Two industry specialists answer four questions about silicones in this WALLS & ROOFS question and answer session.
Silicones enable architects to design spectacular buildings with vast expanses of uninterrupted glass walls, thanks to their superior bonding ability and durability.
Two industry specialists, Michael Berg, national sales and marketing manager at Den Braven Sealants, and Doug Richards, technical consultant for silicones and sealants at a.b.e. Construction Chemicals, give insight into this special kind of product.
1. What types of silicones are available for construction?
Type of silicone & Application/use
Acetoxy curing silicones: Glazing, high temperature requirements, aquarium buildings.
Neutral curing silicones: Weather and perimeter sealing as well as specialised glazing.
Neutral structural silicones: Structural glazing, curtain walls and double glazing.
Two-part structural silicones: Structural glazing.
Hybrid sealants: Joint sealing of roofs, floors and perimeter sealing.
Polyurethane sealants: Joint sealing around windows and floors.
Self-levelling sealants: Road sealing and building sealing where a sealant with high ultraviolet (UV) resistance and high movement capabilities is required. Also used for ease of use were tooling of the applied sealant is not required.
2. Why opt for more expensive products instead of just any silicone?
Berg: Silicones are specially designed to perform on certain substrates, for specific applications and must have proper performance specifications. Professional silicones are of a specific grade, quality and standard. When using cheap or incorrect silicones or sealants, the following problems may be incurred:
– Adhesion and/or cohesive failures.
– Discolouration and substrate attack such as the staining of natural stone, discolouring of mirror backing and the delamination of laminated glass.
– Non-compatibly with other substrates and chemicals.
Richards: It should be considered that more costly products come with a warranty and technical back-up.
3. What is your advice for specifiers or architects?
Berg: Contact the applicable manufacturers and ensure that the correct product and technology is considered with a proper specification written into the project requirement. Performance specifications are also very important to ensure longevity and durability. Specifiers must insist on industry and up-to-date, conforming technical data sheets, and material safety data sheets.
Richards: Investigate the UV capabilities of polyurethanes versus silicones. Most polyurethanes may be cheaper, but cannot withstand UV exposure and will crumble after two years of exposure. Also confirm specific applications with technical sealant and silicone manufacturers, especially chemical resistance, movement capabilities and substrate compatibility.
4. What leads to failures?
Berg: Not specifying sealants leaves the door open for inferior and incorrect products being used. This leads to failures and unnecessary costly remedial work. Sealants may crack, not bond, swell and discolour, to mention but a few. In high-rise buildings quality control and correct application of the applicable sealant are very important. Architects, engineers and specifiers should ensure that the sealants conform to international building standards and norms.
Richards: Chemical resistance, movement capabilities, substrate compatibility and UV exposure over a period of time are some of the main causes for failures.
Talk to the experts and be sure to specify the correct product. Not specifying a product, leaves the installation open to failures.
Full thanks and acknowledgement are given to a.b.e Construction Chemicals and Den Braven Sealants for their participation in this question and answer session.