PF-bonded particleboards from AKD-modified chips

Alkyl ketene dimer (AKD) was used as a hydrophobic agent for PF-bonded particleboards. In contrast to conventionally used paraffin, AKD can be covalently bonded to the chip surface by esterification with wood hydroxyl groups. FTIR analyses before and after toluene extractions indicated that only a small amount of the applied AKD is chemically bonded. Wettability studies on veneer strips suggested that particularly the bonded AKD accounts for the surface hydrophobicity. A subsequent spraying of AKD and PF resin on the chips that were pressed for 15, 30, and 60 s?mm^-1 (Process 1) did not result in decreased thickness swelling and water uptake as compared to the control boards. In Process 2, chips were cured (130 °C/6, 12, 24 h) prior to pressing (15 s?mm^-1) which did not impart significant hydrophobicity either. The low efficacy of AKD as hydrophobic agent in Process 1 is attributed to the hydrolysis of AKD by water vapor during pressing. The low hydrophobic effect of AKD in Process 2 is ascribed to a saponification of esters between AKD and wood hydroxyl groups by the alkaline PF resin.     

Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece

In this study, four samples of essential oils obtained from plant species with a wide distribution in Greece and economic importance for the world-wide spice market and also carvacrol and thymol were tested for their possible antioxidant activity. The four plant species wereOriganum vulgare subsp.hirtum, O. onites, Coridothymus capitatus andSatureja thymbra. The essential oils were chemically characterised by gas chromatography-ion trap detection. All the essential oils examined and also carvacrol and thymol were found to have antioxidant activity when tested on TLC plates and by measuring peroxide values of lard stored at 35° C. The results indicate that the antioxidant effect may be related to the presence of carvacrol and thymol in essential oils.     

Some physical properties of sweet chestnut wood grown in Greece

Dises from twenty trees ofCastanea sativa Mill from two stands (Arnea and Morna) were taken at breast height, 5 m and the beginning of crown (crown base). These wood samples were examined for wood density, shrinkage and growth rate. Overall basic density was 0.486 g/cm³ on average at breast height, 0.522 g/cm³ at 5 m height and 0.542 g/cm³ at crown base. Shrinkage to oven dry condition was 0.20% longitudinally, 4.14% radially and 7.15% tangentially, at breast height, 0.19%, 4.47% and 7.33% at 5 m level and 0.20% 4.46% and 7.30 at crown base. The growth rate averaged 2.68 mm/ring at breast height, 2.58 mm/ring at 5 m level and 2.46 mm/ring at crown base.     

Essential oils of the twigs of some conifers grown in Greece

Pinus sylvestris L.), Black pine (P.nigra Arnold) and Fir (Abies Borisii – Regis (Abies alba × A. cephalonica) Mattfeld), grown in natural stands in Greece was investigated. The compounds were identified by GC/MS analysis. The Scots pine oil was found to be rich in α-pinene (19.44%), β-pinene (17.27%), myrcene (14.00%) and β-phellandrene (29.14%). The Black pine oil was also rich in α-pinene (10.38%), β-pinene (15.45%), myrcene (3.99%), β-caryophyllene (4.03%) and citronellol (14.97%), while the Fir oil was rich in α-pinene (3.30%), β-pinene (2.57%), limonene (46.45%), junepene (2.55%) and caryophyllene oxide (7.05%). The mean twig oil yield on dry weight basis was 0.52%, 0.36% and 0.48% for Scots pine, Black pine and Fir respectively.     

Formaldehyde emission from particleboards manufactured with waste materials from plywood industry

Peeling cores, dried veneer residues and plywood edge pieces containing adhesive are used for particleboard production. So, in this study, the effect of waste materials from plywood industry used for particleboard manufacturing on the formaldehyde emission of panels was investigated.     

红麻和麦草制碱性过氧化氢机械浆

本文介绍了用麦草和红麻为原料，采用碱性过氧化氢预处理随后磨浆（P-RC）的APMP制浆流程和方法。     

Steady and unsteady state moisture movement in particleboards

The physical parameters, such as steady state and unsteady state diffusion coefficients, of moisture movement in particleboard are very important for modelling the moisture movement process and preventing the deformation of particleboards. The methods of determination of steady state and unsteady state diffusion coefficients were studied and the results of those determined coefficients obtained. The results demonstrated that the steady state diffusion coefficients parallel to panel surface were 10–20 times as large as those perpendicular to panel surface and unsteady state diffusion coefficients parallel were 3–5 times as large as those perpendicular to panel surface in test particle-boards. This was due to the orientation of chips in the particle-boards.     

Release of acetic acid and formaldehyde from particleboards bonded with phenolic resins

The gas analysis method (EN 717-2:1994), originally destined for measuring the formaldehyde release from wood-based panels, can also be used to determine the emanation of volatile organic acids such as acetic acid. However, the profile of release of formaldehyde and acetic acid seems to be quite different in the course of the gas analysis test.     

Procedural influence on the properties of particleboards made from AKD modified chips

Wood chips were treated with alkyl ketene dimer (AKD) using three different processes to impart water resistance to particleboards. In the first process, AKD was blended with UF resin. Thickness swelling and water uptake after a 24 h immersion period (20 and 69%) were lower than in the control boards (28 and 81%) but were higher than in the paraffin references (10 and 22%). In process 2, AKD and UF resin were sprayed separately on the chips resulting in a greater reduction of thickness swelling (15%) and water uptake (49%) than in process 1. Paraffin references revealed a thickness swelling and water uptake of 7 and 25%, respectively. An extension of the pressing time in processes 1 and 2 did not increase water repellence. In process 3, particleboards were made from AKD-treated chips that were cured at 130 °C (24 h) prior to gluing. They showed a thickness swelling of 7% and a water uptake of 25%, whereas particleboards with paraffin exhibited levels of 8 and 29%. The thickness swelling and water uptake of boards with AKD increased when the curing time was reduced from 24 to 12 to 6 h (130 °C). Changing the curing temperature from 130 to 100 °C (12 h) had no effect on board properties. The IB of boards made from pre-cured chips with AKD (24 h/130 °C) was 44% lower than in controls and 35% lower than in paraffin references. This indicates that AKD impedes the adhesion.     

Modelling of the moisture transfer process in particleboards

There were a number of studies on moisture transfer modelling of wood, but no systematic study for moisture transfer in particleboard with respect to usage or storage. The physical parameters of four kinds of particleboards were determined in this study. The unsteady-state diffusion coefficients and surface emission coefficients of moisture in particleboards were separated in one experimental period by using the method of linear regression. Then the moisture transfer processes in particleboard were analysed by using Finite Element Method (FEM), and the moisture absorption processes of four kinds of particleboards were observed experimentally. By comparing the computed results with the experimental results, it showed that the error was within 10%. Therefore, we came to the conclusion that the processes of moisture transfer in particleboard can be described by using FEM:     

越南利用红麻生产商品BCTMP

木材资源短缺、能源价格持续上涨、面临环保压力、纸和纸板产品的需求量不断攀升等一系列问题都将对制浆造纸业在未来数年的发展提出挑战。面对这些问题,造纸企业无疑将提出新的发展策略,以满足纸和纸板产品的需求,其着重点主要是对可用纤维原料的合理利用以及生产工艺和环境保护的相互协调。     

The influence of scavengers on VOC emissions in particleboards made from pine and poplar

This paper studies the performance of scavengers on Volatile Organic Compound (VOC) emissions from wood-based composites. Particleboards made from maritime pine (Pinus pinaster Ait.) and European poplar (Populus spp.) were produced with a UF resin doped with melamine and two scavengers, sodium metabisulfite and urea. VOC emission was measured according to EN ISO 16000. Particleboards made from pine present much higher total VOC (TVOC) emissions than boards made from poplar. Pine emits a higher amount of terpenes, but also aldehydes, acids and terpenoids, while poplar emits mainly acetic acid. Sodium metabisulfite showed an excellent ability to reduce aldehydes emission, which represents nearly 50 % of total emission of particleboards made from pine. When sodium metabisulfite was applied to particleboards made from poplar, reduction of TVOCs was not significant due to the low contribution of aldehydes to TVOCs. Urea presents a low reduction in TVOCs for both wood species.     

Natural durability in ground stake-test of propionylated particleboards

Zusammenfassung One layer particleboards were made from wood chips modified with propionic anhydride to 12.2% propionyl content. Propionylated stakes were tested in ground contact in Western Greece. Each stake was placed in such a way that half of the stake was below the ground line. After three years of testing, results showed that propionylation provides excellent protection against fungal attack.     

Construction particleboards made from rapeseed straw glued with hybrid pMDI/PF resin

The paper investigates the possibility of manufacturing rapeseed particleboards (RPB) which could be used as construction material in eco buildings. Therefore, single-layer particleboards were produced from rapeseed straw particles glued with mixture of 4.4′-methylenediphenyl isocyanate (pMDI) and phenol–formaldehyde (PF) resins in the weight ratio 70:30 (hybrid pMDI/PF resin). The boards were manufactured with density of 650, 600, 550, 500 and 450 kg/m³. Next, their physico-mechanical properties were determined, i.e. modulus of rupture, modulus of elasticity, internal bond and internal bond after the boil test (V-100) and thickness swelling after 24 h soaking in water. The thermal conduction coefficient (λ) and sorption properties in changeable relative humidity conditions were also determined. Based on the obtained results, it was found that rapeseed straw may be a valuable material used in the production of construction particleboards which meet high strength requirements. Boards with density of 650 kg/m³ meet the requirements of EN 312 standard for type P7 boards. It is also possible to decrease their density to 600 kg/m³ (type P5 boards) and even 550 kg/m³ (type P3 boards). However, rapeseed particleboards are characterized by relatively high values of thickness swelling after 24 h of soaking in water. The weaker resistance to humidity has also been confirmed by tests on sorption and desorption of vapour in changeable relative humidity conditions. Nonetheless, an important advantage of these boards is the fact that they are characterized by better thermal insulation than particleboards.     

Managing declining yields from ageing tea plantations

Strong growth in the demand for tea requires further increases in the productivity of plantations. Declining or stagnant yields are commonly observed in older plantations. Possible controlling factors for yield decline are reviewed including ageing of plants, chronic disease and sub‐optimal soil conditions such as excess soil acidity and low soil organic matter. Management options for addressing these factors are evaluated, including replanting. A systematic approach to decision‐making about replanting is presented. Practice for replanting is reviewed and it is concluded that evidence to support a general case for replanting is limited, unless based on the introduction of more productive clones and/or better plant spacing. © 2013 Society of Chemical Industry     

Sonosynthesis of Microcellulose from Kenaf Fiber: Optimization of Process Parameters

Green composites using cellulose fibers as a reinforcement material provide a sustainable and renewable alternative to petroleum-based polymers. However, controlling the usage of chemicals and processing parameters to extract the cellulose could be sometimes difficult. Therefore, this study aims to optimize the conditions for extracting the microcellulose from kenaf fibers using central composite design (CCD), a statistical tool in design of experiments. Three factors and three levels were chosen for carrying out the analysis. The design was based on sodium hydroxide (NaOH) dosage, Sodium Chlorite (NaClO₂) dosage and sonication time as independent variables, while dependent variables were the fiber size and degradation point. Later, size responses were fitted using quadratic polynomial model and degradation responses using 2-factor interaction model (2FI). The R² values of 0.89 and 0.83 were obtained for the quadratic and the 2FI model, respectively. Further, surface morphology, thermal analysis, Fourier transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD) were also used for design validation. Optimal parameters for microcellulose extraction were found to be 0.15 g of NaOH at first stage, 4.6 mL of NaClO₂ at second stage, and 10 min of sonication during third stage.