Preparation And Properties Of Phosphorus Flame Retardant/Polypropylene Composites

As one of the most widely used polyolefins,polypropylene(PP)materials have been widely used in many fields such as medicine,home appliances,food packaging,automotive and building materials.However,the limiting oxygen index(LOI)of PP is only 17-18%,so PP is a flammable material and can bring great safety hazards to people's lives and property and the toxic fumes are released during the combustion process,which restrict their further application.Therefore,it is of great significance to study the PP materials modified by flame retardant.In this paper,a polymerizable solid caged bicyclic phosphate esters flame retardant was designed and synthesized,which had the advantages of good heat stability,low heat release rate,convenient processing and so on.A new ternary synergistic composite flame retardant system for the flame retardant of PP system was obtained by the caged bicyclic phosphate esters(or its polymerization product)and the commercially available inorganic flame retardant ammonium polyphosphate(APP)and basic magnesium carbonate.The effect of the content of the component on the properties of the PP materials,and its synergistic flame retardant mechanism were studied in detail.In the second chapter,1-oxo-2.6.7-trioxa-l-phosphabicyclo[2.2.2]octance-4-acrylate(PEPAA)was synthesized by two-step method using pentaerythritol,phosphorus oxychloride and acryloyl chloride as raw materials.Its structure was characterized by infrared spectrometer(FT-IR)and 1H NMR.Its thermal properties and flame retardant properties were studied by thermogravimetric analyzer(TG)and micro calorimeter(MCC).The results showed that PEPAA had excellent thermal stability and flame retardant properties,and was suitable for processing flame retardancy of the PP materials.PEPAA was compounded with APP and basic magnesium carbonate for flame retardant PP to produce a new ternary synergistic composite flame retardant.Then the effect of PEPAA content on flame retardancy and the synergistic effect of organophosphorus flame retardants and inorganic nano-flame retardants were both explored.The PP composites were characterized by TG,scanning electron microscope(SEM),vertical burner(UL-94),limiting oxygen index(LOI)and cone calorimeter(CONE).The analysis results showed that the composite with PEPAA flame retardant had a LOI value of more than 27%,and was a flame retardant material.When PEPAA was 25wt%,its LOI value was 37.6%,UL-94 reached V-0 grade and comprehensive performance was the best.Moreover,the addition of PEPAA flame retardant could significantly reduce the heat release rate(HRR)and total heat of release(THR)of the composite,improved the melt dripping phenomenon of PP,and effectively reduced the flue gas release rate generated during PP combustion.The lowest total smoke release rate was only 3.5 m2,which was very important for greatly reducing the casualties caused by smoke asphyxiation in fire.In order to solve the problem that the small molecule phosphate esters flame retardant was unstable,easy to precipitate and poorly compatible with polymer materials.In the third chapter of this thesis,a polyphosphate esters flame retardant was developed.Firstly,the PEPAA monomer was polymerized in-situ polymerization with different proportions of basic magnesium carbonate and APP,and the optimal ratio was selected.Then a series of composite materials were prepared by blending the optimal in-situ polymerization product with PP.From Chapter 2,when the percentage of PEPAA flame retardant was 25%,the overall performance ratio was optimal.Therefore,the percentage of PEPAA or PPEPAA in this chapter was 25%,the effect of the ratio of basic magnesium carbonate and APP on the properties of PEPAA composites and PPEPAA composites was focused on and the difference in the effect of monomer PEPAA composite and polymer PPEPAA composite on PP performance was compared.The results showed that the mechanical properties losses of the composites prepared by in-situ polymerization products were smaller than those prepared by PEPAA monomer,and the compatibility between inorganic and polymer could be improved to some extent by used insitu polymerization products.When the content of phosphate esters flame retardant was 25 wt%,the ratio of APP/basic magnesium carbonate had a great influence on the flame retardancy performance of the composite prepared by monomer PEPAA,which the composite material obtained higher LOI value and better flame retardant effect with the increase of APP.However it had little effect on the flame retardancy of the composites prepared by in-situ polymerization products.