Should Pharmaceutical Manufacturers Use Steel or Plastic?

April 13, 2020 | Custom Wire Baskets, Steel Wire Products, Medical/Pharmaceutical

This stainless steel test tube/bottle rack is built to last while protecting the delicate parts within.Between meeting large production quotas, strict production tolerances, and upholding stringent sanitation standards, pharmaceutical manufacturing companies have their work cut out for them.

To overcome these challenges requires care, precision, and the right tools. One such tool for ensuring the safe and efficient production of pharmaceutical goods would be the baskets used to carry medicine containers, test tubes, and other parts through the various filling, cleaning, and sanitation processes.

The design and materials of these custom baskets and racks are critical for helping to ensure efficiency and productivity. If a test tube rack is made of weak materials, then it will degrade during the washing/sanitizing process. This increases risk of damaging the test tubes or bottles they hold, and reducing production throughput. However, it’s also important for these racks/baskets to be easy to handle and cost effective.

When it comes to manufacturing pharmaceuticals, companies in the industry frequently choose steel or plastic baskets, trays, and racks to hold their products. But, which is better: medical grade stainless steel or plastic?

Here’s a quick comparison of plastic vs steel for pharmaceutical manufacturing baskets and trays:

Plastic Vs Steel for Pharmaceutical Manufacturing          

Comparing Strength                              

In a lot of cases, the tensile strength of the material isn’t the most important factor for a pharmaceutical use basket or rack. The load weight for many of these use cases is fairly light. However, there are times where the strength of the material is still important.

For example, some applications may involve heavier loads, such as when processing multiple industrial-sized bottles through a filling process. Or, baskets may be subjected to repeated impacts because of the design of the conveyor system used to move them.

In terms of raw tensile strength and impact resistance, medical grade stainless steel alloys consistently outperform plastic polymers in the vast majority of use conditions.

Chemical Resistance

Liquid PH Measuring Device

Making the determination between plastic and steel based on chemical resistance is a bit more complicated than choosing between the two for tensile strength.

There are a lot of different polymers on the market, each with resistances to different chemicals. The same goes for steel alloys. Stainless steel alloys come in hundreds of different grades, each one resistant to different corrosive factors.

Chemicals and processes that will quickly degrade one steel alloy might not affect another. The same goes for polymers.

However, one notable thing is that if a polymer would be resistant to a chemical that would degrade steel, you can often use the polymer as a coating for the steel to protect the steel while still benefiting from its tensile strength.

Temperature Tolerances

Many sanitization processes use extreme temperatures to clean glass test tubes and bottles. The combination of high temperatures and strong chemicals is often necessary to ensure the elimination of dangerous microbes.

However, as tough as these sanitation processes are on germs, they’re also tough on the baskets and trays used to carry test tubes and bottles.

The problem with most plastic polymers is that at temperatures past 300°F (~148.9°C), most polymers will be beyond their maximum safe use temperature. This will cause rapid degradation—allowing plastic baskets to lose their shape.

With most steel alloys, the temperatures used in a standard sanitation process will almost never reach the operational limit of the steel. It’s far more common for the chemicals used in the process to be an issue than for the steel to melt or lose strength because of the temperature.

Handling of Parts                           

When handling mechanically brittle parts (such as glass tubes/bottles) that easily scratch or shatter from an impact, it’s important to minimize the risk of such impacts.

Here, polymers typically have the edge over harder materials like steel. Many polymers can have a softer surface that cushions an impact rather than redirecting force back into the object. This reduces the risk of cracking, scratching, or shattering of delicate parts.

However, there are ways to minimize impact risks, such as carefully designing the basket to hold parts tightly so they cannot move around, or redesigning processes to avoid shaking loaded baskets.

Finally, steel baskets can always be given a coating of softer polymers to act as a cushion for held parts.

Cost of Ownership Over Time

The cost of equipment over time is a critical issue to consider when choosing plastic or steel racks for your manufacturing process.

The total cost of ownership (TCO) of any equipment should be a major factor in the purchase decision—which a very different thing from the upfront cost of that equipment. This TCO should be balanced against the reward or value that the equipment will produce during its useful life.

If you look at the upfront costs, a rack or basket made of cheap plastic is less costly per unit than a comparable basket made of steel or stainless steel wires. The issue is that a stainless steel basket will typically have a much longer useful life than a plastic basket—often lasting several times longer.

For example, say a company were looking for a series of small test tube racks for their parts sanitation process and to hold the tubes through their filling process. Ordering a set of plastic racks would cost the company about $3,000 for tooling, materials, and delivery. Meanwhile, a set of steel wire racks would cost about $10,000 for a high-grade, chemically-resistant alloy.

The thing is, while the upfront cost of the plastic racks would be less than the steel racks, how long would they last?

After just a few months of use, a plastic rack might start to degrade after repeated exposure to strong chemicals and sudden impacts. On the other hand, the steel baskets could last for years without needing replacement.

For example, a pharmaceutical manufacturer that contracted Marlin Steel to make test tube racks out of stainless medical steel for them back in 2010 is still using them now! These surgical steel racks were described as:

“Bulletproof, we have not had one issue… some say they are heavier than the plastic but they don’t want anything to change because [the steel racks] do not break and degrade with all the chemical exposures.”

If the plastic racks would last an average of four months to the steel basket’s 6+ years, then the plastic racks would actually have a TCO of 4 x 6 x 3,000, or $72,000. That’s more than seven times the cost of ordering the steel racks.

Overall, steel (especially stainless steel) makes for a stronger, longer-lasting material for pharmaceutical manufacturing baskets and racks than plastic does. 

What about Surgical Steel Vs Stainless Steel?

There are many different kinds of steel on the market. So, the Marlin team is often asked about the differences between different steel grades and their uses. One common question from clients is “what’s the difference between surgical steel vs stainless steel?”

The term “stainless steel” is a broader category that covers thousands of different formulations of steel that have superior oxide resistance compared to plain steel. Meanwhile “surgical steel” refers to a specific subset of stainless steel alloys that have high corrosion resistance and are approved for use in biomedical applications.

Basically, while all surgical steels are stainless steels, not all stainless steels are surgical steels. By definition, an alloy designated as a surgical stainless steel will be better for pharmaceutical applications than a different steel alloy.

Need a set of strong, dependable custom wire forms for your own pharmaceutical manufacturing process? Get started with Marlin Steel today!pharma-basket-tray-checklist