What Every Packager Should Know About MIL-Spec Desiccant

       

Mil-D-3464E is the U.S. military specification for silica gel and clay desiccants. It includes requirements for the desiccant performance and packaging, as well as specific test procedures. Desiccant Bags are desiccants that are packaged in porous materials such as Kraft Paper or Tyvek. Desiccant bags absorb moisture, odors and chemicals to preserve and protect your products such as semiconductors, electronics, cartons of food, and all types of machinery.

A “Unit” refers to the Military Specification for packaging of desiccants. The term unit is a quantity of desiccant, which will absorb a set percentage of its weight at certain levels of humidity.

Mil-D-3464E defines a “Unit” as the amount of desiccant needed to absorb:

  • 3 grams of water at 20% RH, 25˚C, and
  • 6 grams of water at 40% RH, 25˚C.
  • A unit is also roughly equivalent to one ounce.

Classifications

Under MIL-D-3464E there are three classifications of desiccant:

  • Type I bags meet the Mil-D requirements for absorption, reactivation, dusting, and durability.
  • Type II bags meet all the requirements of Type I, plus a tighter dusting spec.  (Type II bags are “low dust.”)
  • Type III bags meet all of the requirements of Type I, plus resistance to hot water.

The “dust test” is a measure of how much dust escapes through the bag material. The specification for dusting is:

  • Type I and Type III: Less than 5.0 mg
  • Type II: Less than 0.5 mg
All of the desiccant sold at Edco meets Type I and type II requirements.

Markings

Mil-D-3464E specifies the information that must be included in the print.  If a bag does not contain this information, it is not a Mil-D bag:

  • Nomenclature:  Desiccant, Activated, Bagged For Package Use and Static Dehumidification
  • Specification:  MIL-D-3464
  • Type I, II, or III as applicable
  • Manufacturer’s designation
  • Unit Content
  • Reactivation temperature in bag ____ºF
  • Reactivation time ____ hours
  • Manufacturer’s name and address

Reactivation

In order to re-use the desiccant bags, they can be placed in a circulating oven and baked to drive off the moisture. After reactivation, the bags must be able to pass a durability test (drop test), to ensure that the seal strengths are not compromised. The bags must also retain 90% of their original adsorption capacity. All Mil-D products can be reactivated. Instructions including baking temperatures and times are printed on each Mil-D bag. We recommend reactivating clay desiccant a maximum of 5 times.

For pricing and more information on desiccant click here.