Isopropyl alcohol wipes are a very common consumable in cleanrooms, therefore their selection and correct use is part of the fundamentals of cleanrooms. Matt Hatfield from High Tech Conversions talks through your options
When it comes to isopropyl alcohol wipes (also known as IPA wipes), the smallest things can make a world of difference. Understanding the unique attributes in the vast sea of options can significantly help with the selection process. It can mean finding the ideal wipe versus investing in a solution that does not match the intended use, ultimately rendering the wipe ineffective. There are three qualifiers when it comes to what type of IPA wipe to use. They are saturation level, size, and material.
While some of the differences are not obvious at first glance, they can be substantial. Saturation levels can range from 1% to 99% - in any combination of isopropyl alcohol and deionised water. Size variations are as equally plentiful. Common sizes include 7" x 7" and 9" x 9", but they can be much larger or smaller depending on the manufacturer and the intended application. Lastly, the wipe material itself will determine absorbency and cleanliness, both significant factors in the cleanroom.
Isopropyl alcohol requirements can vary for each unique application. For example, 70% IPA may be suitable for general-purpose wiping of stainless steel, plastic, glass, and other hard surfaces within the cleanroom. Removal of tougher adhesives and residues might require a higher concentration level, such as 90% or higher.
According to a pair of reports undertaken by the Centers for Disease Control (CDC), wipes with a concentration of isopropyl alcohol of at least 70% are successful at disinfecting surfaces in controlled environments. Uses for wipes in such an environment include:
Furthermore, the USP (United States Pharmacopeial Convention) states in USP797 that "floors, walls, ceilings, shelving, hard surfaces, contaminated gloves, and supplies removed from shipping cartons are to be wiped with 70% Sterile Isopropyl Alcohol."
It should also be noted that not all presaturated IPA wipes are made with the same type of isopropyl alcohol. There are three types commonly used. Knowing the different grades of isopropyl alcohol is critical when making a wipe selection.
ACS (Spectrophotometric grade): This is the highest purity standard sold on the market today. It is used in cosmetic and personal care items (i.e. toiletries) as well as composing the formula for rubbing alcohol.
USP/Medical/Pharmaceutical grade: This is the most widely-ranging type of IPA with uses across many industries. It can be found in the likes of cleanroom wipes, medical wipes, cosmetic products, and the manufacture of certain drugs.
Industrial/Tech grade: This is most well-known as a technical and industrial solvent and cleaner. Its applications include wiping and cleaning surfaces, inks, coatings, and printed circuit boards (PCBs) inside computers. Because it has the lowest purity standards among the classes, it cannot be used for drugs, food, or medicinal purposes.
Choosing the correct wipe size will be determined by the task and surface. Smaller wipes, those ranging in size from 4" x 4" to 7" x 7", are particularly effective for cleaning smooth surfaces and small parts or accessories. For example, 4" x 4" wipes are regularly used in the optics industry for wiping glass surfaces.
The larger sized wipes are ideal for cleaning spills, equipment, and other complex surfaces. For larger wipes, which start at 9" x 9" and extend up to 12" x 12" and even larger, the best way to maximize the cleaning ability is to fold the wipes into quarters, thus creating eight full layers of absorption.
There is an artform to wiping that maximises the coverage area that can be cleaned with a single-use wipe and prevents the user from hitting the same spot time after time. Follow these steps when wiping surfaces with an alcohol wipe.
When wiping surfaces with an IPA wipe, start in the cleanest area (if one can be identified) and wipe towards the less-clean areas, using strokes that overlap each other in a parallel direction. Do not wipe in a circular motion, even though that is a standard way of doing things, such as washing one's car.
IPA wipes eliminates the need to use a sprayer so greatly reduce VOCs
Wiping in a circular motion spreads the contaminants and foreign substances from the dirty area.
To limit the contact of each swipe, turn the wipe so that the next swipe is done with a clean side. Try to keep the overlapping areas to about 10% to avoid leaving streaks of foreign substances or unwanted particles behind. Constantly moving to a clean wiper surface prevents the user from eradicating their own work. Every time a wipe becomes contaminated, it must be disposed of; used wipes should never go anywhere but into the trash.
IPA Wipes are manufactured from a host of different materials, each one offering unique benefits including:
Polyester: This material yields exceptional durability and cleanliness. Edges can be thermally sealed to prevent loose ends and linting. Additional measures can be taken to further enhance cleanliness such as washing and processing / packaging the wipe in a cleanroom. Polyester wipes with sealed edges are commonly used in ISO 3-4 (Class 1-10) cleanrooms, Polyester wipes without sealed edges can be used in ISO 5-6 (Class 100-1,000) cleanrooms.
Polyester/Cellulose blends: These wipes can be engineered to meet unique requirements. Polyester/Cellulose blends are clean, absorbent, and an economic choice. Like polyester wipes, this material can be cleanroom processed to enhance cleanliness. They are common in ISO 5-7 (Class 100-10,000) cleanrooms.
Polypropylene: Polypropylene is soft, non-abrasive, and solvent resistant. It's suitable for wiping sensitive surfaces and components. Polypropylene can be cleanroom processed and washed to further enhance cleanliness. It can be presaturated with a variety of solvents, sterilised, and cut to any size. Common for ISO 6 (Class 1000), in some cases ISO 5 (Class 100) cleanrooms.
There are a variety of benefits that come with using presaturated IPA wipes. Those range from cutting costs and improving workplace safety, to ensuring the exact amount of isopropyl alcohol is used with each application.
Ease of use: Standard wipes are not pre-wetted, unlike IPA wipes, which come from the manufacturer with a specific percentage mixture of IPA and water. When one tries to use a dry wipe and solvent in a spray bottle, the results can be time-consuming, challenging, and can ultimately lead to an incorrect amount of IPA being distributed. When equipment or conditions must meet certain requirements, using measurements that seem "close enough" is not a viable solution. When using a presaturated wipe, you can be sure the exact saturation level is delivered consistently.
Cost efficiency: IPA wipes are packaged in tubs, bags, and boxes that are manually resealable. While this does not result in a total eradication of the evaporation of the agent, it can slow it down considerably. This ensures that each package lasts longer and that remaining wipes in the enclosure maintain the proper standards of cleaning agent throughout their lifespan. This dramatically decreases the chances of having to throw away wipes that have been rendered ineffective by a loss of moisture.
Reduction of volatile organic compounds (VOCs): Using IPA wipes eliminates the need to use a sprayer. This will greatly reduce the element of VOCs from the equation. That leads to an overall cleaner environment, something that is particularly important in critical environments that monitor VOCs. Additionally, VOCs emit chemicals that cause both short and long-term negative health effects in humans.
Safety: Under certain conditions, the spray bottle version of IPA is flammable, like most alcohols. Pre-wetted wipes are a lot less likely to be a fire hazard. They also reduce the potential for the user to have chemicals exposed to their body via the skin or through inhalation of chemicals, which are also common risks with the sprayer.
Convenience: Presaturated wipes remove the need for workers to spend time preparing, mixing, and diluting cleaning agents. Therefore, they help concentrate the efforts of valuable staff members towards more worthwhile activities within the cleanroom.