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.
Outgassing Voids
Meaning
Injection molding and extrusion processes can suffer from internal structural defects caused by the release of trapped gases as the polymer cools. The formation of outgassing voids happens when moisture, residual solvents, or volatile degradation products vaporize within the polymer melt and fail to escape before the material solidifies. This results in empty pockets or bubbles inside the finished plastic part.
Defect Mechanism
High melt temperatures accelerate the thermal breakdown of additives and polymers, releasing gaseous byproducts. These outgassing voids grow in size as the local pressure drops within the mold cavity during the cooling phase. This issue is exacerbated when processing hygroscopic polymers like nylon or polycarbonate that have not been adequately dried.
Process Control
Molders must maintain sufficient back pressure and pack pressure to force volatile gases to dissolve into the melt or escape through mold vents. Properly vented tooling helps prevent outgassing voids by providing a clear escape path for gases as the melt fronts advance. This mechanical solution is supported by running the extruder at lower shear rates.
Part Integrity
Internal bubbles weaken the mechanical properties of the molded part, reducing its impact resistance and tensile strength. This makes the component prone to premature failure under stress.