MOISTURE AND HYDROLYSIS RESISTANCE OF PARTICLEBOARDS, 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 mixture 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-mechanical properties of the boards deteriorated. In contrast, the formaldehyde release decreased with increasing amount of catalyst. 2. Compared with ammonium chloride ammonium nitrate led to higher mechanical properties and lowered thickness swelling of the boards. 3. Particleboards containing UF 1 as a binder showed, compared with those boards bonded with UF 2, higher mechanical proper ties and lower thickness swelling in water. However, the formaldehyde release of the boards bonded with 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, those prepared with ammonium sulfate or a mixture of ammonium sulfate and formic acid as a catalyst the lowest.