Cork Agglomerate Research Articles

Wetting of cork by polymeric adhesives

The cohesion of cork agglomerates is determined by the strength of the adhesive joint established between the polymeric adhesive and the cork particles. The ability of adhesives to form good joints depends, among other factors, on the wetting of cork by the adhesives. The main objective of this research was to study the behaviour of adhesive drops deposited on cork substrates through measurements of contact angles and their time dependence. Several polyurethane prepolymers were tested to establish a correlation between the wetting characteristics and the chemical structure and physical properties of the adhesives. The effect of the morphology of cork on the interfacial properties was also investigated. The initial contact angles were related to the chemical nature of the adhesive. The kinetics of the wetting process were found to depend mainly on the viscosity of the adhesive.

Scanning electron microscopy observations of insulation cork agglomerates

Observations by scanning electron microscopy were made of insulation cork agglomerates and of cork raw material. The insulation cork agglomerates are agglomerates of granules of cork from the cork-oak tree (Quercus suber), self-bonded and expanded by autoclave steaming at approximately 300°C and 40 kPa. In this process, the cork cells expand by unfolding the cell wall corrugations and by stretching the cell walls (concurrently decreasing the cell wall thickness). In the junctions between granules, the cells are compressed against each other and collapsed; the region of cell collapse is restricted to a limited number of cell layers at the boyndary between the granules. The cell wall material is thermochemically degraded and a weight loss of approximately 30% of the cork material is observed in the production of these insulation agglomerates.