Semi-crystalline plastic material with great compatibility with injection molding is a rare sight. However, polybutylene terephthalate is an exception. Let’s dive deep into the infamous plastic material.
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 highlight is 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 and quick crystallization upon cooling make 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, medicine, 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 retardant
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, reducing material costs by a good margin.
- It is stress-resistant and has great machining and processing ability.
- It possesses 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 aging behavior
- 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, and greases. That makes it highly suitable for making plastic parts in constant contact with oils and gasoline.
Here are the general properties of PBT material:
|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 are 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 in extremely demanding conditions for particular purposes.
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 mechanical performance.
- The malleability remains consistent till 40 °C yet retains most of its stiffness in the hot car interior. Moreover, specialty graded variations can resist the hard performance need of safety equipment like doors and containers.
- They combine multiple features to achieve a specific task. Malleability, chemical resistance, die-electric strength, and electrical resistance to oils, greases, and gasoline match 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 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 maintain chemical resistance
- PC blends show higher modules support compared to standalone PC
- Adding a minimal amount of polyester can help in improving the 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
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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 both designers and processors tremendous advantages.
- 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 in manufacturing various automobile parts.
Good resistance to extreme environmental resistance also plays a significant role in making PBT suitable for automobile underhood applications.
- Applications for both automobile interior and exterior include:
- Handles and Fans
- Cowl vents
- Fuel system components
- Windsheid wiper covers
- Mirror Housings
- Fuse boxes
- Sensor Housings
- Ignition system components
Electronic and Eletrcical
Leakage and breakdown in power circuitry are huge problems. PBT materials with high electrical resistance and dielectric strength become a guard for electrical and electronic components.
Many parts are specifically made for electrical and electronic components to be used for 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
Fabulous mechanical properties associated with PBT help maintain a subtle image for industrial applications. Short-term mechanical properties like good smack impact, high stiffness, and high strength make 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.
Consumer products have certain conditions for smooth applications. Conditions like high durability, high-temperature resistance, and electrical stresses are necessary for any material.
The most common industrial applications include oven door handles, motor brackets, housings, closure panels, home, and office furniture, etc.
PBT blend with polyester allows strength and rigidness in such parts, likely 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 230° to 270° C.
250-275°F – 2-4 hours
|Maximum continuous service temperature||80-140°C|
|Minimum continuous service temperature||-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 that is must obey:
- Before processing injection molding, pre-dying is extremely 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 evolution in the last few years to make vehicles lightweight and rigid simultaneously. Thus, engineering plastics like PBT will rapidly grow to replace traditional metals like bronze, stainless steel, and iron for various interior and exterior automobile applications.
However, other engineering plastics will compete with PBT for market share. PC is the biggest competitor in the niche market because it has 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.
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Below are the frequently asked questions on PBT polymer. Let’s dig deep to know more.
Is PBT biodegradable?
PBT’s biocompatibility and biodegradability are often compared to PLA and PCL, as these polymers are heavily used in 3D printing. The lack of research on the material is why much can’t be said about its biodegradable properties and attributes.
What is the key difference between PET and PBT?
Both PET and PBT are strong thermoplastic polymers. However, talking about the differences, PBT has slightly lower strength and rigidity, lower glass transition temperature, and moderately better impact resistance. A major similarity between both, however, is both are sensitive to hot water after above 60°C.
How do you make PBT?
PBT creation process is quite similar to thermoplastics. However, it is produced using polycondensation of dimethyl terephthalate with 1,4–butanediol using special catalysts.
Is PBT better than abs?
On paper, PBT is better than ABS in smack resistance, durability, color stability, and maintaining physical presence shine for a longer period. ABS is cheap but less durable, whereas PBT is more expensive.
What are PBT keycaps?
PBT is one of the most sought-after plastic materials for making keycaps. They hold up well with time and are also used in gaming setups. PBT is probably the most durable material used for manufacturing keycaps.
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 top-quality products for your customers. Thermoplastic material has numerous applications in various industries. Thus, no manufacturer should give utilizing PBT’s exceptional abilities.
I hope you liked my piece. Kindly comment on your thoughts and reviews in the comment box.