Compatibility of your chemical formula and your container material is a significant consideration in the liquid packaging and bottle filling process. Selecting the right plastic or metal that will retain its shape and performance is a safety imperative. A plastic or metal container that leaks and deforms can cause damage and injury. How a container stands up to chemicals over time is also an important consideration. A liquid container can be on the shelf for years and even decades. In this article, we aim to provide some answers and recommendations to the common questions related to the ability of a container to resist the effects of different chemicals. These recommendations are based on a survey of available information from material suppliers, our own experience, and published information we believe to be accurate. It needs to be noted that external variable factors can affect the inherent resistance of metals and plastic containers such as the concentration of the chemicals, material, temperature, time exposure, and other environmental factors. The information presented in this article should be considered as a guide rather than a guarantee. Two main materials; metal, and plastic containers are used when packaging chemicals and will be reviewed separately.
Compared to metal cans, plastic containers are a more recent form of packaging for chemicals, foods, and other substances. An early innovator of plastic packaging was Tupperware which started to be used in the mid-1940’s. Other innovations such as the Ziploc bag were introduced in the 1950’s. Today plastic packaging and containers are ubiquitous and are more common than metal cans as a container for chemicals. Over the years, different types of plastic resins have been introduced in packaging. Each type has different performance characteristics and chemical resistance properties. Many environmental factors will affect the chemical resistance of a kind of plastic product. It is essential to conduct stability tests or consult with a specialist to ensure material compatibility. Three main plastic resins are used in the manufacture of chemical bottles. They are:
LDPE – low-density polyethylene
HDPE – high-density polyethylene
Polyethylene Terephthalate (PET, PETG, PETE)
Each type of plastic resin and its compatibility is covered in more detail below:
Polyethylene was invented in 1936 and is the most common plastic used today in bottles and plastic bags. There are several variants of PE available with HDPE and LDPE being the more commonly used in packaging applications. HDPE is more rigid than LDPE and has good impact strength and cracking resistance. LDPE is more flexible than HDPE and higher impact strength. Both have chemical resistance to a range of chemicals.
HDPE and LDPE containers are particularly resistant to the following chemicals:
Alcohol, Ethanol, Isopropyl Alcohol
HDPE and LDPE containers are not recommended with the following chemicals:
First synthesized in 1951, Polypropylene (PP) is another popular plastic material used in packaging. Yearly demand for PP is estimated to be around 55 million tons per year. PP is a popular material used to manufacture liquid containers and is resistant to many cleaning chemicals and first aid liquids. PP is inexpensive and widely available.
Specifically, PP containers are compatible with the following chemicals:
Bases / Alkali
PP containers are not recommended to be used with the following chemicals:
Polyethylene Terephthalate (PET)
Invented in the 1940’s as a fabric, Polyethylene Terephthalate (PET) is a type of polyester that is today molded into plastic bottles and containers for packaging applications for many kinds of products. PET bottles are used for packaging water, juices, soda, cooking oil, soaps, shampoos, and many other items. PET is a widely used type of bottle and is easily recyclable. You can recognize a PET bottle by the #1 molded on the bottom of the container. PET comes in a few varieties such as PETG and PETE. PETG is the same as PET with the addition of glycol which helps keep the plastic clear and robust after heating the plastic.
PETG containers are particularly compatible with the following liquids:
PETG containers are not recommended for use with the following chemicals:
Bases / Alkali
The food, beverage, and cosmetic industries are the primary users of metal as a packaging material. Cans have been used for around 200 years to package foods to preserve freshness and give it a long shelf life. Metal cans are highly recyclable and have a surprisingly good environmental profile. The Can Manufacturers association industry group estimates that over 1,500 food items are packaged in metal. Metal packaging materials have evolved from using lead in the metal to using steel ferrous metals and non-ferrous aluminum material. Cans are often lined with a polymer resin material to enable additional preserving attributes. For industrial goods, metal cans are used for paints, solvents, fuels, and a variety of chemicals. The home hardware segment is also a big user of metal cans to package chemicals. Aluminum and stainless-steel metal containers hold up well against any water-soluble liquid. The addition of a resin inner lining is particularly useful with water-based materials to inhibit potential corrosion of steel cans. A benefit of cans is that they will not deform when subjected to the high heat of a fire.
Generally, stainless steel metal containers are compatible with the following chemicals:
Alcohols: Amyl, Butyl, Ethyl, Methyl, Propyl
Petroleum-based fuel oils: Diesel, Gasoline, Kerosene, jet fuel
Organic oils: Corn, Cottonseed, Olive, Peanut, soybean
Juices: Grape, Tomato, vegetable
Sodium derivatives: Aluminate, Bicarbonate, Carbonate, Peroxide, Silicate
Stainless steel metal containers do not hold up well with the following: substances:
Aluminum derivatives: Aluminum Chloride, Aluminum Flouride, Aluminum Potassium Sulfate, Aluminum Biflouride
Sodium Derivatives: Sodium Bisulfate, Sodium Flouride, Sodium Hypochlorite
Aluminum metal Containers are compatible with the following chemicals:
Petroleum-based fuel oils: Diesel, Gasoline, Kerosene, jet fuel, naphtha
Organic oils: Corn, Cottonseed, Olive, Peanut, Soybean
Metal Plating solutions
Below are some of the substances not recommended for use with Aluminum metal containers:
When choosing the type of material to package chemicals, make sure to understand the properties of each element. Another recommended practice is to conduct stability testing to make sure your container will stand up over time on the shelf. Doing this will make the package will look good on the shelf and ensure safety to the consumer.