I am a bit confused and therefore turn to people who know more than I do.
Some time ago, I started considering manufacturing my own lightweight beams (wood/I-beams) as load-bearing construction parts for an upcoming house build, but I immediately encounter a hurdle, namely the type of glue.
There are basically three variants used, and they are:
1. Melamine-Formaldehyde.
2. Phenol-Resorcinol.
3. Polyurethane.
I have noted that some people as private individuals use PU glue when manufacturing I-beams, but the problem is that when I go through the datasheet for Cascol Polyurethane glue, it clearly states: "Not intended for load-bearing constructions" (Datasheet for Cascol Polyurethane 1809). In the datasheet available on the website for the same product, it states: "The glue is not intended to support wood constructions." Masonite Beams and Hunton use melamine (MF) glue for their beams, but Svenskt Trä points out that PU in construction, plywood, etc., is more common further down in Europe.
For example, I can read that SÖDRA uses formaldehyde-free PUR glue in their CLT construction: https://www.sodra.com/sv/se/byggsystem/komponenter/korslimmat-tra/
The PU/PUR glue available in stores is classified as Type 1, i.e., waterproof of D4 quality, in other words the same classification and requirements as the industry uses.
My question is: Is there a difference between the PU glue that the industry buys compared to what I can buy in the store?
Some time ago, I started considering manufacturing my own lightweight beams (wood/I-beams) as load-bearing construction parts for an upcoming house build, but I immediately encounter a hurdle, namely the type of glue.
There are basically three variants used, and they are:
1. Melamine-Formaldehyde.
2. Phenol-Resorcinol.
3. Polyurethane.
I have noted that some people as private individuals use PU glue when manufacturing I-beams, but the problem is that when I go through the datasheet for Cascol Polyurethane glue, it clearly states: "Not intended for load-bearing constructions" (Datasheet for Cascol Polyurethane 1809). In the datasheet available on the website for the same product, it states: "The glue is not intended to support wood constructions." Masonite Beams and Hunton use melamine (MF) glue for their beams, but Svenskt Trä points out that PU in construction, plywood, etc., is more common further down in Europe.
For example, I can read that SÖDRA uses formaldehyde-free PUR glue in their CLT construction: https://www.sodra.com/sv/se/byggsystem/komponenter/korslimmat-tra/
The PU/PUR glue available in stores is classified as Type 1, i.e., waterproof of D4 quality, in other words the same classification and requirements as the industry uses.
My question is: Is there a difference between the PU glue that the industry buys compared to what I can buy in the store?
Could it be that they simply do not want to take responsibility for such use?
Got a reply from Mats who works at Sika (Casco's parent company) and he simply says: "Yes, there is a difference," but he doesn't have enough information about the chemical differences. Only knows that there is so-called heat-curing polyurethane and that it is NOT the same as moisture-curing PUR that we can buy in the store.
On the other hand, I can somewhat understand the disclaimer as the producer (Casco-Sika) cannot control the environment for either the adhesive or its use. Since it is an expanding product, it is fundamental that the parts to be assembled are under pressure (if I may put it that way), and there it kind of falls apart since companies often have strict control bodies when it comes to production methods and equipment used.
On the other hand, I can somewhat understand the disclaimer as the producer (Casco-Sika) cannot control the environment for either the adhesive or its use. Since it is an expanding product, it is fundamental that the parts to be assembled are under pressure (if I may put it that way), and there it kind of falls apart since companies often have strict control bodies when it comes to production methods and equipment used.