Poplar Plywood Glued Anti-aging Performance

After our nation?s opening and reformation, the demand for plywood increased year after year as a result of quickened speed of basic construction and heightened standard of living. Plywood is usually used for room fitment and for concrete formwork. Laminated veneer lumber (LVL), which is banded with parallel grain plies, is mainly used for structure and has been used for furniture manufacture. Because the performance of plywood will gradually recede when plywood is effect by weather change or by manade factors, the service of plywood has become what we are concerned for. Many researches and investigations have been done abroad to study the durability of woodased panel especially of particleboard. But few systematic researches were embarked upon in our country, though some investigations on particleboard have been done. Few research reports on plywood durability were founded in our country or in foreign countries. As the natural forest decrease day by day and actualization of our nation natural forest protection project, poplar, which is a kind of wood of manade fast growing forest, has become one of the main materials for plywood use. In such condition, we studied the gluing durability of poplar plywood.By using ASTL( P1037 and BS 5669 two accelerated aging test method, the UF adhesive poplar plywood (three layers) and the PF adhesive poplar plywood (three Layers) were tested respectively under different adhesive amount and different layp condition. The following are our conclusions:(1)In BS 5669 accelerated aging test, the glue bond strength (GBS) of UF adhesive poplar plywood (IJAPP) decreased notably in the first aging cycle, and the GBS of UAPP which is banded with parallel grain plies decreased more sharply then the one with crossanded plies. The rapidity of CBS decreasing in the first aging cycle increased along with the increase of adhesive amount, and the UAPP with parallel grain plies was especially distinctive.(2)After the three aging cycles of BS 5669 accelerated aging test, the GBS preservation ratio of UAPP with parallel grain plies decreased along with the increasing of adhesive amount, and the UAPP with crossanded plies had a reversed trend. But the last value of GBS of IJAPP with parallel grain plies is higher thenthe one,ith crossthanded plies.(3)In the BS 5669 accelerated aging test, the strength of POplar veneer 'asal,ays higher then the shearing strength of adhesive layer.(4)According to the test result of t'o different POplar veneer, the gluingperfomance and gluing durability Performnce of UAPP,ere also effected by thefluctuation of t'o diftbrent d irec t ions of the veneer surface that is the directionparallel to the veneer grain and the direction perPendicular to the veneer grain,and effected hy the subordination chemical comPOnents of the poplar veneer. Ifthe chemical substance content is high, the decreasing of GBS probably,ill bequick. But this yerdict needed further validation.(5)In the ASTM Dl037 accelerated aging test, after certain cycles the veneerstrength of PF adhesive poplar plpood (PAPP) became lo'er then the shearingstrength of adhesive layer. After three aging cycles, the surface of the testspecimens became rough and had some obvious crackles that became more and ooreboard and deep as the aging test processed.(6)In the AarM Dl037 accelerated aging test, the veneer strength of PAPP,ithparallel arein plies became lo,er then the shearing strength of adhesive layerat the end POint of the third aging cycle, and the one 'ith cross--banded p1iesdo at the POint of the fourth aging cycle. This phenomenon indicated that the gluingdurab il ity of PAPP,ith parallel grain pl ies sas higher then the cross--banded one.At the end POint of the second aging cycle, the value of PYeserved GBS of PAPP,ith paralle1 grain plies were high, if the PAPP had a high adhesive asount, butthe variety of the GBS preservation ratio,as not notable. The PAPP,ithcrosschanded plies had the similar phenomena at the end POint of...