There are nine main types of funnels used in laboratories, each with a distinct function. The materials used in the construction of a lab funnel depend on the task they are expected to perform. Funnels in a laboratory are required for tasks such as adding small doses to a solution, filtering solids from liquids, dispensing powders and separating components of a liquid mixture. Funnels that are expected to withstand high temperatures and funnels used for corrosive materials, liquids or fine powders all need to be constructed out of material suited to the task.
The two most common materials for lab funnels are polypropylene (PP) plastic and borosilicate glass. The Büchner and Hirsch vacuum filtration funnels are both traditionally made out of porcelain though also come in a PP or glass model.
Borosilicate glass is a favourite construction material for many classes of funnels. For all laboratory work that requires a transparent vessel the Borosilicate glass is preferred. The clear glass is also better for seeing gradation marks during any process.
As an inert substance Borosilicate glass makes an ideal lab funnel for processes that use hot or corrosive materials. It also has a low thermal expansion resulting in very high structural integrity and is easily affordable for most budgets.
The inert and hardy properties of Borosilicate glass make it the best material for dropping or addition funnels and separating funnels. It is also used extensively in the construction of powder and Büchner funnels.
Another highly suitable material for lab funnel construction is PP which can be moulded into any shape and used to produce multiple sizes and designs of hard, durable funnel. PP is a linear hydrocarbon polymer, similar to polyethylene. It is a widely versatile polymer and can be used as both as a plastic and a fibre. PP funnels are easy to clean, maintain and store.
In a laboratory setting, PP is very popular for powder funnels which are used to pour fine particles. PP funnels also used extensively for use with organic solutions and many aqueous solutions that are not of a corrosive nature. Most PP funnels are suitable for all substances except hydrocarbons and ketones. Depending on the model, PP funnels will withstand temperatures from a low of -40C up to 135C.
Polye can replace ceramic in the construction of the Büchner funnel and is a popular glass substitute in many applications of lab funnels.
Büchner and Hirsch funnels are both traditionally constructed out of porcelain. Porcelain’s high chemical resistance makes it ideal for the process of vacuum filtration. It is easy to clean after use and will last many years. Porcelain can also withstand extreme temperatures and is the industry standard for these types of funnels. The best material for good quality laboratory funnels, as you can see, is entirely dependent on its function. In some cases, the choice is down to your own personal preference but for most funnels, the process it is required to withstand will determine the best material.