Meaning
Morphological restructuring mechanisms in semi-crystalline polymers increase lamellar crystal thickness during thermal annealing or slow cooling. Observing lamellar thickening reveals how chain-folded crystallites re-organize into thermodynamically stable states with higher melting temperatures. Initial crystal thickness depends on crystallization undercooling, yielding metastable structures during rapid mold quenching.
Post-molding heat treatment provides polymer chains thermal mobility to reduce fold surface free energy by extending stem lengths.
Thermal Mechanism
Annealing molded parts near their peak melting point mobilizes fold surface loops and adjacent amorphous chains. Polymer stems pull through existing crystal lattices, combining adjacent thin lamellae into thicker crystalline blocks. Long chain mobility determines the rate of lamellar growth, requiring longer exposure times for high molecular weight resins.
Heat treating temperature dictates the ultimate crystal thickness reachable before melting occurs.
Structural Morphology
Thicker crystalline lamellae raise the effective melting point of the polymer matrix according to Gibbs-Thomson thermodynamics. Amorphous phase fraction decreases as chain folds consolidate into ordered crystal structures. Tensile modulus and yield strength increase, while impact resistance drops due to reduced tie-molecule density.
Regrind inclusion disrupts chain packing regularities, retarding lamellar growth rates during post-processing annealing cycles.
Property Enhancement
Increasing crystalline stem length increases chemical resistance and dimensional stability under elevated service temperatures. Molded structural components undergo controlled annealing to eliminate internal stresses and maximize creep resistance. Optimization of lamellar dimensions ensures predictable performance in demanding mechanical applications.
