Disadvantages in Using Plastic Beakers
Labs have a wide variety of applications for beakers. They are used to measure out liquids, to contain reaction mixtures, and to hold compounds while they are heated or cooled. As with other lab ware, most beakers are made of glass rather than plastic. This is partly because of historical precedent, since glass has been around a lot longer than plastic, but also because plastic has some distinct disadvantages, depending on the application.
Other People Are Reading
-
Temperature Range
-
Glass containers have a very wide temperature range which they can tolerate without melting, breaking or shattering. Most plastic beakers, however, do not have such an extreme tolerance for temperature. A plastic beaker made of high density polyethylene (HDPE), for example, melts at 125 degrees Celsius, just a bit higher than the boiling point of water. This material, therefore, could not tolerate the much higher heat of a direct flame as a glass beaker could. HDPE also becomes stiff and brittle at -25 degrees Celsius, and so could easily fracture at low temperatures.
Attack by Solvents
-
Glass lab ware will withstand many chemicals and almost all common solvents without damage or reaction. Some plastics, such as Teflon, have similar chemical resistance. However, many plastic beakers are quickly dissolved or degraded by a variety of chemicals, thus limiting their usefulness. HDPE is attacked by several classes of chemical solvents including aromatic ketones and hydrocarbons. Other plastics, such as polymethylmethacrylate are degraded by acids as well as alcohols and esters. A notable exception to this rule is hydrofluoric acid, which will react vigorously with some types of glass, and for which plastic is a good choice.
-
Sterilization
-
Plastic beakers do not always tolerate sterilization as well as glass, because the extreme conditions required to kill microbes can degrade the polymers they are made of. Many plastic beakers can still be sterilized, but they may not be usable afterwards. There are a number of plastics, for example, which cannot be sterilized by the common method of autoclaving. These include polyvinyl chloride, acrylic and both low density and high density polyethylene.
Other Issues
-
Plastics also have some other issues which are not encountered with glassware. They sometimes allow the transmission of water vapor or gases (such as oxygen or carbon dioxide) through the walls of the beaker. In some rare applications, this could cause undesirable reactions with the chemical in the beaker. Some plastics could also absorb chemicals from a sample, or leach chemicals into a sample, which can upset the results of an experiment.
-
References
Resources
- Photo Credit PhotoObjects.net/PhotoObjects.net/Getty Images
