Disposables have become an integral part of many industries today. They are everywhere from the local deli to high-tech electronic clean rooms, and while each industry uses some of the same materials there are many differences.

Disposables have become an integral part of many industries today. They are everywhere from the local deli to high-tech electronic clean rooms, and while each industry uses some of the same materials there are many differences. The four types of nonwoven materials that are most common to today's industries are Tyvek?, polypropylene, microporous film, and SMS (Spun-bonded Melt-blown Synthetic).

Biosafety Protection

Most animal facilities classify themselves as BSL 1, BSL 2, BSL 3, or BSL 4. Most common are the BSL 2 and 3 facilities. There is a big difference between the two and which materials they need to use for their applications. BSL 2 areas can use all four materials depending on the protection levels they require. Most will use an SMS or polypropylene fabric in a lab coat, coverall, bouffant cap, shoe covers, and masks. SMS gives the greatest protection for fluid resistance and hold out while still achieving a breathable comfort level. Polypropylene is used in non-BSL and up to BSL 2 areas where protection is not critical for the user or the animals. BSL 3 and 4 areas require the use of microporous film and Tyvek fabrics.

Weighing the Factors

Choosing and identifying the right materials can be difficult. These materials are used in several other industries and one of the largest users is the industrial safety sector. Their application is to protect the user from chemicals and foreign substances. Animal facilities require protection against viruses, cross-contamination, dander, chemicals, and other foreign substances that can affect the outcome of the research project. Pricing on Tyvek? materials remains a constant since there are only two companies that convert the material, but microporous film, SMS, and polypropylene vary in price by weight and size. There are many different manufactures/converters of microporous film, SMS, and polypropylene. These materials are non-wovens that are sold by weight as rolled goods and then converted to an isolation gown, lab coat, coverall, or shoecover. This means the price of a 1.4 oz lab coat versus a 1.8 oz lab coat can vary by 20% and even more depending on the size cut of the garment. The industrial sector usually wants the cheapest form of protection since it goes to their bottom dollar cost. The research industry wants lower costs to enable more budget dollars for expanded investigations. The difference for research settings, however, is that a compromise in quality, weight of material, and durability can cost a researcher his/her experiment. There are several ways to make sure you are getting what you need.

Dupont created Tyvek under the research efforts of William Hale Charch in 1944. Dupont scientists found a way to shred and process nylon fibers to create a form of synthetic paper. Tyvek? however did not emerge on the market until 1961.

Polypropylene, a major nonwoven polymer in today's market, was developed in 1954 by Guilio Natta. It was put into production in 1957 and there have been many improvements on polypropylene materials since its inception. Two of these are microporous film and SMS.


Microporous film is a polypropylene membrane that is thermally laminated to a polypropylene nonwoven. This material was developed in 1987 through improved processing of polypropylene and came into the commercial market in 1993.

SMS is another derivative of polypropylene that is made up of three layers, two layers of polypropylene thermally bonded together with a thin poly membrane that is perforated.

The basis of use for each of these materials within the animal facilities is the amount of protection they give as well as comfort level. Tyvek? and microporous film materials will yield the highest particulate filtration efficiency. These materials will filter out dry particles up to 0.5 microns. The microporous film material has a barrier coating to allow for the low filtration rate, but lacks in comfort because it is not breathable. This works well in areas that are constantly wet and optimum protection is needed. Tyvek? however does breath to an extent. Both of these materials will be hot to wear in most situations. When optimum protection is needed though, these materials work extremely well.

SMS and polypropylene have varying filtration rates since the thickness of the material instead of the composition of the material determines the amount of protection. The average thickness of SMS ranges from 45 gsm (grams per square meter) to 55 gsm or 1.4 oz (ounce per square yard) to 1.8 oz. The filtration rate is 10 microns for a 55 gsm garment versus 30 microns for a 45 gsm garment. SMS will shed liquids for a period of time depending on the thickness of the material, but it is not a complete barrier. This makes SMS a very desirable material because it is breathable and will give adequate protection over a period of time. Most SMS materials are autoclavable if the snaps do not melt. Polypropylene is the least protective of the materials and has a hold out range of 50 to 70 microns based on material weights of 45gsm to 30gsm or 1.4 oz to 1.0 oz. Many facilities use polypropylene for investigators and others that will have minimal exposure within the animal area for brief periods of time.

Microporous film is a complete barrier with the coating. It is meant as an alternative to Tyvek?. Sizing is what affects the cost of this material generally. SMS and polypropylene weights can be looked at in several ways. First is comparing the thickness to another garment as well as weighing the garment itself. You can ask your supplier for the manufactures MSDS sheets on the materials, which should always specify the weight of the material. The cut size and durability of the garment also reflect the quality. How does the garment hold up and does it fit right for the marked size of the garment? Whenever you look at these materials in any form - lab coat, coverall, etc. - look at the stitching and the cut of the overall garment. You will be able to see many differences from one garment to another.

The decision to use one disposable or another will ultimately come down to price, quality, application, and the end user. Choosing the right one can be difficult sometimes, but application is the best way to start because it allows you to make sure it works first. After that is determined, compare the exact same weight garment to another to evaluate pricing.