What is PBT Plastics? (Polybutylene terephthalate)

Posted by Laird Plastics on 3rd Feb 2022

WHAT IS PBT PLASTIC?

Companies across the planet continue to look for ways to innovate and save money. One way of doing this is to use materials and components that weigh and cost less. This is where PBT comes into play.

You can find PBT used in a variety of industries, including electronics and automotive. Most applications that call for high-end engineering will likely use PBT components. Aside from cost and weight, however, there are other benefits to using PBT.

Let’s explore these benefits and why many manufacturers choose to use PBT over other materials. We will also discuss the properties of PBT so you can see the benefits that it brings to the table.

PBT: What Is It?

PBT, or Polybutylene terephthalate, is a semi-crystalline thermoplastic compound used for engineering purposes. It possesses a composition and properties that are similar to that of PET (Polyethylene Terephthalate).

Moreover, PBT is in the polyester polymer family. This material is formed by a process called polycondensation, which uses terephthalic acid. It can also be formed using dimethyl terephthalate and 1,4-butanediol. However, this method requires production under a special catalyst.

In addition, polybutylene terephthalate increasingly finds commercial success due to its benefits. For example, PBT has significant use in electrical applications, as well as the automotive, electronic, and medical fields, among others.

The product lines of PBT include various grades that are very suitable for processes like injection molding.

These grades include:

● Impact Correction

● Enhanced Filling

● Non-Flammable

When compared with non-reinforced resins, the tensile, flexural, and compressive strength and modulus of PBT that’s been glass-reinforced are increased by two to three times.

Moreover, grades of unfilled PBT have a vast range of melting viscosity. This aids in providing greater processing freedoms for extrusion technology and injection molding. This includes PBT fibers that are melt-blown and the production of fiber optic tubes, rods, slab, and brake cable linings, for example.

PBT with flame-retardant properties, as well as lubricated PBT variants, can also be purchased in either unreinforced or reinforced grades. When compared with non-reinforced resins, the compressive strength, tensile, flexural range, and modulus of grades that are glass-reinforced are increased by two to three times.

What’s more, PBT’s widespread use is reflected in several regulatory approvals at various levels. These approvals include VDE and UL for markets in the electrical and electronic industries or FDA approvals for the medical and nutrition markets. Such approvals make it clear that PBT is a reliable material.

PBT Properties

The polymer shows excellent mechanical and electrical properties, as well as:

● PBT provides excellent mechanical properties for short-term use, including toughness, high strength, stiffness, and impact

● PBT has commendable dimensional stability creep resistance and limited moisture absorption

● PBT can effectively use materials to reduce both cost and weight

● Superior machining characteristics

● Outstanding stain resistance

● It has good durability under thermal stress and/or harsh chemical environment, especially under the hood of a car

● The high heat distortion temperature and high-temperature index grade of PBT help components withstand short-term thermal excursions and long-term thermal exposure

● Good creep resistance at stable and elevated temperatures

● Good resistance to ultraviolet radiation and excellent thermal aging performance

● Comply with the approvals of many agencies and regulatory agencies for food, medical, and drinking water applications, as well as professional performance specifications

● Polybutylene terephthalate helps protect electrical and electronic components, has extremely high resistance and high dielectric strength, and can prevent leakage and breakdown in power circuits

● Low dielectric loss minimizes energy absorption in high-frequency electronic applications

● If necessary, an appropriate flame retardant grade can be provided

As you can see, PBT has a lot of essential properties and qualities that manufacturers will want to take notice of and use in the production of various components and products.

There are, however, some limitations to PBT that are worth mentioning. For starters, its mold shrinkage is quite high. This means that if you manufacture injection-molded parts, there’s a good chance that they will lose their shape and shrink over time.

Moreover, PBT is very sensitive when exposed to hot water. There’s also differential shrinkage that you need to be aware of, as well as notch sensitivity.

The good news is that PBT is resistant to a wide range of chemicals. This is a very important property for companies that produce electronic and automotive equipment or parts. Resistance includes chemicals like:

● Aromatic hydrocarbons

● Diluted acids

● Solvents

● Alcohols

● Ketones

● Greases

● Oils

If you need to make a plastic component that is going to be exposed to any of the above chemicals, PBT may very well be the best material for your needs. Using PBT will ensure longer lasting performance, as well as high performance.

Any interference from heat or chemicals can significantly reduce the quality of your parts’ performance. As such, it is very important that you choose a material that best suits the environment in which it will be functioning.

If necessary, you can always implement fillers or additional reinforcing materials. These will ensure that your parts have stronger composition to withstand more use and wear and tear. Additives such as these would need to go in during the compounding stage of production.

You can always tailor your additives to meet your requirements. But regardless of the additive you use, it’s important to think about any changes it might make to your component. For instance, some can alter the color of your part.

If this isn’t an option for you and your component has to remain its initial color, look into the effects that various chemicals have and determine the best course of action in production.

Is PBT Right for You?

Whether you are a consumer or a business owner, PBT possesses essential qualities that can serve you well in manufacturing. If you are a hobbyist who makes your own parts for various purposes, PBT can provide you with strength and reliability.

It’s important to remember that PBT excels in the right conditions. So it’s necessary to consider the setting that your parts will be used in and make adjustments with additives if needed.