Abstract
The service life performance of timber products exposed to natural weathering is a critical factor limiting the broad use of wood as an external building element. The goal of this study was to investigate the in-service characterization of an innovative biofinish coating system. It is a novel surface finishing solution based on the bioinspired concept of living fungal cells designed for effective wood protection. The performance of Scots pine (Pinus sylvestris L.) wood coated with biofinish was compared with uncoated references. Samples were exposed to natural weathering for 12 months under the climatic conditions of northern Italy. The visual appearance, colour, gloss, wettability, and 3D surface topography of the wood surface were examined. Results revealed that the total colour changes (∆E) of biofinish-coated wood were negligible. Untreated Scots pine wood revealed the changes in colour after just three months of exposure. The gloss changes of both surface types were small. The contact angle measured on biofinish-coated wood was higher compared to that of uncoated Scots pine. Surface roughness increased in uncoated wood due to the erosion effect caused by the weathering progress. Conversely, the surface roughness of biofinish-coated samples decreased along the exposure time. This phenomenon was explained by two self-healing mechanisms: migration of non-polymerized oil to the cracked surface, where it polymerizes and creates a closed layer, and local regrowth to cover damaged spots by living fungal cells present in the coating. The obtained results revealed the superior aesthetic performance of the biofinish surface treatment against natural weathering. By considering the fully bio-based nature of the investigated coating, it was concluded that this solution can be an attractive alternative for state-of-the-art wood protection technologies.
Highlights
Weathering is the general term used to describe the slow degradation processes that occur when the material is exposed to the outdoor environment [1,2,3]
The service life performance of timber products exposed to natural weathering is a critical factor limiting the broad use of wood as an external building element
Surface roughness increased in uncoated wood due to the erosion effect caused by the weathering progress
Summary
Weathering is the general term used to describe the slow degradation processes that occur when the material is exposed to the outdoor environment [1,2,3]. The development of bio-concrete (where limestone-producing bacteria are activated when a crack occurs) [40] as well as bio-coatings (where living moulds are re-grooving on a wooden surface after damage) provides a pioneering proof of concept for bioinspired solutions demonstrating the novel capacities of building materials [41]. Biofinish technology represents such a bioinspired and environmentally friendly wood treatment solution. A special focus was directed toward the assessment of the alteration of appearance and aesthetical properties, to be evaluated with an objective multi-sensor approach and confronted with a reference timber product frequently used in a similar configuration
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