PPS vs PEEK the two major stars of special plastics what are their respective advantages

In recent years, the application of special engineering plastics has gradually extended from the previous military and aerospace fields to more and more civilian fields, such as automobiles, equipment manufacturing, high-end consumer goods, etc. Among them, polyphenylene sulfide (PPS) and polyether ether ketone (PEEK) are two special engineering plastics that have developed rapidly and have a wide range of applications.

PEEK is superior to PPS in terms of strength, toughness, and maximum working temperature. In terms of high temperature resistance, PEEK's temperature resistance is about 50°C higher than that of PPS. On the other hand, PPS's relatively obvious cost advantages and better processing performance make its application range wider.

PPS

PPS is a crystalline (crystallinity 55%-65%) white powder polymer with high rigidity and high heat resistance (long-term use temperature is 200℃-220℃, and can withstand high temperatures of 260℃ in the short term). It is a kind of mechanical strength , a resin with excellent rigidity, flame retardancy, chemical resistance, electrical properties, and dimensional stability.

It has excellent wear resistance, creep resistance, flame retardancy and self-extinguishing properties. It still maintains good electrical properties under high temperature and high humidity. It has good fluidity and is easy to form. There are almost no shrinkage cavities during molding. It has good affinity with various inorganic fillers. Its development shortens the difference between standard thermoplastic materials (such as PA, POM, PET...) and advanced engineering plastics.

PPS has the following obvious performance advantages:

（1）Intrinsically flame retardant

Unlike PC and PA, PPS pure resin and its glass fiber/mineral powder-filled composite materials can easily achieve V-0 flame retardancy of V-0@0.8mm or even thinner thickness without adding any flame retardants. level. Although PC and PA are cheaper and have better mechanical strength (especially impact strength) than PPS, the cost of PC and PA composite materials added with halogen-free flame retardant formula (V-0@0.8mm level) is It will rise significantly, and in many cases is even higher than PPS materials with the same mechanical strength.

（2）Ultra high liquidity

In the field of notebook cover applications, this advantage is more obvious than that of PCs. The new generation of ultra-thin notebook front covers (thickness 0.8-1mm) often require flexural modulus as high as 15000 – 17000 MPa (ASTM standard). However, under the pressure of strict cost control in the 3C industry, formulators are often required to choose cheaper glass fiber instead of carbon fiber as reinforcing filler. For PC and its alloys, its poor fluidity determines that the upper limit of glass fiber addition should generally not exceed 40% (the flexural modulus can only reach 10,000 MPa, ASTM standard). In addition to seriously affecting the fluidity of the material and causing processing difficulties, higher addition amounts will also cause problems such as floating fibers on the surface, serious warping, and poor mechanical properties. For semi-crystalline PPS, its very high fluidity can allow the glass fiber filling amount to easily exceed 50%. At the same time, during the high-temperature melt blending and extrusion process, the lower viscosity of PPS compared to PC can make The glass fiber undergoes lower levels of shearing and extrusion, resulting in a longer retained length in the final injection molded product, further increasing the modulus.

（3）Ultra low water absorption

This advantage is mainly for PA. In terms of fluidity, highly filled PA and PPS are comparable; as for mechanical properties, PA composites with the same filling amount are even more advantageous. However, in addition to the limitations of halogen-free flame retardancy, another factor restricting the application of PA is its high water absorption: compared with the water absorption of 0.6%-1% of high-temperature nylon PA6T, the water absorption of PPS of 0.03% is almost negligible. The result is that the product defect rate of PPS products due to water absorption and deformation is much lower than that of PA products under the same conditions.

（4）Unique metallic texture and higher surface hardness

When PPS injection molded parts fall on the table, they will make a very crisp collision sound unique to PPS. Through the combination of a special mold and a reasonable mold temperature, PPS injection molded parts will make a sound similar to the collision of metal when touched by human hands, and their surface will be as smooth as a mirror and have a metallic luster.

PEEK

PEEK is a special engineering plastic with excellent comprehensive properties. It has excellent heat resistance, chemical corrosion resistance, radiation resistance, electrical properties, flame retardant properties, etc. Its molecular chain is a polymer composed of benzene rings and connected ketone and ether groups. The benzene ring ensures that the PEEK material has good rigidity, and the ether bonds ensure that PEEK has good toughness. Therefore, PEEK is a comprehensive material with both toughness and rigidity.

PEEK has the following outstanding properties:

(1) Extremely high heat resistance.

It can be used for a long time at 250°C, the instantaneous use temperature can reach 300°C, and it hardly decomposes in a short time at 400°C.

(2) Excellent mechanical properties and dimensional stability.

PEEK can maintain high strength at high temperatures. The bending strength at 200°C can still reach 24 MPa, and the bending strength and compressive strength at 250°C can reach 12 to 13 MPa. It is especially suitable for manufacturing products that can continue to operate at high temperatures. Building blocks of work. PEEK has high rigidity, good dimensional stability and small linear expansion coefficient, which is very close to metal aluminum. In addition, PEEK also has good creep resistance and can withstand great stress during its service life without significant extension over time.

(3)Excellent chemical resistance.

PEEK is well resistant to corrosion by most chemicals even at high temperatures, and its corrosion resistance is similar to that of nickel steel. Under normal circumstances the only thing that can dissolve PEEK is concentrated sulfuric acid.

(4)Good hydrolysis resistance.

PEEK resists chemical damage from water or high-pressure steam. Under high temperature and high pressure conditions, PEEK components can continue to work in a water environment while still maintaining good mechanical properties. If it is continuously soaked in water at 100°C for 200 days, the strength will remain almost unchanged.

(5)Good flame retardant properties.

It can reach UL 94 V-0 level, is self-extinguishing, and releases less smoke and toxic gases under flame conditions.

(6)Good electrical performance.

PEEK maintains electrical properties over a wide frequency and temperature range.

(7)Strong radiation resistance.

PEEK has a very stable chemical structure, and PEEK parts can work normally under high doses of ionizing radiation.

(8)Good toughness.

The fatigue resistance to alternating stress is the most outstanding among all plastics and is comparable to alloy materials.

(9)Excellent friction and wear resistance.

It can maintain high wear resistance and low friction coefficient at 250°C.

(10)Good processing performance.

Easy to extrusion and injection molding, and high molding efficiency.

QINGDAO PRIME TRADE CO., LTD is a company with more than 20 years of experience that specializes in distributing international brand engineering plastic particles. It mainly represents: CHIMEI ABS, HANWHA TOTAL PP, SABIC PPO, and PC special materials. We also have our own modification processing factory, Qingdao Primetech Plastic Co., Ltd., with a professional technical team to provide you with fast and professional services to meet the needs of customers at different levels.