21st Century Potential for Positive Change – Contributions by Sealants and Adhesives
What do the previous comments have to do with a book focused on the durability of building and construction sealants and adhesives?
Sealants and adhesives are at the interface between building materials and/or components and provide important functions, such as sealing, bonding, strengthening, movement accommodation, shock protection, fire retention, thermal or electrical insulation, and many others. These functions provide added value to the building and can enable a reduction in the building’s ecological footprint. Below are just a few examples of the contributions that sealants and adhesives can make to the reduction of operational energy associated with a building:
• Energy-efficient ventilation achieved via controlled air and moisture flows (elimination of both ‘infiltration’ and ‘exfiltration’, the unintentional and uncontrollable flow of air through cracks and leaks in the building envelope).
• Improved thermal insulation of windows achieved by replacement of existing glazing by durable, sealed high performance insulating glass units.
• Renewable energy generation: Use of sealants and adhesives in the assembly and sealing of photovoltaic (PV) solar modules as well as during installation of building integrated photovoltaic solar panels (BIPV) in the building envelope.
The use of a structural sealant or adhesive may also allow redesign of a building component such that the dematerialization results in a reduction of the associated embodied energy of the component.
One example is the elimination of steel reinforcement bars in uPVC windows by bonding the glass panes to the uPVC frame as an alternative reinforcement measure. Experience gained with silicones in structural glazing and protective glazing systems and with polyurethanes in automotive direct glazing led to the development of these structurally bonded window systems. Obviously, the strength of the window then depends on the structural strength of the glass unit. However, glass has a good load bearing capability (stiffness) and can contribute considerably to the overall strength of the system. In addition to their environmental benefit (smaller carbon footprint), these constructions also offer functional benefits, such as leaner and more slender frame designs (the larger vision area results in increased light transmission via the window opening and provides improved natural lighting) as well as improved protective glazing properties (resistance to burglars, bomb blasts, hurricanes, earthquakes, avalanches, etc.). In this example, dematerialization is achieved by satisfying several product functions through one component (sealant) of the overall product (window).
A second example is the replacement of concrete beams by hybrid composite beams. These composite beams are one-tenth the weight of concrete, one – third the weight of steel, yet they are strong enough to replace structural concrete beams. Manufactured by filling fiberglass composite boxes with a concrete and steel arch, covered by composite tops secured using a two-part methacrylate adhesive, they show excellent environmental durability and are expected to have a useful life of at least 100 years, during which they need less maintenance than existing materials. Furthermore, due to their resilient, energy absorbing, construction, they provide seismic shock resist – ance. The ‘dematerialized’ components mentioned here in the two examples can lower the carbon footprint of construction projects due to the reduction in their materials’ embodied energy, and the lower fuel usage needed to ship these lighter weight components.