Quantitative Validation of Non Aqueous Titration Kinetics for Acidic Volatiles in Recycled Polymers
Non-aqueous titration kinetics validate acidic volatile counts in recycled polymers, preventing extrusion screw corrosion and processing degradation.
Ester Hydrolysis Kinetics
Meaning
A chemical rate equation describes the speed at which polyester molecules break apart in the presence of water at elevated temperatures. Sourcing engineers study ester hydrolysis kinetics to predict the thermal degradation of materials like polyethylene terephthalate and polylactic acid during melt processing. This reaction involves the cleavage of ester linkages in the polymer backbone.
It is limited to condensation polymers processed under inadequate drying conditions.
Processing Risk
Moisture-driven chain scission reduces polymer molecular weight. The ester hydrolysis kinetics determine how quickly the resin loses its melt viscosity and mechanical toughness during extrusion or injection molding.
Defect Prevention
Preventing degradation requires drying the resin to moisture levels below a specific threshold before the material enters the heated barrel. Melt degradation under rapid ester hydrolysis kinetics produces shorter polymer chains, which leads to flashing at the parting line and brittle failure in the molded parts. Sourcing specifications for regrind polyesters must account for pre-existing hydrolytic damage.
Operational Control
Moulders control the degradation rate by monitoring drying temperatures and air dew points. The activation energy of the reaction means that every ten-degree increase in melt temperature can double the speed dictated by the ester hydrolysis kinetics. This rapid degradation becomes financially damaging when processing recycled PET, where moisture variation is high.
Processors must use desiccant dryers to suppress the reaction and maintain physical properties across long production runs. Severe hydrolytic degradation can reduce the impact strength of molded polyester parts by more than half.