Adhesives future trends

Several environment-friendly surface preparation for the treatment of mbber soles with radiations have been recently studied. These treatments are clean (no chemicals or reactions by-products are produced) and fast, and furthermore online bonding at shoe factory can be produced, so the future trend in surface modification of substrates in shoe industry will be likely directed to the industrial application of those treatments. Corona discharge, low-pressure RF gas plasma, and ultraviolet (UV) treatments have been successfully used at laboratory scale to improve the adhesion of several sole materials in shoe industry. Recently, surface modification of SBR and TR by UV radiation has been industrially demonstrated in shoe industry... 

Besides durability, premium sealants are judged by special properties as shown in Table 4. The ability to take on greater elongation and compression is measured by movement capability in terms of joint width. The stability to UV exposure is important for those glazing and insulation compounds used in modern high-rise structures. Thermal stability is in demand for solar collectors, or for other structural materials. On the basis of these evaluations, we can foresee future trends of sealants as shown in Table 4. Silicones appear to out-perform others. In the meantime, technical advances will provide low-modulus polysulfides, and better movement ability for both polysulfides and polyurethanes. Their cure time will be decreased and the UV stability will be improved to match or compete with silicones. All three will be developed for better adhesion under the un-primed conditions. 

As a record of this successful Conference, all papers (after revision) presented to the Symposium and the discussions during the meeting are now published in these Proceedings. In addition, the contributions shortly after the Conference in projecting future trends of adhesive research are also included. As a result, the new title for the volume becomes "Adhesive Chemistry - Developments and Trends." The six parts following the original order of the Conference are ... 

Abstract Biotextile sterilization presents unique challenges. The chapter describes the principles of sterilization and the way in which sterility assurance levels are defined and demonstrated.Traditional thermal, chemical and radiation sterilization methods are described, as well as newer methods such as plasma and microwave sterilization, and applications for which each is suitable. The advantages of the emerging technology of radiochemical sterilization are described, together with some of its successful applications, such as surgical sutures and tissue adhesive and the results of recent comparative studies of radiochemical and other sterilization methods for absorbable materials. Projected future trends in sterilization technology are also outlined. 

Therefore, the future trend will be to combine appropriate coating materials with surface nanostmctures to promote desired mammahan cellular functions and resist bacterial adhesion and colonization. Such a strategy can also be extended to a wide range of biomedical engineering. 

As regard the future trends of utilization of epoxy resins, high-performance coatings, followed by electrical/electronic ones and adhesives, flooring and paving applications, composites and molding products will continue to be their primary application worldwide. Further future developments of epoxy resins are related to their use as matrices of composites for dental applications and for trenchless rehabilitation of existing pipelines. 

During the production phase, and also in service with critical structures, it is essential to use nondestructive tests to assess the quality and fitness for purpose of the product. The nondestructive test will not measure strength directly but will measure a parameter which can be correlated to strength. It is, therefore, essential that a suitable nondestructive test is chosen and that its results are correctly interpreted. Typical defects found in adhesive joints are described and an indication given of their significance. The limits and likely success of current physical nondestructive tests will be described, and future trends outlined. 

In the following sections, the materials and their surface preparation prior to be bonded, the adhesives used, and the manufacture and testing of the upper to sole joints will be separately discussed. Each section will consider an overview of the current state of the art in shoe industry and future trends will be highlighted too. 

The chemical pretreatment methods mentioned are mostly used for TPOs, but in some cases can also be effective when used on polyamide (PA), polybutylene terephthalate (PBT), or other crystalline polymers, as well as some blends like poly(phenylene oxide)/polyamide (PPO/PA), are flamed. As a possible future trend, research is currently underway (plasma polymerization) attempting to combine a pretreatment for adhesion and to provide the surface conductivity on necessary on plastic parts for acceptable electrostatic application (15). 

Finally, it is highly desirable to improve the ability to calculate the properties of surfaces and interfaces involving polymers by means of fully atomistic simulations. Such simulations can, potentially, account for much finer details of the chemical structure of a surface than can be expected from simulations on a coarser scale. It is, currently, difficult to obtain quantitatively accurate surface tensions and interfacial tensions for polymers (perhaps with the exception of flexible, saturated hydrocarbon polymers) from atomistic simulations, because of the limitations on the accessible time and length scales [49-51]. It is already possible, however, to obtain very useful qualitative insights as well as predictions of relative trends for problems as complex as the strength and the molecular mechanisms of adhesion of crosslinked epoxy resins [52], Gradual improvements towards quantitative accuracy can also be anticipated in the future. 

Recent regulations and environmental legislation have put pressure to stop the use of traditional synthetic adhesives for wood panels. Higher costs of oil from which traditional adhesives are derived have also contributed to this trend. As a consequence, the interest in natural adhesives for wood panels has intensified. This has translated in the revival of the traditional approach of partially substituting in the formulations a small proportion of the synthetic adhesive with a natural material [1]. This approach is rather old and is revived now to conserve traditional synthetic adhesives that might well not be available in the future. Its main disadvantages are... 

This large market includes residential housing and commercial building, in addition to roads, bridges, and other elements of the infrastructure. The largest volume of adhesives presently used is for nonstructural applications however, the use of structural adhesives is expected to increase in the future. While some end uses will involve primary structural bonds, most will be semi-structural, in which the adhesive will be used in combination with a mechanical fastener. The use of adhesives is also expected to increase as the trend towards the manufacture of prefabricated sections continues. Laminated beams and trusses are one established use for structural adhesives, typically phenolic, but there is now interest in urethanes for this purpose. Epoxies are also widely used, mostly for the bonding and repair of concrete. 

Many trends in polymer synthesis generally are being applied, or could be applied in the future, to adhesives. There is a continuous stride toward polymers with superior heat resistance. To achieve this, various heterocyclic and aromatic structures are built into polymers, e.g., by intramolecular cyclization (polyimides, polybenzimidazoles), trimerization of terminal acetylene or nitrile groups, etc. Another route is to introduce highly stable perfluorinated units into the polymer. While heat-resistant polymers find their main applications as laminating... 

Ten years into the future may see new board products, new bonding applications, and new innovative adhesive systems. Some future challenges can be predicted based on current trends and will be met by those who currently see opportunities to meet those challenges. Some future challenges cannot be predicted. By extrapolating the individual and collective industrial ability to formulate opportunities to meet past challenges, the unpredictable future challenges will also be met with creative, effective and profitable solutions which will benefit our society. 

Finally, a few words are in order on research trends in the field, current and future ones. Colloid and surface science is not just an area of extensive applications but also an active field of research in essentially all its dimensions. Even a brief account of research trends in colloids and interfaces would require a separate book. We have nevertheless attempted to present research examples throughout the book, via case studies and problems, some of them taken from industrially-oriented applications. Several examples have been presented in the fields of paints, wetting and adhesion, surface characterization, surfactants and foams in Chapters 3,5,6 and 13. 

It is on this last point that one should probably focus both the academic research aiming to understand the adhesion phenomenon, and the applied research on optimal and reproducible performance of the adhesives. It is on this basis also that one can ask, going beyond current industry trends and developments, about the principles behind the development of future adhesives ... 

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