Modification and Performance of Magnesium Oxychloride Adhesive for Plywood
To improve the bonding strength and water resistance of plywood made with magnesium oxychloride adhesive,phosphoric acid and nano-silicon dioxide were used as modifiers.The properties of magnesium oxychloride adhesive and plywood prepared by adding single and composite modifiers were analyzed.The results show that the modification with phosphoric acid and nano-silica can improve the physical and mechanical properties of magnesium oxychloride adhesive.The effect of the composite of the two modifiers with an optimal proportion is better than that of either one single modifier.When phosphoric acid and nano-silica are added at the same time with a ratio of(calculated by MgO mass)1%and 3%respectively,the softening coefficient of the modified magnesium oxychloride adhesive can reach 0.95.The analysis results from Fourier transform infrared spectrometer,X-ray diffractometer,and scanning electron microscope show that the modifier does not chemically react with the magnesium oxychloride adhesive,but changes the state of 518 phase crystals and the filling of pores by nano-particles,which prevents the hydrolysis of 518 phase crystals,inhibits the generation of Mg(OH)2,and forms a denser structure.The dry and wet bonding strengths of plywood prepared with optimal modified magnesium oxychloride adhesive can reach 1.51 and 1.25 MPa,which meets the requirement of≥0.70 MPa of GB/T 9846-2015 Plywood for general use.
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