31 August 2010

Reclaimed Rubber

Manufacture of Reclaimed Rubber
The major reclaiming processes are the following.


Sub Topics
  • Heater or Pan Process
  • Wet Digester Process
  • Reclaimator Process        
     

    Heater or Pan Process

    Any fiber present is separated mechanically and the ground fabric free scrap is blended with reclaiming agents. The same is fed into large horizontal single-shell heater. After devulcanisation, the heater cakes are removed, broken up, milled and refined. The temperature range employed during reclamation is 170-2100C, for a period of 4-12 hours.






    Wet Digester Process

    Coarsely ground scrap mixed with reclaiming and defibering agents and a large excess of water is heated in a digester. After discharge, the devulcanized rubber is washed, dewatered, dried and blended with processing agents such as oil, refined, strained and packed.



    Reclaimator Process

     
    Whole tires are cracked to a convenient size, and the fibre is removed mechanically. The relatively fiber-free scrap is ground to approximately 30 mesh before being mixed with chemical agents for reclaiming continuously in a reclaimator. The temperature range is 204-260o C and the devulcanization time is 1-4 minutes. Reclaimed material is then mixed and blended with small proportions of reinforcing and processing agents.










    Processing Advantages of
    Reclaimed Rubber
     
    1. Low power consumption during break down and mixing. During manufacture, reclaimed rubber has already been thoroughly plasticised so that it breaks down and mixes more quickly than the virgin rubber.
    2. Low mixing, calendaring and extrusion temperature.
    3. Non-critical calendaring temperature range. Reclaim is less nervy than virgin rubber and hence builds up less internal heat in the calender bank, imparting more process safety.
    4. Fast, Uniform Calendering and Extrusion.
    5. Improves penetration of fabric.
    6. Improves tackiness and hold the same over a broader range of temperature.
    7. Reduce and retard blooming of sulfur from both cured and uncured stock.
    8. Low swelling and shrinkage on extrusion and calendaring.
    9. Low Thermo plasticity.
      Due to the cross linked structure of reclaimed rubber, its compounds are less thermoplastic than virgin rubber compounds and therefore when extruded and cured in open stream, they tend to hold their shape better.
    10. Low volume cost for the product
     



     










    Major Uses of Reclaimed Rubber
     
     
    1. Passenger Tire Carcass
    2. In extruded and calendared products
    3. In products such tiles for laying pedestrian concrete areas, Animal mats used in stables, Insulation tiles used in metro railways for reducing the noise level etc.
    4. Inner Tubes: - A moderate proportion of butyl reclaim is used in butyl inner tubes.
    5. Tubeless Tire Liners: - Butyl reclaimed rubber is used widely because of its good air retention property.




27 August 2010

LIGHT EMITTING POLYMER




LIGHT EMITTING POLYMER



(ലൈറ്റ് എമിറ്റിംഗ് പോല്യ്മര്‍)



ABSTRACT

The seminar is about polymers that can emit light when a voltage is applied to it. The structure comprises of a thin film of semiconducting polymer sandwiched between two electrodes (cathode and anode).When electrons and holes are injected from the electrodes, the recombination of these charge carriers takes place, which leads to emission of light .The band gap, ie. The energy difference between valence band and conduction band determines the wavelength (colour) of the emitted light.


They are usually made by ink jet printing process. In this method red green and blue polymer solutions are jetted into well defined areas on the substrate. This is because, PLEDs are soluble in common organic solvents like toluene and xylene .The film thickness uniformity is obtained by multi-passing (slow) is by heads with drive per nozzle technology .The pixels are controlled by using active or passive matrix.


The advantages include low cost, small size, no viewing angle restrictions, low power requirement, biodegradability etc. They are poised to replace LCDs used in laptops and CRTs used in desktop computers today.


Their future applications include flexible displays which can be folded, wearable displays with interactive features, camouflage etc.







INDEX





1. INTRODUCTION 4

2. SUBJECT DETAILING 6


2.1 CONSTRUCTION OF LEP 7


2.1.1 INK JET PRINTING 8


2.1.2 ACTIVE AND PASSIVE MATRIX 9


2.2 BASIC PRINCIPLE AND TECHNOLOGY 11


2.3 LIGHT EMISSION 12


2.4 COMPARISON TABLE 15


3. ADVANTAGES AND DISADVANTAGES 14


3.1 ADVANTAGES 19


3.2 DIS ADVANTAGES 19


4. APPLICATIONS AND FUTURE DEVELOPMENTS
20


4.1 APPLICATIONS 21


4.2 FUTURE DEVELOPMENTS 23























LIGHT EMITTING POLYMER






INTRODUCTION




Introduction-Imagine these scenarios



- After watching the breakfast news on TV, you roll up the set like a large handkerchief, and stuff it into your briefcase. On the bus or train journey to your office, you can pull it out and catch up with the latest stock market quotes on CNBC.



- Somewhere in the Kargil sector, a platoon commander of the Indian Army readies for the regular satellite updates that will give him the latest terrain pictures of the border in his sector. He unrolls a plastic-like map and hooks it to the unit's satellite telephone. In seconds, the map is refreshed with the latest high resolution camera images grabbed by an Indian satellite which passed over the region just minutes ago.



Don't imagine these scenarios at least not for too long.The current 40 billion-dollar display market, dominated by LCDs (standard in laptops) and cathode ray tubes (CRTs, standard in televisions), is seeing the introduction of full-color LEP-driven displays that are more efficient, brighter, and easier to manufacture. It is possible that organic light-emitting materials will replace older display technologies much like compact discs have relegated cassette tapes to storage bins.



The origins of polymer OLED technology go back to the discovery of conducting polymers in 1977,which earned the co-discoverers- Alan J. Heeger , Alan G. MacDiarmid and Hideki Shirakawa - the 2000 Nobel prize in chemistry. Following this discovery , researchers at Cambridge University UK discovered in 1990 that conducting polymers also exhibit electroluminescence and the light emitting polymer(LEP) was born!.




SUBJECT DETAILING




2. LIGHT EMITTING POLYMER



It is a polymer that emits light when a voltage is applied to it. The structure comprises a thin-film of semiconducting polymer sandwiched between two electrodes (anode and cathode) as shown in fig.1. When electrons and holes are injected from the electrodes, the recombination of these charge carriers takes place, which leads to emission of light that escapes through glass substrate. The bandgap, i.e. energy difference between valence band and conduction band of the semiconducting polymer determines the wavelength (colour) of the emitted light.











2.1 CONSTRUCTION




Light-emitting devices consist of active/emitting layers sandwiched between a cathode and an anode. Indium-tin oxides typically used for the anode and aluminum or calcium for the cathode. Fig.2.1(a) shows the structure of a simple single layer device with electrodes and an active layer.











Single-layer devices typically work only under a forward DC bias. Fig.2.1(b) shows a symmetrically configured alternating current light-emitting (SCALE) device that works under AC as well as forward and reverse DC bias.


In order to manufacture the polymer, a spin-coating machine is used that has a plate spinning at the speed of a few thousand rotations per minute. The robot pours the plastic over the rotating plate, which, in turn, evenly spreads the polymer on the plate. This results in an extremely fine layer of the polymer having a thickness of 100 nanometers. Once the polymer is evenly spread, it is baked in an oven to evaporate any remnant liquid. The same technology is used to coat the CDs.





2.1.1 INK JET PRINTING





Although inkjet printing is well established in printing graphic images, only now are applications emerging in printing electronics materials. Approximately a dozen companies have demonstrated the use of inkjet printing for PLED displays and this technique is now at the forefront of developments in digital electronic materials deposition. However, turning inkjet printing into a manufacturing process for PLED displays has required significant developments of the inkjet print head, the inks and the substrates (see Fig.2.1.1).Creating a full colour, inkjet printed display requires the precise metering of volumes in the order of pico liters. Red, green and blue polymer solutions are jetted into well defined areas with an angle of flight deviation of less than 5º. To ensure the displays have uniform emission, the film thickness has to be very uniform.











Fig. 2.1.1 Schematic of the ink jet printing for PLED materials





For some materials and display applications the film thickness uniformity may have to be better than ±2 per cent. A conventional inkjet head may have volume variations of up to ±20 per cent from the hundred or so nozzles that comprise the head and, in the worst case, a nozzle may be blocked. For graphic art this variation can be averaged out by multi-passing with the quality to the print dependent on the number of passes. Although multi-passing could be used for PLEDs the process would be unacceptably slow. Recently, Spectra, the world's largest supplier of industrial inkjet heads, has started to manufacture heads where the drive conditions for each nozzle can be adjusted individually - so called drive-per-nozzle (DPN). Litrex in the USA, a subsidiary of CDT, has developed software to allow DPN to be used in its printers. Volume variations across the head of ±2 per cent can be achieved using DPN. In addition to very good volume control, the head has been designed to give drops of ink with a very small angle-of-flight variation. A 200 dots per inch (dpi) display has colour pixels only 40 microns wide; the latest print heads have a deviation of less than ±5 microns when placed 0.5 mm from the substrate. In addition to the precision of the print head, the formulation of the ink is key to making effective and attractive display devices. The formulation of a dry polymer material into an ink suitable for PLED displays requires that the inkjets reliably at high frequency and that on reaching the surface of the substrate, forms a wet film in the correct location and dries to a uniformly flat film. The film then has to perform as a useful electro-optical material. Recent progress in ink formulation and printer technology has allowed 400 mm panels to be colour printed in under a minute.





2.1.2 ACTIVE AND PASSIVE MATRIX





Many displays consist of a matrix of pixels, formed at the intersection of rows and columns deposited on a substrate. Each pixel is a light emitting diode such as a PLED, capable of emitting light by being turned on or off, or any state in between. Coloured displays are formed by positioning matrices of red, green and blue pixels very close together. To control the pixels, and so form the image required, either 'passive' or 'active' matrix driver methods are used.


Pixel displays can either by active or passive matrix. Fig. 2.1.2 shows the differences between the two matrix types, active displays have transistors so that when a particular pixel is turned on it remains on until it is turned off.


The matrix pixels are accessed sequentially. As a result passive displays are prone to flickering since each pixel only emits light for such a small length of time. Active displays are preferred, however it is technically challenging to incorporate so many transistors into such small a compact area.









Fig 2.1.2 Active and passive matrices





In passive matrix systems, each row and each column of the display has its own driver, and to create an image, the matrix is rapidly scanned to enable every pixel to be switched on or off as required. As the current required to brighten a pixel increases (for higher brightness displays), and as the display gets larger, this process becomes more difficult since higher currents have to flow down the control lines. Also, the controlling current has to be present whenever the pixel is required to light up. As a result, passive matrix displays tend to be used mainly where cheap, simple displays are required.





Active matrix displays solve the problem of efficiently addressing each pixel by incorporating a transistor (TFT) in series with each pixel which provides control over the current and hence the brightness of individual pixels. Lower currents can now flow down the control wires since these have only to program the TFT driver, and the wires can be finer as a result. Also, the transistor is able to hold the current setting, keeping the pixel at the required brightness, until it receives another control signal. Future demands on displays will in part require larger area displays so the active matrix market segment will grow faster.





PLED devices are especially suitable for incorporating into active matrix displays, as they are processable in solution and can be manufactured using ink jet printing over larger areas.





2.2 BASIC PRINCIPLE AND TECHNOLOGY




Polymer properties are dominated by the covalent nature of carbon bonds making up the organic molecule's backbone. The immobility of electrons that form the covalent bonds explain why plastics were classified almost exclusively insulators until the 1970's.



A single carbon-carbon bond is composed of two electrons being shared in overlapping wave functions. For each carbon, the four electrons in the valence bond form tetrahedral oriented hybridized sp3 orbitals from the s & p orbitals described quantum mechanically as geometrical wave functions. The properties of the spherical s orbital and bimodal p orbitals combine into four equal , unsymmetrical , tetrahedral oriented hybridized sp3 orbitals. The bond formed by the overlap of these hybridized orbitals from two carbon atoms is referred to as a 'sigma' bond.




A conjugated 'pi' bond refers to a carbon chain or ring whose bonds alternate between single and double (or triple) bonds. The bonding system tend to form stronger bonds than might be first indicated by a structure with single bonds. The single bond formed between two double bonds inherits the characteristics of the double bonds since the single bond is formed by two sp2 hybrid orbitals. The p orbitals of the single bonded carbons form an effective 'pi' bond ultimately leading to the significant consequence of 'pi' electron de-localization.




Unlike the 'sigma' bond electrons, which are trapped between the carbons, the 'pi' bond electrons have relative mobility. All that is required to provide an effective conducting band is the oxidation or reduction of carbons in the backbone. Then the electrons have mobility, as do the holes generated by the absence of electrons through oxidation with a dopant like iodine.





2.2.1 LIGHT EMISSION




The production of photons from the energy gap of a material is very similar for organic and ceramic semiconductors. Hence a brief description of the process of electroluminescence is in order.


Electroluminescence is the process in which electromagnetic(EM) radiation is emitted from a material by passing an electrical current through it. The frequency of the EM radiation is directly related to the energy of separation between electrons in the conduction band and electrons in the valence band. These bands form the periodic arrangement of atoms in the crystal structure of the semiconductor. In a ceramic semiconductor like GaAs or ZnS, the energy is released when an electron from the conduction band falls into a hole in the valence band. The electronic device that accomplishes this electron-hole interaction is that of a diode, which consists of an n-type material (electron rich) interfaced with p-type material (hole rich). When the diode is forward biased (electrons across interface from n to p by an applied voltage) the electrons cross a neutralized zone at the interface to fill holes and thus emit energy.


The situation is very similar for organic semiconductors with two notable exceptions. The first exception stems from the nature of the conduction band in an organic system while the second exception is the recognition of how conduction occurs between two organic molecules.


With non-organic semiconductors there is a band gap associated with Brillouin zones that discrete electron energies based on the periodic order of the crystalline lattice. The free electron's mobility from lattice site to lattice site is clearly sensitive to the long-term order of the material. This is not so for the organic semiconductor. The energy gap of the polymer is more a function of the individual backbone, and the mobility of electrons and holes are limited to the linear or branched directions of the molecule they statistically inhabit. The efficiency of electron/hole transport between polymer molecules is also unique to


polymers. Electron and hole mobility occurs as a 'hopping' mechanism which is significant to the practical development of organic emitting devices.


PPV has a fully conjugated backbone (figure 2.2.1), as a consequence the HOMO (exp link remember 6th form!) of the macromolecule stretches across the entire chain, this kind of situation is ideal for the transport of charge; in simple terms, electrons can simply "hop" from one π orbital to the next since they are all linked.



untitled.JPG



Figure 2.2.1 A demonstration of the full conjugation of π


electrons in PPV.The delocalized π electron clouds are coloured yellow.


PPV is a semiconductor. Semiconductors are so called because they have conductivity that is midway between that of a conductor and an insulator. While conductors such as copper conduct electricity with little to no energy (in this case potential difference or voltage) required to "kick-start" a current, insulators such as glass require huge amounts of energy to conduct a current. Semi-conductors require modest amounts of energy in order to carry a current, and are used in technologies such as transistors, microchips and LEDs.


Band theory is used to explain the semi-conductance of PPV, see figure 5. In a diatomic molecule, a molecular orbital (MO) diagram can be drawn showing a single HOMO and LUMO, corresponding to a low energy π orbital and a high energy π* orbital. This is simple enough, however, every time an atom is added to the molecule a further MO is added to the MO diagram. Thus for a PPV chain which consists of ~1300 atoms involved in conjugation, the LUMOs and HOMOs will be so numerous as to be effectively continuous, this results in two bands, a valence band (HOMOs, π orbitals) and a conduction band (LUMOs, π* orbitals). They are separated by a band gap which is typically 0-10eV (check) and depends on the type of material. PPV has a band gap of 2.2eV (exp eV). The valence band is filled with


all the π electrons in the chain, and thus is entirely filled, while the conduction band, being made up of empty π* orbitals (the LUMOs) is entirely empty).


In order for PPV to carry a charge, the charge carriers (e.g. electrons) must be given enough energy to "jump" this barrier - to proceed from the valence band to the conduction band where they are free to ride the PPV chain's empty LUMOs.(Fig. 2.2.2)




led.JPG






Figure 2.2.2 A series of orbital diagrams.


• A diatomic molecule has a bonding and an anti-bonding orbital, two atomic orbitals gives two molecular orbitals. The electrons arrange themselves following, Auf Bau and the Pauli Principle.


• A single atom has one atomic obital


• A triatomic molecule has three molecular orbitals, as before one bonding, one anti-bonding, and in addition one non-bonding orbital.


• Four atomic orbitals give four molecular orbitals.


• Many atoms results in so many closely spaced orbitals that they are effectively continuous and non-quantum. The orbital sets are called bands. In this case the bands are separated by a band gap, and thus the substance is either an insulator or a semi-conductor.


It is already apparent that conduction in polymers is not similar to that of metals and inorganic conductors , however there is more to this story! First we need to imagine a conventional diode system, i.e. PPV sandwiched between an electron injector (or cathode), and an anode. The electron injector needs to inject electrons of sufficient energy to exceed the band gap, the anode operates by removing electrons from the polymer and consequently leaving regions of positive charge called holes. The anode is consequently referred to as the hole injector.


In this model, holes and electrons are referred to as charge carriers, both are free to traverse the PPV chains and as a result will come into contact. It is logical for an electron to fill a hole when the opportunity is presented and they are said to capture one another. The capture of oppositely charged carriers is referred to as recombination. When captured, an electron and a hole form neutral-bound excited states (termed excitons) that quickly decay and produce a photon up to 25% of the time, 75% of the time, decay produces only heat, this is due to the the possible multiplicities of the exciton. The frequency of the photon is tied to the band-gap of the polymer; PPV has a band-gap of 2.2eV, which corresponds to yellow-green light.


Not all conducting polymers fluoresce, polyacetylene, one of the first conducting-polymers to be discovered was found to fluoresce at extremely low levels of intensity. Excitons are still captured and still decay, however they mostly decay to release heat. This is what you may have expected since electrical resistance in most conductors causes the conductor to become hot.


Capture is essential for a current to be sustained. Without capture the charge densities of holes and electrons would build up, quickly preventing any injection of charge carriers. In effect no current would flow.




CHAPTER 3


ADVANTAGES AND DISADVANTAGES







3.1 ADVANTAGES


• Require only 3.3 volts and have lifetime of more than 30,000 hours.


• Low power consumption.


• Self luminous.


• No viewing angle dependence.


• Display fast moving images with optimum clarity.


• Cost much less to manufacture and to run than CRTs because the active material is plastic.


• Can be scaled to any dimension.


• Fast switching speeds that are typical of LEDs.


• No environmental draw backs.


• No power in take when switched off.


• All colours of the visible spectrum are possible by appropriate choose of polymers.


• Simple to use technology than conventional solid state LEDs and lasers.


• Very slim flat panel.





3.2 DISADVANTAGES


• Vulnerable to shorts due to contamination of substrate surface by dust.


• Voltage drops.


• Mechanically fragile.


• Potential not yet realized.



CHAPTER 4


APPLICATIONS AND FUTURE


DEVELOPMENTS


4. APPLICATIONS




Polymer light-emitting diodes (PLED) can easily be processed into large-area thin films using simple and inexpensive technology. They also promise to challenge LCD's as the premiere display technology for wireless phones, pagers, and PDA's with brighter, thinner, lighter, and faster features than the current display.




4.1 PHOTOVOLTAICS




CDT's PLED technology can be used in reverse, to convert light into electricity. Devices which convert light into electricity are called photovoltaic (PV) devices, and are at the heart of solar cells and light detectors. CDT has an active program to develop efficient solar cells and light detectors using its polymer semiconductor know-how and experience, and has filed several patents in the area.





Digital clocks powered by CDT's polymer solar cells.


4.2 POLY LED TV


Philips will demonstrate its first 13-inch PolyLED TV prototype based on polymer OLED (organic light-emitting diode) technology Taking as its reference application the wide-screen 30-inch diagonal display with WXGA (1365x768) resolution, Philips has produced a prototype 13-inch carve-out of this display (resolution 576x324) to demonstrate the feasibility of manufacturing large-screen polymer OLED displays using high-accuracy multi-nozzle, multi-head inkjet printers. The excellent and sparkling image quality of Philips' PolyLED TV prototype illustrates the great potential of this new display technology for TV applications. According to current predictions, a polymer OLED-based TV could be a reality in the next five years.







4.3 BABY MOBILE



This award winning baby mobile uses light weight organic light emitting diodes to realize images and sounds in response to gestures and speech of the infant.






4.4 MP3 PLAYER DISPLAY



Another product on the market taking advantage of a thin form-factor, light-emitting polymer display is the new, compact, MP3 audio player, marketed by GoDot Technology. The unit employs a polymeric light-emitting diode (pLED) display supplied by Delta Optoelectronics, Taiwan, which is made with green Lumation light-emitting polymers furnished by Dow Chemical Co., Midland, Mich.



5. FUTURE DEVELOPMENTS




Here's just a few ideas which build on the versatility of light emitting materials.







High efficiency displays running on low power and economical to manufacture will find many uses in the consumer electronics field. Bright, clear screens filled with information and entertainment data of all sorts may make our lives easier, happier and safer


.







Demands for information on the move could drive the development of 'wearable' displays, with interactive features.









Eywith changing information cole woul give many brand ownerve edge








The ability of PLEDs to be fabricated on flexible substrates opens up fascinating possibilities for formable or even fully flexible displays e catching packaging intent at the point of sa d s a valuable competition


FEW MORE DEVELOPMENTS


• Because the plastics can be made in the form of thin films or sheets, they offer a huge range of applications. These include television or computer screens that can be rolled up and tossed in a briefcase, and cheap videophones.


• Clothes made of the polymer and powered by a small battery pack could provide their own cinema show.


• Camouflage, generating an image of its surroundings picked up by a camera would allow its wearer to blend perfectly into the background


• A fully integrated analytical chip that contains an integrated light source and detector could provide powerful point-of-care technology. This would greatly extend the tools available to a doctor and would allow on-the-spot quantitative analysis, eliminating the need for patients to make repeat visits. This would bring forward the start of treatment, lower treatment costs and free up clinician time.



The future is bright for products incorporating PLED displays. Ultra-light, ultra-thin displays, with low power consumption and excellent readability allow product designers a much freer rein. The environmentally conscious will warm to the absence of toxic substances and lower overall material requirements of PLEDs, and it would not be an exaggeration to say that all current display applications could benefit from the introduction of PLED technology. CDT sees PLED technology as being first applied to mobile communications, small and low information content instrumentation, and appliance displays. With the emergence of 3G telecommunications, high quality displays will be critical for handheld devices. PLEDs are ideal for the small display market as they offer vibrant, full-colour displays in a compact, lightweight and flexible form. Within the next few years, PLEDs are expected to make significant inroads into markets currently dominated by the cathode ray tube and LCD display technologies, such as televisions and computer monitors. PLEDs are anticipated as the technology of choice for new products including virtual reality headsets; a wide range of thin, technologies, such as televisions and computer monitors. PLEDs are anticipated as the technology of choice for new products including virtual reality headsets; a wide range of thin, lightweight, full colour portable computing; communications and information management products; and conformable or flexible displays.





6. CONCLUSION


Organic materials are poised as never before to trans form the world of display technology. Major electronic firms such as Philips and pioneer and smaller companies such as Cambridge Display Technology are betting that the future holds tremendous opportunity for low cost and surprisingly high performance offered by organic electronic and opto electronic devices. Using organic light emitting diodes, organic full colour displays may eventually replace LCDs in laptop and even desktop computers. Such displays can be deposited on flexible plastic coils, eliminating fragile and heavy glass substrate used in LCDs and can emit light without the directionality inherent in LCD viewing with efficiencies higher than that can be obtained with incandescent light bulbs.




Organic electronics are already entering commercial world. Multicolor automobile stereo displays are now available from Pioneer Corp., of Tokyo And Royal Philips Electronics, Amserdam is gearing up to produce PLED backlights to be used in LCDs and organic ICs.




The first products using organic displays are already in the market. And while it is always difficult to predict when and what future products will be introduced, many manufactures are working to introduce cell phoned and personal digital assistants with organic displays within the next few years. The ultimate goal of using high efficiency, phosphorescent




flexible organic displays in laptop computers and even for home video applications may be no more than a few years in to the future. The portable and light weight organic displays will soon cover our walls replacing the bulky and power hungry cathode ray tubes.




REFERENCE



· www.cdtltd.co.uk


· www.research.philips.com


· www.covion.com


· www.lep-light.com


· IEEE JOURNAL




26 August 2010

IMPROVEMENT OF BREAKER OFFCENTERING

Zo


PROJECT REPORT

ON



IMPROVEMENT OF BREAKER

OFFCENTERING


RENJITH. P.R



CONTENTS

Introduction

Scope and objectives

Study on off centering

Methodology

Graphs and tables

Results

Conclusions

References




INTRODUCTION

Pneumatic tires are the most versatile and probably the first engineering product made out of polymers and has made it possible the evolution of sophisticated, personalized land transportation system.


It was John Boyd Dunlop who in 1888 developed successfully the Pneumatic tire and before that railways offered the only means of transportation for long distances and horse furnished most of the day to day transportation.

It was the invention of pneumatic tire that widened the horizons of average people and altered their way of life first by popularizing bicycle and then auto mobile, ultimately society itself was changed.

A Pneumatic tire is a toroidal shaped flexible high performance composite membrane capable of containing air or fluid under pressure when mounted on a rim. Chemically the composite membrane essentially consists of two types of polymers that is rubbers and fiber foaming plastics.

In other words it is a thick rubber rainy often filled with air to carry the load which is fitted around the edge of the wheel of the vehicle, allowing the vehicle to stick to road surface and improving smoothness of journey by acting as a shock absorber.




FUNCTIONS OF A PNUEMATIC TYRE



A pneumatic tire performs the following principal functions.


a) It supports the weight of the vehicle

b) It transmits the forces on the vehicle to ground that is, it helps to convert the engine torque to movement of the vehicle.

c) It gives more comfortable ride to passengers or cargo in the vehicle by

i) Acting as an additional spring in suspension system.

ii) Elastic deformations over undulations on road.

d) It permits cornering on the road at relatively high speeds by its capacity to generate higher cornering forces than it would have been possible with a solid tire.



Beads



The bead coils are a combination of multi-strand copper-coated high-tensile steel wires. They have the function of providing rigid, practically inextensible units, which retain the inflated tire on the rim under all conditions of loading. The appropriate numbers of wires, formed into a that layer and uniformly separated, are coated with rubber compound by means of a T-head extruder. The layer of wires is coiled to form a ring, and the free wire ends are taped or stapled. The wire treatment and use of fast-curing compound ensure good bonding and a regular bead shape in the finished product. For some purposes, the bead coil is covered with a light cross-woven rubberized textile to contain the wires and preclude any possibility of looseness in service.


Bead Fillers


In those instances where further reinforcement of the tire bead area is required, the already wrapped and apexed bead may be enclosed by a strip of rubberized textile or, in some applications, by steel cords. Emphasis is on the avoidance of localized circumferential stress lines which could promote looseness or cord break-up under constant Ilex conditions. High-grade flexible heat-resistant compounds are essential for this region of the tire.



Carcass Plies



It is the carcass plies that give the tire its strength. These consist of cords of rayon, nylon, or polyester, woven as the warp of a fabric with only very light yarns, widely spaced, as the weft. These weft strands serve to maintain the uniformity of cord spacing during handling but play no part in the performance of the product. The fabric is treated with adhesive, rubberized to a thickness of approximately 1-0 mm. and interleaved with a low moisture regain textile lining. Steel is produced in weft less form from a creel feeding directly through a rubber calendar. The large rolls of rubbered textile approximately 1-5m wide and 300m long are cut into strips, termed plies, on a horizontal Banner machine. This ply cutting plant has facilities for mechanically unwinding large rolls of fabric and simultaneously rewinding the interleaving lining. The fabric sheet is fed forward, through a festoon unit to allow for continuous operation, and then guided along a horizontal multi-belt conveyor to a cross-beam rotary cutting knife This knife is complete with its own drive motor, and the entire unit traverses across the support beam when cutting the material to pre-determined width and bi angle; the latter is variable between 45 and 90, and the operation is controlled by photoelectric cells.


Cut plies are placed manually on adjacent batching tables, where they a joined, end to end, into a continuous length and batched into roll form interleaved with a textile lining to prevent self-adhesion. Suitable devices are provided at all stages to prevent distortion of the material.


Tread Bracing Components (Breaker or Belts) for Radial or Belted Bias Tires


Tread bracing components raise the modulus of the tread area, thereby maintaining the inflated tire tread profile and reducing tread pattern movement as it contacts the road.

The method of strip cutting rubbered textile belt cords is identical to this used for cutting plies but, in this case, the travelling beam on the bias cutting machine is adjustable for angles of 15° - 25°. The method c converting the single-layer, low-angle cut strips into the form of the fin; belt may vary. A typical construction for textile belted radial-ply tire employs four layers, made from folded strips, adjacent layers being c opposite bias angle. The method of assembly is shown in Fig. 10.4. In practice the two strips are slightly offset to achieve a graduated step-down in thickness at the belt edges, thereby reducing stress concentration and minimizing the development of looseness in service. In the case of steel belted radial-ply tire appropriate cutting equipment is used to cut the calendared material. Two cut layers are used at appropriate bias angle this form the belt the whole may be encompassed by a calendared shoe containing nylon cords at 0° angle.


Insulating Components (Under tread, Breaker Cushion Insulations)



These insulating components are calendared strips of rubber compound usually of 1mm gauge or less. They are located in positions within the structure where additional insulation is required between components to prevent chafing. The compounds are similar to those used for coating the carcass plies.


Tread


The tread is the wearing surface of the tyre. It is applied in the raw state as an extruded slab of rubber compound. In cross-section it is substantially rect­angular across the centre portion, tapering down to very fine edges. The thickness must be calculated to accommodate the pattern fragmentation in the tyre mould and to allow an adequate residual thickness beneath the pattern grooves. The tread width is such that the tapered edges extend to a position slightly above the maximum flex zone in the upper sidewall region.


The extruding operation is continuous, and the extrudate is either batched as a continuous length into a hand dispenser, for subsequent cutting to length at the tyre building machine, or pre-cut into individual lengths and stored on flat metal trays in multi-leaf stillages.


Sidewall


The sidewall is an extruded rubber compound layer which serves to protect the carcass structure from weathering and chafing damage. Together with the tread, which it overlaps in the buttress region, it forms the outermost layer of the tire.


As with the tread, the extruding operation is continuous, and sidewalls are normally batched into spools interleaved with a textile or polyethylene lining material.


For conventional diagonal ply and belted bias tires, built on relatively flat drums, frequently a common formulation permits extrusion of tread and sidewalls as one piece. Two separate compounds are used either to achieve performance or for reasons of economy.


Modern dual extruders, feeding through a common Y-box head, produce a combined tread-sidewall unit; by joining the two stocks under high pressure and at high temperature, interface failures are eliminated.

Chafer

The chafer is a narrow circumferential strip of material which encloses the completed bead area. Its upper edge is located slightly above the rim flange height and extends downwards and around the bead base. This arrangement provides some protection from rim chafing and, in the case of tubeless tires, serves to prevent air leakage cither into the tire or through the tire in the bead area. To meet these conditions, the material used is either a rubber-coated wick-proof cross-woven textile cut at 45O bias or a strip of calendared compound. In the latter case, the strip, of approximately 1mm gauge, is generally fully cured, buffed, and solutioned, prior to assembly into the raw tire. In this way, stock flow during vulcanization is avoided and the retention of an adequate rubber covering over the casing ply edges is assured.

Processing of cured rubber strips is a continuous operation of multi-strip calendering and vulcanizing by drum cure. After surface buffing and solutioning, individually on an ancillary unit, the strips are spooled in continuous lengths suitably interleaved with polyethylene.

Inner Lining

For tubed tires, the inner lining is a thin layer of compound usually calendared direct on to the underside of the first ply after the latter has been joined and batched in continuous lengths. The component serves to insulate fully the tyre cords from the inner tube and thereby prevent tube chafing damage. It also protects the cords from possible degradation due to atmospheric moisture absorption.

In tubeless tires, the inner lining is the air-retaining member and is usually calendared as a two-layer laminate having stepped edges. The overall gauge may be as high as 2-5 mm, and the width must ensure that the edges are overlapped by the inner edges of the chafer. This provides a low per­meability layer from bead tobead.

Clinch Strip

The clinch strip may be considered as an extension to the lower edge of the sidewall, introduced as a further anti-abrasion measure on radial ply tires, which are more subject to rim chafing than the cross ply tyre. It is a narrow extruded strip, about 25 mm wide and tapered at both edges, which is normally hot-assembled to the sidewalls by operating extruders in train.


It should be appreciated that the above elemental breakdown only deals with a comparatively simple passenger car tire construction. Truck tires and allied ranges are far more complex, involving many additional components, inserts, and compounds. Also, it will be obvious that preparation and handling techniques have to be adjusted to deal with the sheer dimensional size and weight of components used in these products. Steel ply radial giant earthmover, and aircraft tires are particular examples.



BASIC TIRE 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 tires.



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.




TYREMANUFACTURING





SCOPE AND OBJECTIVES



Tire manufacturing includes many stages. All these stages are prone to some kind of defects. Even the smallest defect in any of these stages can have significant effect on performance of a tire.



This project is undertaken to study off centering of breakers that is to determine possible reasons of its occurrence and to suggest methods to improve it. Off centering of breakers can be one of the main reasons for inducing the early failures during service period there by reducing the life of tires.



Off centering of breaker can occur because of the following reasons


1. Incoming material related problems


2. Machine related problems


3. Worker related problems




STUDY OF OFFCENTREING OF BREAKERS



BREAKERS:


These are short plies with low EPI (ends per inch) cut at an angle and are positioned centrally between tire casing and tread to strengthen carcass against impact. They also provide cushioning effect and increase the modulus of tread area. They are made by rubberizing dipped fabric on calendar and then cutting them by bias cutting machine. Breakers are used mainly in biased tires where as in radial tires they are replaced by steel belts.



During rotation the carcass transmits all the forces on to the ground through the tread at contact patch. The tread being a rubber mass undergoes considerable deformation while transmitting these forces as well as engaging on the road deformities. This deformation of tread cause excessive stress strain concentration at tread to carcass interface and consequent premature failures. In order to dilute this concentration, a graded structure is opted for biased carcass in which the outer most layer in contact with tread are low modulus suspended plies, or breakers with high gauge of rubber insulation (Low EP (840/2) followed by intermediate layer and real pressure bearing inner plies.



The EPI (ends per inch), i.e. number of cords per unit area is much lower than carcass plies. This helps for rubber compound penetration between the cards which help in achieving better bond between tread and carcass as well as it provides impact resistance.

In general the function of breakers can be summarized as


i) It provides stability to the tread and helps in distributing forces uniformly throughout the tire structure.


ii) Breakers hold the tread firmly to carcass and also help in providing impact resistance to tread region.



OFFCENTERING



Off centering is actually the displacement of breaker from the central position in a band or a tire building drum. This defect can occur mainly during two stages of tyre construction; they are band building and tire building.



Off centering of breakers in tires can lead to;


1) Tread shoulder separation

2) Reduction in tyre life due to early failures.



To study about off centering of breakers mainly we deal with 2 departments



1) Band building department

2) Tire building department




Band building


In band building department the components of carcass, i.e. the inner liner plies and ply squeegees are assembled to form bands. Usually for a truck tire mainly 3 bands are employed.



First band - it consists of the inner liner, plies and ply squeegees. First the inner liner is applied to drum followed by 3 plies with 3 ply squeegees in between.



Second band - It consists of 3 plies with 3 ply squeegees in between


Third band - it consists of 2 plies, 2 ply squeegees and 2 breakers.


Band is usually constructed in a band building machine. Band building machine consists of a metallic drum driven by a shaft, containing a canvas that is held by a tension bar beneath it. During construction of bands the plies are placed in opposite direction. This is same in case of breakers also. The placement of breakers in 3rd band should be in such a way that distance of breaker from both ends of ply should be zero or less than 5. When the difference is more than 5 which is the tolerable value the band is said to be offcentred.


Off centering of breaker in band building machine can occur mainly because of



1. Machine related problems like


a) Canvas shift

b) Tension bar alignment

c) Light setting vibration



2. Material related problems like

a) Variation in width of incoming material



3. Worker related problems like

a) Error in adjustment of light setting

b) Stretching of plies and breaker during band building



TYPICAL BAND BUILDING MACHINE





Tire Building



In tire building process all the components of a tire are assembled to make a raw tire called green tire. The building machine consists of a metallic drum, which is mounted on a drive shaft. The ends of the drum are flanged to suit the bead configuration of the tire to be built. In all cases the overall diameter of the drum exceeds the nominal tire diameter. This difference is known as drum crown height and varies from tire type & size. Radial ply tire require complex and costlier machinery having inflatable textile reinforced diaphragms, overlying a skeletal metal drum shell, to shape the carcass plies and other components up to the diameter for belt fitting.



In tire building machine there is located a bead carrier ring on either side of the drum. This ring is concentric with the drum and is capable of moving inwardly to provide an interference contact with the drum shoulders and there by transfer and consolidate the tire beads against the partly build casing structure. In the carrier ring frame, there are inbuilt spring steel fingers, which forms a circle turn the plies down the contact shoulder of the drum immediately before the beads make contact. Attach to the building machine base plate and to the rear of the drum are two pneumatically operated component consolidating assemblies each comprising two pairs of shaped disc rollers. The rollers of one assembly are located on either side of the drum and pivot around the tire bead area for the purpose of turning and interlocking various components around the bead. The pair of rollers forming the second assembly traverses laterally, out word from the central line of the drum to consolidate the sidewall elements of to the carcass. In case of ply building system servicer is placed at the rear of the machine. More common is to build bands of plies before building tire. Bands with 3 to for plies are assembled together on band building machine. No of plies in a band depends upon the service requirements. No. of bands in a tire also depends upon the service requirements. The diameter of the band is kept lower than that of the drum.

Drum is collapsed, the two beads are placed on the carrier rings and the drum is expanded. A rubber base adhesive is applied to the drum shoulders. First band is then slipped over the drum under rotation with the help of the stick to apply pressure at the edges. The bead carrier ring assemblies then automatically turn down the ply edges around the drum and consolidate the beads. This is followed by the other bands and the second bead, in between the ply edges are turned around the beads. Then the chafer strips are applied and down with the ply edges. After this tread is applied and consolidated followed by applying of side walls on both sides. Final consolidation is done by traversing rollers. On completion drum is collapsed and green tire is removed from the building machine.



In case of radial ply construction (which differs from biased ply construction in the angle of orientation of chord in the plies) different approaches are followed. Earlier building and shaping operations were carried out on different machines. But in modern industries both the operations are carried out in the same machine.



Offcentring of breaker in tire building can occur mainly because of


1. Error in light setting




REASONS FOR OFFCENTERING IN BAND BUILDING



Machine Related problems.


1. Canvas Shift


In a band building machine, bands are constructed over an in extensible canvas that holds the tension bar and the drum. Depending upon the nature of bands to constructed different canvas is used. The canvas lies holding the building drum and the tension bar. During band construction first the canvas is inserted over the drum by keeping the tension bar in closed position. After insertion on the drum, the tension bar is lowered; this keeps the canvas held tightly over machine. Now plies are rolled over canvas and then made into a band. For the proper construction of a band it is necessary that the canvas should have the same perimeter in both the side (machine side and operator side). In case there is variation in perimeter in both side (i.e., difference between perimeter in both sides is greater than 10) then canvas shifting will occur. I.e. canvas during construction of band will move from one side to another over the building drum. (That is canvas moves from area having lesser perimeter to be having more perimeters). In such cases when the builder places the breaker on to the drum, over the plies this shifting movement causes breaker to be placed in such way that distance of breaker from ply ends unequal.



When the canvas shifts whole ply which is placed over the canvas also shifts then builder places. The breaker onto the ply according to the light setting which is incorrect then. The result will be huge difference in distance of breaker from both ply ends. The region of canvas with higher perimeter will have distance of breaker from ply ends greater than the other region of canvas with lower perimeter. The ultimate result will be off centering of breaker.



b) Tension bar alignment



Every band building machine consists of a iron bar with a rubberized coating over it placed below the building drum. The main function of tension bar is to hold the canvas in position. The tension bar is usually placed as a cant lever. Now the alignment of tension bar is critical for production of an okay band. The correctly aligned tension bar will have same distance from building drum with canvas in open position that is difference in distance between tension bar and building drum should be zero. If the difference exceeds 10mm then it will put more pressure on 10 the canvas inducing canvas shifting. This will lead to off centering.



c) Light setting vibration


Every band building machine consists of a light setting (which consists two to three laser beams)


Three laser beams are placed with respect to the edge of band building drum


1. First beam for correct placement of plies.

2. Second and third for correct placement of I and II breakers worker places the breakers and plies to form a band based on this light setting if there is vibration in this light setting because of some kind of machine problems then it will induce the worker to make an off band or offcentred band. Since vibration causes variation in distance set on drum.



2. Material related problems



a) Variation in Incoming material


Fort he purpose of making an ok band, it is necessary that the plies and breakers should have some specified dimensions. When plies and breakers are concerned width forms main area of concern. It is based on this width that light setting in done in band building machine. For example is apply is having a width of 845mm, first breaker - 415mm and 2nd breaker 210 mm the light setting is adjusted in such a way that distance of first breaker from ply ends is 317.5mm and that of 2nd breaker is 215mm. But this speficaition work only if width of all these components comes in the tolerable range (ie ±5m). Whenever the width of breakers and plies exceeds more than 5mm, it becomes difficult to centre the breaker correctly on the band building drum.


[Even if builder changes to set the breaker correctly on onside because of incoming material width variation the distance of breaker may very badly on other side, leading to off centering]



The breakers and plies are given a tolerance of ±5mm when the width exceeds 5mm or goes down below 5mm it may lead to off centering. In coming material variation occur mainly due to problems in bias cutting.


3. Worker related problems



i) Error in light setting adjustment



Each band building machine consists of a light setting comprising of three laser beams over the drum. Three laser beams are provided over the drum with respect to drum edges. First beam for placement of ply, 2nd and 3rd for placement of breakers. For the purpose of building a correct band it is necessary that this light setting adjustment is done correctly by the builder. When the builder creates some error in this light setting the result will be variation from specification, which will ultimately lead to an offcentred band.



2) Ply stretch during band building



Since plies and breakers are rubberized fabric they are likely to be deformed when they are excursively stretched when plies or breakers are stretched it will lead to reduction in width of both plies and breakers. When width reduces below a tolerable limit say 5mm, it becomes impossible to centre the breaker on the band building drum. The ultimate result will be correct reference distance on. One side of the band and incorrect distance on other side. (That is huge difference in distance between breakers from ply ends)



REASONS FOR OFFCENTERING IN TIRE BUILDING



In tyre building the only chance of error likely to occur is in light setting.

After bands are made they are inserted on to the tire building drum for making green tire. During insertion of band care should be taken to see that the breaker comes exactly in the centre of the drum i.e., distance of band edges from either side of building drum should be equal. In order to center the band perfectly, light setting is provided at both the ends of the building drum. Light setting consists of a laser beam fitted on to the top of a steel rod placed parallel to axis of building drum. For the perfect centering of band on the tire building drum the edge of band inserted should coincide with the laser beam. As the distance of band edge from light setting increases off centering also increases.




METHODOLOGY


ACTIVITIES


BAND BUILDING



Studies for off centering were carried out on 4 band building machines building the 3rd band.


1) Machine related problems


a) Canvas shift


i) All the machines were examined for any kind of technical defects which could affect off centering.

ii) Perimeter of canvas was taken in both machine side and operator's side. [Dimensions are measured after removing canvas from the band building drum]

iii) Shifting of canvas for 3 revelations of drum are noted. (3 revelations forward and backward)



b) Tension bar alignment



Distance of tension bar form the band building drum is noted with canvas and without canvas. 3 check points are made i.e., perimeter of canvas in operators side, middle and machine side). The distance between drum and tension bar is noted in closed and open position without canvas also.



c) Light setting vibration

i) Light setting is checked continuously after every 3 bands made.

ii) Material related problems

- Breakers and plies from bias cutting departments are continuously checked for width variation.

For every breaker and ply both upper and lower part are examined for width variation. Cut to cut variation is noted.



3. Worker Related issues


a) Light setting variation

Error in Light setting is a worker related issue so every worker is examined for any kind of variation in light setting. So each worker is examined for correct light setting every machine is surveyed for minimum 3 workers.

b) Stretching of plies and breaker closing band building

- The process of band building requires some kind of force to be applied on to the plies and breakers for the purpose of making a band. Plies from conveyer are pulled on to the building drum to form the band. The breakers are also applied in the same way. To see whether stretching has any affect on off centering first points are marked on the ply before it is made into a band and its width is noted. The dimensions are again checked after the ply is made into a band at the same point marked. The same procedure is carried out for breakers also.

Tire building

Light setting validation is done in tyre building section studies conducted include:

Centering of breaker on tyre building drum.




RESULTS




Band building


The following conclusions were made from the study

.


1) Incoming material width variation


a) Variation in width of incoming ply material were found to be 7mm more than the specified value.


b) Variation in width of incoming 1st breaker was found to be 10 mm more than the specified value. Rare cases recorded shows deviation of 8mm lower than that of specified value.


c) Width of 2nd breaker was found to vary badly when compared to plies and first breaker. The deviation of actual values from the specified values was found to be about 10 mm.

The above mentioned variations were sufficient to cause breaker off centering.




2) Machine related problems


a) Survey was conducted on four band building machines.

Out of four machines two machines showed higher canvas shift of about 12 to 15mm which is very high.

This data pinpoints the role of canvas shift in off centering.



3) Worker related problems


a) Ply stretch during band building

Stretching of plies during band building could cause only around 2mm to 3mm reduction in width which is negligible.

Both first and second breaker width was found to reduce by 2mm to3 mm during band formation


Studies conducted indicate that ply stretching has no significant role in off centering of breakers in band building.


b) Error in light setting

Light setting variation for first and second breakers was checked for 6 operators.

For first breaker, out of 6 operators, 2 to 3 operators were found to vary reference distance by more than 5mm from spec value.

For second breaker 1to 2 operators were found to vary reference distance by about 5mm more than specified value.

The above data clearly indicates the error in light setting which shows that it has a significant role in breaker off centering.



Tire building



Light setting validation was done in tire building section.

Data collected from tire building did not show any kind of variation

From the above data it could be concluded that only source of off centering issue in tire building is off centered bands



CONCLUSIONS


The following conclusions were made from the studies conducted




BAND BUILDING




Ø Incoming material variation seemed to be the main material related problem that caused off centering of breakers

Ø Out of all machine related problems canvas shift proved to be the main reason for breaker off centering.

Ø Other machine related issues like light setting vibration and tension bar alignment did not have any effect on off centering.

Ø Main worker related problem that caused offcentering of breakers was the error in light setting

Ø Other worker related issues like stretching of plies during band building did not have any significant effect on off centering.





TYRE BUILDING



Ø Data collected from tire building did not show any kind of variation

Ø From the above data it could be concluded that only source of off centering issue in tire building is off centered bands

Ø So the best possible option for improvement of breaker off centering is to reduce the above mentioned problems.

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