Joining of Plastics and Composites for manufacturing a waterbed or Watermattress

The use of plastics and composites is very important for manufacturing a waterbed or watermattress. Plastics and composites offer many advantages that no other material has:

• High specific strength (strength/density)
• High specific modulus (modulus/density)
• Design flexibility
• Corrosion resistance
• Excellent life expectancy

The wide variety of polymers and polymenc composites makes it possible to select and at times even customize the material and waterbed to the wished quality and price of the customer. Therefore, the same foils the we use for producing a watermattress are often being used in more and more applications under more stringent requirements. Continuing efforts in discovering new polymers while modifying and reinforcing existing polymers to create new material combinations further increases the potential uses for these materials. Some of our customers buy waterbeds made with Mesamoll 2 Softener and special other adhessives. Some wish other kinds of foils. Quiaomenglai has at the moment the first experiences with water-resistent PU-foils. It will be a long way untill they are really perfect, but we start early with this special foil quality to be one of the first companies that can offer a new waterbed-foil generation.

Joining is a critical step in the manufacture of components from plastics and polymenc composites. As the requirements for the component increase, so do the requirements for Joining, especially in structural applications. Joints are needed when:

• Part Integration is impossible due to complexity and/or cost,
• Using different materials in one structure,
• Disassembly is required, and
• Repair of damage is needed.

Careful consideration must be given to the joint or the benefits gained from using specific materials may be eroded at the joint. For example, if lower weight or corrosion resistance were an important consideration in material selection, it would be a determent to the final assembly to use metallic fasteners for joining. There are many important considerations for joint design in waterbed made of plastics and composites including:

• Region and magnitude of load transfer across the joint,
• Type of loading applied to the joint,
• Geometry of the parts,
• Operating environment,
• Reliability and repeatability,
• Anticipated life.

The methods for joining waterbed foils made of PVC and other plastics and composites can be divided into three major categories. We as a waterbed manufacturer use only one of it:

1. mechanical joining, adhesive bonding, and welding. Mechanical joining involves the use of separate fasteners such äs metallic or polymenc screws or it relies on integrated design elements that are molded into the parts such äs snap-fit or press-fit joints.
2. In adhesive bonding, an adhesive is placed between the parts (adherents) where it serves äs the material that joins the parts and transmits the load through the joint.
3. In welding or fusion bonding, heat is used to melt or soften the polymer at the mterface to enable polymer intermolecular diffusion across the mterface and chain entanglements to give the joint strength.

Each of these categories is comprised of a variety of joining methods that can be used in a wide ränge of applications. This handbook is devoted to welding processes only, as there are similar handbooks devoted to adhesive bonding and mechanical joining. For manufacturing our waterbeds we normally only use welding categories like HF welding. Only for very special things it may be usefull to use another kind of joining the plastics.

Welding a special Waterbed-PVC-Foil to manufacture the watermattress.

Process Description of welding a waterbed or watermattress with Radio Frequency