For anyone working in pharma, product integrity is an ongoing challenge – one that requires careful consideration around packaging to make sure that active ingredients in the formulation are kept safe and secure across the supply chain.
In this blog, the team at CJK discuss solvent resistance, regulatory requirements and accessing packaging that enables long-term stability and compliance.
What is solvent resistance in packaging?
Solvent resistance is the ability of a material to maintain its physical integrity and chemical stability when exposed to solvents, oils or other aggressive substances. In pharmaceutical applications, this means the container won’t dissolve, swell, crack or degrade when it comes into contact with the drug product.
Many liquid medications rely on solvents such as ethanol or propylene glycol to stabilise the active pharmaceutical ingredient. If the packaging material lacks sufficient solvent resistance, these substances can interact with and weaken the container. The result can be compromised mechanical strength, leaks or even the migration of unwanted chemicals into the medication.
Why solvent resistance is a critical property in industrial applications like packaging
Packaging with solvent resistance directly impacts both product safety and packaging performance. When a material lacks sufficient resistance, solvents can extract compounds from the plastic – a process known as leaching. These leachables may alter the drug’s composition, potentially reducing efficacy or introducing harmful contaminants.
Beyond chemical compatibility, solvent resistance also affects structural integrity. Prolonged exposure to aggressive substances can trigger environmental stress cracking, weakening the material over time. The result: leaks, product loss and increased risk of recalls… alongside avoidable operational and financial strain. Solvent resistant bottles
Common materials and their chemical resistance profiles
Choosing the right material ensures the longevity of your product, no matter the rigours involved in transport. Different materials offer varying levels of resistance based on their molecular structure:
High-Density Polyethylene (HDPE) and Polypropylene (PP)
HDPE and PP provide good resistance to water-based solutions and alcohols. However, they can show low resistance when exposed to certain non-polar solvents or oils. In these cases, the material may undergo swelling, which makes the plastic lose its structural integrity.
Fluoropolymers (PTFE/Viton)
For aggressive substances, materials like PTFE (Teflon) exhibit high solvent resistance. In industrial applications, Fluorocarbon rubber is often used because it withstands exposure to fuels and lubricants without degradation.
The commercial impact of solvent damage
Plastic remains a highly effective and reliable packaging material in pharmaceutical and industrial applications. Its versatility, durability and manufacturability make it the right choice for many products. But like any packaging material, performance depends on selecting the right resin for the formulation and storage conditions.
When chemical compatibility is overlooked, solvent exposure can affect packaging performance in ways that create operational and commercial risk.
Swelling and permeation: some solvents can penetrate the polymer matrix, causing the material to expand or change over time. This may affect dimensional stability and increase permeability, which can reduce shelf life or compromise product protection.
Crazing: exposure to incompatible chemicals can create fine surface cracks, known as crazing. Even when a container appears intact, these defects can weaken the material and raise the risk of failure during handling, shipping or long-term storage.
Softening: certain chemicals can reduce a plastic’s rigidity, especially under elevated temperatures. This can lead to distortion, reduced performance and avoidable complications across storage and distribution.
The extent of these effects depends on several factors, including the type of solvent, its concentration, the storage temperature and how long the material remains in contact with the formulation. More aggressive solvents, higher concentrations and elevated temperatures can all accelerate chemical interaction and increase the likelihood of swelling, softening, cracking or permeability changes. Exposure over time can also amplify issues that may not be visible in the early stages of a product’s lifecycle.
How solvent resistance is measured and tested
Solvent resistance is tested to make sure packaging will hold up when it comes into contact with a drug product, cleaning agent or other chemical exposure. The aim is to confirm that the package can continue doing its job: protecting the product, preserving quality and keeping important information intact.
Immersion testing
One common method is immersion testing, where packaging materials are exposed to specific liquids for a set period of time. Afterward, the material is checked for visible or performance-related changes, such as swelling, softening, cracking or loss of strength.
This helps manufacturers understand whether a container can safely hold the formulation without breaking down over time. If the packaging performs well, it supports product stability, reduces the risk of leaks and helps ensure the product reaches the end user in the condition intended.
Rub testing
Rub testing is used for printed surfaces, labels and coatings. The package is rubbed with a cloth containing a cleaning solution or solvent to see whether printed information smears, fades or rubs off.
These standards help confirm that the packaging is fit for purpose before it reaches the market. In other words, they help establish that the material can protect the product under real-world conditions. If you are looking for solvent resistant bottles, contact the team at CJK – in many cases we will have access to test data for our solvent resistant products.
The role of adhesives and sealants
Adhesives and sealants also play an important role in packaging performance. They help labels stay in place, closures stay secure and package components remain properly sealed.
If these materials are not resistant enough, labels may peel, seals may weaken and package integrity can be lost. When they perform well, they help the packaging stay intact through filling, handling, transport and storage.
That means better protection for the product and fewer issues across the supply chain.
Factors influencing material durability
How a package performs over time will depend on practical factors including chemical properties, its concentration of liquid contained, storage conditions and duration of exposure. In pharmaceutical applications, these details all have influence, because even small compatibility issues or sub-optimal storage conditions can affect package performance, shelf life and product quality.
That is why choosing the right packaging is so important. CJK offers pharmaceutical packaging solutions designed to meet the demands of real-world storage, transport and use. By selecting the right bottle for the application, manufacturers can improve product protection, support long-term stability and move through the supply chain with greater confidence. Get in touch with our team to find out more.