Thursday Afternoon, 15 October 2009

14.00 - 17.15h  SESSION 12
Chairman: Dr. Dietmar Dengler, DELO Industrie Klebstoffe, DE

ADHESIVES

Holding things together is the essential assignment of adhesives. Speed of production and afterwards durability of the bonds present main challenges for the application of glues. End-user processes with short cycle times can be realized by UV curing. Pressure-sensitive adhesives present another fast bonding technology, which often involves a UV curing step during the manufacture of the glues. Demands for the long term stability of bonds vary a lot, but are very high for structural bonding.
The presentations of this session will provide a deeper insight into the special parameters connected with bonding processes and highlight some new solutions for the formulation of efficient adhesives.

12.1 14.00 - 14.25h
Expanding the boundaries of cationic photoinduced curing adhesives
Dr. Markus Rojahn, DELO Industrie Klebstoffe, DE

Adhesives cured by a photoinitiated cationic mechanism are well known in industrial applications for more than two decades. As well known are their advantages (i.e. tack-free surface, good temperature stability, ability of preactivation) and their disadvantages (i.e. slow curing compared to radical systems, slow build-up of functional strength, moderate behaviour in humidity testing). Within the last years, several products have been developed to overcome these disadvantages and to work out more of the strengths of these special systems. This talk will focus on improvements concerning curing speed, time for the build-up of functional strength and humidity resistance of cationic photoinitiated-curing adhesives. Furthermore, some special advantages concerning oxygen and water barrier properties will be discussed.

12.2 14.25 - 14.50h
New opportunities in adhesives using photolatent base technology
Dr. Eva Peregi, Ciba Inc., CH

The cross-linking of suitable formulations by base-catalyzed polymerization and polycondensation reactions is well known for use in conventional coating applications and is highly attractive for certain applications. Furthermore, latent base catalysts are an attractive possibility to improve control over the curing process of such formulations while maintaining cure speed and the excellent properties of the cured article. The use of light as the trigger is very attractive in order to achieve optimum control over the curing process. Transferring the experiences from coatings, this paper will report on the design and the application of photolatent bases into adhesives formulations, as this technology is able to offer considerable economic and ecological advantages. It will show that this new class of catalyst considerably expands the scope of the UV technology into new formulations, thus providing the end user with the advantage of full control of the curing process, while producing adhesives of outstanding performance.

12.3 14.50 - 15.15h
UV Light - Challenges in structural bonding
Thomas Kowalik, Fraunhofer IFAM, DE

State of the art in structural bonding technology is usually a common high temperature curing system or a two component system which shows often difficulties in handling. Due to the latest regulations by law, like VOC and REACH and the increase of costs by using high temperatures, the relevance of other technologies, like UV curing, for structural bonding becomes higher again. Respectively the specific requirements different new approaches to introduce UV curing into structural bonding have been investigated. One way is pre applying of the adhesive to separate adhesive application from the bonding in the manufacturing line. Another way is the introduction of a dual cure mechanism in structural bonding. For all approaches the parameters time to cure in manufacturing line, storage time, handling strength and mechanical strength after the final cure are the key parameters which have to fit to the desired application.

12.4 16.00 - 16.25h
Cationic UV-crosslinkable acrylic pressure-sensitive adhesives
Roland Milker, ChemCycle Bitterfeld GmbH, DE

The most technological important and interesting features of radiation crosslinkable acrylic pressure-sensitive adhesives (PSA) being used for the manufacturing of various self-adhesive articles such as mounting tapes, splicing tapes, labels, sign and marking films and other self-adhesive products are photoreactive UV-crosslinkable systems. High performance acrylic PSAs offer several advantages such as excellent ageing characteristics and resistance to elevated temperatures and plasticizers, outstanding optical clarity due to the polymer compatibility, highest balance of adhesion and cohesion, non-yellowing and excellent water resistance. Solvent-borne or solvent-free cationic UV-crosslinkable acrylic PSA are unique because of the single nature of acrylic polymers anchored in the polymerization process along with a wide window of composition and modification. Such exceptional cationic UV-crosslinkable acrylic PSA are polymerized by involving monomers which contain oxirane groups such as glycidyl methacrylate, glycidyl acrylate or allyl glycidyl ether.

12.5 16.25 - 16.50h
Fabrication of high-performanced acrylic PSAs with nanofiller
Dong-Hyuk Lim, Seoul National University, KR

Acrylic PSA is composed of various monomer such as 2-HEA, BA, EA, VP, Vac, AA, GMA. High adhesion properties will be aquired by some methods: chemical composition using GMA, dual curable PSA and addition of nanofiller. In case of nanofiller system, the distribution technology of nanofiller is very important. In synthesis of PSA with nanofiller, in-situ photopolymerization method is very good process. In general, the periods of well-dispersed nanofiller phase is not long. So photopolymerized PSA with nanofiller has more dispersion properties than heat initiating PSA with nanofiller.

12.6 16.50 - 17.15h
A comparison of raw materials used in laminating adhesive formulations, cured with UV or EB
Michael Gould, Rahn, USA

END OF CONFERENCE