By Robert McIlvaine and Betty Tessien, The McIlvaine Company
Cleanroom garments must protect product from the contamination caused by the wearer, but they must also be comfortable and cost-effective. The first decision a cleanroom operator must make is whether to select disposable or reusable garments. Often it is a complex decision: Visitors may be given disposable garments, for example, while workers in various parts of the facility may use either reusable or disposable garments depending on the cleanliness requirements and other considerations.
Although operators of Class l (ISO Class 3) semiconductor facilities tend to opt for high-quality reusables to minimize particulate and molecular contamination, those operating sterile facilities generally lean toward disposable garments because of contamination concerns (e.g., when reusable garments are returned from the processing facility).
This article will focus on the disposable option: Where and when are disposables utilized? Who supplies the fabrics? Who supplies the finished clothing? How big is the market?
Human beings disperse particles from their bodies (e.g., skin, hair, perspiration, oil) and from their indoor, non-cleanroom clothing at a rate of several million particles per minute and several hundred bacteria-carrying particles per minute. According to ISO 14644-5, the primary function of cleanroom clothing is to act as a barrier filter that protects product and processes from human contamination. It should be:
- Made from a fabric that filters human-dispersed contamination.
- Designed to envelop a person, preventing significant amounts of unfiltered body emissions to be dispersed into the cleanroom.
Suppliers point out that the cost of cleanroom disposable garments is simply a delivered price based on actual usage. On the other hand, there are many cost variables associated with reusable garments: In addition to the weekly rental fee, such factors as laundering, sterilization, repair of garments, replacement of lost or ruined garments, hangers, totes and barcode charges, fuel surcharges and additional unplanned garment usage charges may be included in a final cost.
DuPont’s Tyvek® is well known in the cleanroom industry as a fabric used for disposable protective clothing. Tyvek is fabricated from millions of very fine, continuous, polyethylene fibers overlapping to form a dense sheet that functions as a protective shield. The unique process used by DuPont to manufacture these fibers is known as flash-spinning.
Tyvek was originally tried in cleanrooms in the early 1960s. It favorably passed tests designed to compare it with woven fabrics and rate it for comfort. This nonwoven material has been upgraded over the years and has proven to be a good performer in Class 100 (ISO Class 5) to Class 100,000 (ISO Class 8) environments, depending on garment processing and packaging. Free-fiber generation at wear points, however, is a disadvantage of this material. Also, Tyvek garments can be treated to make them static-dissipative but not static-shielding. It’s a breathable fabric that provides filtration efficiency for submicron-sized particles and microorganisms, and it’s suitable for light splash protection from non-hazardous liquids. Unlike film laminates, the protective properties of Tyvek are an inherent feature of the material and cannot be abraded or scratched off. Average use is two to three days, except in sterile areas where three or four garments are used each day. Recleaning is possible, but shedding increases with each laundering or dry cleaning.
Tyvek garment fabric is chemically and biologically inert. Its physical properties are unaffected by most organic and inorganic chemicals, including acids, bases and salts. The fabric can absorb certain organic solvents, however, causing slight swelling of the material before the solvent evaporates.
Tyvek material is highly opaque and has high tensile-tear strength in all directions, wet or dry. Water has no effect on its strength, and it retains its toughness and flexibility down to -100°F. Because it is a synthetic, nonwoven fabric, its flammability characteristics are similar to most synthetic fabrics. If exposed to a flame, Tyvek will shrink away quickly.
Spunbonded-meltblown-spunbonded (SMS) fabric features two unique outer layers made with spunbonded polypropylene for extra strength and clothlike comfort. The two middle layers are composed of a matrix of microfibers that act as a filter to keep out many fine particulates and water-based liquids. The fabric is breathable, but typically provides less particle and microbial barrier than Tyvek.
Spunbonded polypropylene (SBPP) is a generic class of nonwoven material with minimal barrier properties used in low-cost, disposable commodity applications such as bouffants, shoe covers, coveralls, lab coats, and shirts and pants.
Compressed polyethylene (CPE) is a film made from a mixture of 65 percent low-density polyethylene and 35 percent light low-density polyethylene. This extremely lightweight product is a complex hydrocarbon chain, making it practically impervious; hence it is excellent for containing moisture and dirt. It is used in situations where physical properties must be unaffected by either chemicals or solvents.
BF Goodrich offers a barrier film that allows moisture to escape while preventing liquids from penetrating. This high moisture vapor transmission (HMVT) fabric incorporates monolithic film technology to provide textile producers with waterproofing qualities, selective permeability, tear and puncture resistance, and barrier protection.
The product arrives in the form of pellets that can be solvent- or extrusion-coated directly onto a fabric or made into a film, which can be laminated onto a fabric. When used to produce cleanroom apparel, the film features high puncture and abrasion resistance, is non-gassing and non-flaking, and is static dissipative.
Alex Sardarian of Total Source Manufacturing stated that its cleanroom disposables come from China. Many disposable garments are made of Tyvek because that material has been around the longest, has low particle shedding and is suitable in multiple applications. However, in the last ten years, four or five other materials have been created that are more application-specific. Buying a specific disposable garment for a specific application, such as asbestos removal, paint spray booths, agriculture, chemicals or certain manufacturing processes, can reduce cost. A case of Tyvek garments can sell for $80 per case of 25 garments whereas garments for a specific application may sell for $30 per case.
DuPont has a new technology called Advanced Composite Technology (ACT) that uses patented bicomponent fiber technology to deliver a fabric with a unique balance of barrier, thermal comfort and ease of movement for areas where the superior barrier properties of Tyvek are not required. Suprel® LS is made with polyester for strength and polyethylene for softness to create a fabric that delivers a high level of protection without compromising comfort. Suprel LS cleanroom garments will be available in both bulk and gamma-sterilized versions.
Suppliers of finished clothing
Joyce Wasserman of Cardinal Health stated that it currently distributes disposable cleanroom garments for use in Class 100 ( ISO Class 5) to Class 100,000 (ISO Class 8) environments. Cardinal Health operates the largest FDA-regulated gamma radiation sterilization facility in North America, making them one of the market leaders in sterile, disposable cleanroom garments.
Cardinal Health’s Sterile Micro-Clean garments are made from Tyvek. They’re laundered and sterilized with gamma radiation; individually bagged to control particulate; and packaged in a Class 10 ( ISO Class 4) cleanroom. Cardinal guarantees a sterility assurance level of .000001, which means there is one chance in one million that a viable microorganism is present in the sterilized article. This is the highest sterility assurance level in use.
The pharmaceutical manufactur-ing industry is interested in particulate control as well as sterility, while electronics manufacturers are more concerned with particulate. Biotech companies require no cross-contamination; therefore, according to Wasserman, disposable apparel makes the most sense. Also, pharmaceutical or biotech companies that run production on a seasonal basis benefit from disposable apparel by avoiding long-term contracts. With disposable apparel there are no hidden costs: Lost or damaged garments are not part of incremental charges to the customer.
Cardinal Health offers three different lines for nonsterile cleanroom disposable garments. Micro-Clean 2-1-2 Opti-Soft is a laundered Tyvek garment. It’s polyamide-coated to eliminate loose fibers and packaged in a Class 10 ( ISO Class 4) cleanroom. These garments can be recycled to further reduce costs and encourage environmental conservation. Global Recovery Systems, for example, is a company that has a comprehensive recycling program for disposable garments.
Wasserman sees the following trends in cleanroom apparel:
- Increased focus on eliminating risk of mold contamination in cleanroom and surrounding areas
- More frequent garment changes for nonsterile environments
- Increased usage of sterile garments and sterile gloves in nonsterile environments
- Increased standardization enacting latex-free initiatives for gloves and garments in the cleanroom
- Increased need to standardize purchasing of cleanroom and general-use apparel across global organizations
- Increased demand for single-use (disposable) garments versus launderable (reusable) garments due to concerns about cost, barrier protection, cleanliness and cross-contamination
Cardinal Health and others have compared the comfort trade-offs between disposables and reusable garments. The air permeability characteristics of the two types of garments are equal. However, on the basis of weight and emotional comfort, disposable garments often have an increased perceived comfort rating. On the basis of water vapor transmission rate and material stiffness, launderable garments often have increased perceived comfort.
Walter Seemayer of Critical Environmental Consultants notes that cleanroom managers will always be faced with a difficult choice between disposable and reusable garments because of their competitive market positions and uncertain business variables. However, the most cost-effective choice will always be disposable garments in a medium- to high-risk cleanroom environment. Risk can be defined by:
- The potential for cross-contamination either at the cleanroom facility or at the laundry
- Uncertainty with respect to the quantity or sizes of visitors and service personnel
- Operator turnover or changes in size (pregnancy, for example)
- Severity of use
- Uncertainty in production unit forecasts and time frames, from prototypes and start-ups to exponential growth
- The internal cost of effectively managing reusable garment systems
- The amount of money available at a given point in time
DuPont offers IsoClean, ProClean®, Suprel® LS, and Summus® disposable garments to meet the diverse needs of those who use traditional disposable cleanroom garments. The lightweight, nonwoven Tyvek fabric used in IsoClean garments is durable and provides excellent barrier properties. Cleaned garments are processed and packaged in an Class 1 (ISO Class 3) cleanroom, and sterile garments come with a “Certificate of Irradiation and Sterility.” ProClean garments are made from a proprietary microporous composite fabric that offers an exceptional liquid and particulate barrier. Suprel LS garments utilize DuPont’s Advanced Composite Technology to offer garments with good liquid and particulate barrier properties and exceptional comfort at affordable prices. And Summus garments, made from SMS fabric, are an economical choice with good barrier and breathability qualities.
According to Alvin Chapital of Kimberly-Clark, K-C provides disposable garments and accessories for all industries. Its garments are low particulate-shedding, using SMS fabric designed to provide strength and clothlike comfort. The garments are made in facilities around the world under its direction. Kimberly-Clark is committed to providing quality, innovative products to this market.
Kimberly-Clark’s Kleenguard brand products have a patented microforce barrier fabric and, according to the company, feature outstanding particulate holdout and claim to be 25 times more breathable than Tyvek. The fabric has a clothlike, abrasion-resistant, spunbond polypropylene outer layer and includes a middle layer comprising an intricate web of microfibers that filter out many water-based liquids and dry particulates.
Gina Struebel of Alpha Pro Tech stated that Alpha Pro provides head-to-toe coverage with its disposable products. Its nonsterile garments are used in up to ISO Class 4 cleanrooms, mostly in the pharmaceutical, biopharm, research and electronics industries. The garments are made under the company’s jurisdiction from proprietary fabrics in facilities in the U.S., Mexico and China. Alpha Pro will issue a press release soon announcing new, proprietary cleanroom disposable products.
According to Daniel Edwards of Lakeland Industries, Lakeland manufactures reusable garments and disposable Tyvek garments for industrial, nonsterile use, as well as Tyvek garments for cleanroom use. With manufacturing facilities in China, Mexico and the U.S., Lakeland supplies garments globally. It’s the largest converter of Tyvek roll goods, but offers other fabrics to meet niches in the marketplace, giving customers alternatives.
Cellucap/Melco Manufacturing supplies a full line of disposable apparel and accessories for healthcare, laboratory, industrial safety, cleanroom and food-service applications. Its national network claims on-time delivery and personal assistance.
Shenzhen Selen Static Scientific Co., Ltd. was founded in 1993 and the company claims that it is now the largest cleanroom garment manufacturer and ESD products dealer in China. It has four processing bases and three major marketing centers throughout China. Selen believes its systematic R&D, processing, marketing and servicing networks are superior.
VWR Scientific Products is one of the largest distributors of disposable garments, offering products from Kimberly-Clark, Cardinal Health, DuPont and CleanWear.
Garment usage has been derived from the number of employees in each industry in each class of cleanroom. In a Class 100 (ISO Class 5) pharmaceutical cleanroom, the average usage is four per day but the protocol dictates that changes must be made each time the cleanroom is re-entered. In contrast, a worker in a Class 100,000 (ISO Class 8) cleanroom might change garments once or twice per week. Another important factor in determining the number of disposable garments used is the split between disposable and reusable. This varies greatly by industry as shown in Table 1.
Table 1: Disposable garment use by category
Generally, more expensive garments are worn in cleaner areas. Therefore, another challenge is segmenting disposable garment revenues by cleanroom class. In the case of the semiconductor industry, only about 5 percent of workers are in disposable garments-and they are all in the less clean areas (see Table 2).
Table 2: Percentage of disposable-garment revenue by class
The world market for disposable cleanroom clothing will double over the 2001-2009 period (see Table 3). This is a little misleading in that the 2000 market was considerably higher than the 2002 market, but nevertheless the market is enjoying considerable growth.
Table 3: World market for disposable garments ($ millions)
Most of the growth in reusable clothing is in Asia due to the activity in flat panel display, disk drive, and semiconductor investment, whereas the disposable market is rather balanced among U.S, Europe and Asia.
The future of disposable garments will firstly depend on the cost competition with reusable garments. New materials, which increase comfort while maintaining or even decreasing cost, would contribute to maximizing the market penetration of disposable garments. Sterility, particulate shedding, and even offgassing characteristics will continue to be important. In addition, the option of recycling provides additional advantages in both cost and environmental improvement.
Robert McIlvaine is president and founder of the McIlvaine Company, Northfield, Ill. The company first published “Cleanrooms: World Markets” in 1984 and has since continued to publish market and technical information for the cleanroom industry.
Betty Tessien is the cleanroom publications editor for the McIlvaine Company.