49 research outputs found

    Modification, characterization, analysis and life-science application of polymers: Polypropylene

    Get PDF
    Three stepwise chemical approaches were developed to transform commercially available isotactic polypropylene tubes into specialty' plastics for application in the life sciences: Oxidation. Ordinary polypropylene surfaces were oxidatively transformed inlo highsurface plastics bearing reactive surface groups by reaction with aqueous persulfate. Attcnuated-Total-Refiectance (ATR) infrared spcctroscopic analysis indicated that ketone, carboxylic acid and hydroxyl groups were afforded within the plastic. Surface analyses using optical microscopy revealed the formation of macroscopic parallel cracks. More importantly, scanning electron microscopy indicated the reacted material had developed a mesoscopic topology remarkably similar in appearance to microvilli. Protein immobilization experiments conducted using (luorescently labeled albumin served to quantify the performance of oxidized surfaces. Facile detection by visual observation under OV light disclosed that adsorbed protein was released during sequential washings of the tubes in high salt, low salt and detergent solutions. TEOS deposition. Hydrolysis products of tetraethoxysilane were cured onto oxidized, high-surface polypropylenes, affording tubes coated with prc-glass layers on the walls. ATR infrared spcctroscopic analyses verified the glass-like end product. These modified surfaces possessed the appropriate physico-chemical trails to reversibly bind mRNA, thus establishing the concept of a tube-mediated approach to purify mRKA out of total RNA. Protein could also be reversibly bound to the surface Triaminopropylsilane deposition. Oxidized surfaces were transformed using Ihe hydrolysis products of trimethoxysilylpropyldiethylenetriaminc to afford functional surfaces bearing surface-pendent amino groups. ATR infrared spectroscopy revealed that the network formed by triaminopropylsilyl moieties described a thin coating upon the surface. Ninhydrin coiorimctric analyses indicated that the surface amino group loading per unit frontal area had increased by an order of magnitude in comparison to commercially animated surfaces. As in the case of the TEOS tubes, the amino-modified tubes adsorbed protein reversibly. The amino moieties were subsequently transformed with glutaraldehyde solutions to afford surface-bound aldehyde functional groups. This time, immobilization studies using fluorescent albumin indicated that protein retention was remarkably resistant to washings with high salt, low salt and detergent solutions. In comparison to the aldehyde surfaces, native surfaces did not retain protein to any significant degree, and oxidized. TEOS, and triaminopropylsilylatcd surfaces showed merit in applications based upon a reversible association. Protein binding and retention was markedly influenced by mesoscale topology in the absence of covalent surfaceprotein interactions

    The fate of colors in the 20th - 21st centuries: preserving the organic colorants in plastic artifacts

    Get PDF
    Objectos modernos e contemporâneos feitos de plástico são amplamente encontrados no património cultural. Presentemente, a sua preservação levanta questões críticas aos conservadores e cientistas uma vez que estes objectos podem facilmente sofrer degradação num curto espaço de tempo. Um dos fenómenos que pode alterar significativamente a aparência de objectos em plástico é a alteração de cor (descoloração). De um modo geral, a descoloração é habitualmente associada à degradação dos polímeros, contudo, os pigmentos, que são parte integrante das formulações do plástico, também podem desvanecer devido à exposição à luz. A identificação de objetos de plástico com pigmentos sensíveis à luz é um exercício bastante exigente devido à sensibilidade dos mesmos a alterações na cor. A caracterização dos corantes nos plásticos é normalmente realizada através de amostragem, métodos de extração e testagem destrutiva. Como alternativa, esta tese apresenta uma abordagem inovadora e multi- analítica baseada em espectroscopias que foi desenvolvida para a identificação in situ dos pigmentos em plásticos históricos. Esta metodologia compreendeu a utilização de microscopia ótica (MO), microespectrometria por fluorescência de raios X dispersiva de energias (μ-EDXRF), espectroscopia UV-Vis-NIR de reflectância, fotoluminescência (PL) e micro-espectroscopia de Raman (μ-Raman) na análise de obras de arte, objetos industriais e de uso diário, datados de 1950-2000s e pertencentes a coleções Portuguesas. Deste estudo resultou a identificação dos pigmentos comumente presentes na paleta de cor dos coloristas da indústria dos plásticos portuguesa: óxido de ferro (PR 101, α-Fe2O3), molibdato de cromato de chumbo (PR 104, Pb(Cr,Mo,S)O4), vermelho de cádmio (PR 108, Cd(S,Se); PR 113, (Cd,Hg)S), amarelo de cádmio (PY 37, CdS; PY 35; (Cd,Zn)S), branco de titânio (PW 6, TiO2 ambos rutilo e anátase), oxicloreto de bismuto (PW 14, BiOCl) e lacas do pigmento orgânico β-naftol (PR 48, PR 49, PR 53). Adicionalmente, foi também identificado um pigmento fora do comum, o pigmento perlascente plumbonacrite Pb5(CO3)3O(OH)2. Para todos os casos de estudo, μ-Raman foi a ferramenta chave para a caracterização dos pigmentos nos objetos de plástico, aportando dados conclusivos para a identificação dos mesmos. A impressão digital vibracional dos pigmentos orgânicos e inorgânicos foi adquirida com sucesso recorrendo à focagem do laser na superfície das partículas. A aquisição de dados espectrais de pigmentos com concentrações muito baixas (0.1 % a 5%, aproximadamente) à escala micro foi possível através de microscopia confocal, que faz parte do sistema do equipamento de μ-Raman. Adicionalmente, foi também possível obter informação sobre o polímero base (principalmente termoplásticos) e cargas. Os métodos analíticos desenvolvidos neste estudo deverão, em trabalhos futuros, facilitar a obtenção de informação complementar sobre estes objetos de plástico e permitir uma melhor identificação e avaliação do seu estado de conservação. Esta tese foca particularmente objectos de plástico vermelhos visto que estes foram identificados como os mais severamente afetados por alterações de cor. O estado avançado de desvanecimento identificado no pigmento β-naftol PR 53 mostrou a sua fraca estabilidade à luz em formulações de plástico. Esta situação, junto com as alterações de cor descritas em literatura para o pigmento PR 48 em objetos de plástico, sugere uma sensibilidade dos pigmentos vermelhos da família dos β-naftol ao desvanecimento. O PR 53 e os pigmentos vermelhos da família dos β-naftóis são pigmentos históricos facilmente encontrados em objetos do património cultural. No entanto, o conhecimento acerca da sua estabilidade a longo prazo e resistência à foto-degradação é limitado, especialmente para os casos onde os mesmos se encontram em polímeros, sendo que este conhecimento é essencial para a sua preservação. Neste estudo, a quantificação da foto-estabilidade para uma série de pigmentos vermelhos da família dos β-naftol foi realizada pela primeira vez, através do cálculo do rendimento quântico de fotodegradação (ΦR). Os valores obtidos variaram entre 3x10-6 e 4x10-5, indicativo de uma estabilidade relativamente boa à luz por parte das moléculas. Tendo em consideração que a estabilidade dos pigmentos não se limita exclusivamente ao pigmento em si, mas também à sua interação com o meio envolvente, foram realizados ensaios de envelhecimento por exposição à luz (λ>300 nm) do pigmento em solução, em pó e incorporado em polímeros de modo a avaliar o papel do meio na estabilidade à luz dos pigmentos e as vias pelas quais estes se degradam. Verificou-se que o ligante tem um impacto significativo na estabilidade do pigmento uma vez que se foi detetada uma maior sensibilidade à luz dos pigmentos PR 48 e PR 53 quando incorporados nos plásticos, comparativamente ao ensaio do pigmento em pó. Este novo conhecimento irá contribuir para o desenvolvimento de novas estratégias na conservação dos plásticos com estes pigmentos vermelhos fotossensíveis através da previsão do desvanecimento. Espectrometrias de massa (MS) por cromatografia em fase líquida e gasosa foram utilizadas na caracterização dos principais subprodutos da degradação. Observou-se uma fotodegradação significativa e a formação de compostos ftálicos e ftalatos nos pigmentos em solução e em pó.Modern and contemporary objects made of plastics are widely found in cultural heritage. Today, their preser- vation poses critical issues to conservators and scientists, as they can suffer from extensive degradation in a short time period. Color change (discoloration) is one of the alteration phenomena that can significantly affect their appearance. Discoloration is commonly associated with the degradation of polymers. However, pigments within plastics can also fade due to exposure to light. The identification of objects that contain light-sensitive pigments is demanding because of the sensitivity of plastics to color change. Normally sampling, extraction methods and destructive testing are required for the characterization of colorants in plastics. In this work, an innovative multi-analytical spectroscopic approach for the in situ identification of pigments in historical plastics was developed. Optical microscopy (MO), micro-energy dispersive X-ray fluo- rescence (μ-EDXRF), UV-Vis-NIR reflectance, photoluminescence (PL) and Raman microscopy (μ-Raman), were used for the analysis of artworks, industrial and daily objects dated from 1950s-2000s from Portuguese collections. A common colorists’ palette within the Portuguese plastics industry was identified: iron oxide (PR 101, α-Fe2O3), lead chromate molybdate (PR 104, Pb(Cr,Mo,S)O4), cadmium red (PR 108, Cd(S,Se); PR 113, (Cd,Hg)S) and cadmium yellow (PY 37, CdS; PY 35; (Cd,Zn)S) pigments, titanium whites (PW 6, TiO2 both rutile and anatase), bismuth oxychloride (PW 14, BiOCl) and organic β-naphthol lakes (PR 48, PR 49, PR 53). An exceptional pigment found was the pearlescent plumbonacrite pigment Pb5(CO3)3O(OH)2. In all the case studies, μ-Raman was the key analytical tool for pigment characterization in the plastic objects, providing conclusive data for their identification. The vibrational fingerprint of both inorganic and organic pigments was successfully recorded by focusing the laser beam on particle surfaces. The confocal microscopy system used in μ-Raman enabled the collection of spectral data from low concentrations of pigments (ap- proximately 0.1%-5%) on the micro-scale. In addition to pigments, information on the base polymer (mainly thermoplastics) and fillers was obtained. The analytical methods developed will facilitate the acquisition of complementary data from plastics allowing material identification and condition assessment in the future. This thesis focused on red pigmented plastic artifacts, as they were found to be severely faded among the studied objects. The identification of β-naphthol pigment lake PR 53 as a faded pigment highlighted its poor fastness in plastics, that together with the color change of PR 48 in plastic objects, reported in literature, suggests the particular susceptibility of β-naphthol red lakes to fading. PR 53, and the other β-naphthol reds, are historical pigments widely found in cultural heritage. However, little is known about their photodegradation and stability, especially when they are found in polymer media, and this knowledge is essential for their long- term preservation. For the first time, photodegradation quantum yields (ΦR) were calculated for a series of red pigments based on β-naphthol in order to quantify their photo-stability. ΦR values ranging from 3x10-6 to 4x10-5 were obtained, indicating relatively light-stable molecules. Bearing in mind that pigment fastness is not only related to the pigment itself, but also to its interaction with the confined environment, light-aging experiments (λ>300 nm) were conducted in solution, on powders, and in polymers to assess the role of the medium on the lightfastness of the pigments and their degradation pathways. A significant impact of the binder on their stability was found. Indeed, a higher sensitivity to light of PR 48 and PR 53 pigments, when incorporated in plastics than in powder, was observed. This new knowledge will contribute to the prediction of plastic fading and inform effective preventive conservation strategies for objects containing light- sensitive β-naphthol red pigments. Liquid- and gas-chromatography mass spectrometry (MS) were used for the characterization of the main degradation products. Extensive photodegradation was observed with the formation of phthalic compounds and phthalates in both solution and powder phases

    Development of a novel bioactive glass propelled via air-abrasion to remove orthodontic bonding materials and promote remineralisation of white spot lesions

    Get PDF
    PhDEnamel damage and demineralisation are common complications associated with fixed orthodontic appliances. In particular, the clean-up of adhesive remnants after debonding is a recognised cause of enamel damage. Furthermore, fixed attachments offer retentive areas for accumulation of cariogenic bacteria leading to enamel demineralisation and formation of white spot lesions (WSLs). Bioactive glasses may be used to remove adhesives, preserving the integrity of the enamel surface, while also having the potential to induce enamel remineralisation, although their efficacy in both respects has received little attention. A systematic review evaluating the remineralisation potential of bioactive glasses was first undertaken. No prospective clinical studies were identified; however, a range of in vitro studies with heterogeneous designs were identified, largely providing encouraging results. A series of glasses was prepared with molar compositions similar to 45S5 (SylcTM; proprietary bioactive glass) but with constant fluoride, reduced silica and increased sodium and phosphate contents. These glasses were characterised in several tests and the most promising selected. This was designed with hardness lower than that of enamel and higher than orthodontic adhesives. Its effectiveness in terms of removal of composite- and glass ionomer- based orthodontic adhesives was evaluated against SylcTM and a tungsten carbide (TC) bur. This novel glass was subsequently used for remineralisation of artificially-induced orthodontic WSLs on extracted human teeth. The novel glass propelled via the air-abrasion system selectively removed adhesives without inducing tangible physical enamel damage compared to SylcTM and the conventional TC bur. It also remineralised WSLs with surface roughness and intensity of light backscattering similar to sound enamel. In addition, mineral deposits were detected on remineralised enamel surfaces; these acted as a protective layer on the enamel surface and improved its hardness. This layer was rich in calcium, phosphate, and fluoride; 19F MAS-NMR, confirmed the formation of fluorapatite. This is particularly beneficial since fluorapatite is more chemically stable than hydroxyapatite and has more resistance to acid attack. Hence, a promising bioactive glass has been developed.Iraqi Ministry of Higher Education and Scientific Researc

    TECHNART 2017. Non-destructive and microanalytical techniques in art and cultural heritage. Book of abstracts

    Get PDF
    440 p.TECHNART2017 is the international biannual congress on the application of Analytical Techniques in Art and Cultural Heritage. The aim of this European conference is to provide a scientific forum to present and promote the use of analytical spectroscopic techniques in cultural heritage on a worldwide scale to stimulate contacts and exchange experiences, making a bridge between science and art. This conference builds on the momentum of the previous TECHNART editions of Lisbon, Athens, Berlin, Amsterdam and Catania, offering an outstanding and unique opportunity for exchanging knowledge on leading edge developments. Cultural heritage studies are interpreted in a broad sense, including pigments, stones, metal, glass, ceramics, chemometrics on artwork studies, resins, fibers, forensic applications in art, history, archaeology and conservation science. The meeting is focused in different aspects: - X-ray analysis (XRF, PIXE, XRD, SEM-EDX). - Confocal X-ray microscopy (3D Micro-XRF, 3D Micro-PIXE). - Synchrotron, ion beam and neutron based techniques/instrumentation. - FT-IR and Raman spectroscopy. - UV-Vis and NIR absorption/reflectance and fluorescence. - Laser-based analytical techniques (LIBS, etc.). - Magnetic resonance techniques. - Chromatography (GC, HPLC) and mass spectrometry. - Optical imaging and coherence techniques. - Mobile spectrometry and remote sensing

    Thermal protection properties of aerogel-coated Kevlar woven fabrics

    Get PDF
    This paper investigated the thermal properties of aerogel-coated Kevlar fabrics under both the ambient temperature and high temperature with laser radiation. It is found that the aerogels combined with a Kevlar fabric contribute to a higher thermal insulation value. Under laser radiation with high temperature, the aerogel content plays a vital role on the surface temperature of the fabrics. At laser radiations with pixel time 330 μs, the surface temperatures of the aerogel coated Kevlar fabrics are 400-440°C lower than that of the uncoated fabric. Results also show that the fabric temperature is directly proportional to pixel time. It can be concluded that the Kevlar fabrics coated with silica aerogel provides better thermal protection under high temperature

    Aiding the conservation of two wooden Buddhist sculptures with 3D imaging and spectroscopic techniques

    Get PDF
    The conservation of Buddhist sculptures that were transferred to Europe at some point during their lifetime raises numerous questions: while these objects historically served a religious, devotional purpose, many of them currently belong to museums or private collections, where they are detached from their original context and often adapted to western taste. A scientific study was carried out to address questions from Museo d'Arte Orientale of Turin curators in terms of whether these artifacts might be forgeries or replicas, and how they may have transformed over time. Several analytical techniques were used for materials identification and to study the production technique, ultimately aiming to discriminate the original materials from those added within later interventions

    X-ray fluorescence applied to yellow pigments based on lead, tin and antimony: comparison of laboratory and portable instrumentation

    Get PDF
    X-ray fluorescence is a diagnostic approach particularly suited to be utilized in cultural heritage sector since it falls in the non-destructive and non-invasive analytical tools. However there are big differences between portable and laboratory instrumentation that make difficult to perform a comparison in terms of quality and reliability of the results. The present study is specifically addressed to investigate these differences in respect of the same analytical sample-set. To reach this goal a comparison was thus carried out between portable and bench top devices X-ray fluorescence devices and techniques were used on different type of yellow pigments based on lead, tin and antimony obtained in laboratory, reproducing the instructions described in “old” recipes, that is: i) mortar of lead and tin produced on the basis of the recipe 13 /c V of the “Manuscript of Danzica” and “ Li tre libri dell’arte del Vasaio” by Cipriano Piccolpasso; ii) two types of lead and tin yellow (Pb2SnO4 and PbSnO3) produced starting from the indications of the 272 and 273 recipes of the “Bolognese Manuscript”; iii) lead antimonate (Pb2Sb2O7) obtained by following the instructions of the Piccolpasso’s treatise and those contained on the “Istoria delle pitture in maiolica fatte in Pesaro e ne’ luoghi circonvicini di Giambattista Passeri” and finally iv) lead, tin and antimony yellow (Pb2SnSbO6,5) obtained starting from the information contained in the paper 30 R of “Manuscript of Danzica” [1]. The XRF analysis were performed using a laboratory instrumentation (Bruker M4 Tornado) and a handset analytical device (Assing Surface Monitor). In order to perform a significant statistical comparison among acquired and processed data, all the analyses have been carried out utilizing the same sample, the same acquisition set up and operative conditions. A chemometric approach, based on the utilization of Principal Component Analysis (PCA) and multivariate analytical based tools [2], was utilized in order to verify the spectral differences, and related informative content, among the different produced yellow pigments. The multivariate approach on the results revealed instrumental differences between the two systems and allowed to compare the common characteristics of the set of pigments analyzed

    Degradation of Cd-yellow pigment: an ab initio study of defects and adsorption of oxygen and water on CdS

    Get PDF
    The cadmium yellow paints used in impressionist and modernist paintings in early 1900s are undergoing several deterioration processes, including whitening and discoloration. Relevant e↵ects produced at the surface of modern paintings include the growth of discolored crusts, formed mainly by white globular hydrated cadmium sulfate CdSO4*nH2O and cadmium carbonate (CdCO3 ). In view of the fact that the pigment, cadmium sulfide, was historically synthesized by means of dry and wet processes and that CdCO3 and CdSO4 are reagents for this procedure, their identification alone does not constitute conclusive proof of photo-oxidation. The origins of such chemical and physical alterations are still under debate. Structural defects in CdS, among other possible causes like photo-oxidation processes, may play a role in the degradation process. Their presence in the pigment surface alters the electronic structure of cadmium sulfide by forming acceptor levels in the gap of the semiconductor. Such levels make the surface more reactive in the interaction with external agents (oxygen, water ...). To this end, we present a theoretical study of points defects, namely Cd- and S- vacancies, in the structural wurtzite structure (bulk) and [10¯10] CdS surface. In order to understand, at atomic level, the oxidation and hydration mechanisms of these whitish globules, we present the early stages of the interaction between the hexagonal clean and defective [10¯10] surface of CdS and O2 and H2O molecules to simulate the combined e↵ects of exposure to air and humidity. The geometrical and electronic structures as well as the vacancy formation and adsorption energies are determined with the use of a first principles method. All the calculations are performed within the framework of the Density Functional Theory (DFT) in the Generalized Gradient Approximation (GGA-PBE) with the use of ultrasoft pseudopotentials. Despite the standard DFT-GGA ensures a correct order of electronic states, the G0W0 calculations are strongly required to attribute an accurate position of the trap level. Considering the possibility to investigate in a broader spectral range, such theoretical method would be helpful in the interpretation of experimental evidences on fluorescence emissions produced from by yellow altered. This thesis highlights the key role that first-principles methods can play in the application of materials science to art conservation
    corecore