Urea Resin – Plastic Powdered Resin (PPR) – White
Urea resins are a truly versatile adhesive, capable of most wood to wood assembly gluing, face and edge gluing, solids and wood veneers. Urea resin glue line characteristics are strong, rigid, thermoset, Type II water resistance and excellent heat resistance. PPR can be hot pressed, cold pressed, vacuum pressed and radio frequency cured.
Water is necessary to restart the chemical reaction. The amount of water used should be 50-65% of the weight of the dry powder to be mixed.
*65% is the ideal amount of water to 100 parts resin powder by weight. Luke warm water will help the glue mix faster and easier.
*Add 2/3 of the required amount of water to the powder in the mixing container
*Slowly add the powder, while stirring the mix on slow rpm (<2000) with a mechanical agitator
*Continue mixing for 3-5 minutes, using a spatula to scrape powder from the sides back into the liquid. Mix should be creamy and virtually lump free at this point
*Add the remaining 1/3 of water and mix for an additional minute. Mix should be smooth, creamy and lump free.
Spread rate will largely depend on the nature of the work being done and the method of cure employed. This spreads are critical when working with raw veneer in order to reduce the effect of bleed through. Bleed through is glue seeping through the pores of the veneer and showing on the face of the panel. Be aware of the thickness and porosity of the veneer species you are working with and adjust your spread accordingly. In many instances, a thin spread coupled with a mandatory open assembly time (up to 10 minutes) will be necessary to prevent excessive bleed through.
The amount of glue squeeze out while under pressure is a good indicator of a good spread rate. Remember, it is not only the amount of glue, but also how consistently it was applied and squeeze out can indicate both of these factors.
Once mixed with water, the resin will gradually cure until it is unusable. The amount of time from when the glue is first mixed until it becomes unusable is called pot life. As with all glues this is a dynamic value. It will change primarily with temperature. Hotter temperatures will yield a shorter pot life. It is recommended that the glue be used at a minimum temperature of 70 F
*At 70 F pot life will be ~5 1/2 hours and at 90 F it will be 3 hours.
*The glue will continue to cure until it is rock hard, usually within 24 hours.
*Only experience and a careful eye will tell you the point when the mix is unusable. It is best to err on the side of performance rather than yield. When it has thickened to the point that it is not spreading well, consider the mix unusable.
Urea resins offer generous assembly times, making them ideal for intricate work requiring longer layup time. Once again these are dynamic, depending on spread rat, substrate porosity, veneer porosity, moisture content, stock temperature and ambient temperature.
As temperature increases, allowable assembly times decrease. Maximum assembly time at 70 F it is 40 minutes and at 90 F it is 20 minutes.
Ureas are water based poducts and therefore can be cleaned up with water. Warm water is preferred as hot or cold water will make clean up more difficult. Scrape out as much of the glue as is easily possible before adding water. The extra glue is allowed to cure completely and then it can be discarded in a solid waste container.
As withe the use of any industrial chemical, proper care should be taken when handling urea adhesives. These are outlined in the SDS, available on our website under the downloads section in veneer adhesives.