Epoxidised natural rubber based blend for antistatic footwear application

Abstract

Electrically conductive vulcanized epoxidized natural rubber [ENR]-carbon black blends can be produced by using either internal mechanical mixing method or open milling method. These two methods are commercially friendly due to their practicability and high production rate. The addition of vulcanization system, either sulfur or peroxide type does not affect the electrical properties of the vulcanized blends. All vulcanized blends prepared in this innovation show useful electrical properties with electrical volume resistances as low as the order of 10.sup.1 ohms. All these vulcanized blends also exhibit good mechanical properties with tensile strengths up to 26.0 MPa and Dunlop rebound resiliencies of 14.0% (i.e. high damping property). The black color level of all these vulcanized blends is adjustable. As a result of good electrical and mechanical properties (especially high damping property), they have good potential to be used for antistatic footwear manufacturing and application.

Claims

1. A method for preparation of epoxidized natural rubber based blend for antistatic footwear application and manufacturing comprising: epoxidized natural rubber, carbon blacks, antioxidants, processing oils, processing waxes and vulcanisation agents wherein the method comprises the steps of: (a) adding epoxidized natural rubber to an internal mechanical mixing device; (b) mixing of epoxidized natural rubber with carbon blacks, processing oils, processing waxes, and antioxidants by using the internal mechanical mixing device to produce masterbatch; (c) discharge of the masterbatch from the internal mechanical mixing device; (d) mixing of masterbatch with vulcanisation agents by using an open milling device to produce blend; (e) discharging the blend from the open milling device; and (f) vulcanisation of the blend by heating or microwave.

2. The method according to claim 1, wherein step (b) further comprising the step of adding vulcanisation activators.

3. The method according to claim 1 wherein step (d) further comprises the step of adding either vulcanisation accelerators or vulcanisation coagents or whitening agents or in any combination thereof.

4. A method for preparation of epoxidized natural rubber based blend for antistatic footwear application and manufacturing comprising: epoxidized natural rubber, carbon blacks, antioxidants, processing oils, processing waxes and vulcanisation agents wherein the method comprises the steps of: (a) adding of epoxidized natural rubber to an open milling device; (b) mixing of epoxidized natural rubber with carbon blacks, processing oils, processing waxes, antioxidants by using the open milling device to produce masterbatch; (c) mixing of the masterbatch with vulcanisation agents by using the open milling device to produce blend; (d) discharge of the blend from the open milling device; and (e) vulcanisation of the blend by heating or microwave.

5. The method according to claim 4, wherein step (b) further comprising the step of adding vulcanisation activators to the masterbatch.

6. The method according to claim 4, wherein step (c) further comprising the step of adding either vulcanisation accelerators or vulcanisation coagents or whitening agents or in any combination thereof.

7. The method according to claim 1, wherein the vulcanisation process of the ENR based blends are performed at temperature ranges from 100-250 C. by either heating or microwave.

8. The method for preparation of epoxidized natural rubber based blend according to claim 1, wherein the epoxidized natural rubber based blend composition comprises: 50.0 to 150.0 part per hundred rubber [p.p.h.r.] of epoxidized natural rubber; 5.0 to 60.0 p.p.h.r. of carbon blacks; 0.1 to 20.0 p.p.h.r. of antioxidants with a purity level of 80.0-100.0 wt %; 1.0 to 60.0 p.p.h.r. of processing oils; 0.05 to 20.0 p.p.h.r. of processing waxes; 0.1 to 10.0 p.p.h.r. of vulcanisation agent with a purity level of 30.0-100.0 wt %.

9. The method for preparation of epoxidized natural rubber based blend according to claim 1, wherein the epoxidized natural rubber based blend further comprises: vulcanisation accelerators added in step (b) with a purity level of 80.0-100.0 wt %; vulcanisation activators added in step (d) with a purity level of 80.0-100.0 wt %; and vulcanisation coagents added in step (d).

10. The method for preparation of epoxidized natural rubber based blend according to claim 1, wherein the epoxidized natural rubber based blend comprises vulcanisation accelerators, vulcanisation activators and vulcanisation coagents in order to accelerate, activate and enhance the epoxidized natural rubber based blends vulcanisation process.

11. The method for preparation of epoxidized natural rubber based blend according to claim 1, wherein the epoxidized natural rubber based blend further comprises whitening agents added in step (d) in order to adjust its black colour level.

12. The method for preparation of epoxidized natural rubber based blend according to claim 1, wherein whitening agents are added in step (d) and have a purity level of 80.0-100.0 wt %.

13. The method according to claim 5 wherein step (c) further comprises the step of adding either vulcanisation accelerators or vulcanisation coagents or whitening agents or in any combination thereof.

14. The method for preparation of epoxidized natural rubber based blend according to claim 4, wherein the epoxidized natural rubber based blend composition comprises: 50.0 to 150.0 part per hundred rubber [p.p.h.r.] of epoxidized natural rubber; 5.0 to 60.0 p.p.h.r. of carbon blacks; 0.1 to 20.0 p.p.h.r. of antioxidants with a purity level of 80.0-100.0 wt %; 1.0 to 60.0 p.p.h.r. of processing oils; 0.05 to 20.0 p.p.h.r. of processing waxes; 0.1 to 10.0 p.p.h.r. of vulcanisation agent with a purity level of 30.0-100.0 wt.

15. The method for preparation of epoxidized natural rubber based blend according to claim 4, wherein the epoxidized natural rubber based blend further comprises: vulcanisation accelerators added in step (b) with a purity level of 80.0-100.0 wt %; vulcanisation activators added in step (c) with a purity level of 80.0-100.0 wt %; and vulcanisation coagents added in step (c).

16. The method for preparation of epoxidized natural rubber based blend according to claim 4, wherein the epoxidized natural rubber based blend further comprises vulcanisation accelerators, vulcanisation activators and vulcanisation coagents in order to accelerate, activate and enhance the epoxidized natural rubber based blends vulcanisation process.

17. The method for preparation of epoxidized natural rubber based blend according to claim 4, wherein the epoxidized natural rubber based blend further comprises whitening agents added in step (c) in order to adjust its black colour level.

18. The method for preparation of epoxidized natural rubber based blend according to claim 4, wherein whitening agents are added in step (c) and have a purity level of 80.0-100.0 wt %.

19. The method according to claim 5, wherein step (c) further comprising the step of adding either vulcanisation accelerators or vulcanisation coagents or whitening agents or in any combination thereof.

20. The method according to claim 4, wherein the vulcanisation process of the ENR based blends are performed at temperature ranges from 100-250 C. by either heating or microwave.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:

(2) FIG. 1: illustrates the basic chemical structure of the smallest repeat unit of an epoxidised natural rubber example.

(3) FIG. 2: illustrates exemplary flowchart of the first method of preparation of the epoxidised natural rubber based blend, namely the internal mechanical mixing method.

(4) FIG. 3: illustrates exemplary flowchart of the second method of preparation of the epoxidised natural rubber based blend, namely the open milling method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) Definition

(6) 1. Vulcanisation: as used herein the term means a process of crosslinking of a rubber's polymer chains 2. Vulcanisation agent: as used herein the term means any chemicals (for examples, sulfur and peroxide) added to a rubber to create crosslinking reaction of the rubber's polymer chains 3. Vulcanisation accelerator: as used herein the term means any chemicals added to the rubber as catalyst to accelerate vulcanisation reaction 4. Vulcanisation activator: as used herein the term means any chemicals added to the rubber as catalyst to activate vulcanisation reaction 5. Vulcanisation coagent: as used herein the term means any chemicals added to the rubber to enhance its polymer chains crosslinking efficiency and level 6. Vulcanisation system: as used herein the term means a system that comprising of vulcanisation agents, vulcanisation accelerators, vulcanisation activators and vulcanisation coagents

(7) The present invention relates to an environmentally friendly and electrically conductive vulcanised epoxidised natural rubber (ENR) blend targeted for antistatic footwear (includes both inner- and outer-shoe soles) application and manufacturing. Hereinafter, this specification will describe the present invention according to the preferred embodiments of the present invention. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the scope of the appended claims.

(8) The present invention also describes two methods for preparation of vulcanised electrically conductive ENR based blend for antistatic footwear application, i.e. the internal mechanical mixing method and the open milling method. All vulcanised electrically conductive rubber blends in this present invention are based on ENR as the rubber host and carbon black as the only electrically conductive filler. These two major constituent materials in solid form are known to be highly processable with the help of some common mechanical mixing devices, such as internal mechanical mixing device (refer to FIG. 2) and open milling device (refer to FIG. 3). The level of black colour of all vulcanised electrically conductive ENR based blends in this present invention is also adjustable with the inclusion of whitening agents.

(9) In view of problems such as material sustainability issue, poor fillers dispersion, low ageing resistance and also low comfort level due to hard materials for synthetic polymer based blends, it is now able to demonstrate that the very low electrical resistances of the vulcanised (at temperature 15050 C.) epoxidised natural rubber-carbon black blends (reaching at the order of 10.sup.1 ohms in term of volume resistance) can be produced directly by using either the internal mechanical mixing method or the open milling method, which are commercially friendly methods due to their practicability and high production rate. Processing aids such as oils and waxes are also introduced to the blends in order to enhance the processability and dispersion level of the carbon blacks within the solid ENR host matrixes.

(10) Carbon blacks are common electrical conductive fillers and commercially available in different grades at reasonable market pricing. Potential commercial applications (such as for antistatic footwear products) with more interesting visual appearance (i.e. the adjustable level of black colour of the rubber blend due to the inclusion of whitening agent) can also be manufactured using this type of vulcanised ENR blend. Suitable methods for processing this type of vulcanised ENR based blend are including various types of rubber processing equipment, such as injection moulding, extrusion and hot press-moulding.

(11) Masterbatches with different compositions of ENR, carbon black, antioxidants, processing oils, processing waxes and vulcanisation activators are prepared by using either an internal mechanical mixing device (at temperature of between 25 to 230 C., fill factor of between 0.60 to 0.90 and rotors speed of between 50-180 rounds per minute) or by using an open milling device (at temperature of between 25-230 C.) at the first stage of mixing process.

(12) At the second stage of mixing, vulcanisation agents (either sulfur or peroxide), vulcanisation accelerators, vulcanisation coagents and whitening agents are added later (during the second stage of mixing process) to the masterbatch by using an open milling device (at temperature 30-70 C.) in order to avoid the premature vulcanisation problem that can cause hardening and reducing the processability of the produced ENR based blends.

(13) The total mixing period to produce ENR based blend by using both types of methods is fallen between 3 to 60 minutes.

(14) The vulcanisation process of all ENR based blends are performed at temperature ranges from 100-250 C. by either heating or microwave.

(15) All vulcanised (at temperature 15050 C.) ENR based blends (including 5.0 to 60.0 p.p.h.r. of carbon blacks) prepared by using either internal mechanical mixing method or open milling method exhibit low electrical resistances (with the range of order from 10.sup.1-10.sup.10 ohms in term of volume resistances) and other good physical properties (with tensile strengths equal 16.0 to 26.0 MPa, elongations at break equal 140.0 to 680.0%, tear strengths equal 10.0 to 38.0 N/mm, hardness equals of Shore A 30.0 to 90.0, compression sets equal 8.0 to 65.0%, Dunlop rebound resiliencies equal 14.0 to 56.0% and Akron abrasions equal 4.0 to 50.0 mm.sup.3/500 rev).

(16) Mixing proportions and function of each of the raw materials, chemicals and processing devices used to produce the electrical conductive vulcanised ENR based blends are listed as following:

(17) From hereinbelow, the preferred embodiments of the present invention will be discussed in relation to the accompanying FIGS. 1 to 3, which will be used independently or in any combination thereof.

(18) 50.0 to 150.0 parts per hundred rubber (p.p.h.r.) of solid epoxidised natural rubber [ENR]-with refer to FIG. 1 (any grades with 10.0 to 60.0 mole % of epoxide contents) are used as the solid rubber host.

(19) 5.0 to 60.0 p.p.h.r. of carbon blacks (include grades of either reinforcing or semi-reinforcing or non-reinforcing or conductive blacks, all in either single or combination form of application) are used as the only electrically conductive fillers.

(20) 0.1 p.p.h.r to 10.0 p.p.h.r. of vulcanisation agents (selected from either sulfur or peroxide), 0 to 10.0 p.p.h.r. of vulcanisation accelerators, 0 to 12.5 p.p.h.r. of vulcanisation activators and 0 p.p.h.r. to 20.0 p.p.h.r. of vulcanisation coagents are used as the ingredients for all solid ENR based blends vulcanisation purpose.

(21) 0.1 to 20.0 p.p.h.r. of antioxidants (either staining or non-staining grades, all in either single or combination form of application) are included into all blends in the hope to enhance their oxidation resistance.

(22) 1.0 p.p.h.r. to 60.0 p.p.h.r. of processing oils (include types of either natural or synthetic oil, in either single or combination form of application) are added into all blends as processing aid in order to enhance the processability.

(23) 0.05 to 20.0 p.p.h.r. of processing waxes (include types of either natural or synthetic wax, in either single or combination form of application) are also added into all blends as processing aid in order to enhance the processability and dispersion level of the carbon blacks within the solid ENR host matrixes.

(24) 0 to 35.0 p.p.h.r. of whitening agents (either in solid or liquid form) are added for adjusting the level of black colour of the ENR based blend.

(25) Internal mechanical mixing device (with refer to FIG. 2) is a general rubber or polymer processing device, which includes of some main structures in a closed system, i.e. a controllable moving (up and down movements) ram, a pair of rotating rotors (with controllable rotating speed) and equipped with a heating system in order to control the mixing chamber's temperature. Size of the device is varied and depends on the amount of material that is processed.

(26) Open milling device (with refer to FIG. 3) is a general rubber processing device, which includes of main structures, i.e. two or more of counter or co-rotating rollers in an open system and is equipped with a heating system in order to control the rollers surfaces temperature. Size of the device is varied and depends on the amount of material that is processed.

(27) Both open milling device and internal mechanical mixing device may be used independently or in any combination thereof.

(28) The invention now being generally described, the same will be better understood by reference to the following detailed examples which are provided for purposes of illustration only and are not to be limiting of the invention unless so specified.

EXAMPLE 1

(29) Formulation of Electrically Conductive Sulfur-vulcanised Epoxidised Natural Rubber [ENR]-Carbon Black Blends

(30) Vulcanised ENR-carbon black blend with various compositions of carbon black filler are prepared for the antistatic footwear application feasibility study (based on their selected electrical and physical properties). Examples of formulation for preparing the vulcanised ENR-carbon black blends are shown in Table 1.

(31) TABLE-US-00001 TABLE 1 Formulations of Electrically Conductive Sulfur-Vulcanised Epoxidised Natural Rubber-Carbon Black Blends Part per hundred rubber [p.p.h.r.] Raw material/ Blend Blend Blend Blend Blend Blend Blend chemical 1 2 3 4 5 6 7 ENR 50 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Carbon black-XC 72 5.0 20.0 30.0 15.0 10.0 5.0 10.0 Carbon black-N330 0.0 0.0 0.0 10.0 30.0 50.0 50.0 Oil-Nytex 840 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Paraffin wax 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Titanium dioxide 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Antioxidant-Permanax 1.0 1.0 1.0 1.0 1.0 1.0 1.0 WSL 1.6 1.6 1.6 1.6 1.6 1.6 1.6 Accelerator-Santocure 5.0 5.0 5.0 5.0 5.0 5.0 5.0 NS Zinc oxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Stearic acid 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Sulfur

(32) 100.0 p.p.h.r of solid epoxidised natural rubbers (i.e. ENR 50 grade with 50.03.0 mole % of epoxide contents) are used as the only rubber host.

(33) 5.0 to 60.0 p.p.h.r. of carbon blacks, include grades of reinforcing [N330] and conductive black [XC 72] in either single or combination form of application are used as the only electrically conductive fillers.

(34) 2.0 p.p.h.r. of sulfurs are used as the vulcanising agent and 1.6 p.p.h.r. of Santocure NS (N-t-butyl-2-benzothiazole sulfenamide) as the favourable vulcanisation accelerators. Both 5.0 p.p.h.r. of zinc oxide and 2.5 p.p.h.r. of stearic acid are added as the vulcanisation activators.

(35) 1.0 p.p.h.r. of Permanax WSL (alpha-1-methyl cyclohexyl derivative of selected xylenols) is added as the antioxidant (a non-staining grade).

(36) 5.0 p.p.h.r. of Nytex 840 processing oil (a type of naphthenic synthetic processing oil) and 0.5 p.p.h.r. of paraffin wax are added as the processing aids.

(37) 5.0 p.p.h.r. of titanium dioxides are added as the whitening agent. The titanium dioxides used are in solid powder form.

EXAMPLE 2

(38) Preparation of Electrically Conductive Sulfur-vulcanisation System Containing Epoxidised Natural Rubber [ENR]-Carbon Black Blends by Using Internal Mechanical Mixing Method

(39) For the first stage of mixing, ENR-carbon black masterbatches with different proportions [in p.p.h.r.] of carbon blacks, Nytex 840, paraffin wax, Permanax WSL, zinc oxide and stearic acid (accordingly to the formulation as shown in Table 1 of Example 1) are prepared by using an internal mechanical mixing device (with refer to FIG. 2). A fill factor of 0.70 (from the total free volume of an internal mechanical mixing device's mixing chamber) is used to perform all mixings. The starting temperature for each mixing is 70 C. The rotor speed is 100 rounds per minute. Stages of each mixing are described in Table 2:

(40) TABLE-US-00002 TABLE 2 First Stage of Preparation of ENR-Carbon Black Masterbatches by using the Internal Mechanical Mixing Method Stage of mixing Timing 1. Addition of ENR 0.sup.th minute 2. Addition of carbon blacks, 2.sup.nd minute processing oil, wax, antioxidant and activators to produce masterbatch 3. Discharge of masterbatch 6.sup.th minute (Total time = 6 minutes)

(41) For the second stage of mixing, 2.0 p.p.h.r. of sulfurs, 1.6 p.p.h.r. of Santocure NS and 5.0 p.p.h.r. of titanium dioxides are added to each of the ENR-carbon black masterbatches (with 5.0 to 60.0 p.p.h.r. of total carbon black) on a two-roll open milling device (with refer to FIG. 2) at temperature 30 C., with the nip's gap distance is adjusted to 20.2 mm. Each of the produced sulfur-vulcanisation system containing ENR-carbon black blends is then removed from the two-roll open milling device after 6 minutes of total mixing period. Prolonged mixing is not recommended at this stage in order to prevent premature vulcanisation.

EXAMPLE 3

(42) Preparation of Electrically Conductive Sulfur-vulcanisation System Containing Epoxidised Natural Rubber [ENR]-Carbon Black Blends by Using Open Milling Method

(43) ENR-carbon black blends with different proportions [in p.p.h.r.] of carbon blacks, Nytex 840, paraffin wax, Permanax WSL, zinc oxide, stearic acid, sulfur, Santocure NS and titanium dioxide (accordingly to the formulation as shown in Table 1 of Example 1) are prepared directly by using a two-roll open milling device (with refer to FIG. 3). The starting temperature for each mixing is 30 C. with the nip's gap distance is adjusted to 20.2 mm. Stages of each mixing are as described in Table 3:

(44) Each of the sulfur-vulcanisation system containing ENR-carbon black blends is then removed from the two-roll open milling device after 16 minutes of total mixing period. Prolonged mixing shall be avoided in order to prevent premature vulcanisation.

(45) TABLE-US-00003 TABLE 3 Stages of Preparation of Sulfur-Vulcanisation System Containing ENR-Carbon Black Blends by using the Open Milling Method Stage of mixing Timing Stage 1: 1. Addition of ENR 0.sup.th minute 2. Addition of carbon blacks, 2.sup.nd minute processing oil, wax, antioxidant and activators to produce masterbatch Stage 2: 3. Addition of sulfur, accelerator and 10.sup.th minute whitening agent to produce blend 4. Discharge of blend 16.sup.th minute (Total time = 16 minutes)

EXAMPLE 4

(46) Preparation of Electrically Conductive Sulfur-vulcanised Epoxidised Natural Rubber [ENR]-Carbon Black Blends

(47) Each of the sulfur-vulcanisation system containing ENR-carbon black blends is prepared accordingly to Examples 1, 2 and 3. Appropriate amounts (varied with the targeted application and testing) of each of the sulfur-vulcanisation system containing ENR-carbon black blends are cut and fed into a mould (dimension of the mould is also varied with the type of targeted application and testing). The mould together with the sulfur-vulcanisation system containing ENR-carbon black blend are sent for vulcanisation by using an electrical hot press machine with heating temperature 1502 C., pressure 60 psi and duration based on the T.sub.c90 (curing time to at least 90% of curing level) of each blend (as measured by a Monsanto's moving die typed rheometer). The T.sub.c90 values of blends prepared by using the internal mechanical mixing method and open milling method are reported in Table 4 and 5 respectively.

(48) TABLE-US-00004 TABLE 4 T.sub.c90 of Sulfur-Vulcanisation System Containing ENR- Carbon Black Blends (Vulcanised at Temperature, 150 2 C.) prepared by using the Internal Mechanical Mixing Method (according to Examples 1 and 2) ENR-Carbon Black Blend T.sub.c90 (minute) Blend 1 6.20 Blend 2 5.31 Blend 3 5.20 Blend 4 5.25 Blend 5 5.08 Blend 6 4.98 Blend 7 4.95

(49) TABLE-US-00005 TABLE 5 T.sub.c90 of Sulfur-Vulcanisation System Containing ENR-Carbon Black Blends (Vulcanised at Temperature, 150 2 C.) prepared by using the Open Milling Method (according to Examples 1 and 3) ENR-Carbon Black Blend T.sub.c90 (minute) Blend 1 6.32 Blend 2 5.41 Blend 3 5.29 Blend 4 5.35 Blend 5 5.20 Blend 6 5.07 Blend 7 5.02

EXAMPLE 5

(50) Electrical and Physical Properties of the Sulfur-vulcanised Epoxidised Natural Rubber [ENR]-Carbon Black Blends

(51) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (as described in Examples 2 and 4) or open milling method (as described in Examples 3 and 4) have the orders of electrical volume resistance (measured using 2-probe technique with a Keithley 6157A Electrometer) as summarised in Table 6 and 7 respectively, which rendered the material suitable for antistatic footwear application and manufacturing.

(52) TABLE-US-00006 TABLE 6 Orders of electrical volume resistance value (Ohms) for Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) Electrical Volume Resistance ENR-Carbon Black Blend Order (Ohm) Blend 1 10.sup.10 Blend 2 10.sup.3 Blend 3 10.sup.1 Blend 4 10.sup.4 Blend 5 10.sup.5 Blend 6 10.sup.5 Blend 7 10.sup.4

(53) TABLE-US-00007 TABLE 7 Orders of electrical volume resistance value (Ohms) for Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) Electrical Volume Resistance ENR-Carbon Black Blend Order (Ohm) Blend 1 10.sup.10 Blend 2 10.sup.3 Blend 3 10.sup.1 Blend 4 10.sup.4 Blend 5 10.sup.5 Blend 6 10.sup.5 Blend 7 10.sup.4

(54) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (described in Examples 2 and 4) or open milling method (described in Examples 3 and 4) exhibit Shore A hardness values as shown in Table 8 and 9 respectively.

(55) TABLE-US-00008 TABLE 8 Shore A Hardness Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) ENR-Carbon Black Blend Hardness (Shore A) Blend 1 41 1 Blend 2 55 1 Blend 3 63 1 Blend 4 59 1 Blend 5 70 1 Blend 6 75 1 Blend 7 79 1

(56) TABLE-US-00009 TABLE 9 Shore A Hardness Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) ENR-Carbon Black Blend Hardness (Shore A) Blend 1 42 1 Blend 2 54 1 Blend 3 62 1 Blend 4 58 1 Blend 5 70 1 Blend 6 74 1 Blend 7 78 1

(57) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (as described in Examples 2 and 4) or open milling method (as described in Examples 3 and 4) have some main non-aged tensile properties (measured according to the standard, i.e. ISO 37) as shown in Table 10 and 11 respectively.

(58) TABLE-US-00010 TABLE 10 Non-Aged Tensile Properties of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) Tensile ENR-Carbon Black Blend Strength (MPa) Elongation at Break (%) Blend 1 18.0 0.5 456.5 30.0 Blend 2 23.8 0.5 617.2 30.0 Blend 3 24.2 0.5 619.8 30.0 Blend 4 22.0 0.5 522.7 30.0 Blend 5 20.5 0.5 497.3 30.0 Blend 6 19.8 0.5 505.7 30.0 Blend 7 20.7 0.5 515.4 30.0

(59) TABLE-US-00011 TABLE 11 Non-Aged Tensile Properties of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) ENR- Carbon Black Blend Tensile Strength (MPa) Elongation at Break (%) Blend 1 17.6 0.5 446.3 30.0 Blend 2 23.2 0.5 605.0 30.0 Blend 3 23.9 0.5 610.3 30.0 Blend 4 21.5 0.5 513.2 30.0 Blend 5 20.1 0.5 485.5 30.0 Blend 6 19.2 0.5 497.7 30.0 Blend 7 20.3 0.5 507.5 30.0

(60) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (as described in Examples 2 and 4) or open milling method (as described in Examples 3 and 4) show crescent tear strength values (measured according to the standard, i.e. ISO 34) as reported in Table 12 and 13 respectively.

(61) TABLE-US-00012 TABLE 12 Crescent Tear Strength Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) ENR-Carbon Black Blend Tear Strength (N/mm) Blend 1 14.3 1.0 Blend 2 18.4 1.0 Blend 3 26.2 1.0 Blend 4 22.8 1.0 Blend 5 28.5 1.0 Blend 6 31.4 1.0 Blend 7 34.3 1.0

(62) TABLE-US-00013 TABLE 13 Crescent Tear Strength Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) ENR-Carbon Black Blend Tear Strength (N/mm) Blend 1 13.2 1.0 Blend 2 17.5 1.0 Blend 3 25.4 1.0 Blend 4 22.1 1.0 Blend 5 28.2 1.0 Blend 6 31.5 1.0 Blend 7 34.0 1.0

(63) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (as described in Examples 2 and 4) or open milling method (as described in Examples 3 and 4) also show compression set values (measured according to Standard ISO 815 at 30 min) as reported in Table 14 and 15 respectively.

(64) TABLE-US-00014 TABLE 14 Compression Set Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) ENR-Carbon Black Blend Compression Set (%) Blend 1 16.3 1.0 Blend 2 27.8 1.0 Blend 3 28.9 1.0 Blend 4 25.4 1.0 Blend 5 30.0 1.0 Blend 6 33.1 1.0 Blend 7 35.2 1.0

(65) TABLE-US-00015 TABLE 15 Compression Set Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) ENR-Carbon Black Blend Compression Set (%) Blend 1 17.5 1.0 Blend 2 28.9 1.0 Blend 3 29.0 1.0 Blend 4 26.5 1.0 Blend 5 31.0 1.0 Blend 6 34.4 1.0 Blend 7 36.0 1.0

(66) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (as described in Examples 2 and 4) or open milling method (as described in Example 3 and 4) also exhibit Dunlop rebound resilience values (measured according to Standard BS 903 Part A8) as reported in Table 16 and 17 respectively. Damping properties of the ENR-carbon black blends always enhanced with their decreasing rebound resilience values.

(67) TABLE-US-00016 TABLE 16 Dunlop Rebound Resilience Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) Dunlop Rebound ENR-Carbon Black Blend Resilience (%) Blend 1 47.8 1.0 Blend 2 42.0 1.0 Blend 3 33.6 1.0 Blend 4 38.6 1.0 Blend 5 28.8 1.0 Blend 6 21.6 1.0 Blend 7 20.8 1.0

(68) TABLE-US-00017 TABLE 17 Dunlop Rebound Resilience Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) Dunlop Rebound ENR-Carbon Black Blend Resilience (%) Blend 1 48.4 1.0 Blend 2 42.5 1.0 Blend 3 34.3 1.0 Blend 4 39.2 1.0 Blend 5 29.3 1.0 Blend 6 22.3 1.0 Blend 7 20.9 1.0

(69) Sulfur-vulcanised ENR-carbon black blends prepared by using either the internal mechanical mixing method (as described in Examples 2 and 4) or open milling method (as described in Examples 3 and 4) show Akron abrasion values (measured according to Standard BS 903 Part A9) as reported in Table 18 and 19 respectively.

(70) TABLE-US-00018 TABLE 18 Akron Abrasion Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Internal Mechanical Mixing Method (according to Examples 1, 2 and 4) Akron Abrasion (mm.sup.3/500 ENR-Carbon Black Blend rev) Blend 1 30 1 Blend 2 25 1 Blend 3 21 1 Blend 4 24 1 Blend 5 14 1 Blend 6 10 1 Blend 7 8 1

(71) TABLE-US-00019 TABLE 19 Akron Abrasion Values of Sulfur-Vulcanised ENR-Carbon Black Blends prepared by using the Open Milling Method (according to Examples 1, 2 and 4) Akron Abrasion (mm.sup.3/500 ENR-Carbon Black Blend rev) Blend 1 31 1 Blend 2 26 1 Blend 3 22 1 Blend 4 24 1 Blend 5 14 1 Blend 6 11 1 Blend 7 8 1

(72) The invention being thus described, it will be apparent that the same may be varied in many ways. Such variations are to be regarded as within the scope of the invention, and all such modifications as would be apparent to one skilled in the art are intended to be within the scope of the following claims.