Rheological and Purity Test Selection for Post Consumer Resin Qualification
Pair high-shear capillary rheometry with DIN EN 13900-5 filtration and DSC enthalpy testing to qualify post-consumer resin before silo discharge.
Total Chlorine
Meaning
Aggregate concentration of chemically bound organic chlorine alongside inorganic chloride salts contained within a solid plastic material, regrind lot or chemical additive formulation defines this chemical metric. Sourcing operations quantify total chlorine to assess resin purity, verify compliance with halogen-free flame retardancy regulations and protect moulding machinery from acid gas corrosion. The measurement encompasses all elemental chlorine present regardless of whether it originates from polyvinyl chloride contaminants, residual polymerisation catalysts, chlorinated paraffin flame retardants or inorganic salt impurities.
The quantitative scope governs elemental content determination in raw polymer stocks and finished parts, but it does not specify the chemical reactivity, toxicological volatility or molecular release kinetics of individual chlorinated species.
Analytical Extraction
Quantitative evaluation requires standard analytical testing via oxidative combustion tube decomposition followed by ion chromatography or potentiometric titration. The testing protocol burns a prepared polymer sample in an oxygen-rich furnace at temperatures exceeding nine hundred degrees Celsius. High-temperature combustion converts all organically bound and inorganic chlorine species completely into gaseous hydrogen chloride and chlorine gas.
An aqueous absorbing solution collects these combustion gases, converting them into stable chloride ions for precise chromatographic measurement. Standard datasheets report the consolidated mass fraction value as parts per million or percentages by weight.
Degradation Threat
Processing polymers with high total chlorine contents introduces catastrophic corrosion risks to expensive injection moulding barrels, screw flights and tool steel surfaces. Under high processing temperatures, chlorinated compounds degrade thermally, releasing corrosive hydrochloric acid gas within the plasticising unit. This acidic off-gassing pits tool steel, attacks cavity venting pathways, strips physical chrome plating and ruins high-polish mould finishes.
Beyond tool damage, hydrochloric acid catalytic action accelerates base resin degradation, severing polymer chains and reducing the tensile properties of technical components.
Sourcing Governance
Circular economy mandates and electronic industry guidelines drive rigorous limits on allowable chlorine levels in post-consumer recycled feedstocks. Post-consumer polyolefin streams frequently contain trace polyvinyl chloride flakes, which elevate chlorine content beyond acceptable electronic grade specifications. Sourcing teams use chlorine testing to reject contaminated recycled resin lots before they enter production silos, avoiding compromised flame-retardant performance and defective part embrittlement.
Virgin polyolefins manufactured using modern high-yield Ziegler-Natta catalysts naturally maintain very low values, whereas recovered ocean plastics or unregulated industrial scrap display erratic levels that require exhaustive lot-by-lot verification.