A Study On Application Of Microencapsulated Red Phosphorus Flame Retardant In Epdm Compounds And Their Foaming Products

Ethylene-propylene-diene terpolymer (EPDM) is one of the most used synthetic rubber with excellent heat aging resistance, moisture resistance, vapor resistance and electric insolate properties. EPDM has a wide range of applications such as low and medium voltage marine cable. However, EPDM is easy to burn, limited oxygen index (LOI) of pure EDPM is only 19%. EPDM need to add a large amount of flame retardants (mainly aluminum hydroxide Al(OH)3 and magnesium hydroxide Mg(OH)2) to improve its flame retardancy. But this will lead to the significantly decrease of the mechanical properties.As a kind of phosphorus based halogen free flame retardant, red phosphorus (RP) has good flame retardancy and the great advantage that it can improve the flame retardancy of the material significantly and no obvious influence on the mechanical properties when a little amount of RP was added. But in the actual application, RP has poor chemical instability (easy to auto ignition). In recent research, we found that microencapsulation is the best method to improve the poor chemical instability of RP. Microencapsulated red phosphorus (MRP) based in polyethylene (PE) and polypropylene (PP) has been reported, but as the flame retardant in EPDM is rarely.In this paper, we studied that the MRP, aluminum hydroxide and magnesium hydroxide were used in single or in combination as halogen free flame retardant in EPDM compound. The results of the UL94, LOI and mechanical properties testing showed the flame retardancy of MRP in EPDM compound was good and get the EDPM optimized formula which has the balance of the flame retardancy and the mechanical properties. The EDPM vulcanizate has good mechanical property and flame retardancy. When compounding ratio of EPDM/CaCO3/MRP/Mg(OH)2/Al(OH)3 was 100/80/10/90/90, LOI was 37%, the UL94 grade was V-0, tensile strength was 3.9 MPa, elongation at break is 225%. MRP with aluminum hydroxide and magnesium hydroxide showed the good synergetic effects of improve the flame retardancy (the LOI value).Base on the research results of MRP in EPDM compounds, MRP was also used in the foaming EPDM compounds. We studied that the addition of MRP, aluminum hydroxide and magnesium hydroxide has no significantly influence on the thermal decomposition temperature of foaming agent Azobisformamide (AC). In EPDM foaming product, the flame retardancy was mainly depended on the content of the flame retardants, not depended on the density.In this paper, MRP as a kind of halogen free flame retardant was used in EPDM and EPDM foaming products. We studied the effect of MRP on the flame retardancy and foaming characteristics of EPDM compound; providing the basic data which has highly practical value.