Chemical characterization and the effect of a polyherbal varnish coating on the preservation of Ayous wood (Triplochiton scleroxylon)

Abstract

Research on the potential of natural substances to improve the durability and preservation of the physical properties of wood is nowadays an important concern. The objective of this work was to characterize and evaluate the effect of an ecological varnish formulated from Jatropha curcas seed oil and vegetable resins on the improvement of the resistance to biodeterioration agents (fungi and termites) and the preservation of the physical properties of Ayous wood. The varnish was formulated and characterized before being tested on Ayous wood. The properties of the formulated varnish (FV) were compared with those of a reference varnish (RV). The density of the FV was 0.99, while that of the RV was 1.6. FV showed better absorption (0.63) compared to 0.03 for RV, while the transmittance of RV was 94.5 % compared to 23.7 % for FV. The MALDI results showed that the FV contains oleic, linoleic, stearic, and palmitic acids probably from Jatropha curcas and unsaturated fatty acids from the resin of Aiélé (Canarium schweinfurthii, Engl.), such as 2-methyl-5-propan-2-yl cyclohexa-1,3-diene, 1-methyl-4-propan-2-yl cyclohexa-1,4-diene, (1 R,4 S,6 S)− 4,7,7-trimethylbicyclo [4.1.0] hept-2-ene. Catechin oligomers reacted with one molecule of 2-[(1 S)− 4-methyl cyclohex-3-en-1-yl]propan-2-ol were also detected, these derived from the reaction of the Vachellia nilotica tannin extract hardener with one of the main components of the Aiélé resin. Some resinite oligomers derived from the added rosin were also identified. All these significantly reduced the water absorption of the wood. The application of FV changed the color parameters of Ayous more than RV. RV showed a glossiness of 60GU (Glossines Unit), against 35GU for FV. According to ISO/CIE 11664–6 norm, Ayous wood was significantly protected against atmospheric aggression with ∆E * <4 after 4 months of exposure. All varnishes significantly protected the wood against all fungi tested with a mass loss of less than 5%. Finally, FV was more protective for Ayous wood against termites with a mass loss of 2 % against 40 % for RV. FV is an effective alternative for the preservation of Ayous wood and possibly other wood species.