Enzymatic hydrolysis of polyamide and elastane for textile recycling
Résumé
Polyamide and elastane fibers blends are widely used in the daily clothing and very often closely combined . However, these synthetic fibers have different physico chemical properties that make them difficult to recycle and separate it. Polyamide fibers contain amino and carboxylic groups that can be cleaved with hydrolytic enzymes such as proteases and specific amidases [ 1]––[ 3]. However, the crystalline structure of polyamide makes enzymatic attack difficult. Hydrolytic degradation by using enzymes start on the surface towards amino groups which are present as end group chains. Thus hydrolytic enzymes can modify polyamide surface by releasing soluble oligomers [ 4]. Elastane fiber is a complex chemical structure which is composed of two segments, a soft segment containing polyols and a hard segment containing the urethanes groups, these two segments are linked by chain extenders of low molecular weight (diols or diamines). This fiber is difficult to degrade with microorganisms and there are still no studies showing a complete degradation with the use of enzymes. The results obtained showed that the two commercial proteases are specific to both polymers. As it is observed, hydrolysis is carried out on the surface of the materials. After 168h of reaction, the total amount of amines released is 18 mM eq. HMDA using Subtilisin in polyamide film. Subtilisin is specific also for elastane film which shows a total amount of amines released of 19 mM eq. HMDA. However, it is noticed that a part of the chemical structure of polyamide and elastane varies. It is observed that wild type enzymes produced from fungi sp. may be able to degrade the elastane surface very slowly. However, further studies is needed to hydrolyze polyamide.
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