Monday, June 8, 2009

The choice of gloves for the isolator unit is critical to success

A ‘hands on’ approach

With a wide selection of gloves available, loss of manual dexterity when using gloveboxes need not be an issue, argues Phil Vanes, technical sales manager of Polyco

The choice of gloves for the isolator unit is critical to success

Contamination control is a vital aspect of health and safety in areas where environmental sterility is a critical concern. The purpose of the wide range of contamination control procedures and standards is to ensure cleanliness by reducing or eradicating all viable and non-viable contamination, and maintaining an efficient rate of production.

Containment technology is typically used where a very high classification cleanroom environment is required. There are two key scenarios: where the user needs to be protected from the item, such as nuclear or laboratory applications, or where the item needs to be protected from the user, such as in medical applications. In some instances, as with drug manufacture, the containment unit does both – protecting the user from materials which may be toxic while ensuring that the preparation remains pure.

Containment technology – gloveboxes or isolators – simplifies some of the contamination issues that can exist in the cleanroom. In a cleanroom, users need extensive personal protection including respiratory equipment to maintain a high class environment. Areas such as entrances need to be carefully controlled, in some cases requiring an airlock to ensure the absolute minimum risk. But where the procedure is small enough to be contained within a sealed unit, many potential contamination problems are eliminated by isolating it in a glovebox.

The choice of gloves for the isolator unit is critical to operational success. Historically, however, the units have come fitted with basic level gloves, which may not be ideal for the procedure. Then, because the options are not clearly understood, rather than upgrade the gloves on replacing them, users tend to replace like with like.

Commonly, the gloves supplied with such units are heavy-duty latex or neoprene, which are not ideal for several reasons. Owing to latex protein allergy, several applications, particularly those associated with medical preparations, prohibit the use of latex. Latex gloves that have been manufactured using the coagulant dipping method can also shed particles.

Neoprene is another commonly used elastomer; again, this has several problems in a cleanroom environment, including possible particle shedding. The heavy duty nature of the glove can also inhibit dexterity, reducing productivity; also, frequently the gloves are offered only in limited sizes so may be ill fitting. Ergonomic or Repetitive Strain Injury (RSI) problems could also occur because the operator has to perform manipulations using unnatural hand shapes and irregular positions.

However, the choice of gloves available to fit in such scenarios is comprehensive. Users can select a product that is more suitable for the task in hand. A number of factors need to be considered: not only what materials are to be handled and whether hazardous substances are involved, but also the method of sterilising the containment unit.

For example, hydrogen peroxide is often used as a fumigating agent, while hospitals often use chemical wipes for sterilisation. These can affect the integrity of the glove, potentially making it porous or brittle. Users need to be aware of all the substances the glove is likely to come into contact with to avoid affecting its integrity.

To improve ergonomics, several different sleeve-glove combinations exist. In such applications, a cuff mechanism attaches the glove closely to the sleeve to avoid gaps that could introduce contamination or cause loss of containment. Some cuff systems are based on a cartridge that allows a glove change to take place without breaking containment. Such combinations can allow the use of two different materials; for example, a robust sleeve can provide heavy duty, durable protection combined with finer gloves for greater manual dexterity. Although the finer gloves might need to be replaced more frequently, the greater dexterity offers far higher productivity. As the stronger sleeves deteriorate less rapidly, it is not necessary to change them as often, so there is an inherent cost saving.

More sophisticated gloves that might be suitable in this environment include those made from materials such as butyl rubber or Viton. Butyl rubber is a highly flexible unsupported material offering good gas impermeability and ozone resistance for laboratory conditions. Gloves produced using the specialist Viton elastomer offer unparalleled resistance to aromatic hydrocarbons and chlorinated hydrocarbons and can be manufactured with a secondary layer of neoprene, which improves mechanical resistance.

Polyco also produces gloves using Hypalon, designed to give a low modulus product and a very flexible gauntlet. Hypalon is chlorosulphonated polyethylene and shows its true strength when exposed to high temperatures, oxidising chemicals and oxidising environments such as ozone, active oxygen and free radicals. It resists flex cracking and abrasion as well as the damaging effects of weather, UV radiation and ageing. Hypalon has demonstrated long life in harsh environments and is used in high performance applications. In addition, it offers good flame resistance and good mechanical and low temperature properties.

New solutions developed using polyurethane offer possibly the best protection of all. The material has great mechanical strength, which minimises the risk of rips and tears that can result in the loss containment and in a worst case scenario, abandonment of the whole batch.

It can be offered as a standalone material or as a laminate, where a “sandwich” structure to the film combines, for example, the chemical resistance of Hypalon or Viton (product facing layer), with properties of the polyurethane secondary (skin contact) layer. This can also act as wear/failure indicator where the blue polyurethane layer is exposed should the white Hypalon layer be compromised.

Sleeves are available in 10 different materials, but natural rubber latex, Hypalon and Vinyl are used for most applications. Polyco’s Isoflex brand is a two-layer vinyl/dartex product, a high quality sleeve manufactured using a unique welding process that gives a guaranteed weld line without material “rucking”. The sleeves offer the added safety feature of allowing the user to see if the outer surface has been punctured by simple separation of the two layers. This allows the process inside the box to be completed to a “safe” stage, at which point the sleeve can be replaced.

Key to glove security is a thorough test process. BM Polyco has its own UKAS accredited technology centre that carries out stringent tests to certify all gloves. Polyco’s range of drybox and isolator gloves are air leak tested and visually inspected for holes and flaws. All reject gloves are destroyed.

Chemical resistant gloves are tested for resistance to several common chemicals including methanol, acetane, acetronitire, dichloromethane, carbon disulphide, toluene, diethylamine, tetrahydrofurane, ethyl acetate, n-heptane, sodium hydroxide and sulphuric acid. Resistance to permeation is assessed by measuring the time taken for a chemical to break through the glove material. Samples, cut from the palms of the gloves, are placed in a permeation cell, which enables the chemical to be placed in contact with the outer surface of the gloves. Collection air or water is passed through the cell to collect any chemical that has broken through to the inside surface of the glove sample.

Users of gloveboxes have the opportunity to improve comfort and ease of operation significantly. By selecting a product that meets the need for both protection and dexterity, tasks can be completed quickly, efficiently and without compromising the cleanroom environment.

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