Rubber Skill

1. In the Preparatory areas of a Rubber factory, next to Mixing, Extrusion is the most important process for the success of the downline operations such as moulding (Tyre, automotive seals, gaskets, mountings etc), hose making (inner & outer liners), power transmission belts (base profile), tubes for pipe lining etc. Besides, of course, Extrusion of direct production of various products such as automotive profiles, beadings, building profiles, garden hose is carried out. 2. For the production of in-house blanks (for Tyre tread, Bead wire coating, compression mouldings, V- Belt profiles, Hose tubes etc.) a good warm feed extruder is adequate, which has an added advantage of lower investment. For the production of finished products such as automotive & building profiles / beadings, which demand dimensional consistency & zero wastage cold feed extruder is ideal. 3. More than mixing & calendaring machines, Extruder machine design & construction plays a prime role in

The Rubber Research Institute of India (RRII) under the country’s Rubber Board, has developed a method to dry sheet rubber in a single day, instead of the traditional method that takes four to five days. Based on a report in the local press, RRII has been spurred on by the success of a pilot-level study by researchers and is now reportedly undertaking a larger-scale experiment to discover if the technique will work on a day-to-day basis for rubber farmers. It is estimated that there are around 1,320,000 small rubber holdings in the country and in comparison, very few large estates of 10 hectares or above. A total area of 823,000 hectares is covered under rubber cultivation in India, with natural rubber production amounting to around 715,000 tonnes per year. The small holders/farmers who are the main owners and operators of rubber plantations in India, prefer to sell their produce as quality sheet rubber (ribbed smoked sheets or RSS-4 grade) to earn a higher price in the market. The

1. Typical Calendar machine has 3 rolls (especially in non-tyre industry), though 4rolls would improve the quality consistency of the output, as well as productivity (simultaneous topping of both sides of the textile fabric at the same time). Ideally the Calendar machine should be of variable drive speed, for better control on process quality, minimal wastage during start-up & better productivity. Typical maximum speed is 15-20 mtrs/min. Also, the the lateral roll movements (nip adjustment) should be motorized. 2. Uniformity of roll temperatures is a primary condition for calendaring quality & hence steam quality should be right in terms of ‘dryness’ & inlet pressure should be low (typically around 2 kg/cm). If possible, individual roll can have independent pressure regulator valve. During pre-heating of the rolls before starting the process, calendar must be run in slow speed for temperature uniformity on roll surface as well as prevent roll structure deformations due to

1. If there are more than one type of Rubber in a formulation, they should be blended initially at similar Mooney Viscosity level, for uniform blending of the rubbers & subsequent mixing quality. Eg. NR should be masticated first to the mooney viscosity level of other synthetic rubber/s & then only blended. Likewise Synthetic rubbers in a blend should be chosen at similar viscosity range to facilitate uniform blending without any ‘hard’ spots. If the initial blending of the rubbers is not achieved to optimum level of uniformity, no amount of ‘repairing’ at later stages of the mixing process can help in achieving the original desired properties. 2. Compound batch volume should be matched with the mill size. Overloading of the mill will result in poor & inconsistent mix quality. 3. Weighing of Rubber, chemicals, oils etc. in a formulation batch should be under tight control systems. Weight tolerance limits should be within close limits of +/- 100 gms (usually for major,

1. RM sourcing should be from maximum 2 vendors only (baring very few exceptions), in order to minimise the variations, since no two sources can give identical quality / process characteristics of the same product. The identified sources should show very low variations in the critical properties of the product. 2. Test certificates must accompany every supply & should be verified to confirm it refers to the supplied lot only. Test Reports must mention results of mutually agreed parameter limits. 3. Each raw material should be tested for at least one critical property with close tolerance limits, every time (Eg: plasticity / mooney viscosity, melting point, ash content, softening point, flash point etc.), to keep a tab on Supplier QA. A trend graph should be maintained to check consistency of property. 4. Where complete test facilities may not be feasible in a typical MSME company, bare minimum facilities should include the following for the purpose of raw materials only: (a)

1. First priority is to select the right polymer / polymer blend to meet the final application requirements. Note that no amount of anti-degradants or other additives can compensate the wrong choice of base polymer, in meeting final application requirements. (Eg. NR cannot be equal to heat resistance of SBR & similarly SBR cannot equal NR’s wear resistance & tensile properties). 2. Selection of two or more polymers in a blend should be done after great deliberations, in order to meet application requirements; following points should be considered without fail: (a) Final Properties should be the combination of individual properties of the polymers, (b) Compatibility / Miscibility of Polymers, (c) Selection of similar Mooney viscosity grades for easier mixing, (d) Selection of curatives to achieve uniform vulcanising speed, (e) Ingredients chosen should be capable of uniform dispersion in the blended polymers, consistently meeting the final application requirements. 3. Choo