A pneumatic radial tire with low rolling resistance and high wet grip

Abstract

This invention provides a low rolling resistance and high wet grip pneumatic radial tire, belonging to the field of tire technology. It includes a tread and circumferential grooves extending along the circumference of the tread. The contour from the highest point of the tread to one end point on one side of the tread is sequentially divided into a first arc, a second arc, a third arc, and a fourth arc. The radii TR1, TR2, TR3, and TR4 of the first arc satisfy the following relationship: TR1:TR2:TR3:TR4 = 2.3:1.9:1.6:1. Five circumferential grooves are provided, each consisting of a central teardrop-shaped groove, two grooves near the central groove, and two shoulder teardrop-shaped grooves extending from the center of the tread to both sides. The central teardrop-shaped groove and the shoulder teardrop-shaped grooves are self-closing grooves under load. This invention optimizes tire structure design, tread pattern design, and compound design to achieve extreme durability while maintaining low rolling resistance and high wet grip performance throughout the tire's lifespan.

Description

Technical Field

[0001] This invention relates to the field of tire technology, and specifically to a pneumatic radial tire with low rolling resistance and high wet grip. Background Technology

[0002] When tires undergo extreme durability testing, refer to Figure 1 This test typically takes place in a specific location where cars drive along a fixed route in a loop. The route features continuous curves with radii R30–R50. The lateral acceleration experienced by the tires during cornering is required to be 0.6g, and the cornering speed must reach 60–80 km / h. When a car corners under these conditions, the maximum lateral force can reach over 30,000 N (more than 100 times the lateral force experienced during normal driving), easily causing tearing and chipping of the tire shoulder rubber, leading to damage. This test is an extreme durability test designed to evaluate a vehicle's ability to resist lateral forces when driving on a road with multiple consecutive curves. Tires with this durability capability exhibit better crown durability performance than ordinary tires.

[0003] In recent years, with the continuous updates to tire regulations and policies in various countries, the technical requirements for tires have gone beyond the conventional safety, durability, and wear life. In addition, the requirements for low rolling resistance and high wet grip have been added. The newly effective EU regulation R117-04 requires not only the wet performance of new tires, but also that tires maintain a certain level of wet performance throughout their entire life cycle.

[0004] Currently, there are no clear technical means to achieve this level of extreme durability in tires. Technologies for reducing tire rolling resistance include: optimizing tire tread pattern design, using low rolling resistance rubber compounds, reducing component thickness, and reducing material usage; technologies for improving wet grip mainly include: using high wet grip rubber compounds and increasing the water storage volume of tread grooves.

[0005] To balance low rolling resistance and high wet grip, common structural techniques in existing tire products often involve reducing the thickness of components. Since the tread is the primary heat-generating component, reducing its thickness (by decreasing rubber usage) can effectively lower rolling resistance. However, this technique results in less rubber material used in the tire crown area. Under extreme lateral forces, the rubber material in the tire shoulder wears rapidly, leading to decreased durability. Another common formulation technique is to use silica formulations with low hysteresis loss and high wet grip. However, these formulations have poor strength, and under extreme lateral forces, the tire shoulder is easily torn apart, further reducing durability.

[0006] Meanwhile, existing high-wet-grip tread designs add more grooves to the tire surface to increase water storage volume and increase tread edge density to improve the ability to puncture a water film. However, if low rolling resistance is also considered, these grooves must be minimized and made as shallow as possible to ensure tread rigidity and inhibit deformation. Shallow grooves wear away in the middle and later stages of tire use, resulting in a significant decrease in wet performance. Therefore, conventional tread designs struggle to balance wet performance and rolling resistance. Summary of the Invention

[0007] This invention provides a pneumatic radial tire with low rolling resistance and high wet grip. By optimizing the tire's structural design, tread pattern design, and compound design, the tire achieves extreme durability while maintaining low rolling resistance and high wet grip performance. In particular, it can also achieve wet grip performance throughout the tire's entire life cycle.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A pneumatic radial tire with low rolling resistance and high wet grip includes a tread and circumferential grooves extending along the circumferential direction of the tread. The contour between the highest point of the tread and the endpoint on one side of the tread is sequentially divided into a first arc, a second arc, a third arc, and a fourth arc. The radii TR1, TR2, TR3, and TR4 of the first arc satisfy the following relationship: TR1:TR2:TR3:TR4 = 2.3:1.9:1.6:1.

[0010] Five circumferential grooves are provided. These five circumferential grooves, arranged sequentially from the center of the tread to both sides, include a central teardrop-shaped groove, two grooves near the central groove, and two shoulder teardrop-shaped grooves. The central and shoulder teardrop-shaped grooves are self-closing grooves under load, while the two grooves near the central groove are open grooves. The depths of the five circumferential grooves are GD1, GD2, GD3, GD4, and GD5, and the widths are GW1, GW2, GW3, GW4, and GW5, respectively, and they satisfy the following relationship:

[0011] GD1=GD2=GD3=GD4=GD5, and GD1 / L=0.045±3%;

[0012] GW1=GW5, GW2=GW4, GW1:GW2:GW3=1.63±3%:3.88±3%:1±3%, and (GW1+GW2+GW3) / L=0.18±3%.

[0013] Preferably, the five circumferential grooves divide the tread into six tread blocks, the widths of the six tread blocks being A, B, C, D, E, and F respectively along the width direction of the tread, and satisfying the following relationship:

[0014] A = F, B = E, C = D;

[0015] The width ratio of the patterned blocks A:B:C = (1.84±3%):(1.45±3%):(1.00±3%);

[0016] C / L = 0.09 ± 3%;

[0017] Where L is the tread arc length along the tire width direction.

[0018] Preferably, the central teardrop-shaped tread groove and the shoulder teardrop-shaped tread groove include, from the outside to the inside, a zigzag groove section, a straight groove section, and a teardrop groove section along the tire radial direction. The maximum width of the zigzag groove section extending along the tread is w1, the width of the straight groove section along the tire axial direction is w2, and the maximum width of the teardrop groove section along the tire axial direction is w3, and they satisfy the following relationship: w1:w2:w3=3.5±3%:1:3±3%.

[0019] Preferably, the angle between the zigzag groove segment extending along the tread and the circumferential centerline of the tread is 8°.

[0020] Preferably, the depth of the straight groove section along the radial direction of the tire is h2, and h2 ≥ 3 mm.

[0021] Preferably, the depth of the water droplet groove section along the radial direction of the tire is h3, and h3 ≥ 4 mm.

[0022] Preferably, the angle between the upper edge of the cavity at the bottom of the water droplet groove section and the horizontal direction is α, and 45°≤α≤75°; the chamfer R at the bottom of the water droplet groove section is ≥2mm.

[0023] Preferably, the tire further includes a tire carcass disposed radially inside the tread and a belt layer located between the tread and the tire carcass, wherein the belt layer includes a first belt layer, a second belt layer, a third belt layer and a fourth belt layer in sequence from the inside to the outside along the radial direction of the tire.

[0024] Preferably, the width of the second belt layer along the tire axial direction is L1, and 90% ≤ L1 / L ≤ 95%, and the angle between the line connecting the midpoint Q of the second belt layer crown and the endpoint P on one side of the second belt layer and the horizontal direction is β, and 3° ≤ β ≤ 7°.

[0025] Preferably, the distance between one end point of the third belt layer and one end point of the tread along the radial direction of the tire is H, and H≥11mm.

[0026] Preferably, the tread includes a crown layer that contacts the ground and a base layer disposed radially inside the crown layer, wherein the maximum thickness of the base layer along the tire radial direction is h1, and h1 = 3 mm.

[0027] Preferably, the rubber compound used in the tread layer has a hysteresis loss tangent of tanδ = 0.098 and a modulus of 5.35 at 60°C and 5% deformation to ensure rolling resistance performance.

[0028] The rubber compound used in the tread layer has a hysteresis loss angle tanδ=0.130 at 0℃ to ensure wet grip performance;

[0029] The tire crown layer has a tensile strength Ts of 29.5 MPa at room temperature and an elongation at break Eb of 523%. Furthermore, below 120°C, the retention rate of Ts*Eb is 60% of that at room temperature.

[0030] Preferably, the adhesive used in the base layer has a hysteresis loss tangent of tanδ = 0.030 at 60°C.

[0031] As can be seen from the above technical solutions, the present invention has the following beneficial effects:

[0032] 1. In this invention, by optimizing tire structure design, tread pattern design, and compound design, the tire achieves ultimate durability while possessing low rolling resistance and high wet grip performance throughout its entire life cycle. Specifically, the tread crown arc adopts a four-segment tangent circular arc design, with the four segments having roughly equal lengths and their radii meeting certain proportional requirements. This ensures uniform overall crown pressure distribution, reducing rolling resistance and also minimizing shoulder pressure concentration, thereby improving ultimate durability. The five tread grooves divide the tread into six tread blocks, designed in a specific proportion to ensure a reasonable rigidity distribution in the crown area, promoting uniform crown wear, improving wear resistance, and simultaneously guaranteeing rolling resistance and ultimate durability. The belt layer adopts a four-layer structure, with the width of the second belt layer meeting a certain proportion to the tread arc length to improve... Increasing the rigidity of the tire shoulder reduces shoulder deformation during extreme durability testing, decreases shoulder pressure concentration, and increases the area involved in wear, thereby improving extreme durability. Simultaneously, the angle between the line connecting the midpoint of the second belt layer crown and one end point of the second belt layer and the horizontal direction satisfies a certain angle, resulting in smaller strain at the belt layer end point during extreme durability testing, which is beneficial for improving extreme durability performance. The groove depth and width ratio of the five tread grooves are set to ensure both drainage performance and rolling resistance. For the teardrop-shaped grooves, the teardrop-shaped cavity at the bottom allows water to drain from the contact patch when the tire is driving in wet conditions, enabling the tire to enter a dry contact state earlier and significantly improving wet performance. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of an extreme durability test;

[0034] Figure 2 This is a schematic diagram of the tire structure provided by the present invention;

[0035] Figure 3 for Figure 2 One of the partial schematic diagrams of the crown portion of the tire;

[0036] Figure 4 This is a schematic diagram of the tire circumferential groove width provided by the present invention;

[0037] Figure 5 for Figure 2 Partial schematic diagram of the crown portion of the tire (part 2);

[0038] Figure 6 This is a schematic diagram of the structure of a teardrop-shaped groove.

[0039] Figure 7 A comparison chart of ground pressure under extreme durability conditions between the tire design provided by this invention and conventional designs.

[0040] In the diagram: 10, tread; 110, crown layer; 120, base layer; 130, central teardrop-shaped tread groove; 140, near the central tread groove; 150, shoulder teardrop-shaped tread groove; 210, zigzag groove section; 220, straight groove section; 230, teardrop groove section; 30, carcass; 40, belt layer; 410, first belt layer; 420, second belt layer; 430, third belt layer; 440, fourth belt layer. Detailed Implementation

[0041] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0042] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: (Refer to...) Figure 2 , Figure 5 A low rolling resistance and high wet grip pneumatic radial tire includes a tread 10, wherein a circumferential groove is provided extending in the circumferential direction of the tread 10. The contour from the highest point of the tread to the end point on one side of the tread is divided into a first arc, a second arc, a third arc, and a fourth arc in sequence, and the radius of the first arc TR1, the radius of the second arc TR2, the radius of the third arc TR3, and the radius of the fourth arc TR4 satisfy the following relationship: TR1:TR2:TR3:TR4=2.3:1.9:1.6:1. According to this crown arc design, the overall crown pressure distribution is uniform, the rolling resistance is reduced, and the shoulder pressure concentration is also reduced, thereby improving the ultimate durability.

[0043] Furthermore, refer to Figure 3 , Figure 4The circumferential grooves are provided in five sections. These five circumferential grooves, extending from the center of the tread 10 to both sides, include a central teardrop-shaped groove 130, two grooves near the central groove 140, and two shoulder teardrop-shaped grooves 150. The central teardrop-shaped groove and the shoulder teardrop-shaped grooves are self-closing grooves under load, while the two grooves near the central groove are open grooves. The depths of the five circumferential grooves are GD1, GD2, GD3, GD4, and GD5, and the widths are GW1, GW2, and GD5, respectively. W3, GW4, and GW5, and satisfying the following relationship: GD1 = GD2 = GD3 = GD4 = GD5, and GD1 / L = 0.045 ± 3%; it should also be noted that GW1 = GW5, GW2 = GW4, and GW1:GW2:GW3 = 1.63 ± 3%: 3.88 ± 3%: 1 ± 3%, (GW1 + GW2 + GW3) / L = 0.18 ± 3%. In this way, the patterned groove designed according to the above proportions has both certain drainage performance and can ensure rolling resistance.

[0044] Reference Figure 3 As a preferred technical solution in this embodiment, the five circumferential grooves divide the tread 10 into six tread blocks. The widths of the six tread blocks along the width direction of the tread 10 are A, B, C, D, E, and F, respectively, and satisfy the following relationship: A = F, B = E, C = D; the width ratio of the six tread blocks is A:B:C = (1.84±3%):(1.45±3%):(1.00±3%); and C / L = 0.09±3%; where L is the tread arc length of the tread 10 along the tire width direction. The tread block width designed according to this ratio makes the crown rigidity distribution reasonable, which is conducive to uniform crown wear, improves wear resistance, and at the same time ensures rolling resistance performance and ultimate durability.

[0045] Furthermore, refer to Figure 6 The central teardrop-shaped tread groove and the shoulder teardrop-shaped tread groove, from the outside to the inside along the tire radial direction, include a zigzag groove section 210, a straight groove section 220, and a teardrop groove section 230, wherein the maximum width of the zigzag groove section extending along the tread is w1, the width of the straight groove section along the tire axial direction is w2, and the maximum width of the teardrop groove section along the tire axial direction is w3, and satisfies the following relationship: w1:w2:w3=3.5±3%:1:3±3%;

[0046] Furthermore, refer to Figure 4 , Figure 6The zigzag groove section 210 has a zigzag angle of 8°. This means that the part of the teardrop-shaped tread groove near the tread is a zigzag groove, and the zigzag angle is preferably 8°. Specifically, this zigzag angle refers to the angle between the bottom of the zigzag groove section 210 (that is, the top of the straight groove section 220) along the extension direction of the tread 10 and the circumferential center line of the tread 10, which can improve the stone removal ability. At the same time, the middle groove of the teardrop-shaped tread groove is a straight groove, which improves the drainage performance. In addition, the lower half of the teardrop groove has a teardrop-shaped cavity. When the tire is driving in wet conditions, water at the contact front can be discharged through this teardrop-shaped cavity, allowing the tire to enter the dry contact state earlier, which greatly improves the tire's wet performance.

[0047] Furthermore, refer to Figure 6 The straight groove section 220 has a radial depth of h2, and h2 ≥ 3mm. This design allows the tread groove to self-close under tire loading, making what were originally two tread blocks approximate a single tread block upon contact with the ground. This significantly reduces tread deformation during driving and effectively lowers rolling resistance. In extreme endurance tests, the self-closing of the teardrop grooves greatly enhances the rigidity of the shoulder tread blocks, reduces shoulder tread deformation, and further improves extreme endurance.

[0048] At the same time, refer to Figure 6 The depth of the water droplet groove section 230 along the radial direction of the tire is h3, and h3≥4mm, which ensures sufficient water storage volume and gives the tire good wet performance.

[0049] Reference Figure 6 In some embodiments, the angle between the upper edge of the cavity at the bottom of the water droplet section 230 and the horizontal direction is α, and 45°≤α≤75°, preferably α is 60°; at the same time, the chamfer R at the bottom of the water droplet section 230 is ≥2mm. The water droplet designed in this way can ensure sufficient wetland performance, reduce stress concentration at the bottom of the ditch, and avoid tearing of the bottom of the ditch.

[0050] In this way, the tread grooves designed in this manner ensure both rolling resistance and sufficient wet performance. Furthermore, the special teardrop groove design allows the tire to maintain a certain level of wet performance throughout its entire lifespan.

[0051] In some embodiments, refer to Figure 3The tire also includes a tire carcass 30 disposed radially inside the tread 10 and a belt layer 40 located between the tread and the tire carcass. The belt layer includes a first belt layer 410, a second belt layer 420, a third belt layer 430 and a fourth belt layer 440 in the radial direction of the tire from the inside to the outside. Further, the width of the second belt layer 420 along the tire axial direction is L1, and 90% ≤ L1 / L ≤ 95%, preferably, L1 / L = 93%. Through this belt layer design, the rigidity of the tire shoulder position is improved, the deformation of the tire shoulder in the extreme durability test is reduced, the concentration of shoulder pressure is reduced, and the area involved in wear is increased, thereby improving the extreme durability.

[0052] Furthermore, refer to Figure 5 The angle between the line connecting point Q in the crown of the second belt layer and one end point P of the second belt layer and the horizontal direction is β, and 3°≤β≤7°, preferably β=5°, while conventional designs usually ≤2°. In this state, the end of the second belt layer tends to collapse. During the extreme durability test, due to the large lateral force, the tire crown will deform, and the collapsed end point of the second belt layer will rise up, approaching the horizontal. In this state, the strain at the end point of the belt layer is small during driving, which is beneficial to the extreme durability performance.

[0053] Furthermore, refer to Figure 3 The distance between one end point of the third belt layer 430 and one end point of the tread along the radial direction of the tire is H, and H≥11mm. This ensures that there is enough rubber material on the shoulder for wear during the extreme durability test, further improving the extreme durability capability.

[0054] In some embodiments, refer to Figure 5 The tread 10 includes a crown layer 110 in contact with the ground and a base layer 120 disposed radially inside the crown layer. The rubber compound used in the crown layer 110 has a hysteresis loss tangent of tanδ = 0.098 and a modulus of 5.35 at 60°C and 5% deformation to ensure rolling resistance performance; simultaneously, at 0°C, the hysteresis loss tangent of tanδ = 0.130 to ensure wet grip performance. The tensile strength Ts of the crown layer 110 at room temperature is 29.5 MPa, the elongation at break Eb is 523%, and at 120°C, the retention rate of Ts*Eb is 60% of that at room temperature. When subjected to prolonged extreme durability tests, the tread rubber compound can still maintain a certain strength after the tread surface temperature rises, improving the ultimate durability capability.

[0055] Furthermore, refer to Figure 5The maximum thickness of the base layer 120 along the radial direction of the tire is h1, and h1 = 3 mm. The rubber compound used in the base layer 120 has a hysteresis loss tangent of tanδ = 0.030 at 60°C. The base layer 120 mainly serves to dissipate heat, thus enabling the base layer 120 to reduce tire rolling resistance to a certain extent, while ensuring that the tread layer has sufficient thickness for wear testing and ensuring ultimate durability.

[0056] Extreme durability tests were conducted on tires with conventional and present design schemes. The conventional design showed severe shoulder damage, with the entire shoulder tread block delaminating. In contrast, the present design exhibited more even stress distribution, with each tread block wearing down uniformly without any tread block breakage. Further references... Figure 7 Through the optimization of the above structure, in the FEA simulation, it can be seen that under extreme durability conditions, the shoulder edge pressure of the optimized scheme can be reduced by more than 60% compared with the conventional design. This can reduce the tire shoulder pressure value, make the overall pressure distribution more uniform, and make tearing less likely to occur by using a more tear-resistant compound, thereby significantly improving the extreme durability.

[0057] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A pneumatic radial tire with low rolling resistance and high wet grip, comprising a tread (10) and circumferential grooves extending along the circumferential direction of the tread, characterized in that, The contour between the highest point of the tread and the endpoint on one side of the tread is divided into a first arc, a second arc, a third arc, and a fourth arc. The radii of the first arc TR1, the second arc TR2, the third arc TR3, and the fourth arc TR4 satisfy the following relationship: TR1:TR2:TR3:TR4=2.3:1.9:1.6:1; Five circumferential grooves are provided. The five circumferential grooves include, from the center of the tread (10) to both sides, a central teardrop-shaped groove (130), two grooves near the central groove (140), and two shoulder teardrop-shaped grooves (150). The central teardrop-shaped groove and the shoulder teardrop-shaped groove are self-closing grooves in the loaded state, and the two grooves near the central groove are open grooves. The central teardrop-shaped groove (130) has a depth of GD3 and a width of GW3. The two grooves near the central groove (140) have depths of GD2 and GD4 and widths of GW2 and GW4. The two shoulder teardrop-shaped grooves (150) have depths of G1D and GD5 and widths of GW1 and GW5, and satisfy the following relationship: GD1=GD2=GD3=GD4=GD5, and GD1 / L=0.045±3%; GW1=GW5, GW2=GW4, GW1:GW2:GW3=1.63±3%:3.88±3%:1±3%, and (GW1+GW2+GW3) / L=0.18±3%; The five circumferential grooves divide the tread (10) into six tread blocks, the widths of which along the width direction of the tread (10) are A, B, C, D, E, and F respectively, and satisfy the following relationship: A=F, B=E, C=D; The width ratio of the patterned blocks A:B:C = (1.84±3%):(1.45±3%):(1.00±3%); C / L = 0.09 ± 3%; Wherein, L is the tread arc length of the tread (10) along the tire width direction; The central teardrop-shaped tread groove and the shoulder teardrop-shaped tread groove include, from the outside to the inside along the radial direction of the tire, a zigzag groove section (210), a straight groove section (220), and a teardrop groove section (230). The maximum width of the zigzag groove section extending along the tread is w1, the width of the straight groove section along the tire axis is w2, and the maximum width of the teardrop groove section along the tire axis is w3, and they satisfy the following relationship: w1:w2:w3=3.5±3%:1:3±3%.

2. The low rolling resistance and high wet grip pneumatic radial tire according to claim 1, characterized in that, The angle between the zigzag groove (210) extending along the tread (10) and the circumferential centerline of the tread (10) is 8°.

3. The low rolling resistance and high wet grip pneumatic radial tire according to claim 2, characterized in that, The depth of the straight groove section (220) along the radial direction of the tire is h2, and h2≥3mm.

4. The low rolling resistance and high wet grip pneumatic radial tire according to claim 3, characterized in that, The depth of the water droplet groove section (230) along the radial direction of the tire is h3, and h3≥4mm.

5. The low rolling resistance and high wet grip pneumatic radial tire according to claim 4, characterized in that, The angle between the upper edge of the cavity at the bottom of the water droplet section (230) and the horizontal direction is α, and 45°≤α≤75°; the chamfer R at the bottom of the water droplet section (230) is ≥2mm.

6. The low rolling resistance and high wet grip pneumatic radial tire according to claim 1, characterized in that, The tire also includes a carcass (30) disposed radially inside the tread (10) and a belt layer (40) located between the tread and the carcass. The belt layer includes a first belt layer (410), a second belt layer (420), a third belt layer (430) and a fourth belt layer (440) in sequence from the inside to the outside along the radial direction of the tire.

7. The low rolling resistance and high wet grip pneumatic radial tire according to claim 6, characterized in that, The width of the second belt layer (420) along the tire axis is L1, and 90%≤L1 / L≤95%. The angle between the line connecting the crown position point Q of the second belt layer and the end point P on one side of the second belt layer and the horizontal direction is β, and 3°≤β≤7°.

8. The low rolling resistance and high wet grip pneumatic radial tire according to claim 7, characterized in that, The distance between one end point of the third belt layer (430) and one end point of the tread along the radial direction of the tire is H, and H≥11mm.

9. The low rolling resistance and high wet grip pneumatic radial tire according to claim 1, characterized in that, The tread (10) includes a crown layer (110) that contacts the ground and a base layer (120) disposed radially inside the crown layer. The maximum thickness of the base layer (120) along the radial direction of the tire is h1, and h1 = 3 mm.

10. The low rolling resistance and high wet grip pneumatic radial tire according to claim 9, characterized in that, The rubber compound used in the crown layer (110) has a hysteresis loss tangent of tanδ=0.098 and a modulus of 5.35 at 60℃ and 5% deformation to ensure rolling resistance performance. The rubber compound used in the tread layer (110) has a hysteresis loss angle tanδ=0.130 at 0℃ to ensure wet grip performance; The tire crown layer (110) has a tensile strength of Ts=29.5MPa and an elongation at break of Eb=523% at room temperature, and the retention rate of Ts*Eb is 60% at room temperature below 120℃.

11. The low rolling resistance and high wet grip pneumatic radial tire according to claim 10, characterized in that, The adhesive used in the base layer (120) has a hysteresis loss tangent of tanδ=0.030 at 60°C.

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