Q. What Is Desiccant ?
A. A desiccant is a substance that absorbs moisture from the air. Desiccant is useful for protecting any sort of sensitive materials from moisture.
Q. Is Silica Gel a Desiccant ?
A. Yes, it adsorbs water vapour by physical means, not a chemical reaction. Water vapour is attracted inside the silica gels crystalline structure.
Q. Silica gel, not really a gel then ?
A. No, silica gel isn't a gel like a hair gel. It is a solid material that comes in granular or beaded forms.
Q. What is DimethylFumarate (DMF) ?
A. Dimethylfumarate or dimethyl fumarate is a biocide used to prevent mold in certain goods, e.g. furniture, textiles, shoes and other leather goods. The use of dimethylfumarate as a biocide has been banned in the European Union since 1998. JEE CHEMICAL INDUSTRIES SILICA GEL / SACHETS do not contain Dimethylfumarate (CERTIFIED BY SGS LABORATORY)
However, there have been reports recently that some goods imported into the European Union contain this chemical as a biocide, and scientific studies have shown severe health effects such as "Chinese sofa dermatitis" after exposure to even small amounts of dimethylfumarate.
Dimethylfumarate has been added by companies to the packaging of some goods in the form of sachets labelled "moldproof" or the like. Some other goods have been imported into Europe from Asia with bags and packets containing silica gel impregnated with dimethylfumarate. Unfortunately, these silica ge l bags and packets were only labelled "silica gel" thus concealing the true content which comprised the banned biocide. Some examples can be found on the RAPEX list of unsafe products (0368/09, 0155/09, 0498/09, 0538/09) at:
Q. Does silica gel get wet after adsorbing moisture/water ?
A. No it doesn't, it traps water molecules inside its pores yet remains dry and appears physically unchanged.
Q. Does silica gel comes ready to use ?
A. Yes. The silica gel does not need to be 'generated' before use. It is sold (loose or in sachets) in a dry condition, ready for use.
Q. How long can silica gel be stored ?
A. The shelf life of silica gel is between 5 and 12 months, although practical experience has shown that it can often far exceed this. The critical factor is to keep it in a sealed environment until it is needed for use. It will, of course, adsorb moisture from any environment. Although the moisture uptake rate is not fast, small sachets can be particularly defenseless to poor storage conditions. It is recommended that they should not be left open to the atmosphere for longer than 25 minutes.
Q. How much moisture / water vapour can silica gel hold ?
A. Silica gel will adsorb up to 40% of its own weight in moisture. Some special kind of silica gel can adsorb 100% of its own weight in moisture
Q. So, silica gel be used anywhere ?
A. Theoretically yes, but it is really only effective in an enclosed environment. In a situation where new air (and moisture) is constantly being introduced, an unpractical amount of silica gel will likely be needed to keep the Relative Humidity at low levels.
Q. Is silica gel dangerous ?
A. Non-indicating (white) silica gel is non-toxic and non-flammable, it is very inert with a very high melting point. It is very much like sand and thus can safely be sent by any means of transport.
Self-indicating (blue) silica gel has been reclassified by the European Union and as of 01/07/2000 has been classified as a toxic material.
Q. Why are there so many different size sachets ?
A. The larger the item that is being protected, the more silica gel is needed. A range of sachets allows for a single sachet to be used in most cases.
Q. How much Silica Gel / what sachet size should I use ?
A. It will depend on the application. For a well sealed item, a rule of thumb is that 20 grams of silica gel are needed for every cubic foot of volume of the package.
Q. How is silica gel regenerated ?
A. Silica gel can be regenerated by heating at 100 - 120Â°C. The heating literally drives off the adsorbed moisture. Regeneration can be carried out repeatedly. When regenerating Silica gel sachets, only the minimum necessary heat (i.e. 34 Â°C - 38Â°C) should be maintained. This will prevent the sachet material from deteriorating.