Construction foam is a polyurethane-based sealant. The container contains a liquid prepolymer with functional additives, dissolved in liquefied gas. It is the compressed gas that allows the foam to actively get out of the cylinder. In solid form, the substance is polyurethane foam. A prepolymer and propellant are usually used as a displacing agent..
The polyurethane foam polymerizes, that is, solidifies, under the influence of moisture in the air and on the surface. That is, the drier the air in the room where you apply the foam, the longer you will have to wait for solidification..
Let us immediately highlight two main types of polyurethane foam – professional and household. At first glance, the main difference between professional foam is the obligatory presence of a special pistol, which helps to squeeze the sealant out of the container to the right place. The professional foam cylinder has a ring valve that can be screwed onto a similar valve on an assembly gun.
Household foam, unlike professional foam, is sold immediately with a plastic tube, which supplies the sealant. Experts note that it is much more convenient to work with an assembly gun – it is easier to control the process – the pressure and direction of foam application. The differences between household and professional foam do not end there – the second has much less secondary expansion, and this is a very important indicator, which we will talk about separately. And the rest of the quality characteristics of household polyurethane foam can be noticeably lower.
According to experts, it is better to buy a relatively inexpensive gun for professional polyurethane foam once, than entrust the household with such important matters as installing doors, window sills and windows.!
The polyurethane foam is also divided according to the temperature regime, within which it can be used:
|Type of polyurethane foam||Temperature range, ° C|
|Winter||-18 – +35|
|Summer||+5 – +35|
|All-season||-10 – +35|
As you can see, the upper limit for all types of polyurethane foam is the same; in 40-degree heat in the sun, you cannot work with it.
In addition, polyurethane foam is divided into flammability classes:
- B1 – refractory;
- B2 – self-extinguishing;
- B3 – combustible.
Of course, it is best to choose the first class, as the least fire hazardous..
Let’s move on to such important characteristics of polyurethane foam as primary and secondary expansion. The first time the foam expands as soon as it emerges from the balloon. This is a powerful expansion, several times, this should be considered when applying. The foam expands again during the hardening process, sometimes it can take up to 24 hours.
Important! The smaller the secondary expansion, the better, the less the danger that the window sill you installed will stand on end the next morning!
Professional polyurethane foam has a lower secondary expansion rate than household foam.
You should also pay attention to the following characteristics of the polyurethane foam:
- Output volume. Usually, numbers are written on the cylinder – 50, 60, 70 liters. This is exactly how much hardened product should be obtained from one cylinder. However, as experts emphasize, in fact, this indicator depends on various factors, including air temperature. The manufacturer simply indicates how much propellant is contained in the container at baseline conditions. In fact, the output is less.
- Viscosity. The polyurethane foam must not flow! If this happens, you may be outside the acceptable temperature range..
- Adhesion. This is the ability of polyurethane foam to attach to various surfaces. Do not apply foam on an icy surface, with the exception of polypropylene, oil, silicone, teflon, polyethylene. On all other surfaces, including metal, brick, wood, concrete, polyurethane foam is easily and reliably attached. Especially if you pre-prime.
Before you start working with polyurethane foam, we advise you to wear gloves, and first buy a special cleaner that will help you remove possible splashes and clean the gun. From the surface where the foam will be applied, brush off all the debris, it is advisable to walk with a brush or brush. If the surface is oily, be sure to use a cleaner.
Important! Before use, the balloon should be kept at standard room temperature for at least 10 hours! Even if you work outside in winter, the cylinder must be warm enough before use.!
Shake the can for about 30 seconds, then put on the gun or nozzle and start working. Experts advise filling vertical slots and seams with polyurethane foam from the bottom up, so that there is less chance that it will start to drain. And do not forget that the frozen foam after cutting off the excess should be protected with something, for example, putty.