Keywords: 
• forest engineering /
• high concentration of formaldehyde /
• MUF /
• room temperature curing /
• physical and mechanical properties

Abstract: To research the influence of high formaldehyde concentrations on synthetic copolycondensation of melamine urea-formaldehyde （MUF） resin performance, resins from a high formaldehyde concentration （MUF-H） of 50% and standard concentration （MUF） of 37% were compared. Then glulam was prepared at room temperature （20 ℃） to test its physical and mechanical properties. Also, structural characteristics and thermal mechanical properties of resins were studied using 13C-NMR （nuclear magnetic resonance）, Fourier transform infrared （FT-IR） spectroscopy, and Dynamic Mechanical Analysis （DMA）. Results showed that the high formaldehyde concentrations enhanced solid content and viscosity of the MUF-H adhesive, shortened curing time, and improved shear strength for 60%. The DMA test results revealed that the MUF-H resin also greatly enhanced the adhesive elastic modulus. Additionally, the 13C-NMR analysis indicated that the methylene and ether bonds of MUF-H resin ware higher than MUF. Thus, the MUF-H system had a higher reaction rate and crosslinking degree which improved the mechanical properties of the resin.［Ch, 5 fig. 5 tab. 15 ref.］