Dupont created Tyvek in 1944 using a process to shred and process polyethylene fibers (HDPE) to form a synthetic paper.  Tyvek did not come onto the market until 1961.

Microporous film was developed in 1987 with a process which takes a thermally laminates a polyethylene film to a polypropylene nonwoven material.  It did not come onto the commercial market until 1993.

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

Polypropylene is widely used today and was developed in 1954.

CHARACTERISTICS
●  Tyvek breathes.  The inherent barrier of Tyvek has many twists and turns which does not allow particles to pass through the material.  This unique property will allow air to pass through easily.  Tyvek is generally six times more breathable than microporous film.

●  Tyvek has a smooth side and a rough side.  Cleanroom garments are sewn with the smooth side out while industrial Tyvek garments have the rough side out.  The rough side will attract and hold micron size particles and should not be used for a cleanroom environment.

●  Tyvek and microporous film will have the highest particle filtration efficiency up to 0.5 microns.  The microporous film has a barrier coating to allow for the low filtration rate.  Tyvek inherent barrier to particles is as small as 1 micron.

●  Tyvek material will have minimal abrasion. Even after surface abrasion, the fabric retains a high level of barrier because the entire thickness of the fabric constitutes the barrier itself.  Microporous material has a laminated film and with abrasion the barrier protection will be compromised because the film will be worn or removed.

●  Microporous material lacks comfort because it is not breathable.  Works well in areas that are constantly wet and optimum protection is required.  Both Tyvek and microporous will be hot to wear.  Both materials work extremely well for optimum protection.

●  SMS and polypropylene have varying  filtration rates since the thickness of the material determines the amount of protection.  SMS ranges from 45 gsm (grams per square meter) to 55 gsm or 1.4 oz (ounce per square yard) to 1.8 oz.  Filtration rate is 10 microns for 55 gsm vs 30 microns for 45 gsm.  SMS will shed liquids for a period of time but is not a complete barrier.  SMS is breathable and will provide adequate protection depending on the level of cleanroom.

●  Polypropylene is the least protective of the materials and has a hold out range of 50 to 70 microns based on material weights of 45 gsm to 30 gsm or 1.4 oz to 1.0 oz.  Many facilities will use polypropylene for visitors and others that will have minimal exposure within the cleanroom or lab area for brief periods of time.

Microporous film is a complete barrier with a coating.  It is meant as an alternative to Tyvek.  SMS and polypropylene weights should be considered when choosing this type of garment.  You can ask your supplier for the manufacturers MSDS sheets on the materials, which should always specify the weight of the material.  How durable is the garment?  Does it fit right?  Look at the stitching and the cut of the garment.  You will be able to compare the quality from one garment to another.  First decide which garment will work best for your application.  The next step will be to compare quality.  The final step is to evaluate the pricing.

For additional specification on disposable garments visit www.CleanroomWorld.com