Static Electricity build-up in dryers has been a challenge in the textile industry since the invention of the tumbler dryer. One of the main reasons why this issue has continued to be a problem is the lack of understanding of the cause of static electricity and how to mitigate it.
Static electricity is generally agreed to be caused by the triboelectric effect, which is simply the rubbing together of dissimilar materials. During the rubbing process, electrons from one material with a weak affinity for electrons transfers electrons to another material with a strong affinity for electrons. The material that sheds electrons develops a positive charge while the material that collects the electrons develops a negative charge. These charges remain in the materials until they contact a conductive path that provides a path back to the original material. If there isn’t a conductive path for the electrons to continually return the built-up electrons to the original material, the built-up electrons will forcefully discharge to a grounded object. Many times this discharge can be felt, heard, or even seen in the form of an electrical arc. When the grounded object is a person who touches the material, this discharge can produce anything from a slight tingling sensation up to a painful shock.
Static electric build-up is intensified in low humidity environments which typically occur seasonally, usually during the winter in many areas. Moisture in the air increases conductivity which provides a conductive path for the displaced electrons to return to the original material, essentially reducing or virtually eliminating the build-up of electrons. Without a build-up of electrons, static electricity charges cannot exist.
When fabrics are dried in a tumbler dryer, the rubbing of the fabrics together as they tumble in the dryer causes fabrics with a strong affinity for electrons to collect electrons from materials with a weaker affinity for electrons. The electrons collected causes a fabric to develop a negative charge while the material that is releasing electrons develops a positive charge. As long as the fabrics retain a sufficient amount of moisture, the moisture provides a conductive path for the electrons to return to the original fabric. A static charge almost never builds up in wet linen but as the fabric dries, the static build-up begins to intensify. The lower the moisture retention in the fabric, the more intense the static charge becomes.
In most cases, static electricity can be easily mitigated through making simple changes to the drying procedures. Here are some easy steps to take to help reduce static electricity that can occur:
Do not over-dry fabrics.
- Once the moisture is gone, the conductive path between the fabrics is gone, trapping the transferred electrons. This causes a negative electrical charge to remain in the fabric which will discharge when a path to ground is provided. Unfortunately, many times that path is the person unloading the dryer. The longer the dryer runs after the fabrics are dry, the stronger the charge will become. Fabrics should never be dried completely and should be left with a slight moisture content. This small amount of moisture will assist in returning the collected electrons back to the original material from which it was collected, helping to eliminate stored static charges.
Do not mix dissimilar fabrics in the dryer.
- Different weights, types, blends, and over all structure of fabrics will dry at different rates and temperatures. Cotton will retain a lot more moisture than a synthetic fabric. The extra retained moisture means cotton will require more time and heat to evaporate the higher volume of moisture. When cotton and synthetic fabrics are mixed in the dryer, the synthetic fabrics will dry far more quickly than the cotton and without the conductive path of the moisture, the completely dry fabrics will begin to build up a static electrical charge while the cotton fabrics are still damp. The longer the dryer runs after the synthetic fabrics are dry, the stronger the charge will become.
- This can also occur when terry and bed linens are mixed. Although the bed linens may contain a percentage of cotton, they will retain much less moisture than 100% cotton and the blends will dry much more quickly than the terry. Continuing to dry the terry while the bed linens are already dry will provide an ideal static generator in the bed linens while the terry finishes drying. The higher the synthetic content in the bed linens, the faster it will dry, leaving even more time to create an even greater charge.
Do not overload the dryers.
- While no damage will occur to a dryer when loaded to capacity, the drying efficiency will be negatively impacted. Dryers work on two main factors: air flow and heat. Heat evaporates the moisture and the airflow moves the moisture out of the dryer through the exhaust vent. Both factors are required to dry fabrics efficiently. Heat without airflow will just create a steam bath. Air flow without heat will make for an extremely slow drying process. Both factors are required for efficient drying. In a dryer, the air is drawn through the burner to heat the air drawn into the dryer. The heated air enters into the top of the dryer which flows around and through the fabrics then out the dryer through the exhaust vent.
- An overloaded dryer reduces airflow contact with the fabrics so that only the outside fabrics in the load dry effectively. The fabric in the middle of the load will take much longer to dry due to very limited contact with the heated air, which due to the density of the center of the load, is mostly flowing around the outside of the load. The outside will dry and begin building a static charge while the inside is still damp. By the time the middle of the load is finally dry, the outside has stored up a significant static charge.
- A simple solution is to reduce the load size in the dryer. Typically, the smaller load size will greatly reduce the drying time which will ensure there is no loss in productivity. In most cases, productivity through the dryers will actually increase with reduced load sizes due to the improvement in drying efficiency.
- Another problem that occurs with overloaded dryers and extended drying time is increased wear to the fabrics. Dry heat along with the friction of the contact between the fabrics tumbling in the dryer breaks down the fibers causing them to wear out prematurely.
Use a good quality fabric softener.
- Most fabric softeners are cationic based surfactants that are oil based. Using a good quality fabric softener can assist in controlling static charges that build up in the fabric. By introducing a liquid fabric softener in the washer, the softener permeates the fabric and assists in providing a conductive path on which the electrons can return to their original material. While one of the main goals of a fabric softener is to replace the naturally occurring oils found in natural fibers that are removed during the wash process, it can also balance the electrons between the fabrics which in turn will greatly reduce or even eliminate static charges.
- The oil based surfactants also provide lubrication to the fabrics which reduces the friction between the fabrics in the dryer and helps limit unwanted static charges. Unfortunately, if the dryer is run too long on too high of a temperature, even the best fabric softener cannot eliminate all static charges.
An excellent choice in fabric softeners is available. Meet the new industry leader in Fabric Softeners, Clax® Deosoft Breeze Conc.
Clax Deosoft Breeze Conc has a special blend of ingredients to help control static electrical charges in the finishing process. Controlling static ensures a more efficient finishing process by eliminating the annoying and painful shocks caused by static electrical charges.
Clax Deosoft Breeze Conc fragrance endures through long drying cycles and long storage times, ensuring fabrics always smell freshly laundered. This superior product is a high performing, concentrated fabric softener that doesn’t just leave a pleasant scent, it neutralizes malodors with patented ONT (Odor Neutralizing Technology). The revolutionary ONT sets Clax Deosoft Breeze Conc above the rest in a class by itself. Multilayered fragrances add a touch of luxury to your fabrics. The Clax Deosoft Breeze fragrance was developed to offer rich scent profiles.
Clax Deosoft Breeze Conc replenishes the naturally occurring oils in natural fibers that are removed during the wash process to help create a luxuriously soft, plush feel. Replacing the oils in the fabric will also extend the life of the fabric, reducing the replacement frequency of the linens.