FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[see section 10 and rule13]
“A COMPOSITION COMPRISING NATURAL RUBBER AND
ETHYLENE ACRYLIC ELASTOMER, A METHOD TO OBTAIN THE
COMPOSITION AND APPLICATIONS THEREOF”
Name and Address of the Applicant: TATA MOTORS LIMITED, Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai – 400001, Maharashtra, India.
Nationality: INDIAN
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
The present disclosure relates to a composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient. The present disclosure also relates to a method of obtaining said composition as well as its application by way of an automotive suspension bushing composed of the said composition.
BACKGROUND OF THE DISCLOSURE
Suspension bushes are critical components used for connecting suspension links to the wheel side as well as to chassis side on vehicle while properly supporting its weight, isolating the vehicle structure from road inputs.
Vehicle ride and handling poses conflicting requirements from suspension bushes (stiff for better handling performance but soft for better ride performance) which typically need selection of different stiffness rubber isolators in different directions depending on requirements. Very high stiffness of suspension bushes lead to higher road inputs to the vehicle and resulting in higher road noise and vibrations. Relatively lower stiffness rubber bushes are prone to durability problems due to severe jerks to suspension resulting from sudden acceleration or braking of vehicle. This also leads to improper ride and poor handling of vehicle. Hence, the rubber suspension bushes have to be designed to meet both requirements.
Historically Natural Rubber (NR) is being used for vibration isolation application because of its superior mechanical and fatigue properties. However, the behavior of the suspension bushes can be altered to great extent by changing the elastomer type, filler type combination or by varying filler percentage.
Therefore, there is a need in the art to develop a novel blend of a rubber elastomer which can be used as a very effective vibration isolator and which has superior mechanical and fatigue resistant properties.
OBJECTIVE OF THE DISCLOSURE
The first objective of the present invention is to provide a composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.

One objective of the present invention is to provide a method of obtaining a composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.
One objective of the present invention is to provide an automotive suspension bushing composed of the composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.
SUMMARY OF THE DISCLOSURE
The shortcomings of the prior art are overcome and additional advantages are provided through the provision as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.
The present disclosure related to a composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.
In an embodiment of the disclosure, the composition is an elastomeric blend of the NR and the AEM, in ratio ranging from about 10:90 to about 90:10.
In an embodiment of the disclosure, the ratio is about 80:20.
In an embodiment of the disclosure, the elastomeric blend of NR and AEM has hardness of about 55 Shore or about 65 Shore.
In an embodiment of the disclosure, the elastomeric blend is used in the application of automotive suspension bushings.
The present disclosure also relates to a method of obtaining a composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient, said method comprising acts of: (a) mixing the NR along with industrially acceptable excipient to obtain a NR composition; (b) mixing the AEM along with industrially acceptable excipient to obtain an AEM composition; and (c) combining the NR composition and the AEM composition in ratio ranging from about 10:90 to about 90:10, optionally along with industrially acceptable excipients to obtain the said composition.

In an embodiment of the disclosure, the industrially acceptable excipient is selected from group comprising activators, anti-degradants, filler, curing agent, release agents and accelerators or any combination thereof.
In an embodiment of the disclosure, the activators are selected from a group comprising ZnO active, stearic acid, zinc sterate or any combination thereof; the antidegradents are selected from a group comprising diphenyl amine, trimetheyl dihydroquinoline (TDQ), N-(1,3 dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD) (Pilflex 13), P. wax, amine and phenolic based compounds or any combination thereof; the filler is selected from a group comprising Semi Reinforcing Filler N770, Medium thermal black N990, High abrasion furnace black N330, Fast extruding furnace black N550 and Carbon black N325 or any combination thereof; the curing agents are selected from a group comprising peroxides, sulfur, hexametheylene diamine carbamate (DIAK 1) or any combination thereof; the release agents are selected from a group comprising organic phosphate ester, octadecyly amine, phosphate acid ester based compounds or any combination thereof; and the accelerators are selected from a group comprising N cyclohexyl-2 benzothiazole sulfenamide (CBS), thiurams, di phenyl guanidine (DPG), 4,4’ dithiodimorpholine (DTDM), thiurams, guanidines, thiazole and cyanurates based compounds or any combination thereof.
The present invention further relates to an automotive suspension bushing composed of the composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The features of the present disclosure will become more fully apparent from the following description taken in conjunction with the accompanying drawings. Understanding that the drawings depict only several embodiments in accordance with the disclosure and are therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings:
Figure 1 illustrates a high frequency elastomer testing machine.
Figure 2 illustrates a test button as per JIS 6304.
Figure 3 illustrates a test set up.
Figure 4 illustrates dynamic model of elastomers.

Figure 5 illustrates dynamic characteristic of natural rubber having 55 shore hardness at 0.05 amplitude.
Figure 6 illustrates dynamic characteristics of natural rubber having 55 shore hardness at 0.11 amplitude.
Figure 7 illustrates dynamic characteristics of natural rubber having 55 shore hardness at 0.17 amplitude.
Figure 8 illustrates dynamic characteristics of natural rubber having 65 shore hardness at 0.05 amplitude.
Figure 9 illustrates dynamic characteristics of natural rubber having 65 shore hardness at 0.11 amplitude.
Figure 10 illustrates dynamic characteristics of Natural Rubber having 65 Shore Hardness at 0.17 Amplitude.
Figure 11 illustrates dynamic characteristics of NRSBR 55 Shore Hardness at 0.05 Amplitude.
Figure 12 illustrates dynamic characteristics of NRSBR 55 Shore Hardness at 0.11 Amplitude.
Figure 13 illustrates dynamic characteristics of NRSBR 55 Shore Hardness at 0.17 Amplitude.
Figure 14 illustrates dynamic characteristics of NRSBR 65 Shore Hardness at 0.05 Amplitude.
Figure 15 illustrates dynamic characteristics of NRSBR 65 Shore Hardness at 0.11 Amplitude.
Figure 16 illustrates dynamic characteristics of NRSBR 65 Shore Hardness at 0.17 Amplitude.
Figure 17 illustrates dynamic characteristics of NRPBR 55 Shore Hardness at 0.05 Amplitude.
Figure 18 illustrates dynamic characteristics of NRPBR 55 Shore Hardness at 0.11 Amplitude.

Figure 19 illustrates dynamic characteristics of NRPBR 55 Shore Hardness at 0.17 Amplitude.
Figure 20 illustrates dynamic characteristics of NRPBR 65 Shore Hardness at 0.05 Amplitude.
Figure 21 illustrates dynamic characteristics of NRPBR 65 Shore Hardness at 0.11 Amplitude.
Figure 22 illustrates dynamic characteristics of NRPBR 65 Shore Hardness at 0.17 Amplitude.
Figure 23 illustrates dynamic characteristics of NRAEM 55 Shore Hardness at 0.05 Amplitude.
Figure 24 illustrates dynamic characteristics of NRAEM 55 Shore Hardness at 0.11 Amplitude.
Figure 25 illustrates dynamic characteristics of NRAEM 55 Shore Hardness at 0.17 Amplitude.
Figure 26 illustrates dynamic characteristics of NRAEM 65 Shore Hardness at 0.11 Amplitude.
Figure 27 illustrates dynamic characteristics of NRAEM 65 Shore Hardness at 0.11 Amplitude.
Figure 28 illustrates dynamic characteristics of NRAEM 55 Shore Hardness at 0.17 Amplitude.
Figure 29 illustrates dynamic characteristics of Natural Rubber 55 Shore hardness with different amplitude.
Figure 30 illustrates dynamic characteristics of Natural Rubber 55 Shore hardness with different amplitude – Dynamic to Static stiffness ratio.
Figure 31 illustrates dynamic characteristics of Natural Rubber 65 Shore hardness with different amplitude.
Figure 32 illustrates dynamic characteristics of Natural Rubber 65 Shore hardness with different amplitude – Dynamic to Static stiffness ratio.

Figure 33 illustrates dynamic characteristics of NRSBR 55 Shore hardness with different amplitude.
Figure 34 illustrates dynamic to static stiffness ratio of NR SBR 55 Shore hardness with different amplitude.
Figure 35 illustrates dynamic characteristics of NRSBR 65 Shore hardness with different amplitude.
Figure 36 illustrates dynamic to static stiffness ratio of NR SBR 65 Shore hardness with different amplitude.
Figure 37 illustrates dynamic characteristics of NRPBR 55 Shore hardness with different amplitude.
Figure 38 illustrates dynamic to static stiffness ratio of NR PBR 55 Shore hardness with different amplitude.
Figure 39 illustrates dynamic characteristics of NRPBR 65 Shore hardness with different amplitude.
Figure 40 illustrates dynamic to static stiffness ratio of NR PBR 65 Shore hardness with different amplitude.
Figure 41 illustrates dynamic characteristics of NRAEM 55 Shore hardness with different amplitude.
Figure 42 illustrates dynamic to static stiffness ratio of NR AEM 55 Shore hardness with different amplitude.
Figure 43 illustrates dynamic characteristics of NRAEM 65 Shore hardness with different amplitude.
Figure 44 illustrates dynamic to static stiffness ratio of NR AEM 55 Shore hardness with different amplitude.
Figure 45 illustrates dynamic characteristics of Natural Rubber with different hardness.
Figure 46 illustrates dynamic to static stiffness ratio of Natural Rubber with different hardness.

Figure 47 illustrates dynamic characteristics of NRSBR with different hardness. Figure 48 illustrates dynamic to static stiffness ratio of NR SBR with different hardness. Figure 49 illustrates dynamic characteristics of NRPBR with different hardness. Figure 50 illustrates dynamic to static stiffness ratio of NR PBR with different hardness. Figure 51 illustrates dynamic characteristics of NRAEM with different hardness. Figure 52 illustrates dynamic to static stiffness ratio of NR AEM with different hardness. Figure 53 illustrates dynamic characteristics of different Elastomer with 55 shore A. Figure 54 illustrates dynamic to static stiffness ratio of different Elastomer with 55 shore A. Figure 55 illustrates dynamic characteristics of different Elastomer with 65 shore A. Figure 56 illustrates dynamic to static stiffness ratio of different Elastomer with 65 shore A.
DETAILED DESCRIPTION OF DISCLOSURE
To meet the vehicle Noise, Vibration and Harshness (NVH) and dynamics requirements, it is necessary to know the dynamic characteristics of elastomer material used for engine mounts, suspension bushes, exhaust hangers, etc. The dynamic characteristics of suspension bushes play vital role in ride and handling as well as altering road induced noise and vibration at the vehicle level in dynamic condition.
Elastomers are visco-elastic in nature and the ratio of viscous and elastic nature can be altered to a great extent. The dynamic characteristic of bushes depends on the type of elastomers, type and amount of filler used, curing condition and method of testing etc.
In the work presented, a novel blend of Natural Rubber and an ethylene acrylic rubber (AEM Rubber) was tried in which the characteristics under dynamic conditions were studied along with other known elastomer blends (NR/SBR and NR/PBR). The dynamic characteristics including dynamic stiffness, Loss angle, damping co-efficient and static to dynamic stiffness ratio were studied.
Scope of this work is to provide an overview of effect of various elastomer compositions on dynamic response and to choose the appropriate material combination for suspension bush

application. All dynamic characteristics and other properties were measured on standard test buttons.
In line with this a novel blend of Natural Rubber and (AEM) rubber was tried and compared with 100 % Natural Rubber and other known elastomer blends.
The term dynamic mechanical property of elastomers refers to the behaviour of elastomer under stress or strain that changes with time. The time is determined inversely by the frequency of the deformation. Elastomers have combined properties of both solids (Elastic) and liquids (Viscous). Based on the elastic and viscous properties, isolation and damping responses are exhibited by elastomers during dynamic loading conditions.
It is important to understand that damping property is well desired property in elastomers which also governs creep, compression set and stress relaxation.
Natural Rubber, known elastomer blends and novel elastomer blend of Natural Rubber and AEM were evaluated with different amplitude and constant preload respectively. The elastomer combinations were tested for the following:
1. Low frequency vibration isolation/damping properties.
2. High frequency vibration isolation/damping properties.
3. Effect of test amplitude and frequency.
4. Effect of elastomer hardness.
5. Effect of different elastomer type.
METHODOLOGY:
Elastomer combinations selected for suspension bush application was Natural Rubber, a blend of Natural Rubber with SBR, a blend of Natural Rubber with PBR and a novel blend of Natural Rubber with AEM. The blending of Natural rubber and AEM elastomer was done by physical mixing and compounding was done separately. The final compound of Natural Rubber and AEM was blended 80:20 ratio respectively. The subject blending was done because to get homogenized compound where as other elastomer were blended with in the same compound i.e., two different elastomer (Raw Rubber) was taken in to single recipe. The filler combination selected was SRF and MT black with hardness range of 55±2 shore A and 65 ± 2 Shore A.

Table 1: Elastomer combination with different hardness:

Application Hardness Shore A Filler Type Experiments

100 70/30 70/30 80/20
Suspension Bushes 55 SRF&MT NR NR/SBR NR/PBR NR/AEM

65 SRF&MT NR NR/SBR NR/PBR NR/AEM
Table 2: NR/AEM recipe

Ingredients 55 Shore A Hardness 65 Shore A Hardness

NR AEM NR AEM

Phr Range Phr Range Phr Range Phr Range

NR 100 - 100 -
VAMAC GXF - 100 - 100

ACTIVATORS
Zno Active 3-4 - 3-4 -
Stearic Acid 1.5 - 2 1.5-2.0 1.5- 2.0 1.5 – 2.0

ANTI-DEGRADANTS
Nauguard 445 (Diphenyl Amine) - 1.5 – 2.0 - 1.5 – 2.0
TDQ 1.5 -3.0 - 1.5 -3.0 -
Pilflex 13 1.5- 2.0 - 1.5 -2.0 -
P. Wax 0.8- 1.2 - 0.8 -1.2. -

FILLERS
SRF N-774 16-18 23-25 32-36 38- 42
MT N -990 18 -20 - 25-28 -

CURING CHEMICALS
Sulfur 2.4 - 2.8 - 2.4 - 2.8 -
DIAK 1 - 1.5-1.8 - 1.5 - 1.8

ACCELERATORS
CBS 0.8 - 1 - 0.8 - 1 -
DPG - 3 - 4 - 3 - 4
DTDM 0.1 -0.3 - 0.1 - 0.3 -

RELEASE AIDS
VANFRE VAM (Organic phosphate ester) - 0.8 – 1.2 - 0.8 – 1.2
Armeen 18 D(Octadecyl Amine) - 0.3 - 0.5 - 0.3 - 0.5

Blending % 80 20 80 20

NR - Natural Rubber
SBR - Styrene Butadiene Rubber
PBR - Polybutadiene
AEM - Ethylene Acrylic Elastomer
SRF - Semi Reinforced Filler
MT - Medium Thermal Black
HAF N330 - High Abrasion Furnace Black
FEF N550 - Fast Extruding furnace Black
TDQ - Trimetheyl Dihydroquinoline
CBS - N cyclohexyl-2 benzothiazole sulfenamide
DTDM -4,4’ dithiodimorpholine
DIAK1- Hexametheylene Diamine Carbamate
DPG - Diphenyl Guanidine
Alternate fillers:
High Abrasion Furnace Black (HAF N330), Fast Extruding furnace (FEF N550) and Carbon
Black N325.
Mixing Procedure:
1. Ethylene acrylic elastomer is pre masticated for 1 minute. Activators, Anti-degradents and filler were added and mixed together for 3 minutes. Mixed compound passed through the tight nip in two roll mixing mill for 2 times. Curing chemical along with accelerator mixed to this compound for 1 minute. Mixed compound passed through the tight nip in two roll mixing mill for 2 times. Compound stock was taken out with required thickness.
2. Natural rubber is pre masticated for 1.5 minute. Activators, Anti- degradents and filler were added and mixed together for 3 minutes. Mixed compound passed through the tight nip in two roll mixing mill for 2 times. Curing chemical along with accelerator mixed to this compound for 1 minute. Mixed compound passed through the tight nip in two roll mixing mill for 2 times. Compound stock was taken out with required thickness.

3. NR compound and AEM compound were stored for 24 hrs in room temperature. After this 80 % of NR compound and 20% of AEM compound mixed together for 3 minutes. Mixed compound passed through tight nip for 2 times. Compound stock was taken out with required thickness.
Test Specimen and Test Conditions:
It has been known that the condition under which the dynamic characteristics are determined have an influence on the test results hence the measurements were done under precisely specified conditions. The tests were conducted with specified frequency range of 5 to 40, 40 to 100 with amplitude of 0.05 mm, 0.11 mm and 0.17 mm with pre compression of 2.5 mm, 5mm and 7.5 mm respectively in deflection mode. For frequency range of 100 to 300 Hz, test carried out with amplitude of 20 m/s2, 30 m/s2 and 70m/s2 with pre compression of 2.5 mm, 5mm and 7.5 mm respectively in acceleration mode.
All the tests were conducted with ambient temperature range of 23±5°C. Test button dimensions were followed as per JIS 6304.
Table 3: Test conditions of dynamic characterization – Natural Rubber

NATURAL RUBBER
Frequency Amplitude Hardness Shore A
5 to 40 Hz 0.05 mm 55 NR A 55 NR B 65 NR A 65 NR B

0.11 mm

0.17 mm

40 to 100 Hz 0.05 mm 55 NR A 55 NR B 65 NR A 65 NR B

0.11 mm

0.17 mm

100 to 300 Hz 20 m / s2 55 NR A 55 NR B 65 NR A 65 NR B

30 m / s2

70 m / s2

Table 4: Test conditions of dynamic characterization- Natural Rubber + Styrene Butadiene Rubber

NATURAL RUBBER +STYRENE BUTADIENE RUBBER
Frequency Amplitude Hardness Shore A
0.05 mm 55 NRSBR A 55 NRSBR B 65 NRSBR A 65 NRSBR B
5 to 40 Hz 0.11 mm

0.17 mm

40 to 100 Hz 0.05 mm 55 NRSBR A 55 NRSBR B 65 NRSBR A 65 NRSBR B

0.11 mm

0.17 mm

100 to 300 Hz 20 m / s2 55 NRSBR A 55 NRSBR B 65 NRSBR A 65 NRSBR B

30 m / s2

70 m / s2

Table 5: Test conditions of dynamic characterization – Natural Rubber + Polybutadiene Rubber

NATURAL RUBBER +POLY BUTADIENE RUBBER
Frequency Amplitude Hardness Shore A
5 to 40 Hz 0.05 mm 55 NRPBR A 55 NRPBR B 65 NRPBR A 65 NRPBR B

0.11 mm

0.17 mm

40 to 100 Hz 0.05 mm 55 NRPBR A 55 NRPBR B 65 NRPBR A 65 NRPBR B

0.11 mm

0.17 mm

100 to 300 Hz 20 m / s2 55 NRPBR A 55 NRPBR B 65 NRPBR A 65 NRPBR B

30 m / s2

70 m / s2

Table 6: Test conditions of dynamic characterization – Natural Rubber + Ethylene Acrylic Elastomer

NATURAL RUBBER + ETHYLENE ACRLIC ELASTOMER
Frequency Amplitude Hardness Shore A
0.05 mm 55 NRAEM A 55 NRAEM B 65NRAEM A 65NRAEM B
5 to 40 Hz 0.11 mm

0.17 mm

40 to 100 Hz 0.05 mm 55 NRAEM A 55 NRAEM B 65NRAEM A 65NRAEM B

0.11 mm

0.17 mm

100 to 300 Hz 20 m / s2 55 NRAEM A 55 NRAEM B 65NRAEM A 65NRAEM B

30 m / s2

70 m / s2

A - Test specimen 1 B - Test specimen 2
Test Machine:
The static and dynamic characteristics were tested on elastomer test system as disclosed in Figure 1. This system is capable of conducting tests for low and high frequencies. The machine specification and make details are as follows,
Figure 1 High Frequency Elastomer Testing Machine
Make SAGInoMIYA, Japan.
Load capacity 20 KN
Frequency Range 1000 Hz
Max. Amplitude ± 30mm
Fig: 4 Dynamic Model of Elastomers
Dynamic Spring Constant K* = Po/ Xo
Storage Spring Constant Kd = K* cos δ
Loss Spring Constant Ki = K* sin δ
Loss Angle δ = °
Damping Factor C = Ki / ω (N.s / m)

RESULTS AND DISCUSSION:
Table 7: Dynamic Characteristics of Natural Rubber with 55 shore hardness

Frequency Amplitude 55 NR A 55 NR B

K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1)
5 to 40 Hz
(Results @ 20 Hz
) 0.05 mm 186.0 0.0303 0.0450 1.0 192.3 0.0299 0.0458 1.1

0.11 mm 208.5 0.0377 0.0620 1.1 213.1 0.0382 0.0648 1.2

0.17 mm 234.2 0.0338 0.0620 1.3 237.7 0.0336 0.0636 1.4

40 to 100 Hz
(Results @ 100 Hz
) 0.05 mm 201.0 0.0480 0.0154 1.1 204.0 0.0470 0.0150 1.2

0.11 mm 218.0 0.0630 0.0218 1.2 221.3 0.0635 0.0223 1.3

0.17 mm 238.4 0.0675 0.0213 1.3 241.5 0.0630 0.0219 1.4

100 to 300 Hz
(Results @ 150 Hz
) 20 m / s2 210.9 0.0769 0.0151 1.2 219.2 0.0734 0.0170 1.3

30 m / s2 228.2 0.0718 0.0173 1.3 228.2 0.0718 0.0173 1.3

70 m / s2 241.7 0.0708 0.0181 1.4 249.8 0.0656 0.0174 1.4

INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient
decreases.
Dynamic characteristics of Natural Rubber with 55 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 186 ~ 293 0.19 ~ 0.011
5 ~ 300 0.11 205 ~ 295 0.17 ~ 0.012
5 ~ 300 0.17 208 ~ 295 0.19 ~ 0.012

Table 8: Dynamic Characteristics of Natural Rubber with 65 shore hardness

Amplitude 65 N R A 65 N R B
Frequency
K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1)
5 to 40 Hz 0.05 mm 324.6 0.0491 0.1260 1.3 310.7 0.0598 0.1475 1.3
(Results @ 20 0.11 mm 354.2 0.0581 0.1635 1.4 348.5 0.0645 0.1780 1.5
Hz ) 0.17 mm 398.7 0.0601 0.1903 1.6 398.8 0.0655 0.2073 1.7

40 to 100 Hz 0.05 mm 337.9 0.0781 0.0419 1.3 330.6 0.0934 0.0490 1.4
(Results @ 0.11 mm 366.8 0.0865 0.0503 1.5 364.4 0.0991 0.0572 1.5
100 Hz ) 0.17 mm 424.6 0.0925 0.0622 1.7 429.8 0.0983 0.0669 1.8

100 to 300 Hz 20 m / s2 365.9 0.0871 0.0337 1.4 342.1 0.0883 0.0319 1.5
(Results @ 30 m / s2 381.2 0.0928 0.0374 1.5 356.9 0.102 0.0386 1.5
150 Hz ) 70 m / s2 401.1 0.098 0.0415 1.6 376.2 0.1124 0.0446 1.6
INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Dynamic Characteristics of Natural Rubber with 65 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 300 ~ 445 0.47 ~ 0.021
5 ~ 300 0.11 336 ~ 440 0.57 ~ 0.010
5 ~ 300 0.17 383 ~ 462 0.68 ~ 0.023
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Table 9: Dynamic Characteristics of NRSBR with 55 shore hardness.

Amplitude 55 NR+SBR A 55 NR+SBR B
Frequency
K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1)
5 to 40 Hz 0.05 mm 321.1 0.0962 0.2440 1.8 315.0 0.0987 0.2463 1.7
(Results @ 20 Hz 0.11 mm 328.9 0.1108 0.2881 1.8 331.2 0.1051 0.2755 1.8
) 0.17 mm 374.0 0.1089 0.3221 2.1 385.8 0.1049 0.3203 2.1

40 to 100 Hz 0.05 mm 350.7 0.1287 0.0712 2.0 340.3 0.1257 0.0676 1.9
(Results @ 100 Hz 0.11 mm 351.9 0.1324 0.0735 2.0 351.6 0.1359 0.0754 1.9
) 0.17 mm 382.1 0.1356 0.0817 2.1 394.7 0.1341 0.0835 2.2

100 to 300 Hz 20 m / s2 377.2 0.1191 0.0474 2.1 371.1 0.1310 0.0512 2.0
(Results @ 150 Hz 30 m / s2 383.0 0.1282 0.0517 2.1 375.2 0.1291 0.0510 2.1
) 70 m / s2 398.8 0.1375 0.0576 2.2 395.9 0.1349 0.5620 2.2

INTERPRETATION:
Dynamic Characteristics of NR SBR blend with 55 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 287 ~ 456 0.87 ~ 0.030
5 ~ 300 0.11 303 ~ 476 0.99 ~ 0.020
5 ~ 300 0.17 345 ~ 472 1.15 ~ 0.025
Table 10: Dynamic Characteristics of NRSBR with 65 shore hardness

Frequency Amplitude 65 NR+SBR A 65 NR+SBR B

K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1)
5 to 40 Hz
(Results @ 20
Hz ) 0.05 mm 458.3 0.1277 0.4619 2.2 510.9 0.1365 0.5499 2.4

0.11 mm 470.1 0.1419 0.5254 2.3 514.4 0.1503 0.6085 2.4

0.17 mm 634.4 0.1446 0.7227 3.1 654.9 0.1448 0.7467 3.0

40 to 100 Hz
(Results @
100 Hz ) 0.05 mm 523.5 0.1616 0.1329 2.5 584.4 0.1609 0.1478 2.7

0.11 mm 527.1 0.1698 0.1404 2.5 594.7 0.1726 0.1610 2.7

0.17 mm 667.2 0.1671 0.1750 3.2 723.2 0.1739 0.1972 3.3

100 to 300 Hz
(Results @
150 Hz ) 20 m / s2 575.8 0.1432 0.0866 2.7 628.4 0.1515 0.0999 2.9

30 m / s2 587.3 0.1650 0.1014 2.8 626.1 0.1627 0.1067 2.9

70 m / s2 606.6 0.1337 0.0849 2.9 643.4 0.1707 0.1149 2.9
INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Dynamic Characteristics of NR SBR blend with 65 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 415 ~ 782 1.88 ~ 0.040
5 ~ 300 0.11 425 ~ 774 2.20 ~ 0.050
5 ~ 300 0.17 586 ~ 779 2.72 ~ 0.060

Table 11: Dynamic Characteristics of NRPBR with 55 shore hardness

Frequency Amplitude K* (N/mm) tan δ (1/1) C (Ns/mm) Kd /
Ks
(1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd /
Ks
(1/1)
5 to 40 Hz 0.05 mm 193.8 0.0597 0.0918 1.2 198.6 0.0486 0.0767 1.2
(Results @ 20 0.11 mm 211.1 0.0515 0.0865 1.3 217.4 0.0587 0.1014 1.3
Hz ) 0.17 mm 238.3 0.718 0.0679 1.5 243.9 0.0522 0.1012 1.5

40 to 100 Hz 0.05 mm 202.5 0.0961 0.0308 1.2 219.8 0.1007 0.0350 1.3
(Results @ 100 0.11 mm 222.6 0.0864 0.0305 1.4 229.3 0.0999 0.0363 1.4
Hz ) 0.17 mm 249.1 0.0776 0.0307 1.5 1.3 257.4 0.0768 0.0314 1.6


100 to 300 Hz 20 m / s2 216.5 0.0842 0.0193
226.4 0.0569 0.0136 1.4
(Results @ 150 30 m / s2 236.5 0.0741 0.0185 1.5 253.9 0.0669 0.0180 1.5
Hz ) 70 m / s2 255.6 0.0802 0.0217 1.6 261.7 0.0911 0.0252 1.6
INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Dynamic Characteristics of NR PBR blend with 55 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 186 ~ 282 0.26 ~ 0.010
5 ~ 300 0.11 203 ~ 296 0.27 ~ 0.020
5 ~ 300 0.17 226 ~ 312 0.32 ~ 0.010
Table 11: Dynamic Characteristics of NRPBR with 65 shore hardness

Frequency Amplitude K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks
(1/1) 1.5 1.6 1.7 K* (N/mm) tan δ (1/1) C (Ns/mm) Kd /
Ks
(1/1)
5 to 40 Hz 0.05 mm 340.2 0.0761 0.2055
354.3 0.071 0.1996 1.4
(Results @ 20 0.11 mm 365.1 0.0766 0.2219
371.1 0.0775 0.2282 1.5
Hz ) 0.17 mm 402.0 0.0694 0.221
415.0 0.0704 0.2319 1.7

40 to 100 Hz 0.05 mm 355.9 0.1136 0.0639 1.5 1.6 1.8 368.2 0.103 0.0600 1.5
(Results @ 0.11 mm 380.0 0.0961 0.0578
392.7 0.0971 0.0604 1.6
100 Hz ) 0.17 mm 416.5 0.0748 0.0989
437.6 0.1041 0.0721 1.8
1.6 1.6
100 to 300 20 m / s2 382.5 0.0983 0.0397
398.6 0.1148 0.0483

Hz
(Results @
150 Hz ) 30 m / s2 392.4 0.0928 0.0385 1.7 1.8 443.7 0.0815 0.0382 1.8

70 m / s2 426.7 0.1005 0.0453
426.3 0.108 0.0488 1.7
INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Dynamic Characteristics of NR PBR blend with 65 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 321 ~ 452 0.66 ~ 0.040
5 ~ 300 0.11 348 ~ 516 0.72 ~ 0.036
5 ~ 300 0.17 382 ~ 491 0.77 ~ 0.020
Table 12: Dynamic Characteristics of NRAEM with 55 shore hardness

Frequency Amplitude 55 NR+ AEM A 55 NR+ AEM B

K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1)
5 to 40 Hz
(Results @ 20 Hz
) 0.05 mm 251.8 0.1095 0.2180 1.6 264.4 0.1099 0.2300 1.62

0.11 mm 271.0 0.1140 0.2460 1.7 286.4 0.1101 0.2490 1.76

0.17 mm 299.4 0.1130 0.2682 1.9 315.8 0.1052 0.2631 1.94

40 to 100 Hz
(Results @ 100 Hz
) 0.05 mm 281.2 0.1727 0.0762 1.8 296.1 0.1733 0.0804 1.8

0.11 mm 306.3 0.1783 0.0856 2.0 321.2 0.1711 0.0862 2.0

0.17 mm 339.5 0.1710 0.0910 2.2 340.2 0.1656 0.0884 2.1

100 to 300 Hz
(Results @ 150 Hz
) 20 m / s2 318.0 0.1514 0.0505 2.1 335.9 0.1802 0.0632 2.0

30 m / s2 334.5 0.1938 0.0675 2.2 348.9 0.1944 0.0706 2.1

70 m / s2 354.9 0.1961 0.0725 2.3 378.0 0.1915 0.0754 2.3
INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Dynamic Characteristics of NR AEM blend with 55 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 224 ~ 458 0.65 ~ 0.040
5 ~ 300 0.11 251 ~ 450 0.90 ~ 0.040
5 ~ 300 0.17 277 ~ 463 0.93 ~ 0.050

Table 13: Dynamic Characteristics of NRAEM with 65 shore hardness

Frequency Amplitude 65 NR+AEM A 65 NR+AEM B

K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1) K* (N/mm) tan δ (1/1) C (Ns/mm) Kd / Ks (1/1)
5 to 40 Hz
(Results @ 20
Hz ) 0.05 mm 460.6 0.1284 0.4672 2.0 445.2 0.1112 0.3918 1.9

0.11 mm 491.2 0.1428 0.5526 2.1 484.1 0.1153 0.4415 2.0

0.17 mm 546.0 0.1421 0.6117 2.4 564.1 0.1088 0.4856 2.4

40 to 100 Hz
(Results @
100 Hz ) 0.05 mm 528.0 0.2117 0.1740 2.3 502.0 0.1805 0.1419 2.1

0.11 mm 560.5 0.2104 0.1836 2.5 563.5 0.1602 0.1419 2.3

0.17 mm 636.9 0.1867 0.1861 2.7 636.1 0.1521 0.1522 2.6

100 to 300 Hz
(Results @
150 Hz ) 20 m / s2 574.8 0.2519 0.1489 2.5 548.9 0.1735 0.0995 2.3

30 m / s2 611.5 0.2296 0.1452 2.7 605.8 0.1856 0.1173 2.5

70 m / s2 648.0 0.2326 0.1582 2.8 655.6 0.1852 0.1267 2.7
INTERPRETATION:
As the frequency increases, the dynamic stiffness increases and damping coefficient decreases.
Dynamic Characteristics of NR AEM blend with 65 shore hardness are as follows,

Frequency Range (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm)
5 ~ 300 0.05 411 ~ 711 1.81 ~ 0.080
5 ~ 300 0.11 448 ~ 739 1.97 ~ 0.080
5 ~ 300 0.17 504 ~ 806 2.18 ~ 0.080
DYNAMIC CHARACTERISTICS OF ELASTOMER WITH DIFFERENT AMPLITUDE
Natural Rubber with 55 shore hardness
Dynamic stiffness observed to be increasing with increase in amplitude. Dynamic stiffness
response after 200 Hz was observed to be inconsistent with some sharp falls and rises. Refer
fig.29.
Damping coefficient observed to be increasing with increase in amplitude; however it was more responsive till 50 Hz but lesser responsive further. Refer fig.29.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. Similarly, as the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig.30.

The range of damping co-efficient, dynamic stiffness & Kd/Ks according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 186 ~ 255 0.184 ~ 0.004 1.060 ~ 1.450
5 ~300 0.11 205 ~ 277 0.177 ~ 0.002 1.160 ~ 1.580
5 ~300 0.17 208 ~ 293 0.193 ~ 0.011 1.190 ~ 1.160
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 31.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 32.
The range of damping co-efficient, dynamic stiffness & Kd/Ks according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 308 ~ 445 0.389 ~ 0.021 1.220 ~ 1.750
5 ~300 0.11 342 ~ 440 0.520 ~ 0.014 1.350 ~ 1.740
5 ~300 0.17 385 ~ 462 0.619 ~ 0.031 1.520 ~ 1.810
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 33.
As the amplitude increases, the damping co-efficient increases; response is higher till 50 Hz but lower beyond 50 Hz. Refer fig. 31.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 34.

The range of damping co-efficient, dynamic stiffness & Kd/Ks according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 295 ~ 456 0.876 ~ 0.033 1.660 ~ 2.550
5 ~300 0.11 303 ~ 443 0.994 ~ 0.038 1.700 ~ 2.470
5 ~300 0.17 345 ~ 472 1.150 ~ 0.025 1.950 ~ 2.650
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 35.
As the amplitude increases, the damping co-efficient increases; response is higher till 50 Hz but lower beyond 50 HZ. Refer fig. 35.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 36.
The range of damping co-efficient, dynamic stiffness & Kd/Ks according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 415 ~ 694 1.650 ~ 0.056 1.060 ~ 1.450
5 ~300 0.11 464 ~ 744 2.209 ~ 0.057 1.160 ~ 1.580
5 ~300 0.17 606 ~ 779 2.723 ~ 0.062 1.190 ~ 1.160
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 35.
As the amplitude increases, the damping co-efficient increases; response is higher till 50 Hz but lower beyond 50 Hz. Refer fig. 37.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 38.

The range of damping co-efficient & dynamic stiffness according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 186 ~ 282 0.223 ~ 0.020 1.140 ~ 1.720
5 ~300 0.11 203 ~ 296 0.275 ~ 0.020 1.250 ~ 1.800
5 ~300 0.17 226 ~ 305 0.309 ~ 0.016 1.390 ~ 1.870
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 39.
As the amplitude increases, the damping co-efficient increases; response is higher till 50 Hz but lower beyond 50 Hz. Refer fig. 39.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 40.
The range of damping co-efficient, dynamic stiffness & Kd/Ks according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 321 ~ 452 0.667 ~ 0.041 1.370 ~ 1.912
5 ~300 0.11 354 ~ 443 0.693 ~ 0.018 1.440 ~ 1.800
5 ~300 0.17 395 ~ 491 0.832 ~ 0.024 1.600 ~ 1.990
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 41.
As the amplitude increases, the damping co-efficient increases; response is higher till 50 Hz but lower beyond 50 Hz. Refer fig. 41.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 42.

The range of damping co-efficient & dynamic stiffness according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 224 ~ 411 0.908 ~ 0.049 1.480 ~ 2.660
5 ~300 0.11 251 ~ 416 0.908 ~ 0.045 1.660 ~ 2.710
5 ~300 0.17 277 ~ 455 0.933 ~ 0.054 1.830 ~ 2.950
INTERPRETATION:
As the amplitude increases, the dynamic stiffness increases and damping co-efficient increases. Refer fig. 43.
As the amplitude increases, the damping co-efficient increases; response is higher till 50 Hz but lower beyond 50 Hz. Refer fig. 43.
As the frequency increases, the Kd/Ks ratio increases irrespective of amplitude and hardness. As the amplitude increases the Kd/Ks ratio also increases irrespective of frequency and hardness. Refer fig. 44.
The range of damping co-efficient, dynamic stiffness and Kd/Ks according to amplitude is given below,

Frequency (Hz) Amplitude (mm) Dynamic Stiffness Range (N/mm) Damping Co-efficient Range(Ns/mm) Kd/Ks (1/1)
5 ~300 0.05 418 ~ 678 1.813 ~ 0.088 1.850 ~ 2.940
5 ~300 0.11 450 ~ 739 1.973 ~ 0.099 2.000 ~ 3.200
5 ~300 0.17 504 ~ 806 2.184 ~ 0.106 1.600 ~ 3.500
DYNAMIC CHARECTERISTICS OF ELASTOMER WITH DIFFERENT HARDNESS
Natural Rubber with different hardness
As the hardness increases, the dynamic stiffness and damping co-efficient increases significantly. Refer fig.45.
As the hardness increases the Kd/Ks ratio also increases significantly irrespective of frequency and amplitude. Refer fig. 46.

The range of damping co-efficient, dynamic stiffness and Kd./Ks according to material hardness is given below,

Frequency (Hz) Hardness Shore A Dynamic Stiffness (N/mm) Damping Co-efficient (Ns/mm) Kd/Ks (1/1)
5 ~300 55 186 ~ 255 0.184 ~ 0.004 1.060 ~ 1.450
5 ~300 65 308 ~ 445 0.389 ~ 0.021 1.220 ~ 1.750
INTERPRETATION:
As the hardness increases, the dynamic stiffness and damping co-efficient increases significantly. Refer fig.47.
As the hardness increases the Kd/Ks ratio also increases significantly irrespective of frequency and amplitude. Refer fig.48.
The range of damping co-efficient , dynamic stiffness and Kd./Ks according to material hardness is given below,

Frequency (Hz) Hardness Shore A Dynamic Stiffness (N/mm) Damping Co-efficient (Ns/mm) Kd/Ks (1/1)
5 ~300 55 295 ~ 456 0.876 ~ 0.033 1.660 ~ 2.550
5 ~300 65 415 ~ 694 1.656 ~ 0.056 2.000 ~ 3.340
INTERPRETATION:
As the hardness increases, the dynamic stiffness and damping co-efficient increases significantly. Refer fig.49.
As the hardness increases the Kd/Ks ratio also increases significantly irrespective of frequency and amplitude. Refer fig.50.
The range of damping co-efficient & dynamic stiffness according to amplitude is given below,

Frequency (Hz) Hardness Shore A Dynamic Stiffness (N/mm) Damping Co-efficient (Ns/mm) Kd/Ks (1/1)
5 ~300 55 186 ~ 282 0.223 ~ 0.020 1.140 ~ 1.720
5 ~300 65 321 ~ 452 0667 ~ 0.0411 1.370 ~ 1.910

INTERPRETATION:
As the hardness increases, the dynamic stiffness and damping co-efficient increases significantly. Refer fig.51.
As the hardness increases the Kd/Ks ratio also increases significantly irrespective of frequency and amplitude. Refer fig.52.
The range of damping co-efficient & dynamic stiffness according to amplitude is given below:

Frequency (Hz) Hardness Shore A Dynamic Stiffness (N/mm) Damping Co-efficient (Ns/mm)
5 ~300 55 224 ~ 411 0.653 ~ 0.049
5 ~300 65 418 ~ 678 1.813 ~ 0.088
As the basic elastomer type changes, the dynamic response also changes according to the basic back bone structure of elastomer. Refer fig.53.
The dynamic stiffness of elastomer are categorized as follows,
NRSBR> NRAEM> NRPBR> NR

Elastomer Type Frequency (Hz) Dynamic Stiffness (N/mm)
NRSBR 5 ~ 300 295 ~ 456
NRAEM 5 ~ 300 224 ~ 411
NRPBR 5 ~ 300 186 ~ 282
NR 5 ~ 300 186 ~ 255
The damping co-efficient of elastomer are categorized as follows, NRSBR> NRAEM >NRPBR>NR

Elastomer Type Frequency (Hz) Dynamic Stiffness (N/mm)
NRSBR 5 ~ 300 0.876 ~ 0.033
NRAEM 5 ~ 300 0.653 ~ 0.049
NRPBR 5 ~ 300 0.223 ~ 0.020
NR 5 ~ 300 0.184 ~ 0.004

The ratio of dynamic to static stiffness of elastomer are categorized as follows, NR< NRPBR< NRAEM< NRSBR

Elastomer Type Frequency (Hz) Kd/Ks (1/1)
NR 5 ~ 300 1.060 ~ 1.450
NRPBR 5 ~ 300 1.140 ~ 1.720
NRAEM 5 ~ 300 1.480 ~ 2.660
NRSBR 5 ~ 300 1.660 ~ 2.550
Refers to above comparison, NRAEM blend exhibits highest damping with slight increase in dynamic stiffness characteristics compared to other combinations. Other known combinations exhibits either higher damping with higher dynamic stiffness or lesser damping with lesser dynamic stiffness.
Higher damping and lesser dynamic stiffness or higher damping with slight increase in dynamic stiffness is the typical requirement for elastomer components including suspension bushes where damping is required above nominal requirement.
As the basic elastomer type changes, the dynamic response also changes according to the nature of elastomer. Refer fig.55.
The dynamic stiffness of elastomer are categorized as follows, NRAEM> NRSBR> NRPBR> NR

Elastomer Type Frequency (Hz) Dynamic Stiffness (N/mm)
NRAEM 5 ~ 300 418 ~ 678
NRSBR 5 ~ 300 415 ~ 694
NRPBR 5 ~ 300 321 ~ 452
NR 5 ~ 300 308 ~ 445

The damping co-efficient of elastomer are categorized as follows, NRAEM> NRSBR>NRPBR>NR

Elastomer Type Frequency (Hz) Damping Co-efficient (Ns/mm)
NRAEM 5 ~ 300 1.813 ~ 0.088
NRSBR 5 ~ 300 1.656 ~ 0.056
NRPBR 5 ~ 300 0.667 ~ 0.041
NR 5 ~ 300 0.389 ~ 0.021
The ratio of dynamic to static stiffness of elastomer are categorized as follows,

Elastomer Type Frequency (Hz) Kd/Ks (1/1)
NR 5 ~ 300 1.220 ~ 1.750
NRPBR 5 ~ 300 1.370 ~ 1.912
NRAEM 5 ~ 300 1.850 ~ 2.940
NRSBR 5 ~ 300 2.000 ~ 3.340
In the above comparison, NRAEM blend exhibits highest damping with increase in dynamic stiffness or equal dynamic stiffness compared to NRSBR combination. Other known combinations exhibits either higher damping with higher dynamic stiffness or lesser damping with lesser dynamic stiffness.
Higher damping and lesser dynamic stiffness or higher damping with slight increase in dynamic stiffness is the typical requirement for elastomer components including suspension bushes where damping is required above nominal requirement to address low frequency damping.
CONCLUSION:
1. As the frequency increases, the dynamic stiffness increases and damping co-efficient decreases irrespective of hardness, tests amplitude or elastomer type.
2. For low strains, as the test amplitude increases, the dynamic stiffness and damping coefficient both increase irrespective of hardness, frequency or elastomer type.
3. For the same material; as hardness increases, the dynamic stiffness and damping coefficient both increase significantly irrespective of test amplitude or frequency.

4. As the frequency increases, the dynamic to static stiffness ratio (Kd/Ks) increases irrespective of hardness or elastomer type.
5. For low strains, as the test amplitude increases, the dynamic to static stiffness ratio (Kd/Ks) increases irrespective of hardness or material.
6. For the same material; as hardness increases the dynamic to static stiffness ratio (Kd/Ks) increases significantly irrespective of test amplitude or frequency.
7. As the elastomer type changes the dynamic characteristics change significantly. Different elastomers can be characterized as follows,
In case of 55 shore hardness,
Dynamic Stiffness - NRAEM> NRSBR> NRPBR> NR
Damping Co-efficient - NRAEM> NRSBR>NRPBR>NR
Kd/Ks - NR< NRPBR< NRAEM< NRSBR
In case of 55 shore hardness, novel blend of NR & AEM was found to have highest damping and dynamic stiffness in comparison with other known elastomer blend.
In case of 65 shore hardness,
Dynamic Stiffness - NRSBR> NRAEM> NRPBR> NR
Damping Co-efficient - NRSBR> NRAEM >NRPBR>NR
Kd/Ks - NR< NRPBR< NRAEM< NRSBR
In case of 65 shore hardness, novel blend of NR& AEM was found to have highest damping next to NRSBR blend in comparison with other known elastomer blend.
NRAEM with 80:20 ratio compound exhibits highest damping with slight increase in dynamic stiffness (compared to nominal dynamic stiffness), which is typical requirement of elastomer components including suspension bush when damping is required above nominal requirement to address low frequency damping. Higher dynamic stiffness will deteriorates the overall NVH performance thus, it is prefer to keep the dynamic stiffness as less as possible.
Based on conflicting requirements needed for elastomer components including suspension bushes in form of stiffness, isolation for low & high frequency vibration and damping; right combination can be selected based on above results.

Please note that, the following table describes the recipe details of NR and AEM blend. The tables numbered 14, 15 and 16 provide examples for a few combinations of elastomeric blends which were carried out.
Table 14

Ingredients 55 S Har
NR
Phr
100
-
3 1.8
-
1.5
-
1
-
1.5 18 20
2.8
1 0.3
-
-
80 hore A dness 65 Sh Hard ore A ness
AEM
Phr
-100
-1.8
1
-
2
-
0.5
-
42 -
---1.5 4
20

AEM NR

Phr Phr

NR
- 100

VAMAC GXF
100 -

Zno Active
- 3

Stearic Acid
1.8 1.8

VANFRE VAM (Organic phosphate ester)
1 -

Pilflex 13
- 1.5

Nauguard 445 (Diphenyl Amine)
2 -

P. Wax
- 1

Armeen 18 D(Octadecyl Amine)
0.5 -

TDQ
- 1.5

SRF N-774
25 36

MT N -990
- 25

Sulfur
- 2.8

CBS
- 1

DTDM
- 0.3

DIAK 1
1.5 -

DPG
4 -

Blending %
20 80

Table 15

Ingredients 55 S Har
NR
Phr
100 -4 2
-
2
-
-
-
3 16 18
2.4 0.8 0.3
-
-
80 hore A dness 65 Sh Hard ore A ness
AEM
Phr
-
100
-
2
0.8
-
1.5
-
-
-
38 -
---1.8 3
20

AEM NR

Phr Phr

NR
- 100

VAMAC GXF
100 -

Zno Active
- 4

Stearic Acid
2 2

VANFRE VAM (Organic phosphate ester)
0.8 -

Pilflex 13
- 2

Nauguard 445 (Diphenyl Amine)
1.5 -

P. Wax
- -

Armeen 18 D(Octadecyl Amine)
- -

TDQ
- 3

SRF N-774
23 34

MT N -990
- 27

Sulfur
- 2.4

CBS
- 0.8

DTDM
- 0.3

DIAK 1
1.8 -

DPG
3 -

Blending %
20 80

Table 16

Ingredients 55 S Har
NR
Phr
100 -3 2
-
1.5
1
-
1.2
2 18 18
2.8
1 0.2
-
-
80 hore A dness 65 Sh Hard ore A ness
AEM
Phr
-100
-1.5
1.2
-
2
-
0.8
-
40 -
-
-
-1.5 3.5
20

AEM NR

Phr Phr

NR
- 100

VAMAC GXF
100 -

Zno Active
- 3

Stearic Acid
1.5 2

VANFRE VAM (Organic phosphate ester)
1.2 -

Pilflex 13
- 1.5

Nauguard 445 (Diphenyl Amine)
2 1

P. Wax
- -

Armeen 18 D(Octadecyl Amine)
0.8 -

TDQ
- 2

SRF N-774
25 32

MT N -990
- 28

Sulfur
- 2.8

CBS
- 1

DTDM
- 0.2

DIAK 1
1.5 -

DPG
3.5 -

Blending %
20 80

EQUIVALENTS
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be

interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

WE CLAIM:
1. A composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.
2. The composition as claimed in claim 1, wherein the composition is an elastomeric blend of the NR and the AEM, in ratio ranging from about 10:90 to about 90:10.
3. The composition as claimed in claim 2, wherein the ratio is about 80:20.
4. The composition as claimed in claim 2, wherein the elastomeric blend of NR and AEM has hardness of about 55 Shore or about 65 Shore.
5. The composition as claimed in claim 2, wherein the elastomeric blend is used in the application of automotive suspension bushings.
6. A method of obtaining a composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient, said method comprising acts of:
a. mixing the NR along with industrially acceptable excipient to obtain a NR
composition;
b. mixing the AEM along with industrially acceptable excipient to obtain an
AEM composition; and
c. combining the NR composition and the AEM composition in ratio ranging
from about 10:90 to about 90:10, optionally along with industrially acceptable
excipients to obtain the said composition.
7. The composition as claimed in claim 1 and the method as claimed in claim 6, wherein the industrially acceptable excipient is selected from group comprising activators, anti-degradants, filler, curing agent, release agents and accelerators or any combination thereof.
8. The composition and the method as claimed in claim 7, wherein the activators are selected from a group comprising ZnO active, stearic acid, zinc sterate or any combination thereof; the antidegradents are selected from a group comprising diphenyl amine, trimetheyl dihydroquinoline (TDQ), N-(1,3 dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD), P. wax, amine and phenolic based compounds or

any combination thereof; the filler is selected from a group comprising Semi Reinforcing Filler N770, Medium thermal black N990, High abrasion furnace black N330, Fast extruding furnace black N550 and Carbon black N325 or any combination thereof; the curing agents are selected from a group comprising peroxides, sulfur, hexametheylene diamine carbamate (DIAK 1) or any combination thereof; the release agents are selected from a group comprising organic phosphate ester, octadecyly amine, phosphate acid ester based compounds or any combination thereof; and the accelerators are selected from a group comprising N cyclohexyl-2 benzothiazole sulfenamide (CBS), thiurams, di phenyl guanidine (DPG), 4,4’ dithiodimorpholine (DTDM), thiurams, guanidines, thiazole and cyanurates based compounds or any combination thereof.
9. An automotive suspension bushing composed of the composition comprising natural rubber (NR) and ethylene acrylic elastomer (AEM), optionally along with industrially acceptable excipient.