Which Thermoplastic Materials Can Be Welded?

Thermoplastic materials refer to the plastic materials that become pliable when heated above a specific temperature and then harden upon cooling. Thermoplastic welding is the process of joining pieces of thermoplastic material using a combination of heating, pressure, and cooling. The surface of the thermoplastic material is first heated to its melting point, where it enters its thermoplastic state. Each material has its own thermoplastic state, and they usually range between 220F (105C) and 380F (193C). Then the material is pressed together until it cools, with the pressure allowing the molecules in the material to bond with the molecules of the other part. 

Why Use Thermoplastic Materials?

Using Thermoplastic materials is very popular in manufacturing industries because there are so many applications for it. Some of the most common are consumer goods, machine parts, medical equipment, packaging material, and storage material. There are also many benefits to using thermoplastic materials. These benefits include:

  • The materials are lightweight
  • They possess high strength
  • They allow for Design Flexibility
  • There are low processing costs and the materials are more cost efficient
  • Thermoplastic materials have better fatigue properties than metals and are less corrosive

However, not all thermoplastic materials can be welded. Here are some of the most commonly welded thermoplastics, and their applications:

– Polypropylene (PP): Polypropylene coated fabrics are commonly used for a variety of applications in the ducting and packaging industries. It is used in a variety of products ranging from reusable plastic containers to car batteries. It also has medicinal uses, as a way to repair hernias and make heat-resistant medical equipment.

-Polyethylene (PE): Polyethylene has been welded in the agriculture and geomembrane industries for years, but recently the sign industry has begun to use Polyethylene as well. There are a variety of strains of Polyethylene categorized by their density and molecular structure, and all have different applications. The 4 most prominent are ultra-high molecular weight polyethylene (UHMWPE), High-density polyethylene (HDPE), Medium-density polyethylene (MDPE), and Low-density polyethylene (LDPE).

-Polyvinylchloride (PVC): Polyvinylchloride laminated fabric has been a staple in the awning, banner, tent, sign, and ducting industries for years due to its tough but lightweight nature and its resistance to acids and bases. It is also very popular in the construction industry, where it is used in vinyl siding, drain pipes, gutters, and roofing sheets. It can be converted to more flexible forms, which is seen in hoses, tubing, electrical insulation, water beds, and upholstery.

-Polystyrene (PS): Just like PVC, Polystyrene is manufactured in various forms. Extruded Polystyrene (PS) can be found in CD and DVD cases, plastic cars and boats, disposable cutlery and smoke detectors. Expanded polystyrene (EPS) is most prominent in the foam peanuts that are used to pack fragile materials. Extruded Polystyrene foam (XPS), also known as Styrofoam is used in a variety of ways, from architectural models to beverage cups.

-Acrylic: is the shortened name for the polymer poly methyl methacrylate (PMMA), and is known as Lucite, Perspex, and Plexiglass. It is the most prominent substitute for glass and can be found in aquariums, aircraft windows, submersible viewing ports, and automobile lights. It is also used to make signs, including the lettering and logos. PMMA is also used in the medical field, in bone cement and as a replacement for eye lenses. Acrylic is usually heat resistant and can only be welded using a medium, such as thermoplastic seaming tape.

-Nylon: belongs to a class of polymers called polyamides and has served as a substitute for silk in a wide range of products including parachutes and women’s stockings. When in bulk form nylon can be used for mechanical parts, like gear wheels, machine screws and power tool casings. Nylon fibers are often found in fabrics, rope, carpets, and in strings for musical instruments.

-Teflon: is a polymer called polytetrafluoroethylene (PTFE), but is better known by the brand name “Teflon” which was coined by the DuPont Corporation to describe the coating for non-stick cookware. As a polymer, it is chemically inert and is used to make containers and pipes that come into contact with reactive chemicals. Because of this, it is also used as a lubricant in sliding parts to help reduce wear from friction. Only special type of high heat/cooling systems can be used to weld Teflon.

Furthermore, most of these materials can be used in Ultrasonic or RF welding. Other materials such as PET, PETG, Open Celled Polyurethanes, LDPE/EVA, PEVA and some ABS plastics can also be used.
In addition to a wider variety of weldable materials, there are other benefits associated with RF welding. These benefits include:

  • a shorter set time
  • no toxic adhesives
  • an airtight seal
  • evenly distributed stress
  • A tighter seal on thicker materials

In addition, since the heat is only produced at the weld spot there is no heat-degradation of the piece.
If your machine is not as efficient as you would like, your welder may not be the right machine for the job. Our eBook 5 Signs That You May Be Using the Wrong Fabric Welder can help you figure out the answer to this question, and help you find the machine that fits your welding needs.

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