Journal
JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY
Volume 32, Issue 24, Pages 2667-2681Publisher
TAYLOR & FRANCIS LTD
DOI: 10.1080/01694243.2018.1511075
Keywords
Urea-formaldehyde resin; oxidized starch; UF-OS adhesives; blocked pMDI; plywood
Funding
- Korea Forest Science Technology by the Korea Forest Service (Korea Forestry Promotion Institute) [2015077B10-1718-AA01]
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This study investigated the modification of UF resins of two different formaldehyde/urea (F/U) mole ratios with OS levels, using blocked pMDI (B-pMDI) as a cross-linker for plywood. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of C=O of aldehyde and carboxyl groups in the OS. The UF-OS adhesives then were prepared by adding 5%, 10%, and 15% OS based on the UF resin's solid content as well as 1% B-pMDI based on the OS dry weight as a cross-linker. FTIR spectra confirmed the formation of ester groups at 1348 cm(-1) owing to the reaction of carboxyl groups of OS with -NCO groups of B-pMDI. Regardless of the F/U mole ratio, both the solids content and viscosity of the UF resins decreased, but the gelation time increased as the OS level increased. Differential scanning calorimetry showed that the activation energy of neat UF resin with 1.0 F/U mole ratio was higher than that with 1.2 F/U mole ratio; however, the opposite was true after the OS addition. These results showed that the modified UF resins improved the adhesion strength and decreased formaldehyde emission of plywood. The best performance of modified UF resins with different F/U mole ratios of 1.0 and 1.2 was found at 10% OS based on resin's solid content.
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