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12/17/18 | Adhesives

Sandwiches must be glued together!

Let us start this blog post with the sandwich in its most famous form: the edible one. Do you know who – allegedly – invented the sandwich?

John Montagu (1718 - 1792) was the 4th Earl of Sandwich in Kent County in the southeast of England. He was also a passionate cribbage player. According to a popular tale, during a particularly long-lasting card game in 1762 he found no time to eat and had his meal “sandwiched” between two slices of bread. As a result, another player also demanded a meal like Sandwich. The original sandwich thus consisted of three parts – a slice of beef between two slices of toasted bread.

Sandwich – a three or more part structure that is joined by high-performance adhesives to form a composite structure

For us at RAMPF Polymer Solutions, a sandwich is a structure made up of three or more parts. The so-called sandwich panel consists of one or more low-density core materials that are sandwiched between two relatively thin layers. By combining a core material, cover layers, and a high-performance adhesive, a composite structure is formed that exhibits high load-bearing capacity and rigidity, excellent dimensional stability and insulation, and boasts a wide variety of design options.

Sandwich constructions are found, amongst others, in

  • Facade elements
  • Door panels
  • Wall and roof panels
  • Building and construction elements
  • Caravans and motorhomes
  • Superstructures for commercial vehicles
  • Transport vehicles such as buses and trains
  • Furniture industry

How are sandwich panels made?

The sandwich adhesive, which is based on either polyurethane, silicone or reactive hotmelts, is applied to the core material (e.g. polystyrene foam, polyisocyanurate or rock wool). In addition, the sandwich adhesive is also applied to the shell (e.g. sheet steel, GRP, aluminum or stainless steel). Depending on application and company, this process can be carried out manually or with a dispensing system.

The adhesive can be applied in different ways:

  • Track/line application on core material or cover layer
  • Spray application under atmospheric pressure or high pressure
  • Roller application
  • Manual application with paint roller or trowel
  • Wiper method: separate application of A and B component followed by mixing

After the application of the adhesive, the layers are pressed together in order to achieve optimum adhesion.

What requirements do sandwich adhesives have to fulfil?

RAMPF adhesives for sandwich panels meet the requirements of industry – high aging resistance, UV stability, temperature stability, rigidity, and very good adhesion to various materials.

Further advantages:

  • Fast handling strength for high restoring forces
  • EU fire class A2 with low PCS value according to DIN EN 13501-1 / Part 1
  • Fire class B1 according to DIN 4102-1
  • IMO FTP Code / Part 5 (Marine Applications)

RAMPF's sandwich adhesive portfolio includes filled and unfilled 1K and 2K polyurethane adhesives that have a long open time, are fluid or stable, and have a broad adhesion spectrum. The viscosity ranges from 1,000 mPas to 300,000 mPas.

In addition, RAMPF develops and produces so-called hotmelts – reactive and thermoplastic hot melt adhesives that have a solid state at room temperature and are applied in liquid (melted) form. Adhesion develops when the adhesives cool below their melting point.

Advantages of reactive hotmelts:

Reactive hotmelts facilitate the rapid processing of the glued panels without the mixing process of the two components and the time-consuming pressing procedure that is usually required when using liquid systems. All RAMPF adhesives are free of NMP and NEP respectively, yet they exhibit excellent adhesion to various surfaces.

More information about our adhesive systems can be found here.