Air bladders are hermetic containers of air in specific configurations. In laymen’s terms, they are devices that are made out of flexible materials such as rolled sheets of films and fabrics that are filled with air. The flexibility of air bladders is important as it allows them to be used in a variety of applications. They are created through a process of radio frequency welding, hot air welding, hot wedge sealing, or solvent bonding services. Injection molding or rotational molding can also be used if the containment vessel (Bladder) needs to be rigid, not flexible or not collapsible.
The design of the air bladder is of utmost importance. In most cases, the medium in the bladder, the application, and the environment in which it is used, will dictate its construction. Common materials that are used in its construction include:
- Polypropylene – This thermoplastic polymer is used for textiles, packaging, laboratory equipment and automotive components.
- Polyethylene – This is the most common thermoplastic polymer because of its many desired features including chemical and abrasion resistance, durability, low moisture absorption low-cost, and non-toxic.
- Nylon – Nylon is often used to coat fabric to make it resistant to mildew and rot. It adds strength, moisture resistance, and durability. It is also easy to clean.
- Olefin – This polymer is often used in electrical insulation sleeves, blown film, athletic equipment and textiles.
- PVC-laminated fabric – PVC is used to add strength, durability and moisture resistance to the fabric.
- PVC-coated fabric – This is a great choice for applications that require added strength, elasticity, and durability of the fabric.
- Cloth-backed vinyl – The cloth backing makes the vinyl easier to handle and manipulate.
- Thermoplastic films – These films are pliable above a certain temperature, but then solidified after they have cooled. They normally have a high molecular weight.
- EVA (Ethyl Vinyl Acetate) – This copolymer of ethylene and vinyl acetate is used in products that require flexibility and durability.
- TPU (thermoplastic polyurethane) – This material is often used in manufacturing. It is often found in foam seating, insulation panels, gaskets, seats, automotive components, synthetic fibers, carpet underlayment, plastic parts, and surface sealant.
- TPE (thermoplastic elastomers) – This copolymer is a combination of plastic and rubber with thermoplastic and elastomer properties. It can easily be manipulated with heat, chemicals, or compression. It is often used in injection molding and can easily be colored and recycled.
It is important to note that each of these materials has its specific strengths and each one works best for specific applications. For example, the most commonly used materials for the creation of air bladders through the RF process are PVC and TPU films. TPU films offer the most elasticity. However, PVC is the most economical. Both varieties come in a variety of thicknesses and colors. Experts like those at AmCraft can help you determine which material is best for your needs.
UV resistance of air bladders
Resistance to Ultraviolet rays is largely reliant on the material from which an air bladder is made. If this issue is necessary for your needs, your best option is to use an air bladder that is constructed from polyethylene since it is resistant to both chemicals and UV rays. Many outdoor playgrounds are made from sheets of HDPE, precisely because it is durable and can stand up to the beating it will take while exposed to the weather elements day after day for many years. Although your air bladder will likely not be constantly exposed to the sun, it is good to know that its material can withstand that kind of punishment.
Chemical resistance of air bladders
Many industries need air bladders that are resistant to chemicals. Not unlike UV rays, this resistance is largely reliant on the materials that are used to make the particular air bladder. Polyethylene is a great material to choose, as not only is it resistant to chemicals, but its other qualities such as low price and durability are favorable to many users. Another material that is chemical resistant is PVC. Not only is it resistant to chemicals, it adds durability and elasticity that are often important qualities an air bladder needs to maintain.
Air introduction and evacuation
The other design aspect that is an important consideration is the introduction and evacuation of air into and out of the devices. The easier and smoother this process is, more effective the air bladder will be.
Advantages of pneumatic air bladders
Air bladders have many advantages for the user. Among the most important include:
- Simplicity of design and control
- No need for make up air to equalize to equalize internal bladder containment pressure
Industries that use air bladders
Common industries that use air bladders include, but are not limited to, the following:
- Aerospace – Air bags are used in the construction of airline seats that can double as flotation devices.
- Shipping – Air bladders are used to fill vacant spaces that might otherwise cause damage to packages during shipping.
- Industrial plants
- Mining – Air bladders add extra tension to roof props ensuring they can handle enough pressure to keep the roof from collapsing.
- Oil industry
- Power Plants -Power plants can send and retrieve compressed air from an underwater air bladder to help supply the necessary power the plant needs.
- Automotives – Lumbar support bladders are often used to make the seats in the automobile more comfortable.
- Medical industry – There are many uses of air bladders throughout the medical field, including therapeutic arm wraps.
- Safety industry – Air bladders are the preferred device for emergency oxygen bags on most commercial aircrafts.
Pressure limitations of air bladders
The concept of using air bladders in many applications is a wise one. It is often the most economical and safest choice. Its efficacy is largely dependent upon the amount of pressure upon the air within the bladder. The pressurized air in most air bladders that are used for industrial applications have a range that extends between 1 and 35 pounds per square inch (psi).
Costs of air bladders
Determining a set price for air bladders is not an easy task. Since air bladders can be used for a multitude of applications, the costs associated with them are highly dependent on their intended use. Air bladders can range in size from compact to enormous, so the amount of material and the type that is needed are factors that are always changing based on the application.
Uses for air bladders
The features and functions of air bladders are many, which makes them a great option for several different applications. Here are just a few of the functions for which air bladders are used.
Air bladders for lifting equipment
Many industries deal with heavy equipment that cannot be lifted by even the strongest humans. When air bladder bags are used as lifting tools, they only need about an inch of clearance under whatever they are lifting. The air bladders can be placed under a specific load that needs to be moved, and when the bladder is inflated, the load moves to wherever it needs to be. This is a great solution for any industry that needs to move extraordinarily heavy objects. Many air bladders can move loads that weigh as much as forty tons. Air bladders are commonly used in emergency rescue situations.
A logical use for air bladders is positioning and securing items during the shipping of items. An air bladder packing system can be helpful in the packing process. The air bladder can be placed in a box between the item being shipped and the wall of the box. The inclusion of the air bladder ensures that the item will not be displaced during shipping.
Air bladders are used in the medical field in a variety of ways, all with great success. Some of the most common medical uses for air bladders include:
- Aiding in the positioning of limbs
- Moving patients into hospital beds, MRI tables, etc.
- Medical heating and cooling of body parts
- Optimizing the pressure contact of pressure temperature wraps
- Blood pressure cuffs
Personal comfort items
One innovative way air bladders are used in increasing personal comfort is in a new type of wheelchair seat. People who have to spend the majority of their day in a wheelchair can attest to the fact that they lose their comfort quickly, as the seat cushion sinks down to nothing with the weight of a human. Seats that have air bladders tucked inside eliminate that problem. The pressure can be adjusted in the bladders to customize the support these seats provide so they can easily conform to each individual’s shape and leave the user feeling comfortable all day.
Flotation devices serve an important need. Without them, it is easy for people and objects to easily sink to the bottom of a body of water. Air bladders are buoyant and therefore make great flotation devices. One air bladder has been designed to help a snowmobile stay afloat. When the air bladder is affixed to the outside of the vehicle, it ensures the vehicle will not sink and occupants can use it as a floatation aid until they can reach solid ice or ground.
Another use for air bladders is as part of the suspension system for a three-wheeled vehicle. The air bladder is designed to work either in conjunction with the existing suspension system or on its own. When it is used in conjunction with an existing system, the weight capacity of the vehicle is increased greatly. The amount of air in the system can also be adjusted by the user to fit personal needs as well as to adjust to differing riding conditions.
These are but a few examples of the many uses of air bladders. Not only are air bladders versatile in their use, they are also versatile in their creation as well. They can be fabricated in just about any size to fit the needs of the end user. Air bladders can be made in almost any size. Regardless of the size that is needed, the internal pressure of the air bladder is a crucial factor and is an issue that should be discussed during the initial stages of design, along with the bladder’s intended use and the environment in which the air bladder will need to function.
Problems with air bladders
Perhaps the most recognized problem that is caused by an air bladder can be seen in the air bags that are installed in automobiles. Although the advent of automobile air bags was a huge step in the right direction in the way of driver and passenger safety, it is not without its flaws. Often car companies recall vehicles because of problems with airbags. Some of the most common pertain to inflation failure or other improper inflation. Since the efficacy of airbags is crucial to the safety of people in cars, manufacturers do everything they can to spread the word about vehicle recalls and replace the defective airbags whenever necessary. However, recall issues are not the only cited problem with the airbags in cars. When airbags were first introduced, it was well known that they were designed for average and above average heighted individuals. Adults who were of smaller stature and children were not only not properly protected by airbags, the deployment of them could actually be harmful to these people. Newer vehicles have airbags that have been tested to assure the protection of people of all heights, but people must still take some appropriate precautions. Older vehicles may still have airbags that are considered unsafe for drivers of smaller stature. Although problems with car airbags is but one example of problems that can occur with air bladders, it shows how air bladders can affect our everyday lives without us realizing it.
Recalls of air bladders
Problems with air bladders can sometimes lead to serious problems that need to be rectified. The best way to accomplish this fix is through a product recall. Since air bladders are so versatile, there are have been recalls of varying types of products including:
- SCUBA equipment/Diving wings
Air bladders are essential to the proper functioning of SCUBA equipment. If the air bladder inside the diving wing breaks, it cannot be used as a buoyancy device, which can be extremely hazardous to a diver. There have been known recalls in certain brands of diving wings.
- Another recall of diving equipment involves the internal weld on an air bladder. It was found to fail during use. When the weld on the bladder fails to work, the flotation device cannot function in its intended use as a flotation device, which can cause undue harm to the diver.
- The Takata recall was one of the largest recalls of automobile airbags. It spanned dozens of brands and affected millions of vehicles in the United States. The recall was the result of defective inflator and propellant devices that caused improper deployment of the airbags. Various entities have cited differing causes of the issue, ranging from rust and bad welds to the presence of foreign substances such as chewing gum in an inflator. Updates to this recall were ongoing as late as December of 2014.
Injection molding or rotational molding can be used to manufacture containment that needs to be rigid. Rigid containment is most likely not classified as a bladder because volume deficit replacement needs to occur to eliminate a negative pressure situation. The larger the containment requirement is, the less viable rigid containment becomes.
SealWerks offers many different options for air bladder fabrication. Our staff can also offer expert advice on the proper material selection to best fit your needs.
Contact us today for your RF Welding product assessment.