Sodium Iodide as a Contrast Agent for X-ray Micro-CT of a Wood Plastic Composite

Dengcheng Feng,Philip D Evans,Michael Turner

doi:10.3390/app12010208

Dengcheng Feng, Philip D Evans + Show 1 more

Open Access

https://doi.org/10.3390/app12010208

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Abstract

The properties of wood plastic composites (WPCs) depend on their microstructure, particularly the level and geometry of wood reinforcement in the composite. We hypothesize that impregnating a WPC with a radiocontrast agent will increase the contrast between wood and plastic, allowing better visualization of its microstructure and numerical analysis of the geometry of its wood reinforcement. A commercial WPC was scanned using X-ray micro-CT, impregnated with aqueous sodium iodide, and then rescanned. CT data from both scans were visualized, and we analyzed the geometry of wood reinforcement and levels of wood, plastic, zinc borate (ZB), and voids in the WPC. ZB occurred mainly as discrete particles between wood flakes, and interfacial voids formed a network of cracks within the WPC. Sodium iodide labeling made it possible to clearly visualize wood and plastic in the WPC and quantify levels of different phases and the geometry of wood particles. However, sodium iodide was not an ideal contrast agent because it swelled wood particles, closed interfacial voids, and partially dissolved ZB particles. We suggest methods of overcoming these limitations and conclude that advances in labeling are necessary to improve our understanding of the relationship between the microstructure of WPCs and their properties.

Highlights

Wood plastic composites (WPCs) are an important class of natural fiber-reinforced composites, and in North America alone, approximately 2000 Kt of wood plastic composite (WPC) are produced each year, with an estimated market value of USD 6 billion [1]
We used the definition of aspect ratio from Merkus [30], Impregnation of the WPC sample with sodium iodide made it possible to clearly which is the maximum Feret diameter divided by the minimum Feret diameter
The unimpregnated sample contained voids within and aroundtowood particles, parImpregnation of the WPC sample with sodium iodide made it possible clearly difticularly larger particles, whereas such voids were absent from the impregnated sample

Summary

Introduction

Wood plastic composites (WPCs) are an important class of natural fiber-reinforced composites, and in North America alone, approximately 2000 Kt of WPCs are produced each year, with an estimated market value of USD 6 billion [1]. Smaller wood particles act as a filler in WPCs, but larger particles provide reinforcement [2]. Tailoring the size and geometry of particles can improve the mechanical properties of WPCs. For example, previous studies have examined the relationships between the initial size and length-to-width ratio of wood particles (measured using microscopy) and the mechanical properties of WPCs [5,6]. Previous studies have examined the relationships between the initial size and length-to-width ratio of wood particles (measured using microscopy) and the mechanical properties of WPCs [5,6] These studies have shown that when wood particles have a larger aspect ratio, ‘there is potential for more effective load transfer between the plastic and particles leading to better mechanical properties’ [7]

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