1,720,988 research outputs found
Use of spruce tannin as a binder in particleboards and medium density fiberboards (MDF)
No full textIn the recent past, increasing attention has been paid to the use of natural adhesives as a binder in the wood-based panel industry. Nowadays, two German companies are using Quebracho tannin and Wattle tannin for the production of particleboards and medium density fiberboards (MDF), respectively. To date no serious attention has been given to bond fiberboards using tannin derived from spruce bark. Results of research work on the use of spruce tannin as a binder for medium density fiberboards carried out in the last two years are presented. The results reveal that spruce tannin can be used to partially substitute Quebracho tannin in MDF up to about 60%. Such boards still meet the specification of moisture resistant MDF (according to EN 319 and EN 321). Moreover, spruce tannin can be used to 100% as a binder for the production of MDF for indoor use (type MDF EN 622-5)
Use of fiber material from chemothermomechanically processed waste particleboard and fiberboard
No full textSubject Chemo-thermo-mechanical pulps (CTMP) were made from waste particle- and fibreboards. Medium density fiberboards (MDF) were made from industrial refiner fibers in combination with the CTMP using urea-formaldehyde resin as a binder. The physical properties and the formaldehyde content of the MDF were determined. The results reveal that MDF made from CTMP of waste particle- and fibreboards meet the standards according to EN 622-5, type MDF. The bending strength and internal bond of MDF made from industrial TMP is higher compared with MDF from chemo-thermo-mechanical pulps from waste panels. However, the thickness swelling of MDF made from pulps derived from waste panels is clearly lower compared with that of MDF made from industrial TMP. Furthermore, MDF made from pulps derived from waste panels show a lower formaldehyde content than MDF from virgin fibers. It seems that residues of chemicals from the pulping process (CTMP) act as a formaldehyde scavanger
Influence of moisture content on the formaldehyde release of particle- and fibreboards bonded with tannin-formaldehyde resins
No full textThe main objective of this study was to evaluate the influence of moisture content on the formaldehyde release of particleboards and medium density fibreboards (MDF) bonded with tannin-formaldehyde (TF-) resins. The results revealed that increasing the moisture content in the TF-bonded boards elicited a decline in the content of extractable formaldehyde (perforator values according to EN 120). This is an opposing behaviour to the general state of knowledge related to the influence of moisture content on the formaldehyde content (EN 120) of particleboards and MDF bonded with urea-formaldehyde based resins. Moreover, the TF-bonded panels showed a decrease in the gas analysis values (EN 717-2), flask values (EN 717-3) as well as formaldehyde emission measured in the 1 m(3)-chamber (EN 717-1). EN 120 (now also pr EN ISO 12460-5, 2013) does not take into consideration that boards bonded with other binders rather than aminoplastic resins may behave differently at different moisture contents. Insofar, it leaves no leeway to consider different binders systems
Change of water absorption and density profiles of PF- and PMDI-bonded MDF during water storage
No full textPF- and PMDI-bonded laboratory made fibreboards (binder content 10% PF-resin and 6% PMDI) were stored under water at different temperatures (40degreesC, 50degreesC and 60degreesC) for a period of six weeks. The water absorption of the boards was measured, moreover the change in density profile was also registered for boards stored at 40degreesC after drying at 40degreesC and climatisation at 20degreesC and 65% relative humidity. The results show that at the beginning of storage time PF-bonded boards absorb relatively more water than PMDI-boards. Thereafter, the water uptake of PF-boards increases at a lower rate compared to PMDI-boards. The density profiles reveal that the major change in density due to water-storage is mainly in the middle layers of the boards
Use of fiber material from chemically-thermally processed waste fiberboard for production of medium-density fiberboards
No full textSubject Waste paper coated fiberboards are chopped into chips and then pulped according to a chemical-thermal procedure, which dissolves the wood structure. The liquid remaining after the separation of the fibre material (pulp) is retained as waste liquor and can be used as extender for wood adhesives. The pulps are used as raw material for medium density fiberboards (MDF). The mechanical properties of medium density fiberboards were determined. There are no significant differences between the strength properties of boards derived from industrial virgin fibres alone and from industrial fibers substituted by 50% of the chemically treated waste paper coated MDF. However, the thickness swelling of boards derived from industrial fibers mixed with fibers from a chemically treated waste MDF are significantly lower
Effect of oxidising and reducing agents on the release of volatile organic compounds (VOCs) from strands made of Scots pine (Pinus sylvestris L.)
No full textStudy of the influence of treating pine wood strands with hydrogen peroxide as an oxidising agent and sodium sulphite as a reducing agent on the emission of volatile organic compounds revealed that hydrogen peroxide increases the emission of aliphatic aldehydes (e.g. hexanal) and reduces the emission of monoterpene compounds (like alpha-pinene). Sodium sulphite as a reducing agent decimated the emission of monoterpene compounds without noticeably affecting the emission of volatile aldehydes
Influence of pulping methods (thermomechanical, chemothermomechanical) and pulping conditions on physical and technical properties of medium-density fibreboards
No full textSubject Thermo-mechanical pulps (TMP) and chemo-thermo-mechanical pulps (CTMP) were made from spruce under different pulping conditions. The fibres were dried at 70 degrees C. Medium density fibreboards (MDF) were made in pilot plant scale from the pulps using urea-formaldehyde resin as a binder. The results of testing the physical properties reveal, that the pulping temperature has a significant influence on the thickness swelling and water absorption of the boards. MDF from fibres produced at high pulping temperature (180 degrees C) generally show lower thickness swelling and water absorption than MDF made from fibres produced at lower pulping temperature (140 degrees C and 160 degrees C)
Method to determine the wettability of wood fibers
No full textThis paper describes a method to measure the wettability of thermomechanical pulps (TMP) from wood. Handsheets were made from pine TMP produced at different pulping temperatures (140 degreesC, 160 T and 175 degreesC). A coloured waterdrop, (0.1% aniline-blue solution) is added on the surface of a handsheet. The wettability is defined by the time elapsed from applying the waterdrop on the handsheet until its total penetration. The results reveal that pulping temperature influences the wettability of the TMP. The wettability of the TMP decreases with increasing pulping temperatures during the refining process
Paraffins of different chain length as swelling agents in medium-density fiberboards
No full textThe influence of chain length and amount of paraffins on the thickness swelling, water absorption and internal bond of MDF was assessed. Pronounced differences in the sizing efficiency of paraffins with different chain length were found. On using 0.1% paraffin ( based on dried fibres) sizing efficiency increases between C-20 and C-28. Higher paraffin content (> 0.25%) has an insignificant influence on the swelling behaviour of MDF. Preliminary results indicate that addition of 0.5... 1.0% of the tested paraffins seems to improve the internal bonding strength of the MDF
- …
