The Preparation And Properties Of POSS/DPP/UPR Flame-Retardant Composites

Unsaturated polyester resins are one of the most important thermoset materials that widely used in the 21st century due to their outstanding properties,including easily controllable of synthetic condition and fast curing processe at room temperature and low cost.Unsaturated polyester resins are mainly used in aerospace,electronic materials,biological materials,porous materials,chemical industry and equipment in daily life.However,the disadvantage of high flammability limits the wide spread applications of unsaturated polyester resins,so the research of improving the fire resistance of unsaturated polyester resins has abstracted lots of experts at home and abroad.The work is mainly focus on modifying the flame retardanceofunsaturatedpolyesterresinsbyusing[?6-Oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl?methyl]butanedioic acid?DDP?and Polyhedral oligomeric silsesquioxane?POSS?through the methods of physical blending and chemical synthesis.And the thermal stability and flame retardance properties of the modified unsaturated polyester resins were systematically studied.The main experimental content is as follows:?1?DDP and DodecaPhenyl-POSS were used as additives to blend with unsaturated polyester resins and then cured at the room temperature under the presence of the cobalt naphthenate and cyclohexanone peroxide.The modified unsaturated polyester resins with 10wt%,20wt%,30wt%of DDP or DodecaPhenyl-POSS were obtained.Thermo-gravimetric analyzer?TGA?,Oxygen index test?OI?and Vertical burning test were used respectively to measure the thermal stability and flame retardant performance.The results show that flame retardance performance and carbon residue rate of DDP/UPR and DodecaPhenyl-POSS/UPR are both improved,and the thermal stability has not changed much.Furthermore,DDP and DodecaPhenyl-POSS were both added into unsaturated polyester resins and when each content maintains at 10wt%,the OI value and vertical burning level are higher than that of 20wt%DDP/UPR and20wt%DP-POSS/UPR,indicating that the flame retardant performance get further improved.It means that there contains certain synergistic flame retardant effect between DDP and DodecaPhenyl-POSS.?2?DDP was used as raw material to participate into the polycondensation reaction of unsaturated polyester resins and then resins containing phosphorus on the polyester molecular chain were obtained.Unsaturated polyester resins that contain different content of phosphorus?0.8wt%,1.43wt%and 2.15wt%?were prepared by changing the mole ratio of DDP and adipic acid.Using Fourier Transform Infrared Spectroscopy?FTIR?and Nuclear Magnetic Resonance?NMR?as measurements to characterize the structure of the synthetic products.The results show that the characteristic peaks and chemical shifts of DDP appear in the IR and NMR spectra of modified UPR,suggesting DDP was connected to the molecular chain of unsaturated polyester resins successfully.The results of TGA show that the introduction of DDP into the molecular chain reduce the low temperature thermal stability and improve the high temperature thermal stability of unsaturated polyester resins,and the maximum decomposition temperature and carbon residue rate get further improved.Moreover,the OI value increases and the same as vertical burning level with the adding of DDP.These consequences mean that DDP improve the flame retardant properties of unsaturated polyester resins.The results of Differential Scanning Calorimetry?DSC?point out that DDP improves the maximum heat release temperature of UPR,meaning the addition of DDP leads to the delay of curing process in UPR.?3?PSS-?2,3-Propanediol?propoxy-Heptaisobutyl substituted?PSS-POSS?and DDP were regarded as reactants to added into the reaction of the unsaturated polyester resins,then the resins containing phosphorus and silicon on the polyester molecular chains were prepared.The DDP content remains at 9wt%,changing the content of PSS-POSS,then finally got a series of phosphorus-containing unsaturated polyester resins with different content of silicon.FTIR and NMR were used to characterize the structure of the synthetic product.The results show that the characteristic peaks of Si-O-Si and P-C appeared in the infrared spectra,and the characteristic chemical shift of DDP also appeared in the ³¹P NMR spectra of the products.These indicate that unsaturated polyester resins containing DDP and PSS-POSS on the molecular chain were successfully synthesized.The thermal stability of the modified unsaturated polyester resins were evaluated by TGA.The results point out the T₅ decrease with the addition PSS-POSS and the maximum decomposition temperature basically maintained at 390?.It means that PSS-POSS has little influence on the thermal stability of the phosphorous-containing unsaturated polyester resins,but the carbon residue rates at 650?are improved.The OI value and vertical burning level aslo increase,indicating that the PSS-POSS has certain improvement to the flame retardance properties of phosphorus-containing unsaturated polyester resins.Scanning Electron Microscope?SEM?was carried out to describe the surface morphology of the carbon residue that after vertical burning test.It can be seen that the carbon residue of the?phosphorous and silicon?-containing unsaturated polyester resins possess compact and continuous surface.This kind of surface has good barrier effect to oxygen and heat,protecting the underlying resins matrix during burning process.This is in agreement with the good flame-retardant performance in vertical burning test.