Shear Strength and Microscopic Characterization of a Bamboo Bonding Interface with Phenol Formaldehyde Resins Modified with Larch Thanaka and Urea
The aim of this study was to understand the microscopic characteristics of the bamboo bonding interface with phenol formaldehyde resin modified with larch thanaka and urea (PTUF) and its effect on the shear strength of two-ply bamboo laminated lumber. Bleached and carbonized bamboo strips were used, and two assembly patterns (outer-to-outer and inner-to-inner) were adopted to make two-ply bamboo laminated lumber with PTUF. The microstructure of the bonding interface and the bond-line thickness were investigated using a scanning electron microscope. The average depth and effective depth of PTUF on bamboo surfaces were evaluated by fluorescent microscopy characterization. The shear strength of two-ply bamboo laminated lumber was also examined. The results revealed a shallow depth of penetration of PTUF into the bamboo surface that was distributed primarily in the broken cell cavities formed during preparation, as well as between the cell walls. When the assembly pattern was inner-to-inner, the depth of penetration and bond-line thickness were higher, but the shear strength was lower than that of the outer-to-outer pattern. The carbonized bamboo laminated lumber provided a greater resin penetration and bond-line thickness, but lower shear strength, than the bleached bamboo laminated lumber.
Study on urea-modified phenol formaldehyde resin adhesive
A reasonable technology to synthesize Urea-Modified Phenol Formaldehyde resins is realized by reacting phenol,urea and formaldehyde.The resin's feasibility is explored.The experiment result of shows that storable stability of the modified resin is good.The curing temperature of PUF resins was 25 ℃,lower than that of PF resins.The curing speed of PUF resins is faster than that of PF resins at the same curing temperature.The physical properties of the birch plywood bonded with PUF resins is similar to that of the birch plywood bonded with normal PF resins.The mechanical properties of the birch plywood bonded with PUF resins can achieve the demands of GB/T9846-1988.Free formaldehyde content of plywood is lower than the E1 level set by GB18580-2001.The cost of the adhesive is lowered for the use of urea,and its comprehensive properties is better than that of PF resins.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.