Two Kinds of Pigments in Automotive Coatings in Forensic Analysis by FTIR Spectroscopy

The analysis of automotive coatings is important to forensic scientists, especially in the investigation of hit-and-run accidents. Amino resin paints, alkyd resin paints, and polyurethane paints are all popular automotive coatings. In this study, FTIR was employed to investigate these coatings, particular in amino resin paints. IR spectra were tentatively interpreted. The indicative peaks distinguishing amino resin paints (1550 cm^?1) and alkyd resin paints (1600 cm^?1/1580 cm^?1) were summarized. Two kinds of alkyd resin paints (with the Pigment Scarlet Powder and with the Toluidine Red), which were frequently confronted in cases and might readily be read as amino resin paints in IR spectra, were studied and interpreted. The indicative peaks (1619 cm^?1, 776 cm^?1 and 1674 cm^?1, 1494 cm^?1) were selected to discriminate these two kinds of alkyd resin paints from amino resin paints and avoid an incorrect certificate of authenticity. The data in this study can help the forensic scientists identify these three paints accurately, especially in the cases with the interference of the pigments.     

Study of ceramic pigments based on Er2Ce2?x Mo x O7

This contribution is focused on the synthesis, characterization and optical properties of new inorganic pigments which are environment friendly and can substitute some toxic metals in interesting colour compounds. Pyrochlores belong to the group of high-temperature pigments, and are a variety of actual and potential applications for several materials. Examples include catalysts, thermal barrier coatings, solid electrolytes, nuclear waste forms and host materials for luminescence centers. The pigments were prepared by the solid state reaction and also by method of suspension mixing of materials in the series with increasing content of molybdenum. The pigments were applied into organic matrix and ceramic glaze. The colour properties of these applications were investigated depending on content of Mo, method of preparation and temperature of calcination (1350?C1550?°C after step 50?°C). The optimum conditions for their synthesis were determined. The pigments were evaluated from standpoint of their structure, colour and particle sizes. Characterization of Er₂Ce_2?x Mo _x O₇ pigments (x?=?0.1, 0.3, 0.5 and 0.7) suggests that they have a potential to be alternative yellow or orange colourants for paints, plastics, ceramics and building materials.     

Thermal and structural properties of commercial dental resins light-cured with blue emitting diodes (LEDs)

We have investigated the thermal and structural properties of different commercial dental resins: Filtek^TM Z-350, Grandio^®, Tetric Ceram^®, and TPH Spectrum^®. The purpose of the present study was to evaluate quantitatively the photo-polymerization behavior and the effect of filler contents on the kinetic cures of the dental resins by using Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. We have successfully obtained the low and high glass transition T _g values of the dental composite resins from DSC curves. It was also observed a good agreement between the both T _g values, activation energies from thermal degradation, and the degree of conversion obtained for all samples. The results have shown that Tetric Ceram^® dental resin presented the higher T _g values, activation energy of 215 ± 6 KJ mol^?1, and the higher degree of conversion (63%) when compared to the other resins studied herein.     

Solid-state thermal decomposition of heterobimetallic oxalate coordination compounds, zinc(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate

Two heterobimetallic oxalate coordination compounds, zinc(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (ZnOLa) and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate (CdOLa) were synthesized and characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. Both the compounds were found to have monoclinic structure. Thermal decomposition studies by TG, DTG and DTA in air have proved that the aqua ligands are associated with metals in a stronger coordination mode. The temperatures for pyrolysis were adopted from the TG results chosen from the stable range of thermograms. In case of ZnOLa, it decomposes through two steps and the end product at 1000 °C was found to be consisting of mainly, La₂O_3, ZnO and La₂ZnO _x through the intermediate formation of several oxycarbonates of lanthanum at ca. 525 °C. In case of cadmium analogue, three steps decomposition were observed and the final products were confirmed as CdO₂, La₂O₃, LaCO and La₂CdO _x via the formation of several intermediates at 340 and 590 °C. The La₂C₃ and carbon are also found as part of the end product. The kinetic parameters, E ^*, lnk _o, ?H ^# and ?S ^# of all the deaquated and decomposition steps are investigated and discussed from the DSC study in nitrogen.