ON THE SUITABILITY OF THERMOMECHANICAL AN D CHEMO-THERMO-MECHANICAL PULPS (TMP AND CTMP) FROM BEECH AND PINE FOR THE MANUFACTURE OF MEDIUM DENSITY FIBERBOARDS .2. PROPERTIES OF MEDIUM DENSITY FIBERBOARDS FROM BEECH PULPS

Medium density fibreboards (MDF) were made from beech in laboratory an d pilot plant scale from thermo-mechanical (TMP) and chemo-thermo-mech anical pulps (CTMP) using both melamine reinforced urea-formaldehyde r esin (UF-resin) and diphenylmethane diisocyanate polymers (PMDI). The physical-mechanical and chemical properties of the boards were evaluat ed. From the results the following conclusions can be drawn: 1. Both T MP and CTMP led, on using UF-resin, to MDF with very high mechanical p roperties exceeding the required values in European standards. 2. Pulp ing temperature seems to have an influence on the mechanical propertie s of the boards, prepared from TMP and CTMP. Increasing the pulping te mperature from 150 degrees C to 170 degrees C negatively affects the m echanical board properties, whereas the properties of MDF from CTMP (s ulfonic group content between 0.2% and 0.3%) increases by elevating th e maximum pulping temperature from 150 degrees C to 170 degrees C. 3. The pulping chemicals in the CTMP-process (Na2SO3 and/or NaOH) decreas e the formaldehyde release from the boards, as they act as scavengers for formaldehyde. 4. Due to higher deacetylation degree during CTMP pr ocess, MDF made from CTMP release more than 4 times acetic acid than M DF from TMP. The release of formic acid is quite different, it is in M DF, made from TMP higher than in MDF from CTMP. 5. MDF with very high mechanical properties can also be made from beech pulps (TMP) using PM DI. PMDI in combination with a formaldehyde scavenger in the middle la yer and UF-resin in the surface layer leads to boards with very low fo rmaldehyde release.