Meaning
Thermodynamic models measure the free energy of mixing when small solvent molecules or migrants interact with flexible polymer networks. The flory huggins theory calculates chemical potential changes and phase behavior in polymer-solvent systems through a lattice-based statistical framework. The formulation predicts additive solubility limits and swelling behavior in non-ideal polyolefin solutions.
Applicability declines when strong polar interactions or high polymer crystallinity cause structural departures from mean-field lattice assumptions.
Interaction Parameter
Interaction parameters quantify enthalpic contributions between polymer chains and low molecular weight migrants. Positive values indicate poor thermodynamic compatibility between the matrix and additive.
Lattice Formulation
Statistical thermodynamics assumes each polymer segment occupies a single lattice site equal in volume to a solvent molecule. Applying flory huggins theory enables converters to estimate migrant solubility limits inside polyolefin packaging films before physical compounding. High molecular weight polymers exhibit small combinatorial entropy gains upon mixing, rendering system stability heavily dependent on non-bonded interaction energetics.
Processing temperature increases alter interaction values, shifting the equilibrium between dissolved migrants and phase-separated surface blooms during storage.
Solubility Boundary
Thermodynamic predictions fail when orientation-induced crystallization reduces available volume within injection-moulded parts. Exceeding solubility limits forces excess additive out of the polymer matrix, producing surface hazing and weld line weaknesses.
