How is milk fabric made?

Across the world, several gallons of milk are thrown away simply because it is sour or spoiled, surplus or too close to the date of consumption. Thus, this waste milk that is no longer fit for consumption becomes a source of fiber extraction due to the presence of casein protein for the textile industry. Milk fibers are bio-based that are processed with certain chemicals to formulate a textile substrate.

The step involved in the processing of milk fibers are as follows:

• The first step involves the collection of stale and waste milk from the dairy, milk processing factories and other sources. The liquid milk is then skimmed to remove fat which is carried out in an acidic medium and dehydrated that involves withdrawal or removal of water in order to obtain concentrated or dry milk. This process involves boiling to milk under reduced pressure and low temperature and the resultant is powdered milk.

• However, since milk fibers are protein-based, the dry milk powder further needs to be processed to extract the casein protein which forms the basis of the fiber. The extraction of casein is done by dissolving and filtering the milk powder. Thus, it is being quoted that thirty-five litres of skimmed milk consists of one kilogram of casein protein.

• After the casein protein is extracted it is made into fibers which can be accomplished using two methods.

• The first method is the conventional method (wet spinning) wherein the grinded powder of casein protein is dissolved in an alkaline solution of caustic soda (sodium hydroxide). The resultant solution is then ripped till the right viscosity is attained followed by filtration of the solution. This viscous solution is then extruded through a spinneret (sieve-like device having several holes at its base) in a water bath consisting of a non-volatile solvent (sulphuric acid) followed by solidification of fibers by coagulation. The fibers are then hardened by immersing the filament fibers into formaldehyde and followed by a drawing process wherein the fibers are stretched to impart strength. The fibers are then washed and dried and cut into staple length as per the end-use.

• The second method involves in which casein protein attaches as a side-chain or forms a branch of the acrylonitrile and this process is referred to as graft polymerization wherein the casein is grafted on the surface of acrylonitrile.

Apart from the two methods mentioned above, certain other initiatives have been taken to come up with milk fibers that are produced using eco-friendly methods, one of them is German-based Qmilk. Qmilk affirms that the casein fiber processed by them utilises 100% renewable resources with zero end waste and with the least carbon dioxide emission. The company further states that the spinning process is quite different with a minimal footprint. And adds that it requires about one hour and two litres of water to manufacture one kilogram of Qmilk fabric.

However, the Qmilk has not yet explained their process of manufacturing and the raw materials used and so there is not much information that confirms the sustainability of the milk fibers.