Verifying Chain Scission and Crosslinking in Recycled Resins
Single-point melt flow certificates mask concurrent chain scission and crosslinking, requiring high-temperature GPC, low-shear rheology, and solvent extraction.
EN 13900-5
Meaning
Standardized European test protocol specifying the determination of pigment dispersion and colorant quality within thermoplastic matrices via the filter pressure value method defines EN 13900-5. The procedure measures the pressure rise generated upstream of a defined metal mesh filter pack when an extruded compound containing a specified concentration of pigment masterbatch passes through a laboratory extruder. It establishes the mechanical dispersibility of color concentrates and inorganic additives, stopping short of evaluating the final chemical stability or thermal degradation kinetics of the carrier polymer itself.
Testing Geometry
Controlled volumetric throughput is maintained by an isolated melt gear pump positioned between the single-screw laboratory extruder barrel and the filter pack housing. Standard qualification employs a dual-layer or triple-layer woven wire assembly, commonly terminating in a nominal screen aperture of fourteen micrometers. Molten polymer mixtures flow across the screen area under continuous pressure surveillance using upstream capillary transducers.
Any agglomerated pigment particles, unbroken mineral clusters or insoluble foreign contaminants larger than the mesh opening lodge permanently against the screen surface.
Pressure Differential
Insoluble agglomerate accumulation diminishes the functional open surface area of the screen disc, driving upstream pressure steadily upward throughout the test run. The filter pressure value is calculated by subtracting the baseline extrusion pressure of the pure carrier polymer from the maximum peak pressure registered during masterbatch introduction. Low pressure deltas, quantified in bar per gram of colorant, indicate clean dispersion with minimal agglomerates.
High pressure differentials signal clustered particles capable of tearing thin blown films or clogging spinneret orifices in synthetic yarn extrusion.
Commercial Impact
Sourcing agreements in technical injection moulding and agricultural film manufacturing mandate maximum permissible values to avoid continuous visual imperfections and brittle structural faults. Masterbatch processors tune twin-screw kneader configurations, screw residence time and dispersant additive chemistry to drive down this metric. Reclaiming post-industrial film scrap through compounding lines frequently elevates values due to unmolten gel inclusions or residual inorganic fillers.
Laboratory verification according to this method protects high-speed continuous processing machinery against disruptive off-spec resin lots.