Influence mechanism of roller-press impregnation on the dimensional stability of eucalyptus scrimber

Objective To solve the problem of poor dimensional stability caused by the uneven disintegration during the preparation process of scrimber, the scrimber was prepared by roller-press impregnation, and the influence mechanism of roller-press impregnation on the dimensional stability of eucalyptus scrimber was explored.

Method In this study, eucalyptus scrimber was prepared by cage and roller-press impregnation techniques, and the surface morphology, microstructure, and glue distribution were observed by ultra-depth microscope, scanning electron microscope, microcomputer tomography scanner, and laser confocal microscope. The surface chemical composition, surface roughness, surface wettability, and water resistance of scrimber were studied by X-ray photoelectron spectroscopy, roughness tester, contact angle tester, soaking at 63 ℃ for 24 h, and 28 h cycle treatment (boiling for 4 h, dry at 63 ℃ for 20 h, boiling for 4 h).

Result Compared with the wood scrimber prepared by cage impregnation (CWS), the surface cracks, roughness, and the surface wettability of wood scrimber prepared by roller-press impregnation (RWS) were reduced, and the water resistance of RWS was significantly increased. The results of roughness showed that compared with CWS, the surface roughness R_a and R_z of RWS decreased by 34.38% and 72.75%, respectively. The contact angle test results indicated that the surface wettability of RWS was weakened, and the surface contact angle of RWS increased by 283.95% compared with CWS at the 20th second. The test result of soaking at 63 ℃ for 24 h showed that the thickness swelling ratio (TSR) and width swelling ratio (WSR) of RWS were 5.47% and 1.11%, respectively, which were 52.16% and 50.09% lower than those of CWS. The TSR and WSR of RWS under 28 h cycle treatment were 6.24% and 1.17%, respectively, which were reduced by 51.45% and 58.51%, respectively. The process of roller press caused secondary damage to the recombination unit, which increased the flow path for PF resin solution. At the same time, the negative pressure generated by the roller pressing during the process from compressing the cells to restoring their original appearance increased the penetration depth of the glue, formed a network bonding structure, strengthened the bonding performance of the recombined wood, and inhibited the rebound of wood cells after water absorption.

Conclusion The roller-press impregnation improves the uniformity of glue distribution in scrimber, reduces the surface roughness of eucalyptus scrimber and wettability, and significantly improves the water resistance and dimensional stability, which has important references and guidance for the process optimization and continuous production of scrimber.