The incorporation of the modified starch (MS) in urea-formaldehyde resins at different stage of the synthesis was studied in this article. The synthesized resins were characterized by Fourier transform infrared spectroscopy, indicating that the ester bond can be introduced into the UF structure after the addition of MS. The curing reactions were examined with differential scanning calorimetry and it reveals that curing temperature of UF resin are slightly shifted to higher temperatures. To study the bonding strength and formaldehyde emission of the bonded plywood, the addition method and amount of MS are systematically investigated. The performance of the UF resins is remarkably improved by the addition of MS around 15% (weight percentage of the total resin) in the second stage.

A new zero-waste and zero-pollution composite adhesive labeled Chinese fir-based adhesive for exterior plywood was synthesized by blending alkaline Chinese fir (Cunninghamia lanceolata) liquid with a small amount of phenol-formaldehyde (PF). The free phenol and free formaldehyde content of the Chinese fir-based adhesive were sharply decreased compared to normal PF resin by more than 50%. The synthetic adhesive show with excellent water resistance and environmental friendliness, which had a 28h boil-dry-boil wet bonding strength of 1,73MPa according to standard JIS K6806-2003 and a formaldehyde emission of 0,045mg/L according to standard JIS A1460-2003. The structural properties and their thermal properties of cured adhesives were evaluated using Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC). The FT-IR analysis confirmed the expected chemical structure as the Chinese fir liquid reacted with formaldehyde and phenol which occurred at the wavenumbers of 1733, 1698, 1652cm -1 and 1077, 1048 cm -1 . Although the DSC results indicated that the Chinese firbased adhesive's curing need higher temperature than the control PF resin, the higher curing temperature hardly cripple the availability of Chinese fir-based resin in the plywood production.

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