Shamsuzzaman Rasel1 & Joy Sarkar2
- Lecturer, Department of Textile Engineering, World University of Bangladesh (WUB)
- Assistant Professor, Department of Textile Engineering, Khulna University of Engineering & Technology (KUET), Khulna- 9203
Manufacturing process of Recycled polyester yarn from bottle
Recycled polyester yarn manufacturing is very easy and economical which are encouraging fabric manufacturers. Sorting and grading plastic bottles are chops and grinds into small bits that melt and soften plastics passes through a number of tiny holes which results in thin filaments. These filaments are using nowadays into both woven and knit industry to manufacture fabric.
- Collection of plastic bottles
- As generally plastic bottles are just used and thrown away which needs to be taken under a policy. By following Bring Schemes and/ or Deposit refunds schemes plastics bottle could collect. By bringing schemes known as kerbside collection results in low collection rates (overall 30 – 40% wastage) in the absence of public behavioral commitment. However, Deposit refunds schemes impose a direct economic incentive to mass participation. Further “on the go” or “office” collection may increase the recycling rate.
According to the report by World Economic Forum over 165 million tons of plastics contains in the ocean where about 8.8 million tons of bottles are throwing as garbage per year. This collection could use recycling as well .
- Sorting of plastic bottles according to grades
- Sorting of plastic bottles  is very important. Most of the plastic bottles are marked with number “1 to 8” inside of the triangular symbol along with PET below on it according to the quality, grades, color etc. collected bottles are sorted and separated from other materials such as PVC, HDPE, Polypropylene, drink cartoons, glass etc are taken to recycling centers known as MRF ( Materials recovery facilities). Post-consumer PET is often sorted into different color fractions; transparent or uncolored PET blue and green color PET and remainder into a mixed colors fraction.
Sorting is done in both automatically and manually where automatic methods separate plastics from glass, metals, and paper. Here, clear PET and unpigmented HDPE milk bottles also identified and separated out of the collected lot. By using the Fourier-Transform Near-Infrared (FT-NIR) spectroscopy and optical color recognition camera systems, materials can be categorized and sorted out. Sorting performance can be maximized by using techniques including X-ray detection.
After crushing post-consumer PET waste, it is converted into bales for companies and offers high prices for colorless/light blue than darker blue and green fractions.
- PET flakes production and washing
The sorted plastics are crushes, separate and dry by shredding the material into small fragments that contain residues of the original content, shredded paper labels, and plastic caps. As a result, pure PET fragments or PET flakes are produced. It is used as a raw material for polyester fabric making. According to the report by Rosenberger, a fabric made from recycled polyester requires 80% less energy and 90% less water than virgin polyester that made directly from oil. In washing plants, flakes are washed. According to a report, only 2-3m3 water per ton of material is requisites to clean the flakes. However, “Dry cleaning” technologies are using to clean the surfaces through frictions without using water.
- Drying process of PET flakes
- PET flakes are very sensitive to the hydrolytic situation during melting results in adverse mechanical properties; therefore, it requires a very low moisture level prior to extrusion. There are different drying processes of PET flakes are available after removing contaminations such as dehumidifying and infrared drying . Here moisture level is strictly maintained based on parts per million (ppm) contains on flakes to minimize hydrolysis.
After drying flakes are passed through electrostatic separator thus it could become free from metals from flakes. Then send to the production sector to produce final product fiber.
- Melt filtration and contaminants removal
- Removal of contaminants from polymer melts is done during extrusion in the melt filtration process. A “screen changer” machine is used to separate contaminants mechanically from melt where contaminants are stored on stainless steel, called a “Breaker Plate”. A large hole of steel drill allows the flow of polymer melt smoothly and heated, reheated and re-melted if necessary further [4, 5]
- Re-melted of flakes to convert yarn
In this section, PET bottle flakes are re-melted and passed through spinnerets, leaving them as filaments as like synthetic yarn produce from virgin raw material. A cooling system automatically cools the filament recycled polyester yarn. The length of the yarn depends on the requirements and is using to manufacturing fabric both in woven section and knit section. Therefore, CVC, PC etc. yarn also could possible to produce by mixing cotton fiber, called blending. By adding color during melting colored yarn is also possible to manufacture.
Dyeing, finishing, cutting, garment making process are the same as if virgin polyester is used .
- Quality of recycled yarn
The quality of the finished product depends on the grades of plastic bottles used and processing of raw material. Newer technology applications during manufacturing would be a great innovation in recycled bottle.
Flow chart of fabric manufacturing by using plastic bottles
- Shredding (left out of stored liquids into bottles)
- Sorting and separating clear plastics
- Treating with caustic soda to remove moving rivals from plastic which is harmful to the body
- Passing through a screw channel where temp.is 2700C (mixer); a long filament strand is produced here
- Mixed and blend of different types of strand passed through a heated chamber to make a bond between fiber together to a continuous strand
- Then taken to Aegis to produce materials (fiber) and baled and send to spinning
- Carding started (all line and similar direction together)
- Sliver form (spin on the bobbin)
- Send to knit or woven mills to produce fabricComparative properties of Virgin and Recycled plastics
There are obvious differences between recycled and virgin HDPE in the modification of bitumen in case of the rutting and fatigue cracking behavior. How much recycled polymer needs to add to the resins to achieve the same level of the properties of the virgin would be the best differences ever. Being on the added extra amount of the polymer defines the economic viability of the recycled materials . Other differences could determine as follows-
After discussing the properties of the virgin and recycled plastics it has become clear that recycled materials would be useful comparatively with virgin materials of being achieving the required properties.
The following information also signifies how we could save our existing energy after recycling the plastic bottles.
Global statistics for plastic bottle recycling
Day by day plastic bottle recycling amount increasing significantly due to sustainable issue throughout the world. According to the report, 480 million pounds of plastic bottles were collected in 1990 where it increases to 2900 million pounds in 2016. Among them, 5.9 million tons of flakes in 2009 3.4 million tons were used to fiber production . In Europe, 1.6 million tons of PET bottles were collected where 51% of them were used to produce flakes for fiber formation in 2011 and they must need to mandate the Waste Framework Directive by 2020 . Approximately 81% of the PET bottles sold in Switzerland were recycled in 2012. Main reason was the consequently increasing of fuel prices. According to the National Association report, 31.2% PET were recycling where a total of 1,798 million pounds was collected and recycled 475 million pounds over a total of 5764 million pounds of PET bottles .
Challenges, opportunities, and suggestions for industry
- A larger proportion of plastic waste stream can recycle if the post-consumer collection is set accurately.
- Product designs of the plastic makes from virgin materials must be potential that will assist in recycling effort further.
- Implementations of wider policies to environmental designs could have a larger impact on recycling performance.
- Plastic shopping bag can only be recycled from a range of 21 to 40% effectively
- Most of the time material handling is difficult because of the rigid packaging characteristics.
- The low weight to volume ratio of plastics collection and recycling is less economical.
- In sorting of plastic bottles must need high-performance machines to separate to high levels of purity.
- There is a possibility of making contamination of plastics to produce a wide range of quality of the products that is also considered as an environmentally sustainable.
- The performance of recycling is also important.
- The goals should be to maximize both the volume and quality of recycled resins.
It is assumed that there are approximately 165 million tons of plastics in the ocean which could be more the weight of fisheries by 2050. As there requires only some extra arrangement as a regular process could be much more effective to the environment. Only mixing the concept of plastic bottle melt filtration and fiber formation is required. By recycling, we could make a wide range of polyester fabric and at the same time, we could make a safer world.
- Hanaki: Urban Environmental Management and Technology, ISBN 9784431783978, p. 104
- Melt Filtration Options and Alternatives
- infohouse.p2ric.org/ref/14/13543.pdf PET Drying Best Practices
- Nicholas Dege: The Technology of bottled water, p. 431, John Wiley & Sons, 2011, ISBN 9781444393323
- A. V. Shenoy, D. R. Saini and V. M. Nadkarni, Estimation of the melt rheology of polymer waste from melt flow index, Polymer., Vol. 24, p. 722 (1983).
- A. V. Shenoy and D. R. Saini, Thermoplastic Melt Rheology and Processing, Marcel Dekker Inc., New York (1996).
- Nicholas Dege: The Technology of bottled water, p. 431, John Wiley & Sons, 2011, ISBN 9781444393323
- www.bafu.admin.ch/dokumentation/medieninformation/00962/index.html?lang=fr&msg-id=50084 (page visited on 4 November 2013).
- Japan streets ahead in global plastic recycling race Primary source is 『Plastic Waste Management Institute, Tokyo http://www.pwmi.or.jp/ei/index.htm』
- Guardian graphic, Euromonitor 2017
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Arvanitoyannis I., Bosnea L. 2001Recycling of polymeric materials used for food packaging: current status and perspectives. Food Rev. Int. 17, 291–346 (doi:10.1081/FRI-100104703)