How to Select and Use Plastics Successfully in the Lab

How to Select and Use Plastics Successfully in the Lab

Working in a laboratory presents a number of health and safety obstacles, especially when working with chemicals and solutions. On one hand, to cope with aggressive chemicals, many researchers use glass either borosilicate or Pyrex labware because of its resistance to most chemicals and solutions. On the other hand, the fragile nature of glass introduces a safety hazard that researchers must take into account. Plastic labware provides a safe alternative to glass and, when chosen and used properly, it can provide years of reliable performance.

It’s important to understand that plastic labware comes in a vast array of shapes and sizes, but also in various plastic resins. Each plastic resin has its own chemical and physical properties, and these affect what you can and cannot do with the labware— whether you can autoclave it, what chemicals you can use, and if it will retain its protective elastic properties during freezer storage. When selecting plastic labware, you first need to identify a material that is compatible with the chemicals or solutions it will come into contact with in your laboratory. The second point is to check the plastic’s physical properties. In particular, you need to be sure it can handle the temperatures you will be working with.

After you have selected the best labware for your needs, you will need to care for it appropriately and inspect it regularly to achieve the best possible performance. Follow these guidelines to choose the right plastic labware for your lab applications.

Chemical compatibility of labware

First, you need to think about what kinds of chemicals your plastic labware will come in contact with. Chemicals can affect the strength, flexibility, surface appearance, color, dimensions and weight of plastics. Chemical compatibility depends on what plastic resin the labware is made from and how well that resin resists reacting with the chemical.

For example, polyethylene terephthalate (PET) has good resistance to aliphatic alcohols, aldehydes, aliphatic hydrocarbons and dilute acids. But PET labware is not recommended for use with bases, aromatic or halogenated hydrocarbons, aromatic ketones or concentrated acids; these chemicals can cause immediate damage to the labware.

In contrast, labware made from a fluoropolymer resin like perfluoroalkoxy (PFA) demonstrates excellent resistance to all common laboratory chemicals including halogenated hydrocarbons, aromatic ketones, acids of all strengths, bases, aliphatic alcohols, aldehydes and even strong oxidizing agents.

Temperature, duration of chemical contact and applied stresses like vacuum, pressure or g-forces of centrifugation also play a critical role in chemical resistance ratings for plastics. For example one can successfully put ethanol in a polycarbonate bottle for long term storage. However, if you put ethanol in a polycarbonate centrifuge tube and spin it at 5,000xg, the tube will start to crack during the first spin. It’s important to check the appropriate chemical compatibility rating charts to determine which materials will be compatible under your specific lab application.

Tool-providers have created different charts for general lab use, centrifugation, filtration and tubing applications.

Temperature resistance

The second area to investigate is the plastic’s physical properties—you need to be sure the labware can handle intended temperatures. Some plastic labware can stand up to hot-water baths and autoclaving, but not all plastics are compatible with temperature extremes. For example, polypropylene (PP) can be autoclaved, but if you attempt to autoclave polyethylene (PET) , you’ll end up with a puddle of plastic.

You should consider temperatures at the opposite end of the thermometer, as well, particularly if you plan to use the labware for freezing of samples or solutions. Some plastics retain their protective elastic and impact resistant properties at low temperatures while others become very brittle and will likely crack if they receive an impact. It is the plastic’s brittleness temperature that needs to be considered. Polycarbonate (PC), low-density polyethylene (LDPE) and high-density polyethylene (HDPE) are all good choices for freezer storage as they all have brittleness temperatures below -100oC. Other plastics can be used at freezing temperatures, but care must be taken to protect them from impact to prevent breakage.

Selection tools

Tools are available to help you select the plastic labware that’s best suited to your needs, based on chemical resistance, temperature exposure and other variables. Global Scientific offers on each product page a specification section which lists all the relevant properties of tat particular product i.e. compatibility with specific types of chemicals, within a defined temperature range and time period. resin, volume, shape and size,  product certifications (e.g., sterile, low-particulate). See our shop for more on our products specifications.

Care and maintenance

After you’ve chosen your labware, you’ll need to care for it to assure its longevity. Be sure to wash pieces thoroughly after use. When washing, be sure to use a pH-balanced detergent see our cleaning range. Store items where they will be protected from UV light -sunlight and fluorescent lighting; Prolonged exposure to UV radiation ages plastic, and exposure to non compatible chemicals can cause brittleness, stress cracking, loss of strength, discoloration, deformation, dissolution or permeation loss.

Autoclaving LABWARE directions—including trace cleaning, general cleaning and removing RNase or DNase from plastic ware—are available with our range of autoclaves.

Signs of aging

Before each use, inspect your plastic labware for signs of aging, including:

§  Discoloration not removed by washing— yellow, brown, orange or pink.

§  Brittleness—loss of flexibility.

§  Crazing—spider web cracks.

§  Stress cracking—vertical cracks or those around bends or flex points.

§  Pitting and other permanent surface blemishes.

To avoid labware failure during use, promptly replace product pieces when they begin to show any signs of aging. Aged plastic eventually becomes brittle, losing its protective elastic properties, and it is more likely to break. And be aware that repeated autoclaving will shorten the life of your labware.

Getting the most value from your plastic labware starts with choosing a high-quality supplier, followed by determining the chemical and thermal properties you require. Careful selection, teamed with proper care and maintenance, will assure many years of service from your labware.