Isocyanate index deviation

The imbalance of the ratio between isocyanate and polyol causes abnormal performance. When this defect occurs in products of Process No. 2, it is usually related to a specific process parameter range or equipment status. If it persists, it will directly affect the product qualification rate and production cycle, increasing material loss and rework costs. Timely diagnosis and elimination is a basic requirement to ensure stable production.

1. Equipment factor: The NCO content in the isocyanate component fluctuates, the metering pump accuracy is insufficient, large viscosity differences between components cause metering deviation, and temperature changes cause density changes. 2. Mixing quality factor: In the RIM process, the mixing uniformity of the two components is the foundation of all quality; the Reynolds number of the mixing head, the impingement mixing energy, and the residence time distribution are the key engineering parameters that determine the mixing quality.

1. Process parameter optimization and adjustment: Regularly test the NCO content, calibrate the metering pump accuracy, keep the temperature control stable, and use mass flow meters for metering. 2. Systematic troubleshooting method: RIM problem troubleshooting follows the order of "formulation -> mixing -> temperature control -> equipment". First check the two-component ratio and catalyst dosage, then check the mixing head and self-cleaning function, next troubleshoot the raw material and mold temperature control, and finally check the accuracy of the metering pump and hydraulic system. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) assessments. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points.

This problem is a typical manifestation of isocyanate index deviation in the RIM process, and the core of the solution lies in ensuring the precise ratio and sufficient mixing of the two components, while controlling the reaction temperature and curing conditions within the optimal window. It is recommended to start troubleshooting from the mixing system and metering accuracy.