Stronger than Steel..!!

On 16th Dec 2010, I had the most fascinating day since I started doing my masters. I got an opportunity to visit National Aerospace Laboratories (NAL) which one of the research labs under Council for Scientific and Industrial Research (CSIR) along with my fellow classmates and few faculty members from my department in one of the college vans.

On arrival at NAL, we were received by the a person from the Public Relations office of NAL who gave us a brief introduction about NAL and its history. We also got to see a small video about the institute and the work they have carried out till now and also about the on going projects. Then we were guided to another campus a bit further away from the main NAL campus where we met few scientists, who told us that they have a carbon fiber manufacturing plant housed in that facility and they are going to show us around and also let us inspect the equipments . We split into 2 groups and each group was shown around the plant by a team of 2 scientists. They explained each and every step that takes place during the production and the different reactions, reaction conditions etc that takes place in the plant. They were giving out loads of information out of which few things went over my head as I could not comprehend few of the stuff they were talking about. But still I managed to understand a bit of it which I am trying to put out in words.

And in order to make this a bit more informative, I am writing everything that I can recall after the trip in the next few paragraphs. This will sound more like a report than a log. So, Brace yourselves..!!!

NAL and Carbon fibers:

Carbon fibers are important strategic raw materials for fabrication of advanced composite materials. Carbon fiber polymer matrixes are used extensively as light weight structural materials in a large number of applications. Some of the areas where carbon fibers are widely used are: Aerospace structures, Wind Turbine blades, sports equipments, off shore platforms and transportation.

Carbon fiber composites provide very high strength, stiffness and very low weights to the products. These composites can be used to fabricate structures with complicated shapes and sizes with a relative ease. Carbon fiber composites are in use since the past 2 decades in many fields, but all these years India was relying on overseas suppliers for procuring carbon fibers for strategic applications. In order to minimize our dependency on overseas suppliers, CSIR-NAL along with DRDO-ADA initiated research and development towards the development of the production technology for carbon fibers and after a lot of effort, they have managed to design and set up a pilot plant for the production of carbon fibers.

This fully functional plant is located in the NAL facility in Bangalore and manufactures the carbon fibers having a diameter of 7 microns and a density of 1.8 gm/cc.

Among the different methods available for manufacturing the carbon fibers, here they make use of a synthetic polyacrylonitrile polymer which is carbonized by subjecting it to a variety of process in order to get carbon fibers.

The plant has the capacity to synthesize 35kg of polyacrylonitrile per hour and this is done by mixing the Monomer acrylonitrile with other co-monomers like Etagonic Acid, Acrylic acid acryl amide along with water in a CSTR . Here Iron is used as a catalyst to promote polymerization. The polymerization process is a exothermic reaction and in order to maintain the rate of reaction , the heat liberated in the CSTR is removed by passing brine through the outer jacket of the CSTR. The resulting polymer mixture will be a highly viscous and also contains unreacted monomers and water along with it which has to be separated which is done by passing it through a stripping column which is a tower packed with steel packing and the pressure maintained at 150 mmHg inside the tower. The reaction mixture is heated to about 50-60 C to vaporize the monomers and separated. The water is removed by centrifuging the polymer mixture is basket centrifuges at speeds of 4Gs . The remaining polymer is dried using rotary vacuum driers and the obtained polyacrylonitrile powder is stored for further processing.

In the second stage the polyacrylonitrile fibers are manufactured. This is done by mixing the polymer powder along with dimethylacetamine in order to obtain the spinnable dope. This dimethylacetamine is known as coagulant in this process and it forms slurry with the polymer making it easy spin the polymer yarn by passing the mixture through the spinneret to spin the polymer yarn of 50-60 microns diameter. The spinneret is made out of Gold- Platinum and it has 6000 holes of 50 microns each to spin the polymer yarn. There are other spinnerets with 3000 and 12000 holes as well which are used depending upon the requirements. The polymer coming out of the spinneret passes through the coagulant bath where the coagulant will be removed and only the polymer is left behind in the yarn (fiber) spun. The fiber is then made to pass through a series of rollers running at varying speeds in order to stretch the fiber. The final roller will be running at 10- 12 times the speed of the first roller. This also means that the diameter of the fiber would have also reduced from 50- 60 microns to around 12 microns by the end of the process. The fibers are passed through the spin finish during the rolling process in order to obtain a smooth finish as well as to prevent building up of static electricity between the threads. The polymer fiber finally obtained is made into rolls and stored until it is subjected to the next process.

Once the polyacrylonitrile fiber is produces, it has to be subjected to carbonization in order to remove the elements like hydrogen and Nitrogen from the polymer so that only carbon is left behind in order to obtain carbon fibers. This is carried out by further processing of the polymer fibers. The fibers are subjected to 4 more processes in order to obtain carbon fiber.

The polymer fibers are heated to around 250 degrees for a period of 100 minutes using hot cross flowing air. This is known as stabilization process. Then it is passed onto a oven where the temperature ranges from 400-900 C and this step is known as precarbonization. At this stage the fibers have 58%-77% carbon. Then it is subjected to carbonization process in graphite lined ovens where the temperature is over 1400C in an inert atmosphere with nitrogen and devoid of oxygen. Then in the final stage the graphitization is carried out at temperatures ranging over 2600C. The obtained fibers will be 6-7 micron thick with 97-98% of carbon and this is rolled onto bobbins and stored.

These fibers are used to manufacture carbon fiber laminates by sandwiching it in between 2 layers of resin. These laminates and composites of carbon fiber have various uses in the aerospace & space programs, Motorsports, renewable energy and oil exploration and other fields.

This manufacturing process and the plants has been indigenously developed and it reduces the dependency of India on other countries for the supply of Carbon fibers, this provides a significant boost to the Indian defense and space programs.

The technology for the manufacturing of carbon fibers has been transferred to a Gujarat based Kemrock Industries and Exports Limited who has set up a carbon fiber plant and are planning to undertake mass production of the same.

Now, if you managed to read the whole thing without getting bored, I am all praises for your patience and interest and i hope this was informative.

Bleed it out...!!

I finally did one of the things I had in my ‘To do’ list. The phrase used for blood donation campaign- ‘Donate Blood, Save Lives’. I hope, the blood I donated will play a part in saving someone’s life. It was 26^th of October 2010 and there was a blood donation camp organized in our college. And I was thinking whether to go ahead and participate in it or not. And then I thought I should give it a try, so I made up my mind, overcoming the fear of the needle piercing through my vein I registered myself, got all my vitals checked by a doctor and then declared that I am fit enough to donate blood. And at last , they made me lie down and inserted a needle into my median cubital vein, after strapping the sphygmomanometer around my arm and pumping it in order to elevate the blood pressure which helps the blood to flow through the needle and then into the collecting bag which has anti coagulants and preservatives in it. Within 20 minutes the bag filled up and the donation process was over. It was a minute contribution from my side towards saving lives and I am ready to do it all over again.

Social message: People should get over their misconceptions regarding blood donations and they should actively get involved to help save lives. 'GIVE BLOOD, GIVE LIFE'.