Gu Jiyou

Analysis of moisture diffusivity of larch timber during convective drying condition by using Crank’s method and Dincer’s method

Two analytical procedures (Crank’s method and Dincer’s method) for porous solid materials were reevaluated and used to determine moisture diffusion coefficients and moisture transfer coefficients for larch lumber subjected to drying. A diffusion-like equation was used to describe drying process data. The lumber was idealized in the modeling as infinite plates. The moisture transport process inside the board was assumed to be one-dimensional. The macroscopic drying kinetics curves of larch timber at particular conditions were determined experimentally. Based on these data, calculation for both the moisture diffusion coefficients and moisture transfer coefficients by the Dincer’s analytical procedure were made. The dynamic moisture diffusion coefficients by the traditional Crank’s method were calculated. In general, diffusion coefficients calculated by the Dincer’s method were all higher than those by Crank’s method. These results could be due to the differences between two analytical methods and also different characteristics between solid moisture diffusion process and heat transfer process. Therefore the analysis and solution procedures of moisture diffusion differential equations need to be adapted in the future. With drying temperature’s increasing moisture diffusion coefficient (D) and moisture transfer coefficient (k) increases accordingly. Also the relationships between diffusion coefficients and temperature as well as material moisture contents were analyzed by using Arrhenius equation and bound water transport theory.

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.

A discussion on producing agro-residue composites with isocyanate resins

With the urgent shortage of forest resource in China, using agro-residues as raw materials of composite become increasingly important. Agro-residue is the most potential fiber resource, which is helpful to sustainable development of composite industries in China. Based on a great deal of researches, this paper summarized and discussed some problems in using agro-residues as raw materials of composites, including raw material preparation, hot-pressing, bonding technology, preventing composite from going moldy. It is proposed that to manufacture the composite of rice straws or wheat straws, the isocayante resin is a suitable adhesive, and the appropriate technologies, bonding, and treatment measures are also needed.

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.