FIELD OF THE INVENTION

The present invention relates to the field of Polymer technology. More importantly, it relates to rubber composition for an off highway tyre treads using naturally occurring pineapple leaf fibre.

BACKGROUND OF THE INVENTION

As rubbers for a tire tread, rubbers having a high frictional force have been sought from the viewpoint of safety. Recently, the development of green rubber composites has been gaining more interest and attention due to the depleting petroleum reserves and environmental awareness. Natural fibers are the one of green fillers with high strength that can be used to reinforce polymer materials. Short and fine pineapple leaf fibers (PALF) have been successfully developed by Amomsakchai’s research group at Mahidol University and have been used to reinforce polypropylene (PP), polyamide (nylon), vulcanizable thermoplastics (Santoprene TM) and also nitrile rubber (NBR) effectively.

US Patent No. 9,896,553 relates to a method for manufacturing a rubber composition with excellent reinforcement properties by improving the dispersibility of fibers in a rubber component when the fibers are added to the rubber, a rubber composition obtained using this method, a vulcanized rubber, and a tire. The method for manufacturing a rubber composition comprising short fibers, comprising a dispersion preparation step for preparing a short fiber dispersion by adding the short fibers into a liquid, a mixed dispersion preparation step for preparing a mixed dispersion by adding at least one dispersant selected from the group consisting of carbon black and inorganic compounds into the short fiber dispersion, a mixing step for mixing the mixed dispersion and rubber latex to prepare a rubbershort fiber mixed solution, and a drying step for drying the rubber- short fiber mixed solution to give a rubber composition. This patent discusses about the various dispersion methods for an effective dispersibility of fibers in a rubber component. Also, dried rubber latex or any diene rubber latex is used as a base polymer whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition and there is no latex involved for preparing the rubber composition. US Patent No. 8,048,514 relates to a film for an adhesive tape, characterized in that the film contains at least one homopolymer, copolymer, or terpolymer of the propylene and fibers and is monoaxially stretched in the longitudinal direction, wherein the elongation ratio is preferably at least 1:8 and particularly preferably at least 1:9.5. This patent discusses about the preparation of a film to produce an adhesive tape using atleast one homopolymer, co polymer, or terpolymer of the propylene whereas the present invention discusses about the preparation of an off highway tyre tread compound using NR:BR blend based rubber composition.

US Patent No. 9,695,305 relates to a polyolefin-natural fiber composite composition for extrusion molding, and more particularly to a polyolefin-natural fiber composite composition, which comprises polyolefin resin, natural fiber, thermoplastic elastic rubber and an anhydrous maleic acid-grafted polypropylene -based compatibilizer. This patent discusses about the polyolefin-natural fibre composite. Moreover, butadiene rubber is not used in the preparation of composite whereas the present invention discusses about off highway tyre tread with the NR:BR blend based rubber composition.

US Patent No. 7,582,241 relates to a thermoplastic polymer composition reinforced with fibers such as cellulose or other fillers, particularly from natural sources, and a process for manufacturing the composition are disclosed. The polymer is extruded with a salt which reduces the melting point and pelletized. The pellets are then extruded again with the filler. The composition with the filler can then be melted at the reduced melting temperature to manufacture an article. This patent discusses about the process of reinforcing high temperature melting thermoplastics (e.g., Nylon, PET, PPO, ECM, ABS etc.,) which melt above 200°C with natural fibers start to degrade thermally at or above 200°C whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition to produce an off highway tyre tread.

US Publication No. 20160032086 relates to a rubber composition provided with excellent reinforcement properties by improving the dispersibility of fibers in a rubber component when the fibers are added to the rubber, a method for manufacturing the same, a vulcanized rubber, and a tire. The rubber composition comprises a rubber component and short fibers, wherein the short fibers are cationized. The method for manufacturing the rubber composition, comprises a mixing step for mixing cationized short fibers and rubber latex to prepare a rubber-short fiber mixed solution, and a drying step for drying the rubber- short fiber mixed solution to give a rubber composition. This patent discusses the use of predetermined dispersant to a rubber component in order to improve the dispersibility of short fibres in a rubber composition. Also, dried rubber latex or any diene rubber latex is used as a base polymer whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition and there is no dispersant involved for preparing the rubber composition.

Publication No. US2015315372 (Al) relates to compositions for power transmission belts or hose which utilize environmentally friendly cellulosic reinforcing fibers. The elastomeric or rubber compositions include a base elastomer, polyvinylpyrrolidone, a cellulosic fiber, and a curative. The base elastomer may be one or more selected from ethylene elastomers, nitrile elastomers, and polychloroprene elastomers. The elastomer may be an ethylene-alpha-olefin elastomer. The polyvinylpyrrolidone may be present in an amount of 5 to 50 parts weight per hundred parts of the elastomer. The cellulosic fiber may be one or more selected from kenaf, jute, hemp, flax, ramie, sisal, wood, rayon, acetate, triacetate, and cotton. The cellulosic fiber may be a bast fiber. The cellulosic fiber is present in an amount of 1 to 50 parts weight per hundred parts of the elastomer. A number of other plant fibers have been studied for possible use in composites. The referred patent discusses about the use of cellulosic fibre in ethylene elastomers, nitrile elastomers and polychloroprene elastomers based rubber composition to produce a power transmission belts whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition to produce an off highway tyre tread.

The article entitled “Performance of pineapple leaf fiber-natural rubber composites: The effect of fiber surface treatments” talks about composites of natural rubber (NR) and short pineapple leaf fiber (PALF) prepared on a laboratory two-roll mill. The influences of untreated fiber content and orientation on the processing and mechanical properties of the composites were investigated. The dependence of extent of orientation on fiber concentration was also established. Sodium hydroxide (NaOH) solutions (1, 3, 5, and 7% w/v) and benzoyl peroxide (BPO) (1, 3, and 5 wt % of fiber) were used to treat the surfaces of PALFs. FTIR and scanning electron microscope (SEM) observations were made of the treatments in terms of chemical composition and surface structure. It was found that all surface modifications enhanced adhesion and tensile properties. The treatments with 5% NaOH and 1% BPO provided the best improvement of composite strength (28 and 57% respectively) when compared with that of untreated fiber. The PALF-NR composites also exhibited better resistance to aging than its gum vulcanizate, especially when combined with the treated fibers [Lopattananon, Natinee & Panawarangkul, Kuljanee & Sahakaro, K & Ellis, Bryan; Journal of Applied Polymer Science. 102. 1974 - 1984, 2006]. This technical paper discusses about the use of treated and untreated short pineapple leaf fibre in NR composites to provide better adhesion and physical properties whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition to provide better mechanical properties.

The article entitled “Improving the mechanical properties of short pineapple leaf fiber reinforced natural rubber by blending with acrylonitrile butadiene rubber” proposes a simple method for improving the rubber to filler stress transfer in short pineapple leaf fiber-reinforced natural rubber (NR). This was achieved by replacing some of the non-polar NR by polar acrylonitrile butadiene rubber (NBR). The amount replaced was varied from 0% to 20% by weight. The mixing sequence was designed so that the fiber would be coated with polar NBR before being dispersed in the NR matrix. A comparison system in which the mixing was carried out in a single step was also examined. Despite the fact that the two rubbers are immiscible, it was found that significant improvement of the stress transfer in the low strain region can be obtained. The mixing sequence affected the mechanical properties of the resulting composites. It is concluded that frictional stress transfer between the immiscible rubbers contributes more to the total stress transfer than does the frictional stress transfer between non-polar NR and polar cellulose fiber [Nuttapong Hariwongsanupab, Sombat Thanawana, Taweechai Amomsakchai, Marie-France Vallat, Karine Mougin; Polymer Testing Volume 57, Pages 94- 100, February 2017]. This referred technical paper discusses about the use of short pineapple leaf fibre in NR composites with the partial replacement of polar rubbers like NBR to improve the rubber to filler stress whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition. Moreover, butadiene rubber is non-polar rubber.

The article entitled “Manipulation of mechanical properties of short pineapple leaf fiber reinforced natural rubber composites through variations in cross-link density and carbon black loading” demonstrates that the stress-strain behavior of natural rubber reinforced with short pineapple leaf fiber (PAEF) can easily be manipulated by changing the cross-link density and the amount of carbon black (CB) primary filler. The composites studied here contain a fixed amount of PALF at 10 part (by weight) per hundred rubber (phr) and varying carbon black contents from 0 to 30 phr. To change the cross-link density, the amount of sulfur was varied from 2 to 4 phr. Swelling ratio results indicate that composites prepared with greater amounts of sulfur and carbon black have greater cross-link densities. Consequently, this affects the stress-strain behavior of the composites. Here, the rate of stress increase becomes larger with increasing cross-link density. Hence, we demonstrate that the use of PALF filler, along with the usual carbon primary filler, provides a convenient method for the manipulation of the stress-strain relationships of the reinforced rubber. Such composites can be prepared with a controllable, wide range of mechanical behavior for specific high performance engineering applications [Pitchapa Pittayavinai, Sombat Thanawan, Taweechai Amornsakchaia; Polymer Testing Volume 54, Pages 84-89, September 2016]. This technical paper discusses about the stress-strain behaviour of natural rubber reinforced with pineapple leaf fibre by changing the crosslink density through varying the dosage of sulfur from 2 to 4 phr in the rubber composition whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition.

The article entitled “Mechanical Properties of Natural Composite Containing Pineapple Leaf Fiber, Natural Rubber and Low Density Polyethelene” talks about polymer composite reinforcement exploiting natural PALF, low-density polyethylene (LDPE) and Standard Malaysian Rubber 10 (SMR10). The tensile properties of the composites increase as the fiber loading increases. Moreover, the Young’s modulus or known as tensile modulus increases as the percentage of PALF loading also increased. The results indicated that the rigidity of the composites increased proportionally to the stiffness. Nevertheless, the elongation at break of the composites was inversely proportional towards the stiffness of the composite [Nursyafreena Attan & Norshakinah Nasri; Imperial Journal of Interdisciplinary Research (IJIR) 2032- 2035, Vol-2, Issue-12, 2016]. The referred technical paper discusses about the use of pineapple leaf fibre in LDPE: SMR blend based polymer composite provide high tensile modulus with the increase in dosage of pineapple leaf fibre content whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition.

The article entitled “Development of green natural rubber composites: Effect of nitrile rubber, fiber surface treatment and carbon black on properties of pineapple leaf fiber reinforced natural rubber composites” talks about the effects of nitrile rubber (NBR), fiber surface treatment and carbon black on properties of pineapple leaf fiber-reinforced natural rubber composites (NR/PALF) were studied. The incorporation of NBR and surface treatment of fiber were used to improve the mechanical properties of composites at low deformation, whereas carbon black was used to improve these properties at high deformation. The fiber content was fixed at 10 phr. The composites were prepared using two-roll mill and were cured using compression moulding with keeping the fiber orientation. These composites were characterized using moving die rheometer (MDR), dynamic mechanical thermal analysis (DMTA) and tensile testing. However, reinforcement by fiber reduced the deformation at break. Hence, carbon black was also incorporated into NR/NBR/PALF and NR/surface-treated PALF composites to improve the ultimate properties. By incorporation of carbon black 30 phr in both composites, the mechanical properties of composites were improved and can be controlled at both low and high deformations [Nuttapong Hariwongsanupab; HAL, 2017]. This technical paper discusses about the use of pineapple leaf fibre in NR, NR: NBR based polymer composite and surface treatment of fiber were used to improve the mechanical properties of the composites at low deformation whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition to provide better abrasion resistance.

The article entitled “Development of green natural rubber composites: Effect of nitrile rubber, fiber surface treatment and carbon black on properties of pineapple leaf fiber reinforced natural rubber composites” talks about composites made from styrene-butadiene rubber and short fibers prepared by mixing. The influence on the vulcanization process and tensile strength properties has been studied and compared with compounds filled with carbon black. In this study, the primary objective was to examine the effect of the ratio of short fibers on the curing/rheological characteristic and tensile properties of styrene-butadiene rubber. The presence of fibers gave shorter curing time and led to a slight increase in tensile strength but decreased the elongation at break of the compound [Natalia Meissner, Wladyslaw M. Rzymski, AUTEX Research Journal, 40-43, Vol. 13, No 2, June 2013]. The referred technical paper discusses about the composites made from styrene butadiene rubber and short fibers to study the influence of vulcanization process and tensile strength whereas the present invention discusses about the use of pineapple leaf fibre in NR:BR blend based rubber composition to produce an off highway tyre tread to provide better abrasion resistance.

In view of the above prior arts it is clear that natural fibers have been used with rubber or vulcanized rubber or with other compositions to improve mechanical or tensile property of the composition. However, no rubber composition of natural rubber- butadiene rubber blend with naturally occurring pineapple leaf fibre is available for providing high physico-mechanical properties. Hence, the present invention aims to provide rubber composition for an off highway tyre treads using naturally occurring pineapple leaf fibre. OBJECT OF THE INVENTION

Principal object of the present invention is to provide rubber composition for an off highway tyre treads using naturally occurring pineapple leaf fibre.

Yet another object of the present invention is to provide rubber composition capable of providing better physical properties.

Yet another object of the present invention is to provide better abrasion resistance.

Yet another object of the present invention is to provide better cut and chip resistance.

Yet another object of the present invention is to provide better wet and dry grip.

SUMMARY OF THE INVENTION

One or more problems of the conventional prior arts may be overcome by various embodiments of the present invention.

It is a primary aspect of the present invention to provide a rubber composition for off highway tyres, comprising of:

Polymer matrix - 100 phr;

Reinforcing fillers - 0-100 phr;

Coupling agent - 0-2.5 phr;

Tackifier - 1 - 5 phr;

Activators - 1.5 - 10 phr;

Anti-degradant - 1.5 -4.5 phr;

Anti-oxidant - 1.0 - 2.5 phr;

Process aid - 1-15 phr;

Accelerators - 0.1 - 2.7 phr;

Vulcanization agent - 1.3 - 2.5 phr; and

Natural fiber - 1- 10 phr, wherein the natural fibre is selected from pineapple leaf fibre (PALF) with the cellulose greater than 60% and lignin greater than 3%, and wherein the length of the PALF is 1-7 mm.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the polymer matrix comprises of rubbers selected from natural rubber - 60-80 parts, polybutadiene rubber - 20-40 parts, and combinations thereof.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the reinforcing fillers are selected from carbon black and precipitated silica, in a weight ratio of 0-80: 0-20 phr.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the coupling agent is bifunctional, sulfur-containing organosilane Si75.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the tackifier is koresin. It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the activators are selected from zinc oxide, stearic acid and combinations thereof, preferably zinc oxide - 1.5 - 5 parts and stearic acid - 1.5 - 4.5 phr.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the anti-degradants are selected from N(l,3-dimethyl-butyl)-N’- phenylenediamine (6PPD) - 1.5 - 4.5 phr.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the anti-oxidants are selected from 2,2,4-trimethyl -1,2-dihydroquinoline (TDQ) - 1.0-2.5 phr.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the process aid is TDAE oil - 2-15 phr.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the accelerators are selected from N-cyclohexyl-2-benzothiazolesulfenamide (CBS), Diphenyl guanidine (DPG) and combinations thereof, preferably CBS - 1.2-2 PHR, and DPG - 0.1 -0.7 phr.

It is another aspect of the present invention to provide a rubber composition for off highway tyres, wherein the vulcanization agent is sulphur.

It is another aspect of the present invention to provide a method for preparation of rubber composition for off highway tyres, comprising of steps: preparation of master batch: step 1 in two roll mill: mastication of rubber at a temperature of 70+2 °C; blending of pineapple leaf fibre with masticated rubber; step 2a for carbon black and silica filled compounds: further mixing of step 1 rubber with pineapple leaf fibre blend in a Banbury mixer and allowed it to mix for 10 to 35 seconds at a temperature of 55-65°C at 55-60 rpm; further addition of the reinforcing filler silica, silane coupling agent Si75 at a temperature of 110 to 125°C at 20 - 30 rpm; further mixing of carbon black, TDAE oil, TDQ, koresin except 6PPD and zinc oxide at a temperature of 130-150°C; dumping of the compound and sheet out;

Step 2b for carbon black and silica filled compounds: mixing of step 1 master batch with zinc oxide and 6PPD at a temperature of 130-145°C and sheet out;

Step 2c for carbon black filled compounds: further mixing of step 1 rubber with pineapple leaf fibre blend in a Banbury mixer and allowed it to mix for 10 to 35 seconds at a temperature of 55-65°C at 55-60 rpm; further addition of reinforcing filler carbon black, TDAE oil, TDQ, Koresin and allowed to mix for 160 to 240 seconds and sweep the orifice; further allowed to mix for another 80 to 120 seconds and the compound has been dumped in the range of 135 to 150°C and sheeted out; step 3: mixing of step 2b or 2c master batch and dumping at the temperature range of 125- 135°C and sheet out, and preparation of final batch: mixing of step 3 master batch and curatives and dumping at a temperature of 95-115°C and sheet out.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 represents the image of pineapple leaf fibre blended with polymers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an off highway tyre tread composition, capable of providing high physico-mechanical properties. The rubber composition of an off highway road tyre tread includes 100 parts per weight of a rubber, 60 to 80 parts by weight of a natural rubber and 20 to 40 parts by weight of a butadiene rubber, a reinforcing filler such as Carbon Black dosage between 0 to 80 parts, a reinforcing filler precipitated silica dosage between 0 to 20 parts, between 1 to 10 parts of a naturally occurring pineapple leaf fibre (PALF) with the cellulose greater than 60% and lignin greater than 3%. Table 1: Rubber Composition in phr

1. Natural Rubber - RSS 3 (Natural Rubber - Ribbed Smoke Sheet) from Southland Global PTE Ltd, Thailand with the Mooney Viscosity, ML (1+4) at 100°C is 72 MU. 2. Polybutadiene rubber - It is from Reliance Industries Ltd, India with the Mooney viscosity, ML (1+4) @ 100°C is 44 MU

3. Carbon black - ASTM grade N110 is from Continental carbon India Ltd, Ghaziabad,

India. It is the reinforcing filler SAF, Superior Abrasion Furnace having the Iodine adsorption No. 140 to 150 mg/gm, tinting strength value between to 118 to 128 % ITRB, statistical thickness surface area value between 114 to 124 m ² /gm

4. Precipitated Silica- Ultrasil VN3 silica from Insilico Ltd, Evonik Industries GmbH, India. It is the reinforcing filler having nitrogen surface area value 170 to 190 m ² /gm

5. Si 75 Bifunctional, sulfur-containing organosilane from Evonik Resource efficiency GmbH, Germany

6. Koresin- It is a high performance tackifier resin. It is from Tech Wax chem Pvt Ltd, WB, India.

7. Zinc Oxide from POCL Enterprises Limited, India. It is an activator added to the rubber compound to activate sulphur vulcanization

8. Stearic acid - from 3F Industries Ltd., India. It is used as a Process aid. Also, Zinc oxide and Stearic acid are added to form zinc soap, improves the solubility of zinc oxide in the compound, and with the accelerator to form a complex, this complex reacts with sulphur to produce a strong cure activating system

9. 6PPD - (N-(l,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine) is an antidegradant from Nocil Limited, India.

10. TMQ (TDQ) - 2, 2, 4 - trimethyll-1, 2-dihydroquinoline (Oligomers) is an antioxidant from Nocil Limited, India

11. TDAE Oil- Treated Distillate Aromatic Extract Oil is a non-carcinogenic mineral oil. It is from Panama Petrochem Ltd, Gujarat, India.

12. Pineapple leaf fibre - Pineapple leaf fibre (PALF) with the cellulose greater than 60% and lignin greater than 3%. It is from Sree ram agencies, Madurai, Tamilnadu.

13. CBS N-cyclohexyl-2-benzothiazolesulfenamide) from Nocil Limited, India. It is a delayed action accelerator suitable for diene rubbers.

14. DPG Diphenyl guanidine from PMC Rubber Chemicals India Pvt ltd, West Bengal, India. It is a secondary accelerator, used to activate the primary accelerator.

15. Sulphur is the vulcanizing agent from The Standard Chemical Co. Pvt Ltd, India.

Mixing Sequence:

Using a mixer of Banbury, a rubber composition prepared by a thermomechanical process is as follows:

Preparation of master batch:

Rubber with Pineapple leaf fibre preparation in Two Roll Mill: Step 1: Rubber is masticated in a two-roll mill with the roll temp 70+/-2 deg C to form a band on roll and then the pineapple leaf fibre with the length of 1 to 7 mm is added into the masticated rubber to attain uniform orientation of pineapple leaf fibre in rubber blend.

For Silica and carbon black filled rubber compounds:

Step 2a: Preparation of masterbatch has been performed with the rotation speed of the mixer between 55 to 60 rpm and with the head temperature of the Banbury maintained between 55 to 65°C a) Mixing chamber has been charged with the step I: rubber + pineapple leaf fibre blend, and allowed to mix for 10 to 35 seconds b) Further by adding, the reinforcing filler silica, silane coupling agent Si75 and allow it to mix upto the temperature between 110 to 125°C c) the process of silanization has been done with the reduced the rotor speed 20 to 30 rpm d) further addition of carbon black, TDAE oil, TDQ, Koresin (except 6PPD and zinc oxide) are added, and allowed to mix and the compound has been dumped in the range of 130 to 150°C and sheeted out in the laboratory two-roll mill.

Step 2b: Mixing chamber of Banbury charged with the Step I master batch, chemicals zinc oxide and 6PPD, and allowed to mix for 120 seconds and dumped in the temperature range of 130°C to 145°C. The compound has been sheeted out in the laboratory two-roll mill.

Carbon black filled Rubber Compounds:

Step 2c: Preparation of masterbatch has been performed with the rotation speed of the mixer between 55 to 60 rpm and with the head temperature of the Banbury maintained between 55 to 65 °C a) Mixing chamber has been charged with the step I: rubber + pineapple leaf fibre blend, and allowed to mix for 10 to 35 seconds b) Further by adding, the reinforcing filler carbon black, TDAE oil, TDQ, Koresin and allowed to mix for 160 to 240 seconds and sweep the orifice d) further allowed to mix for another 80 to 120 seconds and the compound has been dumped in the range of 135 to 150°C and sheeted out in the laboratory two-roll mill.

Step 3: Mixing chamber of Banbury charged with the Step 2b or 2c master batch, and allowed to mix for 120 seconds and dumped at the temperature range of 125 °C to 135°C. The compound has been sheeted out in the laboratory two -roll mill.

Preparation of Final Batch: Mixing chamber charged with the Step 4 master batch and the curatives and allowed to mix for 50 to 80 seconds and dumped at the temperature range of 95°C to 115°C. Final sheet out has been done in the laboratory mill. Results:

Table: 2 Characterization of Cured Rubber Vulcanizate and Uncured Rubber Compound: Table 3: Characterization of Cured Rubber Vulcanizate and Uncured Rubber Compound:

Results

Measurements and tests (Table 2):

The purpose of these tests is to measure the improved properties of the tyre tread rubber composition related to the invention against control tread rubber composition. For this, rubber composition Fl is prepared based on NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler containing 5 phr of pineapple leaf fibre against rubber composition Cl based on NR: PBR (75 phr: 25 phr) diblend reinforced by carbon black are prepared and evaluated.

The present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler containing 5 phr of pineapple leaf fibre provide higher hardness i.e., Shore A value improved by 11.29% when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black. Also, The present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend based rubber composition reinforced by carbon black filler containing 5 phr of pineapple leaf fibre provide higher 100% and 300% modulus value improved by 10.66% and 4.04% respectively when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black.

The present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler containing 5 phr of pineapple leaf fibre provide lower abrasion loss i.e., abrasion resistance (wear resistance) improved by 14.78% when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black.

The present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler containing 5 phr of pineapple leaf fibre provide lower weight loss and diameter reduction (i.e., better cut and chip resistance) improved by 19.54% & 30.43% when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black.

Results

Measurements and tests (Table 3):

The purpose of these tests is to measure the improved properties of the tyre tread rubber composition related to the invention against control tread rubber composition. For this, rubber composition F2 is prepared based on NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler and silica filler containing 5 phr of pineapple leaf fibre against rubber composition C2 based on NR: PBR (75 phr: 25 phr) diblend reinforced by carbon black & silica filler are prepared and evaluated.

The present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler and silica filler containing 5 phr of pineapple leaf fibre provide higher hardness i.e., Shore A value improved by 6.25 % when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black filler and silica filler. Also, the present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend based rubber composition reinforced by carbon black filler containing 5 phr of pineapple leaf fibre provide higher 100% modulus value improved by 11.47% and 300% modulus provide comparable value when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black filler and silica filler.

The present invention provides a 100 parts by weight of rubber composition Fl, NR: PBR (75 phr :25 phr) diblend rubber composition reinforced by carbon black filler and silica containing 5 phr of pineapple leaf fibre provide higher tan delta value at 0 deg C and 25 deg C which results that wet grip and dry grip property improved by 4.10 % and 4.37% when compared to NR: PBR (75 phr: 25 phr) blend based rubber composition reinforced by carbon black filler and silica filler.

Overall, the present invention provides a 100 parts by weight of rubber composition, NR: PBR (75 phr: 25 phr) diblend based rubber composition reinforced by carbon black containing 5 phr of pineapple leaf fibre provides higher hardness, higher 100% and 300% modulus, better wear abrasion resistance (wear resistance) and cut and chip resistance. Also, the present invention provides a 100 parts by weight of rubber composition, NR: PBR (75 phr: 25 phr) diblend based rubber composition reinforced by carbon black and silica filler containing 5 phr of pineapple leaf fibre provides higher hardness, higher 100% and comparable 300% modulus, better wet grip and dry grip property.

Characterization of Rubber Vulcanizate:

The resulting vulcanized rubber compositions shall be evaluated for

Measurements and Tests:

Ml. Shore A Hardness of the Rubber Vulcanizate:

Shore A Hardness of the Rubber Vulcanizate is assessed in accordance with ASTM D 2240.

M2: Physical properties 100% modulus & 300 % modulus are measured in accordance with ASTM D 412 using universal testing machine Instron make.

M3: Abrasion loss in mm ³ is measured using Din Abrader in accordance with ASTM D 5963. M4: Cut and chip resistance of the rubber vulcanizate is measured to understand the relative service life of the off highway tyre subjected to uneven terrains (i.e., to predict service performance of the tyre tread that are subjected to contacting surfaces containing sharp objects such as rocks, gravels etc.,) using Goodrich Cut and Chip Tester. Cutting takes place when the tyre tread hits a sharp object with the sufficient force that the surface is cut, creating a new surface area. Chipping follows cutting and involves fracturing away of a piece of rubber from the surface. Test specimen Speed: 760 rpm; Cut chip cycle-Frequency: 60HZ; Test cycle - 10 Minutes. Weight loss and diameter reduction are measured after 10 minutes of test time.

M5. Dynamic properties/Visco elastic properties of the Rubber vulcanizate:

The dynamic properties of the rubber vulcanizate are measured on a dynamic mechanical analyzer (DMA Metravib +1000) in tension mode with the temperature sweep -40 to 100 °C, Dynamic strain: 0.3%, Static strain:0.6%, Frequency: 10 Hz. Tan delta at 0°C is a predictor for wet grip (Higher tan delta value at 0 °C is good for wet grip property) and tan delta at 25 °C is a predictor for dry grip (Higher tan delta value at 25 °C is good for dry grip property).