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Effect of Adding UV Absorbers Embedded in Carbonate Calcium Templates Covered with Light Responsive Polymer into a Clear Wood Coating Caroline Queant *

ID

, Pierre Blanchet, Véronic Landry and Diane Schorr

Department of Wood and Forest Sciences, Université Laval, Québec City, QC G1V 0A6, Canada; [email protected] (P.B.); [email protected] (V.L.); [email protected] (D.S.) * Correspondence: [email protected]

Received: 24 June 2018; Accepted: 28 July 2018; Published: 28 July 2018

Abstract: The limited durability of clear coatings is a major issue for the coating and wood industry. The addition of organic UV absorbers improves coating resistance by the absorption and the conversion of the UV radiation into harmless heat. Organic UVAs are prone to degradation and can migrate in the binder of coatings. In this study, commercial UVAs and HALS have been entrapped into CaCO3 templates coated with stimuli responsive polymers. Microspheres were incorporated into a clear acrylic water-based coating formulation. The formulation was applied on glass and wood panels and was placed into an artificial UV chamber. This study presents a comparison between the aesthetic behavior of coating formulations with free and encapsulated commercial UVAs and HALS during the accelerated ageing test. Encapsulation of UVAs was confirmed by XPS and TGA analysis. Results have shown that the coating’s aesthetic was slightly improved when using the encapsulated products. Keywords: coatings; stimuli-sensitive polymers; structure-property relationships

1. Introduction Wood used for exterior applications is prone to environmental damages such as photodegradation (UV). The most damaging radiations are between 290 and 350 nm. The Planck-Einstein relation E = hc/λ (E: photon energy in joules; c: light speed in vacuum m/s; λ: wavelength in nm) states that the shorter the wavelength is, the higher the corresponding energy is. UV rays have enough energy to initiate scission reactions in polymer chains [1]. Lignin and carbohydrates components of wood are UV sensitive [2]. The resulting effect in wood leads to its discoloration and a change in its chemical and mechanical properties. The change in wood color is the first sign of chemical alteration [3–6]. To protect wood from alteration, coatings, impregnation, and chemical modification can be employed [7–9]. Applying coatings is the most common method to protect from degradation [10]. The desire amongst consumers for exterior clear coatings that will maintain the wood’s appearance is expanding [11,12]. However, they are more sensitive to UV light than opaque coatings. Their transparency allows UV rays to reach the wood underneath [1,4,5]. The use of UV absorbers (UVAs) contributes to the UV protection of coatings by screening harmful radiations. Organic UVAs are molecules with conjugated π electrons systems that are able to absorb the UV radiation and convert it into harmless heat [13]. Benzophenones type UVAs are commonly used with HALS (hindered amine light stabilizers), which show synergistic photoprotection [14]. UV light responsive microspheres can be employed to release encapsulated materials upon UV illumination. An interesting group of molecules that can respond to near-UV and visible light are azobenzenes. Azobenzene molecules contain two phenyl groups attached by a N=N bond.

Coatings 2018, 8, 265; doi:10.3390/coatings8080265

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UV light responsive microspheres can be employed to release encapsulated materials upon UV light responsive microspheres can be employed to release encapsulated materials upon of 14 An interesting group of molecules that can respond to near-UV and visible2 light UV illumination. An interesting group of molecules that can respond to near-UV and visible light are azobenzenes. Azobenzene molecules contain two phenyl groups attached by a N=N bond. are azobenzenes. Azobenzene molecules contain two phenyl groups attached by a N=N bond. This bond allows a cis-trans rearrangement by UV absorption [15]. Microspheres are used in various Thisbond bondallows allowsaacis-trans cis-transrearrangement rearrangementby byUV UVabsorption absorption[15]. [15].Microspheres Microspheresare areused usedin invarious various This applications [16,17]. Studies from Yi et al. (2014) [18] have shown synthesis of UV responsive applications [16,17]. [16,17]. Studies Studies from from Yi Yi etet al. al. (2014) (2014) [18] [18] have have shown shown synthesis synthesis of of UV UV responsive responsive applications polyelectrolyte microcapsules by sequential deposition. With UV exposure, microcapsules were polyelectrolyte microcapsules by sequential deposition. With UV exposure, microcapsules were polyelectrolyte microcapsules by sequential deposition. With UV exposure, microcapsules were disrupted. This has the effect to modulate protein release. Zhao et al. (2012) [19] worked on the design disrupted.This Thishas hasthe theeffect effectto tomodulate modulateprotein proteinrelease. release.Zhao Zhaoetetal. al.(2012) (2012)[19] [19]worked workedon onthe the design design disrupted. and preparation of light-responsive biocompatible micelles. Applications are light triggering delivery andpreparation preparationof oflight-responsive light-responsivebiocompatible biocompatiblemicelles. micelles.Applications Applicationsare arelight light triggering triggering delivery delivery and of drugs and others bioagents. Microspheres have been introduced into coatings in many studies and of drugs drugs and and others been introduced into coatings in many studies and of others bioagents. bioagents.Microspheres Microsphereshave have been introduced into coatings in many studies applications. applications. and applications. The main objective of this study is to suggest a tailored solution to increase the durability of clear The main main objective suggest a tailored solution to increase the durability of clear The objective of ofthis thisstudy studyisistoto suggest a tailored solution to increase the durability of coatings. In this study, encapsulation of organic UVAs in microspheres is used for UV protection coatings. In this study, encapsulation of organic UVAs in microspheres is used for UV protection clear coatings. In this study, encapsulation of organic UVAs in microspheres is used for UV protection improvement. Poly(1-(4-(3-carboxy-4-hydroxyphenyl-azo)benzenesulfonamido)-1,2-ethanediyl) (PAZO) improvement. Poly(1-(4-(3-carboxy-4-hydroxyphenyl-azo)benzenesulfonamido)-1,2-ethanediyl) Poly(1-(4-(3-carboxy-4-hydroxyphenyl-azo)benzenesulfonamido)-1,2-ethanediyl) (PAZO) (PAZO) improvement. is used as a light responsive polymer. UVAs and HALS were encapsulated into CaCO3 templates is used as a light responsive polymer. UVAs and HALS were encapsulated into CaCO 3 templates is used as a light responsive polymer. UVAs and HALS were encapsulated into CaCO3 templates with with PAZO and poly(diallyldimethylammonium chloride) (PDADMAC) layers. Encapsulated with PAZO and poly(diallyldimethylammonium chloride) (PDADMAC) layers. Encapsulated PAZO and poly(diallyldimethylammonium chloride) (PDADMAC) layers. Encapsulated compounds compounds were incorporated into water-based acrylic coating formulations. Artificial accelerated compounds were into incorporated intoacrylic water-based acrylic coatingArtificial formulations. Artificial accelerated were incorporated water-based coating formulations. accelerated weathering was weathering was performed to evaluate the effect of encapsulated compounds on the behavior of weathering was performed to evaluate the effect of encapsulated compounds on the behavior of performed to evaluate the effect of encapsulated compounds on the behavior of coating aesthetic in coating aesthetic in response to intense UV exposition. coating aesthetic response to intense UV exposition. response to intenseinUV exposition. Coatings 2018, 8, 265 UV illumination.

2. Materialsand and Methods 2. 2. Materials Materials and Methods Methods 2.1. Materials 2.1. 2.1. Materials Materials 1-propanol, CaCl22,,Na Na2CO33 (Fisher (Fisher Chemical, St St Louis, MO, MO, USA),poly(diallyldimethylammonium poly(diallyldimethylammonium 1-propanol, 1-propanol,CaCl CaCl2, Na22CO CO3 (Fisher Chemical, Chemical, St Louis, Louis, MO, USA), USA), poly(diallyldimethylammonium chloride) solution (PDADMAC M w 200,000–350,000, 20 wt.% in H 2 O), and poly(1-(4-(3-carboxy-4chloride) H22O), O), and and poly(1-(4-(3-carboxy-4poly(1-(4-(3-carboxy-4chloride) solution solution (PDADMAC (PDADMAC M Mww 200,000–350,000, 200,000–350,000, 20 20 wt.% wt.% in in H hydroxyphenyl-azo)benzenesulfonamido)-1,2-ethanediyl, sodium salt) (PAZO) (Figure 1) (Sigma hydroxyphenyl-azo)benzenesulfonamido)-1,2-ethanediyl, sodium salt) (PAZO) (Figure 1) (Sigma hydroxyphenyl-azo)benzenesulfonamido)-1,2-ethanediyl, sodium salt) (PAZO) (Figure 1)Aldrich, (Sigma Aldrich, St Louis, MO, USA) were used without any further purification. UV stabilizers Tinuvin 1130 St Louis, MO, USA)MO, wereUSA) used were without any furtherany purification. UV stabilizers 1130Tinuvin and Tinuvin Aldrich, St Louis, used without further purification. UVTinuvin stabilizers 1130 and Tinuvin 292 (derived piperidine) from tetramethyl piperidine) were obtained from BASF (Laval, QC, 292 from were obtained from BASF QC, from Canada). The(Laval, commercial and(derived Tinuvin 292tetramethyl (derived from tetramethyl piperidine) were(Laval, obtained BASF QC, Canada). The commercial UVA used in this study is of the hydroxyphenylbenzotriazole type UVA used in thiscommercial study is of the hydroxyphenylbenzotriazole 2). Deionized water was used Canada). The UVA used in this study is oftype the(Figure hydroxyphenylbenzotriazole type (Figure 2). this Deionized water was used throughout this study. throughout study. (Figure 2). Deionized water was used throughout this study.

Figure 1. Chemicalstructure structure ofthe the poly(1-(4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido)Figure Figure1.1.Chemical Chemical structure of of the poly(1-(4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido)poly(1-(4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido)1,2-ethanediyl)(PAZO) (PAZO)polymer. polymer. 1,2-ethanediyl) 1,2-ethanediyl) (PAZO) polymer.

Figure 2. Chemical composition of Tinuvin 1130. Figure2.2. Chemical Chemical composition compositionof ofTinuvin Tinuvin1130. 1130. Figure

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Coatings 2018, x FOR PEER REVIEW 2.2. Synthesis of8,CaCO 3 Templates with Tinuvin 1130 and Tinuvin 292

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2.2. of CaCO 3 Templates with Tinuvin and Tinuvin 292 1130 and Tinuvin 292 was obtained TheSynthesis formation of CaCO with 1130 embedded Tinuvin 3 templates by the coprecipitation (Figure 3) of CaCl and Na CO salts [20]. CaCO templates wereobtained prepared by 2 3 Tinuvin 1130 The formation of CaCO3 templates 2with embedded and 3Tinuvin 292 was mixing equal volume of Na (1ofM) and CaCl solutions under magnetic stirring for 1by h. 0.1 g 2 CO33) 2 2(1 by the coprecipitation (Figure CaCl 2 and Na COM) 3 salts [20]. CaCO 3 templates were prepared of concentrated solution of and Tinuvin Tinuvinunder 292 was added to theforCaCl solution mixing equalcommercial volume of Na 2CO3 (1 M) CaCl21130 (1 M)orsolutions magnetic stirring 1 h. 20.1 g solution of Tinuvin 1130 or Tinuvin 292 was added to the CaCl 2 solution prioroftoconcentrated the mixing commercial with the Na CO solution. During the precipitation process, the precipitates were 2 3 prior to the mixing with the Na 2 CO 3 solution. During the precipitation process, the precipitates were vigorously stirred by a magnetic stirring bar. They were then rinsed three times with deionized water. ◦ C times by a magnetic the stirring bar. They were rinsed three water. Aftervigorously removingstirred the supernatant, precipitates werethen dried at 80 for 2 with daysdeionized and stored at room After removing the supernatant, the precipitates were dried at 80 °C for 2 days and stored at room temperature prior to use. temperature prior to use. To obtain complete dissolution of Tinuvin 1130 and Tinuvin 292, 40 wt.% of the water was replaced To obtain complete dissolution of Tinuvin 1130 and Tinuvin 292, 40 wt.% of the water was by 1-propanol into the CaCl2 solution. replaced by 1-propanol into the CaCl2 solution.

Figure 3. Synthesis of CaCO3 templates and layer by layer deposition.

Figure 3. Synthesis of CaCO3 templates and layer by layer deposition. 2.3. Layer by Layer Deposition of Polyelectrolytes

2.3. Layer by Layer Deposition of Polyelectrolytes

Polyelectrolytes were deposited on the CaCO3 templates alternately for 15 min (Figure 3), Polyelectrolytes were deposited the CaCO(1 alternately for 15then min the (Figure 3), starting starting with the positively chargedon PDADMAC mg/mL in 0.15 M NaCl) and negatively 3 templates PAZO (1 mg/mL PDADMAC in 0.15 M NaCl). Resultingincoated microspheres three times withcharged the positively charged (1 mg/mL 0.15 M NaCl) and were then washed the negatively charged with ToMavoid aggregation, were ultrasonicated for 10 three s aftertimes each with PAZO (1 purified mg/mLwater. in 0.15 NaCl). Resultingmicrospheres coated microspheres were washed deposition The layer by layer microspheres deposition technique was already used studies for purified water. step. To avoid aggregation, were ultrasonicated for in 10 several s after each deposition polyelectrolyte deposition and coating of various inorganic microspheres [15,21,22].

step. The layer by layer deposition technique was already used in several studies for polyelectrolyte deposition and coating of various inorganic microspheres [15,21,22]. 3. Characterization Techniques TransmissionTechniques Electron Microscopy (TEM) was performed on the microspheres to investigate the 3. Characterization

shape. The observation was performed by using an electronic microscope JOEL 1230 (Peabody, MA, Transmission Electronvoltage Microscopy (TEM) was performed the directly microspheres to investigate USA) at an acceleration of 80 kV. Microsphere solutionsonwere deposited on nickel the shape. The observation waswith performed byformvar. using an electronic microscope JOEL 1230 (Peabody, MA, microscope grids coated carbon and

USA) at an acceleration voltage of 80 kV. Microsphere solutions were directly deposited on nickel 3.1. XPSgrids coated with carbon and formvar. microscope X-ray photoelectron spectroscopy (XPS) was used to study the chemical composition of the 10

3.1. XPS nm surface of grinded CaCO3 templates with commercial UVAs. Experiments were performed with an XPSphotoelectron instrument (Axis-Ultra) from Kratos Analytical, Manchester, UK.composition This equipment X-ray spectroscopy (XPS) was used to study the chemical of theis10 nm composed of three communicating chambers: the analysis chamber comprising the ESCA analyzer, surface of grinded CaCO3 templates with commercial UVAs. Experiments were performed with an the preparation chamber, and the introduction chamber. Survey scans were recorded using an X-ray XPS instrument (Axis-Ultra) from Kratos Analytical, Manchester, UK. This equipment is composed of monochromatic Al source operated at 300 W. The X-ray source was oriented with a 30° incidence three communicating chambers: the analysis chamber comprising the ESCA analyzer, the preparation angle. Scans were obtained with pass energy of 160 eV and with lens used in hybrid mode. Survey chamber, introduction chamber. Survey scansconcentration were recorded using an X-ray monochromatic scans and werethe used for elemental analysis and apparent calculations. Calculation of the

Al source operated at 300 W. The X-ray source was oriented with a 30◦ incidence angle. Scans were obtained with pass energy of 160 eV and with lens used in hybrid mode. Survey scans were used for

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elemental analysis and apparent concentration calculations. Calculation of the apparent relative atomic concentrations were performed with the software CasaXPS (Version 2.1.9, 2002) based on principles found in standard textbooks and using sensitivity factors pertinent to the operating conditions of the spectrometer. 3.2. TGA Thermogravimetric analysis curves were collected with a thermoanalyzer TGA 851e from Mettler Toledo (Columbus, OH, USA). Measurements were performed over a 25–850◦ C temperature range at 10 ◦ C/min under a nitrogen flow. Crucibles used were made of aluminum oxide. Three replicates were performed for each sample. 3.3. Introduction of Encapsulated UVAs in an Acrylic Water-Based Formulation Microspheres were pre-dispersed in water in order to obtain a better distribution before the addition to the paint formulation (Table 1). Percentages of UVAs and HALS added to the formulation are detailed in Table 2. The solution was mixed with a given paint formulation using a high-speed disperser Dispermat LC 30 (BASF) at 1000 rpm for 1 h. Several formulations were prepared and applied on glass and wood panels for testing (Table 2). The control sample contained only the paint formulation without any protective absorber. Table 1. Clear coat complete formulation. Formulation

Weight (g)

Acrylic binder Water Solvent and plasticizer Liquid rheological Silicone surfactant Defoamer Biocide

50.23 30.9 1.68 1.6 0.71 0.56 0.05

Table 2. Composition of the formulations. Sample

Free UVAs (wt.%)

Free HALS (wt.%)

CaCO3 + UVAs (wt.%)

CaCO3 + HALS (wt.%)

Control Formulation 1 Formulation 2 Formulation 3 Formulation 4

– 0.1 0.1 – –

– – 0.1 – –

– – – 2.5 2.5

– – – – 2.5

UVAs and hindered amine light stabilizers (HALS) are often utilized together to improve their performance. Tinuvin 1130 (UVA) and Tinuvin 292 (HALS) are indeed known to have a synergistic effect [23,24]. Part of the formulations were prepared using UVAs as well as HALS. For an optimal protection, BASF guidelines advise the use of 1–3 wt.% of UVA and 0.5–2 wt.% of HALS, which explains the UVA concentration selected. Concentrations are based on weight percent binder solids. All formulations were prepared in triplicates. 3.4. Weathering Tests Two types of accelerated artificial ageing tests devices were used—Atlas Ci3000 + Weather-Ometer (Atlas Electric Devices Company, Mount Prospect, IL, USA) and a QUV accelerated weathering tester from Q-Lab (Westlake, OH, USA). To evaluate the coating behavior on its own, tests were first carried on glass supports of 68 mm × 144 mm × 4 mm. Samples were exposed to a xenon lamp of 4500 W in the Weather-Ometer. Artificial xenon exposures were performed to simulate the entire UV and visible

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spectrum of daylight. The filter combination used was an inner Type S Boro and an outer Soda Lime. Samples were exposed to 2500 h of ageing. The standard test method employed for accelerated ageing tests is the ASTM G155 “Standard Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials“ [25]. Cycle 4 was selected: the irradiance was set at 0.30 W m−2 nm−1 Coatings 2018, 8, x FOR PEER REVIEW 5 of 14 with 100% light, 55% relative humidity, at 55 ◦ C black panel temperature. No water spray was used. This cycle the “Standard continuous lightening could induce degradation. ageingwas testschosen is the because ASTM G155 Practice for Operating Xenonquicker Arc Light Apparatus for The second series of tests was performed on4wood panels.the White spruce (Picea Exposure of Non-Metallic Materials“ [25]. Cycle was selected: irradiance was set atglauca 0.30 W(Moench) m−2 −1 with 100% light, 55% relative humidity, at 55 °C black panel temperature. No water spray was nm Voss) boards were obtained from Maibec (Saint-Pamphile, QC, Canada) and were cut into 75 mm × used. was chosen the continuous lightening couldafter induce quicker degradation. 50 mm × 4This mmcycle samples. They because were sanded with P150 sand paper being stored and conditioned ◦ The second series ofhumidity tests was performed on wood panels. White spruce (Picea glauca (Moench) at 20 C and 65% relative until constant mass at 12% humidity. Panels were placed into Voss) boards were obtained from Maibec (Saint-Pamphile, QC, Canada) and were cut into 75 mm × the accelerated ageing tester QUV. Tests were performed in accordance to the ASTM G154-2012 50 mm × 4 mm samples. They were sanded with P150 sand paper after being stored and conditioned Standard test method “Standard Practice for operating Fluorescent Ultraviolet (UV) Lamp Apparatus at 20 °C and 65% relative humidity until constant mass at 12% humidity. Panels were placed into the for exposure of non-metallic Materials” [26]. Cycle 1 was selected. The first step is at a temperature accelerated ageing tester QUV. Tests were performed in accordance to the ASTM G154-2012 Standard ◦ 2 ◦ C Black Panel of 60test C method and energy 0.89 W/m h. The condensation cycle then(UV) begins at 50 “Standard Practicefor for8 operating Fluorescent Ultraviolet Lamp Apparatus for Temperature 4 h. An UV-A 340 lamp Westlake, USA) was for the irradiation at exposure for of non-metallic Materials” [26]. (Q-Lab, Cycle 1 was selected.OH, The first step is atused a temperature of 60 °C − 2 − 1 2 0.89 W menergy nm 0.89toW/m simulate UVcondensation portion of the solar spectrum. chosen with a dark and for 8 the h. The cycle then begins at This 50 °Ccycle Blackwas Panel Temperature h. An UV-A 340 lamp (Q-Lab, OH, cycle. USA) was used for the irradiation at 0.89 W m−2 phasefor to4reproduce more precisely theWestlake, natural light nm−1 to simulate the UV portion the solar spectrum. This cycle waswith chosen with a dark phase Formulations were applied on of glass substrate and wood panels a roller-coater (BYK,toWesel, reproduce more precisely the natural light cycle. Germany) at a speed of 50 mm/s. Two wet layers of 50 µm of each coating were deposited. Formulations were applied on glass substrate and wood panels with a roller-coater (BYK, Wesel, Germany) 3.5. Colorimeterat a speed of 50 mm/s. Two wet layers of 50 µ m of each coating were deposited.

The color change in the coating systems was measured with a colorimeter (BYK-Gardner 3.5. Colorimeter Colorguide 45/0, Wessel, Germany). Three measurements were taken for each sample. The average The color change in the coating systems was measured with a colorimeter (BYK-Gardner valueColorguide was calculated and is reported inThree this paper. CIELABwere (defined International 45/0, Wessel, Germany). measurements takenby forthe each sample. The Commission average on Illumination (CIE) L*a*b*. for the in lightness and a* and(defined b* for the and blue–yellow value was calculated and isL* reported this paper. CIELAB bygreen–red the International Commission color components) color scale used. Three b*)the were determined for each sample. on Illumination (CIE)was L*a*b*. L* for the coordinates lightness and(L*, a* a*, andand b* for green–red and blue–yellow color components) scale was used. coordinates (L*, a*,(0) and were determined Chromatic coordinatescolor are L*, which is theThree lightness from black tob*) black/white (100);for a*, each the color sample. Chromatic coordinates are L*, which is the lightness from black (0) to black/white (100); component from green (−60) to red (+60); and b*, the color component from blue (−60) to yellow (+60). the color component from green (−60) toseparately red (+60); and b*, the color component from blue (−60) to Each a*, component’s evolution was evaluated [10]. yellow (+60). Each component’s evolution was evaluated separately [10].

4. Results and Discussion

4. Results and Discussion

4.1. Characterization Techniques

4.1. Characterization Techniques

CaCO3 microspheres coated with polyelectrolytes were observed with TEM at 400×. Images CaCO3 microspheres coated with polyelectrolytes were observed with TEM at 400×. Images (Figure 4) show microspheres of sizes ranging from approximatively 10 nm to 300 nm. Size distribution (Figure 4) show microspheres of sizes ranging from approximatively 10 nm to 300 nm. Size was found to be was highly heterogeneous. The morphology observed is mostly ispolygonal, while some distribution found to be highly heterogeneous. The morphology observed mostly polygonal, particles are cubic. while some particles are cubic.

(a)

(b)

Figure 4. Observation of CaCO3 coated microspheres with Transmission Electron Microscopy (TEM)

Figure 4. Observation of CaCO3 coated microspheres with Transmission Electron Microscopy (TEM) 400×: (a) Agglomeration of CaCO3 microspheres; (b) Cubic CaCO3 coated particles. 400×: (a) Agglomeration of CaCO3 microspheres; (b) Cubic CaCO3 coated particles.

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4.2. 4.2.XPS XPS Apparent Apparentrelative relativeconcentrations concentrationsare aregiven givenby byatomic atomicpercentages percentageson onsurvey surveyspectra. spectra.Hydrogen Hydrogen isisnot included as it is not detectable. Concentrations are apparent and considered homogeneous not included as it is not detectable. Concentrations are apparent and considered homogeneous on on entire volume analyzed × µm 400 ×µm × 5 The nm).survey The survey spectrum 5) shows thethe entire volume analyzed (800(800 µmµm × 400 5 nm). spectrum (Figure(Figure 5) shows atomic atomic composition quantity for carbon, nitrogen, calcium, sodium,oxygen, oxygen,chlorine, chlorine, and and phosphorus composition quantity for carbon, nitrogen, calcium, sodium, phosphorus elements. elements.Phosphorous Phosphorouscould couldcome comefrom fromthe thewater watermedium mediumofofthe thecoprecipitation coprecipitationreaction. reaction.

25

x 10

4

Name Na 1s O 1s N 1s Ca 2p C 1s Cl 2p P 2p

At% 2.40 42.21 2.22 15.08 37.57 0.26 0.27

O 1s

30

15

Ca 2p

Na 1s

CPS

20

1000

800

600 400 Binding Ene rgy (e V)

P 2p

Cl 2p

5

C 1s

N 1s

10

200

Laboratoire d'analyse de surface-CERPIC-Université Laval

Figure5.5.Survey Surveyspectrum spectrumof ofelementary elementaryanalysis analysison onembedded embeddedUVAs UVAsinto intoCaCO CaCO3sample. sample. Figure 3

The Ca spectrum (Figure 6) shows a Ca 2p characteristic peak of a carbonate. This is also The Ca spectrum (Figure 6) shows a Ca 2p characteristic peak of a carbonate. This is also confirmed confirmed by the C 1s spectrum (Figure 7). The binding energy of 289.51 eV corresponds to an O=C– by the C 1s spectrum (Figure 7). The binding energy of 289.51 eV corresponds to an O=C–O group, O group, which is also characteristic of a carbonate. These elements show that the coprecipitation which is also characteristic of a carbonate. These elements show that the coprecipitation process has process has correctly happened. It has led to the formation of carbonates such as CaCO3 [27]. correctly happened. It has led to the formation of carbonates such as CaCO3 [27]. N 1s high resolution spectrum (Figure 8) shows two narrow peaks of different binding energies N 1s high resolution spectrum (Figure 8) shows two narrow peaks of different binding energies and another large peak that can correspond to a nitrogen atom linked to an aromatic carbon. N 1s-1 and another large peak that can correspond to a nitrogen atom linked to an aromatic carbon. N 1s-1 peak binding energy corresponds to a pyrrole or pyridone group [28]. N 1s-2 peak corresponds to a peak binding energy corresponds to a pyrrole or pyridone group [28]. N 1s-2 peak corresponds to a Carom–N–X. These two groups belong to the Tinuvin 1130 molecule. This result shows that Tinuvin Carom –N–X. These two groups belong to the Tinuvin 1130 molecule. This result shows that Tinuvin 1130 is embedded into the CaCO3 templates. 1130 is embedded into the CaCO3 templates.

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3 x 10 3 STD = 1.27631 xResidual 10 Residual STD = 1.27631

Name Ca 2p3/2 Name Ca 2p3/2 2p1/2 Ca Ca 2p1/2

Pos. FWHM L.Sh. 347.23 1.45 GL(60) Pos. FWHM L.Sh. 350.75 1.45 1.49 GL(60) GL(60) 347.23 350.75 1.49 GL(60)

Area %Area 15975.0 67.23 Area %Area 7800.6 67.23 32.77 15975.0 7800.6 32.77

Ca 2p3/2 Ca 2p3/2

CPSCPS

10 10

8 8

Ca 2p1/2 Ca 2p1/2

6 6

4 4

2 2

354 354

351 348 Binding 351 Ene rgy (e V) 348 Binding Ene rgy (e V)

345 345

Laboratoire d'analyse de surface-CERPIC-UniversitéLaval Laboratoire d'analyse de surface-CERPIC-UniversitéLaval

Figure 6. Ca 2p high resolution spectra on embedded UVAs into CaCO3 sample.

Figure 6. Ca 2p 2p high resolution embeddedUVAs UVAs into CaCO 3 sample. Figure 6. Ca high resolutionspectra spectra on on embedded into CaCO 3 sample. C1s C1s

2 x 10 2 Residual STD = 0.999636 x 10 50 Residual STD = 0.999636 50 45 45 40 40

Name C-C, C-H Name C-OC=N C-C, C-H C=O C-OC=N O=C-O, carbonate C=O sat O=C-O, carbonate sat

CPSCPS

35 35

Pos. FWHM L.Sh. 285.00 1.38 GL(30) Pos. FWHM L.Sh. 286.30 1.38 GL(30) GL(30) 285.00 1.38 287.31 1.38 1.38 GL(30) GL(30) 286.30 289.51 1.38 1.29 GL(30) GL(50) 287.31 291.00 1.29 2.00 GL(50) GL(30) 289.51 291.00 carbonate 2.00 GL(30) O=C-O,

Area %Area 3181.8 30.45 Area %Area 1771.2 16.94 3181.8 30.45 618.0 16.94 5.91 1771.2 4602.6 618.0 43.93 5.91 289.9 2.76 4602.6 43.93 289.9 2.76

O=C-O, carbonate

30 30 C-C, C-H C-C, C-H

25 25 20 20

C-OC=N C-OC=N

15 15 10 10 5 5

C=O C=O

sat sat 291 291

288 Binding288 Ene rgy (e V) Binding Ene rgy (e V)

Laboratoire d'analyse de surface-CERPIC-UniversitéLaval

285 285

282 282


Figure 7. C 1s high resolution spectra on embedded UVAs into CaCO3 sample. Figure 7. C 1s high resolution spectra on embedded UVAs into CaCO3 sample.

Figure 7. C 1s high resolution spectra on embedded UVAs into CaCO3 sample.

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2

x 10 Residual STD = 0.885898 85

80

Name N 1s-1 N 1s-2 sat

Pos. FWHM L.Sh. 400.30 1.47 GL(30) 402.74 1.71 GL(30) 408.25 3.52 GL(30)

Area %Area 2684.1 59.43 1567.1 34.66 268.2 5.91

N 1s -1

CPS

75

70

N 1s -2

65

60

sat

408

404 Binding Ene rgy (e V)

400

396


Figure N high 1s high resolutionspectra spectra on on embedded CaCO 3 sample. Figure 8. N8.1s resolution embeddedUVAs UVAsinto into CaCO 3 sample.

4.3. TGA

4.3. TGA

Control CaCO3 templates (Figure 9) start degrading at 700 °C. Under nitrogen, 84.5% (±1.6) of

◦ C. Under nitrogen, 84.5% (±1.6) Control (Figure degraded 9) start degrading 700 3 templates the CaCOCaCO 3 template alone is thermally at the end ofatthe analysis at 900 °C. A CaCO3 sample ◦ of thewith CaCO alone is thermally the end°C ofwas the78.6% analysis atfor 900 A CaCO3 embedded UVAs was also analyzed. degraded The weight at loss at 900 (±1.9) thisC. sample. 3 template ◦ UVAs start to degrade from 200 600 °C. Entrapped takeloss more and(± degrade. sample with embedded UVAs wastoalso analyzed. TheUVAs weight attime 900 toCevaporate was 78.6% 1.9) for this ◦ C. Entrapped TheUVAs weightstart losstodifference 3 samples with and without to the and sample. degrade between from 200CaCO to 600 UVAs takeUVAs more corresponds time to evaporate evaporation and degradation of the embedded UVAs. Coated CaCO 3 templates present a different degrade. The weight loss difference between CaCO3 samples with and without UVAs corresponds to thermoanalysis of the degradation of the polyelectrolytes. It starts at approximatively 100 °C the evaporation andbecause degradation of the embedded UVAs. Coated CaCO 3 templates present a different and goes up to 850 °C or even more. The thermal degradation of azo polymers and azo organic ◦ thermoanalysis because of the degradation of the polyelectrolytes. It starts at approximatively 100 C molecules was studied in [29]. Five percent weight loss temperature of azo polymers was found to and goes up to 850 ◦ C or even more. The thermal degradation of azo polymers and azo organic be between 274 and 302 °C. Those temperatures correspond to the degradation found in this study. molecules in [29]. Five percent weight temperature of700 azo°C. polymers was found to Alongwas withstudied the polyelectrolytes degradation, CaCO3loss begins to degrade at be between 274 and 302 ◦ C. Those temperatures correspond to the degradation found in this study. Along with the polyelectrolytes degradation, CaCO3 begins to degrade at 700 ◦ C.


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Templates + +UVA+ polyelectrolytes Templates UVA+ polyelectrolytes 0

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200 200

400 600 400 600 Temperature (°C)

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Temperature (°C)

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Figure 9. Thermoanalysis curves of samples of control, UVAs only, CaCO3 templates + UVAs, and on

Figure curves of samples of Figure 9. 9. Thermoanalysis Thermoanalysis curves samples of control, control, UVAs UVAsonly, only,CaCO CaCO33templates templates++ UVAs, UVAs,and andon on CaCO3 templates with UVAsof and polyelectrolytes. CaCO templates with UVAs and polyelectrolytes. 3 CaCO3 templates with UVAs and polyelectrolytes. 4.4. Weathering Tests

4.4. Tests 4.4. Weathering WeatheringMonitoring Tests

the color of wood and its coatings allows to obtain information on coating degradation. An efficient coating should help to keep a stable color. The overall color variation (ΔE) Monitoring wood and its coatings allowsastoaallows obtain to information on In coating degradation. Monitoring thecolor of wood and its coatings obtain time. information on coating should the tend to color zeroof(Figure 10) [10]. Color is measured function of exposure this study, An efficient coating should help to keep a stable color. The overall color variation (∆E) should tend the overall color varies more for the encapsulated formulations. Because ΔE is only a vector, it is degradation. An efficient coating should help to keep a stable color. The overall color variation (ΔE) important dissociate study the color to zero (Figure 10) to [10]. Colorand is measured ascomponents a functionevolution. of exposure time. In this study, the overall

should tend to zero (Figure 10) [10]. Color is measured as a function of exposure time. In this study, color varies color more varies for themore encapsulated formulations.formulations. Because ∆E is only a ΔE vector, it is aimportant the overall for the encapsulated Because is only vector, itto is 9 Non encaps UVA dissociate and study the color components evolution. 8 important to dissociate and study the color components Nonevolution. encaps UVA + HALS 7

Delta E

8 6

2

3

Non encaps UVA

4 3

4

Encaps UVA+HALS

5

7 5

Encaps UVA

6

Delta E

9

Non encaps UVA + HALS Encaps UVA Encaps UVA+HALS

1 0 0

200

400 Exposure time (h)

600

Figure 10. Evolution of ΔE for the different formulations on glass panels with Weather-Ometer 2 exposure. 1

0 The monitoring of the separate components (a*, b*, and L*) shows more precise information in 0 200 400 600 the variation. The evolution of a* and b* (Figure 11) shows a different behavior for the encapsulated Exposure time (h) formulations. Non-encapsulated formulations remain stable after 600 h of Weather-Ometer exposition. Encapsulated formulations evolve toward blue (−) and red (+). This transition could be Figure10. 10.Evolution Evolution of for different the different formulations onpanels glasswith panels with Weather-Ometer Figure ∆EΔE for the on glass Weather-Ometer exposure. explained by theofconformational changeformulations of the PAZO molecule. The photoisomerization reaction of exposure. azobenzene groups is triggered by UV irradiation (Figure 12) [21]. Two separate absorption regions are responsible for the trans-cis and cis-trans isomerization of the azobenzene molecules. Once the The monitoring of the separate components (a*, b*, and L*) shows more precise information in transition of molecular conformation is achieved,(a*, theb*, absorbance therefore theinformation color The monitoring of the separate components and L*)changes, shows and more precise in the variation. of a* andwell b* (Figure shows different behavior(Figure for the shiftsThe [30].evolution This transition in 11) photos beforeaaand after weathering 13).encapsulated The the variation. The evolution of is a*also and b* visible (Figure 11) shows different behavior for the encapsulated formulations. Non-encapsulated formulations remain stable after 600 h of Weather-Ometer exposition. formulation with non-encapsulated UVAs have clearly photoyellowed, which is not the case of the formulations. Non-encapsulated formulations remain stable after 600 h of Weather-Ometer encapsulated UVAs formulations. The encapsulated formulations coatings to be yellow. Encapsulated formulations evolve toward blue (−) and red (+). have Thisprevented transition could explained by

exposition. Encapsulated formulations evolve toward blue (−) and red (+). This transition could be the conformational change of the PAZO molecule. The photoisomerization reaction of azobenzene explained by the conformational change of the PAZO molecule. The photoisomerization reaction of groups is triggered by UV irradiation (Figure 12) [21]. Two separate absorption regions are responsible azobenzene groups is triggered by UV irradiation (Figure 12) [21]. Two separate absorption regions for the trans-cis and cis-trans isomerization of the azobenzene molecules. Once the transition of are responsible for the trans-cis and cis-trans isomerization of the azobenzene molecules. Once the molecular conformation is achieved, the absorbance changes, and therefore the color shifts [30]. transition of molecular conformation is achieved, the absorbance changes, and therefore the color This transition is also well visible in photos before and after weathering (Figure 13). The formulation shifts [30]. This transition is also well visible in photos before and after weathering (Figure 13). The with non-encapsulated UVAs have clearly photoyellowed, which is not the case of the encapsulated formulation with non-encapsulated UVAs have clearly photoyellowed, which is not the case of the UVAs formulations. The encapsulated formulations have prevented coatings to yellow. encapsulated UVAs formulations. The encapsulated formulations have prevented coatings to yellow.

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20 20 20 18 18 18 16 16 16 14 14 14 12 12 10 10 88 8 66 6 4 4 2 2

Non-encapsulated UVA Non-encapsulated UVA

Non-encapsulated UVA Non-encapsulated UVA + HALS Non-encapsulated UVA + HALS Non-encapsulated UVA + HALS Encapsulated UVA Encapsulated UVA Encapsulated UVA Encapsulated UVA + HALS Encapsulated UVA + HALS Encapsulated UVA + HALS

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Non Non encapsulated UVA encapsulated UVA Non encapsulated UVA Non Non encapsulated UVA + HALS encapsulated UVA + HALS Non encapsulated UVA + HALS Encapsulated UVA Encapsulated UVA Encapsulated UVA Encapsulated UVA + HALS Encapsulated UVA + HALS Encapsulated UVA + HALS

Exposure time Exposure time (h)(h) Exposure time (h) (a) (a)

00

0

200 200

400400 600 600 Exposure time (h) (h) 200 400 600 Exposure time

Exposure time (h) (b)(b)

(a)

(b)

Figure 11. Evolution of (a) a*and (b) b* for the different formulations on glass panels with Weather-

Evolution of of (a) (a) a*and a*and (b) (b) b* b* for for the the different different formulations formulations on on glass glass panels panelswith with WeatherWeatherFigure 11. Evolution FigureOmeter 11. Evolution exposure.of (a) a*and (b) b* for the different formulations on glass panels with WeatherOmeter exposure. Ometer exposure.

Figure 12. Photoisomerization reaction of PAZO molecule. Adapted from [30].

Figure 12. Photoisomerization Photoisomerization reaction reaction of of PAZO molecule. Adapted from [30]. Figure 12. Photoisomerization reaction of PAZO molecule. Adapted from [30].

(a)

(b)

Figure 13. Photos before (a) and after (b) weathering of the non-encapsulated formulations on glass support of 68 mm × 144 mm × 4 mm (top) and the encapsulated ones (bottom).

(a) (a)

(b) (b)

were (a) applied on white spruce panels to test the behavior offormulations wood underneath the FigureFormulations 13. Photos before and after (b) weathering of the non-encapsulated on glass Figure 13. Photos Photos before (a) and after (b) weathering weathering of the thesome non-encapsulated formulations oncontrol glass Figure 13. before (a) and after (b) of non-encapsulated formulations on glass formulations. After only 48 h of exposure in QUV tester, formulations as well as the support of 68 mm × 144 mm × 4 mm (top) and the encapsulated ones (bottom). support of 68 mm mm × 144 ××4 4mm and ones (bottom). support 68 × 144mm mm mm(top) (top) andthe theencapsulated encapsulated ones (bottom). sample of start to darken. Wood color depends on UV protection efficiency. Changes in wood color reflect chemical degradation occurring during weathering [3]. Photoinduced discoloration starts to the Formulations were applied on white spruce panels to test the behavior of wood underneath Formulations applied on whiteThis spruce panels toistest the behavior of wood underneath occur after onlywere 24 h of QUV exposure. phenomenon explained by the lignin degradation and the Formulations white spruce panels to some test the behavior of as wood the formulations. Afterwere onlyapplied 48 h ofon exposure in QUV tester, formulations wellunderneath as the control formulations. Afterofonly 48 h ofaromatic exposure in QUV [10]. tester, formulations as well as the control the formation unsaturated compounds Thesome test was carried out for 2500 h. formulations. onlyWood 48 h of exposure in QUV tester, some formulations as wellin aswood the control sample start toAfter darken. color depends on UV protection efficiency. Changes color sample start darken. Wood ofcolor depends on allows UV protection Changes inthus wood Thetocolor monitoring the wood panels to study efficiency. wood degradation and UVcolor sample start to darken. Wood color depends on UV protection efficiency. Changes in wood color reflect reflect chemical degradation occurring during weathering [3]. Photoinduced discoloration starts to protection efficiency. The most efficient protective coating should absorb the entire UV spectrum, reflect chemical degradation occurring during weathering [3]. Photoinduced discoloration starts to chemical occurring during weathering [3]. Photoinduced starts to occur occur afterdegradation onlyno24UV h of QUV exposure. This phenomenon is explained bydiscoloration the lignin degradation and light should reach the underneath. Wood discoloration is a sign of wood occur and afterthus only 24 h of QUV exposure. Thiswood phenomenon is explained by the lignin degradation and afterformation only 24 h of QUV exposure. This phenomenon is explained by the lignin degradation and the the of unsaturated aromatic compounds [10]. The test was carried out for 2500 h. degradation and of a less efficient coating. the formation of unsaturated aromatic compounds [10]. The test was carried out for 2500 h. formation of unsaturated aromatic compounds [10]. The test was carried out for 2500 h. For L* monitoring color components (Figures all formulations most important colorand variation The color of the wood14) panels allows to show studythewood degradation thus UV The color monitoring of the wood panels allows to study wood degradation and thus UV in the first monitoring 500 h The of exposure. This early phenomenon is study caused by the degradation visible radiation, which The color of the wood panels allows to andspectrum, thus UV protection efficiency. most efficient protective coating shouldwood absorb the entire UV protection efficiency. The most efficient protective coating should absorb the entire UV spectrum, decomposes products into This effect is worse with protection efficiency. most efficient protective coating[31]. should absorb the entire UV and thus no UV yellowing lightThe should reach thecolorless wood compounds underneath. Wood discoloration is a accelerated signspectrum, of wood

and thus no UV light should reach the wood underneath. Wood discoloration is a sign of wood and thus no and UV of light should reach the wood underneath. Wood discoloration is a sign of wood degradation a less efficient coating. degradation and of a less efficient coating. degradation and of a less efficient coating. For L* color components (Figures 14) all formulations show the most important color variation For L* color components (Figures 14) all formulations show the most important color variation For L* color 14) all formulationsisshow theby most color variation in the first 500 hcomponents of exposure.(Figure This early phenomenon caused theimportant visible radiation, which in the first 500 h of exposure. This early phenomenon is caused by the visible radiation, which in the first 500 h of exposure. early phenomenon caused the isvisible which decomposes yellowing productsThis into colorless compoundsis[31]. Thisby effect worseradiation, with accelerated decomposes yellowing products into colorless compounds [31]. This effect is worse with accelerated

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decomposes yellowing products into colorless compounds [31]. This effect is worse with accelerated Coatings 2018, 8, x FOR PEER REVIEW 11 of 14 testing devices atxx high light intensity and with shorter dark periods than in natural exposition Coatings 2018, 8, 8, FOR PEER PEER REVIEW 11 of of 14 14 [32]. Coatings 2018, FOR REVIEW 11 Lighttesting sources emitting fluorescent UV-Aand tubes induce exaggerated unnatural devices at high light intensity with shorter dark periodsand than in naturalphotoyellowing exposition [32]. [33]. testingsources devices at at high light intensity andno with shorter dark periods and than in natural natural exposition [32]. This Light change in color thelight beginning has impact ondark mechanical properties ofphotoyellowing the binder [31,33]. testing devices at high intensity and with shorter periods than in exposition [32]. emitting fluorescent UV-A tubes induce exaggerated unnatural LightThis sources emitting fluorescent UV-A tubes tubes induce exaggerated and unnatural unnatural photoyellowing Light sources emitting UV-A induce exaggerated and photoyellowing The change affects only thefluorescent aesthetic properties wood. [33]. change in color at the beginning hasof nothe impact on mechanical properties of the binder [33]. This This change inaffects color only at the the beginning has no no impact impact onwood. mechanical properties of the the binder binder [33]. change color has on of [31,33]. The changein thebeginning aestheticcompounds, properties of the the For the formulations withat encapsulated L*mechanical parameterproperties (Figure 14) presents a good [31,33]. The change affects only the aesthetic properties of the wood. [31,33]. The change affects only the aesthetic properties of the wood. For the encapsulated the L*formulations. parameter (Figure presents stability from 500formulations to 2500 h ofwith QUV exposition compounds, for encapsulated The 14) slope of theacurve For the formulations formulations withhencapsulated encapsulated compounds, the L* L* parameter parameter (Figure 14)slope presents For the with compounds, the (Figure 14) presents aa good stability from 500non-encapsulated to 2500 of QUV exposition encapsulated formulations. The of the for the formulations with UVAs is for slightly more pronounced, which shows that the good stability from 500 to 2500 h of QUV exposition for encapsulated formulations. The slope of the good stability from 500 to 2500 h of QUV exposition for encapsulated formulations. The slope of the curve for the formulations with non-encapsulated UVAs is slightly more pronounced, which shows woodcurve is still darkening during UV exposition. The parameter a* more (Figure 15) during UV shows exposition forwood the formulations formulations with non-encapsulated UVAs is slightly pronounced, which curvethe for the with non-encapsulated UVAs is slightly more pronounced, shows that is still darkening during UV exposition. The parameter a* (Figure 15)which during UV evolves toward red and then reaches stabilization after 500 h. The formulation with non-encapsulated that the the wood wood is still still darkening during UV exposition. exposition. Theafter parameter a* (Figure (Figure 15) during during UV that is darkening UV The parameter a* 15) UV exposition evolves toward red andduring then reaches stabilization 500 h. The formulation with nonUVAsencapsulated and HALS presents a slope near 0, which makes the best formulation for the a* component exposition evolves toward red and then reaches stabilization after 500 h. The formulation with nonexposition evolves toward red and then reaches stabilization after 500 h. The formulation with nonUVAs and HALS presents a slope near 0, which makes the best formulation for the a* only. encapsulated UVAs and HALSof presents slope near 0,awhich which makes the best formulation for the a* a* The evolution of the b* and component (Figure 16) shows similar slope for the different formulations. encapsulated UVAs HALS presents aa slope near 0, best formulation the component only. The evolution the b* component (Figure 16) makes shows athe similar slope for thefor different component only. The evolution of the b* component (Figure 16) shows a similar slope for the different However, the yellowing is minimized with encapsulated compounds (lower b* values). component only. The evolution of the b* 16) shows acompounds similar slope for the formulations. However, the yellowing iscomponent minimized (Figure with encapsulated (lower b*different values). formulations. However, However, the the yellowing yellowing is is minimized minimized with with encapsulated encapsulated compounds compounds (lower (lower b* b* values). values). formulations. 75 75 75

L* L*L*

70 70 70 65 65 65

Non-encapsulated UVA Non-encapsulated UVA UVA + HALS Non-encapsulated

60 60 60 55 55 0 55 00

Non-encapsulated UVA ++ HALS HALS Encapsulated UVAUVA Non-encapsulated Encapsulated UVA UVA + HALS Encapsulated

500 500 500

Encapsulated UVA UVA ++ HALS HALS Encapsulated

1000 1500 2000 1000 1500 2000 1000 1500 QUV exposition (h) 2000 QUV exposition exposition (h) (h) QUV

2500 2500 2500

Figure 14. component L* component evolutionfor for the the different different formulations studied with QUV exposure. Figure 14. L* evolution formulations studied with QUV exposure.

a* a* a*

Figure 14. 14. L* L* component component evolution evolution for for the the different different formulations formulations studied studied with with QUV QUV exposure. exposure. Figure 16 16 16 14 14 14 12 12 12 10 10 10 8 8 68 6 6 4 4 4 2 2 2 0 00 0

00

Non-encapsulated UVA Non-encapsulated UVA UVA + HALS Non-encapsulated Non-encapsulated UVA ++ HALS HALS Encapsulated UVAUVA Non-encapsulated Encapsulated UVA UVA + HALS Encapsulated 500 500 500

Encapsulated UVA UVA ++ HALS HALS Encapsulated 1000 1500 2000 2500 1000 1500 2000 2500 1000 1500 2000 2500

QUV exposition (h) QUV exposition exposition (h) (h) QUV

Figure 15. a* component evolution for the different formulations studied with QUV exposure.

b* b* b*

Figure 15.component a* component component evolutionfor forthe the different different formulations formulations studied with QUV exposure. Figure 15. a* evolution formulations studied with QUV exposure. Figure 15. a* evolution for the different studied with QUV exposure. 51 51 51 46 46 46 41 41 41 36 36 36 31 31 31 26 26 26 21 21 0 21 00

Non-encapsulated UVA Non-encapsulated UVA UVA + HALS Non-encapsulated Non-encapsulated UVA Non-encapsulated UVA ++ HALS HALS Encapsulated UVAUVA Non-encapsulated Encapsulated UVA UVA + HALS Encapsulated Encapsulated UVA Encapsulated UVA UVA ++ HALS HALS Encapsulated

500 500 500

1000 1500 1000 1500(h) 1000 1500 QUV exposition QUV exposition (h) QUV exposition (h)

2000 2000 2000

2500 2500 2500

Figure 16. b* component evolution for the different formulations studied with QUV exposure. Figure 16. b* component evolution for the different formulations studied with QUV exposure.

Figure 16.component b* component evolutionfor forthe the different different formulations studied with QUV exposure. Figure 16. b* evolution formulations studied with QUV exposure.

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In comparison to formulations with non-encapsulated compounds, formulations with encapsulated compounds were found to be slightly more stable. Indeed, darkening and yellowing evolve more slowly during the UV illumination. One explanation is that the PAZO rearrangement observed on glass support causes the small evolution of color. 5. Conclusion Very few studies report the preparation and the use of UV responsive microspheres. The main objective of the study was to examine the effect of adding microspheres in a transparent acrylic water-based formulation. Commercial UVAs and HALS were embedded into CaCO3 templates by coprecipitation of CaCl2 and Na2 CO3 . Polyelectrolytes were deposited around the templates. PAZO is a light responsive polymer which changes its polymer structure upon radiation. The synthesis method was found to be efficient to encapsulate a small amount of UVAs and HALS. Microspheres prepared were incorporated into a clear coat formulation. Colorimetric studies on glass support show proof of the molecular transition in conformation of PAZO chains. This transition is revealed by a modification of the absorption during UV exposition. Experiments on wood panels show a similar behavior for formulations with non-encapsulated and encapsulated compounds. Color analysis reveals a global color evolution toward red, blue, and black. Although it is difficult to extrapolate about UV protection efficiency from color results, encapsulated formulations appear to prevent darkening from yellowing. One solution to improve efficiency of encapsulated formulations would be to achieve a better encapsulation of UVAs and HALS. This could be done by optimizing the coprecipitation process and solubility of products. These conclusions are exploratory results meant to assess the effect of adding encapsulated UVAs into a clear coat formulation. Encapsulated UVAs could give an alternative solution in the field of clear coat UV protection. Encapsulated UVAs could help to preserve wood aesthetics and provide more durable protection. These data only show aesthetic and colorimetric analysis. Future studies should include results on mechanical and physical properties. Results obtained in the present study are from an accelerated weathering tester. Further studies should include natural exposition data. Author Contributions: Conceptualization, P.B, V.L, C.Q.; Methodology, P.B, V.L, D.S, C.Q.; Software, C.Q.; Validation, P.B, V.L, D.S, C.Q; Formal Analysis, C.Q.; Investigation, C.Q.; Resources, P.B, V.L, D.S,.; Data Curation, C.Q.; Writing-Original Draft Preparation, C.Q.; Writing-Review & Editing, P.B, V.L, DS.; Visualization, C.Q.; Supervision, P.B and V.L.; Project Administration, P.B and V.L.; Funding Acquisition, P.B. Funding: This research was funded by Natural Sciences and Engineering Research Council of Canada for the financial support (IRC No 461745 and CRD No 445200). Acknowledgments: The authors are grateful to the industrial partners of the NSERC Industrial Chair on EcoResponsible Wood Construction (CIRCERB). Conflicts of Interest: The authors declare that they have no conflict of interest.

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