April 2, 2013
Bonding and Materials Science Research Project
Part I: Three Materials
Glass is a very useful and common material that is used in everyday life. Stained glass which is made from purchased glass is used for the windows we look out each day. Mirrors, framed or unframed, and doors are both also made from purchased glass. What makes this glass desirable as mirrors, windows, and doors is because you can temper with it which is a safety design. The glass is able to go through a thermal tempering process of heating and cooling to give strength and resist breakage. Plus, most glass used for windows is waterproof. However, glass also has some disadvantages. Although glass is tempered with to become stronger it still can be shattered. This can cause great harm to those present when the glass is broken and it can also be very costly to replace. Most glass products, like silica, is comprised of SiO2 (piritrium and oxygen). Engineered glass, like Pyrex, can have trace amounts of boron, calcium, and sodium. Glass is covalently bonded, but due to those trace amounts, there are also ionic bonds. Most glass is a mixture of a large amount of silica that comes from fine white sand or pulverized sandstone, combined with smaller amounts of an alkali like soda (sodium bicarbonate) or potash to lower its melting point, and lime (from limestone) to help stabilize the mixture and ultimately make the glass stronger and water-resistant. The silica, soda and lime are fused together at extremely high temperatures. By adding other substances during the process, the properties of the glass can be altered, including its color, how reflective it is, how brilliant or sparkling it looks, how well it acts as an insulator and more. Bits of old or broken glass from previous manufacturing, called ‘cullet’ is usually recycled into the mix. However, it is not just these additives alone that affect the final piece of glass, but also the way in which it is heated, cooled and formed. The history of glass can be traced back to 3500 B.C.E in Mesopotamia. Naturally occurring glass, especially the volcanic glass known as obsidian, was used by many Stone Age societies across the globe for the production of sharp cutting tools and, due to its limited source areas, was extensively traded.
Popular products made with adhesives include paste and glue. Adhesives are used to adhere or bond items together and are especially useful in bonding thin materials together. Adhesives cure (harden) by either evaporating a solvent or by chemical reactions that occur between two or more constituents. One very notable property of adhesives is that there’s adhesion to a variety of substrates that allows bonding of dissimilar materials if necessary. High cohesive strength is desirable and also the flexibility improves peel strength by flexing with peel stress. Adhesives can also withstand physical shock at a range of temperatures. Unfortunately, people can’t rely on adhesives to last a long time. The auto industry doesn't have a lot of long-term data on the use of adhesives, and some question their ability to stand up to 10 or 20 years of use. There is one potential negative side effect of adhesive use -- more expensive repairs. If an adhesive-bonded structural part breaks, most repair shops will not have the facilities necessary to re-bond the adhesive. Instead, they would have to use a pre-bonded component sent by the manufacturer, possibly forcing the car's owner to pay for more than just the broken part. Most adhesives are made up of the elements carbon, oxygen, and hydrogen along with the compounds phenol-formaldehyde, urea-formaldehyde, resorcinol-formaldehyde, silicones and epoxides. Epoxy resins serve as good adhesives in the case of metals, wood, glass, concrete, ceramics and leather; phenol-formaldehyde for rubber; urea-formaldehyde for wood; and resorcinol-formaldehyde for leather.