Solution Provider of Medical Biomaterials

The elastic modulus of PEEK pure materials is similar to the elastic modulus of most human bones; blended modified materials or composite materials can be customized through the reinforcement of chopped carbon fiber or continuous carbon fiber to improve the elastic modulus and satisfy the needs of special implant applications. The elastic modulus of human skull is between 2 and 6 GPA, and that of human cortical bone is 18GPa. If stainless steel with a large elastic modulus of 200GPa is used to replace skull and cortical bone, the enormous difference of elastic modulus will form a "stress shield", and stainless steel implants with high elastic modulus will bear the main stress. The fractured bone repaired is exposed to the problem of "bone absorption" due to less stress, which results in osteoporosis and secondary fracture. The elastic modulus of PEEK pure materials is 4GPa, which is suitable for skull, spinal fusion cage, ribs and the like; after modification of carbon fiber blends, pure PEEK can reach the elastic modulus of cortical bone of 18GPa, which is suitable for joints; apart from time, the composite materials of continuous carbon fiber can also reach the elastic modulus (110GPa) similar to that of titanium alloy, which is suitable for fracture bone lamellas. It can not only meet the strength and rigidity of bone lamellas, but lower the elastic modulus of bone lamellas and alleviate the problem of "stress shielding".

PAEK materials are characterized by excellent biocompatibility and in vivo stability, while other polymers, such as polysulfone (PSU) and polybutylene terephthalate (PBT), after test and evaluation in 1990s, were proved to be prone to stress cracking due to the influence of human fat. These polymers were abandoned as a result. PAEK polymers became the most ideal biomaterials for human implantation.

The tensile strength of pure PEEK can be up to 105MPa, and that of pure PEK can be up to 110MPa. The tensile strength of PEEK can be up to 310MPa through blending modification of chopped carbon fiber. The tensile strength of 2300MPa can be obtained in the direction of 0 degree (the direction of carbon fiber arrangement) through the preimpregnating of continuous carbon fiber and PAEK resin into unidirectional tape and then molded into composite material, which exceeds that of all metal implants currently used, offering a basis for replacing all types of metal implants in the future.

Polyaryletherketones(PAEK) have outstanding wear resistance. In many areas, when doing the grinding test with metals, the metal often wears out rather than the polyaryletherketone(PEEK). Compared with ultra-high molecular weight polyethylene(UHMWPE), PEEK only have 1/11 abrasion loss after doing grinding test with cobalt-nickel-molybdenum alloy. In human implantation area, carbon fiber PAEK has properties such as good wear resistance, low friction coefficient, high PV value and high strength, making it the best material to replace metal and ultra-high molecular weight polyethylene (UHMWPE) in artificial joint applications.

Low thermal conductivity is a common feature of almost all polymers. The thermal conductivity of PAEK pure materials is 0.29W／m．K, that of 30% carbon fiber reinforced PAEK is only 0.95W／m．K, and that of human tissue is 0.43W／m．K, which is quite close to PAEK materials. In the application of human body implantation, commonly used metal materials such as stainless steel and titanium alloy are of pretty high thermal conductivity, and the thermal conductivity is between 15 and 16W／m．K. As the heat-transfer capability is much greater than that of human body tissue, after these metal instruments are implanted into human body, the implanted person will feel cold in winter and hot in summer, e.g., cerebral cranium, fracture bone lamella, denture bracket, special-shaped gasket for maxillofacial plastic surgery, joints, etc. As PAEK has thermal conduction properties very close to human tissue, the implanted person will not have foreign body sensation after being implanted with PAEK as a prosthesis.

Polyaryletherketone（PAEK）is one of the most excellent polymers for mechanical fatigue performance. In the industrial field, it has been highly recognized and widely used for making many kind of mechanical parts, such as various types of gears, worms, air compressor valve plate, blades for vacuum pumps, single screw air compressor star-wheels, aviation composite materials, etc. After fatigue test (S-N fatigue curve), we found that the mechanical fatigue performance of PEEK resin can be related to the following factors: 1) Molecular weight; 2) Molecular weight distribution width; 3) Crystallinity; 4) Spherulite size; 5) Aging degree; 6) Geometric configurations of the product. For example, the mechanical fatigue performance of the type 8100G is much better than that of 8800G and the service life of the gears vary greatly. The theoretical principle that causes such a huge difference is that the fatigue fracture of high molecular weight PEEK (8100G or 450G) is a failure process between crystal spherulites, while the fatigue fracture of low molecular weight PEEK (8800G or 150G) is a failure process within crystal spherulites. In medical fields, most PEEK implants have requirements for endurance fatigue, especially bone plates, vertebral body fusion cage, joints, bone nails, etc. PEEK's excellent fatigue performance can bring some advantages to orthopedic implant, such as safety, reliability and long service life.

Polyaryletherketone(PAEK) implants can use various methods such as X-ray, CT, MRI to produce medical image. Metal implants are not suitable for CT imaging and MRI imaging because black shadows will appear near the metal implants. However, the polyaryletherketone(PAEK) implants have high clarity and there are no black shadows near the implants. For the X-ray, PEEK implants can transmit and absorb X-rays. The pure PAEK implant can be completely invisible on the X-ray film, which can help doctors to observe lesions in tissues. If we want to see the PEEK implants, We can use X-ray absorbers to make it as a shadow. Then doctors can observe the growth of human tissues around the PAEK implant. For continuous carbon fiber composite materials, in order to make it clear, a tantalum wire ring can be added during the molding of the composite material.

Polyaryletherketones(PAEK) can be disinfected using high-temperature steam or gamma rays. The material structure of pure PEEK does not change when it is continuously stored under steam at 250 ℃ and 14Bar pressure for 2500 hours. The tensile strength does not decrease but increases from 92MPa to 96MPa. Its essence is that when heated for a long time at 250 ℃, the amorphous structure of PEEK that has not yet been saturated and crystallized undergoes crystallization. Under the steam after 2500 hours, the PEEK has already reached supersaturation (about 35%). And the higher the crystallinity, the higher the tensile strength. Therefore, after 2500 hours in a steam environment, the tensile strength does not decrease but increases instead. Gamma ray radiation can destroy the structural stability of aliphatic polymers, such as ultra-high molecular weight polyethylene (UHMWPE). During the radiation process, the chemical bond is easy to break and produce free radicals that exist for a long time. This can easily lead to chemical crosslinking reactions, affecting the original properties of UHMWPE. Polyaryletherketones have excellent resistance to gamma rays and electron beams due to their aromatic ring structure. Even if free radicals are generated, they can decay and disappear after 20 minutes and it is not similar with polyolefins. In the past 30 years, the research shows that crystal PEEK and amorphous PEEK will indeed undergo some degradation and cross-linking when exposed to 10-50 MGy gamma ray radiation in outer space or under nuclear fusion. But radiation below 10MGy does not have a significant impact on PAEK. The gamma ray disinfection for medical implanted devices is only 25-40KGy, which is 400-250 times smaller, so the gamma ray disinfection dose not affect the performance of PEEK. The following table shows the changes in PEEK performance at a gamma ray dose of 75 KGy and 9 items showed minimal performance changes.
Polyaryletherketones(PAEK) can be disinfected using high-temperature steam or gamma rays. The material structure of pure PEEK does not change when it is continuously stored under steam at 250 ℃ and 14Bar pressure for 2500 hours. The tensile strength does not decrease but increases from 92MPa to 96MPa. Its essence is that when heated for a long time at 250 ℃, the amorphous structure of PEEK that has not yet been saturated and crystallized undergoes crystallization. Under the steam after 2500 hours, the PEEK has already reached supersaturation (about 35%). And the higher the crystallinity, the higher the tensile strength. Therefore, after 2500 hours in a steam environment, the tensile strength does not decrease but increases instead. Gamma ray radiation can destroy the structural stability of aliphatic polymers, such as ultra-high molecular weight polyethylene (UHMWPE). During the radiation process, the chemical bond is easy to break and produce free radicals that exist for a long time. This can easily lead to chemical crosslinking reactions, affecting the original properties of UHMWPE. Polyaryletherketones have excellent resistance to gamma rays and electron beams due to their aromatic ring structure. Even if free radicals are generated, they can decay and disappear after 20 minutes and it is not similar with polyolefins. In the past 30 years, the research shows that crystal PEEK and amorphous PEEK will indeed undergo some degradation and cross-linking when exposed to 10-50 MGy gamma ray radiation in outer space or under nuclear fusion. But radiation below 10MGy does not have a significant impact on PAEK. The gamma ray disinfection for medical implanted devices is only 25-40KGy, which is 400-250 times smaller, so the gamma ray disinfection dose not affect the performance of PEEK. The following table shows the changes in PEEK performance at a gamma ray dose of 75 KGy and 9 items showed minimal performance changes.

PAEK materials can be processed in a variety of ways, and the processing diversity, flexibility, convenience and efficiency thereof are incomparable with other metal materials and implanted polymers. The processing and molding methods of PAEK cover profile extrusion, injection molding, insert injection molding, compression molding, 3D printing of powder, 3D printing of wire, 3D printing of granules, electrostatic spraying, dispersion spraying, monofilament extrusion, pultrusion molding, unidirectional belt laser molding, foam extrusion, foam injection molding, machining, etc.. Printing human ribs with PEEK powder can not only create customized shapes as per the individual size of human body, but control the crystallinity by printing the ambient temperature of cavity of PEEK, thus getting the elastic modulus of human ribs most suitable for human body. The bone lamella for treating fracture is made of composite materials satisfying the high mechanical properties of the bone lamella by molding the unidirectional tape of continuous fiber and carbon fiber; cerebral cranium will continue to grow and develop after the infant's skull is implanted, and the rigidity of the skull material should not be too high. The bending elastic modulus of the skull can be reduced by 3D printing the amorphous PEEK skull bone lamella, thus lowering the internal stress between the PEEK skull and the human brain bones during the infant's growth and development, and achieving the goal of harmonious growth.