Weathering of chemically modified wood

Acctylation of radiata pine vencer was shown to improve the colour stability and weathering resistance of material exposed to accelerated weathering conditions. Two exterior finishes, an opaque acrylic stain and a semi-transparent alkyd stain, as well as unfinished veneer, were studied. Significantly less checking was observed for unfinished, acetylated samples or acetylated vencers finished with the alkyd stain when compared with untreated controls. Examination of unifinished samples by scanning electron microscopy (SEM) showed that, although checking was not completely prevented by acetylation of the vencer, it gave significant protection from the effects of weathering.     

Weathering of chemically modified wood

The weathering characteristics and microscopic structure of unfinished acetylated and untreated radiata pine are reported. Samples were exposed outdoors over 28 weeks in Rotorua, New Zealand. Acetylated veneer had improved checking resistance when compared with untreated veneer, confirming results of a previous study on accelerated weathering of untreated and acetylated veneer. Colour changes of naturally weathered untreated and acetylated veneer were very different to that of artificially weathered veneer. Acetylated veneer was only slightly less grey than untreated veneer after 28 weeks' natural weathering.     

Bonding behaviour of chemically modified wood particles for board production

The objective of this paper was to evaluate the bonding behaviour of chemically modified wood particles towards an isocyanate resin system, as determined from internal bond strength of the board, and to determine which resin system, isocyanate or formaldehyde is suitable for use in boards made from modified raw material. It was found that chemical modification of wood chips and strands did not significantly affect the bonding efficiency of isocyanate resin, but the bonding efficiency of formaldehyde resins was strongly influenced. This behaviour can be a consequence of the usage of a less pH dependent resin that is fully cured during hot pressing in combination with the high mobility of the resin which causes penetration to considerable depth into compressed particles repairing weak zones, which are created during the modification process as chips are exposed to elevated temperatures, by sticking them together. It is suggested therefore, that the isocyanate resin system is more suitable for use in boards made from modified raw material than the formaldehyde resin system.     

Soft purification of lampante olive oil by microfiltration

An efficient membrane-based process for deacidification of lampante olive oil was investigated. The neutralization of the free fatty acids with appropriate soda concentration allows the formation of submicronic particles which are subsequently removed by a microfiltration technique. A total or quasi-complete neutralisation of the acidity is necessary to achieve the complete retention of the soap molecules. Partial neutralization of the acidity leads to a lower membrane separation efficiency. The residual FFA causes permeation of soap molecules across the membrane. When filtered under suitable conditions, lampante olive oils show excellent quality characteristics, i.e., very low residual acidity as well as soap and water contents. The initial fluxes, obtained during crossflow filtration with membrane pore sizes 0.5 and 0.8 μm (147 and 212 l/h m², respectively) after neutralization with 20% NaOH are twice those obtained with 40% NaOH while there is only a slight improvement with the 0.2 μm membrane. The filtered oils show good quality (acidity and residual soaps) in the case of PS 0.2 and 0.5 μm, whereas the 0.8 μm membrane allows some soaps to pass through the membrane. The passage from the laboratory scale (1 kg) to a 50 kg unit shows the practical possibility of scaling up without meeting any particular problems or loss of efficiency.     

Utilisation of textile wastes for the production of geotextiles designed for erosion protection

Textile waste was used for production of thick ropes designed for the protection of slopes against sliding and erosion. For the production of ropes, scraps of insulating materials produced from poor quality wool and scraps of nonwoven manufactured from blend of recycled fibres were applied. The ropes were installed on the slope in a disused gravel pit. Stabilisation of the slope and behaviour of the materials used were analysed during two vegetation seasons. Investigations confirmed the usefulness of the technology for the protection of steep slopes.     

Characterisation of thermally modified wood: molecular reasons for wood performance improvement

Relatively mild thermal treatments of wood according to a two step process which leads to improved dimensional stability and improved timber performance were investigated by solid phase CP-MAS 13C-NMR to understand at molecular level the reasons for the improvements reported. All the occurrences described appear to be the consequence of reactions which are known in wood chemistry. These are the formation of acetic acid liberated from the hemicelluloses, which further catalyses carbohydrates cleavage, causing a reduction of degree of polymerisation of the carbohydrates. Acid catalysed degradation results in the formation of formaldehyde, furfural and other aldehydes as well as some lignin cleavage at Cα and O4 and believed to cause some aldehyde production from lignin units Cγ, all occurring in the first reaction step. Lignin autocondensation through the cleaved, positively charged benzylic Cα to form some methylene bridges presumably starts already to occur in this first phase. The increase in the number of free reactive sites on the aromatic ring of some lignin units already occurs in this phase but continues into the next. In the second treatment step completion of the autocondensation of lignin is believed to occur through the formation of methylene bridges connecting aromatic rings. The aromatic nuclei sites are released by demethoxylation and through the cleaved, positively charged benzylic Cα. Reactions of some of the aldehyde groups formed in the first step phase occur with lignin aromatic nuclei sites to connect aromatic rings through methylene bridges. The extent of these reactions is mild, but nonetheless they lead to an increase in cross-linking with consequent improvement in dimensional stability and decreased hygroscopicity of wood.     

Determination of surface area and pore volume of holocellulose and chemically modified wood flour using the nitrogen adsorption technique

Very low surface area (ca. 0.5 m²/g) and a low pore volume (ca. 0.002 cm³/g) have been obtained for oven dried wood, using the nitrogen adsorption technique. The microporous structure of wood flour was partially preserved by the solvent exchange drying (SED) employed in this study, in particular when toluene was used as a final solvent. However, the resulted surface area (ca. 6 m²/g) and a pore volume values (ca. 0.015 cm³/g) indicated that such a structure is in no way representative of a fully swollen cell wall. By using solvent exchange drying (SED), it is possible to preserve the swollen pore structure of holocellulose samples. However, with samples which contain significant amounts of lignin, such as native wood, it is not possible to prevent re-collapse of the pores. This problem arises because as micropore swelling occurs, the surrounding lignin network of the cell wall is stretched. When the molecules occupying the micropores are removed, the lignin returns to its original configuration, re-collapsing the micropores in the process. Chemical modification resulted in significant reduction in surface area and pore volume, possibly a result of pore blocking by the large acyl group.

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Bestimmen der inneren Oberfläche und des Porenvolumens von Holocellulose und chemisch modifiziertem Holzmehl mit Hilfe der Sickstoffadsorptions-Methode

Zusammenfassung Sehr geringe Oberflächenanteile (ca. 0,5 m²/g) und Porenvolumina (ca. 0,002 cm³/g) wurden in ofengetrocknetem Holz mit Hilfe der Stickstoffadsorptios-Methode gefunden. Die Mikroporenstruktur in Holzmehl blieb nach Trocknen durch Lösemittelaustausch (SED) teilweise erhalten, insbesondere, wenn Toluol als letztes Lösemittel verwendet wurde. Allerdings zeigen die gemessenen Oberflächen (ca. 6 m²/g) und Volumina (ca. 0,015 cm³/g), daß solche Strukturen keineswegs den Verhältnissen in der gequollenen Holzzellwand entsprechen. Bei Holocellulosen kann die Porenstruktur des gequollenen Zustands nach Lösemittelaustausch erhalten werden. In Proben, die beträchtliche Mengen an Lignin enthalten, wie ursprüngliches Holz, ist es jedoch nicht möglich, den Kollaps der Poren zu verhindern. Das Problem ergibt sich dadurch, daß aufgrund des Quellens der Mikroporen das umgebende Lignin-Netzwerk der Zellwand gestreckt wird. Wenn die Lösemittel-Moleküle in den Mikroporen durch Trocknen entfernt werden, kehrt das Lignin in die ursprüngliche Konfiguraton zurück und verschließt so die Mikroporen wieder. Chemische Modifizierung hatte eine beträchtliche Verringerung der Flächen und Volumina zur Folge, womöglich durch Blockieren der Poren durch die großen Acetylgruppen.

     

木材工业用酚醛树脂的改性研究现状

从降低成本、提高性能的角度阐述了近几年来木材工业用酚醛树脂胶粘剂改性研究及应用的现状。     

新型节能环保的刨花干燥系统与烟气油炉的研制

本文通过介绍其技术特点、系统结构和应用效果,为烟气油炉与三通道干燥机组成的干燥系统的应用和推广提供一定的根据,供行业借鉴,参考。     

Swelling kinetics of thermally modified wood

European Journal of Wood and Wood Products - The swelling kinetics of native and thermally modified wood was studied. Norway spruce, Scots pine, European beech, and English oak specimens of...     

Application of polyuronides for removing heavy metals from vegetable oils II. Application of chemically modified polyuronides for demetalization of hydrogenated sunflower oil

Summary The possibility of heavy metal removal from hydrogenated vegetable oils with the help of chemically modified pectins was studied. These included pectic acids of different origin, sunflower, apple and celery, crosslinked with epichlorohydrin, as well as amidated pectins with different degrees of amidation. The degree of oil demetalization obtained was high- from 78% to 94%. It was found that the removal of the heavy metals Cu, Fe, Zn and Ni depended on the type of chemical modification of the pectin. The best results were obtained with amidated pectic acid.

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Einsatz von Polyuroniden zur Entfernung von Schwermetallen aus pflanzlichen Ölen II. Einsatz von chemisch modifizierten Polyuroniden zur Entmetallisierung von hydriertem Sonnenblumenöl

Zusammenfassung Es wurde die Möglichkeit untersucht, Schwermetalle aus hydrierten pflanzlichen Ölen mit chemisch modifizierten Pectinen zu entfernen und zwar mit Epichlorhydrin vernetzten Pectinsäuren unterschiedlicher Herkunft (aus Sonnenblumenkernen, Äpfeln, Sellerie und amidierten Pectinen mit verschiedenem Amidierungsgrad). Es wurde eine hohe Entmetallisierung von 78 bis 94% erreicht. Dabei wurde festgestellt, daß die Entfernung der Schwermetalle Cu, Fe, Zn und Ni von der Art der chemischen Modifizierung des Pectins abhängig ist. Die besten Ergebnisse wurden mit amidierter Pectinsäure erzielt.

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First communication: Ivanov K, Popova M, Kratchanov C, Maneva D (1990) Z Lebensm Unters Forsch 191:210–213     

Using the emulsion technique and an iron catalyst to enhance the wood protection properties of tall oil

The aim of this study was to investigate whether the two problems relating to wood protection with tall oil can be solved with one single treatment. The results showed that it is possible to combine the use of an iron catalyst to enhance the drying properties with the emulsion technique to reduce the amount of oil needed. In addition to enhanced drying properties, the iron catalyst also considerably improved the water repellent efficiency.     

Using the emulsion technique and an iron catalyst to enhance the wood protection properties of tall oil

Zusammenfassung The aim of this study was to investigate whether the two problems relating to wood protection with tall oil can be solved with one single treatment. The results showed that it is possible to combine the use of an iron catalyst to enhance the drying properties with the emulsion technique to reduce the amount of oil needed. In addition to enhanced drying properties, the iron catalyst also considerably improved the water repellent efficiency.      

Durability of particleboards made from wood particles chemically modified with propionic anhydride: results after six years in ground stake-test

Propionylated particleboard stakes with 12.2% propionyl content were tested in ground contact in Western Greece. The stakes showed severe attack after five years of testing and total decay after six years, whereas the unmodified boards showed total decay during the fourth year of testing.     

Proteolytic activity and immunoreactivity of chemically modified Papain

Summary The effect of different chemical modifications of papain on the proteolytic activity and immunoreactivity has been studied. Modification with Dextran T 2000 caused increasing decline in proteolytic activity both with increasing degree of dextran oxidation and amount of bound dextran, whilst the immunoreactivity determined by nephelometry remained unchanged. Modification of papain with glutaraldehyde and formaldehyde causes rapid drops in both activities, even at very low concentrations of agents. Acetylation of papain showed expressive maxima of both proteolytic and immunochemical activities at the same degree of enzyme acetylation. Modification with diazobenzensulphonic acid caused a high increase in immunoreactivity and a small increase in proteolytic activity.

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Proteolytische Aktivität und Immunreaktivität von chemisch modifiziertem Papain

Zusammenfassung Es wurde der Einfluß verschiedener chemischer Modifizierung des Papains auf dessen proteolytische Aktivität und Immunreaktivität untersucht. Die Modifikation des Papains mit Dextran T 2000 1äßt die proteolytische Aktivität bei steigender Dextran-oxidation und mit der Menge des gebundenen Dextrans abnehmen, wobei die Immunreaktivität, nephelometrisch bestimmt, unverändert bleibt. Bei der Modifizierung von Papain mit Glutaraldehyd und Formaldehyd werden beide Aktivitäten, auch bei sehr niedrigen Konzentrationen der Reagentien, stark erniedrigt. Das acetylierte Papain zeigt ein scharfes Maximum der proteolytischen und der immunchemischen Aktivität bei demselben Grad der Enzymacetylierung. Die Modifizierung von Papain mit der Diazobenzosulfonsäure verursacht einen hohen Anstieg der Immunreaktivität und einen nur geringen der proteolytischen Aktivität.

     

Pressure-assisted gelation of chemically modified poultry meat batters

Changes were induced in the characteristics of poultry meat protein using specific chemical modifiers to investigate the effect of pressurization, prior to heating, on gelation, texture and thermal behaviour of meat batters. Values of hardness and chewiness were higher in cooked meat batters treated with urea than in a salt-only sample, but cohesiveness was similar. The β-mercaptoethanol treatment produced a heat-induced gel with very similar properties to the salt-only gel. The rheological behaviours of salt-only and β-mercaptoethanol samples were very similar, but storage modulus values were higher in samples with urea, which accelerated gelation. The pressure-induced reduction of differences in the textural properties of meat batters suggests that hydrophobic interactions play an important role in heat-induced gelation. Differential scanning calorimetry showed that urea clearly destabilized chicken meat batters, while β-mercaptoethanol had very little influence on their thermal behaviour. Pressurization tended to equalize batters and final cooking definitively equalized them.     

Proteolytic activity and immunoreactivity of chemically modified papain

The effect of different chemical modifications of papain on the proteolytic activity and immunoreactivity has been studied. Modification with Dextran T 2000 caused increasing decline in proteolytic activity both with increasing degree of dextran oxidation and amount of bound dextran, whilst the immunoreactivity determined by nephelometry remained unchanged. Modification of papain with glutaraldehyde and formaldehyde causes rapid drops in both activities, even at very low concentrations of agents. Acetylation of papain showed expressive maxima of both proteolytic and immunochemical activities at the same degree of enzyme acetylation. Modification with diazobenzenesulfonic acid caused a high increase in immunoreactivity and a small increase in proteolytic activity.     

油脂加工厂的环保措施

目前我国加大保护生态环境力度,限制或减少油厂排放的污染物和污染量.从废物处理、废水排放、隔噪声、灰尘和锅炉除尘控制等方面介绍了有关环保措施的应用情况.对如何防止和降低可能突发性污染所做的应急预案进行了阐述,为保证清洁生产提供参考.     

Development of chemically interesterified healthy coconut oil blends

Edible vegetable oil blends, such as coconut:linseed; coconut:safflower; coconut:sunflower; coconut:rice‐bran oils; in the ratio of 70:30 and 60:40 v/v and pure coconut oil (CNO) were interesterified using sodium methoxide 0.5% and subsequently refined to prepare nutritionally superior flowable CNO blends which remained liquid even at sub‐zero temperatures. The slip melting point of chemically interesterified fats could not be determined as they are liquified just after removing from freezing chamber in comparison with the slip melting point of 21.5–26.5 °C for their uninteresterified counterparts. These interesterified fats were liquid and flowable at 6 °C for more than 4 h in a cooling chamber and their solidification temperature ranged between ?2.0 and ?5.5 °C. Free fatty acids showed an increasing trend from 0.35% to 2.0% resulting in decrease in triglycerides After refining these oil blends showed values similar to their controls. However, iodine value of interesterified and uninteresterified oils were close to each other. Differential scanning calorimetry showed the onset of crystallisation at lower temperatures and lower solid fat content for interesterified fats. A nutritionally superior combination of CNO blend which is flowable at low temperature could be prepared.