DESC:FIELD OF INVENTION:

00001. The present invention pertains to the design, development and manufacture of AKCC type shock. More particularly, this invention discloses a polymeric composition for development and manufacture of AKCC type shock and vibration mount with improved life, wherein the composition comprises rubber compounds based on Hydrogenated Acrylonitrile Butadiene rubber.

BACKGROUND OF THE INVENTION:

00002. Shock and Vibration mounts (hereafter referred to as SV mounts) are used widely in industry, such as automobiles, power generation, etc. and also in defense sector for mounting equipment in naval ships and submarines. These isolators have dual roles to play. While these isolators offer vibration isolation to/ from a machinery, they also protect the machinery from a mechanical shock. The requirement of better vibration and shock isolation characteristics requires the mount to be compliant, so that the Natural Frequency of the system is to the minimum. However, the mount structure itself needs to be strong enough to provide stability to the supported machinery, as also it should withstand the shock load without structural failure.

00003. The conventional SV mounts mainly employ elastomeric materials, or a combination of air/ fluid and elastomer. Since the elastomer degrades with time due to the environmental and service conditions, the mounts become unserviceable after certain duration. Extensive research has been ongoing to enhance the life of these mounts, while maintaining their static/ dynamic characteristics.

00004. A certain category of these mounts is known as AKCC type mounts, a series of mounts with different load-bearing capacities from 10Kg to 400Kg. Originally from Russian design, they are standard shock and vibration mounts available in the market or made by mount manufacturers to order and are extensively used in mounting of equipment and engines especially in ship building. They are made of steel components named as bottom plate, bracket and bolt sleeve of specified material composition and mechanical properties, held in place with intervening layers of viscoelastic material, to impart the vibration/ shock isolation characteristics (Components drawing and product drawing attached). These are consolidated in the form of a product in a mould by Injection Moulding. After proper treatment, the metallic components are placed in the mould cavity and the elastomeric compound is injected into the cavity. Under high temperature and pressure, the elastomer bonds with the metallic components and forms an integral product with sufficient strength, load-bearing and shock withstanding capacity. The load-deflection characteristics, static and dynamic stiffness, strength, natural frequency, ageing resistance, storage and service life, withstand capability to the operating environmental conditions such as temperature, seawater, humidity, oil etc. are achieved through proper selection and composition of viscoelastic material. Polychloroprene material compositions have traditionally been used in these mounts as the viscoelastic material.

00005. AKCC 40 I/E and AKCC 120 I/E are the two verities of mounts in this category with load bearing capacity of 40Kg and 120Kg respectively. The basic performance characteristics of the mounts are
Performance characteristics SV Mount
AKCC 40 I/E SV Mount
AKCC 120 I/E
Rated Load 40 Kg 120 Kg
Deflection at Rated Load 1.2 +/- 0.4 mm 1.5 +/- 0.4 mm
Natural Frequency 20 Hz +/- 15% 16 Hz +/- 15%
Static stiffness 400 Kgf/cm 750 Kgf/cm
Vibrational stiffness 650 Kgf/cm 1200 Kgf/cm

00006. It has been observed that these SV mounts, after prolonged storage of more than five years show increased static stiffness and lower nominal deflection under rated load than the specified range. The phenomenon is attributed to cross-linking of polymeric chains, resulting in hardening of Polychloroprene material. The character of Polychloroprene Rubber is to increase crystallinity with time, which affects the stiffness, and hence the static/ dynamic characteristics.

00007. Therefore, there exists a need for alternative rubber formulations for SV mounts with improved life, better performance, and better properties than polychloroprene rubber based SV mounts.

00008. The polymer, Hydrogenated Acrylonitrile Butadiene rubber (hereafter referred as HNBR) has an intriguing combination of properties. HNBR has high tensile strength, low permanent set, very good abrasion resistance and high elasticity. Also these are complemented by good stability towards thermal ageing and better properties at low temperatures compared to other heat- and oil-resistant elastomers. In addition HNBR has good static and dynamic properties at operation temperatures and good retention of properties under continuous heat exposure. Also some other key properties of HNBR that make it useful in applications include good viscoelastic properties in HNBR vulcanisates, a wide service temperature range from -40°C to +150°C, resistance to fluids of various chemical compositions and excellent resistance to strongly alkaline and aggressive fluids.

00009. Therefore, the compounds made from low ACN HNBR shows good deflection value, under long term ageing shows good retention in properties, resistance to chemicals compared to polychloroprene (CR) rubber.

000010. In the present invention, a special formulation is developed based on Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content as the viscoelastic material to overcome the above drawback. The developed formulation imparts desired features to SV mounts, such as wide operating temperature range and longer life, as evaluated through Accelerated Ageing study. It also yields better performance characteristics, in terms of static and dynamic properties of the mounts.

OBJECTS OF THE INVENTION:

000011. It is an object of the present invention to provide a polymer composition for AKCC type shock and vibration mount based on Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content as the viscoelastic material .

000012. Another object of the present invention is to provide a composition for SV mounts which is of low hardness, low modulus rubber compound with high strength and long storage and service life for the indented application such as loading of machinery.

000013. Yet another object of the present invention is to provide a formulation imparts desired features to SV mounts, such as wide operating temperature range and longer life, and better performance characteristics, in terms of static and dynamic properties of the mounts.

000014. Further object of the present invention is to provide a metal component and Shock and vibration mount comprising the composition based on Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content as the viscoelastic material.

000015. These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:

000016. This summary is provided to introduce concepts related to elastomer formulation for injection moulding process .The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

000017. Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

000018. According to this invention is provided a polymeric composition comprising Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content as the viscoelastic material for AKCC type shock and vibration mount.

000019. The present invention discloses a novel composition for AKCC type shock and vibration mount comprising:
(i) A base polymer;
(ii) Filler component;
(iii) Plasticizer; and
(iv) Accelerator;
characterized in that the said polymer is Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content of 18-19 %, specific gravity of 0.98 and mooney viscosity, ML1+4 @ 100°C is 62±10.

000020. It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure. The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

000021. It is to be noted, however, that the appended drawing illustrates only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figure. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figure, in which:

000022. Figure 1 illustrates Schematic diagram of metal component and Shock and vibration mount
DETAILED DESCRIPTION OF THE INVENTION:

000023. In the present document, the word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or implementation of the present subject matter described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

000024. While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

000025. The terms “comprises”, “comprising”, “includes” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.

000026. The present invention describes a polymeric composition comprising Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content as the viscoelastic material for AKCC type shock and vibration mount.

000027. More particularly , the present invention discloses a novel composition for AKCC type shock and vibration mount comprising:
(i) A base polymer;
(ii) filler component;
(iii) Plasticizer; and
(iv) Accelerator;
characterized in that the said polymer is Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content of 18-19 %, specific gravity of 0.98 and mooney viscosity, ML1+4 @ 100°C is 62±10.

000028. The filler component present the composition of the present invention strengthen, increase the volume, improve the physical properties of rubber, and strengthen vulcanization. More particularly, the present invention uses Carbon Black SRF (N774) with a phr (parts per 100 unites of the base polymer) value in the range of 25-35. Calcium carbonate can also be used as a filler material.

000029. Plasticizers are usually added to the base polymer to increase softness or flexibility, lowering the glass transition temperature, reducing crystallization, increasing dispersion, or lowering the cost of the compound. The plasticizer used in the composition of the present invention is Tri-(2-ethylhexyl)trimellitate ( hereinafter referred to as TOTM) with a phr range of 45-50.

000030. Accelerators such as Benzothiazole Disulfide (MBTS), and Tetramethyl Thiuram Disulfide (herein after referred ad TMTD) are employed in the present invention. Accelerators increase the speed of vulcanization and permit vulcanization to proceed at lower temperature and with greater efficiency. More particularly, the preferred accelerator is TMTD with a range of 0.5 to 0.8 phr. Further, curing agents such as sulfur is also used in the composition of the present invention.

000031. Additionally the composition of the present invention also comprises antidegradants that deter the aging of rubber such as ZMMBI (2-Mercaptomethylbenzimidazole), Naugard 445 (4,4’-Bis(a,a’-dimethyl benzyl/diphenylamine)), 6PPD (N-(1,3-dimethylbutyl)-N'- Phenyl-P-Phynylenediamine) , TDQ (2,2,4-Trimethyl-1,2-Hydroquinoline).
000032. Further, the composition of the present invention also comprises Zinc Oxide and Stearic Acid as activators. These compounds react together and with the aforementioned accelerators to form a zinc sulfurating compound, which in turn is the key intermediary in adding sulfur to the base polymer and creating sulfur interlinks between the base polymer for efficient vulcanization.
Examples:

000033. The typical formulation of the rubber compound is as follows in
Table 1 below:

INGREDIENT
Phr (Range)

Polymer
100

ZnO
3 – 5

St. Acid
1 – 2

SRF
25 – 35

CaCO3
15 – 20

Naugard 445
1 – 2

ZMMBI
1 – 2

6PPD
1 – 2

TDQ
1 – 2

TOTM
40 – 50

MBTS
0.5 - 1.5

TMTD
0.3 - 0.6

Sulphur
0.3 - 0.6

Table 1
000034. The polymer formulations adopted to meet the characteristics of different mounts for performance enhancement are given in table-2:

Formulation Code
Sample Code >>> AM H1-B B1 AM 40-H1 AM 40-H2
INGREDIENT Phr Phr Phr Phr
Polymer 100 100 100 100
Carbon Black SRF (N774) 30 35 25 25
Plasticizer TOTM 45 45 45 50
Accelerator TMTD (Tetra methyl Thiuram Disulfide) 0.5 0.8 0.8 0.5

Table 2

000035. While quantity of all other chemicals such as Calcium Carbonate (15 phr), antidegradant ZMMBI (2-Mercaptomethylbenzimidazole) (1 phr), Naugard 445 (4,4’-Bis(a,a’-dimethyl benzyl/diphenylamine)) (2 phr), 6PPD (N-(1,3-dimethylbutyl)-N'- Phenyl-P-Phynylenediamine) (2 phr), TDQ (2,2,4-Trimethyl-1,2-Hydroquinoline) (1 phr), Activator Zinc Oxide (5 phr) and Stearic Acid (1.5 phr), Accelerator Benzothiazole Disulfide (MBTS) (1.5 phr) and Sulphur (0.5 phr) are kept constant for all formulations.

Comparative example:
000036. In case of polychloroprene rubber (hereafter referred to as CR) Compound, grade with Mooney viscosity ML1+4@ 100°C, 45-53 MU having medium crystallization rate was used. Here other ingredients of the formulations are Stearic acid, 6PPD N-(1,3-dimethylbutyl)-N'- Phenyl-P-Phynylenediamine, Zinc Oxide, Magnesium oxide, Plasticizer DOP (Dioctyl phthalate) , filler Whiting and Carbon black N774, Benzothiazole Disulfide (MBTS), TMTD (Tetramethyl Thiuram Disulfide) and Na22 (Ethylene Thiourea) and Sulphur.

Mixing of ingredients:

000037. The mixings were carried out in a conventional laboratory open roll mill as per ASTM D3182. The compounding ingredients were added in the order: polymer mastication followed by activators, fillers along with other additives and plasticizers. Before the addition of accelerator and curing agent, the batch was thoroughly cooled.

Rheological properties:

000038. Rheometric properties were tested as per ASTM D5289, in a Montech Rheometer (MDR 3000) . The properties observed are given in table 3:

Sr.No. Properties Compound Code
CR AM H1-B B1 AM40-H1 AM40-H2
A) Rheometric Properties @ 160°C
i) MH (lbf.inch) 46.91 28.54 28.06 27.57 23.99
ii) ML (lbf.inch) 4.33 3.8 3.78 2.46 2.25
iii) TS2 (minutes) 3.80 5.37 5.3 5.62 6.13
iv) Tc90 (minutes) 40.21 12.15 11.71 12.67 13.36

Table 3

000039. The cure characteristics of these mixes were studied as per ASTM D5289, in a Montech Rheometer (MDR-3000) at 160°C. The cure characteristics of the rubber compound, expressed in terms of the scorch time(tS2), Induction time (ts1), optimum cure time (t90), the maximum and minimum values of the torque (MH and ML respectively). The test gives the Torque Vs Time graph as the rubber compound vulcanizes inside the cavity of the rheometer under temperature and pressure. The lowest torque value recorded on the graph, is called ML. It is a measure of stiffness of uncured rubber compound at a given temperature. Data shows comparatively low ML value than CR compounds, indicates low viscosity which helps to flow rubber compound to reach mold cavities smoothly.
000040. TS1 and TS2 are the time from the beginning of the test to the time the torque has increased 1 and 2 units respectively above ML value. It is measured in time units and provides an information about scorch time or at which point the curing actually starts. It also represents compounds storage life. Higher the value more is the storage life. Data indicates newly developed HNBR based compounds are good scorch safety and storage life than CR compound.

000041. As the curing process is completed, the torque attains maximum value and it plateaus out. The slope of the curve depends on the compound and curing system used. MH, the highest torque recorded on the graph, can be regarded as a measure of the composites modulus. Data indicates newly developed HNBR based compounds are having low MH than CR compound, indicates low stiffness and thus the deflection at higher side.

000042. Time from the start of the test to the point where 90% of the MH value is reached is called t’90, the optimum cure time. This is useful to know the curing time of rubber products. Data indicates newly developed HNBR based compounds are having low T90 than CR compound which will be helpful for more productivity.

Moulding / Vulcanization:

000043. The rubber compounds were vulcanized in a hydraulic press having electrically heated platens at 160°C temperature as per timing given in table 4. While in case of mounts, molding is done on specially designed mold cavities on injection molding press at 160°C.

Sr. No. Properties Compound Code
CR AM H1-B B1 AM40-H1 AM40-H2
A) Vulcanization time in minutes
i) Slab 41 13 12 13 14
ii) Compression Set button 51 23 22 23 24
iii) Adhesion test piece 48 20 20 20 20
iv) Mount 48 20 20 20 20

Table 4

000044. Based on rheometric data samples were molded. The cure time allowed for each of the specimen depend on the optimum cure time (T90) of the rubber compound and the extra time allowance for the rubber thickness in the specimen.
Physical properties:

000045. Modulus, tensile strength, elongation at break is tested on Instron tensile testing machine model 3365 as per ASTM D 412, tear strength as per ASTM D 624 die C. Hardness tested by Shore A hardness tester as per ASTM D 2240. Air ageing of samples were carried out in air circulating oven at 100°c for 24 hrs as per ASTM D 573. On button specimen, compression set tested as per ASTM D395 method B, while brittleness temperature was tested as per ASTM D2137. The results obtained on the slab are given in table 5.
000046. 000047. Sr.
Properties CR AM H1-B B1 AM40-H1 AM40-H2

1)
Vulcanization Properties – Before Ageing

i) Shore A 38 32 33 31 31
ii) 100% Mod.( MPa) 0.7 0.5 0.6 0.5 0.5
iii) 200% Mod. ( MPa) 1.0 1 1.1 0.9 0.7
iv) 300% Mod. ( MPa) 2.0 1.3 1.5 1.3 1.1
v) Tens. Strength( MPa) 10.5 13.2 13.1 11.9 11.7
vi) Elon.at Break (%) 700 min. 880 800 810 810
vii) Relative Residual Elongation +5 +5 +5 +5 +5

2)
% Change in Vulcanizate Properties – After Air Ageing at 100°C/24hrs.

i) Hardness (points) +2 +1 +2 +2 +2
ii) Tensile Strength (%) -7 +1 -3 -17 Nil
iii) Elongation at Break (%) -18 -16 -11 -14 -16
3) Density (kg/cm3) 1.29 1.13 1.14 1.1 1.1

4)

Weight change@20-25°C/ 24 hrs
i) 70 isooctane + 30 toluene +52 +29.8 +30.5 +28.69 +25.82
ii) NaCl (10% Wt.Fraction) +1.5 +0.25 +0.2 +0.24 +0.23
5) Rubber metal bond. strength, MPa (min) D429 method A 1.67 2.1, 2.4 2.0, 2.3 2.1, 2.3 2.0, 2.5
6) Brit. temp. °C No cracks & breaks observed after impact @-40°C

Table 5
000048. Table 5 data indicates that, newly developed compounds shows improved tensile strength and elongation at break along with low modulus, low hardness and low stiffness than CR compound. Also after thermal ageing shows good retention in properties than CR. As far as chemical resistance and adhesion properties are concerned HNBR shows much superior values. Also due to low density of HNBR compounds, final product i.e. mount will be lighter than CR mount.

DEFLECTION TEST:

000049. To select the correct compound, to meet the product specification and better properties than CR compound, button deflection of CR compound and DMA properties were tested. For deflection purpose, the experiment is carried on button with diameter29mm having thickness 12.5mm. The observed data is tabulated in table 6. Dynamic properties were tested on slab. Properties were tested in tension mode at room temperature from 1 to 50Hz frequency/ at 0.5% static and at 0.1% dynamic strain. DMA of Metravib make used. Observed values of Tan delta at different frequencies were tabulated in table 7.

Sr. No.
Deflection on Button
CR
AM H1-B
B1
AM40-H1
AM40-H2
i)

Defl.@ 40Kg

2.6 2.63

2.60

3.09

3.44

ii)

Defl.@ 120Kg

4.74
5.22

5.19

5.72

5.95

Table 6
000050. As expected from low hardness and low modulus, most of the HNBR compounds shows higher deflection under specified load when tested on button.
Sr. Frequency (Hz) CR AMH1-B B1 AM 40- H1 AM 40-H2
1. 1 0.0975 0.142 0.169 0.133 0.157
2. 5 0.0995 0.183 0.176 0.176 0.183
3. 10 0.109 0.177 0.174 0.167 0.179
4. 15 0.107 0.175 0.171 0.172 0.178
5. 20 0.111 0.170 0.172 0.162 0.171
6. 25 0.0990 0.155 0.144 0.140 0.149
7. 30 0.0187 0.120 0.128 0.134 0.140
8. 35 0.115 0.171 0.170 0.168 0.168
9. 40 0.124 0.175 0.174 0.174 0.178
10. 45 0.127 0.177 0.179 0.166 0.176
11. 50 0.132 0.179 0.175 0.174 0.179

Table 7

000051. Dynamic properties shows that tan delta value of CR compounds is at lower side than HNBR compounds at corresponding frequencies. Tan delta represents the ratio of the viscous to elastic response or in another words the energy dissipation potential of the material. The tan delta quantifies the way in which a material absorbs and disperses energy. The greater the Tan delta, the more dissipative the material is. It expresses the out-of-phase time relationship between an impact force and the resultant force that is transmitted to the supporting body.

000052. Deflection and Tan delta values data shows that, HNBR compounds shows more damping compare to CR compound. This is due to low %ACN of HNBR and unique compound design with low stiffness.

THERMAL RESISTANCE:
000053. To see the thermal resistance in air, properties of vulcanizates were tested for different duration at different temperatures. The observed data is tabulated in table-8.
Sr. Properties Specification CR AM
H1-B B1 AM 40-H1 AM 40-H2
A) % Change in Vulcanizate Properties – After Air Ageing at 70°C/10days.
i) Tensile Strength (%) -NA- -10 -3 -1 -8 -4
ii) Elongation at break (%) -NA- -7 -7 -3 -6 -6
iii) % Change in Vulcanizate Properties – After Air Ageing at 80°C/10 days.
iv) Tensile Strength (%) -NA- -30 2 -2 -9 -2
v) Elongation at break (%) -NA- -25 -9 -14 -17 -11
B) % Change in Vulcanizate Properties – After Air Ageing at 100°C/24hrs.
i) Hardness (points) -NA- +2 +1 +2 +2 +2
ii) Tensile Strength (%) -NA- -7 +1 -3 -17 -1
iii) Elongation at break (%) 25Max -18 -16 -11 -14 -16
C) % Change in Vulcanizate Properties – After Air Ageing at 100°C/7days.
i) Tensile Strength (%) -NA- -58 -16 -5 -15 -15
ii) Elongation at break (%) -NA- -28 -23 -20 -18 -21
iii) % Change in Vulcanizate Properties – After Air Ageing at 120°C/7days.
iv) Tensile Strength (%) -NA- -57 -23 -7 -15 -12
v) Elongation at break (%) -NA- -70 -20 -22 -20 -27

Table 8
000054. Thermal ageing properties shows that, retention in properties is better for all the HNBR compounds compare to CR compound. This is due to low unsaturation of HNBR and more thermal resistance.

000055. Also long term ageing carried for all compounds. As per Arrhenius equation, CR compound shows 14years life, while other compounds shows life between 34 to 38 years, which is useful for longer storage life as well as service life.
On Product Testing:

000056. These rubber compounds were used to make AKCC 40E and 120E type mounts. The product geometry is depicted in Figure 1. Figure 1 shows the product Mount and its components such as metal plate, metal bracket and bolt sleeve which are secured in their position by the rubber material.

000057. The deflection and natural frequency of these mounts is given in table-9 and table-10 respectively.

Sr.
No.
Description
Spec. Mount / Product codes

AM40-H1
AM40-H2 AM
H1-B B1
1. Deflection @40 Kg load 1.2±0.4mm 0.9 to 1.18 1.18 to 1.4 0.88 to 1.02 0.7 to 0.85
2. Deflection @120 Kg load 1.5±0.4mm 1.89 to 1.92 2.0 to 2.2 1.56 to 1.90 1.59 to 1.73

Table 9
000058. Deflection data shows that, out of selected compound for 40Kg type mount, all compounds shows deflection value within specification. Rubber compound AM40-H2 and AM40H1 shows deflection value on higher side but within acceptable limit) while compound AMH1-B shows values towards lower side though within specification and within acceptable limit. Compound B1, shows some value below acceptable limit.

000059. In case of AKCC 120 mount, rubber compound AMH1-B and B1 shows deflection value within specification limit around middle and upper side of specified values, whereas compound AM40H1 and AM40H2 shows values at extreme upper side of specification value.

000060. So the compounds AM40 H1 and AM40H2 was selected for AKCC40 type mounts and compound AMH1-B and B1 for AKCC120 type mounts.

000061. Natural Frequency of selected compounds are within specified limit (table-10). Also after thermal ageing, change in natural frequency is within acceptable limit.

Sr.
No.
Description
Spec.
Mount / Product codes
AM40-H1 AM40-H2 AMH1-B B1

3.

Resonance Search Test – Natural frequency (Hz) @ amp 0.1mm
i) @ 40Kg rated load 20±15% 20.02,20.8, 21.44 19.9,20.02, 19.16 -NA- -NA-
ii) @120Kg rated load 16±15% -NA- -NA- 16.1,16.0, 16.8 17.1,
17.3

4.
Resonance Search Test – Natural frequency (Hz) @ amp 0.1mm, % Change after thermal ageing at 100°C/24hrs.

i) @ 40Kg rated load Should not exceed more than 50% of initial value -1.63 +3.45 -NA- -NA-
ii) @120Kg rated load -NA- -NA- +0.87 -5.17

Table 10

000062. As the deflection along with other dynamic properties are the key parameters, there is need for low hardness, low modulus rubber compound with high strength and long storage and service life for the indented application. Data shows that HNBR rubber compounds shows comparatively high Tensile strength. After long-term thermal ageing, HNBR compound shows good retention in properties compared to CR compound indicates better life of the product made from HNBR polymer.

Technical Advantages of the Composition of the present Invention:
1. Formulation used to make HNBR compound is composed of low acrylonitrile butadiene rubber, along with other ingredients given in table-1 and description given there. Rubber compound is having low hardness compared to CR compound and so lower stiffness.
2. Rubber compound is having low modulus which creates low stiffness in compound, at the same time shows high strength.
3. Shock and vibration (SV) mounts made are having deflection value towards higher side (but within specification). This is helpful for long term use of SV mounts, as the period required to reach lower limit of deflection value will be more.
4. The SV mounts with the new composition have better Shock and Vibration isolation characteristics. Mounts are having good thermal ageing retention in properties. After 100°C/24hrs ageing also, there is not much change in deflection as well as Natural frequency of mounts which is indication of long storage and application life.
5. Slabs molded for compounds, shows good retention in tensile properties, which is indicating long storage and application life.
6. Chemical resistance of HNBR compounds of the present invention is better than CR compounds for given chemicals.
7. HNBR compounds of the present invention are having low density than CR compound and so the weight of mounts.
8. HNBR compounds of the present invention are having improved adhesion strength between polymer and metal than CR compound.
9. Long term ageing shows life of HNBR compound vulcanizate is more than double the life of CR compound vulcanizate.

,CLAIMS:WE CLAIM:

1. A polymeric composition for AKCC type shock and vibration mount comprising:
(i) A base polymer ;
(ii) filler component;
(iii) Plasticizer; and
(iv) Accelerator;
characterized in that the said polymer is Hydrogenated Acrylonitrile Butadiene rubber of very low Acrylonitrile content of 18-19 %, specific gravity of 0.98 and mooney viscosity, ML1+4 @ 100°C is 62±10.

2. The composition as claimed in claim 1, wherein the filler component is Carbon Black SRF.

3. The composition as claimed in claim 1 , wherein the carbon black is present in an amount in the range of 25-35 parts per 100 units of the base polymer , for the said variety of mounts with nominal load capacity 40 to 120Kg.

4. The composition as claimed in claim 1, wherein the plasticizer is Tri-(2-ethylhexyl)trimellitate.

5. The composition as claimed in claim 1, wherein the Tri-(2-ethylhexyl)trimellitate is present in an amount in the range of 40-50 parts per 100 units of the base polymer, for the said variety of mounts with nominal load capacity 40 to 120Kg.

6. The composition as claimed in claim 1 , wherein the accelerator is selected from Benzothiazole Disulfide ,Sulphur , and Tetramethyl Thiuram Disulfide.

7. The composition as claimed in claim 1, wherein the accelerator is Tetramethyl Thiuram Disulfide.

8. The composition as claimed in claim 1 , wherein Tetramethyl Thiuram Disulfide is present in an amount in the range of 0.5 to 0.8 parts per 100 units of the base polymer, for the said variety of mounts with nominal load capacity 40 to 120Kg.

9. The composition as claimed in claim 1 , wherein the composition comprises antidegradants selected from 2-Mercaptomethylbenzimidazole , 4,4’-Bis(a,a’-dimethyl benzyl/diphenylamine), N-(1,3-dimethylbutyl)-N'- Phenyl-P-Phynylenediamine), (2,2,4-Trimethyl-1,2-Hydroquinoline.

10. The composition as claimed in claim 1, wherein the composition comprises activators selected from Zinc Oxide and Stearic Acid.