A laboratory chemist is always on the lookout for container materials which can be used for handling and dispensing of all types of solvents, chemicals, oils, etc. However, this dream has remained unfulfilled for ages. In the last few decades plastics have supplemented common glassware as they have provided some viable options. Deciding between glass and plastic ware discusses the benefits and drawbacks of plastic ware.
The present article covers some common plastic materials which have been used for fabrication of laboratory items.
Polyethylene or polythene is the most abundant manufactured plastic material. Polyethylene is generally available as thin transparent sheets which are used for making packings for solid test sample powders and other containers such as bottles. Other important plastic materials derived from polyethylene are HDPE and LDPE.
High-density polyethylene (HDPE)
HDPE is a rigid variant of polyethylene which has better impact resistance and shows resistance towards acids and alkalis, alcohols, hydrocarbons, ketones and oils and can withstand high temperatures up to 120 degrees C. It is commonly used for making bottles, and large containers and pipes. HDPE articles should not be autoclaved.
Low-density polyethylene (LDPE)
LDPE shows more flexibility than HDPE and is used for making wash bottles, dispensing bottles, tube caps and lab trays. It has lower heat resistance than HDPE and is used up to around 80 degree centigrade only and cannot be autoclaved. It shows resistance to dilute acids and alcohols but can be attacked by oxidizing agents, halogenated hydrocarbons, aromatics and mineral oils
Polymethylpentene (PMP or TPX)
Polymethylpentene is a favoured plastic material because of its rigidity, impact resistance and temperature resistance up to 120 degrees centigrade. It is autoclavable and finds use in making volumetric flasks, beakers, measuring cylinders and optical windows. It shows good resistance to acids, bases, alcohols, mineral oils, and aldehydes but can deform on long exposure to oxidizing agents, hydrocarbons and ketones.
Polyethylene terephthalate (PET)
PET is a clear plastic material which exhibits good resistance towards weak acids, alcohols and aliphatic hydrocarbons. It finds common use as media bottles, water bottles, dispensable pipettes and face protection shields. Autoclaving of PET items is not recommended.
Polystyrene shows good strength and rigidity alongwith excellent transparency. It can be recycled for re-use. However, its use is limited to an upper temperature of about 70 degrees centigrade. The items commonly made from it are plastic test tubes, centrifuge tubes, tube racks, serological pipettes, petri dishes and pipettes. It is compatible with aqueous solutions, weak acids and bases but is attacked by aromatic and halogenated solvents.
Polycarbonate shows good strength and is used for the manufacture of safety shields, vacuum desiccators and centrifuge tubes. It is autoclavable. However, it shows poor compatibility with acids, halogenated hydrocarbons, bases but shows appreciable resistance towards oil and organic solvents.
Polypropylene has good strength and is a translucent material. It can be used at temperatures upto135 degrees centigrade and therefore it is autoclavable.It is compatible with acids, bases, aldehydes, ketones and aliphatic hydrocarbons. It is used for making items like trays and jars which may require frequent sterilization.
PMMA plastic or acrylic
Acrylic is used commonly for making safety shields and transparent tabletops. It has low resistance towards most chemicals and has low heat resistance as well. Common items made from PMMA plastics are optical cuvettes
PTFE is a fluoropolymer which is also commonly called Teflon. It is highly inert material. In addition it has high temperature stability and non-adhesive nature. It is commonly used as magnetic stirrers, stop-cocks, valves, tube connectors, beakers and centrifuge tubes.Teflon tape is commonly used for securing leak free seals for gas connections.
Plastic ware offers several benefits over common laboratory glassware items but you should also be aware of appropriate cleaning practices that should be adopted for such reusable items.