What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach
Abstract
:1. Introduction
1.1. Phenol Formaldehyde (PF) Foams as a Complex Chemical Formulation
1.2. Open- and Closed-Cell PF Foams and Their Applications
1.3. Stability of PF Foams
1.4. Aim of This Research
2. Materials and Methods
2.1. Materials
“Unaged” and Naturally Indoor-Aged Materials
- -
- Balsa Foam Soft Density: Naturally Aged 1 is the brighter zone under the label (not glued on the surface), and Naturally Aged 2 is the one outside the covered area, which resulted in a darker shade.
- -
- Balsa Foam 5 PCF: Naturally Aged 1 is the portion covered by the label (not glued on the surface), while Naturally Aged 2 refers to the area surrounding it on the same surface, and Naturally Aged 3 is the upper lateral part of the block, which was more exposed to the surrounding environment.
- -
- Austrotherm: Naturally Aged 1 is the surface cut in 2018, and Naturally Aged 2 is the external one.
2.2. Optical Microscopy (OM)
2.3. Fiber Optics Reflectance Spectroscopy (FORS)
2.4. Micro-Fourier Transform Infrared (μ-FTIR) Spectroscopy
2.5. pH Measurements
3. Results and Discussion
3.1. Optical Microscopy (OM)
3.1.1. “Unaged” Open- and Closed-Cell PF Foams
3.1.2. Naturally Aged Open- and Closed-Cell PF Foams
3.2. Fiber Optics Reflectance Spectroscopy (FORS)
3.2.1. “Unaged” Open- and Closed-Cell PF Foams
3.2.2. Naturally Aged Open- and Closed-Cell PF Foams
3.3. Micro-Fourier Transform Infrared (μ-FTIR) Spectroscopy
3.3.1. “Unaged” Open- and Closed-Cell PF Foams
3.3.2. Naturally Aged Open- and Closed-Cell PF Foams
3.4. pH Measurements
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Structure Cell Type | Commercial Name | Application | Color | Cell Diameter (µm) | Cell Struts Thickness (µm) | Cell Shape | General Observations after Natural Ageing | ||||
---|---|---|---|---|---|---|---|---|---|---|---|
Min | Max | Average | Min | Max | Average | ||||||
Open-cell | Gardol | floral arrangments | 86 | 272 | 181 | 16 | 39 | 28 | polygonal from 4 to 6 sides (mainly 5) | cell walls rupture | |
Oasis | 109 | 224 | 180 | 13 | 22 | 18 | pentagonal (few with 2 sides shorter) | elongations of cells | |||
Closed-cell | Balsa Foam Soft Density | sculpting | 100 | 158 | 129 | 16 | 27 | 23 | hexagonal | browning/elongation of two sides cells/cell walls rupture/brittle cell struts | |
Balsa Foam 5 PCF | 78 | 130 | 97 | 14 | 30 | 21 | hexagonal | browning/cell walls rupture/brittle cell struts | |||
Austrotherm | thermal insulation | 61 | 122 | 88 | 7 | 16 | 11 | polygonal from 4 to 7 sides | Browning/brittle cell struts |
Structure Cell Type | Samples | Color | CIELab Color Coordinates | CIELab Color Shifts | Total Color Change | |||||
---|---|---|---|---|---|---|---|---|---|---|
L* | a* | b* | ∆L* | ∆a* | ∆b* | ∆E*1976 | ||||
Open-cell | Gardol | “Unaged” | 52.4 | −8.0 | 12.3 | 1.1 | 5.6 | 1.9 | 6.0 | |
Natually Aged | 53.5 | −2.4 | 14.2 | |||||||
Oasis | “Unaged” | 59.2 | −25.5 | 3.0 | −2.3 | 3.3 | 1.7 | 4.4 | ||
Natually Aged | 56.9 | −22.2 | 4.7 | |||||||
Closed-cell | Balsa Foam Soft Density | “Unaged” | 82.4 | 20.6 | 49.8 | 2.1 | −1.6 | 1.1 | 2.9 | |
Naturally Aged 1 | 84.5 | 19.0 | 50.9 | |||||||
Naturally Aged 2 | 73.6 | 26.3 | 49.3 | −10.9 | 7.3 | −1.6 | 13.2 | |||
Balsa Foam 5 PCF | “Unaged” | 86.8 | 17.3 | 51.1 | −0.6 | −1.9 | −2.1 | 2.9 | ||
Naturally Aged 1 | 86.2 | 15.4 | 49.0 | |||||||
Naturally Aged 2 | 80.3 | 21.2 | 50.1 | −5.9 | 5.8 | 1.1 | 8.3 | |||
Naturally Aged 3 | 70.5 | 26.4 | 45.9 | −9.8 | 5.2 | −4.2 | 11.9 | |||
Austrotherm | “Unaged” | 59.1 | 23.2 | 25.0 | 7.1 | 7.4 | 14.8 | 18.0 | ||
Naturally Aged 1 | 66.2 | 30.6 | 39.8 | |||||||
Naturally Aged 2 | 72.1 | 28.5 | 47.1 | 5.9 | -2.1 | 7.3 | 9.6 |
PF Foams | |||||||
---|---|---|---|---|---|---|---|
Open-Cell | Closed-Cell | ||||||
Bond Type | Gardol | Oasis | Balsa Foam Soft Density | Balsa Foam 5 PCF | Austrotherm | Lit. Data Range [5,8,13,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39] | Lit. Compound Type Assignment |
Wavenumber cm−1 | |||||||
O–H stretching | 3374 | 3348 | 3386 | 3386 | 3387 | 3389–3100 | Phenolic O–H [5,8,24,25,26,27,28] and methylol OH [5,24,26,29] |
C–H stretching | 3009 | 3014 | 3007 | 3009 | 3010 | 3300–3010 | Phenolic ring C–H [5,24,27,28] |
2921; 2868 | 2924; 2855 | 2908; 2864 | 2911; 2867 | 2921; 2871 | 2953–2800 | Methylene group –CH2– [5,24,25,27,28] | |
O | O | 2789 | 2791 | O | 2724 | CH2 groups of formaldehyde (–CHO) [25] | |
C=O stretching and C–C stretching | 1742.000 | O | 1751.000 | 1751.000 | O | 1755–1735 | Arlyl carboxylic acid [35,38]/Tetra–substituted benzene ring C–C stretching [27,36] |
C=O stretching | O | O | 1722 (shoulder) | 1721 | O | 1720 | Hydroxy acids COOH [13] |
O | O | O | O | 1709 | 1704 | (Phenolic) C=O [34] | |
O | O | 1685 (shoulder) | O | O | 1660–1690 | Quinoid structures [13] | |
1650 | O | 1651 | 1651 | 1653; 1648 | 1643 | Formaldehyde monomer residue [8]/benzophenone by oxidation of methylene groups [13,27]/(Phenolic) C=O [34] | |
C=C stretching | 1606 | 1606; 1594; 1558; 1504 | 1606; 1503 (weak shoulder) | 1607; 1503 (weak shoulder) | 1600; 1501 | 1633–1500 | Phenolic ring C=C [5,8,24,25,26,28,29] |
C–H bending and C=C stretching | 1478 | 1478 | 1476 | 1478 | 1475 | 1480–1473 | Scissor bending vibration of CH2 (o–p’ ) [31,32,33] |
1447 | 1442 | 1450 (shoulder) | 1450 (shoulder) | 1451 (weak shoulder) | 1456–1450 | Scissor bending vibration of CH2 (p–p’) [31,32,33] and C=C aromatic ring [28,29] | |
O | O | O | O | 1436 | 1437 | Aliphatic CH3 [27] | |
O–H in plane bending and C–H bending | O | O | 1377 | 1377 | O | 1378–1370 | Phenolic O–H groups [5,24,25] /C–H deformation vibration of aliphatic hydrocarbons [27] / O–H in plane bending of carboxylic acids [39] |
1354 | 1353 | 1353 | 1353 | 1349 | 1360 –1340 | Phenolic O–H groups [5,8,24,25,26,28] / C–H deformation vibration of aliphatic hydrocarbons [27] | |
C–H bending (overtone) | 1326 | O | 1324 | 1326 | O | CH2 groups | |
C–O stretching | O | O | 1260 (shoulder) | 1260 (shoulder) | 1257 (shoulder) | 1270–1260 | Biphenyl ether C–O [28] / alkyl–phenol C–O [30] / carboxylic acids C–O [39] |
1223 | 1210 | 1235; 1223 | 1234; 1223 | 1208 | 1240–1210 | Phenolic C–O [5,24,25,26,27,28,30] and ether bond [29] | |
C–H bending andC–O stretching | 1167 | O | 1168 | 1168 | O | 1175–1160 | Aromatic C–H in plane deformation [5,24,28] |
1146 | 1151 | 1143 | 1146 | 1138 | 1153–1147 | Aromatic C–H in plane deformation [26,28] and dimethylerne ether C–O–C– bridges [29] | |
1064 | 1124; 1102 (shoulders) | 1077 | 1077 | 1098; 1077 | 1120–1060 | Aromatic C–H in plane deformation [5,8,24,28] and dimethylene ether C–O–C [5,26,27] | |
C–O stretching | 1031; 1006 | 1029; 1005 | 1012 | 1035; 1013 | 1032; 1011 | 1058–1010 | Alcoholic C–O (methylol groups) [5,24,25,26,27,28,29] |
C–H bending | O | O | 992 | 992 | O | 997–960 | Phenol with trisubstitution at 1,2,4 positions [25,28] / =C–H def. of aryl and/or a,b–unsaturated carboxylic acid [38] |
O | O | 933 | 932 | O | 950–920 | C–O–C ether alyphatic or aromatic C–O–O–C peroxide [32]; O–H out of plane of carboxylic acids [39] | |
884 | 885 | 880 | 881 | 883 | 890–875 | Phenol with tri–substitution at 1,2,4 positions (o,p) [5,13] and tetra–substitution at 1,2,4,6 positions (o,o',p) [5,24,25,26,28,30] | |
818 | 828 | 822 | 820 | 822 | 826–814 | Phenol with di–substitutions at 1,4 positions (p) [5,24,25,26,28,30] and tri–substitution at 1,2,4 positions (o,p) [13] | |
779 | O | 775 | 778 | 777 | 790–780 | Phenol with tri–substituions at 1,2,6 positions (o,o') [5,24,28] | |
759 | 767 | 753 | 754 | 748 | 760 –756 | Phenol with di–substituions at 1,2 positions (o) [5,24,25,28,31] and tri–substituions at 1,2,6 positions [30,31] | |
O | O | 714 | 714 | O | – | CH2 rocking [32] | |
685 | 695 | 680 | 680 (shoulder) | 700 | 694–690 | Monosubstituted ring [5,24,25,28] |
Bond Type | Wavenumber (cm−1) | Change Type | Assignment |
---|---|---|---|
C=O stretching | 1751 | → shift to 1744 | changes in aryl carboxylic acids conformation |
1721 | ↑ increase | formation of hydroxy acids | |
1650 | ↑ increase | formation of benzophenone through oxidation of methylene bridges | |
C–H bending | 1447; 1326 | ↓ decrease | decrease of methylene bridge through primary oxidation |
O–H in plane bending | 1354 | ↓ decrease | slight reduction of phenolic O–H through secondary oxidation |
C–H bending and C–O stretching | 1168–1064 | ↓ decrease | ether bridge oxidation andvariation of aromatic C–H conformation |
C–O stretching | 1005–1035 | ↓ decrease | decrease of methylol groups |
Structure Cell Type | Samples | Color | pH | |
---|---|---|---|---|
Open-cell | Gardol | “Unaged” | 2.8 ± 0.01 | |
Natually Aged | 2.9 ± 0.06 | |||
Oasis | Unaged | 2.8 ± 0.00 | ||
Natually Aged | 2.9 ± 0.00 | |||
Closed-cell | Balsa Foam Soft Density | “Unaged” | 3.8 ± 0.00 | |
Naturally Aged 1 | 4.0 ± 0.06 | |||
Naturally Aged 2 | 4.1 ± 0.06 | |||
Balsa Foam 5 PCF | “Unaged” | 4.0 ± 0.00 | ||
Naturally Aged 1 | 4.2 ± 0.00 | |||
Naturally Aged 2 | 4.3 ± 0.00 | |||
Naturally Aged 3 | 4.4 ± 0.00 | |||
Austrotherm | “Unaged” | 3.0 ± 0.06 | ||
Naturally Aged 1 | 3.0 ± 0.00 | |||
Naturally Aged 2 | 3.1 ± 0.01 |
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Pintus, V.; Piccolo, A.; Vetter, W.; Moretto, L.M.; Sterflinger, K.; Schreiner, M. What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach. Polymers 2021, 13, 1964. https://doi.org/10.3390/polym13121964
Pintus V, Piccolo A, Vetter W, Moretto LM, Sterflinger K, Schreiner M. What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach. Polymers. 2021; 13(12):1964. https://doi.org/10.3390/polym13121964
Chicago/Turabian StylePintus, Valentina, Anna Piccolo, Wilfried Vetter, Ligia Maria Moretto, Katja Sterflinger, and Manfred Schreiner. 2021. "What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach" Polymers 13, no. 12: 1964. https://doi.org/10.3390/polym13121964