Test Method

There are various evaluation test methods for sliding characteristics. The appropriate method depends on the application and situation. Devices for evaluating the basic sliding characteristics of resin include a Suzuki wear tester, Pin-on-Disk wear tester, and thrust wear tester (Amsler, etc.).

Limiting PV Value

The limiting PV value (Load pressure × Velocity) represents the limit at which the sliding surface of the material becomes deformed or melts due to frictional heat generation. Therefore, when conditions exceed the limiting PV value, both friction and wear will increase significantly, making it unusable. The limiting PV value increases as the resin heat resistance increases. It is necessary to use it at about 50 to 60% or lower than the limiting PV value.

Frictional Properties

Frictional properties are indicated by the static friction coefficient (μ_S) and dynamic friction coefficient (μ_D). Fluororesin-based sliding materials are said to have the smallest friction coefficient.
The frictional resistance at startup is represented by μ_S. It is important that the μ_S be small and stable for applications where it repeatedly changes from static to movement. The μ_S immediately after molding and μ_S after initial wear are different.

Sliding Characteristics of Non-Reinforced Sliding Grades

Non-reinforced sliding grades that do not contain reinforcing fibers include SUMIPLOY E3010 and SUMIPLOY FS2200. These have a feature making it extremely difficult to damage the mating material in a dry state even when the mating material is a soft metal such as SUS or aluminum.

Limiting PV value

Figure 3-7-1 shows the velocity dependence of the limit PV values for E3010 and FS2200 compared with other engineering plastic sliding grades. This indicates that it has a limit PV value that is considerably higher than the compared sliding materials.

Figure 3-7-1 Velocity Dependence of Limiting PV Values for Non-Reinforced Sliding Grades

Frictional Properties

E3010 shows the smallest static friction coefficient in the dry state among sliding materials for injection molding. E3010 maintains its initial static friction coefficient even after wear and is stable over a long period of time.

Wear Properties

Table 3-7-1 shows the friction and wear properties of SUMIPLOY sliding grades in comparison with the sliding grades of other general-purpose engineering plastics. It shows stable wear resistance for low to high PV values. Figure 3-7-2 shows the relationship between the amount of wear and time for E3010 when P = 0.6MPa and V = 40m/min. The initial wear is smaller than that of fluororesins containing filler. It is also equivalent to fluororesins containing polyimide.

Table 3-7-1 Friction and Wear Properties of Non-Reinforced Sliding Grades (Thrust Type Testing Machine)

Measuring conditions			Sample	Dynamic friction coefficient μD	Cumulative friction amount ΔW (μ)	Wear coefficient K (mm/km-MPa)	Wear of mating material (mg)
Pressure P (MPa)	Speed V (m/min)	Mating material
1	10	SUS304	E3010	0.16	3.5	1.2×10-6	Transfer
			FS2200	0.12-0.30	11	3.8×10-6	0.27
			PTFE-filled PC	0.12-0.31	95	33.3×10-6	0.13
			PTFE-filled POM	0.13	8.7	3.0×10-6	0.10
0.6	40	SUS304	E3010	0.18	11	1.6×10-6	0.01
			FS2200	0.14-0.21	133	19.2×10-6	0.16
			CF/PTFE filled PPS	0.40	132	19.2×10-6	13.6
			PTFE-filled PC	Above the limiting PV value (melting within a few minutes)
			PTFE-filled POM
0.1	100	SKH-2	E3010	0.24	5.7	2.0×10-6	0.16
			FS2200	0.29	85	29.5×10-6	0.14
			CF/PTFE filled PPS	0.81	90	31.3×10-6	10.5
0.2	100	SKH-2	E3010	0.22	5.4	0.9×10-6	0.24
			CF/PTFE filled PPS	0.53	168	29.2×10-6	4.30

Figure 3-7-2 Friction and Wear Properties of Non-Reinforced Sliding Grades

P = 0.6MPa V = 40m/min Mating material: SUS304

Sliding Characteristics of Fiber-Reinforced Sliding Grades

SUMIPLOY CS5220, CS5530, and CK3420 are reinforced grades with carbon fiber, inorganic filler, etc. These have excellent dimensional stability, mechanical strength and rigidity, a small coefficient of thermal expansion, and can even be used under harsh conditions with a high PV value. Although the friction coefficient is relatively large and has slight fluctuation, it can be used for various applications by using a mating metal material with high hardness, by applying a hardening treatment to the surface of the material, or by using it together with lubricating oil. However, keep in mind that these may damage soft metals such as SUS and aluminum.

Limit PV Values for SUMIPLOY Fiber-Reinforced Grades

Table 3-7-2 shows the limiting PV values for SUMIPLOY CK3420, a fiber-reinforced grade.

Table 3-7-2 Limiting PV Values of Fiber-Reinforced Sliding Grades

Unit : MPa-m/min

	CK3420
V=40m/min	160
V=100m/min	100

Mating material : SKH-2, room temperature-DRY

Friction and Wear Properties of SUMIPLOY fiber-Reinforced Grades

The following shows the PV value dependence of the dynamic friction coefficient μD when the velocity is V = 40 m/min, 100 m/min. Each grade shows a small value of 0.1 to 0.2 when the PV value is high (high load), but the friction coefficient is large when the PV value is low (low load). Therefore, it is a good sliding material for high loads and high speeds.
The wear resistance of these fiber reinforced grades is not good compared to non-reinforced sliding grades. Table 3-7-3 shows examples of friction and wear properties.