Impact of N,N′-Methylene-bis-Morpholine on the Preservation of Natural Rubber Latex

Abstract

Natural rubber latex (NRL) preserved by high ammonia (HA) presents substantial pollution issues despite its good all-around properties. Cleaning preservation of NRL is critical in the modern rubber industry. In this study, NRL was preserved using N,N′-methylene-bis-morpholine (MBM), and the impact of MBM on the preservation and characteristics of NRL was investigated. The results showed that when the MBM dose was greater than 0.15 wt%, the volatile fatty acid value (VFA No.) and viscosity value of fresh NRL were lower, and it could be stored for longer than 5 days without losing stability. Furthermore, MBM demonstrated a favorable preservation effect on concentrated NRL (CNRL). To be effective, MBM must be administered at a dosage greater than 0.3 wt%. The mechanical stability test (MST) and VFA No. of the low-ammonia (LA)-CNRL prepared by MBM combined with ammonia were somewhat lower, whereas the viscosity value was greater. The research showed that the dose of lauric acid soap needs to be increased to improve the stability of ultra-LA-CNRL made by MBM–ammonia composite preservation. After pre-vulcanization treatment, the stability of LA-CNRL preserved by MBM–ammonia composite was drastically reduced. As the stabilizer dose was increased, the CNRL viscosity value decreased, whereas the MST and heat stability improved. The LA-CNRL vulcanized film has excellent mechanical properties similar to HA-CNRL. Furthermore, the infrared spectrum of the LA-CNRL raw rubber film was similar to that of the HA-CNRL film. The thermal degradation curve and characteristic temperature were also similar to that of the HA film. The study indicates that MBM has an outstanding preservation effect on fresh NRL and LA-CNRL, and the findings constitute a significant step forward in the development of the CNRL sector.