Synthesis And Application Of Phosphazene Derivatives With Long Chain As Flame Retardant On PP And EVA

Polypropylene（PP） and ethylene-vinyl acetate（EVA） are widely used themoplastics with excellent properties. Nevertheless, the flammability limited their applications in many fields. It is necessary to modify them in order to meet the requirements. A widely known method to impart flame retardancy is to add halogenated flame retardants into the polymers. Halogenated flame retardants showed outstanding flame retardancy, However, they emit toxic gases and pollute the environment. Inorganic flame retardants are also widely used, but their high loading deteriorate the mechanical properties of materials. In this paper, we have prepared two phosphazene derivatives with long chain, and they were added into PP and EVA as flame retardant. Subsequently, the flame retardancy and mechanical properties were studied, then the thermal degradation properties of PP and EVA were investigated by using thermo-gravimetric analysis（TGA）, thermo-gravimetric analysis coupled with fourier transform infrared spectrometry（TG-FTIR）, thermo-gravimetric analysis coupled with mass spectrometry（TG-MS）. More details are as follows:Firstly, hex（dodecylamino） cyclotriphosphazene（HDCP） and hex（octylamino） cyclotriphosphazene（HOCP） were synthesized by nucleophilic substitution reaction, and characterized through fourier transform infrared spectrophotometry（FTIR）, nuclear magnectic resonance（NMR） and elements analysis（EA）; The automatic contact angle（ACA） and thermogravimetric analysis（TG） were also tested for the properties.Secondly, PP was modified by ammonium polyphosphate（APP）, pentaerythritol（PER） and phosphazene derivatives（HDCP, HOCP）. The flame retardancy were investigated by limiting oxygen index（LOI）, UL-94 test and cone calorimeter test（CCT）. The thermal degradation properties of flame-retarded PP were also investigated using TG-FTIR and TG-MS. The results showed that the LOI value of flame-retarded PP increased about 13 % when 2 wt% phosphazene derivatives were introduced. The degradation products of PP primarily included hydrocarbons and carbon dioxide. The adding of flame retardant can reduce the decomposition rate of PP and decrease the release combustible hydrocarbons.Thirdly, the flame-retarded EVA was prepared using phosphazene derivatives（HDCP, HOCP）, APP and Trimer. The combustion properties of flame-retarded EVA were evaluated using LOI, UL-94 test and CCT. The cone calorimeter data indicated that the flame-retarded EVA has the signidicant smoke-suppressing effect. The thermal degradation properties of flame-retarded EVA were also studied by TG-MS. The results showed that the flame retardant decreased T-5%（de?ned as the temperature at which 5 % of the initial weight has been lost）. The pyrolysis products of EVA were acetic acid, acetyl, hydrocarbons and other small molecules, and the main pyrolysis products were reduced by adding the flame retardants.Finally, EVA were modified by Mg（OH）₂ and phosphazene derivatives（HDCP, HOCP） to prepare the flame-retarded EVA. The flame retardancy were investigated by LOI and UL-94 test. The mechanical properties of EVA were studied by tensile test. The results showed that the adding of HDCP and HOCP greatly improved the mechanical properties of EVA composites, and the elongation at break was 700 % higher than that of EVA composites with Mg（OH）2.