Many do-it-yourselfers have a kind of love-hate relationship with Styrofoam panels. The material is valued for its technical properties, but at the same time despairs of its processing. How the gluing succeeds and which glue is suitable for Styrofoam is clearly explained here.
Polystyrene is one of the most commonly produced plastics. Most people know it foamed up by its sales name Styropor. While some appreciate the good insulating properties, the low weight and other positive aspects for a wide variety of uses, others flatly reject the processing of polystyrene.
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Glue styrofoam plates
One reason is always the difficult processing and above all the struggle with the adhesive. We explain which technique you can use to glue Styrofoam panels without despair. We also explain which glue is suitable for Styrofoam and which ones should be left alone.
In order to be able to understand the peculiarities of the processing of Styrofoam, one must first know the material itself. Because its composition already explains a lot of what can become a problem in the course of the work in the case of ignorance.
Actually, the term polystyrene does not describe a material. Rather, it is a brand or trade name that has meanwhile found its way into usage, just as “Tempo” is representative of all paper handkerchiefs today. Styrofoam is made from polystyrene, the fourth most common plastic. This makes it one of the normal plastics that can be found in a wide variety of forms in households, trade and technology.
In order for polystyrene to become styrofoam, the plastic is foamed with the help of heat, in technical terms it expands. In technical terms, one therefore also speaks of EPS (expanded polystyrene). With typical Styrofoam, the plastic granulate used as the starting material is still recognizable as small balls that are joined together to form a tight bond.
The essential properties of the polystyrene foam produced in this way are:
- high elastic deformability
- high absorption capacity for vibrations and shocks
- closed-cell, fine-pored structure
- low moisture absorption
- low solvent resistance to e.g. ketones and aldehydes
- low temperature resistance
- high UV sensitivity
The most common form in which the foamed plastic is sold for a wide variety of applications around the home and hobby room are panels of various thicknesses and dimensions. But molded parts can also be found again and again, especially in the field of building services, but also in model making.
If you now know the essential properties of styrofoam, it is quite easy to derive from this knowledge which properties an adhesive for styrofoam must have.
- high elasticity to accommodate possible deformations of the styrofoam
- Adhesion and setting ability on non-absorbent substrate
- Composition without relevant solvents
- no thermally activated adhesives above the melting point of styrofoam (e.g. “hot glue”)
- no UV activation of the adhesive required
Practical examples of suitable adhesives
Now, from the variety of products available on the market, a range of suitable products can be easily put together based on the requirements for suitable adhesives for gluing Styrofoam panels. It is noticeable that the individual adhesives vary greatly in their consistency, composition and processing.
That depends above all on the intended use, i.e. on the surface on which you want to glue the polystyrene plates. An adhesive for styrofoam on masonry as insulating material looks completely different from an adhesive for gluing styrofoam components to each other because of the mineral, mostly very uneven and also absorbent to sandy substrate. Typical products are therefore presented below as examples and the bonding of the Styrofoam panels to them is explained.
- Polyurethane foam (PU), typical construction and assembly adhesive
- usually as a cartridge with propellant, adhesive expands when it exits the cartridge
areas of application
- Fastening of insulation panels on mineral substrates such as stone and concrete, as well as on wood – due to the small cartridge content especially suitable for small areas and auxiliary work.
- Due to the space-filling effect of the adhesive, it is well suited for bridging gaps in the substrate
Adhesive Foam | instructions
If Styrofoam panels are to be glued with adhesive foam, it is best to proceed as follows.
- Remove dust, dirt and loose components from the surface
- Provide the adhesive cartridge with a nozzle according to the instructions
- Apply adhesive foam in even snakes to the styrofoam board
- Immediately align the panel with the substrate and press firmly until the adhesive effect occurs
- If necessary, readjust panels, as adhesive foam can easily expand and move panels, even in a “non-pressing” form.
- Also apply an adhesive strip to the front of the follow-up plates and press the plates firmly against each other.
- Fill any gaps between panels with adhesive foam, cut off the foam after it has hardened (e.g. with a cutter knife)
NOTE: Since the PU adhesive foam itself takes up a certain amount of space, care must be taken to ensure that it is applied evenly. If the adhesive snakes are applied too far apart or if too much foam is applied at certain points, cavities can form between the Styrofoam panel and the substrate, which reduce adhesion and, above all, reduce the usually desired insulating effect.
The same applies to defects in panel joints. Gaps in the adhesive create thermal bridges, which in total can significantly reduce the insulating effect.
- Synthetic elastomer based aerosol adhesives
- Ready-to-use, pressurized spray can
Areas of application:
- Bonding of insulation panels on very flat substrates, due to small container sizes especially for small areas, well suited for bonding Styrofoam panels to each other.
- low application thickness, therefore no filling effect on imperfections.
- very short flash-off and setting time, therefore bonding without the panels sagging or the adhesive penetrating.
- However, readjustments are hardly possible.
spray adhesive | instructions
The processing of styrofoam with spray adhesive works like this:
- Clean the surface, eliminate defects or unevenness by filling or sanding.
- Prepare the boards to fit perfectly and ideally check them briefly in the planned position before gluing.
- Spray the adhesive onto the bonding surfaces of the insulation board (rear and front sides).
- After the specified drying time, position the panel and press firmly
ATTENTION: In contrast to PU foams, any gaps between the Styrofoam panels cannot simply be filled with spray adhesive afterwards. If there are gaps to be filled, other fillers, such as adhesive foam, must be used for the rework.
Acrylate dispersion adhesives
- Pasty adhesive based on acrylate
- mostly bucket goods, rarely cartridges
areas of application
- Bonding of styrofoam on absorbent surfaces such as masonry, concrete and wood
- high filling effect, therefore also suitable for uneven surfaces or for bridging imperfections
Acrylate dispersion adhesives | instructions
The most common way of gluing Styrofoam panels in house construction, renovation and modernization is to use dispersion adhesives in the following way.
- Remove loose components from the surface
- Apply a leveling primer to highly absorbent substrates
- Level extremely uneven surfaces with a filler beforehand
- Apply the dispersion adhesive to the surface using a notched trowel and wait for the specified drying time
- Push the styrofoam plates tightly into the adhesive bed and align
- When gluing to the wall: due to the long setting time, mechanically support the bottom row of panels to prevent sagging, for example by placing wood underneath or using plate dowels in addition to the adhesive
ATTENTION: Very pasty dispersion adhesives are only conditionally suitable for gluing the front sides of the panels. Here you should pay attention to a corresponding information from the manufacturer. Alternatively, the panels can be connected to each other with other adhesives, such as adhesive foam or spray adhesive.
adhesive and sealing compounds
Today there are numerous specially developed adhesives with special properties for special areas of application. The most well-known of these are polyurethane-based adhesives and sealants. They create elastic, highly effective connections between the styrofoam panels and substrates ranging from wood and metal to fiberglass and glass. Due to their high elasticity, they are very well suited for use in the area of expansion joints.
Due to the high degree of specialization of the individual products, however, no generally applicable instructions can be written. The information provided by the manufacturer should be studied before use.
Reactive hot melt adhesives
One of the most modern types of adhesive for Styrofoam are the so-called hot-melt adhesives. They liquefy the surface of the Styrofoam through the development of heat and thus create an extremely strong and non-positive bond, especially between Styrofoam panels. However, since these adhesives are not practicable in the do-it-yourself sector and are mainly reserved for the technical sector , no further explanation of the processing is given at this point.
In addition to the actual gluing, the question of what happens to the residues of the adhesives used in the do-it-yourself processing of Styrofoam panels arises at the latest after the end of the actual work. Since the adhesives, like the actual foam sheets, are ultimately chemical products, any disposal should be avoided.
Since the adhesives are not critical when set, small residual amounts can be applied to a leftover piece of Styrofoam, aired and hardened. They can then be professionally disposed of together with the Styrofoam residues at the landfill or at the recycling collection point. Due to the high reactivity and the substances contained, larger quantities of adhesive should be disposed of at a hazardous waste collection point.
Finally, when gluing Styrofoam panels, you should always be aware that – no matter which adhesive you use – Styrofoam can generally only generate relatively weak adhesive forces on its surface. This is mainly due to the surface quality and the closed-pore structure.
Especially with construction measures using Styrofoam, you quickly get into an area where additional mechanical fixings of the insulation boards may be necessary. In most cases, so-called plate dowels are then used, which fasten the plates through the insulating material into the solid substructure using large plates. In the case of subsequent installation of Styrofoam on plastered walls and similar components, their use is even prescribed for the most part.