Nano- to microscale three-dimensional morphology relevant to transport properties in reactive porous composite paint films

Xiaoyang Liu,Nicholas Zumbulyadis,Molly Wagner,Silvia A Centeno,Valeria Di Tullio,Vincent De Andrade,Chonghang Zhao,Yu-Chung Lin,Cecil Dybowski,Cheng-Hung Lin,Yu-Chen Karen Chen-Wiegart

doi:10.1038/s41598-020-75040-6

Abstract

The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability. Reactive porous paint materials are composites in nature and widely used in arts and technological applications. In artistic oil paintings, ambient moisture and water and organic solvents used in conservation treatments are known to trigger multiple physical and chemical degradation processes; however, there is no complete physical model that can quantitatively describe their transport in the paint films. In the present study, model oil paints with lead white (2PbCO3·Pb(OH)2) and zinc white (ZnO) pigments, which are frequently found in artistic oil paintings and are associated with the widespread heavy metal soap deterioration, were studied using synchrotron X-ray nano-tomography and unilateral nuclear magnetic resonance. This study aims to establish a relationship among the paints’ compositions, the 3D morphological properties and degradation. This connection is crucial for establishing reliable models that can predict transport properties of solvents used in conservation treatments and of species involved in deterioration reactions, such as soap formation.

Highlights

The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability
Reactive porous paint films consisting of inorganic pigments and a binding oil were investigated from the nano- to the microscale, to quantify their 3D morphology relevant to transport properties
Parameters associated with the 3D morphology of lead white and zinc white oil paints, such as the pigment and oil phase volume fractions, feature size distributions, tortuosity, connectivity of the oil/pore network, diffusion paths, and open porosity available for the diffusion of water, were calculated using a combination of synchrotron X-ray nano-tomography and unilateral Nuclear magnetic resonance (NMR) in model paint samples

Summary

Introduction

The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability. Ambient moisture and water and organic solvents used in conservation treatments are known to trigger multiple physical and chemical degradation processes; there is no complete physical model that can quantitatively describe their transport in the paint films. This study aims to establish a relationship among the paints’ compositions, the 3D morphological properties and degradation This connection is crucial for establishing reliable models that can predict transport properties of solvents used in conservation treatments and of species involved in deterioration reactions, such as soap formation. High temperature and relative humidity, as well as aqueous solutions and organic solvents used in conservation treatments, are important factors known to trigger soap formation[7,8,9,10], in addition to causing other physical and chemical degradation processes, such as paint swelling, the deformation of canvas stonybrook.edu. They reported that the canvas cellulose fibers and the glue sizing have a much stronger water uptake than the chalk ground layer bound in glue, and that the uptake rate is not uniform throughout the thickness of the sized canvas[23]

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Conclusion