Meaning
Physical, chemical and rheological characterisation suites establish the purity, structural integrity and processing behaviour of post-consumer or post-industrial recovered polymer fractions. Comprehensive recyclate testing measures contamination levels, moisture content, volatile organic emissions, melt flow consistency and mechanical property retention to certify scrap lots for commercial manufacturing. Procedures encompass spectroscopic scanning, differential scanning calorimetry, capillary rheometry, ash content quantification and mechanical tensile impact protocols.
Standard testing procedures stop applying when materials arrive as unsorted municipal municipal solid waste streams containing excessive organic non-polymer debris that invalidates standard laboratory test equipment.
Contamination Detection
Recovered plastics carry particulate, polymeric and chemical contaminants that jeopardize processing stability and part performance. Differential scanning calorimetry identifies trace cross-polymer contamination, picking out low-level polypropylene peaks hidden within high-density polyethylene bales or detecting polyamide fractions in recovered polyethylene terephthalate. Thermogravimetric analysis and muffle furnace ashing measure inorganic fillers, masterbatch pigments, glass fibres and abrasive dirt particles that score processing screws.
Infrared spectroscopy scans flake surfaces to detect non-polymeric adhesives, multi-layer barrier films and labels. Contamination levels dictate whether a scrap lot requires aggressive secondary wash cycles or diversion into low-specification applications.
Rheological Tracking
Variable melt behaviour creates major challenges when processing recycled resin lots through commercial injection moulding tools. Reprocessed polymers suffer chain scission, branching or crosslinking induced by prior thermal histories, shifting the melt flow index away from virgin polymer specifications. Multiple melt flow rate tests performed across single lots reveal lot heterogeneity and batch-to-batch inconsistency.
Capillary rheometry evaluates high-shear viscosity behaviour across typical gate shear rates, showing whether the recyclate will short-shot thin walls or cause excessive flash. Testing also tracks moisture levels, as trace water rapidly hydrolyzes engineering polymers such as polyesters and polycarbonates during melt processing, destroying mechanical properties.
Mechanical Verification
Structural parts moulded with post-consumer recyclate must satisfy strict safety and load-bearing performance requirements. Tensile, flexural and notched impact specimens run on mechanical test frames confirm whether the material exhibits embrittlement caused by oxidative ageing. Environmental stress crack resistance tests expose loaded specimens to surfactant solutions, identifying residual degradation that leads to sudden field cracking.
Odour testing and volatile organic compound measurements screen materials targeting automotive interiors and consumer goods packaging. Consistent data from test batteries enables processors to balance virgin-to-regrind blending ratios, adjusting mould packing pressures and cycle times to prevent warpage, sink marks and premature mechanical failure.
