Tan Haiyan

Fabrication, performances, and reaction mechanism of urea–formaldehyde resin adhesive with isocyanate

In order to improve the performances of urea–formaldehyde (UF) resin adhesive and reduce formaldehyde emission, the isocyanate was applied to modify the UF resin adhesive. The effects of the composition ratio of the isocyanate/UF resin on the thermal stability and molecular structure of the composite adhesive were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analyzer. The results showed that the appropriate addition of the isocyanate into the UF resin is favorable to improve the performances of the composite adhesive due to the chemical cross-linking reaction of the isocyanate with UF. Furthermore, the reaction mechanism of the UF resin adhesive with isocyanate was analyzed in detail. These research results can be applied to aid materials engineering design for the development of new adhesive, quality assurance, and characterization assessment of durability.

Comparative study of plasticizing effect of corn starch using formamide and urea

Formamide and urea were used as plasticizers for corn starch to prepare formamide plasticized-thermoplastic starch (FPTPS) and urea plasticized-thermoplastic starch (UPTPS), respectively. The properties of thermoplastic starch (TPS) were tested by scanning electron microscope (SEM), x-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and mechanical testing machine. Scanning electron microscope result shows that both formamide and urea can make corn starch plasticized form uniform continuous phase, but plasticizing effect of formamide was better than that of urea. X-ray diffraction exhibits that the crystallization peaks of FPTPS were disappeared, and a reduction minish for UPTPS, the crystallinity of FPTPS was smaller than UPTPS. The gelatinization temperature of two kinds of thermoplastic starches was basically the same, but the gelatinization enthalpy of FPTPS was much less than UPTPS. Formamide was better plasticized than urea for corn starch, which made the TGA inflection temperature and residual quantity of FPTPS was lower than UPTPS. FPTPS tensile strength was lower than UPTPS, but the elongation at break was much bigger than UPTPS.

The quick determination method of resin content in larch wood

The resin content in larch wood is usually determined by the traditional Benzene-Alcohol Extract Method (BAEM). In order to meet the requirement of production practice, the authors present two simple quick determination methods, IR lamp method and hydrogen peroxide solution method. Compared with the results of traditional method, the results of new methods are nearly the same as former, therefore, both two methods can reflect the change condition of resin content in wood.