Determining Polymeric Fibre Moisture Regain Using Gravimetric Oven Drying Methods
Gravimetric oven drying determines accurate polymeric fibre regain by measuring dry mass after removing volatile moisture at specified temperatures.
PLA Thermal Degradation
Polymer Instability
Polylactic acid undergoes chain scission when exposed to elevated processing temperatures during melt extrusion or injection molding. This pla thermal degradation reduces the molecular weight of the resin and compromises the mechanical properties of final textile filaments or molded components. Exposure to moisture before heating accelerates hydrolysis, which fractures the polymer backbone further.
Molecular Breakdown
Heat energy initiates the cleavage of ester bonds within the long chains of the material. Increased shear force during screw rotation adds mechanical stress to these already fragile molecules. The resulting shorter chains exhibit lower viscosity and decreased melt strength.
Variations in this chemical breakdown cause inconsistency in fiber denier and tenacity during high speed spinning operations.
Quality Threshold
Manufacturers measure the onset of these changes by monitoring the torque output of the extruder and the drop in inherent viscosity of the pellets. A significant shift in these values indicates that the polymer has reached an irreversible state of damage. Operators adjust the temperature profile or the residence time to remain within the safe processing window for the grade in use.
Production Outcome
Excessive thermal history creates brittleness in finished garments and susceptibility to rapid aging under atmospheric conditions. Recycled streams often contain higher quantities of these shortened chains, necessitating the addition of virgin pellets or stabilizers to maintain structural integrity. The presence of residual monomers and oxidation products impairs the color fastness and physical durability of the textile product over its life cycle.