There is no omnipotent wiper. MicroCare’s Emily Peck said that understanding the priority, material composition, and absorbency of the facility is critical to selecting the right material for the task

To ensure that cleanliness standards are maintained in a clean room environment, wet wipes are an indispensable tool. They need to meet strict standards, especially in a controlled environment.

Any contamination of the items being manufactured and the manufacturing tools and equipment themselves must be eliminated. Wet wipes play an important role in this cleanliness control, but does the use of wet wipes only increase the pollution problem rather than eliminate it? Let's look at the options and how to choose the right wipe to ensure cleanliness.

Although choosing wet wipes may seem simple, it is more than just a flash of light. Wet wipes come in a variety of sizes, materials, and packaging options, all of which affect the cleanliness of the clean room environment after use.

There are three main categories: non-woven fabrics, woven or knitted wipes and cotton swabs, but no matter which one you choose, the first consideration should be its water absorption. Depending on the material composition of the wipe, the absorbency may vary.

The cleanest wipes may not be the most absorbent, and wet wipes that absorb liquids may in turn leave unwanted residues

Absorption is usually expressed in milliliters of liquid absorbed by a square meter of material. However, some wipes can work well with cleaning fluids or lacquers, but they will not absorb water. For example, polyester is petroleum-based, so polyester wipes can easily absorb gasoline, oil, or grease. Cellulose wipes are suitable for water-based pollution.

It is important to note that the cleanest wipes may not be the most absorbent, and wet wipes that absorb liquids may in turn leave unwanted residues.

The cheapest option is non-woven fabrics. These wipes are usually made of paper or fabric. Paper non-woven wipes are disposable items; for example, paper towels. There is a series of "hybrid" paper towels with specially designed "non-woven fabrics".

This material has the strength, softness and quality of woven textiles, but its production, speed and cost are the same as paper. These lint-free wipes are usually used in applications that do not allow recontamination, such as electronics and medical applications, so they are a good choice in clean room environments.

Non-woven cellulose wipes use glue or adhesives to hold the fibers in place. The binder in some nonwoven products accounts for 30% by weight. The most common adhesive is water-based latex, such as polyacrylate.

Many adhesives will dissolve when in contact with cleaning fluids, so wipes made with adhesives are not desirable in critical applications: they leave adhesives, lint, and fibers on the surface being cleaned. Especially when it is humid. Most non-woven cellulose wipes have insufficient strength, cleanliness and absorbency, and cannot handle anything except the simplest cleaning tasks.

Another option is non-woven wipes made of synthetic fibers such as polyester, rayon, and polypropylene. These wipes are suitable for various applications.

For example, textured polypropylene wipes pre-saturated with d-liomine solvent are ideal for cleaning grease and heavy oils. Polyester non-woven fabrics are great for pharmaceutical companies because they can help minimize the risk of bioburden by trapping contaminants in the wipes.

If clean room performance is essential, choose polyester or rayon knitted synthetic fabric

It is important that the non-woven wipes do not wear out in any way, thereby eliminating any damage during cleaning. When in contact with the cleaning fluid, it should be able to withstand cleaning without tearing or dissolving, leaving residue and particle contamination.

Fabric wipes are made of woven or knitted materials and come in a variety of qualities and prices. The cheapest material is recycled fabrics, followed closely by "edging" materials. Please note that they may contain permanent printing chemicals, antifouling agents and dyes, thus increasing pollution problems.

The next layer is washed cheesecloth, but it is very hard and stiff, not suitable for wiping at all, and may wear out. However, once it is thoroughly cleaned with special surfactants and detergents, the material becomes very smooth and flexible.

In terms of fabrics, the best quality wipes are "washed diaper fabrics." This material is soft, strong and highly absorbent, but it is expensive.

If clean room performance is critical, choose polyester or rayon knitted synthetic fabrics. If a high-quality cleaning effect is required, these materials are soft, clean, absorbent and non-linting, and are the first choice.

If you need to clean small places or hard-to-reach places, cotton swabs are effective because the wand design helps to contact contaminants or absorb liquids. The key to choosing a swab is the design of the head. The material of construction, the size and configuration of the head and handle are the main factors to be considered.

Cotton swabs made of cotton fibers may be the cheapest, but it comes at the cost of leaving a lot of lint when used. Reticulated foam is a good cotton swab for scrubbing, but it tends to leave a granular residue. The highest quality cotton swabs are made of pre-washed knitted fabric.

A key factor when choosing a cotton swab is material compatibility. The construction of the swab must be compatible with the cleaning application; if acetone is used on the foam swab, the foam tip will swell and weaken. In applications where acetone must be used, polyester swabs are a better choice.

Wet wipes made of synthetic materials such as polyester non-woven fabrics and knitted fabrics have the widest range of chemical compatibility. On the other hand, cellulosic materials are easily decomposed when used with certain cleaning solutions.

Pre-soaked wipes are easy and fast to use, and are pre-loaded with the correct amount of liquid for the task. They provide the right fabrics and liquids in the right combination, and generally result in more consistent cleaning performance.

A wider range of water-based and solvent-based cleaning fluids enables manufacturers to customize prepreg wipes for different environments. Better packaging allows some companies to provide pre-saturated products with an unlimited shelf life.

The best cleaning solution for pre-saturated wipes is water-based and contains soap, alcohol, hydrocarbons or siloxanes. Stronger liquids, such as d-liomine, usually corrode plastic drums. Quick-drying solvents are also rarely used because they usually fail to meet the required shelf life.

A good toxicity rating (TLV of 200 or higher) is usually a wise strategy. Since the prepreg wipes do not need to have high absorbency-the cleaning solution has been impregnated-they can be made of non-woven fabrics such as polyester, which are ideal for controlled environments.

A good way to reduce lint on paper towels is to choose paper towels with sealed edges. Since wipes are usually manufactured in large rolls, they must be cut into individual units. This process increases the chance of fiber contamination. To reduce this risk, choose wipes with heat-sealed or laser-cut edges, which will melt and seal the end of the fiber and further reduce hair loss.

When choosing the right wipes, don't forget to consider the packaging. Most clean rooms require special "double packaging". They need to be pollution-free, free of fibers, plasticizers, silicones or ions.

Some of the cheapest wet wipes are packaged in cardboard or plastic and are not suitable for clean room environments. When the paper towel is taken out of the box, the cardboard packaging will damage the fibers of the paper towel, resulting in fluff. Rough cardboard packaging may also deposit cardboard fibers on the wipes when pulled from the box.

Some packaging also adds static electricity to the wipes. Then static electricity will inhale dust, increasing the risk of contamination. If you need maximum cleanliness, choose wipes that not only have static dissipative properties but are also packaged in electrostatic discharge (ESD) safe packaging to limit dust absorption. These unique wipes are usually cut and packaged in professional facilities to ensure their purity.

If using pre-soaked wipes, please check that the package is sufficiently sealed and effectively keep the wipes moist to prevent any liquid from evaporating during storage.

When choosing wipes, look for these three characteristics and answer the following questions for each characteristic:

Remember to check how the wipes are done. If you want them to be used in a clean room, choose a sealed edge to eliminate any fiber shedding.

With so many wipe changes on the market, it is important to consult experts and experienced wipe manufacturers to ensure that the product you are using is suitable for the task.

Note: This article was published in the June 2019 issue of Clean Room Technology. The latest digital version is available online.

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