- Critical parameters of recycled PVC: why characterization determines industrial applicability
- Viscosity in recycled PVC: degradation, impurities and “interval” reading in extrusion
- Density and apparent density: indicators of charges, contamination and dosing repeatability
- Color in recycled PVC: thermal degradation, legacy additives and rapid quality control
- Stability of recycled PVC: process predictability, operating window and waste management
- Interpreting the correlations between viscosity, density, color and stability: the quality profile of recycled materials
- TGA thermal tests on recycled PVC: compositional fingerprint, volatiles and inorganic residue
- DSC in recycled PVC: Tg, residual plasticizers, heterogeneity and thermal history of the material
- Mechanical and rheological tests: tensile, impact and real workability of recycled PVC
- Classification of bales and ground materials: multidimensional criteria, variability and intended use
Viscosity, density, color, and stability: thermal tests, mechanical tests, and classification methods to qualify recycled PVC
Recycled PVC – Technical Manual - Chapter 6 – Quality Characterization of Recycled PVC
Critical parameters: viscosity, density, color, stability
Characterizing the quality of recycled PVC marks the moment when the secondary raw material ceases to be a vague collection of waste and becomes, in effect, an industrial material that can be assessed, compared, and targeted for specific applications. At this stage, we measure not only the "what," but also, and above all, the "how" the material will behave during processing and in the finished product. Critical parameters such as viscosity, density, color, and stability are not isolated quantities, but interconnected indicators that tell the technical history of the material and predict its future performance.
In recycled PVC, viscosity plays a central role because it summarizes, in a single parameter, the effects of thermal degradation, the presence of impurities, the distribution of additives, and the material's processing history. Unlike virgin PVC, where viscosity is closely linked to the degree of polymerization and controlled upstream by the resin manufacturer, in recycled PVC it is the result of a stratification of events. Every thermal cycle, every mechanical stress, every contamination contributes to modifying the material's response to flow.
From an industrial perspective, the viscosity of recycled PVC should not be interpreted as an absolute value, but rather as a behavioral range. Materials with nominally similar viscosities can react very differently during extrusion or molding, due to differences in molecular distribution or the presence of secondary components. For this reason, viscosity becomes a guiding parameter only when interpreted in relation to other quality indicators and the intended application context.
Density is another seemingly simple parameter, yet it's extremely important in characterizing recycled PVC. It provides indirect information about the material's composition, particularly the presence of fillers, impurities, and foreign components. In recycled PVC, even small variations in density can indicate significant differences in the formulation or purity of the flux. Unlike other polymers, PVC has a relatively high density, making the measurement particularly sensitive to polymeric or mineral contamination.
From an operational standpoint, the density of recycled PVC directly impacts logistical and process aspects.
The bulk density of the ground material or granules affects dosing, feed stability, and process repeatability. Non-uniform density within a single batch can lead to fluctuations in extruder or mold loading, with cascading effects on the quality of the finished product. Again, the numerical data is only meaningful when considered within a broader context of the material's behavior.Color is one of the most immediately perceptible parameters, yet also one of the most complex to interpret, in recycled PVC. Unlike virgin material, where the color is defined and controlled, in recycled material it is the result of a combination of original pigments, thermal degradation, contamination, and regeneration processes. Color is therefore not merely an aesthetic attribute, but an indicator of the material's condition...
