Chemical compatibility is strongly related to package material. When choosing a container, the compatibility of the contents with the material forming the container is crucial. Hazardous materials (commonly referred to as Hazmat) bear legal responsibility for chemical compatibility. Chemical compatibility is highly dependent on the packaging, so it is essential to understand the properties of plastic materials. Popular plastic packaging materials are polyethylene and polypropylene. They have a lot of similarities offering lightweight and durable features. However, testing is necessary to ensure safe transportation and storage. Many published listings show the compatibility of common chemicals with packaging materials. Thermo Fisher Scientific provides a well-detailed compatibility chart. Before deciding a package for your products, you can conduct various tests to prove good chemical compatibility.
Package Material Chemical Compatibility Tests
You can test strips molded from the plastics used to manufacture the containers and compare critical properties such as tensile strength, elongation, and impact resistance (ASTM D638) for ‘before and after’ exposure chemicals. However, since the container design and the molding process can influence the container’s performance, a test involving the container itself is recommended. Testing with a container consists of holding the liquid in the container under conditions that duplicate or exceed the proposed storage time and severity of storage conditions (stacked height, temperature, internal pressure, etc.).
If the storage time is unacceptable, the test can be “accelerated” by raising the storage temperature. The reduction of storage time by a factor of 2.5 for 10°C increase in storage temperature is used as an approximation. For example, a proposed application involving a one-year shelf life at an average temperature of 25°C would be held for 21 weeks at 35°C or eight weeks at 45°C to obtain equivalent results. Appendix B of Part 173, Title 49, Code of Federal Regulations, specifies a procedure for hazardous material compatibility tests.
Chemical Incompatibility Examples
There are many indications of incompatibility. A few includes:
- A chemical attack is indicated by the weakening wall structure of the container. A drop test with the filled samples after the storage period will provide an approximate determination.
- Softening/Swelling is evident with the storage of permeating hydrocarbons. If the container is being used for a single-use for a short duration, this is not necessarily a problem if you ensure that the degree of softening or swelling is small.
- Permeation to the outside manifests as weight loss in the container. Unless the product is a poison, a 2% loss during testing is acceptable. If it is a poison, a rate of ½% is allowed. Naphtha, benzene, gasoline, and carbon tetrachloride are known to excessively permeate plastic containers.
- Pressure build-up can occur from the vapor pressure of liquid contents, accentuated by elevated temperature or by a reaction of permeating oxygen with liquid contents. It can exert stress at seams and other areas, making the container more susceptible to environmental stress cracking.
- Discoloration of contents can occur from the product’s reaction with permeating oxygen or by a reaction of the product with plastics. For example, concentrated sulfuric acid darkens when stored in contact with polyethylene, although it does not reduce the acid’s efficiency.
Packaging Products by ZACROS
Understand both chemical compatibility and package material are essential choosing the right packaging for your product. ZACROS AMERICA is responsible for manufacturing containers by applicable construction and physical (not chemical) performance standards, codes, and regulations. The shipper is responsible for deciding to ship (or not to ship) a given chemical in a given container. Based on the extensive history of field experience and comprehensive testing, ZACROS AMERICA aids in determining the fitness of an application. Our CUBITAINER® is capable of shipping Group II and III HAZMAT chemicals. Contact us to get more information about our products and their chemical compatibilities.