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Structural adhesives

Right down to the last drop: One advantage of the new gel
products from Armacell is that hardly any adhesive is wasted

Elastomeric insulation materials not only have good technical properties, they are also very user- friendly due to their high flexibility and ease of application. When installing these insulation materials it is crucial that they are glued professionally. Therefore, Armacell offers a broad range of accessories specifically developed for its products and regularly adds innovative solutions.

These adhesive products are simpler and quicker to apply with very little wastage involved. They are also odourless and emission free and provide longer shelf storage life. Alongside the tried-and-tested contact adhesives such as Armaflex 520 adhesive, interesting alternatives are now also available. Armacell recently launched a completely new generation of adhesives which make the installation process even easier and allow elastomeric insulation materials to be used in projects with the highest environmental and health standards. Apart from presenting the latest developments in adhesive technology, this article takes a look at the advantages and disadvantages and the fields of application for the new adhesives.

New thixotropic (gel-like) adhesives such as the new Armaflex RS850 are drip-resistant and guarantee neat application which has advantages for awkward installations where spillages would be hard to contain. The gel consistency and viscosity of these products provides a great benefit when working overhead or when it is important that the insulation is not soiled by drips of adhesive.

The term thixotropy (made up of the Greek words thixis - "touching" and trepo - "I change") refers to the viscosity of gel-like substances depending on mechanical forces, with the adhesive gel-like in its static condition (when the adhesive molecules are interlocked) and fluid when brushed.

When energy is applied to the adhesive it is activated, the flow behaviour changes and the viscosity falls and can be spread like a traditional contact adhesive: thinly and evenly over the whole surface area. The product's gel-like condition prevents it from spilling if the container is overturned.

Technical data
Gel adhesives can be used to install elastomeric insulation materials on plant which operates within a temperature range of -40 to +70°C. This covers over 90% of typical application cases. Another benefit compared to traditional contact adhesives is that gel products cure faster. Whereas it is usually necessary to wait 36 hours, plant can be put back into operation just 24 hours after this adhesive has been applied. The shelf-life is also extended with unopened containers able to be kept for 36 months (from filling date) compared to the typical 12 month shelf-life of contact adhesive systems.

Image 1:No drips: the gel-like consistency of the new Armaflex adhesives means that they can be applied evenly, neatly and economically.

Image 2: Right down to the last drop: one advantage of the new gel products is that hardly any adhesive is wasted.

Image 3: The new Armaflex RS850 products can be applied more economically and precisely with no drips of adhesive soiling the insulation material.

When applying gel adhesives, the ambient temperature should ideally be between +15 and +25°C during the installation. It should not fall below +10°C because the reaction of the adhesive is restricted and it is harder to apply. If the temperature during the application is too high (above +30°C), the adhesive liquefies and is no longer as drip-resistant. As is the case with contact adhesives, the relative humidity should also be below 80% when gel products are applied.

Like contact adhesives, tack-drying is an aspect which must always be taken into account. After the adhesive has been applied thinly and evenly to both surfaces, the solvents must evaporate. The tack-drying time depends on the amount of adhesive applied, the temperature, relative humidity and wind speed. As with the Armaflex 520 adhesive, it is necessary to test with a fingertip to determine when the adhesive is no longer 'stringy'. This is the earliest point at which the Armaflex pieces can be joined. However, it is better to add extra waiting time before closing the seam. It is important that as little solvent as possible is trapped. The so-called open time (the period between the application of the adhesive and the latest possible time for joining the insulation pieces) is comparable to that of contact adhesives of normal viscosity.

In spite of their different properties, thixotropic adhesives are very similar to contact adhesives in terms of use. In addition to the application benefits, the gel substance has very little wastage since whilst traditional contact adhesives often thicken and harden significantly during the installation work and can then no longer be applied, the gel product encapsulates the solvents due to its high viscosity.

The reduced release of solvents is a further advantage: in the gel state the "locked-in effect" ensures that only minimal amounts of solvent are released into the ambient air which is important for confined spaces such as ship building and in all areas where strong odours must be avoided. Today buildings in the public and private sector are increasingly planned and constructed on the principle of sustainability. Construction materials used in buildings certified under BREEAM (Building Research Establishment Environmental Assessment Methodology) or a comparable national scheme place a greater demand for reduced solvent adhesives.

The thixotropic Armaflex RS850 adhesive can be used to install all Armaflex products (except the specialised HT/Armaflex and Armaflex Ultima). For gluing Armaflex Ultima and other insulation materials based on Armaprene® synthetic rubber, Armacell has developed corresponding versions of the adhesive. For these products too, a gel-like, drip-free product (Armaflex Ultima RS850 adhesive) is available in addition to the Armaflex Ultima 700 standard contact adhesive. These adhesives for the new blue insulation materials are also blue in colour and are only approved for installing these products.

The new adhesive systems are the result of focused research and development work and have undergone rigorous application tests. They are specifically developed for the various Armaflex materials and are subject to continuous quality inspections by Armacell's quality management system. In this way the insulation manufacturer ensures that its insulation systems work in the long term. In the field of technical insulation, perfect results can only be achieved if the adhesives are optimally coordinated with each other, tested as a system and installed professionally.

Armacell in profile
Armacell is a manufacturer of technical foams and the world leader in the market for flexible technical insulation materials. In the financial year 2012, the company had a gross annual turnover of around 475 million Euros. The group of companies has approximately 2,420 employees and 19 factories in 13 countries. It is headquartered in Münster, Germany. Apart from ARMAFLEX, the leading brand in the field of flexible technical insulation, the company also produces thermoplastic insulation materials, covering systems, fire protection and noise control products, special foams for a multitude of industrial applications and foam cores which are used as composite materials.

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