Influence of a nitrogen-containing oil-based plasticizer on mechanical, thermal stability and fire performance of plasticized poly(vinyl chloride) and study of its mechanism of flame retardancy with Py–GC/MS

• An oil-based plasticizer with a triazine ring structure is prepared and exhibits flame inhibition in the gaseous phase.
• Proposed degradation and cross-linking processes of the nitrogen-containing plasticizer in PCV blends is proposed.
• The mechanism of flame retardancy was investigated by pyrolysis–gas chromatography–mass spectrometry (Py–GC/MS).
• An effective method to improve the flame retardant property of oil is proposed.

An epoxy oil-based plasticizer with a triazine ring structure (THEIC-ESBO) has been prepared using tris(2-hydroxyethyl) isocyanurate (THEIC) and soybean oil methyl ester as the main raw materials. The structure of THEIC-ESBO has been characterized by 1H NMR and 13C-NMR and elemental analysis. THEIC-ESBO substituting epoxy soybean oil (ESO) was used to plasticize PVC blends (PVC/THEIC-ESBO). when 60-70% ESO was substituted by THEIC-ESBO in PVC blends, the results of the mechanical properties and the dynamic thermomechanical analysis (DMA) indicate that plasticizing and compatibility of the plasticizer with PVC remained excellent, and the glass transition temperature (Tg) was 46.4 °C. The thermal stability of PVC blends was investigated by thermogravimetric analysis (TGA). The Fire performance of the PVC/THEIC-ESBO was investigated by the limiting oxygen index (LOI) and cone calorimeter test. When THEIC-ESBO was used as plasticizers alone, the LOI of the PVC blend reached 26.1%. The cone calorimetric data show that with increasing THEIC-ESBO, the time to ignition prolong, the value of the heat release rate (HRR) and the total heat release (THR) were reduced, the total smoke of release (TSR) was increased, both of the release rate of CO and CO2 were increased, but the value of CO/CO2 was decreased, the value of the residual char yield (C-Y) was significantly enhanced. All the data indicated that flame retardant of PVC blends using THEIC-ESBO substitute ESO was significantly improved, and THEIC-ESBO exhibits flame inhibition in the gaseous phase. The mechanism of flame retardancy of PVC/THEIC-ESBO was investigated by pyrolysis gas chromatographymass spectrometry (Py–GC/MS). The results indicate that nitrogen-containing compounds from THEIC-ESBO pyrolysis dilute the concentration of combustible gases, the cross-linking reaction is also promoted the char yield. SO, during PVC blends combustion process, the flame retardant of PVC/THEIC-ESBO was enhanced.

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