| 초록 |
Natural adhesives derived from the renewable materials such as oils and carbohydrates are safe with low price. We have developed a practical process to synthesize formaldehyde free natural adhesives for wood binding. pMDIs were rapidly mixed with aqueous RP solutions right before applying to plywood veneers. Upon heating and pressing the plywoods, water in the PU adhesives may undergo rapidly vaporizing and absorbing through wood structure so that NCO functional groups of pMDIs react much more with OH groups of rice powder (RP) and cellulosic part of plywoods than water, forming chemical cross-linkages. Otherwise, isocyanates are reactive to moisture so that they form by-products such as polyurea and biuret-type structures. Thermal properties of formaldehyde-free (PU) adhesives synthesized from pMDIs and rice powder(RP) as a natural polyol were characterized by DSC and TGA. Thermal stability of formaldehyde-free resins increased to about 250℃ with adding pMDIs. |
