New alternatives for wood preservation based on thermal and chemical modification of wood— a review

International audienceAbstractKey messageIncreasing environmental pressures appearing over the last few years have led to important changes in the field of wood protection. In this context, new technologies, based either on thermal or chemical modifications, suggest increasing interest in prospect of programmed ban of biocide products.• ContextThe evolution of the regulations on the use of biocide products has led to important changes in the field of wood preservation, leading to an increasing interest for non-biocide treatments like thermal or chemical modifications to face to the programmed ban of biocide products.• AimsThe paper reviews the different non-biocide alternatives developed currently on an industrial scale, highlighting their main characteristics and applications.• ResultsDifferent treatments have been developed on an industrial scale involving mainly thermal modifications and acetylation, furfurylation and DMDHEU constituting already available solutions.• ConclusionDifferent non-biocide alternatives already exist and will become more important in the next decades due to the increasing legislative pressure driven by environmental considerations

Characterization of extracts from the bark of the Gabon hazel tree (Coula edulis baill) for antioxidant, antifungal and anti-termite products

Chemical composition of the bark extracts ofCoula eduliswas inves-tigated tofind potential antioxidant, anti-termite and antifungal compounds whichcanfind useful applications in thefields of food, nutraceuticals, cosmetics or agro-chemical. Phytochemical screening revealed the presence of several groups ofactive molecules such as alkaloids, polyphenols,flavonoids, saponins and sterolsand/or terpenes in the different extracts. Total phenols, condensed tannins andfla-vonoids contents corroborated phytochemical screening. Gas chromatography-mass spectrometry (GC-MS) analysis revealed compounds in dichloromethaneextract different from those obtained with all the other solvents. Hexadecanoicand trans-9-octadecenoic acids, as well as stigmasterol andβ-sitosterol have beenidentified as the major compounds in the dichloromethane extract. Extractsobtained with acetone and toluene/ethanol mixture (2/1, v/v) indicated the pre-sence of few amounts of fatty acids and sugars, catechin in small amount andhuge amounts of phenolic acids like gallic and ellagic acids. The radical 2,2-diphenyl-1-picrylhydrazyle (DPPH) and the cationic radical 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS+) were used for evaluation of antioxidantproperties of the different extracts. The dichloromethane extracts had a very lowantioxidant activity, while acetone and toluene/ethanol extracts presented EC50values similar to those of catechin and BHT used as reference antioxidant com-pounds. Effect of the different extracts of the bark ofC. edulison fungal growthinhibition indicated better inhibition of the mycelium growth of brown rot fungicompared to white rot fungi. Low anti-termite activities were recorded with theaqueous extracts, while stronger activities were recorded with dichloromethane,acetone and toluene/ethanol extracts

Outcome of life-threatening malaria in African children requiring endotracheal intubation

BACKGROUND: Little is known about children undergoing critical care for malaria. The purpose of this survey was to evaluate the outcome in African children requiring endotracheal intubation for life-threatening malaria. METHODS: All children with a primary diagnosis of severe malaria (2000 WHO definition) requiring endotracheal intubation, hospitalised over a five-year period, within a tertiary-care hospital in Dakar, Senegal, were enrolled in a retrospective cohort study. RESULTS: 83 consecutive patients were included (median PRISM h(24 )score: 14; IQR: 10–19, multiple organ dysfunctions: 91.5%). The median duration of ventilation was 36 hrs (IQR: 4–72). Indications for intubation were deep coma (Glasgow score ≤7, n = 16), overt cortical or diencephalic injury, i.e, status epilepticus/decorticate posturing (n = 20), severe brainstem involvement, i.e., decerebrate posturing/opisthotonus (n = 15), shock (n = 15), cardiac arrest (n = 13) or acute lung injury (ALI) (PaO(2)/FiO(2 )<300 Torr, n = 4). Death occurred in 50 cases (case fatality rate (CFR), 60%) and was associated with multiple organ dysfunctions (median PELOD(h24 )scores: 12.5 among non-survivors versus 11 among survivors, p = 0.02). Median PRISM(h24 )score was significantly lower when testing deep coma against other indications (10 vs 15, p < 0.001), ditto for PELOD(h24 )score (2.5 vs 13, p = 0.02). Multivariate analysis identified deep coma as having a better outcome than other indications (CFR, 12.5% vs 40.0 to 93.3%, p < 0.0001). Decerebrate posturing/opisthotonus (CFR 73.3%, adjusted relative risk (aRR) 10.7, 95% CI 2.3–49.5) were associated with a far worse prognosis than status epilepticus/decorticate posturing (CFR 40.0%, aRR 5.7, 95% CI 1.2–27.1). Thrombocytopaenia (platelet counts <100,000/mm(3)) was associated with death (aRR 2.6, 95% CI 1.2–5.8) and second-line anticonvulsant use (clonazepam or thiopental) with survival (aRR 0.4, 95% CI 0.2–0.9). Complications, mostly nosocomial infections (n = 20), ALI/ARDS (n = 9) or sub-glottic stenosis (n = 3), had no significant prognostic value. CONCLUSION: In this study, the outcome of children requiring intubation for malaria depends more on clinical presentation and progression towards organ failures than on critical care complications per se. In sub-Saharan Africa, mechanical ventilation for life-threatening childhood malaria is feasible, but seems unlikely to dramatically improve the prognosis

Synthesis and Characterization of Poly(hydroxy)urethane from Polyols for Beech (Fagus sylvatica) Wood Impregnation

A non-isocyanate route of polyurethane synthesis based on polyol (xylitol, sorbitol, glycerol, and PG3), alkyl carbonate (DMC and DEC), and diamine (HMDA, EDA, and DETA) was conducted for wood impregnation through in-site polymerization. The structure and mass average molecular weight (Mw) of the polyurethanes were analyzed using FTIR, NMR, and SEC. According to the results, polyurethane synthesis by a two-pot method in water brought cyclic carbonate degradation. The distribution of Mw of the polyurethanes showed that the most satisfying polymer (4380 g/mol) was prepared without solvent. Polyurethanes synthesized in methanol have a higher Mw than that in distilled water. In the same solvent, the use of HMDA resulted in a polymer with higher Mw than that of EDA. One-step wood impregnation in a solvent gave unsatisfactory WPG (12.59–19.71%) and LC (50.36–62.80%). However, one-step impregnation without solvent gave a higher WPG (78.39–87.63%) and a lower LC (19.11–21.25%). It is not feasible to be applied industrially. The two-step impregnation gave WPG (14.89-30.73%) and LC (42.22–56.52%). Wood impregnation using methanol or ethanol as the solvent was more recommended than using an aqueous solution. However, the resistance against leaching needs improvement. Keywords: Alkyl carbonate, diamine, polyol, polyurethane, wood impregnatio

Characterization of thermally modified short and long rotation teaks and the effects on coatings performance

Many wood processing industries use short rotation teak, which has lower quality especially in durability and dimensional stability. Heat treatment is an eco-friendly method to improve dimensional stability and durability of wood. The objectives of the study were to investigate the effects of thermal modification on chemical composition, colour, dimensional stability and durability as well as coating’s performance after accelerated weathering of short and long rotation teak for exterior utilization. In this study, the samples were heated in oven at 220 °C for 20 h under nitrogen atmosphere. Results showed that independently of growth conditions teak woods underwent hemicelluloses degradation and an increase of lignin content after heat treatment. Extractives contents were lower in short rotation than in long rotation teak, and decreased in all cases after heat treatments. Dimensional stability was considerably improved as indicated by anti-swelling efficiency values of 64.9% and 58.9% for short and long rotation teak, respectively. Heated teak woods were more resistant against Trametes versicolor and the durability of short-rotation teak increased from moderate to very durable. Coatings on heat treated teaks had better bonding quality and better photo-stability when compared to unheated. Heated short rotation teak could be considered for exterior application

Total phenolic and lignin contents, phytochemical screening, antioxidant and fungal inhibition properties of the heartwood extractives of ten Congo Basin tree species

International audienceAbstract Key messageContent and type of extractives vary considerably among woody species in the Congo Basin tropical forest. They influence the natural durability of wood with respect to fungal and insect degradation. Species containing higher amounts of extractives and Klason lignin were generally less susceptible to fungal colonization. Phenolic extractives with large anti-fungal and high antioxidant activities were the main chemical family of compounds extracted from the tested species, which suggests a potential chemical valorization of these extractives.ContextSeveral woody species from the Congo Basin are known for their natural durability, but the causes of this natural durability are not always fully elucidated. This is particularly the case for the resistance to white rotting fungi decay.AimsThe chemical composition as well as the antioxidant activity of the heartwood extractives of several species were quantified and correlated to the ability of different fungi to colonize wood sawdusts in order to better understand their decay resistance.MethodsThe chemical screening of extracts was conducted using colorimetric methods. The quantity of lignin, extracts and total phenolic compounds, as well as antioxidant activities were determined. Extracted and unextracted heartwood sawdusts were exposed to two white rot fungi to assess the effect of extractives on their colonization.ResultsExtractives and lignin contents ranged from 2.7 to 16.0 % and from 26.5 to 35.9 %, respectively. Antioxidant activity was directly connected to total phenolic contents. The phytochemical screening revealed the presence of different chemical groups in all extracts. Resistance to fungi was correlated to the amount of extractives and in most cases to the lignin content.ConclusionPhenolic compounds associated with antioxidant activities influenced the natural resistance of heartwood

Anti-fungal and anti-termite activity of extractives compounds from thermally modified ash woods

Thermal modification of wood is a promising alternative to chemical and biocidal modification processes, increasing the biological durability and dimensional stability of wood. However, the wood-decay resistance properties of heat-treated wood are still not well known. The main objective of this study was to determine the biological resistance of heat-treated ash wood, and assess the antifungal and anti-termite activity of extractive compounds from heat-treated ash woods, depending on the intensity of the modification process (2 hours at 170, 200, 215, 228 (°C) - steam pressure). Untreated and heat-treated wood samples were extracted with water or acetone. The extracts were then used to determine inhibition effectiveness against white-rot (Trametes versicolor) and brown-rot (Rhodonia placenta) fungi. Whatman papers impregnated with extractives were used to evaluate the inhibition of termite feeding. Lastly, the extractives were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS) and compared for their level of anti‑termite and antifungal activity. The results showed that the degree of antifungal activity of these extracts depended on the solvent used during the extraction process and varied depending on heat treatment intensity. The extracts were more effective against brown-rot than white-rot fungi. However, the anti-termite activity of heat-treated ash wood extracts was not really significant. A GC-MS analysis showed that the main share of the extractives in untreated wood was removed. In addition, new chemical elements were generated by the thermal degradation of wood polymers (lignin and hemicelluloses), including aliphatic acids, monosaccharides and other products resulting from their dehydration reaction. The most abundant element was syringaldehyde, from lignin derived compounds, which might explain the antifungal activities of thermally treated ash wood extracts

Improvement of the durability of heat-treated wood against termites

Thermal modification is an attractive alternative to improve the decay durability and dimensional stability of wood. However, thermally modified wood is generally not resistant to termite attacks, limiting the field of application of such materials. One way to overcome this drawback is to combine thermal modification treatment with an additional treatment. One such treatment is the impregnation of a boron derivative associated with appropriate vinylic monomers, which takes advantage of the thermal treatment to polymerise these monomers for boron fixation. Using this strategy, we recently showed that an impregnation of borax (2 or 4% boric acid equivalent) dissolved in a 10% aqueous solution of polyglycerolmethacrylate followed by thermal treatment under nitrogen at 220°C protects wood from both termite and decay degradations, even after leaching. Additionally, wood samples treated with a 10% polyglycerolmethacrylate aqueous solution and subjected to thermal treatment at 220°C presented improved resistance to termites while avoiding boron utilization. Based on these results, we investigate the effect of impregnation with two types of vinylic monomers, which are already used in the presence of boron, followed by thermal treatments at different temperatures. We evaluate termite and decay durability of wood to evaluate if thermal modification associated with light chemical modification could be a solution for utilization of thermally modified materials in termite-infested areas