Cork: properties, capabilities and applications

Abstract

Cork is a natural, renewable, sustainable raw material that has been used for many centuries. As a result of this very long term interest, the scientific literature on cork is extensive. The present review focuses on the chemical composition, physical and mechanical properties of cork and on its products and sub-products. The substantial efforts to fully characterise cork, as well as new developments and evolving research, are reviewed, beginning with its histology, growth and morphology (at macro-and microscales). The chemical structure is analysed in detail, covering both the materials that form the wall structure and the low molecular weight, extractable components. The unique properties of cork are discussed and correlated with current knowledge on morphology and chemical structure. Finally, the important industrial applications of cork are reviewed, in the context of research to provide cork with novel, high added-value applications.

Comparison of low and high pressure infiltration regimes on the density and highly porous microstructure of ceria ecoceramics made from sustainable cork templates

“…Cork has a microstructure different to other lignocellulosic woods, consisting of hollow polyhedral cells, with a hexagonal honeycomb shape (∼20 μm diameter) when viewed from the radial direction coming out of the tree, and a rectangular shape (∼45 μm length, resembling a brick wall) when viewed from the transverse side or top directions [22,23]. There are up to 200 million cells per cm 3 [24], and due to this structure, cork exhibits exceptional thermal, acoustic and vibrational insulation, and a very low density of 0.12-0.24 g/cm 3 [25], the higher densities occurring when the cell walls are corrugated. Therefore, it is an ideal natural template to form ecoceramics, although in natural cork all the cells are sealed with front and rear walls, and as such it has a low open porosity and is not very permeable.…”

The Potential of Agglomerated Cork for Sandwich Structures: A Systematic Investigation of Physical, Thermal, and Mechanical Properties

“…As previously mentioned, the number of edges of the polygonal base can vary from four to nine, but the shapes that are most frequent from a statistical point of view are the pentagonal, hexagonal, and heptagonal ones [7,17], as can be observed in Figure 3. In the literature, an average cell-wall thickness of 1-1.5 µ m was detected for early cork [6,8], and a thickness up to 2 µ m was detected for late cork [7]. Figure 4 reports the measurement of cell-wall thickness of NL10, NL20, and NL25 performed with the program Image J.…”

“…Prisms are stacked base-to-base along the radial direction and this means that, if cork is observed in this direction, a polygonal shape is recognized. Instead, if it is observed in the axial or tangential direction, it displays a brick-layered structure that can be ascribed to the parallel arrangement of cells [6][7][8]17].…”

“…This can be explained taking into account, as mentioned previously, that even if test speed had an effect on PVC foam yield strength and plateau stress, the speed working range was not broad enough to detect it markedly. The estimation of the regression coefficients of each parameter led to Equations (5)- (7).…”

Experimental and finite element analysis of the impact response of agglomerated cork and its intraply hybrid flax/basalt sandwich structures

“…➢ "Effect of basalt fibre hybridisation and sizing removal on mechanical and thermal properties of hemp fibre reinforced HDPE composites" Fabrizio Sarasini, Jacopo Tirillò, Claudia Sergi, Maria [36] with some micrographs of the cross section of the radial (A), axial (B) and tangential direction (C) [35] .. 38…”