What is PBT Plastic? (Polybutylene Terephthalate)
Polybutylene terephthalate is strong, semi-crystalline engineering thermoplastic material created by the polymerization of butanediol and terephthalic acid. It belongs to the polyester family of polymers and has characteristics similar to PET(polyethene terephthalate). The major being the number of methylene units present in a repeating form.
PBT( 220 to 225°C) possesses a lower melting point than PET( 250 to 255°C).
The smooth flow of molten material couple with quick crystallization upon cooling makes it highly compatible with injection molding for producing solid components.
Polybutylene Terephthalate is quite popular among mainstream plastic manufacturers thanks to its wide array of applications in automobiles, medical, electronics, etc.
Here’s the list of top PBT suppliers:
PBT products exhibit a wide array of grades highly compatible with Injection molding. These includes:
- Impact modified
- Flame retardent
The unfilled PBT grades have a wide range of thickness that helps them provide processing support in injection molding and extrusion techniques.
Flame retardant PBT plastic is also available in the market, and not just that, lubricated Polybutylene Terephthalate versions are also available in both unreinforced and reinforced grades.
Properties of PBT –
- It has high material handling capabilities which will reduce material cost by a good margin.
- It is stress-resistant and has great machining and processing ability.
- It posses nine sets of short-term mechanical properties like High-strength, toughness, and stiffness.
- It has impressive creep resistance, moisture absorption, and excellent dimensional stability.
- Polybutylene Terephthalate helps in protecting electrical components with high electric resistance.
- Appropriate flame-resistant grades are also available in specific cases.
- Good UV blocking coupled with good heat ageing behaviour
- PBT material has high heat deflection temperatures and a high-temperature index, which helps resist short-term thermal excursion and longer-term heat exposure.
- Decent durability in tough chemical environments, especially in automobile underhood applications.
- Fantastic chemical resistance against chemicals like alcohols, aromatic hydrocarbons, ketones, diluted acids, oils, solvents, greases. That makes it highly suitable for making plastic parts in constant contact with oils and gasoline.
Here are the typical properties of PBT materials:
|Greases and Oils||Good|
|Tensile Strenght (MPa)||50|
|Elongation at break ( % )||250|
|Tensile Modulus (GPa)||2|
|Izod impact strength ( J.m-1 )||60|
|Dielectric strength ( kV.mm-1 )||20|
|Dielectric constant @ 1 kHz||3.2|
|Dissipation factor @ 1 kHz||0.002|
|Volume resistivity ( Ohm.cm )||10 raise 15|
|Heat-deflection temperature – 1.8 MPa ( °C )||60|
|Heat-deflection temperature – 0.45 MPa ( °C )||150|
|Upper working temperature ( °C )||120-?|
|Density ( g.cm-3 )||1.31|
|Limiting oxygen index ( % )||25|
|Water absorption – over 24 hours ( % )||0.1|
Limitations of PBT –
- Strength and rigidness lower than PET
- Glass resistance temperature is also lower than PET.
- Poor resistance to hydrolysis
- Warping is evident because of constant differential shrinkage.
- High mold shrinkage
Polybutylene Terephthalate Alloys and its Blends –
Polybutylene Terephthalate alloys have various blends used for particular purposes in extremely demanding conditions.
The blend is mostly formed with PC and PET materials and gives various advantages for certain engineering applications.
It highlights the strengths and overshadows the limitations, thereby achieving top-notch results in high-end and complex applications.
Here are certain benefits:
- Delivering robust engineering properties in a malleable, chemically resistant material. Providing designers with the freedom and ability they require to give robust results without trading off between mechanical performance.
- The malleability remains consistent till-40°C yet retains most of its stiffness in the hot car interior. Moreover, specialty graded variations are capable of resisting the hard performance need of safety equipment like doors and containers.
- Combining multiple features to achieve a specific task. Malleability, chemical resistance, die-electric strength, and electrical resistance to oils, greases, and gasoline matching the heat shock criteria.
- Variants with weatherable grades are useful in outdoor electrical applications.
Polycarbonate/Polybutylene Terephthalate (PC/PBT) Blend:
Polycarbonate and PBT material have many similarities, but the major similarities are tensile strength and flexibility.
Both the materials complement each other. In the PC and PBT blend:
- Polycarbonate helps in balancing resistance capabilities with impact, stiffness, and heat. On the other hand
- Polybutylene Terephthalate helps in maintaining chemical resistance
- PC blends show higher modules support compared to standalone PC
- Adding a minimal amount of polyester can help in improving PC’s flexibility
- Other PC/Polyester blends have better mixing abilities compared to PC/PBT blends
Let’s have a look at the strengths and the drawbacks of the blend:
|Impressive heat resistance – up to 140°C||
Not compatible with thin wall design because f its medium flow properties
|Fantastic weatherability||High Shrinkage|
|Good UV resistance||Opaque|
|Good color retention||
Shows weakness towards esters, ketones, alkalis, and halogenated hydrocarbons
Excellent toughness – upto -40°C
Applications of PBT Plastic –
PBT offers applications in various industries thanks to its versatile nature and excellent physical properties. The vast range of valuable properties gives tremendous advantages to both designers and processors.
- Industrial Applications
- Electronics and Electrical
- Consumer Goods
PBT’s supreme set of mechanical and electrical properties, suited wonderfully by decent thermal stability and excellent chemical resistance, makes it more than qualified enough to be used manufacturing various automobile parts.
Good resistance to harsh environmental resistance also plays a significant role in making PBT suitable for automobile underhood applications.
- Applications for both automobile interior and exterior includes:
- Handles and Fans
- Cowl vents
- Fuel system components
- Windsheid wiper covers
- Mirror Housings
- Fuse boxes
- Sensor Housings
- Ignition system components
#2 Electronic and Eletrcical:
Leakage and breakdown in power circuitry is a huge problem. PBT materials with high electrical resistance and dielectric strength become a guard for electrical and electronics components.
Many parts are specifically made for electrical and electronic components to be used in their power and signal purposes. There are products like:
- Power sockets made for modular building panels
- Connectors, sensor housings, chip sockets
- Transformer insulation
- Terminal Boards
- Cable Liners
- Fiber optic buffer tubes
- Switches and Circuit breakers
#3 Industrial Applications:
Fabulous mechanical properties associated with PBT helps in maintaining a subtle image for industrial applications. A good set of short-term mechanical properties like good smack impact, high stiffness, and high strength makes Polybutylene Terephthalate well-versed for tough and rigid industrial applications.
The most common applications include street lamp reflectors, pump housings, fluorescent lamp bases, monofilaments, filter media, and packaging components. Mixing alloys with PBT can improve the scope of industrial applications by a large margin.
PBT alloys can produce small off-rode file tanks, tractor hoods, panels, power tool housings, and conveyer chain components with the added dimension of greater toughness.
#4 Consumer Goods:
Consumer products have certain conditions for smooth applications. Conditions like high durability, high-temperature resistance, and electrical stresses are a must for any material.
The most common industrial applications include oven door handles, motor brackets, housings, closure panels, home, office furniture, etc.
PBT blend with polyester allows strength and rigidness in such parts, which are likely to be rough contact like closure and kick panels, lids, covers, seatbacks, and bottoms.
Processing of PBT –
All the PBT grades and variations are mainly processed in injection molding at having a temperature ranging from 230° to 270° C.
250-275°F – 2-4 hours
|Maximum continous ervice temprature||80-140°C|
|Minimum continous service temprature||-40°C|
|L/D Screw ratio||20:1|
|HDT – 0.46MPa||115 to 150°C|
|HDT – 1.8 MPa||50-85°C|
|Brittle transition temperature||-40°C|
- There are certain conditions during and before processing which is must obey:
- Before processing injection molding, pre dying is extreme;y important to control moisture content – 0.02%
- Mold shrinkage – Higher the model temperature, the higher the shrinkage – Unfilled: 1.4-2.0%, Glass-fiber Reinforced: 0.4-0.6%
- Injection pressure – 100-140 MPa
- A graded three-zone screw needs to be used.
The Future of PBT Material –
The pre-pandemic growth forecast for OBT was a CAGR of 5%. The demand is witnessing positive growth in the automobile and electronics industries.
The automobile industry has seen rapid evolvement in the last few years to make vehicles lightweight and rigid at the same time. Thus, engineering plastics like PBT will see a rapid growth replacing traditional metals like bronze, stainless, steel, and iron for various interior and exterior applications in automobiles.
However, other engineering plastics will stand toe to toe with PBT for market share. PC is the biggest competitor in the niche market because of its having similar properties. Bio-based PBT is also in the development stages. That can also propel growth on a long-term basis.
Asia-pacific is said to lead other regions in terms of the amount of PBT consumed by the manufacturing sector. Countries like China, Vietnam, India, and Bangladesh have witnessed rapid growth in their manufacturing sector, showing a bright future for engineering plastics, let alone PBT.
Interesting Read – Compression Molding Process – A Detailed Guide | Thermosets Composite Compression Molding | Types of Compression Molding | Molds Used for Compression Molding | Advantages | Disadvantages | Applications
#1 What is PBT used for?
Ans. PBT plastic is often used in industrial applications, automobiles, consumer goods, electronics, and electrical. There are several products for various uses which are produced using engineering plastic.
#2 What does PBT stand for?
Ans. It stands for Polybutylene Terephthalate.
#3 How do you make PBT?
Ans. PBT creation process is quite similar to thermoplastics. However, it is produced using polycondensation of dimethyl terephthalate with 1,4–butanediol using special catalysts.
#4 Is PBT better than abs?
Ans. On paper, PBT is better than ABS in smack resistance, durability, color stability, and maintaining physical presence shine for a longer period of time.
#5 What is PBT resin?
Ans. Polybutylene Terephthalate, better known as PBT, is one of the strongest and most resilient engineering plastic with a semi-crystalline structure. The range of applications is noteworthy as it has a set of phenomenon mechanical and physical properties. Thanks to all that, it is one of the most sought-after thermoplastic resins by plastic manufacturers.
The Takeaway –
So, that was all from my side. I have shared everything I knew about PBT plastic. PBT plastic is a must for your shop floor to provide supreme quality products for your customers.
I hope you liked my piece. Kindly comment on your thoughts and reviews in the comment box.