Nilgül Özmen

Use of organosolv lignin in phenol–formaldehyde resins for particleboard production: I. Organosolv lignin modified resins

Abstract This paper describes the work considering the potential for partially replacing phenol with organosolv lignin in phenol–formaldehyde resin used as an adhesive in the production of particleboard. Lignin-based resins were synthesised with organosolv lignin using various percentages of lignin replacement for phenol. The lignin was introduced to the resin in two different ways. The first method was the replacement of a certain percentage of phenol (5–40%) with lignin (as supplied) directly into resins. In the second method, lignin was modified by phenolation prior to resin manufacture. Different degrees of phenol substitution (20–30%) were investigated for the production of lignin-based resins. The physical properties of the formulated resins were measured and compared to commercial PF resin.

Use of organosolv lignin in phenol-formaldehyde resins for particleboard production. II. Particleboard production and properties

The objective of this work was to demonstrate the utility of lignin-based resins designed for application as an adhesive in the production of particleboard. Bond qualities of lignin-phenol-formaldehyde resins, phenolated-lignin-formaldehyde resins and commercial phenol-formaldehyde (PF-com) resin were assessed by using an automatic bonding evaluation system, prior to production of particleboards. In order to evaluate the quality of lignin-based resins, particleboards were produced and physical and mechanical properties were investigated. These physical properties included internal bond, modules of rupture and modulus of elasticity. Thickness swell and water absorption properties of particleboards bonded with lignin-based resins were also determined. The lignin-based resins have been reported previously in Part I of this study. The results showed that particleboards bonded with phenolated-lignin formaldehyde resins (up to 30% lignin content) exhibited similar physical and mechanical properties when compared to particleboards bonded with PF-com. The work has indicated that phenolated-lignin formaldehyde resins (up to 30% substitution level) can be used successfully as a wood adhesive for constructing particleboard. The performance of these panels is comparable to those of boards made using PF-com resin.

The effect of chemical modification on the strength of wood and bonded wood joints

Abstract The effect of propionic, crotonic or methacrylic anhydride (MA) modification on the lab joint strength of monomer bonded veneer strips was investigated. Lap joints were formed by hot pressing veneers of modified wood with monomer in the presence of free radical initiator and bond strength was determined on an Automatic Bonding Evaluation System tensile tester. Test results indicated that chemical treatment improved bond quality between hydrophilic wood and hydrophobic monomer. Extremely strong bonds (wet and dry conditions) formed in the case of MA modified veneer strips. In addition, the effect of chemical modification on the mechanical properties of strips was also investigated. Chemical modification had a detrimental effect on the mechanical properties.

Acetylation of wood components and fourier transform infra-red spectroscopy studies

In this study, the reactivity of wood components with acetic anhydride or vinyl acetate was studied. It was found that the reactivity of wood components was virgin wood flour > holocellulose >> a-cellulose. Acetylation of Turkish pine or cedar wood flour with acetic anhydride was significantly improved in the presence of potassium carbonate at 100°C. Maximum of about 20 and 18% weight percentage gain (WPG) values were obtained with Turkish pine ( Pinus brutia ) and cedar ( Cedrus libani ) wood flour after 3 h reaction at 100°C, respectively. The two modification methods and the effect of wood components on vinyl acetate (VA) or acetic anhydride (AA) modification, were characterised by infrared analysis in detail. As an apparent advantage of this new method, acetaldehyde was formed as by-product which is non-acidic was removed easily after the reaction due to low the boiling point of acetaldehyde [b.p. (760 mm Hg) = 21°C]. Key words : Acetic anhydride, vinyl acetate, holocellulose, α-cellulose, FTIR, chemical modification

Dimensional changes in Corsican and Scots pine sapwood due to reaction with crotonic anhydride

Abstract The effects of the reaction temperature and varying level of weight gain on the dimensional stabilisation of crotonic anhydride modified Corsican and Scots pine sapwood were investigated. With Corsican pine at low levels of substitution, the reagent occupied larger molar volumes in the cell wall than at higher weight gains. With Scots pine the molar volume occupied by reagent was found to be temperature dependent at low levels of substitution. Dimensional stabilisation was determined by the water-soak/oven-dry method through a total of ten cycles in order to determine the stability of the ester bond to hydrolysis at neutral pH. It was found that the reaction temperature has no significant effect on dimensional stability provided the same weight gain level is obtained. At weight gain levels in excess of 30%, values of anti-shrink efficiency of 90% were obtained.

A new approach for acetylation of wood: Vinyl acetate

The chemical modification of wood has been the subject of research for many decades. The most favoured modification reaction involves the acetylation of wood with acetic anhydride. Reacted acetate provides dimensional stability by bulking the cell wall polymers and reduces further swelling when the woods come into contact with water. In addition that chemical modification also provides biological resistance. With acetylation, it is possible to extent at least twice or three times service life of wood as compared to control one. Acetylation of wood with acetic anhydride is not subject only academic studies, it is also became commercial process since 2003. In Turkey, the study of acetylation of wood with acetic anhydride is limited with academic work. There are two main obstacles commercialization of acetylation in Turkey. One of them is the cost of acetic anhydride, the other is that acetic anhydride is the restricted chemical. The purchase and the stock of acetic anhydride are requiring special permission from Health Ministry because of its use for the synthesis of heroin by the diacetylation of morphine. The purpose of this study is to show the new methods for acetylation of wood. Scots pine (Pinus sylvestris) sapwood was successfully acetylated by the new transesterification reaction with vinyl acetate. Under identical conditions, Scots pine sapwood was also modified with acetic anhydride to compare with the new technique. The results of acetylated wood with acetic anhydride and vinyl acetate were compared, and characterized by Infrared (FTIR) and 13C CP MAS NMR analysis.