Choosing a laboratory container for a solvent or formalin requires checking more than just the vessel’s capacity and shape. The type of plastic, the substance concentration, the temperature, and the expected contact time all matter. A poorly matched material may swell, soften, crack, or lose its seal over time. That is why, before making a purchase, it is worth comparing the properties of PP, HDPE, and PET and relating them to the specific reagent.
How PP, HDPE, and PET differ in laboratory containers
Polypropylene (PP), high-density polyethylene (HDPE), and polyethylene terephthalate (PET) differ in, among other things:
· rigidity,
· transparency,
· chemical resistance,
· behavior at elevated temperatures.
Therefore, when choosing between them for laboratory containers, you should take into account the properties of the stored substance, its concentration, and the conditions of use.
| Property | PP (Polypropylene) | HDPE (High-Density Polyethylene) | PET (Polyethylene Terephthalate) |
| Rigidity | Rigid and lightweight | Slightly flexible, impact-resistant | Very rigid |
| Transparency | Semi-transparent or typically opaque | Usually semi-transparent | High |
| Chemical resistance | Very good resistance to many acids, bases, alcohols, and reagents | Very good resistance to many acids, bases, and alcohols | Good for aqueous solutions, but limited resistance to aggressive substances |
| Heat resistance | Very good | Good | Lower than PP |
| Solvent compatibility | Depends on the type of substance | Good resistance to many aliphatic solvents | Limited resistance to many aggressive solvents |
Chemical properties and resistance to solvents and formalin
PP shows very good resistance to:
· acids,
· bases,
· alcohols,
· aldehydes and many inorganic reagents.
It also performs well with formaldehyde and formalin, especially at room temperature. An additional advantage of this material is its resistance to elevated temperatures, which means that selected PP laboratory containers may be suitable for autoclave sterilization.
HDPE is also characterized by high chemical resistance. It is used, among other things, for acids, bases, alcohols, aqueous solutions, and formalin. In the case of formalin, however, the compatibility of HDPE and PP depends on the specific concentration and temperature, so before use you should check the manufacturer’s data for the particular container.
PET is rigid and transparent, which makes it easier to monitor the liquid level, its color, and the presence of sediment. However, its chemical resistance is more limited. The material performs well with many aqueous solutions and selected alcohols, but it may be unsuitable for:
· ketones,
· esters,
· ethers and aromatic compounds,
· chlorinated hydrocarbons.
Which plastic is best for storing solvents?
In the case of organic solvents, the choice is most often narrowed down to HDPE and PP, but that does not mean that either of these materials is suitable for every substance. HDPE performs well with many aliphatic solvents, alcohols, and selected nonpolar liquids. PP may be suitable for alcohols and some reagents, including applications that require elevated temperatures.
Greater caution is needed with aromatic and chlorinated solvents. In such cases, HDPE and PP may have limited compatibility, so long-term storage should take place only in a container specified by the manufacturer for the particular substance. Depending on the application, glass or fluoropolymers such as PTFE, PFA, or FEP may be an alternative.
PET is usually not the first choice for storing aggressive organic solvents. It may be suitable for certain substances if this is confirmed by a chemical resistance chart, but high transparency alone is not a sufficient reason to use it.
Before choosing a container, you should check:
· the chemical name of the substance and its concentration,
· the storage temperature,
· the expected contact time,
· the resistance of the body, cap, and seal,
· the sealing requirements,
· the manufacturer’s recommendations for the specific model.
Examples of PP, HDPE, and PET container applications in the laboratory
PP is used for storing:
· reagents,
· samples,
· acids,
· bases.
It is also used to manufacture test tubes, vials, and vessels where resistance to elevated temperatures or the possibility of sterilization is important.
HDPE is used to manufacture containers for:
· acids,
· bases,
· alcohols,
· buffers,
· aqueous solutions,
· detergents,
· formalin.
Thanks to its impact resistance, this material is also suitable for transporting laboratory liquids.
PET is chosen primarily for manufacturing vessels intended for:
· aqueous solutions,
· buffers,
· media,
· sera,
· samples whose contents should be easy to observe.
Before using it with an organic reagent, its chemical compatibility should be checked.
How to choose the right container for formalin and other aggressive substances?
Containers made of HDPE or PP are most commonly used for formalin. They should have a properly selected cap and sealing system, because the properties of the body alone do not determine the tightness of the entire set. With higher formalin concentrations, compatibility should be checked for the specific concentration value and temperature.
When choosing a container, it is worth going through several steps.
· Determine the substance, its concentration, and the storage temperature.
· Check the plastic’s resistance to the specific chemical compound.
· Verify the compatibility of the cap and seal.
· Establish whether the liquid will be stored briefly or for many months.
· Take into account transport requirements and leak protection.
· For aggressive substances, confirm the choice based on the manufacturer’s data.
For acids and bases, PP and HDPE often provide adequate resistance, while PET requires more careful verification. For ketones, aromatic solvents, and chlorinated solvents, limitations may apply to any of the polymers discussed.
It is worth remembering that plastic resistance is not a universal property. The same container may perform well with one reagent, yet lose its properties with another under the influence of time, temperature, or concentration. Therefore, when choosing laboratory containers offered by Noex Labware, you should use chemical compatibility charts and the specifications of the specific product.
Comparison of polymers used in the production of laboratory vessels
· HDPE and PP are usually a more suitable choice than PET for formalin and many laboratory reagents.
· PP stands out for its high chemical and temperature resistance, while HDPE performs well with many acids, bases, alcohols, and solutions.
· PET is particularly useful where transparency is important, but it has greater limitations with aggressive solvents.
· The final choice must always be confirmed for the specific substance, its concentration, temperature, and contact time.
FAQ
Are PET containers suitable for storing solvents?
PET containers are not recommended for storing organic solvents because they may degrade. HDPE or PP containers are a better choice, as they offer greater chemical resistance.
Which plastic is safest for formalin?
For storing formalin, it is best to choose containers made of HDPE or PP. Both materials are resistant to formaldehyde, but compatibility should be confirmed for the specific concentration and temperature.
How can you tell whether a container is suitable for aggressive substances?
Information on chemical resistance can be found in the product specification. It is worth choosing containers whose compatibility has been confirmed for the specific substance, its concentration, and the storage conditions.
Do PP and HDPE differ in terms of solvent resistance?
Both materials have high chemical resistance, but HDPE performs well with many aliphatic solvents, while PP has broad resistance, including to acids, bases, and alcohols. For a specific solvent, you should always check the manufacturer’s compatibility chart.