Brief history

Sealants were used in stone-age cultures to water-proof dwellings - archeology records show that bitumen was used as early as 36,000 years ago. Naturally occuring bitumen bound the walls of the ancient cities of both Jericho and Babylon. It was also used as a sealant in the construction of brick baths in India as early as 3000 B.C [1].

In more modern times, sealants (then commonly known as "joint-fillers") have been used since the early 1900's, when heated tar was applied to seal joints between concrete slabs. In the 1970s, the expectations of joint fillers changed, and products were expected to minimize water infiltration as well. At this time, the word "sealant" became more common, and in essence, defined the switch in expectations [2].

Two other noteworthy dates in this brief history include: 1922/23 silica gel was first sold, and, around the same time, lead solder was being phased out as a sealant in 'tin can' joints. In 1941 a synthetic sealant was developed to replace natural rubber bottle and can sealants - due to a shortage of natural rubber.

What is a sealant:

Sealants are composed of two main types: silicone and polyurathanes. The silicone sealants that are available at the hardware store may be comprised of the following. Methyltriacetoxysilane 2%, Ethyltriacetoxysilane 2%, Silica or Silicon Dioxide 8-9%, and Polydimethysiloxane 85%. Polydimethylsiloxane is the world’s most common silicone. Its applications range from contact lenses and medical devices to elastomers, caulking (sealing), lubricating oils and heat resistant tiles. Silicone sealant's physical appearance can be described as: clear paste with a consistency like toothpaste and with an acetic-acid like odor.

Polyurathanes are composed of long molecular chains - longer than the molecules of silicones. These longer, more complex chains mesh within each other more intricately, and this gives them greater bonds within the sealant and to other materials. As a result, they generally have greater shear strength than silicone sealants and are less likely to break along a glue line. The polyurethane sealants that are available at the hardware store may be comprised of the following. Polyurethane polymer (30 to 60%) Plasticiser (10 to 30%) Filler (10 to 30%) Pigment (<10%) Xylene (<10 %). Its physical properties can be described as: thixotropic, non slump, coloured paste with a slight aromatic odour.

Care must be taken when using sealants - refer to the Material Safety Data Sheet for each product. Typical hazards include: Irritation to the nose and throat caused by the vapor evolved during curing. Eye contact may cause intense irritation and injury. Contact with the skin may cause skin irritation.

The following hyperlinks provide great resources for teachers and students.

The following sealant websites links have very useful information along with links to other sealants & adhesives sites.

GE Silicones has 3,500 employees at plants around the world, and manufactures more than 4,000 products.

Bostik Findley Inc have lots of information and datasheets online. (Adobe Reader is required to read the .pdf files). Bostik Findley Inc has approx. 4,500 employees with production facilities and sales operations in 36 countries across six continents - making it one of the largest adhesive and sealant company’s in the world.

Orica is a publicly owned Australian chemical company employing around 8,000 staff across approximately 35 countries. One of Orica's business areas, its 'consumer products', includes the following well-known Australian brands. Dulux paints, Cabots wood treatments (preservatives and appearance improvers), and Selleys adhesives, sealants and paint preparation products. (Orica's web site: www.orica.com.au)

The following links, then, represent some of the best information that is available online!

Return >> to Adhesives

Glossary

adhesive: a substance that unites or bonds.

sealant: a substance used to seal a surface to prevent passage of a liquid or gas.

thixotropic: some gels become fluid when stirred or shaken and return to a semisolid state upon standing.

Citations

[1]. Oklahoma Geological Survey. (undated). Earth Sciences Week : History of Petroleum Development. [WWW Document] URL: www.ou.edu/special/ogs-pttc/earthsci/histpetr.htm (visited October 2002).

[2]. Public Works Magazine: Online Edition. (2000). "An Overview of Joint Sealants for Concrete Pavements" by Voigt, J. [WWW Document] URL: www.pwmag.com/articles/online_articles/joint.htm (visited October 2002).

Note: This page is under construction, and will be added to as time permits.

Copyright D. L. Christiansen [Last updated Nov 2002] Images: respective copyright owners noted/cited.