Sustaining Recycled Polyester in Textile

Sustaining Recycled PET in Textile
Amirsuhel Aslam Desai Danwade
D.K.T.E’s Textile and Engineering Institute,
Ichalkaranji, India

As growing world textile market give prominence to synthetic fiber than natural fiber due to low cost and consistently same comfort as natural fiber. Synthetic fibers account for about 65 per cent of world production versus 35 per cent for natural fibers. Most synthetic fibers (approximately 70 per cent) are made from polyester, and the polyester most often used in textiles is polyethylene terephthalate (PET). Majority of the world’s PET production – about 60 per cent – is used to make fibers for textiles; about 30 per cent is used to make bottles. It’s estimated that it takes about 104 million barrels of oil for PET production each year – that’s 70 million barrels just to produce the virgin polyester used in fabrics. That means most polyester – 70 million barrels worth – is manufactured specifically to be made into fibers, not bottles, as many people think. Of the 30 per cent of PET used to make bottles, only a tiny fraction is recycled into fibers. But the idea of using recycled bottles – ‘diverting waste from landfills’ – and turning it into fibers has caught people’s attention.
Plastic Bottle waste
Fig: Plastic Bottle waste 
There are specifically two reasons that support sustainability quotient of recycled polyester (or rPET) Energy needed to make rPET is less than what was needed to make the virgin polyester in the first place, so we save energy. We are keeping bottles and other plastics out of the landfills so that clean environment can achieve.

rPET is divided into ‘post-consumer’ PET (post-consumer is one that comes from bottles) and ‘post-industrial’ rPET ( post-industrial might be the unused packaging in a manufacturing plant, or other byproducts of manufacturing).

The best option is the post-consumer PET, and that has driven up demand for used bottles. Indeed, the demand for used bottles, from which recycled polyester fiber is made, is now outstripping supply and cynical suppliers are now buying new, unused bottles directly from bottle producing companies to make polyester textile fiber that can be called recycled.

Production process :
There are two types of recycling – mechanical and chemical.

Mechanical:- Mechanical recycling is done by melting the plastic and re-extruding it to make yarns. However, this can only be done few times before the molecular structure breaks down and makes the yarn suitable only for the landfill where it may never biodegrade, may biodegrade very slowly, or may add harmful materials to the environment as it breaks down (such as antimony).

Chemical:- Chemical recycling means breaking the polymer into its molecular parts and reforming the molecule into a yarn of equal strength and beauty as the original. The technology to separate out the different chemical building blocks (called depolymerisation) so they can be reassembled (repolymerisation) is costly and almost nonexistent.

Most recycling is done mechanically because, Chemical recycling creates a new plastics which is of the same quality as the original but the process is expensive.

Dyeing process:
The base colour of the recycled polyester chips vary from white to creamy yellow, making colour consistency difficult to achieve, particularly for the pale shades. Some dyers find it hard to get a white, so they’re using chlorine-based bleaches to whiten the base. Inconsistency of dye uptake makes it difficult to get good batch-to-batch color consistency and this can lead to high levels of re-dyeing, another very high energy process. Re-dyeing contributes to high levels of water, energy and chemical use. Unsubstantiated reports claim that some recycled yarns take almost 30 per cent more dye to achieve the same depth of shade as equivalent virgin polyesters.

Uses of rPET fiber:
Many rPET fibers are used in constructions such as polar fleece, where the construction of the fabric hides slight yarn variations. For fabrics such as satins, there are concerns over streaks and stripes. Once the fibers are woven into fabrics, most fabrics are impossible to recycle because the fabrics almost always have a chemical backing, lamination or other finish, or they are blends of different synthetics.
Polar fleece fabric
Fig: Polar fleece fabric
As the growing market value of plastic as packing or container of beverages are increasing, environmental waste is also increases. So rPET fiber manufacturing can be reduce eco waste, provide good environment as well as give best recycled product in textile. 
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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