Naruhito Hori

Effect of the ethylene/vinyl acetate ratio of ethylene-vinyl acetate emulsion on the curing behavior of an emulsion polymer isocyanate adhesive for wood

We investigated the curing behavior of an emulsion polymer isocyanate adhesive for wood with different ethylene-vinyl acetate (EVA) emulsions, because it was found that the ethylene/vinyl acetate weight composition (E/VA ratio) of EVA could control the volume of gas emitted from the adhesive. EVA with higher VA content reduced the volume of gas emitted at the initial stage, which was caused by the extent of the reaction between the NCO groups and water. The reaction scheme of NCO could not be determined because the broad infrared (IR) absorptions due to CaCO3 and water masked the information of the NCO products in IR spectra. Examination of the degree of swelling suggested that the adhesive films stored for 3 weeks had the same degree of cross-linking structure in spite of the variation of EVA. This result was supported by IR spectroscopy, which showed the same amounts of NCO remained in these films. All the adhesives prepared in this study had satisfactory bond performance. The findings indicate that the E/VA ratio affects the curing behavior of the adhesive in the initial curing stage, whereas the cross-linking structure and the bond performance were independent of the E/VA ratio after storage for 3 weeks.

Effect of postcure conditions on the dynamic mechanical behavior of water-based polymer-isocyanate adhesive for wood

To study the effect of postcure conditions on the viscoelastic behavior of water-based polymer isocyanate adhesives for wood (API adhesive), dynamic mechanical analysis (DMA) was performed for a simplified model of API adhesives under various postcure conditions. These conditions were achieved by storing the samples at room temperature or by heating them in an oven. Fourier transform infrared (FT-IR) spectroscopy was performed to test for residual isocyanate groups (NCO) and isocyanate derivatives to elucidate the reaction mechanism under the postcure conditions. DMA revealed that the postcure conditions led to wide variations in the viscoelastic behaviors of API films. FT-IR analysis confirmed the decrease of residual isocyanate during postcure treatments. However, the complete consumption of isocyanate could not be achieved under the postcure conditions. A good correlation was found between the DMA result and the chemical changes in the API samples heated above 140°C. However, no correlation was observed in the case of the samples heated at temperatures less than 140°C. This implies that postcure conditions led to a difference in the reaction chemistry of API.

Surface Property and Compatibility of Poly(styrene-isoprene-styrene) Triblock Copolymer/Tackifier Blend System

The frictional forces between pressure sensitive adhesives (PSAs) and a probe tip were measured with a scanning probe microscopy (SPM). A peak appeared in the scanning rate-frictional force curve shifted to a lower scanning rate with decreasing temperature. In the case of the miscible system of isoprene matrix of SIS base polymer, the tendency of a peak to shift to a lower scanning rate was observed with increasing tackifier content; however, in the case of the immiscible system of styrene domain of SIS base polymer, no remarkable shift was observed. The frictional force is influenced by viscoelastic properties of the PSA which systematically changed with miscibility. In this study, it is aimed to clarify the correlation between the observation of phase structure and the behavior of surface rheology by using two kinds of tackifiers that have different miscibility with the polyisoprene phase or the polystyrene phase of SIS triblock copolymer.

Optimization of polyol production via liquefaction from Acacia mangium and analysis of the polyols by traditional methods and two-dimensional correlation spectroscopy

Abstract The aim was to optimize the liquefaction conditions of Acacia mangium wood flour with polyethylene glycol (PEG#400) as the solvent in the presence of sulfuric acid as a catalyst under atmospheric pressure. Reaction time (30–180 min), temperature (130–170°C), and the solvent ratio (PEG/glycerol=0–25%) were varied to obtain the lowest residue content. The resulting polyol was characterized by their hydroxyl number (OHN), acid number (AN), viscosity, molecular weight (Mw), thermogravimetric analysis, Fourier transform infrared (FT-IR) and two-dimensional correlation spectroscopy (2D-COS). The OHN was lowered, AN and Mw were elevated as a function of increasing the reaction temperature and the time. Introducing glycerol in the PEG system markedly increased the OHN, AN and viscosity of the liquefied wood. The optimum condition was 80/20% ratio of PEG/glycerol at 150°C in 150 min leading to a 75% liquefaction yield. The 1730 cm−1 band was indicative for the esters in the liquefied product. The 2D-COS analysis showed that lignin is easily liquefied at high temperatures and a decreasing amount of PEG, and that the presence of glycerol significantly enhanced the 1730 cm−1 band.