silicone

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s website and was written by Dan Ewing, senior chemical engineer, Parker Hannifin O-Ring & Engineered Seals Division.

In the rush to massively increase the number of medical ventilators available to treat patients with severe cases of Covid-19, using the correct seal materials for those ventilators should never take a back seat to expediency.

Medical ventilators are mechanical devices that essentially breathe for a patient with damaged lungs. They force air into the lungs and draw it out, augmenting or even replacing the natural functions provided by the movement of the diaphragm and the inflation/deflation of the lungs themselves. These devices can supply room air, pure oxygen, or nearly any ratio of the two to the patient, depending on health needs.

What makes a good seal selection in this environment?

First, seals within the device must be compatible with air and pure oxygen. They should not harden or crack, nor should they contain a significant amount of volatile matter that can evaporate out of the seal where it could be inhaled by the patient or potentially catch fire in a concentrated oxygen environment. Further, it should be assumed that any air that contacts the seals will likely end up in the patient’s lungs. As a result, it's strongly recommended using seal materials that have passed USP <87> Class VI testing for any seals used in a medical ventilator.

Parker O-Ring & Engineered Seals Division has already helped several customers ramp up production of critical medical equipment with supplying the right materials and O-rings for the application.

These application requirements limit the recommended compounds to only a small handful.

Recommended compounds suitable for use in ventilators

When it comes to food, Freudenberg wants to be sure that its sealing materials are free of harmful substances.

In the food processing industry, in order to guarantee food safety, both the food and the hardware that come into contact with it must meet particularly stringent criteria. These guidelines also apply to sealing materials.

In China, specific standards were created in 2016 with the two standards GB 4806 and GB 9685, which deviate from the existing relevant American and European regulations for food-grade materials. To meet the stringent Chinese regulations, FST has now successfully tested two proven VMQ materials: 70 VMQ 117055 and 60 VMQ 117117 for their conformity with Chinese guidelines.

The Chinese standard GB 9685

American Biltrite is pleased to announce the launch of their new IM-S60  industrial grade silicone.

Through high demand, American Biltrite felt this new industrial grade silicone was a natural fit to complete their product offering to assist in covering applications with extreme temperature variations. IM-S60 is a versatile material which offers excellent resistance to UV, ozone, weathering, and resists most fluids encountered in general industrial applications.

The IM-S60 is a 60 durometer, terracotta colored silicone that withstands drastic temperatures ranging from -80°F to 450°F.  This product is now available in stock

The spectrum of elastomers range from very simple forms, like the natural rubber already in use in the 19th century, to modern, high performance elastomers from the second half of the 20th century.  They are continually being improved.

This blog article is the second in a two-part series discussing the many different elastomer materials available today, as discussed in Freudenberg's The World of Freudenberg Sealing Technologies.
The first post discussed Natural Rubber (NR), Nitrile Rubber (NBR), and Hydrogenated Nitrile Rubber (HNBR).

Polyacrylate Rubber (ACM)
ACM elastomers are made of polar acrylic acids. As polar materials, they display good resistance to high-additive lubricating oils. Due to its saturated¹ main chain, the material exhibits good resistance to ozone, weather and heated air. Petroleum-based oils and fluids (for engines, transmissions and automatic transmissions) cannot harm them. But the material offers only moderate strength and low elasticity while displaying limited cold behavior.

There are a plethora of choices when it comes to gasketing material.  But if you are in the food processing, it is crucial that every item that makes contact with the gasket is left unaffected.  And although silicone is inherently non-toxic, only a specially formulated food grade silicone is fit for use with consumables.

Silicone is an ideal elastomer to use if you require FDA-approved rubber.  Since there is an emphasis on rubbers being suitable for repeated use in the food processing industry, silicone is ideal being that the material is not susceptible to harmful microbial agents or other contaminants.  Food grade gaskets and seals should be able to function for long periods of time without falling prey to harmful contamination, or degradation.