RO134390A0 - Process for preparing nanocomposite films meant to protect architectural lithic components of cultural heritage - Google Patents

Abstract

The invention relates to a process for preparing nanocomposite films to be used for protecting architectural components of the national heritage. According to the invention, the process consists in preparing a suspension of nanoparticles of magnesium oxide 0.5% in a solution of hydrophobically modified sodium polyacrylate 0.1% and applying a suspension layer, on surfaces of different roughness such as glass, tiles, ceramics, sandstone, mortar, by usual methods, to result in a nanocomposite film having antimicrobial activity and, in the absence of light, a water absorption by capillarity reduced by 10%, photocatalytic properties and colour and appearance stability.

Description

Process for obtaining nanocomposite films designed to protect the lithic architectural components of the cultural heritage.

The present invention relates to a process for obtaining thin films / nanocomposite films from a mixture of oxide nanoparticles (MgO) and polymers in aqueous solution (NaPAC16- hydrophobically modified sodium polyacrylate), for use in protecting the architectural components of cultural heritage.

Constant exposure to the combined activity of nature and urban pollution causes more damage to building materials: water, air pollution, soluble salts, biodegradation are the main causes of degradation, and the literature includes many articles on investigating their mechanisms of action.

The protection of architectural elements in the field of cultural heritage is a complex activity due to the difficulty of meeting the required criteria. An ideal coating should be effective, resistant, durable, transparent, easy to apply, non-toxic and removable. Moreover, the protective coating must guarantee a high level of hydrophobicity, given that moisture and rainwater are the main causes of degradation mechanisms. At the same time, the coating must allow the stone to perspire to avoid that the water already present in the substrate can cause further degradation. [C. V. Horie, Materials for Conservation: Organic Consolidants, Adhesives and Coatings, Routledge, 2010]

Water contributes substantially to the degradation of monuments by freezing and thawing and also because it is a carrier of pollutants and salt solutions. Waterproofing can be achieved by applying a thin, hydrophobic, organic film. The use of simple polymer coatings for monument protection is still under debate due to the unwanted side effects developed with aging.

Several strategies related to the protection of monuments have been proposed: organic layers, inorganic particles and composite materials.

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Both organic and inorganic agents, including synthetic polymers, were used to protect and preserve historical monuments. Treatments performed with organic materials show low durability, drastic change in the structural properties of the stone and poor physico-chemical compatibility with the substrate. Inorganic products appear to have certain advantages, such as good durability and greater physico-chemical compatibility with stone components, but, on the other hand, they usually provide insufficient penetration and therefore an effect. weak consolidation. [M. Licchelli, M. Malagodi, M. Weththimuni, C. Zanchi, Anti-graffitinanocomposite materials for surface protection of a very porous stone, AppI.Phys. A. 116 (2014) 15251539]

In the last 40 years, organic materials have been used mainly to strengthen stone structures and painted walls: synthetic acrylic and vinyl polymers have been used as consolidators for frescoes, as well as organosilicone compounds. Examples include a mixture of polytetrafluoroethylene in the form of an aqueous dispersion, an emulsion or a microemulsion of perfluoropolyether applied to the surface of said materials or articles CA2005749A1 [Giovanni Moggi, Daria Lenti, Desiderata Ingoglia, Process for protecting stony materials, marble, tiles and cement from atmospheric agents and pollutants], application of amorphous fluoropolymer compositions to stone to protect stone from the harmful effects of water and pollution US20030211332 [William Tuminello, Robert Wheland, Method for protection of stone with substantially amorphous fluoropolymers]

Inorganic consolidants have the great advantage of compatibility with the constituent materials of the work of art. The method was initially based on the dispersion of slaked lime in short-chain aliphatic alcohols (micron calcium hydroxide particles) and was later improved by reducing the average size of the consolidation particles to the submicrometric scale to obtain a deeper penetration of the dispersion. , better stability and to avoid the formation of white films on the treated surface. The average size of the consolidation particles is critical for their application on porous materials, especially when the matrix has low porosity: in recent years, these micron and submicron particles of calcium hydroxide have been used successfully by 2019 00350

10/06/2019 for the consolidation of murals, where the relatively high porosity of the mortar allowed the penetration of large particles.

Numerous investigations have aimed to improve strategies based on organic compounds by adding inorganic nanoparticles [Esposito Corcione, C .; Manno, R .; Frigione, M. Sunlight curable boehmite / siloxane-modified mathacrlylic nano composites: An innovative solution for the protection of carbonate stone. Prog. Org. Coat. 2016, 97, 222-232. / Esposito Corcione, C .; Manno, R .; Frigione, M. Novei hydrophobic free solvent UV-cured hybrid organic-inorganic mathacrylic-based coatings for porous stones. Prog. Org. Coat. 2014, 77, 803-812.] [Kapridaki, C .; Maravelaki-Kalaitzaki, P. TiO2-SiO2-PDMS nano-composite hydrophobic coating with self-cleaning properties for marble protection. Prog. Org. Coat. 2013, 76, 400-410.] [Graziani, G .; Sassoni, E .; Franzoni, E .; Scherer, GW Hydroxyapatite coatings for marble protection: Optimization of calcite covering and acid resistance. Appl. Surf. Sci. 2016, 368, 241-257. /. Manodius, PN; Karapanagiotis, I. Modification of the wettability of polymer surfaces using nanoparticles. Prog. Org. Coat. 2014, 77, 331-338. / Munafo, P .; Goffredo, GB; Quagliarini, E. TiO2-based nanocoatings for preserving architectural stone surfaces: An overview. Constr. Build. Mater. 2015, 84, 201-218.] For increasing hydrophobicity or providing surfaces with self-cleaning properties [Kapridaki, C .; Maravelaki-Kalaitzaki, P. TiOa-SiOz-PDMS nano-composite hydrophobic coating with self-cleaning properties for marble protection. Prog. Org. Coat. 2013, 76, 400-410.] [Munafo, P .; Goffredo, GB; Quagliarini, E. TiO ₂ -based nanocoatings for preserving architectural stone surfaces: An overview. Constr. Build. Mater. 2015, 84, 201-218./. Quagliarini, E .; Bondioli, F .; Goffredo, GB; Licciulli, A .; Munafo, P. Self-cleaning materials on architectural heritage: Compatibility of photo-induced hydrophilicity of T1O2 coatings on stone surfaces. J. Cult. Heritage 2013, 14, 1-7./ Colangiuli, D .; Calia, A .; Bianco, N. Novei multifunctional coatings with photocatalytic and hydrophobic properties for the preservation of stone building heritage. Constr. Build. Mater. 2015, 93, 189-196.] And 2019 00350

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Detailed description of the invention

Precursor materials

MgO - semiconductor nanostructured materials are an effective tool for controlling biological disintegrations because they have great advantages (the ratio of surface area to large volume and small particle size). Among these nanomaterials, titanium dioxide has attracted special attention in the development of antibacterial and antifungal coatings [La Russa, M.F .; Macchia, A .; Ruffolo, S.A .; De Leo, F .; Barberio, M .; Barone, P .; Crisci, G.M .; Urzi, C. Testing the Antibacterial Activity of Doped TiO2 for Preventing Biodeterioration of Cultural Heritage Building Materials. Int. Biodeter. Biodegradable. 2014, 96, 87-96, DOI: 10.10167j.ibiod.2014.10.002 / Munafo, P .; Goffredo, G.B .; Quagliriani, E. TiO2-Based Nanocoatings for Preserving Architectural Stone Surfaces: an OverView. Constr. Build. Mater. 2015, 84, 201-218, DOI:

10.1016 / j.conbuildmat.2015.02.083]. The main disadvantage of this material, however, is the presence of light to be efficient, which restricts their application field./ Morlando, A .; Cardillo, D .; Devers, T .; Konstantinov, K. Titanium Doped Tin Dioxide as Potential UV Filter with Low Photocatalytic Activity for Sunscreen Products. Mater. Lett. 2016, 171, 289-292. DOI: 10.1016 / j.matlet.2016.02.094]

Magnesium oxide is of particular interest because, in addition to being a cheap and environmentally friendly material (bio-safe and bio-compatible), it has antimicrobial activity and in the absence of light, due to high chemical activity on the surface [Salehifar, N .; Zarghami, Z .; Ramezani, M. A Facile, Novei and Low-Temperature Synthesis of MgO Nanorods Via Thermal Decomposition using New Starting Reagent and its Photocalytic Activity Evaluation. Mater. Lett. 2016, 167, 226-229. DOI: 10.1016 / j.matlet.2O16.01.015 / Zhang, W .; Tay, H.L .; Lim, S.S .; Wang, Y .; Zhong, Z .; Xu, R. Supported Cobalt Oxide on MgO: Highly Efficient Catalysts for Degradation of Organic Dyes in Dilute Solutions. Appl. Catal. B. 2010, 65, 93-99] in addition, oxide or metal-doped MgO nanoparticles can be an excellent photocatalyst for the degradation of organic pollutants due to their high photosensitivity.

Hydrophobically modified sodium polyacrylate. Hydrophobically modified sodium polyacrylates (NaPACns) are amphiphilic macromolecular compounds with a hydrophilic structure on which hydrophobic groups are grafted.This leads to the obtaining of unique materials, which has 2019 00350

10/06/2019 are useful in a wide variety of applications. The specific properties of NaPACn are determined by electrostatic interactions (repulsion and attraction) and hydrophobic interaction. Therefore, nonpolar groups remove water molecules and tend to accumulate in the surface layer of the aqueous solution, while the hydrophilic chain interacts with water [F. Petit-Agnely, I. Iliopoulos, R. Zana, Hydrophobically modified sodium polyacrylates in aqueous Solutions: Association mechanism and characterization of the aggregates by fluorescence probing, Langmuir 16 (2000) 9921-9927./ Yu.A. Shashkina, Yu.D. Zaroslov, V.A. Smirnov, O.E. Philippova, A.R. Khokhlov, T.A. Pryakhina, N.A. Churochkina, Hydrophobic aggregation in aqueous Solutions of hydrophobically modified polyacrylamide in the vicinity of overlap concentration, Polymer 44 (2003) 2289-2293].

Depending on the concentration, hydrophobic chains tend to self-associate through intramolecular (low concentration) and intermolecular (high concentrations) hydrophobic attractions and form hydrophobic microdomains. The study of these materials is justified by the various fields in which they are used. NaPACn have special properties, such as the spectacular increase in viscosity and elasticity, which leads to gelling [L. Aricov, A. Băran, E.L. Simion, LC. Gîfu, D.F. Anghel, V. Jerca, M. Vuluga, New insights into the self-assembling of some hydrophobically modified polyacrylates in aqueous solution, Colloid Polym. Sci., 294 (2016) 667-679./L. Aricov, H. Petkova, D. Arabadzhieva, A. lovescu, E. Mileva, K. Khristov, G. Stingă, C.F. Mihailescu, D.F. Anghel, R. Todorov, Aqueous Solutions of associative poly (acrylates): Bulk and interfacial properties. Colloids and Surfaces A: Physicochemical and Engineering Aspects 505 (2016) 138-149]. NaPACn exhibits host properties of hydrophobic compounds in the absence or presence of surfactants [L. Aricov, A. Băran, G. Stingă, E.L. Simion, LC. Gîfu, D.F. Anghel, V. Rădițoiu, Formation and hosting properties of polyacrylate-surfactant complexes, Colloid Polym. Sci., 295 (2017) 1017-1038]. They can also be used in the field of viscoelastic foams [L. Aricov, A. Băran, G. Stîngă, E.L. Simion, LC. Gîfip DJL Anghel, V. Rădițoiu, Formation and hosting properties of polyacrylate-surfactant complexes, Colloid Polym. Sci., 295 (2017) 1017-1038], to build protective films with water insulation properties [LC. Gîfu, M.E. Maxim, A. lovescu, E.L. Simion, L. Aricov, M. Anastasescu, C. Munteanu, D.F. Anghel, Surface a 2019 00350

10/06/2019 hydrophobization by electrostatic deposition of hydrophobically modified poly (acrylates) and their complexes with surfactants, Appl. Surface Sci., 371 (2016) 519-529], as long-term hydrophobic coatings [I.C. Gîfu, M.E. Maxim, A. lovescu, L. Aricov, E.L. Simion, A.R. Leonties ^ M. Anastasescu, C. Munteanu, D.F. Anghel, Natural aging of multilayer films containing hydrophobically modified poly (acrylate) s or their complexes with surfactants, Appl. Surface Sci., 412 (2017) 489-496] and in antimicrobial surface coatings [I.C. Gîfu, M.E.Maxim, L.O. Cinteza, M. Popa, L. Aricov, A.R. Leontieș M. Anastasescu D.F. Anghel, R. lanchis ,, C.M. Ninciuleanu, E. Alexandrescu, S.G. Burlacu, C. Nistor, C. Petcu, Antimicrobial activities of hydrophobically modified poly (acrylate) films and their complexes with different chain length cationic surfactants, Coatings 9-4 (2019) 244],

The detailed description of the preparation of the two main components of the nano-composite, the MgO and NaPACn nanoparticles, is presented in the examples.

We mention here some properties of MgO obtained by the sol-gel method. The white MgO powder consists of periclase, identified by X-ray diffraction analysis (XRD ICD file no. 01-071-1176 having cell parameters a = b = c = 4.2172 (7) Â, a = β = γ = 90 °), has a specific surface area of 72,2 m2 / g and an average pore size of 33,1 nm (determined by the BET method) and has needle-like shapes (SEM) and a bandwidth of 4,7 eV .

NaPACie - sodium salt of polyacrylic acid modified hydrophobically with hexildecyl amine (fatty amine with linear structure) by an amidation reaction using as precursor polyacrylic acid (PAA, M = 150 kDa, Wako Chemicals). PAA modification was performed by reacting the amine with the carboxyl groups of the present precursor of DCC, Ν, Ν'-dicyclohexylcarbodiimide (Sigma Aldrich, 99% purity) using 1-methyl-2pyrrolidone (Sigma Aldrich, 99% purity) as solvent at room temperature. of 60 ° C. The recovery of the synthesized polymer was done by neutralizing and precipitating it in 40% aqueous sodium hydroxide solution (NaOH, Chimopar pa). Subsequently, the hydrophobic modified polymer was purified by dialysis and recovered by lyophilization. The theoretical degree of grafting was 3% (moles). All precursors used for the synthesis of 2019 00350

10/06/2019 NaPACie polymer were used in the condition in which they were purchased, without being purified.

To prove the performance of the nanocomposite obtained for the protection of lithic architectural elements, the following determinations and tests were made: 1. Determination of the contact angle to demonstrate the hydrophobicity of the film, 2. Microbial activity, 3. Capillarity, 4. Colorimetric tests and 5. Photocatalytic activity.

1. Determination of the contact angle

The Drop Shape Analysis System model DSA1 (FM40 Easy Drop) from KRLISS GMbH was used to measure the contact angle of deionized water. A stainless steel needle with an outer diameter of 0.5 mm was used. The volume of the water drop was 3 pl_. All measurements were performed statically at room temperature. The contact angle was determined geometrically by drawing a tangent from the point of contact to the liquid-vapor interface in the droplet profile.

The results are presented in table 1 in the case of depositing a layer of nanocomposite film on a glass support. Thus, for the composite material deposited on the glass, obtained from the dispersion of MgO nanoparticles (0.5%) in the NaPAC16 solution (0.1%), a significant increase of the contact angle values is observed - an average value of 96.41 ° - which demonstrates entering the field of hydrophobicity. Comparatively, the results obtained in the same processing conditions and the same T1O2-based composite films are presented. In the latter case, the average value obtained was 78.50 °, a value that places the material towards the lower limit of hydrophobicity.

Table 1. Contact angle values for polymeric and composite films (0.5% nanoparticle concentration) deposited on the glass.

Sample C. A. (°) C. A. average (°) Glass / 5 NaPAC 16 66.39 65.09 _________ 64.66 _________ 65.38 Bottle / 1 PMH + TiO ₂ NPs (0.5%) 80.89 78.20 76.41 78.50 Bottle / 1 PMH + MgO NPs (0.5%) 99.74 89.25 102.21 94.42 96.41

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2. Antimicrobial activity was analyzed by agar diffusimetric method. On the medium, Mueller-Hinton (for bacterial strains) and Sabouraud (for fungi) were poured into Petri dishes. bacterial density 1-3x10 ⁸ CFU / mL and fungal 1-5x10 ⁶ CFU / mL. Subsequently, 10 μL of each compound, kept in the ultrasonic bath for 1 hour before testing, was added as a spot. Petri dishes were incubated for 18-24 hours at 37 ° C for bacterial strains, and 8 ° C for 72 hours for fungi. The reading of the results was performed by measuring with the help of the graduated ruler the area of inhibition of microbial growth on two perpendicular axes. [James HJ and Ferraro MJ. Antimicrobial Susceptibility Testing: A Review of General Principles and Contemporary Practices. Clin Infect Dis. 49 (11): 1749-1755, 2OO9./Araniciu C., Maruțescu L., Oniga S., Oniga O., Chifiriuc MC, Palage M., 2014, Evaluation of the antimicrobial and anti-biofilm activity ofsome 4,2 and 5.2 bisthiazole derivatives, Digest Journal of Nanomaterials and Biostructures, Vol. 9, No. 1, pp. 123 - 131 / Siti Hajar Othman, Nurul Raudhah Abd Salam, Norhazlizam Zainal, Roseliza Kadir Basha, Rosnita A. Talib, 2014, Antimicrobial Activity of Τ / Ό2 Nanoparticle-Coated Film for Potential Food Packaging Applications , International Journal of Photoenergy]

From the experimental data it results that the investigated nanocomposite film has a microbial activity against Staphylococcus aureus, Candida albicans, and Aspergillus niger. The activity was analyzed under various environmental conditions (light and dark), concentration of nonoparticles (0.01 -1%), in the form of powder or suspension. It was found that antimicrobial activity is directly proportional to the MgO content. However, from the imposed conditions (the color and the initial appearance must not vary) an optimal concentration of MgO -5% was identified.

3. Capillarity (water penetration: the action of capillarity)

The capillarity test was performed according to the procedure adapted after Teutonico [Teutonico, J.M., A laboratory manual for architectural conservators. You. 168. 1988: ICCROM Rome]. Place the reference specimen in a Petri dish. Add water to a height of 1 cm from the base of the brick. The height (H) is measured at each time of 2019 00350

10/06/2019 of 5 minutes, every 5 minutes for 25 minutes and then every 30 minutes. The results are recorded.

The reference specimen was obtained in the laboratory from a mixture of gypsum, lime, sand, water, formed in a silicone mold with dimensions 1x1x7 cm. Their treatment was carried out after drying in the oven, and the application of the consolidants was carried out by brushing.

The results presented in Table 2. As can be seen, the application of a composite film on the surface of the specimens determines an increase of 10%. For comparison, the table also shows the capillary values obtained in the case of the protective layer based on TiO ?.

Table 2. Variation of water capillarity depending on the applied protective layer

Time water height Time water height Time water height min cm min cm min cm witness Test tube with 0.1% NaPAC 16, 0.5% MgO (brushing) Test tube with 0.1% NaPAC 16, 0.5% T1O2 (brushing) 1 2.23 1 2 1 2.1 2 2.8 2 2.6 2 2.8 3 3.6 3 3.1 3 3.2 4 3.6 4 3.5 4 3.6 5 3.8 5 3.9 5 4 10 5.3 10 5.3 10 5.4 15 6.4 15 6.2 15 6.4 After 16 minutes the brick completely absorbed the water After 17:25 minutes the brick completely absorbed the water After 17:10 the brick completely absorbed the water -----

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4. Colorimetric tests

The chromatic parameters for the treated bricks were recorded with a Konica Minolta CR-410 colorimeter. 3 determinations were made both for the reference and for the treated samples and their average was made. The total color differences were calculated according to the equations: & Lf _inal = | Lx treated stone - Lx control | = | treated stone axis - control axis i

Ab / eoai = | bx treated stone - bx control i where: AL is the difference in brightness, Aa is the chromatic deviation of the coordinates a (red and green) and Ab is the chromatic deviation of the coordinates b (yellow and blue).

ΔΕ - color variation and stability

ΔΕ = [(ALfinal) ² + (Aa _fina i) ² + (Abfinal) ² ] ¹⁷²

ΔΕ evaluates the total color change. A small variation of this parameter, between 0 and 0.2 does not indicate a visible change. Between 0.2 and 2 there is a minor color difference. Values greater than 2 indicate visible color changes. At values above 6 the color is severely affected or even different.

In the case of burnt bricks (red) when the sample is immersed for 15 minutes in the dispersion of MgO (0.5%) + NaPAC16 (0.1%), after drying the values ΔΕ have an average of 0.18 which demonstrates the visual non-observation of the color change. Comparatively, if T1O2 is used, under similar conditions, the value ΔΕ is 0.39.

When the color test is done on a test piece (a mixture of gypsum, lime, sand, water, formed in a silicone mold with dimensions 1x1x7 cm) the values ΔΕ were between 0.77 and 1.24. In this case the composite film was obtained by brushing (three layers). The differences can be explained by the non-uniform application of the protective film, the procedure being manual.

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5. Photocatalytic test

The photocatalytic activity of the materials was tested by measuring the degree of methyl orange degradation in the presence of UV radiation (wavelength 254nm).

The process of the degradation experiment was as follows: 10 mL of 1x10 ' ⁵ M methyl orange (MO) solution was added to the quartz glass mini-reactors in which the film was immersed. It was initially stirred in the dark for 30 minutes to reach the adsorption-desorption balance, then the system was irradiated. The photocatalytic experiment was performed at room temperature for 60, 180, 300 min in UV (254 nm). Amounts of 2.5 mL of MO solution were collected at fixed intervals to determine the efficiency of the photodegradation.

The activity of photocatalysts was evaluated by determining the photodegradation efficiency of the dye. For the calculation of the photodegradation efficiencies, the absorption maximum for the dye was established by plotting the absorption spectrum on the range 190-900 nm. To determine the efficiency of the photocatalytic processes of MO, the absorption maximum of 464 nm was taken into account.

The absorbance (A) of the irradiated solution was measured using a UV-Vis spectrophotometer. The photocatalytic activity can be evaluated quantitatively by determining the discoloration rate of the dye calculated according to the following equation:

D% = {(Ao - A _t ) / Ao} * 100 (%);

where D represents the discoloration rate, Ao represents the initial absorbance (after stirring for 30 minutes in the dark) and At the absorbance at time t.

The tests were performed on MgO-based nanocomposite films. A number of 5 layers were deposited on the glass support by the layer by layer immersion method. After each immersion and extraction, with controlled speed, the sample was kept in the air for several hours at room temperature.

Table 5 shows the efficiency of the composite material analyzed in the degradation of methyl orange. Basically, after 5 hours the MO is decomposed in a proportion of 50%.

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In comparison, the T1O2 nanoparticles in the composite film have a yield three times lower in the decomposition of MO.

Table 3. Results of photocatalytic evaluation on MgO-based nanocomposite films

Sample Methyl orange degradation efficiency. 1 h 3h 5h Glass?! PMH 0.001% 0% 1 % Glass / 5 layers (NaPAC16 + ΊΊΟ2) (0.5%) 3.9% 13.62% 17.10% Glass / 5 layers (NaPAC16 + MgO) (0.5%) 18.86% 36.9% 49.13%

The invention has the following advantages:

- The use of magnesium oxide nanoparticles is of particular interest because, in addition to being a cheap and environmentally friendly material (bio-safe and biocompatible), it has antimicrobial activity and in the absence of light, due to high chemical activity on the surface;

- MgO nanoparticles can be an excellent photocatalyst for the degradation of organic pollutants;

- high compatibility of MgO with lithic materials;

- by relatively simple methods of preparation of MgO nanoparticles they can be controlled both in terms of morphology and particle size distribution.

- Na polyacrylate film has hydrophobic properties and is biodegradable. The presence of nanoparticles increases hydrophobicity;

- the possibility of applying thin films / films by simple methods (immersion, brushing, spraying) on different substrates (shape, size, composition, structure) with the possibility of controlling the thickness of the layers applied by multilayer deposits; the thickness ------ layer can also be controlled by easy-to-evaluate sanding (viscosity, speed of extraction from the solution in case of immersion);

- thin films can be applied on any surface (amorphous or crystalline, porous or compact) the precursor solution having a high degree of wetting;

- the possibility of interconnecting some materials.

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The following are examples of embodiments of the invention:

Example 1. Deposition of composite films based on magnesium oxide (MgO) nanoparticles dispersed in aqueous solution of hydrophobic modified polymer

Precursors used

MgO nanoparticles

Mg (NOa) 2 6H2O is dissolved in ethanol, the molar ratio ethanol / magnesium nitrate being 85. The solution is kept at 25 ° C for 1 h. The oxide powder is precipitated with an ammoniacal solution, pH = 10. It is filtered, washed with distilled water, dried and then, according to the results of the thermal analysis, calcined at 450 ° C with a bearing of 1 h and a heating rate of 1 ° C / min.

NaPACu - sodium salt of polyacrylic acid modified hydrophobically with hexildecyl amine (fatty amine with linear structure) by an amidation reaction using as precursor polyacrylic acid (PAA, M = 150 kDa, Wako Chemicals). PAA modification was performed by reacting the amine with the carboxyl groups of the precursor in the presence of DCC, N, N'dicyclohexylcarbodiimide (Sigma Aldrich, 99% purity) using 1-methyl-2-pyrrolidone (Sigma Aldrich, 99% purity) as solvent at temperature of 60 ° C. The recovery of the synthesized polymer was done by neutralizing and precipitating it in 40% aqueous sodium hydroxide solution (NaOH, Chimopar pa). Subsequently, the hydrophobic modified polymer was purified by dialysis and recovered by lyophilization. The theoretical degree of grafting was 3% (moles). All precursors used for the synthesis of NaPACie polymer were used in the state in which they were purchased, without being purified.

The polymeric solution of (PEI) polyethyleneimine (Sigma Aldrich, M = 75 kDa, 50% concentration in water) was used to activate the surface of the glass substrates.

The solution of cationic polymer PDADMAC, dialyldimethylammonium chloride (Sigma Aldrich, M = 100 ... 200 kDa, concentration 20% in water) was used to deposit counterion layers to adhere the composite layers composed of hydrophobic modified polymer NaPACu and powder of MgO. ________

Substrates used:

Microscope glass slides were used as a substrate for the deposition of protective coatings.

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Preparation of solutions for deposition on glass substrate

The preparation of the NaPACie solution in 0.1% concentration in ultra-pure water was performed under conditions of magnetic stirring at room temperature for 24 h to achieve the equilibrium of the reaction.

Preparation of the suspension of magnesium oxide (MgO) nanoparticles in the 0.1% NaPACie polymer solution

Ground MgO was dispersed in 0.1% polymer solution under continuous magnetic stirring.

Preparation of glass substrates for deposition

To clean the surfaces before the deposition process, the glass slides were washed with detergent and then immersed in a mixture of hydrogen peroxide H2O2 and H2SO4 (piranha mixture).

Sequence of electrostatic deposits by the layer-by-layer immersion method

The deposition of the layers on the glass by the layer-by-layer method was done in the following sequence:

Bottle 1. Immersion in PEI (concentration 5 * 10 ' ² M) for 20 min.

Wash with ultrapure water 1 min (to remove excess PEI)

Immersion in aqueous dispersion (Polymer - NaPACie) (0.1% + 0.5% MgO). Wash with ultrapure water 1 min (to eliminate excess aqueous dispersion. Immersion in PDADMAC solution (10 ' ² M) for 5 min

Wash with ultrapure water 1 min (to remove excess PDADMAC)

The extraction speed of the glass from the solutions was 0.8 cm / min

Steps 3-6 were repeated depending on the number of layers proposed

Example 2. The sequence of steps as above minus the red brick deposition phase (by immersion)

Preparation of burnt brick substrates for deposition

- Preparation by grinding to the size 1,5x1x0.5 cm)

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Preparation of the suspension of magnesium oxide (MgO) nanoparticles in the 0.1% NaPACie polymer solution

Ground MgO was dispersed in 0.1% polymer solution under continuous magnetic stirring.

deposit

1. The burnt brick sample is immersed in the 0.5% MgO suspension in 0.1% aqueous NaPAC16 solution for 15 minutes.

2. Leave in the air for at least 24 hours to dry

Steps 1-2 were repeated depending on the number of layers proposed

Example 3. Filing on standard test pieces

Substrate preparation

The standard specimens were obtained in the laboratory from a mixture of gypsum, lime, sand, water, formed in a silicone mold with dimensions 1x1x7 cm.

Laying protective coatings

1. The specimens were dried in the oven before applying the suspension of 0.5% nanoparticles of MgO in aqueous NaPAC16 solution. (at 60C for 2 hours)

2. The specimens were covered on all sides, the deposition being done by brushing.

3. Air drying after each application.

Steps 2-3 were repeated depending on the number of layers proposed

Claims (1)

claims 1. Process for obtaining nanocomposite films based on oxide nanoparticles and polymers in aqueous solution - for the protection of the surfaces of smooth architectural components, with low roughness such as glass, faience, sandstone or other polished building materials characterized by the preparation of a suspension of 0.5% MgO nanoparticles in a solution of NaPAC16- 0.1% modified hydrophobic sodium polyacrylate which is applied by spraying, immersion or brushing, in multilayer form, on the surface to be protected against environmental factors and pollutants providing hydrophobicity with contact angle values in the range 94-102 ° and microbial activity against Staphylococcus aureus, Candida albicans, and Aspergillus niger, a decrease in water absorption by capillarity by 10% unchanged color and appearance characterized by index values of color variation and stability ΔΕ is in the range 0.18 -1.24 and present Photocatalytic activity with a methyl orange degradation yield of 50% after 5 h.