The variation between critical environments is essentially limitless. So noting that a wiper is recommended for a certain class of cleanroom isn’t enough. You need to know what makes a wipe ideal for its specific purpose within a cleanroom. Examining the two essential wiper attributes—material and construction—is the first step in determining if a product is fit for specific situations and applications.
Materials: Synthetics, Cotton and Blends
Although the methods employed for constructing a wiper out of any material has a profound effect on its overall fitness for purpose, the base material determines a wiper’s primary strengths and limitations.
Synthetics like polyester and nylon are cleaner than cotton (with less fiber shedding) and also possess a wider range of chemical resistances. However, in addition to a lower tolerance for heat, they are also hydrophobic—meaning that they do not naturally absorb and hold water or aqueous-based liquids. That said, washing treatments of synthetics can significantly increase adsorbency capabilities.
- If you need to wipe chemicals like acids, bases, alcohols, and solvents, synthetics may be the materials to rely on. If high temperatures and large aqueous spills are a primary concern, cotton may be best.
Cotton is hydrophilic, naturally absorbent, strong, and can withstand high temperatures. It can also be environmentally-friendly. However, the very properties that make cotton absorbent also increase fiber shedding during wiping applications, thus increasing contamination.
- If high absorbency and high temperature resistance are of greater concern than particle and fiber shedding, cotton may be your best option. If high abrasion resistance and durability are key to supporting your processes, synthetics should likely be your first choice.
Blends, typically polyester and cellulose, are paired to offer the cleanliness of a synthetic with the hydrophilic properties of a natural material. Blends can do a good job of leveraging the strengths of synthetics and naturals in a cost effective manner, creating varying levels of absorbency and wipability. However, blends are often limited to general cleaning or maintenance usage in supporting areas for more critical environments.
- If you need to be prepared for a range of wiping scenarios, but do not require the critical cleanliness of a synthetic, a blend may be the best material choice for you.
Construction of Substrates: Nonwoven, Knit and Composite
Nonwoven substrates can be made of natural and synthetic fibers and filaments that are turned into a homogenous sheet with chemical, thermal, mechanical or solvent treatment—not knitting or weaving. Hydroentangling, where a high-pressure water spray compresses and bonds fibers into sheet, is a leading process for nonwoven wipers. The biggest downside of nonwoven products is durability.
- If abrasion and shedding are not primary concerns, nonwovens can be a great choice for you to trim consumables costs for less critical environments and applications.
Knitted substrates are made of interlaced loops of yarn, polyester being the predominant base material for knitted wipers. Single knit wipers are usually lighter in weight and less resistant to abrasion; heavier wipers are usually double knit, which resists thread tears and subsequent contamination. Knitted substrates can be combined into multiple layers through a variety of methods, which further increases absorbency and durability.
- If mitigating particle release and fiber shedding trumps consumables costs, knitted wipers are likely the best option for your more critical environments and applications.
Composite wipers are multiple substrate layers fused into one sheet, typically by a pinsonic process (also known as fuse bonding), where sonic waves heat tiny spots throughout each layer, bonding them without threads or chemicals. For wipers, cellulose is typically sandwiched between layers of polypropylene. Although composites offer a potentially broader range of use than a wiper of either individual substrate, their overall applicability to environments and processes will always be limited by the least compatible material.
- If you perform a variety of less demanding wiping tasks and can tolerate higher levels of particle and fiber counts and NVRs and ions, a composite may be your multipurpose solution.
Truly consider these essential attributes before moving onto features like edge sealing and processing. This can ensure that your wiper is truly fit for purpose—from the inside out.