A liquid-state thermosetting Urea Formaldehyde Resin (UFR) which meets all the requirements of a Type II Adhesive. The resin is best suited for manufacturers capable of storing and handling bulk type shipments. This product is recommended for manufacture of Plywood, Particle Board, Medium Density Fiberboard (MDF), and other wood works especially products for interior use.
PRODUCT SPECIFICATION
- Form: Liquid
- Color: Milky white
- pH: 7.0 – 8.0 (at 30°C)
- Viscosity: 60 – 160 cPS (at 30°C)
- Solid Content: 50 – 51%
- Gel Time: 130 – 160 min
- Specific Gravity: 1,190 – 1,196 g/cm3 (at 30°C)
- Free Formalin: 0.8 – 1.2%
- Shelf Life: +/- 1 month
INTERNATIONAL STANDARDS
Urea Formaldehyde Resin complies to the following international standards:
| UK | : BS-1455 Type MR and INT |
| USA | : C-35-36 Type II and III |
| Germany | : DIN 1-74 PS 51-71 INT GRD |
| Japan | : JPIC Type II and III |
RECOMMENDED FORMULATION
The following mixing formulation is recommended so the Urea Formaldehyde Resin achieves its best performance.
| Urea Formaldehyde Resin | : 100 parts by weight |
| Industrial grade wheat flour as filler | : 10 – 20 parts by weight |
| Hardener | : 0.5 – 1.0 part by weight |
| Water | : 2 – 6 parts by weight |
MIXING PROCEDURE
Mixing procedure for Urea Formaldehyde Resin differs on the speed of the stirrer:
– For High Speed Stirrer
Pour in all of the Urea Formaldehyde Resin and wheat flour, and mix them for about 5 minutes. Next, add the Hardener, followed by water. Prior to use, stir for a further 10 – 15 minutes to ensure the mixture is well-mixed.
– For Low Speed Stirrer
Pour in half of the Urea Formaldehyde Resin and all of the wheat flour, and mix them for about 5 minutes. Next, pour the remaining Urea Formaldehyde Resin and all of the Hardener , and finally add water. Before usage, stir for 10 – 15 minutes more to mix it better.
POT LIFE
The above recommended formulation will have a pot life varying according to environment or room temperature, as follows:
| Room Temperature | 20°C | 25°C | 30°C | 35°C |
| Gel time/pot life (hours) | 14 | 10 | 8 | 4 |
VENEER PREPARATION
Before assembly, veneer faces must be cleaned to be smooth and free of dust, glue stains, etc. The veneers must be uniform in thickness. Moisture content of the veneers must be maintained at about 8 – 12% for face and back veneers, and at about 8 – 16% for inner cores. High moisture content will increase the risk of getting punks (rejects) because it will need higher pressing temperature.
GLUE SPREAD
Glue spreading should use double glue line, using about 30 – 36 g/sqft of glue mix, to be adjusted according to veneer quality. Thicker veneers require more glue spread amount due to having rough faces. High Density Wood must have about 10% increased glue spread amount than Low Density Wood (Meranti).
PRE-PRESSURE
Lay up time is required in pre-press to transfer glue mix from spread core to veneer for suitable penetration. It is important to avoid early curing, for example too low glue spread for low moisture content, especially in hot and dry climate condition. The pressure on cold press must be lower than that of hot press. Suitable pressure is thus determined by working conditions, although good results are usually obtained at about 9 – 10 kg/cm2. Cold press time also depends on operating conditions, normally 15 – 25 minutes.
PANEL ASSEMBLY TIME
The assembly time must generally be as short as possible, and the glue mix must still be viscous when pressing is performed. Although the glue is rather dry, when it is bonded at 110°C, it can achieve good adhesion if the pressure and pressing time are increased.
HOT PRESS TIME
Basic setting time for the above recommended glue mix formulation varies depending on the press temperature, as follows;
| Press Temperature | 90°C | 100°C | 110°C | 115°C |
| Basic Setting Time | 1.75 min | 1.50 min | 1.00 min | 0.85 min |
To have enough time for heat transfer, it becomes necessary to add additional time to the basic setting time above. The amount of additional time varies depending on the distance from the press plate to the Farthest Glue Line (FGL). That additional time (minutes/mm) according to the FGL is as follows:
| Distance to FGL | Press Plate Temperature | |||
| 30°C | 30°C | 30°C | 30°C | |
| Below 5 mm | 1.1 | 1.0 | 0.9 | 0.85 |
| 5 – 10 mm | 1.3 | 1.2 | 1.1 | 1.0 |
| Over 10 mm | 1.5 | 1.4 | 1.3 | 1.2 |
Example One: 3-ply panel of 2.5 mm core and 1.0 mm face and back veneers. The required press time at 110°C is as follows;
| Heat transfer time | 1.0 mm x 0.9 minute/mm = | 0.9 min |
| Basic setting time | = | 1.0 min + |
| Total pressing time | = | 1.9 min |
Example Two: 7-ply panel of 2.5 mm inner cores and 1.0 mm face and back veneers. The required press time at 110°C is as follows:
| Distance to FGL | (1.0 + 2.5 + 2.5) mm = | 6.0 mm | |
| In this case, | |||
| Heat Transfer Time | 6.0 mm x 1.1 minute/mm = | 6.6 min | |
| Basic Setting Time | = | 1.0 min + | |
| Total Pressing Time | = | 7.6 min |
Note: Heat transfer speed will depend also on the wood species and moisture content. Therefore the table above is only a general indication for the required additional time.
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