The Study on Hybrid Properties of UF Resin and Bayberry Tannin Adhesive

To solve the problem of UF and tannin resin, this study prepared the adhesive by mixing UF resin and tannin resin to make maximization of the advantages of these 2 resins. Infrared spectroscopy(FT−IR), nuclear magnetic resonance carbon spectroscopy(¹³C NMR) and mass spectrometry(MS) were used to study the molecular structure of the hybrid adhesive; differential scanning calorimetry(DSC) and the gel time measurement were used to demonstrate the curing behavior; besides, and the viscosity of the hybrid adhesives and its bonding quality as well as formaldehyde emission of the panels were also measured. The results show that the addition of tannin resin had little effect on the structure of the hybrid adhesive, which still connected by methylene bond; compared with UF resin, the addition of tannin resin extended the gel time of the hybrid adhesive, but significantly reduced the formaldehyde emission of the panels, among the sample of panels, the tannin resin content on 5% and pH = 7 have maximum reduction for formaldehyde emission; the tannin resin synthesized under different pH conditions has a greater impact on the properties of the hybrid adhesive, that is, when pH = 7 and 9, the hybrid adhesive has better bonding strength, and pH = 4.6 and pH = 11 negatively affect the bonding performance; the addition of tannin resin in different proportions, includes 5%, 15% and 25%, has a greater impact on the bonding strength of the hybrid adhesive, that the bonding strength of the hybrid adhesive gradually reduces with the proportion of tannin resin increasing. After the veneer was treated by the sliding arc cold plasma, the shear strength of the plywood for hybrid adhesives have significantly improved that have the hot water resistance strength.