Dry Storage Desiccators

WHICH MATERIAL FOR YOUR CABINET?

Some infornation on materials used in the fabrication of dry storage, desiccator cabinets.

ACRYLIC

A plastic material noted for its transparency, weather resistance, colour fastness. Acrylic is important in preservation because of its stability and resistance to chemical change. Acrylic is available in sheets, films and resin adhesives. Some common trade names for the sheet form are Perspex™, Lucite® and Plexiglas®.

PERSPEX

Perspex is the brand name for acrylic sheet produced only by Lucite International. Its chemical name is polymethylmethacrylate, or pmma for short. It was one of the modern generation of plastics first produced in the mid 1930's.

Perspex is derived from a petrochemical feedstock, with the main raw material being acetone. Acetone is converted into a chemical called methyl methacrylate, which is then polymerised into Perspex. Due to the strength of the brand some people refer to any clear plastic as being perspex which is not true! Not only that, Perspex is manufactured and sold in a myriad of colours, tones and surface effects.
Three distinct types of Perspex are:

1 Cast Perspex - Originally invented in the 1930’s and continually improved for over 60 years. The product with the best mechanical and optical properties, and overall performance.

2 Extruded Perspex - the product with the best thickness tolerance. Typical tolerance levels are +/-5%

3 Impact Modified Perspex - Products with improved impact performance where a greater degree of damage tolerance is needed in service.

All of these materials are made from the same raw materials and hence not unsurprisingly all of the products have similar benefits in service. A wide variety of grades are available to meet specific application performances or for ease of processing.
Some of the benefits of Perspex in use are:
- Some Perspex products have been used used for over 30 years outdoors without significant deterioration. Cast and extruded PERSPEX are warranted for a 10-year outdoor service life.
- Excellent Clarity - with 92% light transmission Perspex has superb water white clarity and transmits about 10% more light than glass. Recent fashions for POP displays, shelving and furniture have required a material to resemble the edge colour of glass.
- Safe and easy to Use- Perspex sheet is often used in glazing applications and is a safety glazing product meeting the relevant safety standards. It is half the weight of glass of the same thickness with at least 5 times the impact strength and with none of the breakage problems associated with that material. Fabricating items is relatively simple, as Perspex is easy to work with using standard workshop techniques.
- Fully Recyclable- unlike other plastics, Perpex has one very unique attribute - end of life products and waste can be fully recycled. At high temperatures Perspex acrylic sheet is transformed back into its base raw chemical - methyl methacrylate - which is fed back into the process. This is referred to as Closed Loop Recyclability. The result of this is that even black Perspex can be recycled into clear Perspex without detrimentally affecting its renowned quality.

In Summary the Properties of Perspex are;
• Exceptional light transmission with virtually no colour bias -
even in thick blocks.
• Excellent resistance to outdoor weathering.
• Good resistance to impact.
• A high gloss, hard surface.
• High tensile strength and rigidity.
• Easily thermoformable with simple workshop tools.
• Easy to clean.
• Capable of being fully recycled.

Perspex Cabinet Cleaning. For all general purpose cleaning operations, PERSPEX should be washed simply with
clean cold water to which a little detergent has been added. The use of
any solvents such as methylated spirits, turpentine, white spirit or
proprietary window cleaning products is neither necessary nor
recommended.

STAINLESS STEEL

We can manufacture your cabinet in whatever grade of stainless steel you prefer. To help you choose below is some specifications on the typical grades. If you're not sure then call us, as we can advise depending on your application.

Grade 304. Austenitic Cr-Ni stainless steel. Better corrosion resistance than Type 302. High ductility, excellent drawing, forming, and spinning properties. Essentially non-magnetic, becomes slightly magnetic when cold worked. Low carbon content means less carbide precipitation in the heat-affected zone during welding and a lower susceptibility to intergranular corrosion.

Grade 316. Often refered as 'marine grade'. Austenitic stainless steel. Excellent corrosion resistance. Excellent elongation. Non-magnetic. Easily weldable. Can be polished to a mirror finish. Provides better elongation and ductility over the "standard" grade. Often used for food industry, marine, medical, and applications where corrosion resistance is of higher importance over that of strength or wear resistance. Essentially this grade would provide better magnetic resitance than 304, but if this is not an major issue in your application then 304 will suffice.

Routine Cleaning of Stainless Steel Cabinets. Use soap, mild detergent or ammonia solutions in warm water, applied with a soft cloth or nylon sponge. Occasionally the use of the least course nylon scouring pad may be required. Rinse and dry with a soft cloth.

Also some hygroscopic plastics such as plexiglass® will absorb moisture from a high humidity external environment and pass it through into the cabinet. If your application does require a barrier from a very humid environment, then perhaps Stainless Steel should be considered for you desiccator cabinet. However we find that in most applications acrylic dry storage cabinets and desiccators perform well and of course provide a 'visual' advantage over a metal walled cabinet and thus are likely to be opened less for content inspection, comprimising the environment within. The choice however is yours!

TEMPERED GLASS

Tempered glass is about four times stronger than "ordinary," or annealed, glass. And unlike annealed glass, which can shatter into jagged shards when broken, tempered glass fractures into small, relatively harmless pieces. As a result, tempered glass is used in those environments where human safety is an issue. Often used as rear windows in vehicles, entrance doors, shower and tub enclosures, racquetball courts, patio furniture, microwave ovens and skylights.

PVC

Plastic usually abbreviated as PVC, or sometimes 'vinyl'. Not as chemically stable as some other plastics. PVC can emit acidic components which damage susceptible materials such as paper. Added chemicals called plasticizers are also used to make PVC more flexible. These also damage library and archive materials.

PVC STATIC DISSIPATIVE CABINETS

PVC Static Dissipative Plate. Semiconductors and other sophisticated electronic components are vulnerable to the effects of electrostatic charges throughout the manufacturing process.
The mechanical abrading of surfaces causes electrons to flow from a supplying surface (positive charge) to a receiving surface (negative charge). As a result, dust can be attracted to clean room walls, floors and ceilings, to manufacturing equipment surfaces, and directly to circuits and contacts of semiconductor devices, with devastating effects.
Moreover, the build-up of static charges can result in uncontrolled electrostatic discharges (ESD) capable of affecting numerous devices per incident.
It is therefore essential to limit materials to those capable of dissipating static charges (106-8 Ohms/square surface resistivity), and to provide grounded connections by means of wiring or secure contact with other grounded materials.
Since transparent plastics are insulative by nature (>=1014 Ohm/square surface resistivity), imparting of electrical properties requires molding of opaque, conductive particles into the resin or, in the case of ESLON® DC Plate, applying coatings that are both conductive and transparent.
ESLON DC Plate Satisfies Electrical and Optical Requirements

ESLON DC Plate is comprised of clear plastic sheet coated on both sides with a conductive, transparent surface two-microns in thickness, providing surface resistivity in the static dissipative range of 106-8 Ohms/square.
To meet broad application requirements, the plastic substrate is available in PVC (best chemical and fire resistance - UL Std. 94 V-0), polycarbonate (outstanding high temperature performance and impact resistance), PMMA and A-PET (optimum clarity).
The substrates are offered in 4 colors: clear, transparent orange, transparent yellow, and transparent smoked bronze. The coating is available in two grades: "standard coat" and "hard coat," the latter being a cross-linked version providing superior abrasion and chemical resistance.
ESLON DC Plate is also heat-formable using conventional "drape forming" and "wire forming" methods, allowing two-dimensional bends up to 90° as well as compound curves.
The electrical, physical and optical properties - and formability - of ESLON DC Plate make it suitable for a broad variety of electronics manufacturing applications including:
• Machine and instrument covers and guards
• Clean room glazing and cleanroom cabinets
• Instrument panels
• Minienvironments
• Circuit board test equipment
• Copy machines
• Static sensitive components in dry storage cabinets or desiccators

PVC STATIC DISSIPATIVE SPRAY

We can prepare your dry storage, desiccator cabinet with a static dissipative spray. Or alternatively you can obtain the spray and further details directly from..Chiltern Connections Ltd

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