The Role of Profile
(Rubber Asia, Kerala, India) Rubber products are important to automobiles because they perform certain key functions better than any other known materials – functions that cannot be done by any material other than elastomers.
Profiles are the rubber products used by all types of automobiles – be it an original equipment manufacturer (OEM) or second-hand. In fact, profiles have the second major use of rubber in any automobile, after the tyre and inner tube together.
Some chief functions of the rubber products that are used in automobiles are: Traction for power transmission, reduction of vibration, isolation of vibration, seal for air, seal for contamination, seal for fluids, energy absorption for safety padding, flexible body panels, finder for friction materials, adhesives, gaskets, etc.
The first is related to tyres, while for all others, the automobile industry has to depend on different suppliers and their major challenge today is to find the right vendors who can supply the right product.
Selection of rubber
For any automotive rubber manufacture, the selection of rubber depends on the performance required. Rubber that is used can be NR, EPDM, IIR, CIIR or NBR. At present, the use of natural rubber (NR) in the automobile industry is limited only to tyre and, inside a car, restricted to floor mat.
Mostly synthetic rubbers are used in automobile rubber applications for their higher ageing properties. The positive thing about NBR is that it is very oil-resistant, but the drawback is that it has very poor ageing properties – it is subject to ozone cracking – almost similar to NR.
An automobile component manufacturer needs the following requirements to make the right product such as: Performance material, dimensions, construction sampling, description of test methods, packaging
The rubber used in automobile industries has to undergo specialised tests to control the elastomeric materials in those applications. The key requirement is that the rubber component should perform the job within reasonable cost.
Profile industry in India
India’s domestic automobile market has been growing by 14% in the last four years (2000-2005) and the auto component market also grew by 19% in the same period. The whole automotive industry contributes about 4.5% to the country’s GDP growth.
In India, the automobile component industry is emerging as a giant sector. From a production worth $6.7 billion in 2004-05, auto ancillaries are expected to touch $40 billion by 2015. The sector is absorbing new technologies and aligning itself to global development by becoming export-oriented.
Profiles are necessary in all types of automobiles for both OEMs and the replacement automobile market. The application of profiles in passenger car is comparatively high because of the rising number of car sales – the growth rate is nearly 12 % a year at present.
Some of the major OEMs in India are Maruti, Toyota, Ford, Hyundai, General Motors, Honda, Fiat, Telco, Skoda, Mercedes, Mitsubishi, Mahindra & Mahindra, Swaraj Mazda, Volvo, TVS, Bajaj Auto, Hero Honda, and Suzuki Motors.
In four years from now, the automobile companies in India will roll out more than double the number of cars and the total number will be over 3 million by 2010.
With increased market demand, there are more opportunities for rubber product manufacturers to modernise production operations. Modern machinery is being bought. Tangential mixers and intermix are replacing two-roll mills and kneaders. Cold-feed vented extruders are replacing hot-feed extruders.
The product moulding is being shifted from compression to transfer-injection and injection-moulding. The latter is in increased demand in the automobile industry owing to its quality and product volume. Flashless moulding techniques are being adopted very fast. Product finish is
gaining in importance with special performance additives in compounding and better mould
Raw material, labour cost, processing cost and utility cost are the key areas where profile manufacturers are concentrating on cost reduction. About half a million people are directly employed in this sector and about 10 million people depend on this sector for their livelihood.
Future growth evident
The future growth of Indian automobile industry is evident because of the following
factors such as: Economic growth of about 8% (7.6% in 2004-2005), a huge population of above 1 billion, average income of lower middle class and middle class people are increasing, constraints of the Indian Railways to meet the growing demand for passenger and goods transport, essential goods to rural areas and the farm produce from villages to cities are transported by road, development of the Golden Quadrilateral and North-South and East-West Corridor national highways, more and more capacity utilisation in automobile industries, continued thrust on exports by all automobile industries, easy financing for buying new and old vehicles.
Some of the major Indian profile manufacturers are: Anco (Rudrapur, Uttar Pradsh), Metzeler (Ghaziabad, Uttar Pradesdh), Precision Pipes and Profiles (Delhi), HS Chemicals (Chennai), Gold Seal (Daman), Roop Polymer (Sona, Haryana), RK Profiles (Faridabad, Haryana), Vora Rubber (Faridabad, Haryana), National Engineering (Kolkata), Pulsar (Kolkata), and SR Beadings (Gurgaon, Haryana).
Besides, there are about another 1,000 different unorganised companies making profiles for the replacement market. About 80 kilotonnes of profile compound is being manufactured in a year in India now. The figure will double in the next four years since, with increasing demand.
The Indian is market moving towards a price-driven market rather than product-driven. Winners in this market will be those who can operate at a low cost base and can innovate across the fleet management process.
Stress on automation, R&D
The Indian profile manufacturers are spending much time in identifying problematic business areas like stock-outs, high labour costs, shrinkage, defects, and high inventory levels. Positive pilot project returns may be a key goal when justifying investment in a relatively immature solution area.
Though labour costs continue to be lower in India than elsewhere, the manufacturers are keen to automate to reduce manual handling and thus eliminate human error. Recipe management system, weighing and batching equipment for raw materials, supervisory control and data acquisition for various equipment, stages of process interlinking through programmable logic controls, product weighment, and bulk carbon-black handling systems have been integrated while expanding capacity.
The industry is also driven by strong research and development (R&D) capabilities, both in-house and outsourced. Quality control has dramatically changed over the years. Rheometers, mooney viscometers, analytical equipment like DSC, TGA and FTIR are being procured by even smaller manufacturing units.
Whatever be the current trend in automobiles or whatever be the design of the vehicle, body sealing is a must in all automobiles. Body sealing is done by typically shaped and cured EPDM elastomers and it gives the dynamic link between car-body frame, which is static, and moving parts like window, door, etc. Elastomer sealing protects the vehicle from water, weather, vibration, noise, etc.
Technically, there are two categories of profiles and these are often called solid profile and sponge profile. The compounding, use and the manufacturing pattern of solid and sponge profiles are different. The primary functions of body sealing are: Water sealing, weather sealing, air and noise damping, sliding guide (window)
Based on the design of the vehicle, the number of rubber components in a vehicle changes.
The 4 main types of rubber components are: Foamed rubber (soft) for door, trunk, hood seal, dense rubber for glass run channel and fixed weather strip, metal carrier for belt line seal, stiff profiles for clamping of sponge or dense seal (co-extruded).
Quality of profiles
Profiles are made with compounded elastomers which are compounded with different ingredients, extruded with the desired profiles and finally cured in a continuous vulcanising system like microwave, followed by hot air (200-2100 C) fast-curing. Other curing systems are LCM or by jet-air/hot-air systems.
Though microwave curing is generally preferred, products of lesser quality made by the other two curing systems are consumed mainly by the replacement market in the small-scale, unorganised sector. In India, however, OEM profiles contribute about 65% of the market share, which is lower than in the USA, Europe and Japan.
The selection of elastomers plays a vital role in the quality of the profile. The challenges the automobile elastomers face are: Durability up to 140,000 km, reduced permeability emission, new technology to process polymers, fillers to enhance performance and reduce cost, single-stage mixing, fast-mixing, high-speed extrusion, improved oil resistance and low-temperature flexibility (40 o C) by modification of compounding ingredients, improved quality control with consistence in quality, zero-defect products.
EPDM rubber is preferred all over the world for making profiles. Other than EPDM, plastics, blend of plastics and elastomers, and thermo-plastic elastomers (TPE) are also used widely. The approximate EPDM consumption in the profile sector in India is close to 3.5 kilotonnes a year. While the specification for polymer content is a minimum of 25%, the Indian profiles contain nearly 30% polymer.
The properties that EPDM compounds require are outstanding ozone-resistance, excellent weathering stability, excellent heat-resistance, electrical properties and low-temperature flexibility, ability to accommodate a high volume of filler and oil owing to its chain mobility, excellent range of tensile and durometer, and grades with wider molecular weight distribution for easy processing.
Worldwide, almost all profiles and sealing systems are made with EPDM-based elastomers, compounded differently for suitability of customer requirement. Different designs of profiles are made by different dimensions of extruder head.
The weather-strip/sealing systems are: Tailgate/lift gate weather strips, quarter-window weather strips, cowl weather strips, secondary seals, backlite weather strips, belt strips, glass run channel, door weather strips, deckled weather strips.
Sponge weather strip seals are used for: Sun roof, door, hood to cowl, lift gate, deckled, window, flip-out window.
Though all profile compounding pattern and sealing systems are made with EPDM-based elastomers worldwide, this changes from place to place.
Moisture is poison for this product and so raw material with minimum levels of moisture must be used. Besides, substances like anhydrous calcium oxide, silica and gel are added to absorb moisture. Selection of raw materials and their sources are very important. Identification of sources of grit-free carbon and other fillers, including zinc oxide, plays a vital role in the industry.
The facility of sieving carbon black and other fillers in the factory premises can minimise rejection due to hard grit.
Two-stage compound mixing
The dispersion level of profile compound varies from 70% to 90% in different industries. High levels of dispersion of the ingredients also improve the durability of the product. The art of processing technology can help one achieve a dispersion level greater than 70% without altering the compounding ingredients (process oil). With higher filler loading, however, improvement in the dispersion level could be difficult.
In many industries, profile compound mixing is done in two stages. The first stage, or masterbatch, contains all ingredients except curatives. In the second stage, or final batch, only curatives are added. Single-stage mixing is also being practised in the industry, particularly for solid profiles.
To get better dispersion and higher dump temperature, the banbury volume is very important. In the case of masterbatch, the normal batch weight is 10%-20% higher than that used for a GPR-based compound. For an EPDM-based compound, it is better to use banbury fill factor between 0.85 and 1.0 for better dispersion of carbon black and zinc oxide. The dump temperature of master batch is kept at 160 0C +. With higher dump temperature, the possibility of blister due to moisture is also minimised.
For final batch, the batch weight is normally 80% of the master in the same banbury, and the dump temperature is maintained between
1000 C and 1050 C.
The starting temperature of the master and final batches should be ideally kept around
Adequate mixing time and dump temperature will depend on the following: Type of banbury (2-wing/4-wing chamber and tangent system/interlocking system), banbury volume loading, banbury starting temperature.
Black: Oil ratio in masterbatch, sequence of loading, dump temperature.
The raw material mooney viscosity of EMDM is measured at ML1+8@1250 C for better consistency because EPDM is creepy unlike GPR. For compounded material, however, ML1+4 @ 1000 C is all right.
During mixing, sometimes lump formation is reported and this happens in most cases owing to gel formation. The EPDM elastomer has three monomers and it is often difficult to control the macro-structure of the polymer during polymerisation, frequently resulting in gel (pseudo-cure) formation. This can be detected only by NMR and FTIR studies of the polymer.
Gel formation can be taken care of by: Changing to low-structure black, seduction of black loading, extensive mixing in open mill with narrow nip gap, additional mixing time in banbury for master batch, eliminating reclaim in formulation.
Key parameters in mixing: Moisture and grit in the ingredients are the two enemies of profile compounding, during mixing of carbon black and other fillers with EPDM rubber, enough time or shearing force is to be provided for better dispersion because EPDM has comparatively lower affinity towards carbon black than GPR, higher loading has little or no adverse effect on EPDM-based compounding, the major advantage of the use of EPDM is that it does not affect vulcanising properties with higher dosages of filler due its chain mobility, select high modulus black (N550) with high DBP (close to 136 +/- 4) value and dilute it with process oil.
This will give economy, better flow and control on the modulus of the compound. High structure and high carbon loading is also suitable for conductivity required for microwave curing. The combination of different types of carbon black is good provided the dispersion is also equally good. Different type of carbon black will have different affinity for EPDM rubber due to the difference in surface area.
It is better to avoid combinations of black. Carbon black with higher surface area will provide better green strength it is but difficult to get dispersed in EPDM rubber. Inadequate dispersion of black can create problems as porous extrusions and blister in vulcanisate.
Maintain the desired mooney viscosity and modulus of the rubber and this is the key requirement in the extrusion process. It is better to pre-masticate EPDM rubber either in banbury or in open mill mixing. This increases the acceptance of ingredients. In case of difficulty in pre-mastication, EPDM is recommended to be kept at hot house (60-800 C).
In hot house, FIFO system should be
The best manufacturing spacing is done with ‘I’-shaped floor with banbury at one end and the packing section at the extreme end. A 60×100-metre space is good enough for this purpose. The essential requirement is 5-6-metre space
for microwave oven (3-sets), 6-metre tube tunnel space for hot-air curing, and 6-metre tunnel space for cold-water cooling.
Extruded profiles used in car
After mixing, the next important processing is extrusion. Cutting costs, in the manufacturing processes can be achieved by analysing cost analysis on breaking down different component production, cost of utility, cost of process like shorter line, faster line speed, less finishing, scrap decrease and finally material rationalisation like reduction in inventory (less polymer and grade), continuous improvement in quality strategy, and continuity in innovation aspects for improved performance.
The Indian industry is at present facing challenges regarding improvement of the environmental aspects (polyolefin material, nitrosamine-free cure systems, emission/odour-free).
The major focus, therefore, must be on the following qualities: Colour stability and uniformity on class A surface profile, easy motion of movables on GR channel, replacing flock, noise reduction on sponge door seal, absorbing micro-motion of door.
Maintaining technical demand of coefficient of friction, COF = 0.25, improved adhesion on EPDM compound, easily sprayable on uncured rubber, cross linkable, elastic properties should have to maintain original elastic properties of profile, should be scratch-resistant and abrasion-resistant, should have the highest ageing properties – in humidity @ 700 C for 200 hours.