Cross-sectoral recycling through the properties of the material to be recycled

Materials and Products

Recycled materials have different technical properties depending on the recycling batch, often different from the raw material. The quality of the recycled material passes through a series of analyses to create a knowledge of these properties and thus represent a starting point to direct them to the right recycling process.

Raw materials for the production of manufactured goods are provided with a technical data sheet indicating the characteristics of the material. These data are important in the “quality control” and production phases, as they provide useful information for an optimal process. During processing and the subsequent life cycle, some of this information may be lost as the raw material is processed and other materials are added. In addition, during use the products undergo maintenance processes which can degrade the material and consequently change its initial characteristics. This partial degradation process is also undergone during common recycling processes.

Consequently, the implementation of recycling processes must include both the identification and separation of end-of-life materials and the quality of the material. While the identification and separation of the material to be recycled is carried out by several processes, some of them automated, it is difficult to control the quality of the material, which by the very nature of recycling has a large margin of variability. Particularly with regard to fibres and thermoplastics, it would be necessary to analyse each batch if there is insufficient traceability information. This is the reason why recycling is usually carried out within the same sector, except in some particular cases where, for example, plastic bottles are recycled for the production of textiles. The latter case should be taken as an example to start establishing a cross-sectoral recycling that does not focus on reuse within the same sector, but investigates the properties of the secondary material in order to identify the most appropriate reuse sector for the characteristics of the recycled material.

The analysis of the characteristics of the recycled material passes through a series of instruments able to provide data related to the type of material such as temperatures (melting, softening, crystallisation, etc.) and physical-mechanical performance; first useful information for the processing of the material.

The characterisation of a synthetic polymeric material (thermoplastic) is carried out by means of infrared spectroscopic analysis, which is able to distinguish, through light interaction, the chemical bonds that make up the polymer. The temperatures characterising the material can be identified by means of calorimetric tests called differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA); these instruments provide useful information for the recycling of materials by thermal processes. Further evaluations must be made according to the physical-mechanical performance, which can provide us with indications on the resistance of the material to stresses such as bending, traction, bending, etc.

The characterisation of a material of natural origin, on the other hand, involves tests to study its morphology and reaction to chemical reagents.

The shape and size is examined using microscopes such as transmitted light, reflected light and scanning electron microscope (SEM), in longitudinal and cross-section.

The solubility of the material is verified with the use of solvents that solubilise the cellulosic material to determine the length of the polymer chain, thus verifying the degree of damage/wear.

The instruments and methodologies described above for an initial characterisation are instruments that Centrocot uses daily for qualitative-quantitative composition requests. In order to complete the “technical sheet” of the recycled products, Centrocot has provided itself with further instruments necessary to find an optimal recycling route and to direct the recycled material to the use that is permitted according to its properties. The equipment will be used as part of the activities of the new Multi-sector Laboratory developed at Malpensa Fiere.

 

For further information, please contact:

Dr. Daniele Piga, PhD

Multisectoral Research and Innovation

e-mail: daniele.piga@centrocot.it

Author: Daniele Piga

Multisectoral Research and Innovation Dept.