These fibers are synthetic textile fibres of high polymers which are obtained by esterification of dicarboxylic acids, with glycols or by ester exchange reactions between dicarboxylic acid esters and glycols.
The main raw materials required for the manufacture of polyester fibres are p-xylene ethylene glycol and methanol.
The use of Dimethyl Teraphthalate is preferred instead of Teraphthalic acid as the purity of the reacting chemicals is essential and it is easier to purify DMT than teraphthalic acid.
Production of Polyester Filament Yarn from Polyster Chips
The polymer is made by heating teraphthalic acid with excess of ethylene glycol (Both of high priority) in an atmosphere of nitrogen initially at atmospheric pressure. A catalyst like hydrochloric acid speeds up the reaction.
The resulting low molecular weight ethylene glycol teraphthalate is then heated at 280 deg C for 30 minutes at atmospheric pressure and then for 10 hours under vacuum. The excess of ethylene glycol is distilled off. the ester can polymerise now to form a product of high molecular weight. The resulting polymer is hard and almost white substance, melting at 256 deg C and has a molecular weight of 8000-10000. Filaments are prepared from this.
Spinning of Polyester Fibres
The polymer is extruded in the form of a ribbon. This ribbon is then converted into chips.
The wet chips are dried and fed through a hopper, ready for melting. This molten polymer is then extruded under high pressure through spinnerettes down to cylinder.
Each spinnerette contains 24 or so holes. A spinning finish is applied at this stage as a lubricant and an antistatic agent. The undrawn yarn is then wound onto cylinders.
This yarn goes to the drawing zone, where draw twist machines draw it to about four times their original length. This is hot drawn in contrast to cold drawing of nylon filaments.
For the production of staple fibres, the filaments are first brought together to from a thick tow. These are distributed in large cans. The tow is drawn to get correct strength. Then it is passed through a crimping machines, the crimps being stabilized by heating in ovens. It is then cut into specified lengths and baled ready for dispatch.
Manufacturing process of PET
Crystalline structure of PET
Properties of Polyester
At 65% RH and 70 deg F–> 0.4%
Because of low moisture regain, it develops static charge. Garments of polyester fibres get soiled easily during wear.
Polyester fibres are most thermally stable of all synthetic fibres. As with all thermoplastic fibres, its tenacity decreases and elongation increases with rise in temperature. When ignited, polyester fibre burns with difficulty.
Polyester shrinks approx 7% when immersed in an unrestrained state in boiling water. Like other textile fibres, polyester fibres undergo degradation when exposed to sunlight.
Its biological resistance is good as it is not a nutrient for microorganisms.
Swelling and Dissolving
The fibre swells in 2% solution of benzoic acid, salycylic acid and phenol.
Alcohols, Ketones, soaps, detergents and drycleaning solvents have no chemical action on polyester fibres.
Polyester fibres have a high resistance to organic and mineral acids. Weak acids do not harm even at boil. Similarly strong acids including hydrofluoric acids do not attack the fibres appreciably in the cold.
Uses of Polyester
1. Woven and Knitted Fabrics, especially blends.
2. Conveyor belts, tyre cords, tarpaulines etc.
3. For filling pillows
4. For paper making machine
5. Insulating tapes
6. Hose pipe with rubber or PVC
7. Ropes, fish netting and sail cloth.
Organic farming is a form of agriculture that relies on techniques such as crop rotation, green manure, compost, and biological pest control. Organic agriculture is an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. Organic farming is involved with the natural methods like crop rotation, biological pest control, compost etc. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony. Organic farming is a concept with stringent guidelines for certification. There are a number of techniques that are well suited for organic cropping. In organic farming farmers are required to use traditional farming techniques along with relevant technology to help get enough produce and ease the process. The techniques are based on biological processes and usually come under the field of agro ecology. There are a number of websites that help the farmers in understanding different farming techniques. Several environmentalists and consumer protection organization have claimed that the use of synthetic pesticides not only damages the environment but also have an adverse impact on the quality of food. Pests and insects easily get adapted to the effects of the chemicals involved in them and so these pesticides lose their worth. Sooner or later it damages the health of the final consumer who unknowingly consumes a large amount of lethal chemicals and synthesized materials along with the natural food.
You can make use of organic farming to turn your dreams of safe and wholesome food into reality and the best part is it is already benefiting millions of people. The policy makers are also promoting organic farming for reasons like – sustaining rural economy, improving soil health, creating good environment etc. In India, organic farming has been in practice for decades. Organic farming is of great importance and there are a number of benefits of organic farming.
Some of the benefits of organic farming –
Organic farming is very cost effective compared to the conservative farming. Moreover, this farming is not very tiresome, time taking or difficult.
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S.R.S.Raghuwanshi, O.P.S.Raghuwanshi, M.S.Raghuwanshi and Lekhraj Yadav
J.N.K.V.V Campus College of Agriculture, Ganj Basoda, District Vidisha (M.P.) 464 221
WHO recently advocated trials and assessment of methods previously thought to be on the border of what was considered “ethical means”, thanks to the Zika outbreak earlier this year. This was in relation to the use of genetically modified mosquitoes to break the chain that has troubled mankind for thousands of years.
The boundaries of what is “ethical”, what is “correct” and what is “the right thing to do” have now blurred.
The correct thing to do would be for us humans to remain within the ecosystem and not as an outside agency for whom the earth and her environment were tools for exploiting. The ethical thing would be to refrain from meddling with nature
The right thing, perhaps, is to be neither a spectator to the devastation caused by nature, nor to needlessly meddle with it; yet take some bold steps when needed.
We have the distinction of wiping away hundreds of species of plants and animals off the face of the earth. A natural rate of 1-5 species is considered normal – the background rate. However, we are now losing species directly or indirectly to human activity at over 1000 times the background rate. Around 30% of the known invertebrate of the species evaluated at risk of extinction.
And therefore a question that often arises is, why couldn’t we, or rather, why shouldn’t we do it to those delicate looking tiny insects – the mosquitoes?
The general nuisance created by swarms of these biting, buzzing creatures is nothing compared to the amount of morbidity and mortality they cause. About 3.2 billion people are at risk of malaria. – This is around half the world population. According to a WHO report (December 2015), there were 214 million estimated cases of malaria in 2015 with 4,38,000 deaths. Similarly mosquitoes transmit dengue, chikungunya and zika. An estimated 5,00,000 people with severe dengue require hospitalization each year worldwide, a large proportion of whom are children. About 2.5% of those affected die.
They don’t play such a critical role in the ecosystem that can’t be compensated for either. Some entomologists believe that their role as pollinators and as food for predators can be easily taken over by other insects. Others think their absence would impact the ecosystem significantly, at least for a while.
The food for thought is that there are around 3.5K species of mosquitoes and less than 1% of them are vectors for serious human diseases. What harm would selectively eradicating them do? And considering the advances in science, how difficult can it be?
How do we get rid of them?
The most advocated and the least ecologically damaging method is that of self-protection through use of nets, clothing and repellants. But everyone knows that the benefit is limited.
Advanced science is now looking at mosquito traps using agents like carbon dioxide, warmth, odour producing chemicals that mimic mammalian presence to attract and trap mosquitoes.
Biological means like the Gambusia species of fish ,dragonflies ,mosquitofish etc also have been tried.
Integrated pest management involves use of more than one method depending on the environmental conditions, types and distribution of mosquitoes, seasonality and other factors.
All these are applicable for isolated areas for relative control and by no means look at the big picture.
Use of pesticides is fraught with its own set of issues including accumulation of the pesticides in human food chain and its adverse effects like nerve disorders, various cancers, endocrine disorders and a long list of relatively minor problems.
More sophisticated means now under study have adopted a humane approach rather than charging at them with chemicals.
Using lab grown genetically modified mosquitoes to be released in the environment is one method. These transmit their genome to the offspring making them sterile or shortening their lifespan or disrupting the parasite’s cycle inside the mosquitoes. This method can be customized to affect a specific species at a specific point in their genome and therefore can be highly controlled.
However easy this sounds in theory, in practice, it will need to be a massive project orchestrated to precision and rolled across the world while grappling with the reality of not being able to cover the entire mosquito population or random and unforeseen mutations amongst the mosquitoes making the whole thing ineffective or partially effective
Then there are ethical borderline concerns like a more dangerous species developing or a cascade of ecologically disruptive consequences.
Therefore, for now, while technology is available, we are still struggling with pain, sickness and even death in this longstanding battle against the mosquitoes.
About Author: Dr Sona Sharma
Pic: ASTROSAT before it’s launch at ISAC Bengaluru
India’s first multi-wavelength observatory ASTROSAT was launched on Sept 28, 2015 from the first launch pad of Satish Dhawan Space Centre at Shriharikota, Andhra Pradesh at 10 am by Polar Satellite launch vehicle (PSLV- C30). The satellite weighed 1513kg is launched into a 650km (around 404miles) orbit inclined at an angle of 6° to the equator. It is launched with a life-time of five years. Total cost of the project was approximately 180 crores. Prior to this mission, India was mainly focusing on communication, navigation, education, earth observations but this was the first time when Indian scientists worked for a dedicated astronomy mission.
Conceptualization of India’s astronomy mission was started in the year 1996 and a project report outlining the mission was submitted in 2000. In 2002 the project got approved by Indian Space Research Organization (ISRO) with the grant of seed fund. Later, in 2004 the mission gained approval and full funding from Gov. of India. The mission was aimed to be launched in the year 2011 but due to some technical issue it has suffered a long delay. Resolution of technical issues and prelaunch testing of instruments was complete by Aug 10, 2015. The satellite was assembled at ISRO Satellite Centre (ISAC), Bengaluru and finally placed into orbit on Sept 28, 2015.
Why ASTROSAT was needed:-
The universe has always been a fascinating subject. Ever since the dawn of human civilization the mysteries of universe has been drawing the curious minds of the societies to study the universe. It was this thirst of curiosity which first led to assumption about outer space, different stars, and distance between them, followed by dedicated study in this field. The space science started booming after the development of telescopes that was further led to new height with the development of ground based astronomical observatories. The ground based observatories provided the scientists a peep through the Earth’s atmosphere into outer space. With the advent of time and technology scientists felt a need to develop a space observatory as ground based observatories suffered many limitations, prime being the atmospheric distortion. A space observatory is any instrument (such as telescope) in outer space that is used for observing distant planet, galaxies and other outer space objects. India already had ground based telescopes like Giant Metrewave Radio Telescope near Pune and Indian Astronomical Observatory in Ladakh. Ground based telescopes have limitations of detecting radio-waves and infrared radiations only, as these penetrate the Earth’s atmosphere. Moreover ground based observatories had to contend with atmospheric turbulences and suffer light pollution and daylight problem. Indian scientists had to depend on international resources for the study of entire radiation bands. If India wants to be at the forefront of worldwide scenario of space technology it cannot afford to rely on foreign data resources for longer period of time. The time had come when India felt the need for development of its own indigenous space observatory and Indian scientist came up with the idea of India’s first astronomy mission “ASTROSAT”. ASTROSAT is targeted to observe distant celestial object in full electromagnetic spectrum range in order to have better understanding of our Universe. It is for the first time any space observatory would be observing the universe in such a broad range of wavelength. Multi-wavelength observations of ASTROSAT can be further extended with co-ordinated observations using other space crafts and ground based observations.
Uniqueness of ASTROSAT:
Pic: Payloads of ASTROSAT
ASTROSAT has five payloads which have been developed by ISRO in collaboration with four Indian Institutions and two foreign organizations. The payloads of ASTROSAT will facilitate a deeper insight into our universe. It will help in monitoring the various astrophysical processes occurring in the various types of astronomical objects in space. These payloads relay on the visible,UV and X-rays coming from distant celestial sources. The payloads of carried by ASTROSAT are as follow:
1. Ultra-violet Imaging Telescope( UVIT) :– UVIT was developed by the Indian Institute of Astrophysics, Bengaluru, and the Inter- University Centre for Astronomy and Astrophysics, Pune. It consist of two telescope and three independent detector system. The detector in each channel is a photon counting image device which is capable of observing the sky in visible(320-530nm), near UV( 180-300nm) and far UV(130-180nm) regions of the electromagnetic spectrum. Multiple choices of filters are available in each channel.
2. Large Area X-ray Proportional Counter( LAXPC):– LAXPC was developed by the Raman Research Institute, Bengaluru, and the TATA Institute of Fundamental Research, Mumbai. It is a non imaging instrument. The main objective of this instrument is to record and study the variation of total intensity of sources within 1degree field of view with high time resolution and moderate spectral resolution of X-rays from sources like X-ray binaries, Active Galactic Nuclei and other cosmic sources.
3.Soft X-ray Telescope(SXT):– It was developed by TIFR, the University of Leicester, U.K., and ISRO. It has a focusing X-ray telescope fitted with a CCD imaging camera. It is designed for studying how the X-ray spectrum of 0.3-8kev and 2-10kev range coming from distant celestial bodies varies with time. It will work primarily in photon counting mode, recording the position, time and energy of every detected photon.
Pic: ASTROSAT instrument details
4.Cadmium Zinc Telluride Imager( CZTI):– It was provided by TIFR, IUCAA, ISRO. It has a hard X-ray coded mask camera which has a coarse imaging capability. It function in the X-ray region extending the capability of the satellite to sense X-rays of high energy in 10-100kev range.
5.Scanning Sky Monitor(SSM):– developed by ISRO satellite centre, Bengaluru, and IUCAA. It will monitor the highly variable X-ray sources in the sky. It is intended to scan the sky for long term monitoring of bright X-ray sources in binary stars, and for the detection and location of sources that became bright in X-rays for a short duration of time. The main purpose of SSM is to quickly detect suddenly appearing interesting sources.
6.Charged Particle Monitor( CPM):– a separate CPM is included as a part of payload to control operation of LAXPC and SSM instruments through zones of high fluxes of charged particles. A Scintillator Photodiode Detector( SPD) with a built in preamplifier is used for CPM.
The satellite was assembled at ISRO’s satellite centre, Bengaluru. Generally the payload mass is less than 10% of the mass of the satellite but because of the lower orbit ASTROSAT could afford to have heavier payloads. The combined mass of the payloads is more than the mass of the satellite.
The satellite during its mission life will be managed by the spacecraft control centre at Mission Operations Complex (MOX) of ISRO Telemetry, Tracking and Command Network (ISTRAC) at Bengaluru. The satellite will gather data of various astrophysical processes occurring in universe and will send it to ground station at MOX. This data will then be processed and distributed by Indian Space Science Data Centre( ISSDC). All major astronomy institutions and some universities in India will also participate in these observations. The archival data will be accessible to any scientist in the world from data centre.
Scientific Objectives of ASTROSAT:
ASTROSAT versus Hubble:-
The successful launch of ASTROSAT has marked several successes for India. Now India has joined the elite group of nations like US, Japan, Europe and Russia marking a fifth rank in the world when a space program has succeed in sending a space observatory. It is being considered as India’s Hubble with the uniquely of covering multi-wavelength bands. ASTROSAT mission has provided opportunity to Indian scientists to work in the frontier areas of high energy Astrophysics. Such missions inspire and motivate young minds and open new arena of research.
ASTROSAT had marked strong imprint on the success road of Indian space research following the step of its first successful mission Manglayan launched a year ago. The two consecutive successes were not only a morale booster but showed India’s capability in space research, drawing world’s attentions at India’s fast growing astronomy credentials.
Author:- Aastha Saxena