Analytical NIAS Screening Protocols for High Temperature Injection Molded Components
High temperature polymer NIAS screening requires combined GC MS and LC HRMS untargeted profiling to detect melt degradation products above ten ppb.
Thermal Oxidation Residues
Meaning
Degraded molecular byproducts formed when polymer melts react with atmospheric oxygen create solid deposits that cause cosmetic defects. Identifying thermal oxidation residues helps molders pinpoint areas in the injection molding press where polymer stagnation or overheating is occurring. These carbonized particles usually build up in dead spots of the manifold or around the screw tips.
This measurement guides preventive maintenance to maintain part aesthetic quality.
Degradation Compound
These deposits look like black specks or dark streaks in the final molded plastic part. When thermal oxidation residues form, the polymer chains have broken down into hard carbonaceous material that does not melt. This contaminant ruins the mechanical strength of the part, acting as a point of stress concentration.
Such defects lead to part failures under load.
Defect Prevention
To prevent this degradation, molders must maintain proper purging schedules and avoid leaving resin in a hot barrel during breaks. If the purge analysis shows high levels of thermal oxidation residues, the operator must lower the barrel temperature or reduce the residence time of the polymer. This intervention reduces scrap rates and prevents the blockage of hot runner gates.
It is essential for long-term automated molding operations.
Run Variable
Regrind resins contain more of these oxidised spots than virgin material due to their multiple heating cycles. Tracking thermal oxidation residues allows molders to set the maximum allowed regrind percentage for each production run. This control keeps the cosmetic defect rate low.