19 August 2010

Tyre Sidewall Compounding

OPTIMIZATION OF PROPERTIES IN TRUCK TYRE SIDEWALL COMPOUND


Vishnu Das






CONTENTS

Page No

1. Scope of present study 2

2. Abstract 3

.

I. INTRODUCTION

1. Tyre 4

2. Side wall 8

II. MATERIALS USED

Raw material used & their specifications 9

III. COMPOUNDING

1. Formulations 23

2. Mixing 24

IV. MOULDING AND TESTING

1. Moulding and vulcanization 25

2. Testing 26

V. TABLES AND GRAPHS

1. Tables 36

2. Graphs 40

VI. RESULTS AND DISCUSSIONS

Comparison of result 47

VII. CONCLUSION 51

VIII. REFFERENCE 52

SCOPE OF PRESENT STUDY

The main objective of this work is to reduce the side wall manufacturing cost by replacing some amount of NR with SBR, without affecting the processing, physical properties and product performance.

PRICE OF RAW RUBBERS in 2009 (Rupees per quintal)

Month

NR (RSS 4)

PBD

SBR-1502

January

7034

-

-

February

6903

-

-

March

7583

-

-

April

9488

10000

8512

May

9805

-

-

June

9913

-

-

July

9819

-

-

August

10250

-

-

September

10651

-

-

October

10898

-

-

November

11302

-

-

December

13430

9876

8569


ABSTRACT

The aim of this project is to reduce the amount of NR in the side wall compound and to minimize the cost.

For this purpose, from the presently used NR/ BR compound , 10 phr of NR is replaced with 10 phr of SBR.

In order to obtain good processing and physical properties various concentration of accelerator were studied and optimum quantities were found out.


Introduction

Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 450 tire factories in the world. Over 1 billion tires are manufactured annually, making the tire industry the majority consumer of natural rubber. Tire factories start with bulk raw materials such as rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured. Tyre cost is one of the major components and the measures taken to control the cost therefore can contribute significantly to the profitability. (1) tyre durability; (2) tyre retreadability and (3) tyre mileage to derive the best from the tyre. Usually these three parameters can be clubbed to form an index of measurement of tyre performance known as ‘cost per kilometer (cpkm).

A Pneumatic Tyre is a toroidal shaped flexible high performance composite membrane capable of containing air or fluid under pressure when mounted on a suitable rim

The basic functions of a pneumatic tyre

  1. Load carrying capacity
  2. Transmit driving and breaking torque
  3. Produce cornering force
  4. Provide cushioning ability
  5. Road holding ability
  6. Provide dimensional stability
  7. Provide adequate mileage
  8. Provide flexation
  9. Provide steering force or response of steering
  10. Minimum noise and vibration

Basic Tyre Types

1. Bias angle or cross ply tyre

In this construction reinforcing cords extend diagonally across the tyre from bead to bead. The bias angle of the cord path to the center line of the tyre is generally in the range of 25 to 40 degrees. The cords run in opposite directions in each successive lyres (or ply) of the reinforcing material , resulting in a criss-cross pattern. This type has been a standard construction for years.

2. Radial tyre

In this construction, the plies of reinforcing cords extend transversely from beads to bead. On top of the plies (under the tread) is an inextensible belt composed of several layers of cords. The belt cords are low angle (10 to 30 degrees) and act to restrict the 90 degree carcass plies .Increased sidewall bulging is characteristic of radial tyres.

3. Bias \ Belted tyre

Which consists of a bias angle carcass with a circumferentially restricting belt . In The bias\belted tyre the carcass angle is generally maintained between 25 and 45 degrees and the belt angle between 20 and 35 degrees. In addition, the angle of the belt is about 5 degrees less than the angle of the carcass.


Tyre Components

Parts of a Bias Tyre

Tread

The desirable characteristics are very good abrasion resistance with lowest heat development, good resistance to cuts and bruises and better handling characteristics like no skidding.

Separate cap and base compounds are used to achieve very good abrasion resistance at optimum heat development. The gauges of the tread are decided by the Non skid depth (NSD) and the under tread (UT). The NSD represents the wearing portion of the tyre – linked to tyre mileage and tread shuffling. The tread pattern is characterized by the geometrical shape of the grooves, lugs, voids and sipes .It is generally compounded from NR and / or blend of SBR ( Resistance to abrasion ) , PBD(provide good rebound property) ,mixed with carbon black ,oils , curative ingredients and other chemicals

Sidewall

To protect the carcass from external injuries and moisture (the moisture can hrdrolyse and damage the nylon carcass or rust a steel tyre cord. The most exposed portion of the tyre. The desirable characteristics are very good flex resistance, resistance to cracks, very good ageing characteristics – Resistance to oxidants and ozone. Normally made of synthetic rubbers (PBD) with good weathering characteristics. Sidewall is fabricated in a form of rubber layer of appropriate thickness by extrusion process

Plies

Deciding factor is the load carrying capacity and the tyre inflation pressure. The number of layers is decided based on the inflation pressure, bias angle, optimum modulus gradation and the constructional constraints like single bead or twin bead construction etc. from inner plies to outer plies to the breaker and then to the tread there shall be gradual reduction in the modulus to reduce interface strain and hence to avoid tyre failures This gradual reduction in the modulus necessitates for different EPI’s for inner and outer plies, lower denier and lower EPI for breaker.

The coating of rubber on the plies is to absorb the shear strain between the layers and to prevent cutting between the cords. The number of plies are selected based on the carcass safety factor calculation or the single cord tension calculation. The deciding factors are the contained volume of the tyre, inflation pressure and the carcass construction

Breakers

These are short plies EPI (end per inch) cut an angle and are positioned between the tyre casing and tread to strengthen carcass against impact. They also provide cushioning effect and increase the modulus of tread area. They are also made by rubberizing dipped fabric on calendar and cutting them by cutting machine.

Bead

Holds the tyre on to the rim, consists of bead wire High tensile steel wire copper or bronze coated to bond rubber to steel and to prevent rusting of bead wires. The number of beads and bead turns and strands is decided based on the bead safety factor calculation, decided by the tyre gauges, dimensions, the inflation pressure and processing and assembling constraints.

Bead Wrap

It is the rubber or rubberized thin cross woven fabric strip wrapped around the insulated bead to bind them firmly.

Bead Apex

The apex is a triangular extruded profile that mates against the bead. The apex provides a cushion between the rigid bead and the flexible inner liner and body ply assembly. Alternatively called "filler"

Chaffer

To prevent chaffing of the plies against rim. and prevent the penetration of moisture and dirt into the tyre.

Squeegee

Protects the tube from ply cords and also protects the carcass from the moisture in the air contained in the tube. Usually made of higher green strength compounds.

Belt

Belts are calendared sheets consisting of a layer of rubber, a layer of closely-spaced steel cords, and a second layer of rubber. The steel cords are oriented radially in radial tire construction, and at opposing angles in bias tire construction. Belts give the tire strength and dent resistance while allowing it to remain flexible. Passenger tires are usually made with two or three belts.


Tyre sidewall

Principal task of compounding is concerned with securing and acceptable balance between the demands arising from these 3 considerations namely “properties”, “price” & “processing”.

The sidewall is the part of the tire that bridges between the tread and bead. The sidewall is reinforced with rubber and fabric plies that provide for strength and flexibility. The sidewall transmits the torque applied by the drive axle to the tread in order to create traction. The sidewall, in conjunction with the air inflation, also supports the load of the vehicle. Sidewalls are molded with manufacturer-specific detail; government mandated warning labels, and other consumer information

Sidewall is formulated to have excellent flex fatigue resistance for crack initiation and growth and minimum deterioration in properties on ageing. It should also have good flex life and must have adequate strength and toughness to resist road shocks and service abuse. Compounding involves synthetic base using SBR, PBD,NR blend.

Adequate carbon black reinforcement is employed and high doses of powerful antioxidant/ antiozonents are used in the compound to resist ageing and to improve flex life.


Raw Materials Used.

Ø Raw rubber : Rss- 4, PBD, SBR.

Ø Activator : Zno & stearic acid

Ø Antidegradants : 6PPD & TMQ

Ø Retarder : N-cyclohexyl thio phthalimide

Ø Fillers : HAF, Silica

Ø Accelerators : TBBS, TMTM,DPG

Ø Peptiseres : Pentachloro thio phenol

Ø Tackifers : PF resin

Ø Vulcanizing agent : Soluble & Insoluble Sulphur

Ø Processing aid : Aromatic oil

RAW RUBBER

The selection of the rubber for each part of the tyre is a complicated matter in which the blending of one or more rubbers is common practice to achive the compromise so necessary , because no one rubber is ideally satisfactory in every respect .

Natural Rubber (NR)

Rubber's stress-strain behavior exhibits the Mullins effect, the Payne effect, and is often modeled as hyperelastic. Owing to the presence of a double bond in each repeat unit, natural rubber is sensitive to ozone cracking. Latex is a natural polymer of isoprene (most often cis-1,4-polyisoprene) - with a molecular weight of 100,000 to 1,000,000. Typically, a small percent (up to 5% of dry mass) of other materials, such as proteins, fatty acids, resins and inorganic materials (salts) are found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber". For the mechanical strength requirements of tires, NR is better than SBR or BR and offers excellent tread chipping/chunking resistance with low tire running temperatures and improved rolling resistance. Although more difficult to mix and process, it is very good in downstream processes such as extruding, calendering, and tire building. Although good in chip/chunk-type wear and in severe stress wear, it is usually faster wearing in nominal passenger and truck over-the-road tires. It offers better ice traction and excellent exibility in extreme low temperature service (ie, less than 40ºC). It is by far the preferred rubber for wire belt and textile ply/breaker coat compounds. It also provide good tear strength, abrasion flex resistance nd low heat buildup

Specifications are:-

* Appearance : Brown to Dark brown ribbed sheets

* Mooney viscosity : 85 units

* Dirt % : 0.92

* Ash % : 0.5

* Copper content% : 8 (max)

* Mn content : 10 (max)

* Moisture % : 1 (max)

Styrene-Butadiene Rubber (SBR)

SBR can be produced by both emulsion and solution polymerisation techniques, with the emulsion grades being the most widely used. Emulsion polymerisation yields a random copolymer, but the temperature of the polymerization reaction also controls the resultant properties obtained. ‘Cold’ polymerisation yields polymers with superior properties to the ‘hot’ polymerised types.. Both emulsion and solution polymerised SBR contain about 23% styrene. SBR continues to be used in many of the applications where it earlier replaced natural rubber, eventhough it requires greater reinforcement to achieve acceptable tensile and tear strengths, and durability.

SBR exhibits significantly lower resilience than NR, so that it has a higher heat build-upon flexing.. Due to the unsaturation in the main chain, protection is required against oxygen, ozone and UV light.. Sulphur cures generally require less sulphur (1.5 -2.0 phr) and more accelerator than is normally required to cure natural rubber.


Polybutadiene (BR)

Polybutadiene is produced by solution polymerisation, and one important feature governing the performance of the resultant polymer is the cis 1,4, and 1, 2 vinyl contents. High cis 1,4 polymers (>90%) have a Tg around –90 °C, and hence exhibit excellent low temperature flexibility .They also exhibit excellent resilience and abrasion resistance; unfortunately the high resilience gives poor wet grip in tyre treads, and hence this rubber finds limited use as the sole base for such compounds. As the cis 1,4 content decreases, and 1,2 vinyl content increases, the low temperature properties, abrasion resistance and resilience become inferior.

The polymerisation of butadiene results in a polymer with a narrow molecular weight distribution which can be difficult to break down during mixing and milling, have low inherent tack, and the inherent elasticity of the polymer gives poor extrudability. Peptisers can be used to facilitate breakdown and hence aid processing. Due to the unsaturation present in the main chain, protection is required against oxygen, UV and ozone. Oil resistance is poor and the polymer is not resistant to aromatic, aliphatic and halogenated hydrocarbons. Polybutadiene based compounds can be cured by sulphur. Less sulphur and a higher level of accelerators are required when compared to NR. Compounds based on this polymer only give optimum properties at high filler and oil loadings.

Specifications are:-

* Mooney viscosity : 40 to 48

* Ash content : 0.5 (max)

* Volatile matter : 0.75(max)

Activator

* Zno & stearic acid

Activators are processing additives which support vulcanization, in particular the normal sulphur cure. Actually they should be more correctly called cure activators. The most important inorganic activator is zinc oxide.. They can also enhance filler incorporation and dispersion.

Zinc Oxide and Stearic Acid system assumes dual role, namely peptizing function during Mastication and Activating function during Valcanisation. In the absence of an accelerator, the activators zinc oxide and stearic acid are ineffective in increasing the number of cross-links produced of accelerator used. Zinc oxide can, at reasonable addition levels, also assist with reduction of mould shrinkage values. Specific gravity of Zinc oxide is 5.57 & zinc oxide content is 98%. Specific gravity of stearic acid is 0.84-0.86.

Specification of Zinc Oxide :-

Appearance : Whit powder

Specific gravity : 5.57

Zinc oxide content : 98%

Total sulphur : 0.1 %

Particle size : 0.23t0 0.3 micron

Specification of Stearic Acid:-

Appearance : Dull – coloured flakes

Specific gravity : 0.84 to 0.86

Reinforcing agents

* Carbon black

Carbon black Material consisting essentially of elemental carbon in the form of near-spherical particles coalesced into aggregates of colloidal size, obtained by incomplete combustion or thermal decomposition of hydrocarbons constituents. The main heteroatoms incorporated into the carbon structure are hydrogen, oxygen, and sulfur. Thermal blacks typically contain less than 1% of these heteroatoms, and furnace grades less than 2–3%. The physical properties imparted to a given rubber compound by carbon black are dominated by three factors: 1) the loading of the carbon black, 2) the specific surface area of the carbon black, and 3) the structure of the carbon black.

Carbon black is incorporated into rubber through shear forces generated by adding the carbon black to rubber in an internal mixer or open mill. Once carbon black is mixed into rubber, the resulting filled rubber compound is subjected to processes such as calendering, extrusion, and molding before it is cured to make the finished rubber good.

The addition of carbon black increases the viscosity of the compound, and these increases in viscosity can be correlated with increasing loading of the carbon black, with increasing structure of the carbon black used, and, to a lesser extent, with increasing surface area of the carbon black. These increases in viscosity with carbon black additions obviously change the flow characteristics of the filled compound. It is noted that the typical polymer by itself, when made to flow at low shear rates, will exhibit a shear stress proportional to the shear rate (Newtonian flow), whereas the carbon black–filled polymer results in highly non-Newtonian flow.

Specification of HAF ( N 330 ) :-

DBP Absorption : 102cc / 100 gm

Compressed DBP absorption : 88cc/ 100 gm

Tit strength : 103

Specific Gravity : 108

Ash : 0.75

Accelerators

* TBBS, TMTM, DPG

Accelerators and accelerator systems are chosen on the basis of their ability to control the following processing/performance properties of rubber compounds:

  1. Time delay before vulcanization begins (scorch safety)
  2. Speed of the vulcanization reaction after it is initiated (cure rate)
  3. Extent of the vulcanization after the vulcanization reaction is complete (state of cure)
  4. Other factors such as green stock storage stability, fiber or steel adhesion, and bloom tendency

Compounds classified as primary accelerators usually provide considerable scorch delay, medium-to-fast cure rates, and good modulus development. Compounds classified as secondary accelerators or ultras usually produce scorchy, very fast curing stocks.

Accelerator Classes

Class Response speed Acronyms

Aldehyde-amine Slow

Guanidines Medium DPG, DOTG

Thiazoles Semi-fast MBT, MBTS

Sulfenamides Fast, delayed action CBS, TBBS, MBS, DCBS

Dithiophosphates Fast ZBPD

Thiurams Very fast TMTD, TMTM, TETD

Dithiocarbamates Very fast ZDMC, ZDBC

By proper selection of these accelerators and their combinations, it is possible to vulcanize rubber at almost any desired time and temperature. Of course, the speed of vulcanization is not the same for all polymers. Elastomers that contain 100% unsaturation (i.e., NR, BR) will cure faster with a given vulcanization system than will polymers that contain fewer double bonds such as SBR (85 mol% unsaturation) and NBR (50–75 mol% unsaturation). In these polymers, it is common to use higher accelerator levels and less sulfur. However, the relative relationships between accelerators are similar in all of these elastomers, the sulfenamides provide longer scorch delay, faster cure rates, and higher modulus values. Hence in tyre industry sulfonamide accelerator is using.

Specification of TBBS:-

Specific gravity : 1.29

Melting point : 105- 113 0C

Moisture content : 0.1 % (max)

Ash content @ 750 °C : 0.4 % (max)

Vulcanisation

* Sulphur

Vulcanization is a chemical process where sulfur or other materials form crosslinks in the elastomer and thereby improve the polymer’s mechanical properties. The majority of cure systems in use today involve the generation of sulfur containing cross-links, usually with elemental sulfur in combination with an organic accelerator.

As the cross-link density of the vulcanizate increases (or the molecular weight between cross-links decreases), elastic properties such as tensile and dynamic modulus, tear and tensile strength, resilience, and hardness increase whereas viscous loss properties such as hysteresis decrease. Further increases in cross-link density will produce vulcanizates that tend toward brittle behavior. Thus at higher cross-link densities such properties as hardness and tear and tensile strength plateau or begin to decrease.

Different Types of Sulphur Vulcanisation


SULPHUR

ACCELERATOR

CROSSLINK

C.V

2.5 -to- 3

0.5 -to- 1.2

Polysulphidic

E.V

0 -to- 0.5

1.5 -to- 2.5

Mono / Disulphidic

S.E.V

0.5 -to- 1.2

0.8 -to- 1.5


Property Ratinga

Scorch safety CV > SEV > PV

Faster cure SEV > CV > PV

Heat aging property PV > SEV > CV

Flex fatigue CV > SEV > PV

CV, conventional vulcanization system; SEV, semi efficient vulcanization system; PV, peroxide vulcanization system.

Specifcation of Soluble Sulfur:-

Specific gravity : 2.05

Solubility in CS : 98% (min)

Ash content : 0.1% (max)

Acidity : 0.1 %(max)

Processing Oils

* Aromatic oil

Petroleum oils are offered to the rubber industry to meet two basic processing and compound requirements: to act as a processing additive, or to act as a rubber extender and softener. The classification depends upon the oil volume added to the rubber compound. As processing additives, the oil addition level is usually no more than 5-10 phr; for additions in excess of this the oils are regarded as extenders. All process oils used by the rubber industry are in practice mixtures of all classes of the three components, the mixtures deriving their classification from the preponderance of the main constituent type.

Aromatic - major portion ≥35% Ca

Paraffinic - major portion ≥50% Cp

Naphthenic - major portion ≥30-40% Cn

In general terms, oils of an aromatic preponderance give best processability in general purpose rubbers, such as NR and SBR, but are prone to causing stains, can give poor odour and may contribute to poor ageing resistance. There is a growing awareness that continuous contact with aromatic oils can represent a health hazard.

* Paraffinic oils are less effective as processing additives, but also have less effect upon ageing, giving good colour and contact staining behaviour.

* Naphthenic oils give characteristics midway between the other two types. Oils of the three types are offered in a range of viscosities and this will influence their processing character to some extent

* The temperature influenced rate of change of viscosity is much greater for the aromatic oils than for the paraffinics

The small additions of oil to a compound help with filler dispersion by lubricating the polymer molecular chains and thus increasing their mobility. There will also be some ‘wetting out’ of the filler particles which enables them to achieve earlier compatibility with the rubber and improve their distribution and dispersion speed. Process oils are controlled and marketed, within a molecular type, by viscosity which is influenced by the molecular weight and degree of branching of the molecular chains and the degree of cyclisation and aromaticity.

Viscosity Gravity Constant (VGC)

It is now common to use Viscosity Gravity Constant (VGC) as the criterion for choice of a processing oil. The VGC represents the overall average aromaticity of an oil independent of its molecular weight.

Rubber process oils can be classified using the VGC classification:

* Aromatic - VGC <0.950

* Paraffinic - VGC <0.850

* Naphthenic - VGC <0.850 - 0.900

Specifications are:-

Appearance : Dark coloured oil

Specific gravity @ 60°F : 1.005

Aniliene point : 45

Say bolt viscosity : 125

Antioxidants and Other Protecting Systems

* DPPD, 6PPD ,Wax

To extend the service life of vulcanized rubber goods, it is very important to protect them from oxygen, ozone, light, heat, and flex fatigue. Most natural and synthetic rubbers containing unsaturated backbones—natural rubber (NR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), Antioxidants react with oxygen to prevent oxidation of vulcanized rubber and react with free radicals that degrade vulcanized rubber.

There are four principal theories on the mechanisms of antiozonant protection of vulcanized rubber.

* The first is the scavenger theory, which postulates that the antiozonant competes with the rubber for ozone.

* The second theory is that the ozonized antiozonant forms a protective film on the surface of the vulcanized rubber, preventing further attack.

* The third mechanism postulated is that the antiozonants react with elastomer ozonide fragments, relinking them and essentially restoring the polymer chain.

* The fourth theorized mechanism suggests that Criege zwitterions are formed from the ozonide produced.

The various types of antidegradants are described below.

Resistance to

Type common chemical staining oxygen ozon heat flex use name name

Amine DPPD Dimethyl Very Exc- Mild Exce- Good Tread&

Butyl Para strong Sidewall

Phenylene

Liamine

6PPD Dimethyl Very Exc- Good Exc- Good Sidewall

Pentyl Para strong

Phenylene

Diamine

Wax MC Micro No Nil Exc- Nil Nil Tread&

Wax crystalline Sidewall

Paraffinic waxes generally protect better at low temperatures, Due to the slow migration of microcrystalline wax, it provides longer term static protection from ozone cracking. Blends (paraffin waxe, microcrystalline)offer a wider temperature range of protection. Waxes are used for, only static ozone protection. During dynamic flexing the barrier of wax is exposed owing to breaking of the wax film. Therefore, reactive antiozonants are required for dynamic ozone crack resistance.

The amount of wax addition to a rubber compound will depend upon a number of factors:

  1. the type of rubber being protected
  2. the required appearance of the rubber product
  3. the temperature of service for the component 
  4. the type of service - static or dynamic
  5. the effect of filler type
  6. the effect of process oils
  7. the rate of wax migration to rubber surface
  8. the type of wax being used.

Specification of 6PPD:-

Specific Gravity : 1

Melting point : 47°C

Ash content @ 950 °C : 0.1 (max)

Specification of Wax Blend:-

Specific gravity : 0.91

Drop melting point : 64 – 70 °C

Ashy content @ 950 °C : 0.1% (max)

Tackifers

* Phenol Formaldehyde Resins

Both thermoplastic and thermoset phenol formaldehyde resins find application in rubber compounds. The thermoplastic resins act as excellent tackifiers whilst the thermoset resins act as plasticisers during processing then crosslink to give a reinforcement structure to the compound. Suitable resins for many applications can be tailored by variation in the type of phenol and the ratio of formaldehyde. Lower levels of formaldehyde produce tackifying properties whilst the higher formaldehyde levels contribute, in the presence of hexamethylene tetramine during the rubber cure, to a greater degree of resin polymerisation within the rubber network creating a crosslinked structure which contributes to the hardness and abrasion properties of the compound.

The various types of resin have been discussed above. However, the listings for these materials have been categorised to indicate their prime usage in the industry and have been assigned according to the manufacturers classification:

  1. Homogenising resins
  2. Petroleum resins and proprietary blends
  3. Reinforcing/bonding resins
  4. Resins for adhesives
  5. Tackifier and dispersing resins
  6. Vulcanising resins.

mixing

The key words, homogeneous and dispersion, seem to sum up the principal purposes of most mixing operations: the various ingredients must be dispersed evenly so that the product is the same (homogeneous) everywhere. If the mixer has done a perfect job, each ingredient is evenly intermingled with every other and even the smallest sample taken from any part of the product is identical to any other sample.

The four main components of mixing are

1. Incorporation: Incorporation means each individual particle must be thoroughly wetted and form a coherent mass.

2. Distribution: Incorporated material should be distributed all over the medium.

3. Dispersion: In dispersion the ingredients that are in the form of agglomerates must be broken down into fine individual particles.

4. Viscosity reduction: During mixing, considerable reduction in viscosity of rubber occurs, due to effective molecular break down. Viscosity reduction enhances the processability of rubber.

Due to the partly elastic nature and very viscosity of rubber, power intensive, sturdy machinery like mixing mills and internal mixers are necessary.

Mixing is usually done in two ways

1. Rolling mill mixing.

2. Mixing by internal mixers.

1.Rolling mill mixing.

The rolling mill is furnished with two rolls. The rolls have internal water-cooling. Both roll have slightly different peripheral speeds giving a more efficient mixing. The ratio of the roller speeds is 1:1.2. the power rating is around 200kw with a roll of 20 rpm. Typical mixing cycle takes 30 min. and batch size are 60-79 kg.

At mixing, the mix is following one of the rolls and additives are added in between the two rolls. During mixing the gap is slightly opened. After mixing, the rubber strips is cut in slices and fed in between the rolls, a number of times. This is ensure through mixing.

An important difference between rolling mills and batch mixers is that the former gives a good mix while the latter gives a fast mix. Furthermore, technological opportunities in the rolling mill mixing procedure are nil compared to the internal batch mixers. Automatization is also a hurdle in rolling mill mixers.

2.Internal Mixers

The mixing in a banbury takes place in the gap between the rotor tips and the chamber walls. At the start of the cycle when the polymer is normally in large pieces and the powders are still loose, the initial breakdown and mixing takes place in the large space between the rotors and against the door top. As the material softens, flow over the rotor tips starts to take place but until the viscosity of the mix has fallen sufficiently, most of the work is done between rotors, along the rotor helix angles and between rotors and discharge door top. The area just in front of rotor tip is similar to the nip of a mill, and causes internal shear in the material. The mixer should be cooled to remove heat generated by the mechanical energy of mixing

Temperature recorder having a temperature range of 0-200 and chart speed of 200mm/hr is provided to record the batch temperature on the graph. Carbon black feed is around 0-18 sec, oil addition around 52-62 sec & ram float at 92 sec.




* Mixer Size /Type : 11D BANBURY MIXER

* Chamber Volume : 237 Liters

* Number of wings : 2W

* Discharge Door Type : DROP

* Electrical motor : 415 VOLTS 3 PHASE 50 HZ

BASIC OPERATING CYCLE

* Start Ram up

§ Hopper door open

§ Discharge door closed

* Charge Add ingredients

* Close hopper door

* Ram down

* Mix for required period

* Open discharge door

* Close discharge door Raise ram

* Open hopper door Return to start

Extrusion

Sidewall is made by extrusion technique. After final batch, the mixed compounds are then lead to the extruder. The rubber compound is given continuous shape by forcing it through a die. The extrudate is cooled, cut into specified length and stored

Hot feed extruder of 8 inch size - dedicated for sidewall extrusion

Flow characteristics of rubber is necessary for an understanding of extrusion.

1. Text Box: Shear StressRubbers are strongly non-Newtonian; i.e. the rate of shear deformation is not proportional to the shear stress. The shear rate increases more than proportionality to stresses

2. At any given shear stress, the shear rate increases with temperature.

3. The rate of flow under a fixed stress is time dependent

4. Rubbers show more or less elastic recovery when the deforming stress is remove

Formulation

COMPOUNDING

INGREDIENTS

Regular

H

J

NR

50

40

40

BR

50

50

50

SBR

--

10

10

Silica

15

15

15

HAF

50

50

50

Aromatic Oil

20

20

20

ZnO

5.0

5.0

5.0

6PPD

5.0

5.0

5.0

DAPPD

0.75

0.75

0.75

Stearic Acid

3.5

3.5

3.5

80 mesh crumb

10

10

10

PCTP

0.04

0.04

0.04

PF Resin

4.0

4.0

4.0

Wax

2.5

2.5

2.5

TBBS

0.85

0.9

0.935

Soluble Sulphur

1.5

1.5

1.5

Retarder

0.35

0.35

0.35


Mixing

The mixing was carried out in two stages.

1st stage:

This stage include master batch preparation. Here the black and other compounding except curatives, accelerator, retarder were mixed with rubber. The mixing was done in a 11D internal mixer at 150ºC. The capacity of internal mixer is 237 kgs & the rotor speed has been adjusted to 60 rpm.

2 st stage:

A portion of Master batch along with Curing agents ,accelerators, retarder are mixed in a 11D internal mixer mixer at 118ºC. The capacity of internal mixer is 237 kgs & the rotor speed has been adjusted to 40 rpm. The final batch was done after 24 hrs of ageing the stocks were sheeted out in the open mixing mill(33cm x 15cm) having 1:1.4 friction ratio at a nip of 1/8”. Mixing temperature and time were controlled for all the batches.

MIXING process are accepting on the basis of following tests

Master batches : Specific Gravity, Moony Viscosity.

Final batches : Specific Gravity, Moony Viscosity, Mooney Scorch

and Rheological properties

Moulding & Testing


1. Moulding & Vulcanisation

The Moulding of test specimens were done a steam heated single daylight press (INDEX PELL) with a platen size of 24” X 24” having 12” round size. The mould were preheated to the vulcanization temperature. After mounding the curd sample were cooled upon removal from the mould to room temperature and conditioned at ambient temperature for 24 hrs before testing.

Following test samples were molded for study

v Tensile and tear sample

CURE TIME

TEMPERATURE

60 min

141.7 °C

v Crack initiation and growth samples

CURE TIME

TEMPERATURE

60 min

141.7 °C

v Heat Buildup , Resilience and Abrasion

CURE TIME

TEMPERATURE

60 min

141.7 °C

2. Testing

1. Mooney Viscosity Measurements (ASTM D 1646-81)

Mooney viscosity is defined as the shearing torque resisting rotation of a cylindrical metal disk (or rotor) embedded in rubber within a cylindrical cavity. The test provides information on processability of the compound.The Mooney scorch time, and Mooney viscosity were also determined by using a Monsanto automatic Mooney Viscometer (MV 2000). Condition is ML(1+1.5) at 135°C. The testing procedure was conducted according to the method described in ASTM D 1646-94.

The Mooney Viscometer was the most common tool used to determine the processing characteristics for a given batch of rubber. Many compounders still use the Mooney to verify viscosity (which is indicative of molecular weight) when obtaining raw polymer stock. This works because a compound’s resistance to being moved by the Mooney’s internal rotor is directly linked to its viscosity.

From the chart of the mooney unit v/s time the scorch time can be easily determined by noting the time where the cure turns upwards. A 5 point raise above taken from the mooney cure are

v MV Minimum viscosity

v t5 Time to scorch at Mv + 5 units

v t35 Time to cure at Mv + 35 units

v t1 Cure index which is t35 – t5

Specifications

Standards ASTM-D1646, ISO-289

Rotor Speed : 2 RPM

Graphic Output Curves generated :

· MOONEY viscosity curve

· Scorch curve

· Stress relaxation curve.

· Temperature curve of the upper and lower die

Sample Volume : Two piece test specimen having a combined - volume of 25 ± 3cm3

Temperature 135 °C

2.Rheometer

Rheometer is a versatile instrument used in rubber industry to study curing characteristics of rubber compounds. Basically, it consists of a bi-conical rotor oscillating at desired arc inside in a heated cavity, filled with a rubber compound. The resistance offered to rotor by the compound is measured in terms of torque v/s time. The Rheometer curve give useful information on compound safety, cure rate, optimum cure etc.. From the

data Tc 90, ML, MH, Ts2 of compounds were found out from the plot of torque Vs time , scorch time (Ts2), time for 90% cure (tc 90) and cure rate can be calculated .

There are two main types of Rheometers currently in use: the ODR and the MDR.

ODR

1 Cure rate

Cure rate = MH - ML

Tc 90 – Ts2

Cure rate is the rate at which stiffness (modulus) develops after the scorch point. During this period, compound changes from a soft plastic to a tough elastic material, owing to the introduction of cross-links.

2 Minimum Torque(ML)

It is a measure of the viscosity of the stock at the test temperature. The Rheometer minimum torque is proportional to the Moony Viscosity when both the tests are conducted at same temperature.

3 Maximum Torque(MH)

It is the measure of the stiffness or shear modulus of the the test specimen at the test temperature. It is also an effective measure of the changes in tensile modulus and cross-link density.

4 Induction Time ( Ts2)

It is the time corresponding to 2 unit rise in torque about ML. It is a measure of the time available for mold flow. At lower temperature Ts2 is a processability measure similar to mooney scorch.

5 Optimum Cure ( Tc 90 )

It is the time to achieve 90% of the maximum torque .

Tc 90 = [( MH – ML ) X 90/100] + ML

Rheometer Cure Curve

Monsanto Moving Die Rheometer (MDR – 2000)

It also measure the cure characteristics of the compound. It differs from ODR 2000 in the following respect. In MDR 2000 there is no separate disc, instead the lower half of the die oscillates at 1.66 hz (100 cpm). The reaction torque measured at the upper die correlates with the degree of vulcanization as a function of cure time. The parameters measured from the rheograph are ;

Ø Minimum Torque ( ML )

Ø Maximum Torque ( MH )

Ø Optimum Cure ( Tc 90 )

Ø Tan∂

MDR holds the sample between a pair of heated dies (metal plates forming a cavity). As one of the dies moves across a small arc, the other die gauges the reaction torque generated in the sample. This again results in a cure curve that can show the optimum cure time for the desired blend of properties.

MDR generates 3 curves S’, S" and Tan Delta.The MDR produces a cure curve labeled S’ which is similar to the ODR curve

S’ is called the storage modules, elastic modulus or in phase modulus. S" is called the loss modulus, viscous modulus, or out-of-phase modulus. All of these terms have been used to mean the same thing. The unit of S’ and S" in the product family instruments are in lbs. These are units of torque. They can also be in dnm. Which are also torque units.

Tan∂ = Loss modulus ( S”)

Storage Modulus ( S’)

The smaller the Tan delta, then the more viscous the material.

Specific Gravity

Specific gravity of the compounds was determined according to IS:3400 and compared with theoretically calculated value.

Physical Properties

Tensile properties (ASTM D 412)

Molding

Cure condition 60 min at 141.7 ºC

The final compounds were for 24 hours before molding. The compounds were sheeted out at the required thickness using laboratory mill. Molding was done in a 24” X 24” steam heated automatic press at 141.70 ºC and 75 Kg /sq.cm pressure. The mould pieces were cooled in water and conditioned at 23_+2 and 50% RH for 24 hours before testing.

Equipment:

INSTRON- 4301 Tensile tester with a crosshead speed of 500 mm/ min (ASTM D 412)

Sample preparation :

The test pieces are punched out from the vulcanized sheets, parallel to the mill grain direction. Dumb bell types are most popular whereas ring types test pieces are also used to a limited extent.

Total length : 15mm

Width of ends : 25+_1mm

Width of the narrow parallel portion : 6+_0.4mm

Length of the narrow parallel portion : 33+_2mm


Test:

The test were carried out at 23+_2ºC dumb bell specimens were placed in the grips of INSTRON universal testing machine. Two grips were also there, one inch apart to indicate elongation. There were fixed to the sample in the narrow region. area corresponding to the thickness was fed to the microprocessor. the rate of separation of grip was 20 inch per min. After testing tensile strength, elongation at break, moduli were noted.

Tensile strength:

It is the tensile load per unit cross sectional area of the original cross section within the narrow parallel portion of the test specimen at the point of breakage of the test specimen.

Tensile strength (psi) = load at break

Initial cross sectional area

Modulus:

It is the stress per unit cross sectional area of the original cross section with in the narrow parallel portion pf the test specimen for a particular elongation.

Eg:

300 % modulus (psi) = load at 300% elongation

Initial cross sectional area

Elongation at break:

It is the elongation within the narrow parallel portion of test specimen at the point of breakage of the test specimen expressed as percentage. Elongation describes the ability of the rubber to stretch without breaking.

Elongation at break = length at break- initial length x100

Initial length

Tear strength (ASTM D 634)

The test were carried out at 23+- 2 ºC dumb bell specimens were placed in the grips of INSTRON universal testing machine. Two grips were also there, one inch apart to indicate elongation. These were fixed to the sample in the narrow region. Area corresponding to the thickness was fed to the microprocessor. The rate of separation of the grip was 20 inch per min. after testing tensile strength, elongation at break, moduli were noted. The result is expressed in Kg/cm or lbs/inch instruments.

Tear strength= load required to tear the specimen / specimen thickness

Shore A Durometer Hardness (ASTM D 2240)

Hardness may be defined as a material's resistance to permanent indentation

Shore A hardness is a measure of resistance to the penetration of an indenter of specified size and shape forced in to the test specimen. The hardness is measured in Shore A Hardness units ranging from zero to hundred.

This test method permits hardness measurements based on either initial indentation or after a specified period of time or both.

Test specimen:

The minimum dimensions of the specimen are 30mm diameter, and 6mm thick, tensile pads may be tested for hardness by sticking two pads of similar hardness.

The surface of the specimen must be flat and as free of surface irregularities possible.

Conditional specimen at 23 ºC + 2ºC for a minimum of 16 hours testing.

Procedure

Durometer, like many other hardness tests, measures the depth of an indentation in the material created by a given force on a standardized presser foot. This depth is dependent on the hardness of the material, its viscoelastic properties, the shape of the presser foot, and the duration of the test. ASTM D2240 durometers allows for a measurement of the initial hardness, or the indentation hardness after a given period of time. The basic test requires applying the force in a consistent manner, without shock measuring the hardness (depth of the indentation). If a timed hardness is desired, force is applied for the required time and then read. The material under test should be a minimum of 6.4 mm (.25 inch) thick.

Heat Build Up (ASTM D 623 – 78)

These tests are used to compare the rate of heat generation of different rubber vulcanisates when they are subjected to dynamic compressive strains. The Goodrich Flexometer as per ASTM D 623-78 was used for measuring the property. Tests were carried out with cylindrical samples of 1” hight and 0.7” in diameter. The oven temperaure was kept constant at 50 ºC. The samples were preconditioned to the oven temperature for 15”. The samples were subjected to flexing for 18”. The heat buildup at the base of the sample was relayed to the micro voltmeter. The temperature rise at the end of 18” was taken as the heat buildup.

Resilience (ISO-R-1767)

Standard tests mostly measured the rebound of a pendulum from the rubber test piece

Equipments used:- Lupke Pendulum

Test specimen of 12.5 mm thick was moulded as per specification. In this machine the striker is a steel bar suspended so as to remain horizontal. It was released from a position, 100 above its rest position :- the height of the rebound was measured (usually indirectly from the horizontal return swing ) and expressed as percentage of the 100 mm fall, the result was measured as rebound resilience


Flex Resistance

Crack Initiation (ASTM D 430 - 95 )

Equipments used:- De - Mattia Flexing Machine

After adjustment of the apparatus and specimen is completed, start the machine and record the time. Continue the test until, by frequent inspection, the appearance of the first minute sign off cracking is detected. At this point again record the time. The 1st cracking may be evidenced as either very fine hair line cracks or as slight pin holes. After this time, observe the specimens very closely until the test is discontinued and record the final time.

Crack Growth (ASTM D 813 – 95 )

Equipments used:- De - Mattia Flexing Machine

After adjustment of the apparatus and specimen is completed, start the machine and record the time. At the end of period of operation, calculate the no. of flexing cycles. By multiplying the observed time in minutes by the machine rate of 5 Hz. This shall also be checked by means of a counter on the machine .Since the rate of crack growth is important, take frequent readings early in the test. Stop the machine after 1000, 3000, and 5000 cycle periods, observe the specimens and measure the length of the developed crack to the nearest 0.3 mm with an accurate scale. For improved precision, make the observation with the aid of a low powdered magnifying glass while the grips are separated 65.0 mm (0.5 in) in length is developed. Use a matric scale for measuring crack growth is recommended . The initial cut produced by the puncturing spear is 260.1 mm (0.08+0.002-0.000 in) in width.

Observations

INGREDIENTS

REG.

A

B

C

D

E

F

H

I

J

NR

50

40

40

40

40

40

40

40

40

40

BR

50

50

50

50

50

50

50

50

50

50

SBR

--

10

10

10

10

10

10

10

10

10

Silica

15

15

15

15

15

15

15

15

15

15

HAF

50

50

50

50

50

50

50

50

50

50

Aromatic Oil

20

20

20

20

20

20

20

20

20

20

Zno

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

6PPD

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

DAPPD

0.75

0.75

0.75

0.75

0.75

0.75

0.75

0.75

0.75

0.75

Stearic Acid

3.5

3.5

3.5

3.5

3.5

3.5

3.5

3.5

3.5

3.5

80 mesh crumb

10

10

10

10

10

10

10

10

10

10

PCTP

0.04

0.04

0.04

0.04

0.04

0.04

0.04

0.04

0.04

0.04

PF Resin

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

4.0

Wax

2.5

2.5

2.5

2.5

2.5

2.5

2.5

2.5

2.5

2.5

TBBS

0.85

1.25

1.42

1.59

1.0

1.10

1.20

0.9

0.95

0.935

Sulphur

1.5

1.5

1.5

1.5

1.5

1.5

1.5

1.5

1.5

1.5

Retarder

0.35

0.35

0.35

0.35

0.35

0.35

0.35

0.35

0.35

0.35

REGULAR RHEO : 60 min @ 141.7 ºC

ML

7.96

6.10

6.33

6.74

6.85

6.16

6.51

7.61

6.21

7.55

MH

23.47

26.49

28.52

30.15

24.34

25.50

26.61

24.69

23.35

24.28

tS1

13.17

11.03

11.33

10.95

11.97

11.00

10.78

13.28

11.75

13.23

tS2

16.32

12.42

12.70

12.27

13.85

12.82

12.52

16.18

13.63

16.18

TC15

16.93

13.18

13.62

13.25

14.55

13.68

13.38

17.07

14.23

16.93

TC25

18.90

14.10

14.48

14.10

15.75

14.75

14.40

18.8

15.42

18.73

TC50

22.28

15.72

15.88

15.33

17.93

16.67

16.10

22

17.75

21.98

TC90

30.68

21.55

20.70

19.32

25.62

23.60

22.15

31.20

25.97

31.33

PHYSICAL PROPERTIES ( ORIGINAL )

100% MOD(Psi)

163.8

192.3

214.2

227.7

169.1

182.5

198.1

184.0

158.8

175.8

300% MOD(Psi)

731.4

861.7

981.9

1061

735.8

788.7

869

768.5

681.7

723.7

TENSILE (Psi)

2581

2802

2779

2801

2751

2754

2800

2622

2735

2635

% E.B

676.6

645.8

608.7

588.5

703.5

674.4

648.2

676.6

715

685.4

HARDNESS

52

55

57

58

54

55

56

52

54

50

TEAR

511.4

570.8

438.5

413.5

489.5

493.3

542.1

524.7

518.1

523.4

PHYSICAL PROPERTIES ( AIGED )

100% MOD(Psi)

249.3

--

--

--

267.5

--

--

329.6

251.8

343.9

300% MOD(Psi)

1139

--

--

--

1175

--

--

1261

1122

1156

TENSILE (Psi)

2204

--

--

--

2153

--

--

2199

2109

2212

% E.B

501

--

--

--

482.1

--

--

473.1

480.3

496.7

HARDNESS

55

--

--

--

58

--

--

58

58

57

TEAR

270.7

--

--

--

271.6

--

--

295.5

312.6

264.9

% CHANGE IN PROPERTIES

100% MOD(Psi)

134.28

--

--

--

136.78

--

--

144.2

136.9

127.9

300% MOD(Psi)

135.8

--

--

--

137.37

--

--

139.1

139.2

137.5

TENSILE (Psi)

89.9

--

--

--

72.22

--

--

80.8

70.3

80.8

% E.B

64.9

--

--

--

54.07

--

--

56.9

43.63

62.01

HARDNESS

105.5

--

--

--

106.89

--

--

110.3

106.8

112.3

TEAR

48.0

--

--

--

55.48

--

--

44.0

34.26

49.4

MOONY VISCOSITY:8-16 min @ 135 ºC

ML(1+1.5)

61.81

--

--

--

--

--

--

59.01

--

57.9

MS

15.33

--

--

--

--

--

--

15.71

--

15.19

On comparison, H & J are more similar with regular compound.

Tables and Graphs


1 Tables

1. Mooney viscosity

8-16 min @ 135°C

Samples

ML(1+1.5)

MS

Regular

61.81

15.33

H

59.01

15.71

J

57.90

15.19

2.REGULAR RHEO :

60 min @ 141.7 °C

samples

ML

TS1

TS2

MH

TC15

TC25

TC50

TC90

Regular

7.96

13.17

16.32

21.47

16.93

18.90

22.28

30.68

H

7.61

13.38

16.18

24.69

17.07

18.80

22.00

31.00

J

7.55

13.23

16.18

24.28

16.93

18.73

21.98

31.33

Physical properties;

Determination of Tensile strength of Unaged samples

Cure time: - 141.7 °C for 60 minutes.

Sample

100%

Modulus(psi)

300 %

Modulus(psi)

Tensile strength

(Psi/1n2)

Percentage

elongation

Regular

163.83

731.43

2581

676.6

H

184.03

768.55

2622

676.6

J

175.80

723.75

2635

685.4


Determination of Tensile strength of aged samples

Temperature 100 ºC for 48 hours.

Sample

100%

Modulus(psi)

300 %

Modulus(psi)

Tensile strength

(Psi/1n2)

Percentage

elongation

Regular

249.3

1139.3

2204.5

500.9

H

329.6

1261.0

2199.0

473.1

J

243.9

1156.0

2212.0

496.7

Determination of Tear strength & Hardness of Unaged samples

Cure time: - 141.7 °C for 60 minutes.

SAMPLE

Tear strength(lbs/In)

Hardness Shore A

Regular

511.4

52

H

524.7

52

J

523.4

50

Determination of Tear strength & Hardness of aged samples

Temperature 100ºC for 48 hours.

SAMPLE

Tear strength(lbs/In)

Hardness Shore A

Regular

270.7

55

H

295.5

58

J

264.9

57

Determination of % Change Retention

SAMPLES

100% MOD (Psi)

300% MOD (Psi)

TENSILE (Psi)

% E.B

HARDNESS

TEAR

Regular

134.2

135.8

89.9

64.9

105.5

48.0

H

144.2

139.1

80.8

56.9

110.3

44.0

J

127.9

137.5

80.8

62.01

112.3

49.4

Determination of Crack Growth and crack initiation

Sample

No. of cycle for initiation (un notched)

No. of cycle for crack growth (8mm) (Notch-2mm)

Regular

65114

372768

H

52130

348414

J

80663

428110

Determination of heat build-up

SAMPLE

HEAT BUILD UP

Regular

15

H

22

J

23

Determination of Resilience

Sample

Resilience

Regular

38.59

H

32.3

J

34.2


2 Graphs

REGULAR RHEOGRAPH

The values obtained from graph:-

Samples

ML

TS1

TS2

MH

TC15

TC25

TC50

TC90

Regular

7.96

13.17

16.32

21.47

16.93

18.90

22.28

30.68

H

7.61

13.38

16.18

24.69

17.07

18.80

22.00

31.00

J

7.55

13.23

16.18

24.28

16.93

18.73

21.98

31.33


Comparison of Results.

Rheological properties

Mooney Viscosity

From the fig.1, by comparing with regular compound (R), the cure time of compound (H) decreased by 2.8 units. Compound (J) decreased by 3.9 units.

Mooney scorch

From the fig.2, by comparing with regular compound (R), the moony scorch of compound (H) increased by 0.38 minutes. Compound (J) decreased by 0.14 minutes.

Minimum Torque(ML)

From the fig.3, by comparing with regular compound (R), the minimum Torque (ML)of compound (H) decreased by 0.35 minutes. Compound (J) decreased by 0.41 minutes.

Maximum torque(MH)

From the fig.4, by comparing with regular compound (R), the maximum torque(MH) of compound (H) increased by 1.22 minutes. Compound (J) increased by 0.81 minutes.

Induction time(Ts2)

From the fig.6, by comparing with regular compound (R), the induction time(Ts2) of compound (H) decreased by 0.14 minutes. Compound (J) decreased by 0.14 minutes.

Optimum cure(Tc90)

From the fig.10, by comparing with regular compound (R), the optimum cure(Tc90) of compound (H) increased by 0.52 minutes. Compound (J) increased by 0.65 minutes.

Physical properties

For unaged sample

Modulus at 100% elongation

From the fig.11, by comparing with regular compound (R), the modulus at 100% elongation of compound (H) increased by 10.9%, Compound (J) increased by 6.8%.

Modulus at 300% elongation

From the fig.12, by comparing with regular compound (R), modulus at 300% elongation of compound (H) increased by 4.83%, Compound (J) decreased by 1.1%.

Tensile strength

From the fig.13, by comparing with regular compound (R), the Tensile strength of compound (H) increased by 1.5%, Compound (J) increased by 2.1%.

Elongation at break(EB).

From the fig.14, by comparing with regular compound (R), the Elongation at break (EB) of compound (H) is same %, Compound (J) increased by 1.3%.

Hardness

From the fig.15, by comparing with regular compound (R), the Hardness of compound (H) is same%, Compound (J) decreased by 4%.

Tear strength

From the fig.16, by comparing with regular compound (R), the Tear strength of compound (H) increased by 2.53%, Compound (J) increased by 2.1 %.

For aged sample

1. Modulus at 100% elongation

From the fig.11, by comparing with regular compound (R), the modulus at 100% elongation of compound (H) increased by 24.1%, Compound (J) decreased by 2.2%.

2. Modulus at 300% elongation

From the fig.12, by comparing with regular compound (R), the modulus at 300% elongation of compound (H) increased by 9.6%, Compound (J) increased by 1.2%.

3. Tensile strength.

From the fig.13, by comparing with regular compound (R), the Tensile strength of compound (H) decreased by 0.25%Compound (J) increased by 0.33%.


4. Elongation at break(EB).

From the fig.14, by comparing with regular compound (R), the Elongation at break(EB) of compound (H) decreased by 2 %Compound (J) decreased by 0.8%.

5. Hardness.

From the fig.15, by comparing with regular compound (R), the Hardness of compound (H) increased by 5 %Compound (J) increased by 3.5%.

6. Tear strength

From the fig.16, by comparing with regular compound (R), the Tear strength of compound (H) increased by 8.4%Compound (J) decreased by 2.2%.


Flex Resistance

Crack Initiation

From the fig.23, by comparing with regular compound (R), the Hardness of compound (H) decreased by 24.9% Compound (J) increased by 18.7%.

Crack Growth

From the fig.24, by comparing with regular compound (R), the Hardness of compound (H) decreased by 6.9%Compound (J) increased by 12.9%.

Heat Build up

From the fig.25, by comparing with regular compound (R), the Hardness of compound (H) increased by 7%Compound (J) increased by 8%.

Resilience

From the fig.26, by comparing with regular compound (R), the Hardness of compound (H) decreased by 18.9%Compound (J) decreased by 12.6%.

CONCLUSION

From the tests and observations, the samples H (NR;- 40, PBD:-50, SBR:-10, TBBS;-0.9) and J (NR;- 40, PBD:-50, SBR:-10, TBBS;-0.935) are more similar in cure and physical properties with regular side wall compound (NR;- 50, PBD:-50, TBBS;-0.85), and they have good tensile, tear and resilience properties. One of the important properties required for the sidewall compound is crack initiation and growth resistance. These properties are excellent for compound J when compared with compound H. So J is more preferable.

Recommendation

If compound ‘J’ is used as a truck sidewall compound, the manufacturing cost can be minimized without affecting the properties.


References


BOOKS

v RUBBER TECHNOLOGY AND MANUFACTURE-C.W. BLOW, second edition.

v TIRE TECHNOLOGY –F.J.KOVAC,1978.

v RUBBER ENGINEERING-Indian Rubber Institute,1998

v Hand Book of RUBBER TECHNOLOGY – Hoffman.

v Hand Book of Testing & Identification of Rubber – Steven Blow,1998.

WEBSITES

v www.indiarubberdirectory.com

v www.wikipedia.org

v www.etyres.co.uk


1 comment:

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