Hello and welcome to another interesting class of high-performance polymers: Polyphenylenes.
Poly-para-phenylene (PPP), a self-reinforced polymer, is a fascinating material with exceptional properties and potential applications. This polymer was first developed by Maxdem (California, USA) and market as Parmax SRP. Mississippi Polymer Technologies (MPT) acquired the technology in 2000 and then Solvay (now: Syensqo) bought it from MPT.
Generally, self-reinforced polymers or plastics (SRPs) are thermoplastic composites made using the same material for the matrix and the reinforcement.
Chemistry and Production Process
PPP is an amorphous polymer composed of repeating para-phenylene units, forming a rigid, rod-like structure. Its synthesis is challenging due to the high reactivity of the monomers and the insolubility of the resulting polymer. Figure 1 shows the chemical structure of the PPP rigid rod polymer.
One modern way of production method is the Suzuki polycondensation-thermal aromatization methodology, where a continuous sequence of Suzuki couplings occurs between the monomers to form a polymer. This method allows for the controlled polymerization of para-phenylene units.
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| Figure 1: Chemical structure of Poly-para-phenylene (PPP) [4]. |
Main Properties
The backbone structure's repeating aromatic phenyl rings give PPP its exceptional strength; it has been specifically identified as one of the toughest unreinforced polymers on the market. PPP offers a number of advantageous qualities in addition to its high strength, including shape-memory properties, scratch resistance, thermal stability, and biocompatibility.
PPP exhibits remarkable properties:
- High Thermal Stability: It possesses exceptional thermal stability, withstanding high temperatures without degradation. The glass transition temperature of PPP is 158°C and the heat deflection temperature (HDT @ 1.8 MPa) is 154°C.
- High Mechanical Strength: PPP exhibits exceptional mechanical strength, making it one of the stiffest and hardest thermoplastics without adding reinforcement fibers. Figure 2 compares the tensile strength and tensile modulus of PPP (PR-120 = extrusion grade; PR-250 = injection moulding grade) to PEEK, PAI, and PBI. PrimoSpire PR-120 has a tensile strength of 207 MPa and a tensile modulus of 8.3 GPa, which is twice as high as PEEK and PAI. The flexural modulus of PR-120 is with 8.3 GPa also extremely high.
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| Figure 2: Tensile strength and modulus of PPP vs PEEK, PAI, and PBI [6]. |
- Chemical Resistance: It is resistant to a wide range of chemicals, including acids, bases, and solvents. Furthermore, it is resistant to steam sterilization and is x-ray transparent. PPPs can be used as coatings in the chemical process industry and semiconductor wafer handling equipment.
- Self-Lubricating: PPP has self-lubricating properties, reducing friction and wear.
- Low coefficient of thermal expansion: PPP is a quasi-isotropic material which has high strength values in almost all directions.
- Flame Retardancy: It is inherently flame-retardant, making it suitable for applications in fire-prone environments.
- Metal replacement: Not only are PPPs suitable to replace different metal applications, but also fiber-reinforced plastics.
Processing Methods
Due to its high melting point and insolubility, PPP requires specialized processing techniques:
Injection Moulding: High-temperature injection moulding is used to shape poly-para-phenylene-copolymers (PR-250) into complex components.
Extrusion: Extrusion processes, such as profile extrusion and film extrusion, are employed to produce various poly-para-phenylene-copolymers (PR-120) products.
Machining: PPP can be machined using conventional machining techniques, although specialized tooling may be required.
Applications
PPP's unique combination of properties makes it suitable for various applications:
- Aerospace: Components in aircraft and spacecraft, such as engine parts and structural elements. Using PPP will save weight since no reinforcements need to be added and density can be kept at 1.19 g/cm3 (glass-fiber reinforced engineering plastics have a density of typically 1.3 g/cm3).
- Automotive: High-performance components in racing cars and other automotive applications.
- Electronics: Heat sinks, electrical connectors, and other electronic components.
- Medical Devices: Medical devices such as surgical instruments; PPP is able to obtain biocompatibility approvals.
- Industrial Machinery: Gears, bearings, and other components subjected to high stress and wear.
Trade Names and Economic Aspects
PPP is commercially available under various trade names, including:
- Tecamax SRP (Ensinger)
- PrimoSpire SRP (Syensqo)
- Parmax (Mississippi Polymer Technologies; technology owned by Solvay; now Syensqo)
While PPP offers significant advantages, its high production cost limits its widespread use. However, as demand for high-performance materials grows, the economics of PPP production may become more favorable.
Conclusion
Poly-para-phenylene (PPP) is a remarkable polymer with exceptional properties and potential applications. Its high thermal stability, mechanical strength, chemical resistance, and self-lubricating properties make it a valuable material for demanding applications. As production techniques and demand for high-performance materials continue to evolve, PPP is poised to play an increasingly important role in various industries.
Check out my High Performance Thermoplastics selection series here:
Introduction to High Performance Polymers (Part 1)
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Literature:
[1] https://www.aimspress.com/article/doi/10.3934/matersci.2018.2.301?viewType=HTML
[2] https://pubs.rsc.org/en/content/articlelanding/2020/py/d0py00001a/unauth
[3] https://www.matweb.com/search/datasheettext.aspx?matid=67959
[4] https://www.sciencedirect.com/topics/engineering/reinforced-polymer
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