Post-Consumer Polyester Non-Aqueous Volatile Desorption Kinetics Baseline
Non-aqueous volatile desorption kinetics in post-consumer polyester depend on flake thickness, Arrhenius diffusion limits, and sweep gas partial pressures.
Tortuosity Factor
Meaning
Materials science describes the ratio of the actual winding path length that a diffusing molecule must travel through a matrix to the straight line distance across that matrix. In polymer membrane and packaging design, the tortuosity factor determines how effectively a polymer or composite material resists the penetration of gases like oxygen and moisture. This parameter directly affects the shelf life of packaged foods.
Diffusion Resistance
Introducing plate-like mineral fillers such as clay or graphene increases this path length by forcing gas molecules to navigate around the impermeable obstacles. A high tortuosity factor slows down the overall rate of gas permeation through the polymer film. This mechanism is critical for producing high barrier food packaging.
Processing Design
Extrusion conditions must be optimized to ensure that these filler platelets are aligned parallel to the film surface. When the platelets are disoriented, the tortuosity factor decreases, which reduces the barrier properties of the packaging material. This requires careful control of the blow up ratio and draw down speed during film blowing.
Barrier Limit
Structural defects or phase separation can create straight channels that bypass the winding paths. This limits the maximum loading of filler particles that can be incorporated before the barrier properties begin to degrade.