The general principle underlying the STRAP process (extraction and precipitation by targeting solvents) is:
- Selectively dissolve a single polymer in a multi-material composite in a solvent system in which the polymer is soluble, but the other components are not.
- The solubilized polymer is then separated from the composite by mechanical filtration and precipitated by changing the temperature and / or adding a co-solvent (an anti-solvent) that makes the dissolved polymer insoluble. The distilled solvent is reused in this process and the targeted polymer is recovered as a dry solid. This process can be repeated for each of the polymeric materials in the composite, resulting in a number of separate streams which can then be recycled.
Polyloop technology offers a STRAP process by batch “Batch STRAP”, targeting only PVC and its formulation components. The solvents which are used are reused in a closed loop.