Sika adhesives

Before the application of the adhesive, the bonding surfaces have to be prepared. To clean the surfaces properly, the aluminum of the chassis is grit-blasted (corundum 20-30 pm grit) and the GRP of the cabin is ground with a very fine grinding pad. Then, any dirt and dust particles are removed with the Sika Cleaner-205 and brushed with a suitable Sika Primer. Then the cabin is set onto the chassis in the correct position using polyurethane distance holders to control the adhesive thickness, before Sikaflex -254 Booster is injected into the joint with the booster pump equipment, pressed, and skinned into the joint with a spatula. A small gap with a depth of 5 mm has to remain later, this gap is filled with Sikaflex -265 to achieve a durable seal. 

Sika internal studies and those made in cooperation with a car manufacturer carried out in 1996 showed that the primerless system provides good durable adhesion and outperforms black primer systems for bonded auto windscreens. The studies showed that not only UV, but also other factors contribute to the degradation of the adhesive system such as humidity, working conditions, application. 

The Sikaflex -555 direct glazing adhesive possesses the highest mechanical properties of products currently in Sika PUR-Hybrid product range (Fig. 84). The lap shear, tensile and tear strengths are higher than those of comparable MS-products. 

In the early 1980s, Sika diversified into the chemistry of elastic adhesive bonding for industrial applications. With eight production centres in three continents, Sika is now the world s largest manufacturer of one-component polyurethane adhesives and sealants. The customer oriented solutions and services of the Sika Industry Division are marketed to the following market sectors, where they are the leaders in their field ... 

Acrylic 87 Epoxy 212 - 3 Polyurethane 285 Silicone 316 Miscellaneous 374 Sichel, Cyanoacrylate 140 - 4 Sicomin, Epoxy 213 Sika, Polyurethane 285 - 6 Structil, Epoxy 213-5 Structural Adhesives Ltd. 

Chapter 7 Flexible bonding, by Dr Burchardt, Sika Switzerland Volume 3 Adhesives and sealants for construction, woodworking, etc. 

Polyurethane chemistry and adhesives and sealants is such a large and important topic that several chapters will he spent covering this subject A general chapter in Volume 1 (written by a team of scientists from Loughborough University in the UK), PU sealants in Volume 3, PU flexible adhesives and sealants by Sika in Volume 2 and again in Volume 5 probably, and PU adhesives for laminating and packaging in Volume 4 by Bostik-Findley. 

This explains that adhesives suppliers first developed in the seventies the so-called toughened epoxies, flexibilized by addition of a small amount of cross-linkable rubber, and then recently the company SIKA pioneered the so-called flexible structural bonding in which they use PU adhesives derived from their experience in PU sealants, to get semi-structural bonds, for instance, for transportation and automotive or naval uses. 

Fig. 43 shows that a flexible, semi-structural PU adhesive giving only 6 MPa tensile strength may require greater work to break the bond than a high-tensile strength structural epoxy. The reader should refer to the chapters Flexible structural bonding by SIKA, and Epoxy adhesives by 3M, in following volumes of this Handbook. 

For a detailed study of PU adhesives for transportation, automotive, etc., the reader may refer to the chapters Elastic Bonding and Sealing by SIKA in Volume 2 and Flexible Structural Bonding also by SIKA in the next volumes of this Handbook. 

Direct glazing is a common application in the automotive industry since the polyurethane sealant can perform the important functions of adhesion of glass directly into the metal frame, cope with the vibration and movement and still remain weather tight. The Sikaflex -255FC is a one-component compound from Sika which, because of permanent elasticity and excellent adhesion to metal, glass, and many other materials, is ideal for the automotive industry. 

Hull to deck assembly using a polyurethane adhesive, (a) Adhesive placement, (b) Guide pin to ensure alignment (photos Sika) (Sika 2009)... 

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