Paraloid B72 Research Articles

Protective features, durability and biodegration study of acrylic and methacrylic fluorinated polymer coatings for marble protection

Abstract In the present paper, a new fluorine based methacrylic monomer, 1H,1H,2H,2H-Perfluoro-octyl-methacrylate (POMA), was synthesized via esterification reaction from methacryloyl chloride and 1H,1H,2H,2H-Perfluoro-1-octanol. Furthermore, POMA was used to prepare with methyl methacrylate (MMA) via free radical polymerization a novel fluorinated methacrylic polymer (MMA_POMA), in order to overcome the well-known technical problems related to the use of acrylic monomer-based commercial protectives, such as Paraloid B72 ® . Indeed, in Paraloid B72 ® −obtainable from the copolymerization reaction of ethyl methacrylate (EMA) and methyl acrylate (MA)- the presence of an acrylic hydrogen atom in alpha to the carbonyl group can start photo-chemical degradation reactions that are able to promote fungi attack and proliferation. The properties of MMA_POMA and the two references synthesized, EMA_MA and EMA_MA_POMA −in terms of macromolecular structure, molecular weights, thermal features and water repellency- were determined; furthermore, the long-term behavior of these polymeric protective agents was estimated by means of accelerated aging tests exploiting UV radiations. Their behavior over time was checked via Size Exclusion Chromatography (SEC), Fourier Transform Infrared (FT-IR) spectroscopy and biodegradation assay. Lastly, MMA_POMA resin was applied on two marble substrates −Calcite and Dolomite- and its wetting properties were successfully assessed and compared to the same features displayed by the reference polymers. This work demonstrates that a polymer protective prepared starting from methacrylic and fluorinated monomers, i.e. MMA and POMA, is an efficient way to obtain resins with satisfactory water repellent properties and enhanced durability than acrylic based polymers without the use of any photo stabilizer additive.

Protection of Limestone Coated with Different Polymeric Materials

The uniaxial compressive strength is an important parameter in selecting and design of rock and brittles structure. Protection of ancient monuments or historic structure has a great intense in material science point of view. Limestone is commonly rock material which has a great sense in historical buildings and temples. The strength of this material may be influenced by natural weathering like moisture, rains and varying temperature. Samples of ancient limestone rock are coated with Paraloid B44, Paraloid B72, ethyl silicate and Wacker OH100. The results concluded that both Wacker OH100 and Paraloid B44 coating material have more efficient and give considerable protection when the sample is immersed in salinity water for a week. The compressive strength of limestone decreases due to water action. Water absorption, porosity, and rock density are enhanced with the coating process.

Blue-Biotechnology and Biocleaning of Historic­-Artistic Artifacts

The search for novel cleaning strategies in restoration procedures is growing fast. One innovation/innovative breakthrough in cleaning procedures is represented by the use of enzymes. This is due to the fact that their action is highly selective and they effectively remove undesired layers without adversely affecting the constituent or surrounding materials of the artifact undergoing treatment. In this study we present the results of tests performed by a new set of enzymatic proteins, esterases, extracted from marine organisms, for the bio-removal of Paraloid B72.

The effect of TiO2 component on the properties of acrylic and urea-aldehyde resins under accelerated ageing conditions

Abstract Synthetic resins were introduced in paintings conservation during the 1930s, as an alternative to natural resins, due to their superior resistance to degradation. Their composition usually includes a small amount of additives, such as titanium dioxide. The objective of this work is to study the effect of TiO2 additive on the durability of Paraloid B72 (acrylic resin) and Laropal A81 (urea-aldehyde condensation polymer), both used in art conservation, against photochemical degradation. A methodology involving separating particulate TiO2 from the organic fraction of the resins has been applied, followed by accelerated ageing of the resins in their commercial (C) and modified (M, i.e. after TiO2 removal) has been implemented. The morphological characteristics of resin films were examined through scanning electron microscopy (SEM). Chemical changes, colour properties and photo-chemical stability of the resins were studied with FTIR, UV-Vis absorption spectroscopy and spectro-colorimetry. The results showed a considerably different behaviour between the C and M states of both materials. In particular, C-Paraloid B72 collapses after prolonged irradiation, but within a certain time frame it appears to be relatively stable; on the other hand, C-Laropal A81 is considerably destabilized in comparison to its M state. It can be suggested that TiO2 acts as a UV-blocker for the underlying pigment layers, at the expense of resins’ stability.

Probing the Cleaning of Polymeric Coatings by Nanostructured Fluids: A QCM-D Study.

Complex fluids composed of water, an organic solvent, and a surfactant have been recently employed as cleaning systems to remove hydrophobic materials, such as polymeric coatings, from solid surfaces. The simultaneous presence of surfactants and an organic solvent with good affinity for the polymer was proven necessary for the polymer's removal, but the comprehension of the cleaning mechanism is poorly understood. In this Article, we investigated the mechanism of removal, highlighting the specific role of each component in the interaction with the polymer film. In particular, the results from quartz crystal microbalance with dissipation monitoring (QCM-D) were compared with those obtained by using confocal microscopy to follow in situ the effect of a nanostructured fluid, i.e., a ternary formulation containing water, 2-butanone (MEK) as a good solvent for the polymer, and a nonionic surfactant (C9-11 ethoxylated alcohol, BR) on acrylic copolymer films (Paraloid B72). The results indicate a two-step process: (i) the penetration of the good solvent across the film causes the swelling of the polymer, the weakening of polymer-polymer interactions, and an increase of molecular mobility, followed by (ii) the slow adsorption of amphiphilic aggregates promoting the film detachment from the solid substrate. A different behavior is observed in the presence of similar formulations containing an anionic surfactant (sodium dodecyl sulfate, SDS), where the adsorption of SDS micelles on the surface of the polymeric film hinders solvent access into the polymer layer, rather than promoting its detachment from the solid substrate.

Evaluation of protective properties of acrylate varnishes used for conservation of historical metal artefacts

Abstract Acrylate varnishes are due to their suitable properties frequently used in restoration and preservation on variety of historical objects and materials. Common practice of their application involves using as an adhesive agents, consolidants and protective coatings. The purpose of protective coatings especially on metal artefacts is to reduce access of pollutants to the surface of the artefact. In this paper, coatings prepared from two acrylate polymers Paraloid B72 and Paraloid B48N are compared in terms of permeability for water and level of protective properties against air pollutants. For this purpose, electrochemical impedance spectroscopy and resistometric method were chosen for analysis of the coatings. Obtained results show lower permeability for water in case of Paraloid B72. However, same coating provided lower protection against air pollutants than Paraloid B48N coating.

Discoloration of Historic Wood after the Application of Nanotextiles

The article addresses the discoloration of historic wood after application of nanotextiles. The nanofiber fabrics used for experimental testing were made of the PVB polymer and the Paraloid B72 acrylic resin. For the verification of the possibility to increase the biocidal efficiency of historic wood have also been made nanotextile with dopants Ag ant TiO2. Discoloration of historic wood after the application of selected nanotextiles were tested on the wood samples, which were removed from historic building Hájčí Dvůr, Praha 5. The article was written with support from the research project NAKI DF12P01OVV37: Progressive Non-Invasive Methods for the Stabilization, Conservation and Strengthening of Historic Structures and their Parts with Fiber – and Nanofiber – based Composite Materials.

Consolidation of a sepiolite-rich sandstone—learning from failure

Attempts to consolidate an armorial panel from Elgin Cathedral with a solution of Paraloid B72 in acetone had an unexpected adverse reaction and led to irreversible surface damage. XRD analysis identified unusual near-surface pockets of sepiolite below the affected areas. While not identified as expansive by XRD, sepiolite powder visibly increased in volume when submerged in acetone. Solvents with a lower polarity index were investigated and the addition of toluene did not appear to impact on sepiolite powder. Following successful treatment tests, Paraloid B72 solutions in toluene were used to consolidate and restore the carved surface of the armorial panel. Unusual treatment failures, as in this case, present learning opportunities and sharing such experiences honestly may inform colleagues in similar situations.

The conservation of a 19th Century giant deer display skeleton for public exhibition

Following a mishap, a 19th Century mounted giant deer was subjected to a detailed osteological assessment and conservation treatment which required both structural repair and the extensive modeling of broken and missing skeletal components. The historic mounting system and plinth were largely intact and structurally safe for the skeleton and so these could be retained along with any historic restorations deemed sound and non-damaging. The original skull suffered irreparable damage and both antlers were detached from the specimen. A replacement skull was acquired but it was necessary to attach the original antlers to the new skull in a manner both structurally sound and aesthetically accurate enough for the deer to be placed back on open display. After testing commonly used conservation-grade filler materials suitable for fabricating missing skeletal components, losses to the vertebra and the ribcage were re-built using epoxy resin bulked to putty consistency with phenolic microballoons and applied over barrier layers of Paraloid B72 and Japanese tissue. All losses were in-painted with earth pigments in Paraloid B72 before rearticulation. The unique role of this specimen determined the conservation approaches adopted and included a balanced consideration of conservation ethical concerns, client expectations, future structural stability, aesthetic impact and the limitations of the future display location.

Biological performance, water absorption, and swelling of wood treated with nano-particles combined with the application of Paraloid B72®

We evaluated fungal decay and mold resistance, leaching, and water absorption of nano-compounds and Paraloid B72® (PB72) in treated wood specimens to develop new methods of consolidation by combining nano-particles and consolidants. Scots pine wood specimens were treated with dispersions of nano-CuO, nano-ZnO, nano-B2O3, nano-TiO2, and nano-CeO2. PB72 treatments of nano-particle-treated wood specimens were then carried out by either vacuum or immersion for 24 h. Previously, decayed wood specimens were also consolidated with the nano-compounds and PB72. PB72 treatments reduced element release from treated wood specimens. Nearly all nano-compounds + PB72 treatments increased the biological performance of treated wood specimens against decay fungi tested. PB72-only treated wood specimens had the highest weight losses in decay tests. No improvements were obtained in mold resistance tests when the nano-compounds and PB72 were combined. In nano-compound-only treatments, unleached specimens showed slightly lower water absorption values compared to untreated control specimens. Incorporation of PB72 into nano-compound-treated wood specimens resulted in considerably lower water absorption and volumetric swell. In previously decayed specimens treated with the nano-compounds and PB72 solution, water absorption after 2-h immersion declined compared to control specimens.

Preparation and artificial ageing tests in stone conservation of fluorosilicone vinyl acetate/acrylic/epoxy polymers

AbstractIn this work, a series of fluorosilicone vinyl acetate/acrylic/epoxy (FVAE) polymers for protection of stone relics were prepared with different content of hexafluorobutyl methacrylate (HFBMA) by the seed emulsion polymerization process. Properties and structure of FVAE materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and transmission electron microscopy (TEM). Viscosity, particle size, surface tension, gel content, adhesion and surface hardness of polymer materials were also determined. Surface morphology of the stone sample was observed by scanning electron microscopy (SEM). Compared with a commercial copolymer, ethyl methacrylate/methyl acrylate (EM/MA, Paraloid B72), protection ability of the prepared FVAE polymer was investigated using artificial ageing tests such as the freeze-thaw aging test, acid aging test and the soluble salts aging test. It was found that the FVAE polymers prepared can effectively prevent corrosion caused by H

Amphiphile-based nanofludis for the removal of styrene/acrylate coatings: Cleaning of stucco decoration in the Uaxactun archeological site (Guatemala)

Abstract The conservation of mural paintings, stone and stucco elements, which are present in archaeological sites, may involve the removal of synthetic polymers used in the past as consolidants or protective agents. Unfortunately, traditional cleaning methods do not provide satisfactory results in this case. Micelles and microemulsions are the most effective alternative to the use of traditional organic solvents. In this contribution, we report the results of laboratory and in situ cleaning tests on specimens and works of art, whose surface was coated with Sokrat ® (also known as Axylat ® ). Polymer removal was performed with a microemulsion that was previously used to efficiently remove Paraloid B72 ® from inorganic porous substrates. The good results obtained in laboratory were confirmed by the cleaning test on the stucco decorations in the Uaxactun archaeological site (Guatemala). Finally, SAXS characterization of the nanofluid before and after the interaction with Sokrat ® showed that micelles reorganize and get smaller due to the solvents’ migration from the aggregates to the polymer. This behavior is in agreement with previous results obtained on this and other microemulsions interacting with different polymeric films.

Innovative microcrystalline cellulose composites as lining adhesives for canvas

Thin adhesive composite films were prepared by melt‐compounding and compression molding of a thermoplastic resin (Paraloid® B72) widely used for art protection and restoration with a microcrystalline cellulose powder (MCC). To simulate an oil painting restoration work, MCC‐based composites were applied as lining adhesives on two kinds of canvases (English linen and woven polyester). Interestingly, single–lap shear tests both in quasi‐static and creep conditions showed a remarkable stabilizing effect provided by MCC addition. Post‐mortem microstructural analysis of the overlap adhesive area proved how MCC introduction did not change the fracture behavior of the bonded joints. The visual assessment of transparency and color measurements evidenced a chromatic variation of MCC‐based films with a filler amount of 30 wt%, while, UV‐vis analysis showed a decrease of relative transmittance in proportion to the MCC content. Additionally, rheological tests highlighted a viscosity increase for Paraloid B72 in both dry and wet conditions (T = 23°C and RH = of 55%) as the MCC content increases. POLYM. ENG. SCI., 55:1349–1354, 2015. © 2015 Society of Plastics Engineers

CONSERVATION OF PHOTODEGRADED ASIAN LACQUER SURFACES: FOUR CASE STUDIES

Exposure to light combined with fluctuations in relative humidity causes the formation of microcracks in the surface of Asian lacquer, which is associated with loss of gloss. Increasing severity of microcracks results in incremental loss of surface and decoration. This paper presents four case studies of the conservation of photodegraded Asian lacquer surfaces that required balancing ethical considerations, current knowledge of the objects, their condition, intended use, and long-term preservation. These treatments encompassed the use of Paraloid B72 and the lacquer-based treatments urushi-gatame and suri urushi. In each case a unique set of challenges was resolved using a treatment plan customized for each object.

Properties of Polymer-Composite Used as Fills of Asian Lacquerware: Issues on Restoration Processes of Lacquered Objects from Cultural Heritage

One of the common problems encountered in lacquerware issued from cultural heritage is the appearance of lifting areas and some losses of material. Composite systems made of commercial polymer and different fills were tested as filling agents for the cracking, splitting, and losses compensation of Asian lacquer. For that purpose, the stability of traditional and modern commercially available materials usually used in the restoration practice of historical lacquerware was assessed. Their thermomechanical and chemical properties and surface state were evaluated by a set of techniques (TGA, DMA, mechanical test, contact angle value, and microtopography). There is a drastic change of the behavior of the interface between fill and Asian lacquer, dependent on the nature of the composite fillers. So the evaluation of materials and processes for the restoration of Asian lacquer were emphasized. The commercial Paraloid B72 used with glass microspheres as additives appeared to be the most stable of all of the investigated fillers.

Treating friable matte pigments on bark: experimental analysis of four consolidants

AbstractFlaking and friable paint has long been noted as a condition concern of collected ethnographic art and material culture. Over the years, various materials for the consolidation of friable matte pigments have been recommended, from resins to commercial fixatives and varnishes. This article continues the investigation of appropriate consolidants for friable earth pigments specifically from the perspective of Aboriginal Australian bark paintings. Due to the importance of colour and design in communicating significance and provenance in bark paintings, conservation treatments must avoid altering these properties. With this in mind, the experiment described herein compared the efficacy of four consolidants in treating highly friable pigments on simulated test boards. Of the four materials—Paraloid® B72, Klucel® G, Lascaux® Medium for Consolidation and Lascaux JunFunori®—JunFunori and Paraloid B72 were the most effective at improving cohesion and adhesion of the pigments. However, further work is necess...

Effect of the water sorption on the mechanical response of microcrystalline cellulose‐based composites for art protection and restoration

ABSTRACTThermoplastic composites based on a commercial acrylic matrix widely used in the field of art protection and restoration (Paraloid B72) and various concentrations (up to 30 wt %) of microcrystalline cellulose powder (MCC) were prepared by melt‐compounding and compression molding. The mechanical behavior of the resulting materials conditioned at a temperature of 23°C and a relative humidity level of 55% was compared to that of the corresponding dried materials. Even though the moisture absorption of the filler was lower than the neat matrix, the maximum moisture content increased with the MCC amount, probably due to the preferential water diffusion path through the microvoids and/or the filler‐matrix interface. Although the increase of moisture content for filled samples, DMTA analysis evidenced a stabilization upon MCC introduction, with an increase of the storage modulus and a decrease of the thermal expansion coefficient proportional to the filler loading. A similar trend was displayed by the corresponding dried materials. The tensile elastic modulus and the ultimate properties such as the stress at break and the tensile energy to break (TEB) of conditioned samples increased proportionally to the filler amount. On the contrary, the failure properties of dried composites were negatively affected by the presence of the microcellulose. It is worthwhile to report that a significant improvement of the creep stability was induced by MCC introduction both for dried and conditioned samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40741.

A methodology to select bacteria able to remove synthetic polymers

Abstract Synthetic polymers have often been used for the protection and consolidation of cultural heritage. Although it was generally thought that synthetic polymers were not susceptible to deterioration, there are now many papers in the scientific literature demonstrating the opposite. The degradation of synthetic polymers can be due to chemical, physical and biological factors. At present, the traditional way for removing a degraded synthetic polymer is the use of mixtures of solvents that pose some health risks. This work proposes a method to select bacteria able to remove synthetic polymers from cultural heritage surfaces. The ability of five bacteria to attack Paraloid B72, the most commonly used polymer in conservation treatments, was evaluated by optical and scanning electron microscopy observations, weight loss measurements, Fourier transform infrared spectroscopy and differential scanning calorimetric analysis. Although none of the bacteria were able to attack Paraloid B72, the methodology developed can be applied to select other bacteria with this ability. Therefore the results offer insightful guidance to a better design of bioremoval experiments of synthetic resins used in conservation.

Thermo-mechanical properties of innovative microcrystalline cellulose filled composites for art protection and restoration

Microcrystalline cellulose (MCC) powder was selected as a natural reinforcement for a commercial acrylic adhesive widely used in the field of art protection and restoration (Paraloid B72). In particular, various amounts (from 5 to 30 wt%) of MCC were melt compounded with Paraloid B72 to prepare new thermoplastic polymer composites for the cultural heritage conservation field. Scanning electron microscopy showed that MCC flakes are uniformly dispersed within the matrix at all the tested compositions, without preferential orientation. Thermogravimetric analysis evidenced an increase of thermal stability due to the MCC introduction, even at low filler amounts, while DSC measurements demonstrated that the glass transition temperature progressively increases with the MCC content. Interestingly, DMTA analysis revealed a stabilizing effect on the material produced by microcellulose addition, with an increase of the storage modulus and a decrease of the thermal expansion coefficient, in proportion to the filler loading. Moreover, MCC addition determined an increase of the elastic modulus and creep stability with respect to the neat resin, and an enhancement of fracture toughness (K IC).

Development of nanocomposites for conservation of artistic stones

Properties of consolidant and protective materials modified with nanoparticles were analysed in this study following their application onto marble samples. For this purpose, different solutions of an acrylic resin with dispersed SiO2 and TiO2 nanoparticles were prepared. The relative durability of Paraloid B72, an acrylic resin used as consolidant and modified by nanoparticles, was evaluated comparatively by means of diverse diagnostic techniques, namely, scanning electron microscopy, laser-induced fluorescence, ultrasonic sound, colorimetry, total immersion water absorption and contact angle. The results demonstrate that nanoparticles enhance the effectiveness of consolidant and protective material because they induce substantial changes of surface morphology of the coating layer.