J.E.G. van Dam

Wood preservation by low-temperature carbonisation

Pine (Pinus sylvestris L.) wood with dimensions (100 x 10 x 10mm) was thermally treated at 275degreesC in a muffle oven to impart resistance to microbial degradation. Low-temperature carbonised pine resulted in a visually homogeneously treated product with a substantial (about 70% w/w) reduced non-cellulosic carbohydrates content, as compared with untreated pine. These components have been removed or have been partly converted into hydrophobic polymerisation products, which results in reduced water absorption in air of different relative humidity (RH) for carbonised pine. The flexural strength at high RH and after immersion in water of carbonised wood is comparable with untreated and creosote impregnated wood. However, at lower RH the carbonised wood is less strong. Only trace amounts of polycyclic aromatic hydrocarbons (PAHs) and other phenolic compounds could be detected both in water leached from carbonised wood and untreated wood. Furans, mainly 5-hydroxymethylfurfural, have been demonstrated to leach in substantial amounts in the water from carbonised pine. An accelerated decay test in soil showed that low-temperature carbonisation of pine resulted in a product with considerably enhanced durability, as compared with untreated wood. Resistance of carbonised wood against environmental decay was similar or even better than creosote impregnated wood

Improved method for fibre content and quality analysis and their application to flax genetic diversity investigations

Abstract Evaluation for fibre content and quality in a breeding selection program is time consuming and costly. Therefore, this study aims to develop a method for fast and reproducible fibre content analysis on small flax straw samples. A protocol has been developed and verified with fibre screening methods used commonly in flax breeding. A large number of different accessions of mostly fibre flax and some linseed, present in the core collection of CGN, were grown under comparable conditions and were analysed for their bast fibre contents by warm water retting and green decortication methods. From the core collection, a selection was made of a number of high, medium and low fibre yielding flax accessions with extremes in stem length, branching or fibre bundle appearance. These were analysed with the novel fibre extraction procedure utilising short autoclave treatment in 0.05 M EDTA as calcium complexing agent. Since 1999, cultivars selected for the core were grown around Wageningen on sandy soils. The fibre content was determined by different methods and a correlation was found between the values obtained by warm water retting and the autoclave procedure. However, the data obtained by green decortication show up to 20% and on average 15% higher fibre content values. This higher value roughly corresponds to the weight of the cuticula and remaining xylem tissue that is more efficiently removed by retting and autoclave treatments. The reproducibility of this fibre content determination method for small straw sample analysis (25 g) is a promising tool for accelerated breeding protocols.

Alkaline Swelling of Hemp Woody Core Chips

Abstract Swelling of hemp woody core chips after alkaline (peroxide) impregnation at 70 °C, as is practised in alkaline peroxide mechanical pulping (APMP) processes is examined, in relation to pulp yield and chemical composition of the chips. In contrast to wood chips, maximum swelling is attained at elevated temperature (70 °C) without chemical treatment, possibly as the result of relatively high porosity of hemp woody core cell walls. Alkaline swelling at 70 °C correlates with the xylan:lignin ratio. Swelling at ambient temperature shows some correlation with acidic group content. Apparent pore size distributions were examined, using 1H NMR spin-spin relaxation. Several apparent pore size distributions could be distinguished within each sample. Elevated temperature, NaOH and peroxide addition are influencing apparent pore size distribution and total pore volume differently. Addition of peroxide results in remarkably enlarged apparent pore sizes, which emphasizes its importance (apart from bleaching) in ...