Synthesis And Application Of A Novel P-N Flame Retardant SPDC

Polypropylene(PP) is an important common plastic, which has good chemical stability and good electricity insulation and is widely used in the fields of automobile industry, electronic industry, communication equipments, medical instrument, chemical device and packaging products. However, pure polypropylene is highly flammable at room temperature and leaves almost no char. Flame retardants are usually required to be added to improve the fire retardancy of PP. Many flame retardants have been developed for PP in the last three decades. Traditionally, halogen-containing compounds with antimony trioxide as a synergistic agent are the main flame retardants of PP, but to consider the life safety and environmental problems, the use of some flame retardants have been limited because of the evolution of toxic gases and corrosive smoke during combustion.Now halogen-free compounds are regarded as promising flame retardants due to their environmentally friendly properties. Metallic hydroxides and oxides are kinds of flame retardant additives used in polypropylene, but the high loading seriously destroys the mechanical properties of polymeric materials.In recent years, intumescent flame retardant systems and flame retardant mechanisms have been developed rapidly, which is well known as a new generation of flame retardants in polypropylene and other polyolefins for some of their merits, such as very low smoke and toxic gases produced during burning, and antidripping property, which conform to the tendency of flame retardants'development. An intumescent flame retardant is generally made of three constituents:inorganic acid sources (e.g. ammonium polyphosphate, etc.), carbonifics (e.g. pentaerythritol, sorbitol, etc.) and spumifics (e.g. melamine, etc.). A typical and widely adopted IFR system is an ammonium polyphosphate (acid source)/pentaerythritol (carbonization agent)/melamine (blowing agent) (APP/PER/MA) mixture. However, traditional IFR additives have some shortcomings in flame retardancy of polyolefins, for instance, lower thermal stability compared with bromine-containing flame retardants. A novel flame retardant has been synthesized in this paper, and it can get good results in flame retardant PP, hoping to provide more useful information to the development of flame retardant PP.The intermediate product, SPDPC(3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane-3,9-Dioxide) is synthesized by pentaerythritol and phosphorus oxychloride. Then SPDPC and dicyandiamide at a ratio of 1:2 and 200 ml acetone were charged into a 250 ml round-bottom flask equipped with a magnetic stirrer, and slowly heated to 56.5℃, then refluxing about 8-10h, using triethylamine as acid-accepter and catalyst. After pumping filtration, washing and drying, a kind of white power is obtained, yield is about 90%. The analysis of FTIR,1HNMR,31PNMR and elements were done.Through the study of using SPDC as a single-component flame retardant in PP, the flammability and thermal behavior of PP-IFR were studied by the limited oxygen index (LOI), thermogravimetric analysis (TGA) and Cone Calorimeter test (CONE), in addition whose mechanical properties were investigated in this work. The results indicate that when the addition of SPDC comes to 30wt%, the material shows both excellent flame retardancy and anti-dripping abilities for PP, the LOI value of the PP-IFR(30%) achieves to 32.5 and passes the UL-94 V-0 rating test. Moreover, the heat release rate (HRR) and the total heat release (THR), production of CO (COP), smoke production rate (SPR) and total smoke production (TSP) and mass loss rate (MLR) of PP-IFR with30% SPDC decrease significantly relative to PP from cone calorimeter analysis. The morphological of char residues from decomposition of the PP-IFR(30%) was characterized by SEM micrograph, and it was found that the homogenous and compact intumescent char layer was formed. The TGA data show that SPDC can enhance the thermal stability of PP and effectively increase the char residue formation. The mechanical performance test showed that the effect of SPDC on PP systems was not obvious.In order to reduce costs, and cater to the concept of environmental protection. reduce the release of harmful components, the study of SPDC combining with APP to flame retardant PP is done. The results indicate that the compound intumescent flame retardant shows both excellent flame retardancy and anti-dripping abilities for PP when the two main components of IFR coexist at appropriate proportions, and the optimum flame retardant formulation is SPDC:APP= 3:1 that gives a LOI of 38.5 and UL-94 V-0 rating.As same to single-component flame retardant in PP, the HRR and COP, SPR and MLR of IFR-PP with the optimum formulation decrease significantly relative to pure PP from cone calorimeter analysis.The SEM micrograph also found that the good compatibility with PP and a homogenous and compact intumescent char layer was formed.