Elastic Sealants and Adhesives

Technology  Reaction Mechanism  Characteristics  Applications  References  Innovations

Technology
Elastic Bonding is the strength bearing joining of dissimilar parts with the goal to absorb dynamic forces and expansion due to temperature.

An Adhesive is considered elastic when under high mechanical strength its capacity of extension is a multiple of a hundred percent. Through this high elasticity an even distribution of impacting forces is achieved along the dissimilar parts. Consequently stress within the bonded material is normally avoided.

Due to increased design possibilities, easy automation opportunities and cost and time reducing assembly processes, elastic adhesives based on polyurethane technology replace more and more other assembly technologies.

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Reaction Mechanism
Polyurethane adhesives mostly contain isocyanatic polyurethane prepolymers which react with humidity and form highly crosslinked elastomers

By choosing appropriate binders and additives, the adhesion characteristics can be modified and adapted to various substrates like glass, various metals, plastics and paints, leading to durable adhesion.

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Characteristics
With polyurethane adhesives and sealants many characteristics of the bonded connection can be influenced. Sika's core competence in this sector allows...

• ...to avoid contact corrosion using adhesives with low conductivity
• ...to strengthen bonded construction parts using adhesives with modulus as high as 40 MPa
• ...to pass successfully crash tests within one hour of the bonding of the vehicle due to accelerated curing processes
• ...to absorb tensions and forces arising just after the assembling (even when the adhesive is not fully cured)
• ...to bond difficult substrates like polypropylene other equivalent plastics

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Applications
As biggest producer in the world of humidity-reactive polyurethane adhesives and sealants,  Sika offers products with the trademark name "Sikaflex" for many different applications. In the Construction Division, the products are mainly used as joint sealers and for the bonding of parquets. In the Industry Division, "Sikaflex" products are being used in the automotive and transportation industry to bond modules like windows, roofs and wheel arches, and in the marine market. Increasingly, applications can be found in the bonding of washing machines, fridges and building components like elevator components.  

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References
Professional know how and highly innovative products made Sika a prime supplier and development partner of such world class companies as DaimlerChrysler, BMW and the Volkswagen Group.

Some highlights in the last years

• 1997: Introduction of the first seam-sealer with adhesion on topcoat used on the Mercedes A-class
• 1999: First bonding of a complete glass roof module at DaimlerChrysler
• 2001: First serial application of an accelerated 1K Polyurethane-assembly adhesive in the automotive line-production (Audi A2: Bonding of glass and plastic parts)

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Innovations
SikaTack High Module:
With SikaTack High Module, Sika completes the range of products in the area of windshield repair adhesives. This new product is characterized by:

• high modulus
• low conductivity
• antenna suitable (fulfills the highest standards)
• cold applied
• highly reactive, allowing a "safe drive away time" of 1 hr (without airbag), resp. 3 hrs (with airbag)

Sikaflex-552:
With Sikaflex-552, a new construction adhesive is available which offers, due to its excellent adhesion characteristics, big advantages in the application. This adhesive allows the bonding of materials like aluminum and GRP (Glass Reinforced Plastic) without any pre-treatment. Furthermore it shows an exceptional high mechanical strength, something very untypical for this kind of adhesive.