Determining Hydrolytic Degradation Thresholds in Virgin Resin Feedstocks
Hydrolytic degradation thresholds require drying virgin polyesters below 0.02 percent and polyamides below 0.10 percent water before melt processing.
Solution Viscosity
Meaning
Relative flow resistance describes the internal friction of a dissolved polymer chain moving through a solvent. Solution viscosity characterizes the molecular weight of a resin by measuring the time a dilute polymer mixture requires to pass through a calibrated capillary tube under gravitational force. High values signal longer molecular chains that increase the force needed to push molten plastic through a narrow gate.
Moulding Relationship
Process engineers monitor this property to predict how a resin will behave during injection into a mould cavity. Solution viscosity establishes the baseline for how much pressure the machine must apply to fill complex part geometries. Low readings indicate short chains that flow easily but may result in brittle parts with poor mechanical strength.
Excessive molecular length demands higher barrel temperatures to prevent short shots during production.
Data Discrepancy
Datasheet values represent virgin material tested under ideal laboratory conditions using specific solvent concentrations. Moulders frequently find that regrind or recycled lots exhibit lower metrics because shearing during initial processing breaks the polymer chains. Variations in the measured value across a run force constant adjustments to injection speed and holding pressure to maintain consistent dimensions.
Processing Consequence
Inconsistent values drive up scrap rates and prevent repeatable part weights in high volume automated cells. A drift in the molecular weight distribution changes the cooling behaviour of the plastic within the steel tool. Higher values increase the cycle time because the thicker material requires longer cooling intervals to reach structural stability.
Stability in the incoming resin quality remains the primary requirement for holding tight tolerances in precision moulded components.