The Many Uses of PBT Plastics

This high-performance plastic is strong, stiff, and easy to engineer

Bottle caps made of PBT

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PBT, or polybutylene terephthalate, is a synthetic, semi-crystalline engineered thermoplastic with similar properties and composition to polyethylene terephthalate (PET). It's part of the polyester group of resins and shares characteristics with other thermoplastic polyesters. It's a high-performance material with high molecular weight and is often characterized as being a strong, stiff, and engineerable plastic. Color variations of PBT range from white to bright colors.

Uses

PBT is present in everyday life and common in electrical, electronic, and automotive components. PBT resin and PBT compound are the two types of products used in various applications. PBT compound comprises various materials that can include PBT resin, fiberglass filing, and additives, while PBT resin includes only the base resin. The material is often used in mineral or glass-filled grades.

For use outdoors and where fire is a concern, additives are included to improve its UV and flammability properties. With these modifications, it's possible for a PBT product to be used in numerous industrial applications.

PBT resin is used to make PBT fiber as well as electronic parts, electrical parts, and auto parts. TV set accessories, motor covers, and motor brushes are examples of the uses of PBT compound. When reinforced, it can be used in switches, sockets, bobbins, and handles. The unfilled version of PBT is present in some brake cable liners and rods.

When a material with high strength, good dimensional stability, resistance to various chemicals, and good insulation is needed, PBT is a preferred choice. The same is true when bearing and wear properties are determining factors. For these reasons, valves, food processing machinery components, wheels, and gears are made from PBT. Its application in food processing components is largely due to its low moisture absorption and its resistance to staining. It also doesn't absorb flavors.

Advantages

The major advantages of PBT are evident in its resistance to solvents and low shrinkage rate when forming. It also has good electrical resistance and because of its fast crystallization is easy to mold. It has excellent heat resistance up to 150 degrees Celcius and a melting point reaching 225 degrees Celcius. The addition of fibers enhances its mechanical and thermal properties, allowing it to withstand higher temperatures. Other notable advantages include:

  • Excellent stain resistance
  • Excellent machining characteristics
  • High strength
  • Toughness
  • Excellent stiffness-to-weight ratio
  • Resistance to environmental changes
  • Excellent machining characteristics
  • Better impact resistance than PET
  • Excellent dimensional stability
  • Blocks UV radiation
  • High electrical insulation properties
  • Good variety of grades available

Disadvantages

PBT has disadvantages that limit its application in some industries, including:

  • Lower strength and rigidity than PET
  • Lower glass transition temperature than PET
  • Prone to warp when glass is used as a filler
  • Doesn't present satisfactory resistance to acids, bases, and hydrocarbons

Future of PBT

Demand for PBT has regained footing after the economic crisis in 2009 caused various industries to lower production of certain materials. With growing populations and innovations in the automotive, electrical, and electronics industries, the use of PBT will steadily increase. This is apparent in the automotive industry, given its increasing need for lighter, more resistant, low-maintenance, and cost-competitive materials.

The use of engineer-grade plastics such as PBT will increase due to issues surrounding corrosion of metals and high costs to minimize that problem. Many designers looking for alternatives to metals are turning to plastic as the solution. A new grade of PBT that offers better results in laser welding has been developed, providing a new solution to welded parts.

Asia-Pacific is the leader in the use of PBT, which hasn't changed even after the economic crisis. In some Asian countries, PBT is mostly used in the electronic and electrical markets, while in North America, Japan, and Europe, PBT is mostly used in the automotive industry. It's believed that by 2020, consumption and production of PBT in Asia will considerably increase compared to Europe and the U.S. This prediction is reinforced by numerous foreign investments in the region and a need for materials at a lower production cost, which is not feasible in many Western countries.