Secondary Amide Additives in Polyolefin Thermal Sealing Operations
Secondary amides eliminate seal jaw smoking and hot tack decay in polyolefin film sealing by maintaining low volatility at elevated operating temperatures.
ASTM D6579
Meaning
Analytical chromatography protocols for characterizing thermoplastic raw materials provide a standardized method to determine molecular weight averages and distributions. Adhering to astm d6579 allows laboratories to utilize size exclusion chromatography to evaluate polymer consistency before raw materials enter the injection molding machine. The procedure governs the identification of both the low and high molecular weight tails in a resin batch.
Measurement Protocol
Column calibration with narrow polystyrene standards establishes the baseline for resolving the molecular weight distribution. Under the guidelines of astm d6579, a soluble resin sample passes through a porous gel column that separates molecules by hydrodynamic volume. Organic solvents must be chosen and controlled to avoid polymer degradation or column interaction.
Rheological Impact
Variations in the molecular weight distribution directly alter the viscosity and elasticity of the polymer melt during extrusion or injection. Although two resin lots may share the same melt flow rate, subtle deviations measured by astm d6579 expose differences that cause parts to warp or flash. High molecular weight chains provide melt strength, whereas shorter chains act as internal lubricants during high shear flow.
Moulding Consequence
Processing issues such as irregular shrinkage, surface defects, and unstable melt pressure during the molding cycle often trace back to material shifts that only a chromatographic analysis can detect. By applying astm d6579 to incoming raw materials, a moulder can adjust process settings such as melt temperature or hold pressure to compensate for batch variations. Proactive chromatographic testing reduces scrap rates and avoids the costly downtime associated with adjusting tooling for unstable resin grades.