Fabric Knowledge

Is organic/recycled cotton really eco-friendly?(Everything here)

Organic cotton is trendy these days, a lot of customers are asking us about this kind of fabric. While they think this kind of fabric is sustainable, healthy and comfortable, we have different opinions, so we wrote this article. 

Also fashion brands such as H&M, Zara, C&A, ASDA have launched organic collections with their own green labels. It is the perfect time for fashion brands to aggressively promote sustainable collections.  Brands have given their products big names: C&A’s organic line is called “wear the change” , and Zara’s “join life”, and H&M’s “CONSCIOUS”. The key message of these brands is that organic fashion can be bought for a fraction of the cost. 

Does a beautiful new world of GREEN fashion really exist?

We must say the cotton fabric uses much more chemicals and produces much more pollution than synthetic fibre.

The birth of cotton fabric

Cotton is a very long-standing textile material in human history. Cotton itself is a natural fibre, but from the moment it is picked from the cotton tree, it will begin to experience a long journey of chemical baptise.

Sizing :

The cotton is picked as a form of cotton ball, which cannot be directly made into clothes, the first step is to comb the cotton balls into cotton fibres through a textile machine.

The problem is that cotton fibres are too thin and are very easy to break when they are pulled by the machine(the machine runs super fast). Therefore, it is necessary to apply a layer of slurry (modified starch slurry + PVA polyvinyl alcohol (used in glue stick) , CMC carboxymethyl cellulose, PA polyacrylate) on the yarn, The slurry give the yarn a protective film prevents breakage. Tightly wrapped the yarn, reducing friction between the hairness with the machine and improving yarn strength.

* After obtaining the yarn, the yarn will be weaved to raw cotton cloth, it will be sent to the printing and dyeing factory.

 

Every cotton fabric will experience four key stage below:

Pretreatment – Dyeing – Washing – Finishing treatment

 

Pretreatment

Sizing is beneficial for weaving, but detrimental when dyeing. When the fibre is tightly covered by a layer of film on the surface, the dye cannot enter the fibre, so the thread can not attach colours.

The factory uses boiling caustic soda (NaOH) to dissolve the slurry into a water-soluble sodium solvent, and add some penetrating agent JFC to help it dissolve better. This step is called desizing.

Everyone will thinks now it can be dyed after the slurry is removed, NO! It is far from enough. Cotton is naturally grown, so there will be a lot of impurities in it (there are more for organic/recycled cotton), including pectin, wax, cottonseed husk, inorganic salts, pigments, ash, nitrogenous substances and so on. This led to a non good looking raw fabric – not only yellow but also a lot of black cotton seed husks covered on the cloth.

raw-cotton-fabric

raw-cotton-fabric

Therefore, hydrogen peroxide (H2O2), an oxidant, was used to bleach the yellow pigments in the raw fabric. At the same time, to remove the black cotton seed husks, caustic soda (NaOH) and sodium bisulfite (NaHSO3) were added to react with the phenolic hydroxyl in the lignin to form easily soluble derivatives bases. This step is called refining bleaching.

* Just to calculate caustic soda (NaOH), there will need at least 2.5-3.7g used per 100g cotton fibre.

Hydrogen peroxide (H2O2) is very unstable. It is easily decomposed ineffectively by the metal ions of iron and copper in the solvent. So it will have no bleaching effect,  and causes holes on the fabric due to the reaction. In order to avoid this problems, it is necessary to add sodium silicate(Na2SiO3), EDTA, and sodium hexametaphosphate to desorb metal ions to prevent the occurrence of metal ion catalysis.

 

Dyeing

OK, so a lot of chemicals have already been used in pretreatment, now coming to the dying process.

The dye must be colourfast, able to hold the fibre firmly. There are three kinds of dye methods commonly used( cotton fibre): direct dyes, reactive dyes, and protected dyes. They combine with cotton fibres in different ways.

Direct dyes:  this is an old/low end way to dye cotton. Using this way you need to add a large amount of sodium sulphate(Na2SO4). The dye is NOT very firmly attached to the fibre(due to the limitations of this dying mechanism), and there are chemicals gas released which cause cancer. It is banned in Germany and many country in 1980s.  Nowadays,  it is very commonly used for kids crafty kit, tie dye kits etc.(as it is very simple to use).

 

Reactive dyes: the most common dye method, when dying they need to add sodium carbonate (Na2CO3) to adjust alkaline pH level, dispersant and a large amount of sodium sulphate(Na2SO4).

 

Protected dyes: the dye is not dissolvable, so there is no way to directly use them on cotton fibres.  It is necessary to add sodium hydrosulfite and formaldehyde hydrated sodium hydrogen sulfite, so it can be dissolved in solvent and dyed on the fibre. Then the fabric will expose to the air to re-oxidize the leuco sodium solvent to insoluble dye (by oxygen or hydrogen peroxide H202).

Since this dye does not dissolve under normal circumstances, it is very difficult to fade, most of the combat uniforms worn by soldiers use this kind of dye.

However, the sodium hydrosulfite used in the process is very smelly, and it can also decompose the toxic gas of sulphur dioxide (SO2). 

Washing

Due to the limitations of the dying mechanism, there are 30% dyes that will not  bound to the fibre. Which means these dye float on the surface of the fabric, people can’t use them directly ( cause skin reaction). A ‘soaping wash’ is needed now.

It is a must to use a large amount of surfactant compound to wash off this layer of floating colour, at the same time prevent the washed colour from re-sticking back to the cloth, so it is necessary to use a variety of different surfactants to rewash, rewash and rewash…

A lot of CLEAN WATER is used for cleaning, which leads to the fact that the dyeing industry is a highly polluting industry ( Large chemical emision to the water system).

After washing, an active fixative agent will be used again, which can react with the dye to reduce the solubility of the dye or directly cover a film onto the surface of the fibre, so that the dye is difficult to fall off. 

 

Finishing treatment

(This is the key point of differentiation of clothing products, also the most complicated/ changeable process, it is all about giving clothes a makeup.).

We always misunderstand:  the performance of the fabric = the performance of the fibre itself.

For example, pure cotton fabrics should absorb water, and chemical fibre fabrics should be airtight.But as long as there is special treatment, the impression of these two can be reversed.

How to achieve the differentiation between products, you must use different printing and dyeing auxiliaries.

For example, the iron-free shirts (used anti-wrinkle finishing agent, include poison chemical formaldehyde) , the water resistant shirt ( used fabric immersed in fluorocarbon polymer solution).

You probably often found that after a few washings, the fabric that was originally very soft will feel hard. You may complain the water quality is poor or the laundry detergent is not good.

In fact, the hand feel of clothes is destined to deteriorate with the number of washings, just because softener is used in it, and the softener will decrease with the number of washings.

Common softeners include cationic softeners and silicone oil softeners. Cationic surfactants are also the main components of hair conditioners. 

The silicone oil to improve softener is more effective.( more expensive).

Softeners are washable, they do not have a strong bond with the fibre, and can be washed off in water.Most products nowadays only have about 5 – 8 times wash life, and the softening effect has a cliff-like decline.

Of course there are ways to increase the wash resistance, that is to add a cross-linking agent, which the molecules stick to each other like glue. But the problem is there is a risk of formaldehyde exceeding the standard.

In fact, today’s fabrics have already become the same as fast food. Seemingly simple, but there are more than a dozen additives in it.

Dyeing auxiliaries are like food additives, which bring new performance and better comfort experience to clothes. While at the same time, there are also many hazards.

Some people may say what about the safety standards ( like OEKO-Tex 100)? You should know the test of clothing is much more difficult than the food test. For example, the formaldehyde content of clothing is generally measured as percentage of free formaldehyde in the solvent, but if there is formaldehyde still in the clothing, it will gradually dissipate with daily use.

There are more complicated things in the textile industry, sometimes even most practitioners do not understand it, so we try  to help you understand the big industry of clothing from a more professional perspective.

Thinking of a piece of cotton fabric that has been chemically baptised before handed to you, do you still think it is very natural and sustainable?  Thinking of the process above, do you think recycled cotton can be more sustainable?

Data: “In 2019/20,  Organic cotton accounted for less than 1% of the global cotton harvest that season” ( from cottonexchange.org)

Since there are only less than 1% of organic cotton producted globally. Where is so many organic cotton made cloth coming from?  

The most sustainable cloth is what you have now!

On the contrary, because of the high purity, synthetic fibre clothes are far more convenient to process than cotton, and use less chemical products and less waste water than cotton. 

Does this article change your mind? 

 

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