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Fire of Readymade Garment Industry in Bangladesh

Sunday, 30 June 2013

TAZREEN FIRE: EFFECT ON READY-MADE GARMENTS SECTOR IN BANGLADESH
Author: Syed Ansar Ullah
Dept. of Textile Engineering
World University of Bangladesh
Email: ansarwub@gmail.com




Introduction:
The readymade garment (RMG) sector plays a very significant role in the socio-economic development of Bangladesh with more than three million workers, mostly women employed in nearly 4,500 factories. Bangladesh is the world’s biggest exporter of clothing after China, with garments making up 80 percent of its $24 billion annual exports. The garment factories of the country make clothes for brands, including Tesco, Wal-Mart, JC Penney, H&M, Marks & Spencer, Kohl‟s and Carrefour. By 1982, the country had 47 readymade garment factories. In three years the number rose to 587. Now it has more than 4,000.

Factory fires and tragic deaths of helpless garment workers is a regular phenomenon in Bangladesh. Life of garment workers is so pathetic. Each year, Bangladesh faces fire hazards in the garments sector, and it’s frustrating, sad and astonishing to know that they have all been preventable fires. Despite repeated requests from concerned citizens who care, governments of past and present hardly took any practical actions to safe-guard the workers from this death trap.

There have been many garment-factory fires in Bangladesh since 1990; more than 400 peoplehave died. But the tragedy in Tazreen Garments in Nischintapur, Savar in 24 th November, 2012was by far the deadliest one in Bangladesh. At least 112 workers died in the incident and over hundred people are injured. The reasons of the fire are the subject of investigation, but the firefighters put the blame for the tragedy on the lack of fire exits.

TAZREEN FIRE –THE GROUND REALITIES
Background:
Bangladesh’s textile sector is concentrated in export processing zones in Dhaka and Chittagong. The textile industry includes knitwear, ready-made garments and some specialized textile products. The export from textile sector accounts for about 80% of the total exports from Bangladesh. Bangladesh now ranks third in world textile exports (by value), only lagging behind Turkey and China, US and Europe are the major export destinations for Bangladesh garments. There has been intensive strife in the garment industry sector through the years as workers‟ most basic demands for acceptable minimum wages; work safety and freedom of association remain unmet, while the protests and riots of workers are met with police and company repression. Low salaries, unsafe working conditions, lack of proper training methods, and other issues make the RMG sector as one of the most hazardous to work in. More than 500 workers have lost their lives in the past 5 years due to fires in various factories. Some of the major incidents of fires in factories in RMG sector include deaths of 51 workers in fire at Garib and Garib, Matrix Sweater and Ha-Meem Group in 2010, death of 65 workers in factory fire at Chitagong KTS composite textile mills in 2006, death of 20 workers at Narayangonj Sun Knitting in 2005, 48 workers killed in a fire at a garment factory in Narshingdi in 2004, 53 workers killed in 2000 in a fire at Narshingdi Chowdhury Knitwear, death of 22 workers at Mirpur Rahman & Rahman Apparels in 1997, death of 27 workers at Mirpur Tamanna Garments in 1997,and 27 killed in fire at Mirpur Sareka Garments in 1990.
Dead body of some worker due to burn in Tazreen Fashion
Accident A fire broke out at Tazreen Fashions, Nischintapur, Ashulia, Dhaka, Bangladesh on the night of November 24, 2012. The factory employed more than 1200 workers almost 95% of whom were females. The annual turnover of the factory was over USD 36 million. The major buyers include Wal-Mart, KIK GMBH, Teddy Smith Ace, C&A, Li & Fung,

“THE GARMENT FACTORY OWNERS ARE YET TO BECOME HUMANS. THEY ARE STILL OWNERS OF GARMENT INDUSTRIES” 

The fire resulted in the deaths of 111 workers and more than 300 workers were injured. This accident created an uproar against the existing work conditions in the RMG sector globally. Wal-Mart cancelled its import contract with this factory considering its inadequate

Occupational safety measures. There were multiple investigations undertaken by the government and the garment association (BGMEA – Bangladesh garment Manufacture and Export Association) which termed the fire as “pre-planned” and sabotage. The Bangladesh Occupational Safety, Health and Environment Foundation (OSHE) carried out an independent investigation into the incident to highlight the root causes and failures resulting in the large number of deaths and injuries in the incident. The team conducted field investigations, visited the factory site, met the workers and victims of the factory, met government officials and other Stakeholders.

The findings of the report were presented during a multistake holder consultation on “Safe Work at Garments Factories in Bangladesh: Lesson Learned from Tazreen Fire Accidents- Challenges and Way Forward” held at the CIRDAP Auditorium, Dhaka on January 7, 2013. A large number of people from different trade unions, NGOs, government agencies, victims, media, academics etc were present during the discussions.

Mr Omar Faruk of OSHE presented the findings of the investigations:
  1. There were no fire or emergency exits or stairways.
  2. There was only 1 main entrance and exit way which is situated on the ground floor which was in itself not wide enough to accommodate the number of workers in the factory.
  3. Fire extinguishers and other fire defense materials were inadequate and were not to be found during the fire.
  4. 111 workers lost their lives out of which 58 have been identified.
  5. 53 bodies are still unidentified
  6. DNA samples have been taken from the victim’s families and report is awaited. It was told that the results will be disclosed only when all samples are collected.
  7. Most of the workers died due to suffocation and burns. only 6 workers died due to fall from height
  8. The second floor collapsible gate was locked and the highest number of dead bodies (69) were recovered from this floor. Supervisors on the 2nd and 3rd floors stopped the workers from evacuating the factory when the fire alarm went off stating the alarm as a false.
  9. Owner did not follow building code, had a nine storey factory but had permission only for three floors.
  10. Raw materials were stored on the ground floor and in close proximity to the high voltage electric transformers which resulted in the flames spreading at a fast rate.
  11. The factory did not have a renewed fire safety certificate either.
  12. Compensation of BDT 600,000 has been handed over to 45 families so far out of 58 deaths.
  13. Almost 300 workers are injured, some seriously although BGMEA has so far prepared a list of only 63 injured workers. The OSHE team has compiled a list of 89 injured and 58 cases of death due to the fire tragedy.
  14. Only 40 workers out of 1200 had received a basic fire safety introduction.
During the meeting, Mr. Israfil Alam, the Chief Guest and Chair of Parliamentary Standing Committee on Ministry of Labour and Employment appreciated OSHE initiative for independent fact findings and criticized the report of the investigation conducted by Bangladesh Garments Manufacturers and Exporters Association (BGMEA) terming the accident as “sabotage”. He said the BGMEA report has been designed to save the employer of the factory and termed the report as ill motivated, defensive and biased. He demanded the immediate arrest of the owner of the factory. He concluded by saying that “the garment factory owners are yet to become humans.They are still owners of garment industries.” Brig. Gen. Abu Nayem Md. Shahidullah, Director General, Fire Service and Civil Defence expressed his dissatisfaction on the unwillingness of RMG factory owners to ensure fire safety provisions. He disclosed that every year 1500 fire accidents are taking place across the country. He emphasised on structural safety in the work places. 40 % of accidents occur due to short circuits. Sanjiv Pandita, Executive Director, AMRC, expressed deep outrage at the colossal loss of life, which is now unprecedented by any scale. We cannot control fires, as accidents happen. However fires should not kill so many workers; fire safety is the minimal basic that workers deserve. Providing safe fire passage is well known for more than a century since the „Triangle Fire‟ of New York in 1911, and if they are not there or remain blocked than this shows the apathy towards human life.4 Tazreen Fire – the Ground Realities

Mr. Shukkur Mahmud, Chairman of National Coordinating Council for Workers Education (NCCWE) emphasized on a National Policy for RMG Sectors. Criticizing the RMG owners Mr. Mahmud said that, the owners do not care for the rules and regulations of the country. He proposed to conduct a nationwide survey on occupational safety in RMG and the factories lacking the standards should be closed. He blamed the Government agencies for not carrying their responsibilities properly. He strongly demanded the arrest of the Mr. Delwar Hossen, owner of Tazreen Fashion Ltd. The victims of the fire spoke about the situation in the factory and narrated their traumatic experiences. They spoke about the supervisor who refused to let them out of the factory. They said that in order to escape and save their lives, they had to break the windows and jump out. Khaleda who was three months pregnant was forced to jump from the third floor (mercifully both she and her baby are not seriously injured), Ratna braved a jump from the fifth floor to escaping the advancing flames. Morsheda, Age – 30, Sewing Operator said that she was working in the evening of that fateful day. “Suddenly I felt that fire is moving to me, I tried to go down stairs but I was not allowed by the managers.

Finding no other alternatives, I broke the window glass with other workers and jumped below. I was able to save my life, but got injured seriously. I cannot move my hands properly and have partially lost my eye sight.”

Muhammad Syed Ali, Age – 40 said -”I was working on the 3rd floor, suddenly I heard the fire alarm and tried to go down to the ground floor, but my Factory Manager advised me not to go down. By this time the smoke engulfed me and I was not seeing anything. Rapidly I rushed to the window and escaped by jumping out. I was injured and shifted to mother and child care center and moved to Dhaka Medical College and Trauma Center. BGMEA paid for my initial hospital charges.”

Mr. Roy Ramesh Chandra, Chairman of the Bangladesh National Council (BNC) an affiliate council of the global union federation IndustriAll said the employers of Tazreen should be immediately arrested for the murder of 111 workers and compensation should be settled immediately along the lines of the Spectrum fire accident tragedy. The following recommendations emerged out of the consultation to address the needs of the Tazreen fire victims and for ensuring fire safety in the RMG sector of Bangladesh:

Short Term-
  1. Immediate, free and comprehensive Medical treatment for the injured workers and the traumatised community.
  2. DNA testing for unidentified bodies should be completed and report released without further delay
  3. National Policy on health and safety in the RMG sector should be formulated.
  4. Every factory owner should ensure the Bangladesh National building codes and fire safety guidelines are followed in their establishments.
  5. Formation of Fire Safety and OSH committees comprising of workers representatives (independently elected) on every floor of the factories during working hours. Members of these committees should receive appropriate training on fire safety.
  6. All workers should be provided adequate fire safety and OSH trainings, fire drills to be conducted regularly and refresher trainings provided.
  7. Adequate compensation to be provided immediately to all workers.
  8. There were demands made to arrest the owner of the factory and to try him for willful murders.
  9. Pressurize the buyers and brands to ensure that there are adequate safety provisions in the factories from where they are procuring their goods.
Long Term -
  1. Creation of a fund with contribution from the employers association, buyers, brands, workers and government to ensure social security and welfare of the workers.
  2. Strengthening of government structures like factory inspectorates and Fire safety, establishing a culture of accountability.
  3. Rehabilitation for the injured workers
  4. Government to ensure the implementation of the Bangladesh Labour Act 2006 and other relevant laws and International Conventions & recommendations on health and safety.
  5. Formation of mobile courts at the factory level to ensure that workers get speedy justice for their disputes.
  6. Self-regulatory codes and mechanisms should be dismantled.
  7. To consider power and fire safety clearance as pre condition of issuing license.
Fact Finding Mission to Ashulia :
The next day They visited the factory site at Ashulia, around 50 kms from Dhaka. They met with about 60 victims at the local primary school (the charred bodies from the factory were placed in the classrooms of this very school on that fateful day) who once narrated their harrowing stories of being forced to jump out of factory windows to escape death. We saw victims with bones broken in their spine, hands, legs, neck and hips. There were cuts, bruises and burns all over their bodies.

First aid was administered to the injured workers on the day of the accident but no other medical help has been provided since. The victims looked terrified and traumatized due to their experiences. Even the children were terrified and it may take many months of therapy for the community to overcome this catastrophe. Sahira has been mentally traumatized by the horrific fire and is now in constant fear of dying. Deepti was injured so seriously in her legs that she had to be brought to the school in a cart. She could not stand on her own. People with photos of their missing family members approached us hoping that we may help them to ascertain the fate of their loved ones who have 7 disappeared since that day. Sakina has lost her daughter, Abdul has lost his wife and daughter, little Raina has lost her mother, Roshani is missing her husband. There were many more heart wrenching stories. The family members left behind have nothing the look forward to and seemed to have lost their will to live. More than a month and a half has gone by but still all the deceased have not been identified. The injured are still waiting to receive free and comprehensive medical treatment and rehabilitation.

There is an urgent need to provide immediate and comprehensive medical treatment to these victims to enable them to regain their health and become employable again. Some are only hurt physically but most are hurt mentally as well. There is a need for rehabilitation of these victims some of whom were the sole bread earner for their families and now are facing a grim and uncertain future. The ultimate cost of development of the RMG sector in Bangladesh is being paid by these invisible workers who have sacrificed their lives and limbs.

They then went to the site of Tazreen Factory and saw the rampant and obvious building code violations in the building – no fire exits; building more floors than permitted, grills on windows, only one entrance and exit from the factory etc. We also saw the openings left behind by the broken industrial exhaust fans through which the workers jumped to escape death. The factory was surrounded by residences and if the fire had spread, it would have caused grave damages. Immediate steps need to be taken by all concerned and as Mr. Repon Chowdhury; Executive Director of OSHE stated during the multi-stakeholder consultation - “History will not forgive us if we fail to ensure justice for the Tazreen accident victims. Upholding the dignity and guaranteeing safe & decent work for all workers in the RMG sector of Bangladesh is an immediate necessity”.

Conclusion:
All nations are shocked and numerous protests from general people, civil society, NGO‟s, cultural group, national and international group has been shown on this incident. The present incidence may discourage foreign consumers from using the garments produced in Bangladesh where workers are in a vulnerable situation. Evidently, the buyers in the export destinationswill be watching with keen interest the measures taken to ensure safety standards and working conditions inside the garment factories. Otherwise, the second biggest exporter of readymade garments will have reasons to lose golden opportunities. In past the country saw some major fire accident in garments factories and not all of the report have come in light and these incidents are occurring quite frequently. Mountain indignation rose among the workers as well as whole nations against government‟s negligence to arrest the owners of the factory. The whole nation is waiting to see more action and proper justice of this incident and demanding the immediate trial of culprit and action to prevent such accident. So, strict implementation of appropriate fire code and system of accountability in all aspects of safety in the garments sector, are vital not only on the humanitarian ground, but it makes simple and justified economic sense.

Production Report of Silk Fiber in the World

Saturday, 29 June 2013


Production Report of Silk Fiber

Rakibul Islam Khan
Department of Textile Engineering
Ahsanullah University of Science & Technology (AUST)
Email: pl_20in@hotmail.com




Production of Silk Fiber:
Asia is the main producer of silk in the world and produces over 95 per cent of the total global output. Though there are over 40 countries on the world map of silk, bulk of it is produced in China and India followed by Japan, Brazil & Korea. China is the leading supplier of silk to the world with an annual production of 153942 MT (2006). India is the second largest producer of silk with 18475 MT (2006-07) and also the largest consumer of silk in the world.

For most silk producing countries, silk production is non-mechanized and family based. Production increases are therefore slow. Thailand and India fabrics are woven on hand looms, however power looms are increasing in India. Almost, all silk weaving is done on power looms in Vietnam, Brazil and Korea.

Silk has a miniscule percentage of the global textile fibre market—less than 0.2%. This figure, however, is misleading, since the actual trading value of silk and silk products is much more impressive. Silk is a multibillion-dollar trade; with a unit price for raw silk roughly twenty times that of raw cotton.

Worldwide silk production totals about a hundred thousand tones while the other natural fibres (cotton, wool) and synthetic fibres (nylon etc.) total in the tens of millions of tones. Being a natural product and relatively rare enables silk to maintain its value, however it must also have characteristics that create a demand. Any synthetic fibre has not duplicated the characteristics of these, but even if they are in the future, the natural product will remain in demand while there is consumer preference for natural over synthetic.

Though silk production is only about 0.2% of the total textile fibre production in the world, the production of silk together with other natural fibres doubled in the 20 years from 1975 to 1995, the production of synthetic fibres increased three fold.

Table: World silk production in comparison with other textile fibres (Thousand tons)

Bangladesh has no position in the world silk market as it produces only 40 MT of raw silk per year. Interestingly the production of raw silk remains more or less same over the years. The low amount of raw silk production may be attributed to scattered small scale farming of mulberry plantation and silkworm rearing. Due to small amount of cocoon production in different places no reeling industry has yet been established in the country.

Figure: Increment of silk production from year 1975 to 2010.
Only a few reeling units have so far been in operation in some places most of which are not fit for good quality raw silk production. As such the silk industries, mostly located in Rajshahi, have to depend on imported raw silk for fabric production. The extension activities of sericulture in Bangladesh are conducted at small-scale level, which is limited only with the landless and marginal farmers. It is mainly based on tree mulberry leaves except for Bholahat area under Chapai-nawabganj district where bush mulberry is cultivated for silkworm rearing. Most of the reapers of Bangladesh are landless poor and have no separate silkworm rearing houses of their own and as such they have to rear the silkworms in their dwelling houses where hygienic environment cannot be maintained for successful cocoon crop production. As a result sometimes silkworm diseases occur and cocoon production is greatly hampered.

Whenever Bangladesh Sericulture Board (BSB) gets fund through development projects they provide mulberry saplings to the farmers for plantation in the road and embankment sides. They also provide silkworm eggs to those farmers when planted mulberry trees become productive. But when the project period is over the extension activities are greatly hampered due to fund constrained as the next project sometimes gets approval after 2 -3 years. Again they have to start with new plantation of mulberry.

BSB has so far implemented 16 development projects during the period of 33 years since its inception in 1978. But it could not able to increase a tangible amount of raw silk production in the country. This is mainly due to lack of proper extension policy and cocoon production planning. The sericulture projects implemented by BSB were more or less similar and routine in nature, which did not help develop sericulture in the country.

To meet the local demand we have to produce about 300 MT of raw silk per year. BSB should continue the program without any interval to meet the remaining demand of raw silk. BSB need to develop Package of sericulture practices for small, medium and large scale farming with the technical assistance of Bangladesh Sericulture Research and Training Institute (BSRTI). Then draw attention to the interested farmers and enterprises for implementation of the programs.

Understanding About Count and Count Measurement System

Friday, 28 June 2013


Understanding About Count & Count Measurement System

Mustaque Ahammed Mamun
Department of Textile Engineering
Dhaka University of Engineering & Technology (DUET)
Cell: +8801723300703 
Email: mamuntex09@gmail.com



Linear Density or Count :
Count is a numerical expression that indicates the coarseness or fineness of a yarn.

According to Textile Institute, “ Count is a number indicating the mass per unit length or the length per mass unit of a yarn”.

Types of Yarn Counting System

Direct system  : Count is measured as the weight of yarn per unit length

If Count increase then Dia increase.

Count =

Indirect system : Count is measured as the length of yarn per unit weight.

If increase Count then decrease Dia

Count =

For Direct system Used formula,

For Indirect system Used formula,

Where,
  • N= count
  • L= sample length
  • l= unit length
  • W= wt. of yarn
  • ω= wt. unit
Types of yarn count :
  • Normal count
  • Conditional count
  • Average count
  • Resultant count
Relation between yarn diameter and count:

Assuming an apparent specific volume for cotton yarn is 1.1-

Specific volume of yarn is 1.1 cc/gm

The mass of 1.1 cc yarn = 1 gm

If the yarn count is N tex then, we get

The length of N gm yarn is 1000m

The length of 1 gm yarn is 1000/N m=100000/N m

So that, length of 1.1 cc yarn is 100000/N m

We know that,
Cross sectional area × Length = Volume

If yarn Diameter is d then,



Converting cm to inches and Tex to English count

Measurement of Yarn Counting System :
  1. Wrap reel and balance method
  2. Beasley’s yarn balance
  3. Knowles balance
  4. Quadrant balance method
  5. Sliver, roving count by measuring drum
  6. Count data system
  7. Auto sorter by Uster 
 

Phase Change Material and Their Uses in Textile Clothing


PHASE–CHANGE MATERIALS & THEIR USE IN CLOTHING

Bilal Rashid
Dept. of Garment Manufacturing
National Textile University, Faisalabad, Pakistan
Email: br.dmc.gcuf@gmail.com





INTRODUCTION:
PREAMBLE:
Whenever a material changes from solid to liquid it absorbs heat, and whenever a liquid changes to solid it releases heat. A material that is capable of absorbing heat energy or releasing heat energy, at a large-scale, is called PHASE-CHANGE MATERIAL.
 
PCMs & LATENT HEAT:
PCMs are also known as latent heat storage units. By latent heat we mean the amount of heat energy absorbed or released by a body, without any change in temperature, as a whole.

For instance, phase change from solid to liquid absorbs energy, whereas liquid to solid requires release of energy.
 
PCMs & ENTHALPY OF FUSION:
PCMs are known for their high enthalpy of fusion or heat of fusion. By segregating the two parts of ENTHALPY of FUSION, we can get a general idea of what is meant by this phrase,
  1. ENTHALPY means the measure of the total energy of a thermodynamic system or body. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.
  2. FUSION which is also known as MELTING, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid ordering of molecular entities in the solid breaks down to a less-ordered state and the solid liquefies. An object that has melted completely is molten.
CLASSIFICATION:
PCMs latent heat storage can be achieved through solid–solid, solid–liquid, solid–gas and liquid–gas phase change. However, the only phase change used for PCMs is the solid–liquid change.
 
LIMITATIONS:
  1. Liquid-gas phase changes are not practical for use as thermal storage due to the large volumes or high pressures required to store the materials when in their gas phase.
  2. Liquid–gas transitions do have a higher heat of transformation than solid–liquid transitions.
  3. Solid–solid phase changes are typically very slow and have a rather low heat of transformation.
WORKING OF PCMs:

1. Initially, the solid–liquid PCMs behave like sensible heat storage (SHS) materials; their temperature rises as they absorb heat.
 
NOTE: WHAT IS AN SHS?
An SHS or Sensible Heat Storage material is a system that works on the principle of SENSIBLE HEAT, whereas sensible heat is a term that is used in contrast to the LATENT HEAT. Because in case of LATENT HEAT the system e. g, ice keeps on absorbing heat constantly and the temperature around it remains the same till it has changed its phase to liquid. However, in case of Sensible Heat the body with the absorption or release of heat also causes consistent change in temperature in the surrounding.

2. Unlike conventional SHS, however, when PCMs reach the temperature at which they change phase (their melting temperature) they absorb large amounts of heat at an almost constant temperature.

3. The PCM continues to absorb heat without a significant rise in temperature until all the material is transformed to the liquid phase.

4. When the ambient temperature around a liquid material falls, the PCM solidifies, releasing its stored latent heat.
 
POINTS TO PONDER:
  1. Large number of PCMs are available in any required temperature range from −5 up to 190 oC.
  2. Within the human comfort range of 20° to 30°C, some PCMs are very effective.
  3. They store 5 to 14 times more heat per unit volume than conventional storage materials such as water, masonry or rock.
MAJOR TYPES OF PCMs:
1. Organic PCMs:
Paraffin (CnH2n+2) and fatty acids (CH3(CH2)2nCOOH)

2- Inorganic PCMs:
Salt hydrates (MnH2O)

3- Eutectics:
Organic-organic, organic-inorganic, inorganic-inorganic compounds

4- Hygroscopic materials
Many natural building materials are hygroscopic.

SELECTION CRITERIA:
While selecting a Phase Change Material, following characteristics should be kept in mind:

Thermodynamic properties
  1. Melting temperature in the desired operating temperature range
  2. High latent heat of fusion per unit volume
  3. High specific heat, high density and high thermal conductivity
  4. Small volume changes on phase transformation and small vapor pressure at operating temperatures to reduce the containment problem
  5. Congruent melting
Kinetic properties
  1. High nucleation rate to avoid supercooling of the liquid phase
  2. High rate of crystal growth, so that the system can meet demands of heat recovery from the storage system
  3. Chemical properties
  4. Chemical stability
  5. Complete reversible freeze/melt cycle
  6. No degradation after a large number of freeze/melt cycle
  7. Non-corrosiveness, non-toxic, non-flammable and non-explosive materials
Economic properties
  1. Low cost
  2. Availability
PCMs in TEXTILE CLOTHING:
These are smart fabrics. Put a warm hand on PCM fabric swatches and you can feel it for yourself, as the fabric actively draws the heat from your hand. Alternatively, put a cold hand on there and you’ll feel it begin to get warmer.

Phase change materials (PCM’s) can keep you cool when it’s hot and warm you up when you get too cold. Well, that’s to say they can is you select the right. They can be used alone or in combination with other technologies to create passive cooling systems,
 
SETBACK:
PCM’s have, unfortunately, previously been victims of their own hype: they promised a lot but early users were often disappointed with the performance level they actually delivered.

Since then, however, new application methods mean that it’s now possible to achieve significant and permanent heat regulation effects even under very demanding conditions.

WORKING IN CLOTHING:
  1. As we know PCMs are latent heat storage units, so the garments or apparel units made up of these are also HEAT STORAGE UNITS.
  2. When a PCM garment is facing rise in temperature due to external or internal conditions, its solid phase encapsulations starts absorbing heat energy under a constant temperature and change to liquid phase, thus providing cooling effect to the user.
  3. In case of freezing temperature or cold conditions, the liquid phase encapsulated apparel releases the stored energy under constant temperature, thus providing heat and soothing effect to the body.
SCHOLASTIC POINT OF VIEW:
1. Professor Doug Hittle, Ph. D of Colorado State University:

“As phase-change materials absorb body heat, they reduce the distractions of heat and cold fluctuations, providing a new superior level of comfort in clothing”

2. American Society for Testing and Materials (ASTM), is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services. To measure the dynamic thermal performance of fabrics containing phase-change materials, a new standard is being developed by ASTM Committee D13 on Textiles.

ADVANTAGES & USES IN CLOTHING:
1- Used In E- Textiles to provide auxillary system to the electronic components being installed by maintain temperature.
E-textile
2- Gloves (electronic or manual), for indoor and outdoor uses:
Electronic Gloves
3- Used in Fire Brigade and Army Uniforms.
Army Uniforms
.

Electrospinning of Nanofibers | Applications of Electrospun Nanofiber Products

Thursday, 27 June 2013


ELECTROSPINNING FOR NANO-FIBRES

Ashish Kumar Dua
M.Tech, Dept. of Textile Engineering,
Indian Institute of Technology (IIT), Delhi.
Email: ashisdua@gmail.com
Cell: +91-9560480711 




What is a nano-fiber?
  • A nano-fiber is a continuous fiber which has a diameter in the range of billionths of a meter.
  • The smallest nano-fibers made today are between 1.5 and 1.75 nanometers.
  • At the right a human hair (80,000 nanometers) is place on a mat of nano-fibers
Nanofibers
Nanofibers are a continuous filament much like a fishing line. The material produced from nanofibers forms mats of non-woven material on the collection plates or devices. Threads from garments are different in that they have been twisted into yarns and then woven into fabrics. Nanofibers are easily made from manmade polymers such as nylon and natural polymers such as proteins.

Unique Properties of Nano-fibers
  • Nano-fibers are very small which gives them unique physical and chemical properties and allows them to be used in very small places.
  • Nano-fibers have a huge surface area compared to their volume
  • Low basis weight
  • High porosity
High axial strength Scientist study both the chemical and physical properties of nanofibers. Because these fibers are so small, they are much more influenced by intra and intermolecular forces (things like electrical charge and magnetic fields). The huge surface area available on a nanofiber makes it very suitable for our new technologies which require smaller and smaller environments for chemical reactions to occur. Increasing the surface area speeds up a chemical reaction. Students may ask questions about how we see, and work in such a small environment. Much work is done using high speed cameras with enhanced light and magnification. Scientists also use SEM (scanning electron microscope) and TEM (transmission electron microscopes) to see surfaces of nanofibers and structure.

Surface-to-Volume Comparison:

Neglecting spaces between the smaller boxes, the volumes of the box on the left and the boxes on the right are the same but the surface area of the smaller boxes added together is much greater than the single box.

ABC blocks help students to understand the concept of surface to volume ratios. They need to see the additional surfaces.

Methods Producing the Nano-fibres:
Basically there are three methods:
When :
  • 1934 Formhals
  • In the last few years the work of several researchers have made the electrospinning process suitable for the solutions of wide variety of polymers, ceramics and composite materials to produce nano-fibres. 
Principle:
  1. Use of electrostatic and mechanical force to spin fibers from the tip of a fine spinneret.
  2. When the electrostatic Force overcomes the surface tension, a charged jet is ejected, which is then elongated in the electrostatic field. After a variety of jet destabilizations occurring simultaneously with solvent evaporation, the ultra-thinned jet is solidified and then deposited on the collector to form an overlaid nano-fibre mat.

Construction:
It consists of four major components:
  • High voltage power supply
  • Heating assembly (for melt- electrospinning)
  • Syringe and
  • Collector 
High voltage power supply
  1. DC(more feasible) or AC
  2. Very high voltage (usually in the range of 10 - 30 kV)
  3. The polarity of the electrospinning system is arbitrary and can be reversed depending upon the polymer type and final product  
Heating assembly
1. To melt the polymer to suitable viscosity, which can be electrospun easily.
2. Various sources such as:
  • Heating element
  • Heating gun
  • Laser heating
  • Ultrasound heating 
Syringe or capillary tube:
  1. Very fine capillary tube which holds the polymer melt into which a metal electrode is inserted
  2. It is mounted horizontally or vertically on an adjustable electrically insulating stand. A spinneret is connected to the syringe at one end for the production of nano-fibres
  3. A syringe pump is used to supply the polymer at a constant and controllable rate 
Collector:
  1. Used to collect the electrospun fibres
  2. The collector is mounted on an insulating stand so that its potential can be controlled
  3. The collector may also be in the form of a rotating and translating mandrel 
Process:
  1. Solution is prepared by dissolving the polymer in a suitable solvent in a particular weight ratio (typically about 15 to 20% polymer)
  2. The solution is loaded into a syringe and the syringe is placed on a syringe pump which pumps the solution at a fixed flow rate to a needle

  • Jet initiation
  • Jet thinning
  • Jet stabilization

  1. A high voltage is used to create an electrically charged jet of polymer solution or melt out of the syringe
  2. One electrode is placed into the spinning solution/melt and the other attached to the collector which is simply grounded
  3. The electric field is subjected to the end of the capillary tube that contains the solution fluid held by its surface tension
  4. This induces a charge on the surface of the liquid. Mutual charge repulsion and the contraction of the surface charges to the counter electrode cause a force directly opposite to the surface tension
  5. As the intensity of the electric field is increased, the hemispherical surface of the fluid at the tip of the capillary tube elongates to form a conical shape known as the Taylor cone
  6. Further increasing the electric field, a critical value is attained with which the repulsive electrostatic force overcomes the surface tension and the charged jet of the fluid is ejected from the tip of the Taylor cone
  7. The discharged polymer solution jet undergoes an instability and elongation process, which allows the jet to become very long and thin
  8. Solvent evaporates, leaving behind a charged polymer fiber or In the case of the melt the discharged jet solidifies when it travels in the air.

Important Features of Electrospinning:
  1. Suitable solvent should be available for dissolving the polymer.
  2. The vapor pressure of the solvent should be suitable so that it evaporates quickly enough for the fiber to maintain its integrity when it reaches the target but not too quickly to allow the fiber to harden before it reaches the nanometer range.
  3. The viscosity and surface tension of the solvent must neither be too large to prevent the jet from forming nor be too small to allow the polymer solution to drain freely from the pipette.
  4. The power supply should be adequate to overcome the viscosity and surface tension of the polymer solution to form and sustain the jet from the pipette.
  5. The gap between the pipette and grounded surface should not be too small to create sparks between the electrodes but should be large enough for the solvent to evaporate in time for the fibers to form.
Solution Conductivity:
  1. Higher the conductivity of the solution more charges on the surface and hence easier to stretch
  2. Polymers have less conductivity can be increased by the addition of the salts or electrolytes which produces ions and hence voltage required to produce smooth fibers reduces.
Solvents
Conductivity(mS/m)
Acetone
0.034
Butanol
0.0202
Distilled Water                                                             
0.447
Ethanol
0.0554
Methano
0.1207
Propanol
0.0385
Dimethylformamide
1.090

Taylor Cone:

Conic angle for electrospinning PAN/DMF solutions at different PAN concentrations (wt%) under a constant electric field of 80 kVm−1

Conic angle for PAN/DMF solutions (16 wt%) under varied electric field (needle inner diameter: 0.48 mm)

Types:
  1. Solution electrospinning and Melt-electrospinning
  2. In the melt-electrospinning as no solvent is used to dissolve the polymer, it is free from the problem of solvent recycling or removal
  3. The productivity is higher due to no loss of mass due to solvent evaporation in melt-electrospinning
  4. The polymers without appropriate solvents at room temperature such as polyethylene and polypropylene can be easily melt-electrospun
  5. Melt-electrospinning favours the production of multi-component systems such as blends and composites as in many cases no common solvent for all the components may be found
  6. The melt-electrospinning results the fibres, which are thicker than those produced from solution electrospinning  
Polymer-solvent used in solvent Electrospinning:
Polymer
  • Nylon 6 and nylon 66 
  • Polyacrylonitrile
  • PET
  • PVA
  • Polystyrene
  • Nylon-6-co-polyamide
  • Polybenzimidazole
  • Polyramide
  • Polyimides
Solvents
  • Formic Acid
  • Dimethyl formaldehyde
  • Trifluoroacetic acid
  • Water
  • DMF/Toluene
  • Formic acid
  • Dimethyl acetamide
  • Sulfuric acid
  • Phenol
Effect of Parameters:
1. Effect of solution concentration on fibre morphology:
  • Evaporation of solvent
  • Beads formation at lower cocentrtion

SEM micrographs of Nylon 6 electrospun fibre at a voltage of 15 kV, collector distance 8 cm for different polymer concentration (a) 15 wt.%, (b) 20 wt.% and (c) 25 wt.%

Physical properties of Nylon 6/formic acid at different concentration:

Nylon Conc.
(wt%)
Viscosity
    (pa.s)
Surface tension
(mN/m)
Electric conductivity
(S/cm)
Fibre Dia
(nm)
15
2.845
44.8
.0044
250-700
20
3.358
78.5
.00294
750-1200
25
4.856
53
.00116
750-1550
Formic acid
.0002
28
.09


2. Effect of applied electric field:
  • Higher electric field values are obtained either through decreasing the distance between the tip and collector or by applying higher voltages.
  • Increasing the electric field strength will increase the electrostatic repulsive force on the fluid results in more stretching hence slight reduction in diameter

Effect of voltage on morphology with 20 wt.% Nylon 6 polymer solution, tip to target distance 8 cm, a) 12 kV, b) 15 kV, c) 18 kV.

3. Effect of distance from tip to collector:
The wider gap allowed more time for the fluid jet to stretch and for the solvent to evaporate results in reduction of diameter.

Scanning electron microscopy (SEM) images of electrospun 20 wt.% Nylon 6 fibres obtained from formic acid solution at different collecting gap distance, (a) 5 cm, (b) 8 cm and (c) 11 cm and electric power 15 kV constantly.

4. Effect of flow rate:
At the low flow rate (about 0.20-0.25 ml/hr) the electrospun fibre is cylindrical and uniform. At higher flow rates (about 0.26- 0.300 ml/hr) the fibre surface is rougher

Scanning electron microscopy of elctrospun fibres (Nylon 6 solution from formic acid), a) 0.200 ml/hr, b) 0.2500 ml/hr, c) 0.2600 ml/h and the solution was 20 wt.% and electric field was 15 kV and tip to collector distance was 8 cm.

Applications of Electrospun Nanofibre Products:
1. Filtration:
Filter media is used to protect people and precision equipment from dust particles, smog, evaporate water, virus etc.

2. Medical application:
  • Electrospun biocompatible polymer nanofibres can be deposited as a thin porous film onto a hard tissue prosthetic device designed to be implanted into the human body. This coating film is expected to efficiently reduce the stiffness mismatch at the tissue interphase and hence prevent the device failure after the implantation
  • Nanofibre, spun from compounds naturally present in blood, can be used as bandages or sutures that ultimately dissolve into body. This nanofibre minimize infection rate, blood loss and is also absorbed by the body.
  • Artificial blood vessels, artificial organs, and medical facemasks.
  • Nanofiber nonwoven fabric for Soft-tissue biomedical applications