substitution furfural instead of formaldehyde in urea formaldehyde resin and improvement resin properties using nano clay

Background and Objectives: Urea Formaldehyde resin is an important rein in wooden panel industries. Compared with other amino resins, this resin is cheap and colorless when it is polymerized. It is used easily since its solvent is water. But it has some disadvantageous such as its low resistance to moisture and its emission during production and service which is harmful for human health. Researchers are conducting massive investigations to substitute formaldehyde in urea formaldehyde resin with other non harmful materials. Furfural is an aldehyde chemical material which react with urea as formaldehyde do. Furfural can be obtained from crop products such as wheat straw, corn stalk and sugar cane. In this study substitution of furfural instead of formaldehyde for making urea furfural resin and improvement of resulted resin using nano clay were investigated.
Material and Methods: Furfural and urea were mixed with molar ratio of 1 to 1, 1 to 2.2 and 1 to 3.5. Lap -sheer strength test was conducted to evaluate bond strength. Beech strands were dried before gluing. Ammonium chloride was used as hardener. Strand ends were glued using urea furfural resin and assembled. After resin curing in oven, assembled were tensile loaded and tensile strength was measured. 10 samples from each urea furfural resin were prepared for tensile test and tensile sheer strength were measured. results showed that urea furfural with molar ratio of 1 to 2.2 is the best among others. This resin was selected for next step of resin preparation. Nano-clay with amount of 0.5 %, 1 % and 2 % [oven dry wight of resin] was added to urea furfural resin with molar ratio of 1 to 2.2 and resin properties such as density, solid content, viscosity, gel time and bond shear strength were measured. Spectroscopy FTIR, Imaging FESEM and XRD for study reaction of nano-clay and its distribution in the resin were conducted.
Findings:
Results showed that urea furfural resin with molar ratio of 1 to 2.2 with the highest bond sheer strength is the best resin among others. Nano clay at three levels of 0.5%, 1% and 2 % was added to the best resin of urea furfural and caused improvement in resin properties. So that solid content of resin increased from solid content of control (resin without nano clay ) from 56 % to 56.5 %, 56.65%,and 56.8% respectively for adding 0.5%, 1% and 2% nano clay. Density of resin increased from 1.1 gr/cm3 for control to 1.135, 1.14, and 1.145 gr/cm3 for adding 0.5%, 1% and 2% nano clay. Viscosity from 95 second for control to 135,140,143 seconds respectively for adding 0.5%,1 % and 2%nanoclay. Bond shear strength from 1.7 MPa for control to 2.7,0.6 and 0.8 MPa respectively fot 5%,1% and 2% nano clay. Gel time reduced from 180 seconds for control to 160, 145,140 seconds respectively for 0.5% ,1% and 2% nano clay.
Conclusion:
Findings of this study showed that free formaldehyde urea furfural resin with urea to furfural molar ratio of 1 to 2.2 has the highest bond sheer strength (1.62 MPa) and adding 0.5 percent Nano clay to this resin caused an improvement in its bond sheer strength, density, solid content, viscosity, and gel time. Improvement by adding nano clay up to 5.0% was noticeable but improvement by adding higher levels of nano clay was low. Regarding above results it can be concluded that produced urea furfural with urea to furfural molar ratio of 1 to 2.2 and adding o.5 % nano clay is a suitable substitution for urea formaldehyde resin which can be recommended for particleboard and medium density fiberboard industries.