MOISTURE AND HYDROLYSIS RESISTANCE OF PAR TICLEBOARDS, BONDED WITH UNMODIFIED AND MODIFIED LOW FORMALDEHYDE UF-RESINS USING DIFFERENT CATALYST SYSTEMS .2. PREPARATION AND PROPERTIES OF PARTICLEBOARDS BONDED WITH UNMODIFIED LOW FORMALDEHYDE RESINS

In continuation of the work conducted in the first part of this series one-layer pine wood particleboards were made using two different low- emission UF-resins (UF 1 and UF 2) using various amounts of different catalysts (ammonium chloride, ammonium sulfate, ammonium nitrate, a mi xture of ammonium sulfate and formic acid) and tested regarding their properties. From the results the following conclusions can be drawn: 1 . With increasing amount of catalyst in the range between 0.8% and 2.4 % ammonium chloride and 0.8% and 3.2% ammonium nitrate the physical-me chanical properties of the boards deteriorated. In contrast, the forma ldehyde release decreased with increasing amount of catalyst. 2. Compa red with ammonium chloride ammonium nitrate led to higher mechanical p roperties and lowered thickness swelling of the boards. 3. Particleboa rds containing UF 1 as a binder showed, compared with those boards bon ded with UF 2, higher mechanical proper ties and lower thickness swell ing in water. However, the formaldehyde release of the boards bonded w ith UF 1 was above that of boards bonded with UF 2. 4. Particleboards bonded with UF 1 and UF 2 as a binder and containing ammonium nitrate as a catalyst showed, in general, the highest mechanical properties, t hose prepared with ammonium sulfate or a mixture of ammonium sulfate a nd formic acid as a catalyst the lowest.