Synergistic Flame-retarded Effects Of Halogen-free Intumescent Flame-retarded Polypropylene

Halogen-free intumescent flame retardants(IFR) are mainly composed of phosphorus and nitrogen. IFR adding to Polypropyene(PP) may improve the material's flame retardancy performance, meanwhile suppress releasing of toxic substance and gas. Nowdays, Synergistic flame-retarded effects during the acid source, the carbon source and the gas scource of IFR system had been studied deeply, however, Synergistic flame-retarded effects between catalysis or charring synergistic agent and three sources were rarely studied. This paper made IFR/PP be the subject investigated, individual discussed Synergistic flame-retarded effects between different synergistic agent and single-component macromolecule IFR or multi-component mix-IFR.Single-component macromolecule IFR dimelamine salt of 3,9-bis(hydroxy)-2,4,8,10-tetraox-3,9-diphosphaspiro[5,5]undecane-3,9-dioxide(b-MAP) wassynthesized by fractional alkali liquor dropping in place of conventional technology. Highest yield (97.9% yield) occured when the dropping content of NaOH was 0.19mol (equivalent to a molar ratio of a b-MAP product :1.9 NaOH molecule). Furthermore, hydrolysis product of midbody spirocyclic pentaerythritol diphosphochloridate(SPDPC) reacted with melamine by single-side synthesis,then completed double-side synthesis. Dodecylbenzenesulphonic acid sodium(DSAS) etc surfactants were added into b-MAP, which could improve compound effect of IFR and PP. Ordered arrangement of disperse phase and continuous phase indicated the direction of heated materials intumescent, and interclude performance of intumescent char layer was enhanced in favour of improving composite's flame retardancy performance.Different kind and concentration of synergistic agents were added into multi-component mix-IFR. The sequence of synergistic catalytic flame-retarded effects(an increase in LOI of flame-retarded materials per unit mass of synergitic agent) is as follow: dextrine(DTR)>sodium molybdate(SMD)>cellulose methylate(CM)>ZnO>boracic acid(BA). Cellulose diacetate(CDA) is not effective flame-retarded synergistic agent of IFR. SEM obscerved that suitable synergistic agents might accelerate the esterification and charring progress of IFR system, and changed the microscopic structure of final char layer, which made char layer heap closely each other and minimize pores. Therefore, interclude performance of intumescent char layer was enhanced. The effect of these six types of synergistic agents on the ammonium polyphosphate(APP)'s crystalline phase growth and PP- crystallographic form were discussed. The results show that the APP's amorphous phase growth might prompt the esterification of heated materials, and increased the content of final char layer which protected materials from burning; meanwhile ,the concentration of PP- crystallographic form supplied the catalysis environment for synergistic agents exerting synergistic flame-retarded effects.CM, CDA, DTR, BA, SMD would partly decrease the mechanical performance of IFR/PP. When the concentration of ZnO is 2.0wt%, the tensile strength of IFR/PP would decrease from 23.60MPa to 18.00MPa. therefore, when ZnO is selected as the synergistic agent of IFR/PP, Avoiding the concentration of ZnO2.0wt% is necessary.