عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Background and objectives
Increasing of population and daily progressive increase of demand for wood products caused reduction in forest area so that serious regulations have been developed concerning trees cut, Intensive insist of Iranian environmental organization caused that the matter of stopping of forest harvesting is seriously considered and amount of wood harvesting from forests reduce to low than one million cubic meter therefore wood industry is facing wood shortcoming. (12).
The aim of this study was to recycle fibers from waste panels using ecofriendly electerolis method and using them for producing MDF.
Materials and methods:
In this study, first wood panel wastes of MDF were collected from several firms. MDF wastes were immersed in water for 24 hours. Immersing was conducted for penetration of water in the MDF wastes before Ohmic heating. Small pieces of wet MDF were placed in a cylinder equipped with electrical steel electrodes Rectangular electrodes were fixed parallel with each other in the side walls of cylinder. After 45 minutes, fibers of MDF were separated by hydrolysis. In order to increase electrical conduction, some salt was added to the mixture. Obtained fibers were separated and dried and mixed with fresh fibers provide by a local firm (70% based on dry weight of board) for board producing. For reinforcing of UF resin, nano- cellulose was used at three levels of 0, 1 and 3 percent. Resin UF was allied at two levels of 8 and 12 percent.
Manufacturing parameters such as press temp. Of 160 degree centigrade and press time of 8 minutes were kept constant for all treatments. Physical properties of thickness swelling (TS) and water absorption (WA) after 2 and 24 hours water immersing in water and mechanical properties of internal bond (IB), modulus of rupture (MOR) and modulus of elasticity (MOE) of boards were evaluated. The results showed that the highest modulus of rupture (14/47Mpa) and modulus of elasticity (1359/096Mpa) of the boards made with 12% glue and 3% nano- cellulose was, as well as the highest internal bonding in the boards made with 12% glue and 3% nano- cellulose was (0/5Mpa). The least amount of thickness swelling (%4/720 and %9/863 after 2 and 24 hours floatation on water respectively) was observed in boards made with 12% glue and 3% nano- cellulose. As well the least amount of water absorption (%33/113 and %80/653 after 2 and 24 hours floatation on water respectively) was observed in boards made with 12% glue and 3% nano- cellulose.
Statistical analysis of results was conducted using SPSS 16. Results showed that recycled fibers have suitable quality. It is possibility to reuse it mixed with fresh fibers. Manufacture board properties, however, are not as high as standard. Adding nano-cellulose into UF glue caused an improvement in mechanical properties and water absorption and thickness swelling were decreased.