A Study On The Manufacturing Technology Of Exterior Medium Density Fiberboard

Exterior medium density fiberboard has come into the stage of industrialization abroad, but in our country medium density fiberboard is mostly for interior usage and exterior medium density fiberboard as a kind of products is still in the stage of research. The aim of the study is to refer a theoretic basis for promoting efficient usage of fast growing plantation of poplar and china fir, for enriching the variety of medium density fiberboards and for the industrialization of our exterior medium density fiberboard.This study takes orthogonal test as a basic research method and takes statistical analysis as a main analytical means. Under the grounds of selecting phenol-formaldehyde resin as adhesive and choosing constants for the defiber processing parameters, the percentage of water-repellent agent, the mat moisture content, the pressing pressure and so forth respectively, the study picks the glue content, density, hot-pressing temperature and time as variables. After verifying and subsequential test, the study gets the optimized processing parameters through which qualified exterior medium density fiberboard can be made.The research results indicate that: (1) Using poplar to make exterior medium density fiberboard is feasible; under the processing parameters: glue content 12%, density 0.82g/cm3, hot-pressing temperature 180℃ and hot-pressing time 7minutes, the properties of the 9mm thickness boards made from poplar in laboratory are: IB=0.91MPa, IB after the boiled test=0.43MPa, MOR=38.4MPa, MOE=3386MPa, TS=10.2%, all of the indexes reach the MDF national standard; (2) Using china fir to make exterior medium density fiberboard is feasible, but not as economical as poplar; under the processing parameters: glue content 13%, density 0.88g/cm3, hot-pressing temperature 175℃ and hot-pressing time 6minutes, the properties of the 9mm thickness boards made from china fir in laboratory are: IB=0.94MPa, IB after the boiled test=0.32MPa, MOR=36.2MPa, MOE=3651MPa, TS=11.5%, all of the indexes reach the MDF national standard; (3) Using mixtures of poplar and china fir to make exterior medium density fiberboard are feasible, adding more than 25% of poplar fiber into mixtures to make exterior medium density fiberboard can enhance the quality of the board greatly; under the processing parameters: glue content 12%, density 0.83g/cm3, hot-pressing temperature 180℃ and hot-pressing time 6minutes, if poplar:china fir≥25:75, the properties of the 9mm thickness boards made from mixtures in laboratory are: IB≥0.84MPa, IB after the boiled test≥0.34MPa, MOR≥34.0Mpa, MOE≥3247MPa, TS≤12%, all of the indexes meet the requirements of the MDF national standard.