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Bad SolventGood SolventSolubility

(how much A dissolves in B?)

(how quick A moves inside B?)

Crystal line regions = impermeable

Permeation only through the amorphous regions!Permeability = Solubility X Diffusion

Permeability = Solubility X Diffusion

Solubility (how much of a substance dissolves in the plastic?)We must think about intermolecular forces / system temperature

Diffusion (how quick does a substance moves inside the plastic?) We must think about chain mobility (branching, MW, temperature, humidity) AND diffusing molecule mobility (size, shape, interactions with polymer)

Permeability = Solubility X DiffusionPolyolefins (PE, PP)

bad solvents for water, polar molecules, water based formulations

good solvents for most oils

Generally, expect high diffusivities for all molecules (LDPE > MDPE> HDPE ~ PP)

Permeability = Solubility X DiffusionBarrier Resins (PA, EVOH)

good solvents for water, polar molecules, water based formulations

bad solvents for oils

Generally, expect low diffusivities for all molecules in dry/ambient conditions (PA > EVOH)

Barrier Properties WVTR/OTRWVTR = Water Vapor Transmission Rate

Water Solubility

Water Diffusion

Water Permeability (WVTR)